Documents published in 2023 : Scipedia

A Discrete Element Analysis of the Mechanical Behaviour of an Electrode Active Layer
A. Lundkvist, P. Larsson, E. Olsson

particles2023.

Abstract
One of the main challenges in the development of lithium-ion batteries is mitigating the decrease in charge capacity over time. The loss of charge capacity in lithium-ion batteries stem from different phenomena, one of which is mechanical degradation. This study uses the discrete element method (DEM) to investigate the mechanical properties of a positive electrode layer. The goal is to link the local mechanical behaviour, on the particle scale, to the global behaviour of the electrode layer. Understanding the coupling between length scales is crucial for understanding and reducing the mechanical degradation and as the active particles, and the binder connecting it, form a granular structure in the electrode layer, DEM is a well-suited method to apply. The DEM model developed considered both interaction between active particles, as well as interaction between particles separated by binder. This study targeted to replicate the in-plane unloading stiffness of the electrode layer, which had been measured experimentally by Gupta et al. [1] through a U-shape bending test. The experiments measured the stiffness both in compression and in tension at various strain levels and load rates. The developed model was able to capture the constant stiffness in tension at different strain levels and the stiffness increase at higher compression levels markedly. The viscoelastic behaviour of the layer, with an increased stiffness at increased load rates, could be captured quantitatively by increasing the binder stiffness. This work lays an excellent foundation for further investigations of the mechanical properties of the active layer and its mechanical degradation mechanisms, such as viscoelasticity in the binder and swelling and fracture of the active particles.
Abstract
One of the main challenges in the development of lithium-ion batteries is mitigating the decrease in charge capacity over time. The loss of charge capacity in lithium-ion [...]
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Investigation of the draw down test method for the calibration of the DEM sliding friction and rolling friction parameters of a cohesionless bulk material
J. Marín, T. Comlekci, D. MacKenzie, Y. Gorash

particles2023.

Abstract
Discrete Element Method (DEM) is a numerical method that evaluates the interaction between particles and particle-boundaries [1]. The accuracy of the DEM simulations depends on several interaction parameters such as sliding friction and rolling friction coefficients. Most recent studies have shown that a draw down test can provide four criteria: angle of repose, shear angle, mass in the upper/lower box after test is done and mass flow rate that were used to calibrate bulk material sliding friction and rolling friction coefficients [2-3]. In general, these studies have used a fix aperture size of the upper box leading to a specific behaviour flow regime. In this study, three different flow regimes have been studied to evaluate if one set of unique parameters can reproduce the same response for these scenarios. A draw down test was carried out using gravel with particle size between 8-12.5 mm. The aperture size used were 50, 100 and 150 mm. During the test, the transient load was measured using a load cell in the upper box and pictures were taken after the test was done. DEM simulations were performed using the EDEM software where a single spherical and multi-sphere particle shape were used to obtain draw down calibration parameters by varying sliding friction and rolling friction parameters between 0.1 to 0.8 with an step of 0.1. When overlapping the four bulk criteria from 100 and 150 mm in aperture size using single sphere, it was possible to obtain a unique set of parameters. However, for 50 mm there was no overlapping which may indicate that using single sphere might not be accurate for all flow regimes. When using multi-sphere particle, the overlap led to a wide range of sliding friction coefficient for all cases, and although when overlapping the three scenarios there was no feasible region, it shows a tendency where a unique set of parameters might provide an approximate solution for all cases.
Abstract
Discrete Element Method (DEM) is a numerical method that evaluates the interaction between particles and particle-boundaries [1]. The accuracy of the DEM simulations depends [...]
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Particle-Level Experiments of Non-Dilative Interfaces: Accurate Input Parameters for Numerical Simulations
L. Kandpal, P. Vangla

particles2023.

Abstract
The development of more accurate force prediction models developed through particle-level experiments is required to accurately model non-dilative interfaces from micro to macro. Further, selecting reliable input parameters for DEM remains a challenge. Thus, micromechanical experimental studies are of fundamental importance that can provide insights into microscale aspects for in-depth knowledge of non-dilative interfaces. This study presents custom-designed, reliable, and sensitive equipment that facilitates shear tests for non-dilative interfaces under different configurations that simulate suitable conditions for geotechnical applications. This research offers a logical rationale for the non-dilative interface system's observed shear behavior.
Abstract
The development of more accurate force prediction models developed through particle-level experiments is required to accurately model non-dilative interfaces from micro to [...]
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Development and Validation of a High Order Finite Element CFD-DEM Solver
T. Geitani, S. Golshan, B. Blais

particles2023.

Abstract
Currently existing computational fluid dynamics-discrete element method (CFD-DEM) solvers suffer from computationally expensive coupling between the CFD and DEM as it requires calculating at each fluid time-step the void fraction and the solid-fluid forces such as drag, lift, buoyancy, and undisturbed flow forces. We develop a unified finite element CFD-DEM solver which integrates the CFD and DEM solvers into a single software resulting in faster and cheaper coupling. Our fluid formulation is stabilized using tailored techniques to prevent oscillations in regions of sharp gradients, to enhance the robustness of the formulation and local mass conservation, and to relax the Ladyzhenskaya-Babuska-Brezzi inf-sup condition. The developed solver supports high order finite elements resulting in better accuracy with larger cell sizes. Moreover, our solver supports dynamic load balance parallelization for both the particles and the fluid. This evens the distribution of workloads among processors, resulting in better efficiency and resource exploitation. Additionally, we develop a new spatially and temporally continuous analytical void fraction scheme called Quadrature-Centered Method (QCM). This scheme results in less computational time, better accuracy and convergence, and enhanced mass conservation. It also enables the use of very small CFD time-steps thus achieving better temporal accuracy and the use of mesh sizes smaller than those commonly used in CFD-DEM (< 3 times the particle diameter.) We validate our solver through several cases among which we will discuss a spouted bed test case where particle velocities matched those of the experiments, a particle sedimentation test case where we study the effect of the void fraction scheme choice on the particle’s terminal velocity, and a particle Rayleigh-Taylor Instability where the particles constituted the heavy phase and where we study the evolution of the mixing layer with time.
Abstract
Currently existing computational fluid dynamics-discrete element method (CFD-DEM) solvers suffer from computationally expensive coupling between the CFD and DEM as it requires [...]
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Assessing the Impact of Relative Motion on Hydrodynamic Force Interactions between Particles Pair
L. Barbeau, B. Blais, C. Béguin, S. Éthienne

particles2023.

Abstract
The hydrodynamic interactions between particles have significant effects in many engineering fields, such as fluidized beds and slurry sedimentation. This is because they can impact the macroscopic process parameters of these systems (e.g., particles' cluster sedimentation speed) [1-2]. To better understand the hydrodynamic interaction between particles and its effects on macroscopic process parameters, it is necessary to understand the hydrodynamic force interactions between individual particles as a function of their relative position and velocity. The first step in this direction is the interaction between a pair of particles, which remains an active area of research. It is established that drag and lift forces applied on a particle change in function of its relative position and velocity to another particle. However, the impact of these changes on their dynamics is limited. We first study the effects of the relative position between the particles and the Reynolds number on the drag and lift forces applied to them to constitute a pairwise fluid force model. This force model is the basis for a new reduced-order particle dynamics model that also includes lubrication, Basset, and added mass forces. We compare the results obtained for a series of sedimentation cases with the reduced-order model with those obtained from a resolved computational fluid dynamic solver coupled with a discrete element method (CFD-DEM) [3]. Comparing the fluid forces obtained between these to the model enables us to assess the impact of the particles' relative motion on the hydrodynamic forces applied to them (e.g., drag, lift, and forces). These sedimentation cases also allow us to evaluate the effects of the density ratio between the particle and the fluid on the virtual mass force and its impact on the dynamic of the particles. This study is a stepping stone toward a complete model for hydrodynamic forces in particle clusters.
Abstract
The hydrodynamic interactions between particles have significant effects in many engineering fields, such as fluidized beds and slurry sedimentation. This is because they [...]
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DEM and CFD-DEM: From established technology to new frontiers
C. Kloss, A. Mayrhofer, M. Niemann, A. Aigner, P. Seil, M. Kwakkel, C. Govina

particles2023.

Abstract
Discrete Element Method (DEM) and DEM coupled to Computational Fluid Dynamics (CFD-DEM) are established techniques for optimization and design of particle processes. Its applicability to a wide range of processes has been proven for many different industrial and environmental applications. The extension to new fields and processes has been made possible by continuous improvements of: (i) models, (ii) numerical methods and (iii) computational performance. DEM and CFD-DEM have evolved from pure “particle modelling tools” to numerical tools to model “particulate flow””. Combining the Lagrangian nature of discretization with complex interaction models, the behaviour of viscous pastes, compressible powders, melting polymers just to name a few, has become feasible. Additionally much attention has been given to improvement of numerical aspects, which led to improved stability and therefore applicability of the models. Last but not least, the computational efficiency and possibility to make use of available computational resources has boosted the technology to new levels. The authors give their perspective on some corner-stones and highlights in modelling and development that were made in the past few years, which lead to this break-through and give some concrete examples of current state of the art modelling capability. Based on this solid foundation that has been build, new goals are within reach and the authors will give some insight on future opportunities for this modelling technology.
Abstract
Discrete Element Method (DEM) and DEM coupled to Computational Fluid Dynamics (CFD-DEM) are established techniques for optimization and design of particle processes. Its applicability [...]
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Learning Physics-consistent Particle Interactions
Z. Han, O. Fink, D. Kammer

particles2023.

Abstract
Interacting particle systems are ubiquitous in nature and engineering. Access to the governing particle interaction law is of fundamental importance for a complete understanding of such systems. However, it is particularly challenging to extract this information from experimental observations due to the intricate configuration complexities involved. Machine learning methods have the potential to learn the behavior of interacting particle systems by combining experiments with data analysis methods. However, most existing algorithms focus on learning the kinetics at the particle level and do not learn the pairwise interactions specifically. Moreover, in reality, interacting particle systems are often heterogeneous, where multiple interaction types coexist simultaneously and relational inference is required. An approach that can simultaneously reveal the hidden pairwise interaction types and infer the unknown heterogeneous governing interactions constitutes a necessary advancement for our understanding of particle systems. However, this task is considerably more challenging than its homogeneous counterpart. Here, we propose the physics-induced graph network for particle interaction (PIG'N'PI) allowing to precisely infer the pairwise interactions that are consistent with underlying physical laws by only being trained to predict the particle acceleration for homogeneous systems. We further propose a novel method for relational inference which combines probabilistic inference and PIG'N'PI to learn different kinds of interactions for heterogeneous systems. We test the proposed methodologies on multiple benchmark datasets and demonstrate that the learnt interactions are consistent with the underlying physics and the proposed relational inference method achieves superior performance in correctly inferring interaction types. In addition, the proposed model is data-efficient and generalizable to large systems when trained on small systems, contrary to previously proposed solutions. The developed methodology constitutes a key element for the discovery of the fundamental laws that determine macroscopic mechanical properties of particle systems.
Abstract
Interacting particle systems are ubiquitous in nature and engineering. Access to the governing particle interaction law is of fundamental importance for a complete understanding [...]
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DEM Study Investigating the Effect of Particle Shape on Compaction of Realistic Non-Spherical Particles Using Convolutional Neural Network
K. Giannis

particles2023.

Abstract
This study focused on investigating the deformation behavior of non-spherical particles under high-load compaction, utilizing the multi-contact discrete element method (MC-DEM). To account for the non-spherical shape of the particles, two methods were employed: the bonded multi-sphere method (BMS) and the conventional multi-sphere (CMS). The BMS approach yielded accurate results in predicting the compression behavior of a single rubber sphere, while the CMS method failed to replicate the same behavior. Building on these findings, the BMS method was utilized to study the uniaxial compaction of Avicel® PH 200, a popular choice of excipient due to its ability to enhance the stability, flowability, and compressibility of tablet formulations. The results obtained from this study showed very good agreement with experimental data. To generate realistic 3D models of particles, a novel approach was introduced, which combines 2D projections and deep learning algorithms utilizing a 3D convolutional neural network (3D-CNN) methodology. Surrogate model was used to overcome the computational cost of DEM simulations. The findings of this study offer a valuable tool for researchers and engineers to efficiently and accurately generate 3D models of particles, leading to new insights and innovations in a range of applications such as rock and mineral analysis, battery materials, pharmaceuticals, and space exploration.
Abstract
This study focused on investigating the deformation behavior of non-spherical particles under high-load compaction, utilizing the multi-contact discrete element method (MC-DEM). [...]
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Particle-based Modeling of Metal Powder Additive Manufacturing
M. Liu

particles2023.
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Adaptive Data-Driven Modeling of Complex Systems
J. Andrade

particles2023.
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Finite strain elastoplastic and solid-solid contact problems with the Smoothed Particle Hydrodynamics
D. Morikawa, M. Asai

particles2023.

Abstract
The Smoothed Particle Hydrodynamics (SPH) is a numerical scheme in which the domain is discretized into Lagrangian particles in the context of continuum mechanics. It has been widely used for fluid dynamics problems, and recently it has also been applied to solid mechanics with reasonable success. In this work, we present a total Lagrangian SPH (TL-SPH) for the application of solid mechanics and contact problems. Total Langrangian stands for the usage of the reference configuration to calculate the spatial derivatives. As a consequence, all particles maintain a perfect distribution, which, in turns, results in highly accurate calculations. In this way, the method is able to eliminate any problem related to tensile instability, which is one of the main shortcomings of SPH. Here, we introduce a simple, yet robust, way to include finite strain elastoplasticity into the TL-SPH method based on the logarithmic strain. Then, the elastic part can be easily defined with the Hencky elastic model, and the plastic part with any yield criteria such as Drucker-Prager. In addition, we develop a contact algorithm capable of simulating solid-solid contact problems. In this way, the simulation of different objects becomes a mix of continuous and discontinuous problems. Finally, we show the applicability of the method with several simple tests to validate the accuracy of the TL-SPH for simulating the elastoplastic solid material, as well as for contact problems including direct impact and friction effects. REFERENCES [1] Morikawa D.S. Toward robust landslide simulations from initiation to post-failure using the Smoothed Particle Hydrodynamics. Kyushu University PhD thesis (2022).
Abstract
The Smoothed Particle Hydrodynamics (SPH) is a numerical scheme in which the domain is discretized into Lagrangian particles in the context of continuum mechanics. It has [...]
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Discrete element method for combination of continuous and partical problems
R. Varga

particles2023.

Abstract
The Discrete Element Method (DEM) is a numerical approach that deals with the motion and interactions of individual elements. This method is mainly used in particle mechanics because it is overshadowed by other techniques such as the finite element method (FEM) when dealing with continuous problems. For this reason, it is not commonly known among structural engineers. However, its use can be found in cases that combine particle and continuum mechanics problems, such as crack propagation in reinforced concrete members. Calculating and optimizing these types of problems using FEM is challenging due to frequent mesh changes or the requirement for difficult-to-detect parameters in standard practice. This post discusses the possibility of using the DEM method with an extension of the beam-bound model (BBM). In this method, a beam element is inserted between the bounded discrete elements to transfer all types of forces and moments. The problem of this method is to define the correct cross-sectional and material characteristics of the individual beam members. In study, we focus on the determination of these parameters and the verification of this method on model examples of reinforced concrete elements such as simply supported and fixed beams.
Abstract
The Discrete Element Method (DEM) is a numerical approach that deals with the motion and interactions of individual elements. This method is mainly used in particle mechanics [...]
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Parametric Physics-Informed Neural Networks for Material Model Calibration from Full-Field Displacement Data
D. Anton, H. Wessels

particles2023.

Abstract
The identification of material parameters occurring in material models is essential for structural health monitoring. Due to chemical and physical processes, building structures and materials age during their service life. This, in turn, leads to a deterioration in both the reliability and quality of the structures. The material parameters indicate possible damage and material degradation, as they directly reflect the resistance of the structure to external impacts. We further developed physics-informed neural networks (PINNs) [1] for the calibration of the linear-elastic material model from full-field displacement data and global force data in a realistic regime [2]. For a realistic data regime, the optimization problem had to be conditioned. The advantage of this method is a straightforward inclusion of observation data. Unlike grid-based methods, such as the least square finite element method approach, no computational grid and no interpolation of the data are required. However, directly solving inverse problems using PINNs is computationally expensive and prone to realistic noise levels in the measurement data. Moreover, the PINN must be trained completely from scratch for each new full-field displacement measurement, even if the geometry and material of the structure remain unchanged. In our ongoing work, we are therefore focusing on learning parameterized solutions of parametric partial differential equations using PINNs, such as [3]. We further investigate the ability of parametric PINNs to act as a surrogate for the identification of material parameters from full-field displacement data. By learning parameterized solutions, the PINN does not need to be completely re-trained for each full-field displacement measurement. The calibration of the material model can thus be drastically accelerated, and information about the material condition can be provided near real-time. Furthermore, we also plan to apply the parametric PINN to more complex material models, such as those for hyper-elastic and elasto-plastic materials.
Abstract
The identification of material parameters occurring in material models is essential for structural health monitoring. Due to chemical and physical processes, building structures [...]
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DEM-BPM modelling of coated particles to investigate their crash absorbing behaviour
W. Safdar, S. Heinrich, A. Düster

particles2023.

Abstract
The collision of ships remains a significant cause of accidents, resulting in severe environmental consequences such as oil spillage from oil tankers. Enhancing the crashworthiness of ship structural design is crucial, and one approach being explored is the filling of the double hull structure with granular material [1]. Coating these particles with environmentally friendly materials can optimize their ability to absorb kinetic energy and transfer loads from the outer to the inner hull [2]. However, the mechanical behavior of the coated particles depends on the type of coating material, posing challenges in developing numerical simulation models. To address this, an open-source Discrete Element Method (DEM) code called MUSEN [3] is utilized to numerically model the behavior of coated particles. Furthermore, MUSEN can be extended using the Bonded Particle Method (BPM) to simulate particle breakage through solid bridges. However, the inclusion of coating material in the model increases the number of parameters, as well as computational time and cost. This requires a robust methodology to characterize the mechanical behaviour regardless of the type of coating material with reduced computational cost, keeping in mind the actual application inside the ship double hull. Sensitivity analyses and parametric studies are conducted to understand the effect of input parameters and identify the influential ones. Subsequently, algorithms such as the Particle Swarm Algorithm are employed for parameter optimization. Finally, models of different fidelity are used to compare the results from multi particle compression tests. The findings from these simulations will be presented in this contribution
Abstract
The collision of ships remains a significant cause of accidents, resulting in severe environmental consequences such as oil spillage from oil tankers. Enhancing the crashworthiness [...]
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A Novel Parallelisation Scheme for DEM on Distributed Memory Computers
E. Staercke, C. Nougiuer-Lehon, F. Frolio

particles2023.

Abstract
Several strategies have been proposed for high performance computing with DEM. Yet, quite few works have been published on this topic (e.g., [1-3]), compared to the extensive use of DE simulations as a modelling tool in research and industry. This is however not surprising, since granular media at the grain scale appear as highly evolutive and disordered systems, which makes effective parallelisation a challenging task. We present an approach which exploits an inherent limitation of DE simulations, as the opportunity for an efficient and flexible parallel implementation on distributed memory computers. Namely, the “numerical sound speed” set by the representative particle diameter and the time step defines an upper bound for the celerity at which perturbations can propagate across the discrete medium. We show how this numerical artefact (of negligible importance for most applications) can be turned into an original criterion of spatial domain decomposition, which leads to a DEM-suited parallelisation scheme. We present our approach through its actual implementation into the DEM’ocritus code [4,5]. We analyse its performance through benchmarks and parametric analyses of biaxial tests, on assemblies of up to 15 million circular particles.
Abstract
Several strategies have been proposed for high performance computing with DEM. Yet, quite few works have been published on this topic (e.g., [1-3]), compared to the extensive [...]
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Modeling and Simulation of Soil and Soil-Tool Interaction for Industrial Applications
M. Harutyunyan, S. Emmerich, S. Steidel, M. Burger, K. Jareteg, J. Quist

particles2023.

Abstract
Modeling of soil-tool interaction for industrial applications involves the coupling of soil models, mostly based on the Discrete Element Method (DEM), with multibody systems, representing construction machinery such as excavators or wheel loaders. To obtain accurate predictions of reaction forces on tools like wheel loader buckets, it is essential to have an appropriate parametrization procedure, which makes use of data obtained from laboratory tests such as the triaxial compression test or direct shear test for different types of soil. Simulations with suitable DEM-softwares can then be validated against the experimental data to assess the applicability and performance of the numerical methods [2, 3] The DEM software GRAnular Physics Engine (GRAPE) developed at Fraunhofer ITWM in Germany has been successfully used to simulate compression and shear tests and has been proven to yield good predictions of the soil-tool interaction and draft forces [4] for spherical particles such as coarse sand. A year-long collaboration with the Fraunhofer-Chalmers Centre (FCC) in Sweden has successfully resulted in the development of a soil simulation toolbox for FCC’s general purpose DEM solver Demify® incorporating and enhancing the simulation techniques used in GRAPE [1]. Co-simulation is enabled through an FMI interface coupling Demify® with multibody systems modeled e.g., in Simulink to evaluate relevant variables such as forces at critical linkage joints of the construction machines. To model real-life application scenarios, the entire workflow must be considered, from the soil parametrization process, to setting the particulate soil model and performing numerical simulations for the specific problem, to the final post-processing to analyze the load data. We will characterize and discuss the different steps of the workflow and present simulation results obtained with the toolbox Demify® for Heavy Machinery.
Abstract
Modeling of soil-tool interaction for industrial applications involves the coupling of soil models, mostly based on the Discrete Element Method (DEM), with multibody systems, [...]
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Continuum Granular Flow Modeling and Beyond: Exploiting Meshless Methods
K. Kamrin

particles2023.
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Particle-based fiber models of woven materials for earth entry thermal protection
A. Santos, L. Abbot, J. Haskins

particles2023.

Abstract
Applications requiring materials with layer-to-layer strength, from basketry to thermal protection systems, use interlaced, three-dimensional woven materials. NASA is developing and deploying woven material heat shields for missions, including Artemis I (3D-MAT for compression pads) and potentially Mars Sample Return - Earth Entry System. These materials are complex, hierarchical and must protect from extreme environments and phenomena, such as deformation, impact and high-enthalpy heating. Woven material performance depends on microstructure, damage and weave geometry. Therefore, fiber-specific models are needed to simulate fiber contacts within the weave hierarchical geometry (fiber to tow to yarn to weave) and the inherent directionality of fibers. Explicit fiber models can simulate how weave microstructure evolution affects thermal and mechanical properties. We parameterize a discrete element bonded particle models (DEM-BPM) of fibers to capture thermal and mechanical behavior within and between fibers, with bonded and contact forces, respectively. We study the proportion of heat transfer and stress via the contact network, fiber bonds and the weave geometry, for example, with respect to yarn warp-weft identity (whether it interlaces weave layers). Our results demonstrate the importance of explicit fiber modeling for connecting microstructure with thermal and mechanical properties.
Abstract
Applications requiring materials with layer-to-layer strength, from basketry to thermal protection systems, use interlaced, three-dimensional woven materials. NASA is developing [...]
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Blockchain in health sciences: Research trends in Scopus
C. Araujo-Inastrilla, A. Vitón-Castillo

The Iberoamerican Journal of Science Measurement and Communication (2023). The Iberoamerican Journal of Science Measurement and Communication

Abstract
Objective. The scientific production indexed in Scopus on Blockchain in health sciences was characterized from 2012 to 2021. Design/Methodology/Approach. A bibliometric study of the scientific production related to Blockchain technology in health sciences was carried out andindexed in Scopus from 2012 to 2021. Bibliometric indicators of productivity, impact, and collaboration were used. The SciVal, VOSviewer, and Microsoft Excel tools were used to process and present the information. Results/Discussion. Between 2012 and 2021, 1,543 articles were published on the subject studied, with an average of 14.9 citations per publication. Scientific production increased until 2021, as did the number of authors. International collaboration fluctuated. The most frequent terms related to Blockchain were the Internet of things, smart contracts, and cryptography. India, China, and the United States led the collaborations, and authors of Asian origin predominated. Conclusions. The scientific production of Blockchain in health has grown due to its transformative potential in health systems, with an interest in the security and traceability of medical data.
Abstract
Objective. The scientific production indexed in Scopus on Blockchain in health sciences was characterized from 2012 to 2021. Design/Methodology/Approach. A bibliometric study [...]
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EVENTOS ADVERSOS DE MEDICAMENTOS EN COLOMBIA, CUALES SON LAS CAUSAS Y POSIBLES SOLUCIONES
J. Giraldo

Juan Nicolás Giraldo's personal collection (2023). 1

Abstract
This article presents a consolidated quarterly analysis of adverse events associated with medications in Colombia, compiled through the online platform designed for reporting these incidents. The primary focus of the report centers on segmentation by departments, providing a detailed overview of the incidence of adverse events in different regions of the country. The study reveals significant patterns in the geographical distribution of adverse events, highlighting substantial variations between departments. Variables such as gender, quantity of events, possible causes, and specific factors are identified, showing a higher prevalence of adverse events in certain areas, providing valuable information for decision-making in public health and the implementation of preventive strategies. Furthermore, the report emphasizes the importance of strengthening the notification and monitoring of adverse events at the local level, underscoring the need for greater awareness and engagement from healthcare professionals in different regions. Recommendations are proposed to enhance the quality of reports and encourage closer collaboration between departments, with the goal of improving patient safety and optimizing the management of adverse events associated with medications in the Colombian context.
Abstract
This article presents a consolidated quarterly analysis of adverse events associated with medications in Colombia, compiled through the online platform designed for reporting [...]
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GPUs Based Material Point Method for Compressible Flows
P. Baioni, T. Benacchio, L. Capone, C. de Falco

particles2023.

Abstract
Particle-In-Cell (PIC) methods such as the Material Point Method (MPM) can be cast in formulations suitable to the requirements of data locality and fine-grained parallelism of modern hardware accelerators such as Graphics Processing Units (GPUs). While continuum mechanics simulations have already shown the capabilities of MPM on a wide range of phenomena, the use of the method in compressible gas dynamics is less frequent. This contribution aims to show the potential of a GPU-based MPM parallel implementation for compressible fluid dynamics, as well as to assess the reliability of this approach in reproducing supersonic gas flows against solid obstacles. The results in the paper represent a stepping stone towards a highly parallel, Multi-GPU, MPM-base solver for M ach > 1 Fluid-Structure Interaction problems.
Abstract
Particle-In-Cell (PIC) methods such as the Material Point Method (MPM) can be cast in formulations suitable to the requirements of data locality and fine-grained parallelism [...]
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Computational Error Estimation for the Material Point Method in 1D and 2D
M. Berzins

particles2023.

Abstract
The Material Point Method (MPM) is widely used for challenging applications in engineering, and animation but lags behind some other methods in terms of error analysis and computable error estimates. The complexity and nonlinearity of the equations solved by the method and its reliance both on a mesh and on moving particles makes error estimation challenging. Some preliminary error analysis of a simple MPM method has shown the global error to be first order in space and time for a widely-used variant of the Material Point Method. The overall time dependent nature of MPM also complicates matters as both space and time errors and their evolution must be considered thus leading to the use of explicit error transport equations. The preliminary use of an error estimator based on this transport approach has yielded promising results in the 1D case. One other source of error in MPM is the grid-crossing error that can be problematic for large deformations leading to large errors that are identified by the error estimator used. The extension of the error estimation approach to two space higher dimensions is considered and together with additional algorithmic and theoretical results, shown to give promising results in preliminary computational experiments.
Abstract
The Material Point Method (MPM) is widely used for challenging applications in engineering, and animation but lags behind some other methods in terms of error analysis and [...]
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Determining Coke Moisture Content Through Images Analysis Methods and Machine Learning Models
M. Li

particles2023.

Abstract
Coke moisture content plays a crucial role as a quality indicator in ironmaking. Fast and accurate measurement of coke moisture content can effectively ensure operational stability, thereby guaranteeing the quality of pig iron. Coke with different moisture levels exhibits variations in light reflection, refraction, and powder adhesion characteristics. Drawing from this premise, we employed an image analysis approach to analyse the colour and texture features of coke images with varying moisture content. The results indicated that certain specific image features are highly sensitive to changes in coke moisture content. This study also conducted testing and comparison of performances of three common machine learning models in predicting coke moisture content based on image analysis. The Support Vector Machine (SVM) predictive model for coke moisture content based on image analysis showed optimal performance. This demonstrated a close connection between coke image features and moisture content.
Abstract
Coke moisture content plays a crucial role as a quality indicator in ironmaking. Fast and accurate measurement of coke moisture content can effectively ensure operational [...]
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Simulating industrial scenarios: with the open-source software MercuryDPM
A. Thornton, Q. Nguyen, H. Polman, J. Bisschop, R. Weinhart-Mejia, M. Vesal, T. Weinhart, M. Post, I. Ostanin

particles2023.

Abstract
Creating predictive computer simulations, i.e. virtual prototypes, of complex granular industrial processes has many challenges. In this paper we review recent advances in creating such virtual prototypes. We introduce the open-source code MercuryDPM [1], which is often applied to complex industrial applications via the spin-off company MercuryLab. We briefly discuss how to import complex industrial geometries and how to deal with large numbers of particles and wide size-distributions. Then we focus on how to create a computer representation of an actual granular material, the so-called model calibration. For calibration, we start by reviewing what parameters need to be measured and what experimental characterisation machines are available. We present an industrially practical calibration method, where certain parameters are directly measured and others are indirectly calibrated, using a variety of machine-learning techniques, implemented in the open-source codes GrainLearning [2], TensorFlow [3] and scikit-learn [4]. With GrainLearning, one can find local optima in only two to three iterations, even for complex contact models with many microscopic parameters. On the other hand, TensorFlow and scikit-learn use two popular supervised learning algorithms, Neural Network (NN) and Random Forest (RF) regression, respectivly. After a training period consisting of hundreds of particle simulations, NN and RF are capable of providing a mapping between the micro-parameters and the bulk behaviour, which can be used to find the optimal micro-parameters that correspond to the experimentally observed behaviour.
Abstract
Creating predictive computer simulations, i.e. virtual prototypes, of complex granular industrial processes has many challenges. In this paper we review recent advances in [...]
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Advancing Dynamic Process Modeling of Comminution and Classification Circuits: A Paradigm Shift with GPU-Enabled DEM Solver
J. Quist, E. Edelvik

particles2023.

Abstract
The minerals processing and aggregate industry have relied on steady-state population and mass balance simulators for decades. However, accurately modeling new processes remains a critical challenge that hinders innovation and decision-making in the industry. In recent years, time-dynamic simulators have been developed, which offer more accurate predictions of process variability and performance, as well as the ability to introduce regulators and control algorithms. Yet, these still require simplified process models of each unit in the system. The development of high-performance discrete element method (DEM) solvers with advanced particle physics models presents a new opportunity to model complete comminution and classification processes. In this paper, we discuss the potential, challenges, and current limitations of using DEM for advanced dynamic process and equipment evaluation, exemplified by a coarse comminution crushing and screening case. We demonstrate the methodology using a GPU polyhedral DEM implementation with a boundary-volume hierarchy (BVH) collision search algorithm. The results show that the scale of a full-scale two-stage crushing process is possible to simulate. The transition from algebraic process models to DEM would make a significant advancement, bridging the current gap between overly simplified generalized process models and specific equipment design. This approach offers exciting opportunities for the mineral processing and aggregate industry to develop more innovative and efficient circuits.
Abstract
The minerals processing and aggregate industry have relied on steady-state population and mass balance simulators for decades. However, accurately modeling new processes remains [...]
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Physical Process-Based Entrainment Behaviour Modelling of Diluted Debris Flow Using SPH Incorporated with HBP-DP Approach
Y. Ma, M. Asai, G. Chen, Z. Han

particles2023.

Abstract
Debris flows overriding steep valleys can cause a significant decrease in bed friction resistance due to undrained excess pore water pressure, leading to an exponential increase in both destructiveness and volume. This study develops a two-phase numerical model based on Smoothed Particle Hydrodynamics to simulate the progressive entrainment behavior of debris flow accurately. The fluid and bed-sediment materials are modeled using the non-Newtonian Bingham-type Herschel-Bulkley-Papanastasiou (HBP) constitutive model. The mass erosion behavior of debris flow is achieved and augmented by incorporating the Drucker-Prager (DP) softening model, which accounts for variations in the pore water pressure ratio across different saturation states. A straightforward phase-change approach is implemented according to the mutation of effective viscosity to prevent any minute displacements of viscoplastic materials when subjected to steep inclinations. The multi-phase model has been compared with the large scale flume experiments conducted by the United States Geological Survey. The 3-D numerical results obtained from the rigid bed, dry and wet erodible bed exhibit a good agreement with the experimental data, encompassing flow momentum feedback and erosion patterns. This paper initially attempts to simulate the entrainment of multiple phases in a steep valley by incorporating viscoplastic flow.
Abstract
Debris flows overriding steep valleys can cause a significant decrease in bed friction resistance due to undrained excess pore water pressure, leading to an exponential increase [...]
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Bottom Boundary-Fitted Free Surface Flow Simulation with Coordinate Transformation Using SPH(2)
S. Fujioka, N. Mitsune, K. Tsuji, M. Asai

particles2023.

Abstract
Particle methods such as the SPH and MPS methods have problems because it is difficult to treat curved bottom surfaces such as seabed surfaces accurately. In this study, regarding this problem, the curved bottom surfaces’ treatments have been improved using a coordinate transformation using the high-order second derivative model called SPH(2). Although the theory for the coordinate transformation was established in the MPS method, its accuracy did not give the desired accuracy because of the numerical errors of the second derivative models. Therefore, the numerical errors in these coordinate transformations were overcome by applying the second derivative model of SPH(2) to the coordinate transformation formulas. The superiority and validity of the proposed coordinate transformation using SPH(2) are demonstrated through validation examples such as the hydrostatic pressure and dam-break problems.
Abstract
Particle methods such as the SPH and MPS methods have problems because it is difficult to treat curved bottom surfaces such as seabed surfaces accurately. In this study, regarding [...]
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Partitioned Coupling Approaches for the Simulation of Natural Hazards Impacting Protective Structures
V. Singer, K. Sautter, A. Larese, R. Wüchner, K. Bletzinger

particles2023.

Abstract
In recent years, the intensity and frequency of natural hazards such as landslides, debris flow and avalanches have increased significantly due to climate change and global warming. These catastrophic events are responsible for numerous destructions of infrastructures with high economic losses and, even worse, often claim human lives. Therefore, in addition to the prediction, the design and installation of protective structures are of tremendous importance. Due to its hybrid approach of an Eulerian background grid in combination with Lagrangian moving material points, the Material Point Method (MPM) is particularly suited to capture the flow process of those mass movement hazards. For the numerical simulation of protective structures, however, other numerical methods are often preferable. Considering highly flexible structures, which are often utilized due to their high energy absorption capacity classical Finite Element Method (FEM) is best suited to model cable, beam, and membrane elements, while a retaining wall consisting of a few discrete blocks may be preferable modeled by Discrete Element Method (DEM). Therefore, we are proposing partitioned coupling approaches to combine the advantages of different numerical methods so that the protective structures can be appropriately designed to withstand the impact of those mass movement hazards.
Abstract
In recent years, the intensity and frequency of natural hazards such as landslides, debris flow and avalanches have increased significantly due to climate change and global [...]
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Comparison of continuum (PFEM) and discrete (DEM) approaches for large insertion BVPs in soft rocks
J. Zheng, M. Previtali, M. Ciantia, J. Knappett

particles2023.

Abstract
In recent years, significant advancements in computational efficiency have enabled the application of advanced numerical models to solve boundary value problems (BVPs) in geotechnics, including those related to large-displacement problems. However, challenging problems, such as those involving open-ended piles (OEs) in soft rocks, require specialized approaches due to material and geometrical non linearities combined to the large deformation soil-structure interaction. This paper presents a comparison of two approaches for modeling OE pile installation in soft rocks. The first approach employs the Discrete Element Method (DEM), which represents the rock as separate particles bonded together, and introduces a new contact model for highly porous rocks. The second approach uses the Geotechnical Particle Finite Element Method (GPFEM) and investigates the coupled hydromechanical effects during pile installation using a robust and mesh-independent implementation of an elastic-plastic constitutive model at large strains. The DEM approach explores the micromechanical features of pile plugging and unveils the mechanisms behind radial stress distributions inside and outside the plug. The study highlights the strengths and limitations of each modeling approach, providing insights into the behavior of OE piles in soft rocks.
Abstract
In recent years, significant advancements in computational efficiency have enabled the application of advanced numerical models to solve boundary value problems (BVPs) in [...]
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Numerical Simulation of a Laboratory-Scale Free Fall Cone Penetrometer Test in Marine Clay with the Material Point Method
D. Mohapatra, M. SARESMA, J. Virtalaso, W. Solowski

particles2023.

Abstract
This paper shows a numerical replication of a laboratory-scale free fall cone penetrometer test of marine clay. The numerical simulation involves large deformations and considers the destructuration of clay, strain rate effects, and non-linear material behaviour. The numerical simulation well replicates the laboratory experiment captured on a high-speed camera. The penetration process is replicated accurately in time, and the depth of the penetration corresponds to that obtained in an experiment. The simulation results indicate that the numerical framework implemented in Uintah software, consisting of an advanced soil model and the Generalized Interpolation Material Point Method, is well-suited for replication of the dynamic penetration process in soft and sensitive marine clay.
Abstract
This paper shows a numerical replication of a laboratory-scale free fall cone penetrometer test of marine clay. The numerical simulation involves large deformations and considers [...]
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Particle Morphological Effects on the Behaviour of Dry Granular Flow Against Rigid Obstacles
P. Dhanai, B. Bhattacharya

particles2023.

Abstract
Geohazards such as rockfall, catastrophic landslides, and debris flow pose a significant risk due to the rapid movement of the vast amount of granular material carrying tremendous destructive potential and energy. Experimental and numerical studies on channelized flumes have been prevalent in analyzing the kinematics and dynamics of the flow and their interaction with various mitigation measures along the projected flow path. Continuum, discontinuum, and hybrid numerical methods have been successfully employed in the past to comprehend the complex material behaviour of granular mass flows. Although the numerical schemes within a continuum setting offer some insights into critical factors like flow velocity, flow depth, runout distance, etc., the granular interaction within the particle ensemble and the impact force on the barrier system for a better estimate of the force-transmission paths cannot be accounted for. The present study employs the Discrete Element Method to investigate the underlying physics of the micromechanical interaction of the granular assembly with the rigid barrier. Although past studies have explored granular flow-like events within a discrete setting, such studies did not incorporate particle morphology. This paper explores the effect of particle shape on kinematics and impact dynamics against a rigid obstacle. First, the numerical results have been benchmarked against the experimental studies for conventional spherical particles, and then we explore the effect of particle morphology. The present findings indicate that the particle shape significantly influences the flow kinematics and leads to a reduction in impact force on the barrier due to the higher angularity of particles with different morphological features than spherical particles, generally considered in the existing literature. A more significant implication of this study is to better understand and design mitigation measures against geohazards.
Abstract
Geohazards such as rockfall, catastrophic landslides, and debris flow pose a significant risk due to the rapid movement of the vast amount of granular material carrying tremendous [...]
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Examination of the Influence of Particle Parameters on Contact Heat Transfer on a Single Hearth Furnace Floor Using DEM
N. Hilse, S. Scherer

particles2023.

Abstract
In the present paper, contact heat transfer on a batch-operated single circular floor of a multiple hearth furnace is numerically examined using the Discrete Element Method (DEM). The particles are agitated on the floor by a single rabble arm equipped with mixing blades. Two different rabble arm configurations are studied, a rabble arm with three blades covering just the area from the centre of the floor to the wall enclosing the circular floor, and a rabble arm with six blades, which covers the whole diameter of the floor. The floor temperature is set to 100°C, and the initial particle temperature is 20°C. Spherical particles made of aluminium and polyoxymethylene (POM) with two particle diameters (10 and 20 mm) are examined. Blade angle inclination is varied, namely, 0°, 45° and 90°. The major results are that for POM spheres the major mechanism dominating contact heat transfer is the gas layer in the vicinity of the contact point particle-floor, whereas for aluminium the heat transfer through the direct contact point of floor and particle is of equal importance as the heat transfer through the gas layer. For the first configuration with three blades, a larger blade angle leads to lower heat up rates, while the second configuration with six blades, increases the heating rate for larger blade angles.
Abstract
In the present paper, contact heat transfer on a batch-operated single circular floor of a multiple hearth furnace is numerically examined using the Discrete Element Method [...]
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Non-Fourier heat conduction with phase change using Hyperbolic Lattice Boltzmann Method by modifying the Equilibrium distribution function
S. Srivastava, M. Mariappan

particles2023.
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Skin Layer Formation in Plate Model for Coupled Analysis of Injection Molding Process of Bonded Magnets
Y. Uematsu, K. Hirata, F. Miyasaka, T. Kitamura, T. Kikugawa

particles2023.

Abstract
The bonded magnet, which is formed by mixing magnet materials such as neodymium-based and ferrite-based materials with resin, has the characteristic of being able to be formed into small and complex shapes due to the resin being the binding material. It is used in small motors embedded in hard disk drives and motors for home appliances. The major methods for forming bonded magnets are compression molding and injection molding. In this study, injection molding is selected, which can easily apply to complex shape compared to compression molding. However, injection molding has the disadvantage of variability in density and magnetic properties of the molded products. This is due to the difficulty in observing the material flow, as the molding process progresses inside the mold and multiple processes occur simultaneously such as injection, compression, magnetization, and curing. Therefore, determining the optimal molding parameters for injection molding of bonded magnets requires numerous experimental trials. Based on the above, it is believed that predicting the behavior of resin inside the mold during the molding process using numerical simulation can provide guidelines for determining the optimal molding parameters. The authors have previously proposed a coupled analysis method of "fluid analysis and temperature analysis using MPS (Moving Particle Simulation) method, and magnetic field analysis using magnetic moment method." The objective of this study is to assess the solidification process of resin on the mold surface, utilizing a rectangular-shaped mold model.
Abstract
The bonded magnet, which is formed by mixing magnet materials such as neodymium-based and ferrite-based materials with resin, has the characteristic of being able to be formed [...]
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Numerical Investigation of Pressuremeter Test with Material Point Method
H. Kurugodu, P. Vangla, D. Frost, D. Bhattacharya

particles2023.

Abstract
In situ tests for geotechnical investigations can provide a reliable prediction of the soil behaviour because they accurately represent the stress state while preserving the soil structure and the inherent material fabric. These tests complement the information obtained from laboratory element tests on undisturbed or reconstituted specimens. The pressuremeter test is one such example of an in-situ tool that is used to obtain soil properties based on measured pressure-volume data. The pressuremeter test is considered a large deformation problem within a numerical framework. Furthermore, it is commonly idealized as a cylindrical cavity expansion within the realms of conventional finite element schemes. In order to address the issue related to excessive mesh distortion aspects, the Eulerian-Lagrangian approach developed within a continuum framework, namely the Material Point Method (MPM), has been adopted in the present study to investigate the pressuremeter expansion process. First, the results obtained are benchmarked against those from classical cavity expansion problems for a pressure-dependent frictional material. The computed results are in good agreement with both the closed-form solutions and displacement-controlled experiments reported in the literature. A parametric study was performed to further investigate the influence of the loading rate, material properties, and heterogeneities on the pressuremeter test simulations.
Abstract
In situ tests for geotechnical investigations can provide a reliable prediction of the soil behaviour because they accurately represent the stress state while preserving the [...]
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Deformation characteristics of bimetallic clad pipes in the stratigraphic subsidence area
L. LV, T. Hu

Land subsidence (2023). 1

Abstract
One of the primary methods for preventing corrosion in oil and gas field gathering pipelines is bimetallic clad pipe. To reveal the failure mechanism of bimetallic clad pipes under the stratigraphic subsidence area. The bimetallic clad pipe mechanics model for the ground subsidence area was established. Investigated were the effects of working internal pressure, outer base pipe wall thickness, liner pipe wall thickness, and subsidence displacement on the pipe-soil subsidence deformation process, pipe axial strain, ovalization, liner and outer pipe separation, and changes in liner pipe wall thickness. The results demonstrate that as ground subsidence displacement increases, cross-sectional ovalization and maximum axial strain increase, making the separation of the liner and outer pipes more obvious and the wall thickness of the liner pipe thinner. The degree of ovalization of the outer base pipe and the separation of the liner and outer pipes are slowed down by increasing internal pressure. The wall thickness of the liner and outer pipes is increased to slow the separation of the interface.
Abstract
One of the primary methods for preventing corrosion in oil and gas field gathering pipelines is bimetallic clad pipe. To reveal the failure mechanism of bimetallic clad pipes [...]
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Importance of Periodic Boundaries or Frictionless Walls in Simulating Elementary Response of Angular Particles
U. Ali, M. Kikumoto, M. Ciantia, M. Prevatali, Y. Cui

particles2023.

Abstract
In the discrete element method (DEM), the granular response is affected by the selection of boundary conditions, thereby emphasizing the importance of their careful consideration [1]. Replicating the boundary conditions employed in experiments is crucial to have a quantitative agreement between the response observed in the simulation and laboratory test [2]. In this study, a calibrated and validated DEM model was utilized to perform a series of simulations featuring regular polygons with varying numbers of corners subjected to different boundary conditions. The aim was to examine the combined effect of particle shape and boundary conditions on the mechanical response of granular assemblies. Simulations were performed under three boundary conditions: rigid frictional walls (in which the friction between the particle-wall interface is equal to that between the particle-particle interface), rigid frictionless walls, and periodic boundary conditions (PBC). Interestingly, it was observed that qualitatively, the effect of particle shape on granular response was invariant, irrespective of boundary conditions employed. However, quantitatively, the shear strength of all shapes was significantly affected by boundary settings, with the maximum and minimum strengths exhibited under rigid frictional walls and periodic boundaries, respectively. The magnitude of the decrease in shear strength due to boundary conditions was contingent upon the particle shape, with angular assemblies demonstrating a significant change in strength relative to round assemblies. Angular particles in contact with rigid wall frictional boundaries exhibited lesser rotations, thereby inducing relatively significant shear forces on the walls, particularly those parallel to the shearing direction. On the other hand, round particles in contact with walls rotated to a greater extent, resulting in little or negligible shear forces with the walls. Furthermore, boundary conditions also affected deformation patterns, including the development of shear bands.
Abstract
In the discrete element method (DEM), the granular response is affected by the selection of boundary conditions, thereby emphasizing the importance of their careful consideration [...]
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Failure of Cohesive Granular Columns: Friction and Contact Adhesion
L. Staron, L. Duchemein, P. Lagree

particles2023.

Abstract
This contribution focuses on the influence of the existence of a debonding length onto the behaviour of a cohesive granular sample. We apply a contact dynamics algorithm to study the effect of both contact adhesion strength and debonding length on the failure of a cohesive step, analysing a set of independent simulations. Contact adhesion strength coincides with stronger pile stability and larger apparent friction in the absence of any debonding length. We show that the existence of a larger debonding length amplifies this phenomenology. At large adhesion strength, we observe the existence of a sharp modification of the behaviour of the system even in the case of a very small debounding length, compared to the case of the absence of the latter. We compare the performance of the algorithm in the different cases, and show how increasing the debonding length leads to a better precision of the hard-core.
Abstract
This contribution focuses on the influence of the existence of a debonding length onto the behaviour of a cohesive granular sample. We apply a contact dynamics algorithm to [...]
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One Discrete Element vs. Two Finite Elements and the Arbelos of Archimedes
D. Reischl

particles2023.

Abstract
In this article, a visual proof is given that for a certain simple, yet analytically challenging mechanical system a unique solution exists, which can be found by simple fixed-point iteration as easily to be performed by the reader. As turns out, this system is mostly intractable by means of the finite element method, yet being easily manageable by means of the distinct/discrete element method. Thus, this article gives evidence to the assumption that systems exist which may yield almost arbitrarily wrong results when treated with the finite element method, while giving arbitrarily accurate results when handled by means of the discrete element or similar method.
Abstract
In this article, a visual proof is given that for a certain simple, yet analytically challenging mechanical system a unique solution exists, which can be found by simple fixed-point [...]
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Comparative Analysis of Softening Contact laws in Particle Models: Application to Rock and Concrete
M. Braga-Farinha, N. Monteiro-Azevedo, S. Oliveira

particles2023.

Abstract
In this work three constitutive contact models that include softening are adopted for particle model fracture studies in both rock and concrete. For a single local contact, the constitutive contact model performance is initially compared in tensile, pure shear and shear tests under constant axial. Additionally, compression, direct tensile, and confined triaxial tests of quasi-britlle material discretized with spherical particles are presented and the predicted macroscopic response is compared. For a single local contact, the three contact models predict a similar behaviour. As shown, it is possible to calibrate each contact model to reproduce complex macroscopic behaviour observed in rock and concrete, but each contact model requires different contact properties or particle generation procedures
Abstract
In this work three constitutive contact models that include softening are adopted for particle model fracture studies in both rock and concrete. For a single local contact, [...]
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Discrete numerical modelling of capsule-asphalt mixture system for self-healing purposes
G. Câmara, N. Monteiro-Azevedo, R. Micaelo

particles2023.

Abstract
Asphalt mixture faces damage due to vehicle speed, repeated loads, and ultraviolet radiation over time, regardless of being a self-healing material. Induced healing mechanisms are necessary to promote autonomous pavement recovery due to adverse in-service conditions, and the capsule-asphalt mixture system incorporating low-viscosity oils (rejuvenators) has shown to be a possible solution in laboratory tests. This study aims to numerically investigate the effect of rejuvenator-modified mastic (activated capsules) on the stiffness properties of asphalt mixtures within the discrete element method. A three-dimensional model previously validated for rejuvenator-modified mastics with different rejuvenator-to-bitumen ratios (0, 2.5, and 10 wt%) is adopted. A generalised Kelvin contact model represents the time-dependent contacts, and its contact parameters define the rejuvenator amount in the mastic phase. The analysis assesses the impact of the modified mastic amount and the rejuvenator-to-bitumen ratio. Results show that the increasing modified mastic content progressively reduces the mixture dynamic modulus. When the total mastic phase has rejuvenator-modified properties, the mixture stiffness modulus significantly reduces, and the phase angle performs differently from the expected (decrease with frequency) at a 10% rejuvenator-to-bitumen ratio due to the excessively softened state, possibly compromising the pavement mechanical performance. For a 0.30 wt% modified mastic ratio case adopting a local effect, the embedded elements do not significantly influence the mixture rheological properties, especially the stiffness modulus, which may be insufficient for self-healing purposes. Nevertheless, the negligible impact on the phase angle highlights the potential of the rejuvenator-modified asphalt mixture across different traffic and temperature condition
Abstract
Asphalt mixture faces damage due to vehicle speed, repeated loads, and ultraviolet radiation over time, regardless of being a self-healing material. Induced healing mechanisms [...]
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SPH modeling of advanced materials in hypervelocity impact simulations
A. Cherniaev, A. Gudisey

particles2023.

Abstract
Spacecraft must be analyzed for their ability to survive hypervelocity impacts (HVI) by orbital debris, as collision of a space vehicle with even a millimeter-sized object traveling at a typical orbital speed (7 km/s and higher) can be detrimental for both the spacecraft and the orbital environment. Due to the high cost of the physical HVI experiments, numerical modeling plays a significant role in conducting such analyses. In particular, the smoothed particles hydrodynamics technique (SPH) was previously found applicable for simulating scenarios involving extreme deformations and fragmentation, including hypervelocity impact. With the extensive use of advanced lightweight materials in space structures, it is important to find a rational way of representing them using the SPH framework. This study reports the results of SPH modeling of two distinct types of lightweight materials often employed in space structures: open-cell foams and fiber-reinforced composites. For foams, explicit representation of their complex mesoscopic architecture was achieved by filling the STL exteriors (generated using X-ray computed tomography) with SPH particles. For laminated composites, ply-wise representation was obtained using finite elements that could locally and adaptively transform to SPH particles when the elements become highly distorted and inefficient. Results of HVI simulations involving foams and composites were compared with available experimental data. The advantages and limitations of the modeling techniques are discussed. Spacecraft must be analyzed for their ability to survive hypervelocity impacts (HVI) by orbital debris, as collision of a space vehicle with even a millimeter-sized object traveling at a typical orbital speed (7 km/s and higher) can be detrimental for both the spacecraft and the orbital environment. Due to the high cost of the physical HVI experiments, numerical modeling plays a significant role in conducting such analyses. In particular, the smoothed particles hydrodynamics technique (SPH) was previously found applicable for simulating scenarios involving extreme deformations and fragmentation, including hypervelocity impact. With the extensive use of advanced lightweight materials in space structures, it is important to find a rational way of representing them using the SPH framework. This study reports the results of SPH modeling of two distinct types of lightweight materials often employed in space structures: open-cell foams and fiber-reinforced composites. For foams, explicit representation of their complex mesoscopic architecture was achieved by filling the STL exteriors (generated using X-ray computed tomography) with SPH particles. For laminated composites, ply-wise representation was obtained using finite elements that could locally and adaptively transform to SPH particles when the elements become highly distorted and inefficient. Results of HVI simulations involving foams and composites were compared with available experimental data. The advantages and limitations of the modeling techniques are discussed. Spacecraft must be analyzed for their ability to survive hypervelocity impacts (HVI) by orbital debris, as collision of a space vehicle with even a millimeter-sized object traveling at a typical orbital speed (7 km/s and higher) can be detrimental for both the spacecraft and the orbital environment. Due to the high cost of the physical HVI experiments, numerical modeling plays a significant role in conducting such analyses. In particular, the smoothed particles hydrodynamics technique (SPH) was previously found applicable for simulating scenarios involving extreme deformations and fragmentation, including hypervelocity impact. With the extensive use of advanced lightweight materials in space structures, it is important to find a rational way of representing them using the SPH framework. This study reports the results of SPH modeling of two distinct types of lightweight materials often employed in space structures: open-cell foams and fiber-reinforced composites. For foams, explicit representation of their complex mesoscopic architecture was achieved by filling the STL exteriors (generated using X-ray computed tomography) with SPH particles. For laminated composites, ply-wise representation was obtained using finite elements that could locally and adaptively transform to SPH particles when the elements become highly distorted and inefficient. Results of HVI simulations involving foams and composites were compared with available experimental data. The advantages and limitations of the modeling techniques are discussed.
Abstract
Spacecraft must be analyzed for their ability to survive hypervelocity impacts (HVI) by orbital debris, as collision of a space vehicle with even a millimeter-sized object [...]
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Comparative Study of Methods to Generate C^2 Continuous Mesh-free Basis using the Moving Least Squares Method
G. Bridhani, U. Savaran

particles2023.

Abstract
This study investigates the ability of three different approaches for constructing smooth and continuous mesh-free basis functions, namely: (i) assuming one degree of freedom per node with the moving least squares method, (ii) assuming six degrees of freedom per node with moving least squares method, and (iii) assuming six degrees of freedom per node with Hermite-type moving least squares method. Further, it provides evidence that all three approaches can generate continuous mesh-free basis functions;however, the first and third approach results in a C2 continuous mesh-free basis, where the function and its first and second-order derivatives are related. Finally, a comparative study is performed among the three approaches using fourth-order polynomial basis and fifth-order spline weight function.
Abstract
This study investigates the ability of three different approaches for constructing smooth and continuous mesh-free basis functions, namely: (i) assuming one degree of freedom [...]
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Advanced Structure Modelling Using the Bonded-Particle Method: Enabling Complex Capabilities for Structures in DEM Simulations
E. Fimbinger

particles2023.

Abstract
Bonded-particle modelling is a powerful approach for simulating particle made structures with enhanced abilities, i.e., structures that are able to deform, brake/fracture, and thus interact with other particles of a DEM simulation in an enhanced complex manner. This modelling approach is based on connecting particles with beam elements (commonly termed bondings, with each bonding connecting two particles) to create a bonded-particle model (BPM), typically consisting of a large number of particles and bondings. The behaviour of such a BPM can be adjusted in two categories: via properties related to the particles, e.g. their mass, shape, or frictional characteristics, and via properties related to the bondings, e.g. their Young’s moduli or breakage criteria. This contribution presents developments in complex bonded-particle modelling for achieving flexible/deformable and breakable/fracturable structures and highlights the enhanced capabilities made possible by using this approach. For this purpose, various applications for bonded-particle modelling in DEM simulations are presented, with selected case studies each demonstrating the effectiveness of bonded-particle modelling in solving practical engineering problems, including: - 1D BPMs, e.g., deformable beams or ropes and chains, - 2D BPMs, e.g., membranes, textiles, nets, bags, shell-like parts (e.g. silos), or conveyor belts (with particular reference to dynamic belt simulation), and - 3D BPMs, e.g., complex-breakable structures (e.g. with considering crack formation or dynamic impact handling; e.g. illustrated on filter cake material). Furthermore, possible interaction scenarios, including interactions of BPMs to particles, rigid parts, other BPMs, or even in terms of SPH (Smoothed-Particle Hydrodynamic) or MBD (Multibody Dynamics), are addressed. Finally, current developments and potential future directions in this field are outlined, and potentials for extending this modelling approach to further application areas are discussed.
Abstract
Bonded-particle modelling is a powerful approach for simulating particle made structures with enhanced abilities, i.e., structures that are able to deform, brake/fracture, [...]
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Contact Detection Algorithm for Convex NURBS Particles
M. Craveiro, A. Gay-Nieto, P. Wriggers

particles2023.

Abstract
The present work proposes a contact detection algorithm for convex particles whose boundaries are mathematically defined by non-uniform B-splines (NURBS). This algorithm involves a hierarchy of contact searches, including both global and local steps. The focus is on the formulation of the local contact problem (LCP) using a master-to-master approach. It is based on computer graphics and optimization techniques. Besides the algorithm, the paper also discusses strategies for modeling particle geometry and their implications in contact detection. The use of multiple parameterizations (patches) assembled in space, for instance, provides more flexibility in the construction of particles and avoids numerical singularities. However, it leads to local geometric imperfections at the connection between patches. The LCP formulation proposed herein can deal with such imperfections through a contact degeneration technique. An example shows the robustness of the method.
Abstract
The present work proposes a contact detection algorithm for convex particles whose boundaries are mathematically defined by non-uniform B-splines (NURBS). This algorithm involves [...]
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Improving asphalt discrete numerical modelling with realistic particle shapes
R. Micaelo, N. Monteiro-Azevedo, G. Câmara

particles2023.

Abstract
Micromechanical modelling based on the Discrete Element Method (DEM) has been widely used to investigate asphalt behaviour due to its ability to represent an irregular microstructure with variable-sized aggregates, bitumen and voids. The 3D rigid particle models with randomly distributed spherical particles and adopting elastic and/or simple viscoelastic models at the contacts are the standard approach, however, in recent years, a significant research effort is noted to incorporate real particle morphologies in the numerical models. In this study, a previously developed 3D DEM model of asphalt employing a generalised Kelvin contact model formulation for the viscoelastic contacts is further improved with realistic particle shapes representing the coarse aggregates. A digital library of aggregate shapes was created from the X-ray computed tomography (CT) scan of an asphalt specimen, using an adaptive image-processing method to separate the aggregates in the CT images and the Delaunay triangulation method to define the aggregate 3D surface model. Several virtual aggregates with different sizes were selected from the library to represent the coarse aggregate gradation of the modelled 3D DEM asphalt specimen. Each virtual aggregate is discretized with smaller spherical particles and its deformability is taken into account through the inner particle contacts. The numerical asphalt specimens with realistic particle shapes were submitted to uniaxial tension-compression cyclic tests to determine the stiffness properties, and the results were compared with those of the numerical specimens with all constituents represented by single spherical rigid particles. As shown, the proposed methodology greatly enhances the 3D DEM model's ability to simulate the asphalt behaviour.
Abstract
Micromechanical modelling based on the Discrete Element Method (DEM) has been widely used to investigate asphalt behaviour due to its ability to represent an irregular microstructure [...]
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Investigation of Dynamic Characteristics of Rolling-Ball Dampers
K. Nagashima, M. Saeki

particles2023.

Abstract
Tuned mass dampers, consisting of a mass, spring, and damper, are widely used for vibration suppression in structures. Despite being small and lightweight, these dampers exhibit excellent damping effectiveness. However, there are issues such as performance degradation due to the aging of the spring and damper, as well as the need for frequent maintenance. Therefore, as an alternative vibration control device that does not rely on these components, a rolling-ball damper is proposed. This damper consists of a container with a lid and multiple enclosed particles on its curved surface. By utilizing the contact between particles and the friction between particles and the container, the rolling-ball damper can absorb and suppress the vibration energy imposed on the structure to which the container is attached. In this study, we investigated the characteristics of the rolling-ball damper in a horizontal vibration system. We experimentally verified the effects of the size and number of enclosed particles on damping performance. Furthermore, numerical simulations were conducted by the discrete element method using EDEM® software and the multibody dynamics simulation method using MotionSolve® software. A comparison between experimental and numerical simulation results demonstrated the effectiveness of numerical calculations in predicting the amplitude response
Abstract
Tuned mass dampers, consisting of a mass, spring, and damper, are widely used for vibration suppression in structures. Despite being small and lightweight, these dampers exhibit [...]
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Experimental and Numerical Studies on the Efficiency of Damping upon Horizontal Stirring of Granular Materials
K. Ishizeki, M. Saeki

particles2023.

Abstract
In this study, the damping torque exerted on a horizontally rotating blade in granular materials under gravity was investigated. To capture the stirring behaviour of the granular materials in detail, a mechanical stirring apparatus was fabricated. The rotating blade was driven sinusoidally by a shaker through a ball screw mechanism. It was found that energy dissipation depends on various parameters such as particle material and particle size. Energy dissipation was also calculated using the EDEM® software based on the discrete element method. To verify the validity of the numerical simulation model, numerical simulation results were compared with experimental results.
Abstract
In this study, the damping torque exerted on a horizontally rotating blade in granular materials under gravity was investigated. To capture the stirring behaviour of the granular [...]
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Fast Point-To-Mesh Distance Computation Technique Based On Cell Linked List For Polygon-Wall Boundary In Moving Particle Semi-Implicit Method
M. Teixeira, L. Pereira, R. Amaro, L. Cheng

particles2023.

Abstract
The simulation of fluid-structure interaction (FSI) problems usually involves many degrees of freedom, and a considerable number of particles is generally required to model both fluid and solid domains. In relation to the modeling of solid walls by particles, the use of triangular meshes provides more efficient and smoother representation of complex-shaped solid surfaces as well as the straight coupling between particle and mesh-based methods, which is suitable for FSI applications. However, in the particle-based simulations with solid boundaries modeled by mesh, the computation of the particle-mesh distances is a critical time-consuming task, and a fast technique is of major importance. Taking advantage of the cell linked list structure widely adopted for fixed-radius neighborhood search algorithms in particle methods, we proposed a Fast Point-to-mesh Distance computation technique based on Cell linked list (FPDC). Alongside this new technique, a particle-polygon wall contact model was introduced to enable simulations of the collision between the surface of the moving bodies and fixed wall represented, respectively, by particles and mesh. The results show that the proposed technique provides a significant processing time speedup and can be used for practical large-scale problems.
Abstract
The simulation of fluid-structure interaction (FSI) problems usually involves many degrees of freedom, and a considerable number of particles is generally required to model [...]
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A coupled DEM-CFD model to study the physical behavior of loose armor revetments in maritime waterways
J. Sorgatz, M. Herbst, H. Konietzky, M. Pohl

particles2023.

Abstract
Revetments serve to protect a canal or river bank against erosion caused by natural and ship-induced waves and currents. A profound understanding of loads and resistances acting on revetments is indispensable for an economic and sustainable, but also safe revetment design. This paper presents a coupled CFD-DEM model (Computational Fluid Dynamics and Discrete Element Method) to study the physical behavior of loose armor stone revetments in maritime waterways. The waves and currents are modelled with a CFD add-on for the particle-based DEM software PFC3D. The DEM approach allows to simulate the shape, size and mass distribution and displacement of the individual armor stones realistically. DEM and CFD are coupled to capture the response of the armor stones to the hydraulic loads. In this paper, the model calibration and validation are presented using data derived from a full-scale flume experiment. The numerical model is compared to the flume tests where a slope is subjected to flow at different velocities. It can be shown that the implementation of revetment and hydraulic loads provides results that are consistent with the experimental data. Both flow velocities and armor stone displacements agree well between the physical and the numerical model. The herein presented study thus provides the basis for the application of the numerical model to more advanced stability analyses of revetments that are, e. g., subjected to wave and current attack.
Abstract
Revetments serve to protect a canal or river bank against erosion caused by natural and ship-induced waves and currents. A profound understanding of loads and resistances [...]
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Elastic Behaviour of Linear Structures Using Modal Superposition and Lagrangian Differencing Dynamics
M. Paneer, J. Basic, I. Lozina, D. Sedlar, C. Peng

particles2023.

Abstract
Elastic deformation and dynamics response of the linear structures due to fluid loads are studied to understand the Fluid Structure Interaction (FSI). A modal coupling solver is developed by solving dynamic equation of motion with external loads, using the mode superposition method with the help of relevant mode shapes and natural frequencies associated with the structure. Natural frequencies and mode shapes have been pre-calculated and provided as input for the simulation. Modal coupling is integrated into the Lagrangian Differencing Dynamics (LDD) method, utilizes finite differences within the framework of Lagrangian context, and strong and implicit formulation of Navier Stokes equations to model the incompressible free-surface fluid. Elastic deformation of the structure due to fluid force obtained from the flow solver is calculated in the modal coupling algorithm using direct numerical integration. Then the elastic deformation is imposed in the flow solver to account for change of the geometry and obtain new flow pressure and velocity fields. The two-way coupling of fluid and structure is successfully validated by simulating dam-break through an elastic gate. Since the LDD method works directly on surface meshes, the simulation is quickly setup and direct coupling of structural deformation eliminated the usual step of mapping of fluid results on the structural mesh and vice-versa
Abstract
Elastic deformation and dynamics response of the linear structures due to fluid loads are studied to understand the Fluid Structure Interaction (FSI). A modal coupling solver [...]
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A DEM-FEM Coupling Framework Applied to Railroad Infrastructure Simulations
A. Ullrich, J. Quist, C. Cromvik, K. Jarateg, A. Bilock

particles2023.

Abstract
Swedish and other European governments invest significant resources in railroad infrastructure, including maintenance and construction. The degradation of track ballast layers is one of the most critical maintenance issues. Hence, it is of significant interest for infrastructure owners to find novel solutions to mitigate the problem by improving design and maintenance operations. However, established tools for the simulation of railroad systems typically consider the ballast as a solid continuum structure, while in practice, the discrete nature of the particle assembly has to be accurately represented in the model. The sleepers and rails must be modelled as solid structures, which results in the complex coupled problem of combining particulate and structural analysis models. In this paper, the simulation of railroad infrastructure with the example of a transition zone is performed with an explicit surface coupling algorithm of the Discrete Element Method (DEM) and the Finite Element Method (FEM). The ballast layer is represented by individual particles in DEM, where the computations are performed on the GPU. This study focuses on the comparison between a convex and a non-convex particle shape. The rail system with sleepers and the subground with varying stiffness is modelled with solid structures in FEM. Properties of the ballast bed, such as the particle shape, are found to have a significant impact on the stiffness within the bed and the deflection of the sleepers and rails. Furthermore, the sudden transition from low to high stiffness causes a peak in tensile stress in the subground. The results show that accurate particle shape representation and high computational performance are critical aspects of achieving predictions on a relevant scale. Studying the ballast layer as a particulate system provides a new perspective on dynamics in tracked ballast structures.
Abstract
Swedish and other European governments invest significant resources in railroad infrastructure, including maintenance and construction. The degradation of track ballast layers [...]
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Computational Modeling of Cold Spray Process Using Particle-based Methods
J. Qi, R. Raoelisin, J. Li, M. Rachik

particles2023.

Abstract
Cold gas dynamic spraying (CGDS), as a high strain rate shearing and innovative solid-state technique enables to rapidly develop additive manufacturing and coating for metal deposition. This paper investigates the development and evolution of various interfacial bonding characteristics during high strain rate shearing process through Multiphysics numerical simulations of single particle impact. Two different particle-based modeling strategies such as smoothed particle hydrodynamics (SPH), molecular dynamics (MD) are investigated using commercial software ABAQUS/Explicit and LAMMPS, respectively. To separate the difficulties related to complex metallurgy of alloys, our first investigations focus on pure aluminum. The Johnson-Cook (J-C) constitutive model is used to describe the high strain rate self-consolidation process in SPH modeling. Embedded Atom Method (EAM) is used to describe the interactions between Aluminum atoms in MD modeling. The predictions from the different particle-based models are compared with each other and with experimental results. Through the investigations, SPH numerical approach has strong advantage in capturing the phenomena that occur during the cold spray process. It is able to describe the complex features of particle and substrate, especially in the interface vicinity. At the same time, MD numerical approach gives the fundamental understanding of the deposition behavior at the atomistic level. The key finding is the strong relationship between the un-uniform distribution of shear strain and jet formation during high-speed collision. Plastic strain along with an increase of temperature lead to thermal softening of pure Aluminum resulting in metallurgical bonding at the interface.
Abstract
Cold gas dynamic spraying (CGDS), as a high strain rate shearing and innovative solid-state technique enables to rapidly develop additive manufacturing and coating for metal [...]
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Particle-based Flow Simulation of Molten Aluminum Alloy Through Casting Filters
T. Deguchi, K. Taki, Y. Maeda

particles2023.

Abstract
Casting defects can be predicted in advance of practice and countermeasures can be taken to improve casting quality and increase productivity. Applying the casting filters is a method of improvement methods for defects caused by unsuitable molten metal flow. Casting filters have the effect of removing inclusions in molten metal and rectifying the flow. However, specific conditions such as the type, pore size, and setting position of the casting filter are not clear. Casting filter conditions are determined by conventional empirical rules that are not theoretical. In the other view, the use of casting CAE is essential to realize front-loading for the process design process, in which casting defects are predicted in advance of practice and countermeasures are taken. In the previous study, K. Taki et al. performed direct observation of mold filling and flow simulations passing through the casting filter. The particle-based COMINA CAE software was used for the flow simulation of molten metal in complex interior geometries in the filter. The calculations used a model of the filter that was reproduced on an X-ray CT system. To inspect the filter performance it was necessary to make a small and simplified filter model, which is called the 1/4 model of filter. In the present study, the flow dynamics through the filter are investigated using various 1/4 models. The 1/4 model maintains permeability on the surface and porosity of volume while halving the dimensions. As a result, we succeed in reproducing the flow behaviour of molten metal when it passed through the filter by setting the particle size of molten metal to 1/16 of the filter’s pore diameter. Further, we try to evaluate the performance of the filter by extending the calculation target from only the area around the filter to the entire mold. If mold filling behavior for the mold with filter could be simulated, it wouldbe used effectively in casting geometry design and defect countermeasure.
Abstract
Casting defects can be predicted in advance of practice and countermeasures can be taken to improve casting quality and increase productivity. Applying the casting filters [...]
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Examination of Variable Tilting Speed on Flow Behaviour during Ladle Pouring in Die Casting using SPH Simulation
F. Itakura, T. Yamada, Y. Maeda, A. Hasuno, Y. Mochida

particles2023.

Abstract
Disturbance of the molten metal flow during ladle pouring before the plunger advancing in the aluminium alloy die casting process can cause entrapment defects of air and oxide film. Slow pouring to control the turbulence of the flow front reduces productivity due to increased cycle time. Further, the risk of cold flake formation increases caused by large temperature drops in accordance with the long cycle time. On the other hand, rapid pouring is desired to improve productivity, but the risk of air entrapment increases. Therefore, quick and quiet pouring is desired in the ladle pouring process. In the present study, we focus on variable tilting speed as a method to achieve good ladle pouring. The effects of variable ladle tilting speed and switching time on the wave behavior of molten metal are investigated in visualization experiments and simulations. The flow behaviours in ladle pouring are simulated using ”COLMINA CAE”, which is the casting analysis software by particle-based SPH method. Furthermore, the plunger advancing process is also examined. From the simulation results, the variable tilting speed from fast to low can suppress the rise of the maximum wave height of molten aluminium alloy. However, the pouring completion time is longer. Further, the falling position of molten metal poured from the ladle varied with changing tilting speed. And then, the wave height is influenced not only by ladle pouring but also by the plunger advancing process. These trends of wave behaviour obtained in the simulation are similar to that of the actual phenomenon. Therefore, the present simulation method can accurately estimate the ladle pouring process and plunger advancing process. So, casting CAE is an effective tool for exploring die casting conditions.
Abstract
Disturbance of the molten metal flow during ladle pouring before the plunger advancing in the aluminium alloy die casting process can cause entrapment defects of air and oxide [...]
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Comparison of Incompressible and Weakly-Compressible SPH for the Simulation of Laser Beam Welding
D. Sollich, P. Eberhard

particles2023.

Abstract
The process of laser beam welding is simulated using the Weakly-Compressible Smoothed Particle Hydrodynamics (WCSPH) and the Incompressible SPH (ISPH) methods. The presented models consider significant physical effects such as heat conduction, temperature-dependent surface tension with wetting, the phase transitions melting and solidification, and an evaporation-induced recoil pressure. Here, particular emphasis is placed on the modeling differences between the WCSPH and ISPH methods. Then, both methods are evaluated in terms of their accuracy and performance in the simulation of deep penetration laser beam welding with oscillating laser power.
Abstract
The process of laser beam welding is simulated using the Weakly-Compressible Smoothed Particle Hydrodynamics (WCSPH) and the Incompressible SPH (ISPH) methods. The presented [...]
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Calibration of AM powders for Optimization of Recoating Applications using DEM
N. Sani, J. Quist, K. Jarateg, A. Bilock, L. Cordova, F. Edelvik

particles2023.

Abstract
Additive Manufacturing (AM) has been a subject of significant attention from both industrial manufacturers and research communities. However, several challenges hinder the widespread implementation of this technology in the industry. Powder recoating is a crucial step in powder-bed AM process that involves achieving a uniformly packed bed of powder particles that are later melted by an energy source, such as a laser or electron beam. One of the main challenges is calibrating the contact model parameters accurately to match the flowability and spreadability of specific powder alloys. This paper proposes a Discrete Element Method (DEM) model calibration framework based on surrogate model optimisation. The study utilises a Revolution Powder Analyser (RPA) as the experimental reference system. The proposed method is demonstrated with two AM powder samples, Ti64 and Inconel 718. The results indicate that particle-particle friction, rolling resistance, and van der Waals (vdW) surface energy significantly affect the system responses. Furthermore, the validation results show good correspondence between the simulation with calibrated parameters and experimental data. Overall, proposed calibration framework has the potential to optimise powder recoating and to improve the accuracy and effectiveness of the additive manufacturing.
Abstract
Additive Manufacturing (AM) has been a subject of significant attention from both industrial manufacturers and research communities. However, several challenges hinder the [...]
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How the Packing Density and Penetration Resistance is Influenced by Particle Shape: DEM Modelling of Plate Penetration in Granular Media
G. van Selm, M. Mohajeri, H. Shi, D. Schott

particles2023.

Abstract
Granular materials play a crucial role in various geotechnical, mining, and bulk handling applications. Understanding their mechanical properties is essential for optimal use in these industries. Traditional experimental methods like Cone Penetration Test (CPT) and open pile testing have limitations on their repeatability and offer little insight into the contact mechanics. The Discrete Element Method (DEM) is a powerful tool for investigating and simulating granular material behaviour at the element scale and provides deeper understanding in geometry-material interactions. However, due to computational costs, spherical particles are often preferred, though they may not always capture realistic particle interactions. In the current study, the packing density and the penetration resistance of particle beds with different particle shapes, including sphere, multi-spheres and polyhedrons, are compared using a plate penetration test modelled in DEM. Sensitivity analyses are performed for sliding friction, consolidation pressure, and Particle Size Distribution (PSD). Results indicate that polyhedral shapes show lower penetration resistance compared to spherical and multi-spherical shapes. Sliding friction has the most significant impact on resistance, while consolidation pressure has minimal effect on porosity. The study highlights the importance of particle shape in granular media modelling and emphasizes the need for further research in this area.
Abstract
Granular materials play a crucial role in various geotechnical, mining, and bulk handling applications. Understanding their mechanical properties is essential for optimal [...]
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ISPH with a Geometric Multigrid Preconditioning Solver using Background Cells in GPU environment
H. Osaki, D. Moriwaka, M. Asai

particles2023.

Abstract
Incompressible fluid analysis using the ISPH or MPS methods requires the solution of the pressure Poisson equation, which takes up most of the overall computation time. In addition, the iteration number for solving pressure Poisson equations may increase as the simulation model scale increases. This is a common problem in particle methods and the other implicit time integration solvers. In different methods, FEM, etc., good quality preconditioning, such as multigrid preconditioning, can significantly improve the convergence of iterative solution methods. There are two types of multigrid preconditioners, algebraic multigrid and geometric multigrid methods, but there are few examples of their application in particle methods. In this study, we attempted to develop a framework for a geometric multigrid preconditioner for solving the pressure Poisson equation in the ISPH. First, we focused on the geometric multigrid preconditioner using background cells, which are used for neighboring particle search, and implemented it on a GPU environment. Through a simple dam-break problem, we compared the computation time between the Conjugate gradient (CG) solver with a traditional preconditioner and the CG solver with a geometric multigrid preconditioner. We confirmed that the background cell-based geometric multigrid preconditioner is practical for the ISPH method.
Abstract
Incompressible fluid analysis using the ISPH or MPS methods requires the solution of the pressure Poisson equation, which takes up most of the overall computation time. In [...]
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A Macro-Meso-Microscale Meshless Model for Multiphysics Particle-Laden Flows
J. Joubert, D. Wilke, P. Pizette

particles2023.

Abstract
This work extends a multi-phase mixing model framework designed for a Smoothed Particle Hydrodynamics context. Specifically, we propose a higher-order variation using the first-order accurate Generalised Finite Difference differential operators to construct an incompressible scheme for simulating fluid-solid coupled systems resolved via a continuum mixture model. The proposed scheme incorporates inter-phase shear between phases and the viscosity dependency of the solid phase concentration. The scheme is verified by simulating a modified lid-driven cavity case at Re = 1000. In this simulation, our method was capable of treating initially discontinuous concentration fields with a maximum solid volume concentration of 0.5 and a solid-to-fluid density ratio of 4.
Abstract
This work extends a multi-phase mixing model framework designed for a Smoothed Particle Hydrodynamics context. Specifically, we propose a higher-order variation using the [...]
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Discrete Element Method to simulate the thermo-mechanical behavior of plasma-sprayed thermal barrier coatings during a thermal cycle
I. Bensemmane, W. Leclerc, N. Ferguen, M. Guessama

particles2023.

Abstract
Thermal Barrier Coatings (TBCs) are multilayer systems used in Ni-based superalloy components for gas turbine blades submitted to high temperatures resulting in the development of high thermal stresses. The intricacy of their microstructure coupled to severe environmental conditions lead to their premature failure according to complex mechanisms involving notably creep and Coefficient of Thermal Expansion (CTE) mismatch effects. This work aims to investigate the development of thermal residual stress within TBCs during a heating step using a numerical model based on Discrete Element Method (DEM). The suitability of such an approach is investigated in terms of stress field distribution in comparison to Finite Element Method (FEM). Results reveal the capability of the proposed DEM approach to simulate creep phenomenon in a TBC system under thermal loading and predict accurately thermal stresses leading to failure.
Abstract
Thermal Barrier Coatings (TBCs) are multilayer systems used in Ni-based superalloy components for gas turbine blades submitted to high temperatures resulting in the development [...]
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Particle-based Semi-resolved Coupling Model for the Simulation of Internal Erosion in soil structures
K. Tsuji, M. Asai, K. Kasama

particles2023.

Abstract
Internal erosion, caused by seepage flow inside the soil, accelerates soil failure during a natural disaster. Numerical simulation can be an effective tool to quantitatively evaluate the relationship between internal erosion and the instability of the ground as a whole. Internal erosion and multiphase flow simulation of fluid and granular materials with a particle size distribution require coupling simulations that can represent the interaction between particles and pore water and the movement of particles. There are two main types of coupling models: ”Resolved coupling model,” which can calculate detailed flow and fluid forces, and ”Unresolved coupling model,” which is based on empirical drag and seepage flow models. Previous studies have indicated that both models should be judged appropriately based on the ratio of particle-fluid spatial resolution. However, applying a resolved coupling model to the vast number of soil particles that make up the ground is impractical from a computational cost perspective, and empirical unresolved coupling model has difficulty in representing localized failures such as internal erosion. Therefore, developing a new coupling model that satisfies both computational accuracy and efficiency is desirable. In this study, we applied ISPH (Incompressible Smoothed Particle Hydrodynamics) for fluid analysis and DEM (Discrete Element Method) for soil particles to develop a fluid-soil coupling simulation model that can directly represent the movement of soil particles during the internal erosion process. Through numerical experiments using a particle layer with the vertical upward flow, we understand the limitations of the conventional coupling model and propose a new hybrid type of semi-resolved coupling model that combines these two models appropriately.
Abstract
Internal erosion, caused by seepage flow inside the soil, accelerates soil failure during a natural disaster. Numerical simulation can be an effective tool to quantitatively [...]
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PUBLIC HEALTH IN GERMANY BEFORE 1848: PRACTICE AND THEORY
D. Mikhel

RUSSIAN PRESIDENTIAL ACADEMY OF NATIONAL ECONOMY AND PUBLIC ADMINISTRATION (2023). 222

Abstract
The rise of public health care in Germany was part of a modernization process, the first product of which was the state. As part of the cameralist policy of encouraging population productivity, the dignitaries of Prussia and other German states began to establish special authorities responsible for the health and well-being of the population as early as the late seventeenth century. The 18th century saw a bureaucratization of health management methods, with district doctors (Kreisphysickus) as representatives in the field. They were entrusted with a wide range of administrative responsibilities, but their social status remained low. Some of the district doctors became known as the authors of treatises on medical police, presenting their views on the development of public health. Their theories, however, were far removed from actual practice. The situation began to change only after 1848, when political events in Germany prompted a new generation of physicians to vigorously demand political, social and medical reforms.
Abstract
The rise of public health care in Germany was part of a modernization process, the first product of which was the state. As part of the cameralist policy of encouraging population [...]
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PROBLEMS OF READINESS OF THE SECONDARY VOCATIONAL EDUCATION SYSTEM FOR THE GROWTH OF THE INCOMING POPULATION
E. Lomteva

RUSSIAN PRESIDENTIAL ACADEMY OF NATIONAL ECONOMY AND PUBLIC ADMINISTRATION (2023). 223

Abstract
Introduction. The relevance of the study of this problem is due to the growing burden on the secondary vocational education system, namely the increase in the number of graduates of 9th and 11th grades who choose this level of education after school. The purpose of the article was to study the problems, consequences and risks of the growth of the number of entrants to the secondary vocational education system. Methodology. The leading method of research was the analysis of statistical data in the field of vocational education, as well as a sociological study conducted by the Center for the Economics of Continuing Education of the RANEPA in August 2020 among 903 graduates of educational organizations of the secondary vocational education system, which revealed the main motives for young people to choose the next stage of education. The Results of the study are the conclusions that the secondary vocational education system is not currently ready for increased interest on the part of young people. The growing number of middle-level and skilled personnel entering training programmes is constrained by limited resources for secondary vocational education, which forces young people to enter professional educational organizations on a paid basis or choose other regions for admission. The author considered the factors limiting the possibility of the secondary vocational education system to the tendency to increase the number of people wishing to enter professional educational organizations and the associated risks. Conclusion. The materials presented in the article can be used by the executive authorities of the constituent entities of the Russian Federation to assess the dynamics of development indicators and evaluate the performance of the secondary vocational education system and educational organizations.
Abstract
Introduction. The relevance of the study of this problem is due to the growing burden on the secondary vocational education system, namely the increase in the number of graduates [...]
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NUMERICAL SIMULATION OF A LABORATORY-SCALE FREE FALL CONE PENETROMETER TEST IN MARINE CLAY WITH THE MATERIAL POINT METHOD
D. MOHAPATRA, M. SARESMA, J. VIRTASALO, W. SOŁOWSKI, D. Mohapatra

Debasis Mohapatra's personal collection (2023). 1

Abstract
This paper shows a numerical replication of a laboratory-scale free fall cone penetrometer test of marine clay. The numerical simulation involves large deformations and considers the destructuration of clay, strain rate effects, and non-linear material behaviour. The numerical simulation well replicates the laboratory experiment captured on a high-speed camera. The penetration process is replicated accurately in time, and the depth of the penetration corresponds to that obtained in an experiment. The simulation results indicate that the numerical framework implemented in Uintah software, consisting of an advanced soil model and the Generalized Interpolation Material Point Method, is well-suited for replication of the dynamic penetration process in soft and sensitive marine clay.
Abstract
This paper shows a numerical replication of a laboratory-scale free fall cone penetrometer test of marine clay. The numerical simulation involves large deformations and considers [...]
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Design of Graphical Symbols for Shape Transformations of 4D Printed Parts
E. Pei, C. Leung

SIM-AM2023.

Abstract
The term “4D Printing” (4DP) is defined as the ability for a part produced using an additive manufacture process to change its shape when activated by or exposed to one or more stimuli over time. This emerging technology offers unique advantages over conventional Additive Manufacturing (AM) by extending the three dimensions of space into the fourth dimension of time. 4DP parts can be programmed to actuate passively without the need for an external power source such as an electromechanical or other active system, thereby reducing the probability of failure and the complexity of components. This work attempts to address some of the challenges faced by the design engineer in a project team when producing technical documentation to specify the desired shape transformation of a 4DP part with a structured graphical representation at an appropriate level of abstraction. In this paper the requirements for a shape transforming 4DP part are represented as the allowable variation in dimensional size and tolerance in geometric form of the functionally critical features on the part for each function that the transformed shape serves. In this paper, the authors describe how the proposed standard to specify the desired shape transformations of a 4DP part could use graphical symbols in a structured specification by means of a Transformation Control Frame (TCF) to define the rules of transforming between shapes and a Bill of Transformations (BoT) to enumerate all the Transformation Control Frames (TCF) necessary to describe the intended sequence of shape transformations. To illustrate how the graphical symbols could be applied, a SMA actuated gripper is presented as a use-case.
Abstract
The term “4D Printing” (4DP) is defined as the ability for a part produced using an additive manufacture process to change its shape when activated by or exposed to one [...]
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Applications of Immersed Boundary Methods for Laser Powder Bed Fusion Additive Manufacturing
M. Carraturo

SIM-AM2023.

Abstract
In the present contribution, we propose an effective numerical thermal modeling solution for melt pool simulations in Laser-based Powder Bed Fusion of Metals processes. The proposed model employs an anisotropic conductivity to represent melt pool dynamics effectsin a homogeneous material model. The numerical implementation of the proposed physical model is first experimentally calibrated and then validated with respect to a series of melt pool measurements as acquired by using a short-wave infrared (SWIR) camera monitoring system.
Abstract
In the present contribution, we propose an effective numerical thermal modeling solution for melt pool simulations in Laser-based Powder Bed Fusion of Metals processes. The [...]
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Cellular Automata Simulation of Fully Equiaxed Microstructure Formation in Scalmalloy® during Additive Manufacturing with Adjustable Ring Mode Laser
M. Mohebbi, V. Ploshikhin

SIM-AM2023.

Abstract
We utilized an Adjustable Ring-Mode (ARM) laser to achieve an almost fully equiaxed microstructure in powder bed Fusion-laser beam Scalmalloy®. ARM laser-built specimens exhibited over 90% fine-grained material, while circular laser-built specimens yielded less than 50% fine-grained material, using the same laser power, speed, and hatch spacing. To gain insights into these interesting results, we employed a Cellular Automata (CA) solidification simulation, incorporating the nucleation role of L12 Al3(ScxZr1-x) precipitates through a particle-based nucleation model. The simulation was coupled with the corresponding temperature field derived from finite difference analyses of the circular and ARM laser beams. The simulation results revealed a significantly thicker precipitation zone (equiaxed grains) under the ARM laser compared to the circular beam, primarily attributed to reduced temperature and cooling rates. The excellent correlation between simulation and experimental results demonstrates promising potential for the predictive application of the developed model. It can be effectively utilized to optimize heat source modulation and process parameters, thereby enabling the adaptation of microstructure and mechanical properties
Abstract
We utilized an Adjustable Ring-Mode (ARM) laser to achieve an almost fully equiaxed microstructure in powder bed Fusion-laser beam Scalmalloy®. ARM laser-built specimens [...]
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The Effect of Geometrical Imperfections on the Mechanical Properties of Lattice Structures Produced by the Powder Bed Fusion (PBF) Process
K. Hamasaki, K. Ushijima

SIM-AM2023.

Abstract
In this paper, the effects of geometrical imperfections observed in a lattice structure fabricated by metal 3D printer on the compressive response were investigated by using FE simulation. Geometrical imperfections which are due to excessive heat transfer and the melting of unnecessary metal powder during the fabrication process was observed using a 3D X-Ray microscope (XRM) machine. Based on the observation, two types of geometrical imperfections (strut diameter deviation and the center-axis offset) were measured, and the quantities of these imperfections on the mechanical properties of lattice block were discussed. By introducing imperfections to the FE model, a likelihood of reduced mechanical properties can be potentially adverted. In addition, by comparing the amount of geometrical imperfections, the initial stiffness and plastic collapse strength in the models based on different strut diameters, we proposed appropriate manufacturing conditions for the lattice blocks that would minimize the reduction of their mechanical properties.
Abstract
In this paper, the effects of geometrical imperfections observed in a lattice structure fabricated by metal 3D printer on the compressive response were investigated by using [...]
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Numerical Investigation of Vibration Properties of Chiral Structures with Artifical Structural Anisotropy
S. Noguchi, K. Ushijima

SIM-AM2023.

Abstract
The dynamic vibration response of sandwich beams with an anti-tetra-chiral lattice as a lightweight sandwiched core have been studied by using a nonlinear finite element analysis (FEA). Since the anti-tetra-chiral structure has a weak shear stiffness, its vibration response is strongly affected by the shear deformation. In our calculation, a 3-point bending flexural test was conducted for calculating the effective shear stiffness as well as the effective Young’s modulus of the chiral core. The natural frequency of the sandwich beam has been calculated by FEA, and predicted by using the Rayleigh-Ritz method, assuming that the sandwich beam is composed of composite continuum materials with equivalent Young’s modulus and shear modulus. Moreover, the natural frequency and damping ration of the sandwich beam produced by a 3D printer bas been measured through a vibration test, and compared with numerical results in order to clarify the effectiveness of the chiral sandwich beam as a mechanical component.
Abstract
The dynamic vibration response of sandwich beams with an anti-tetra-chiral lattice as a lightweight sandwiched core have been studied by using a nonlinear finite element analysis [...]
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Towards neuronal network enhanced finite element simulations in additive manufacturing
C. Behrens, V. Ploshikhin

SIM-AM2023.
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Parametric Study of Directed Energy Deposition Of Duplex Stainless Steels To Optimize Ferrite-Austenite Phase Ratio And Residual Stresses
D. Weisz-Patrault

SIM-AM2023.

Abstract
Optimal material properties of duplex stainless steels generally require near 50-50 ferrite-austenite microstructures. The development of additive manufacturing of duplex steels is hindered by difficulty in controlling cooling conditions to ensure a balanced phase ratio. In addition, non-uniform phase distribution is usually observed. Thus, sufficiently fast part scale process simulations are interesting to optimize process parameters to better predict and control the temperature history during fabrication and therefore solid-state phase transitions. Furthermore, stresses should also be taken into account in the optimization of the phase field in order to avoid cracking, buckling or excessive distortions. Numerical results obtained from a fast modeling of directed energy deposition including thermal analysis, diffusion of alloying element to account for phase transitions, and stress computation are analyzed. On this basis, we investigate the effect on stresses of an optimized fabrication strategy designed to target uniform and balanced ferrite-austenite ratio with respect to a reference printing strategy
Abstract
Optimal material properties of duplex stainless steels generally require near 50-50 ferrite-austenite microstructures. The development of additive manufacturing of duplex [...]
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Closed-walled topology optimization of an additively manufactured motor bracket for an unmanned cargo aerial vehicle
J. Rieser, M. Zimmermann

SIM-AM2023.

Abstract
Compared to conventional intuition-based design, topology optimization (TO) provides considerable mass savings by clearing excess material from lightly loaded regions of a structural part. The remaining material may be distributed in a purely truss-like fashion, or in the form of a closed-walled design consisting of flat plates or curved shells with variable thickness. Unless buckling is of critical concern, closed-walled designs are in general more efficient than trusses which makes them particularly interesting for challenging applications in lightweight design. However, closed-walled designs obtained by topology optimization are still the exception rather than the rule. This paper investigates the applicability of the recently developed selective penalization approach to the design of a motor bracket for an unmanned aerial vehicle (UAV) to deliver defibrillators which is currently being developed by the HORYZN student initiative at the Technical University of Munich. The optimization results are closed walled designs as desired. A comparison to a truss-like design as well as to a conventional off-the-shelf motor bracket reveals that the closed-walled design even outperforms the topology optimized truss-like design by additional 3% in terms of stiffness-to-weight ratio. Moreover, it provides a streamlined housing protecting the motor cables and contributing to the reduction of aerodynamic drag at cruise speed. Another key finding of this case study is: Depending on the specific optimization problem, and a suitable build orientation provided, closed-walled designs may lower the amount of necessary sacrificial support structures or may even be almost self-supporting. For the closed-walled motor bracket design we found a reduction by more than 25% compared to the truss-like design. This did not require limiting the freedom of design by imposing any additional constraints. The motor bracket was successfully manufactured from aluminium alloy using laser powder bed fusion (LPBF) followed by removal of support structures and CNC machining of functional surfaces.
Abstract
Compared to conventional intuition-based design, topology optimization (TO) provides considerable mass savings by clearing excess material from lightly loaded regions of a [...]
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Incremental Viscoelasticity for 3D Concrete Printing: Finite Strain Modeling and Parametric Studies
B. NEDJAR, Z. Awada, J. Torrenti

SIM-AM2023.

Abstract
Within a 3D concrete printing process, concrete is still fresh and possible collapse may occur due to its own weight and lack of formwork. On the other hand, the mechanical characteristics of the material are continuously evolving due to hydration during curing. Withina predictive theory, the constitutive relation of the early age concrete is to be defined in rate form. In this contribution, and due to the soft nature of the problem at hand, a finite strainincremental viscoelastic modeling is adopted. A generalized Maxwell rheological model is used together with a Saint-Venant-like incremental elasticity. A parametric study is conducted on simulated slump-tests to highlight the abilities of the present framework. Clearly, the early age rheology and mechanical properties have a great impact on the buildability of the fresh concrete. A set of simulations is then given for the purpose of demonstration.
Abstract
Within a 3D concrete printing process, concrete is still fresh and possible collapse may occur due to its own weight and lack of formwork. On the other hand, the mechanical [...]
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Effect of Residual Stresses on the Mechanical Properties of TPMS Lattice Structures Manufactured Using 316L Stainless Steel
H. Mapari, H. Kruse, E. Escobar, A. Matei, J. Schleifenbaum

SIM-AM2023.

Abstract
In recent years, the use of Triply Periodic Minimal Surface (TPMS) lattice structures has gained popularity due to their advantages like high surface to volume ratio and their lightweight potential. Nowadays, TPMS lattice structures can be seen in many fields, including aerospace and medical applications, which can be fabricated using AM methods like Laser Powder Bed Fusion (PBF-LB/M) process. During the PBF-LB/M process, the transient emperature change is caused by the cyclic nature of the thermal load resulting in the accumulation of residual stresses (RS). These RS can cause dimensional inaccuracies, warpageand have a severe impact on the loading capacity and quality of the PBF-LB/M part. In this paper, the effect of RS on the mechanical properties of primitive and gyroid TPMS lattice structures of volume fraction 20%, 30% and 40% undergoing compression testing is studied using Finite Element Analysis (FEA) and experiments. The sequentially coupled thermomechanical finite element model is used to account for the RS accumulation and its effect on Young’s modulus, yield strength and Specific Energy Absorption (SEA).
Abstract
In recent years, the use of Triply Periodic Minimal Surface (TPMS) lattice structures has gained popularity due to their advantages like high surface to volume ratio and their [...]
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SAMPLE3D: A Versatile Numerical Tool for Investigating Texture and Grain Structure of Materials Processed by PBF Processes
Z. Yang, Y. Kuesters, R. Logvinov, M. Markl, C. Körner

SIM-AM2023.

Abstract
Powder Bed Fusion (PBF) not only enables the fabrication of metal parts with complex geometries in near-net-shape, but also offers the potential to tailor the microstructure and, consequently, the mechanical properties of the final product. In this contribution, we present our in-house developed simulation software SAMPLE3D (Simulation of Additive Manufacturing on the Powder scale using a Laser or Electron beam in 3D), which is designed specifically for simulating grain structure evolution during PBF processes. The core of SAMPLE3D is composed of a finite difference model and a cellular automaton model. The finite difference model is used to obtain the temperature field caused by an electron or laser beam. This temperature field is further used in the cellular automaton model to simulate grain structure development where grain selection as well as nucleation is considered. A range of information can be extracted from the simulation results, such as texture, grain morphology, and grain boundary arrangement. SAMPLE3D provides a way to get insight into the relationship between PBF process strategies and microstructures. SAMPLE3D has been employed to investigate the texture and grain structure evolution of various materials in different research projects.
Abstract
Powder Bed Fusion (PBF) not only enables the fabrication of metal parts with complex geometries in near-net-shape, but also offers the potential to tailor the microstructure [...]
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Multi-Scale Topology Optimization of Bodies with TPMS-based Lattice Structures and Mortar Contact Interfaces
N. Strömberg

SIM-AM2023.

Abstract
The combination of topology optimization, lattice structures and 3D printing has quickly emerged as a potential alternative for the design and manufacturing of lightweight components. However, the size of the building chamber restricts the size of this kind of lightweight designs. A possibility to overcome this limitation is to design assemblies of 3D printed lightweight components put together with contact interfaces. To design such an optimal lightweight assembly, the components should not be optimized separately, but the wholeassembly should be optimized simultaneously with all components including their unilateralcontact interfaces. This is the topic of the following work. In this paper, a framework formulti-scale topology optimization of assemblies of bodies with triply periodic minimal surfaces(TPMS)-based lattice structures and unilateral contact interfaces is developed and implementedin 3D. The contact interfaces are formulated for finite element bodies with non-matching meshesusing the mortar approach which in turn is solved by the augmented Lagrangian formulationand Newton’s method. The multi-scale topology optimization formulation, suggested in [1],is set up by defining two density variables for each finite element: one macro density variablegoverned by RAMP (Rational Approximation of Material Properties), and a micro densityvariable governed by representative orthotropic elastic properties obtained by numerical finiteelement homogenization of representative volume elements of the TPMS-based lattice structure. Thus, the macro density variable defines if an element should be treated as a void or be filled with lattice structure, and the micro density variable sets the local grading of the lattice. The potential energy of the system is maximized with respect to the design variables, in such manner no extra adjoint equation is needed for the sensitivity analysis. Both density variables are treated with a density filter, and the macro density variable is also passed a Heaviside filter. The final optimal assembly design is realized by transforming the optimal density fields to implicit surface-based geometries using a support vector machine and Shepard’s interpolation method, which then can be 3D printed as the corresponding stl-file obtained by applying the marching cube algorithm. The implemented framework is demonstrated for three-dimensional benchmark problems.
Abstract
The combination of topology optimization, lattice structures and 3D printing has quickly emerged as a potential alternative for the design and manufacturing of lightweight [...]
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Fluid Flow-Based Topology Optimization of Internal Channels of a LPBF-Manufactured Calibrator Side Lath
F. Gallego-Bordallo, H. Erdelyi, W. Six, I. Marco, B. Van Hooreweder

SIM-AM2023.

Abstract
In this study, a method is presented to design embedded cooling channels in an additively manufactured metal part. A fluid flow-based Topology Optimization (TO) methodology was applied on a specific industrial case study with thermal objectives and constraints. The resulting design was 3D-printed and assessed numerically. In addition, the cooling efficiency is compared against that of the original design, which is machined. This work was performed using commercial software tools Simcenter STAR-CCM+ to perform the thermal and fluid flow optimization and simulations; NX to generate a final geometry from optimization results and 3DXpert to assess part printability.
Abstract
In this study, a method is presented to design embedded cooling channels in an additively manufactured metal part. A fluid flow-based Topology Optimization (TO) methodology [...]
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Thermal and Mechanical calibration of multi-material DED AM process simulations on part-scale
J. Vroon, A. van der Eems, W. van der Brink

SIM-AM2023.

Abstract
Additive Manufacturing (AM) processes, such as Directed Energy Deposition (DED), offer great potential for producing complex and customized components. To optimize these processes, accurate simulations and numerical modeling techniques are essential. This paper presents a study on the thermal and mechanical calibration of DED AM process simulations on a part-scale. The research aims to develop a comprehensive finite element model that incorporates the multi-physics nature of the DED process, accurately predicting thermal behavior, internal stresses, and distortion of manufactured components. The calibration process involves experimental measurements and simulations using Abaqus software. The thermal calibration involves calibrating parameters such as emissivity, absorptivity, and convection coefficients, while the mechanical calibration focuses on plastic strain properties. Additionally, the study explores the simulation of multi-material prints and functionally graded materials. The results demonstrate that the models can accurately represent thermal and mechanical phenomena, with calibration of material properties playing a crucial role. The paper concludes with recommendations for further validation, including demonstrator prints and investigations into simulation parameters. This research contributes to advancing the understanding and application of DED AM simulations, enabling more accurate and reliable predictions for industrial applications.
Abstract
Additive Manufacturing (AM) processes, such as Directed Energy Deposition (DED), offer great potential for producing complex and customized components. To optimize these processes, [...]
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Simulation-Based Process Optimization Towards Homogeneous Ti6Al4V L-PBF Components
T. Koenis, M. Montero-Sistiaga, M. De Smit, E. Amsterdam

SIM-AM2023.

Abstract
In this study, macro-scale thermal simulation of the laser powder bed fusion (LPBF) process is employed to predict and limit geometry-induced overheating of complex Ti6Al4V components. First, the overheating effect is reproduced in tensile specimens. Overheating is found to increase the local oxygen content by almost 80% and lower the elongation at break by over 70% in overheated regions. By employing macro-scale thermal simulations, an automated routine is developed to efficiently optimize the L-PBF process to prevent local overheating. Variable interlayer wait times are numerically optimized to allow cooling of the material without adding manufacturing time where this is not required. In this way, local overheating can successfully be prevented resulting in a more homogeneous temperature distribution during the L-PBF process. This method was found to fully restore the mechanical properties in geometries prone to overheating, resulting in more homogeneous and predictable Ti6Al4V components.
Abstract
In this study, macro-scale thermal simulation of the laser powder bed fusion (LPBF) process is employed to predict and limit geometry-induced overheating of complex Ti6Al4V [...]
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Numerical model for the laser metal deposition additive manufacturing process: Multiphysics modeling and experimental validation
G. Dali

SIM-AM2023.

Abstract
Metallic Additive Manufacturing (AdM) technologies (3D printing) is rapidly spreading to a variety of industrial applications. In recent years, advances in AdM have gradually transformed the way in which manufactured products are designed and produced. It enables easy manufacturing of complex shaped parts with high performance, less material waste and short development cycle. Laser Metal Deposition (LMD) is one of the processes in this growing field. This process can produce high performance parts by the injection of powders into a melt-pool created by a laser heat source. However, the LMD is complex and several defects may appear during the printing process. In this context, numerical simulation could be a helpful tool to describe the involved physical phenomena and then to predict the impact of process parameters on the material state. Such numerical tool can predict the heat exchanges and the fluid flow within the molten pool enabling defect prediction and process optimization. In this work, a multi-physics numerical model of the LMD process, at a mesoscopic scale, (i.e. at the layer thickness scale) is developed to predict thermal cycles during fabrication, as well as the complex relationships between part construction and operating parameters. For this purpose, the finite element code COMSOL Multiphysics is used. The developed model takes into account fluid flow and heat transfer in the different phases (gas, substrate and melt pool). As a key feature, the developed model simulates the growth of the track using the generation of droplets when the powder flow is intercepted by the laser beam. Material addition, interface tracking, and strong topological changes are handled using the level set technique. The numerical results are compared to the experimental results for validation purposes. This validation includes the comparison between the predicted molten pool cross-section and measurements from macrographs and high-speed videos.
Abstract
Metallic Additive Manufacturing (AdM) technologies (3D printing) is rapidly spreading to a variety of industrial applications. In recent years, advances in AdM have gradually [...]
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Multiphysical modeling of soft-tissue stent interaction (Plenary Lecture)
S. Reese, K. Manjunatha, J. Shi, M. Sesa, M. Behr, F. Vogt

coupled2023.

Abstract
The efficacy of cardiological interventions, including the implantation of prostheses, is highly dependent on patient-specific immunohistology and can be enhanced with computational predictive tools. Therefore, an in silico replication of neointimal hyperplasia shall provide the necessary insights about the biochemical and cellular interactions within the vessel wall, and eventually address the risks of in-stent restenosis in a patient-specific manner. In this context, we set up a multiphysics framework considering key mediators of restenosis and couple them to a continuum mechanical vessel wall model. The governing set of coupled partial PDEs for the underlying mechanobiological system is solved via the finite element method and the results are compared to those obtained using a deep learning framework employing physics-informed neural networks (PINNs). Another interesting cardiological intervention-related problem is the maturation of tissue-engineered cardiovascular implants wherein the evolution of the collagen density affects the tissue’s mechanical behavior. The model we present allows us to predict the evolution of collagen density within textile-reinforced heart valves.
Abstract
The efficacy of cardiological interventions, including the implantation of prostheses, is highly dependent on patient-specific immunohistology and can be enhanced with computational [...]
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A coupled model for the formation of Atherosclerosis due to inflammation processes
P. Wriggers, M. Gierig, A. Haverich

coupled2023.

Abstract
Atherosclerosis is a disease in blood vessels that often results in plaque formation and lumen narrowing. It is an inflammatory response of the tissue caused by disruptions in the vessel wall nourishment. Blood vessels are nourished by nutrients originating from the blood of the lumen. In medium-sized and larger vessels, nutrients are additionally provided from outside through a network of capillaries called vasa vasorum. It has recently been hypothesized [1] that the root of atherosclerotic diseases is the malfunction of the vasa vasorum. This, so called outside-in-theory, is supported by a recently developed numerical model [2] accounting for the inflammation initiation in the adventitial layer of the blood vessel. Building on the previous findings, this presentation proposes an extended material model for atherosclerosis formation that is based on the outside-in-theory. Beside the description of growth kinematics and nutrient diffusion, the roles of monocytes, macrophages, foam cells, smooth muscle cells and collagen are accounted for in a nonlinear continuum mechanics setting. Cells are activated due to a lack of vessel wall nourishment and proliferate, migrate, differentiate and synthesize collagen, leading to the formation of a plaque. Numerical studies show that the onset of atherosclerosis can qualitatively be reproduced. Thus, the in silico model backs the new theory.
Abstract
Atherosclerosis is a disease in blood vessels that often results in plaque formation and lumen narrowing. It is an inflammatory response of the tissue caused by disruptions [...]
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Reduced-Order Models in Bayesian solvers for inverse problems
P. Diez, S. Zlotnik, A. Muixí, A. García-González

coupled2023.

Abstract
Challenging inverse problems aim at identifying large sets of parameters using data from different sources and diverse accuracy. This is the case of data assimilation for geophysical crust dynamics, were the number of parameters to identify amounts to thousands. In this context, Bayesian inverse solvers combined with Markov-Chain Monte Carlo (MCMC) strategies are an affordable strategy, accounting for the uncertainty of the input data and quantifying also uncertainty of the output. Despite the efficiency of the MCMC approach, the direct problem has to be evaluated an extremely large number of times, many (after the burn-in phase) with the input parameters lying in a narrow range. This is the ideal situation for Reduced-Order Models (ROM): many repeated queries to the model corresponding to parameters lying in a limited manifold. Thus, we aim at applying ROM to large-dimensional parametric forward problems. In this case, it is important optimising the dimensionality reduction technique inherent to the ROM strategy. For instance, Proper Orthogonal Decomposition (POD) is associated with a linear Principal Component Analysis (PCA). PCA is linear in the sense that assumes the reduceddimension manifold to be Euclidean. We explore using kernel PCA (kPCA) to further reduce the dimension, thus devising a kPOD approach. Different options to select physically inspired kernels, based on the knowledge of the problem under consideration, are discussed. Moreover, the computational strategy to explore the feature space (the reduced-dimensional space) is also discussed.
Abstract
Challenging inverse problems aim at identifying large sets of parameters using data from different sources and diverse accuracy. This is the case of data assimilation for [...]
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Model Order Reduction in the Parametrized Multi-Scale and Coupled Setting
K. Veroy-Grepl

coupled2023.
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A New Paradigm for Multiphysics Simulation: Its Initial Application to Fluid-Structure Interaction
K. Park, J. González

coupled2023.

Abstract
A new paradigm for simulating mulitipysics systems is presented with initial focus on FluidStructure Interaction (FSI). For each single-field governing equations adopting Lagrangian frame, a projection operator couples the coupled field without invoking interface Lagrange multipliers. For FSI problems where fluids are modeled by employing ALE kinematics, a physics-based interface equations are formulated as an independent set of third-field equations. This approach facilitates the connection of non-matching meshes and provides consistent dynamic equations of motion for the interface that can be integrated in parallel. The proposed simulation paradigm adopts stand-alone software modules for the fluid and the structure, which is coupled through a third interface system treating their interaction, which preserves the modularity of the singlediscipline software modules. The new FSI simulation paradigm is demonstrated as applied to several FSI benchmark examples, demonstrating its efficiency and accuracy. Extension of the proposed new multiphysics simulation paradigm to treat other multiplhysics problems are suggested.
Abstract
A new paradigm for simulating mulitipysics systems is presented with initial focus on FluidStructure Interaction (FSI). For each single-field governing equations adopting [...]
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CECM: A continuous empirical cubature method with application to the dimensional hyperreduction of parameterized finite element models
J. Hernández, J. Bravo, S. Parga

Computer Methods in Applied Mechanics and Engineering (2023). Vol. 418 (Part B), 116552

Abstract
We propose a method for finding optimal quadrature/cubature rules with positive weights for parameterized functions in 1D, 2D or 3D spatial domains. The method takes as starting point the values of the functions at the Gauss points of a finite element (FE) mesh of the spatial domain for a representative sample of input parameters, and then construct an elementwise continuous orthogonal basis for such functions using the truncated Singular Value Decomposition (SVD) along with element polynomial fitting. To avoid possible memory bottlenecks in computing the SVD, we propose a Sequential Randomized SVD (SRSVD) in which the matrix is provided in a column-partitioned format, and which uses randomization to accelerate the processing of each individual block. After computing the basis functions, the method determines an exact integration rule for such functions, featuring as many points as functions, and in which the points are selected among the Gauss points of the FE mesh. Finally, the desired optimal rule is obtained by an sparsification process in which the algorithm zeroes one weight at a time while readjusting the positions and weights of the remaining points so that the constraints of the problem are satisfied. We apply this methodology to multivariate polynomials in cartesian domains to demonstrate that the method is indeed able to produce optimal rules – i.e., Gauss product rules –, and to a 2-parameters, 3D sinusoidal–exponential function to illustrate the use of the SRSVD in scenarios in which the standard SVD cannot handle the operation because of memory limitations. Lastly, the fact that the method does not require the analytical expression of the integrand functions – just their values at the FE Gauss points – makes it suitable for dealing with the so-called hyperreduction of parameterized finite element models. We exemplify this by showing its performance in the derivation of low-dimensional surrogate models in the context of the multiscale FE method. The Matlab source codes of both the CECM and the SRSVD, along with the scripts for launching the numerical tests, are openly accessible in the public repositoryhttps://github.com/Rbravo555/CECM-continuous-empirical-cubature-method.
Abstract
We propose a method for finding optimal quadrature/cubature rules with positive weights for parameterized functions in 1D, 2D or 3D spatial domains. The method takes as starting [...]
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Empirical Interscale Finite Element Method (EIFEM) for modeling heterogeneous structures via localized hyperreduction
J. Hernández, A. Giuliano, E. Soudah

Computer Methods in Applied Mechanics and Engineering (2023). Vol. 418 (Part A), 116492

Abstract
This work proposes a special type of Finite Element (FE) technology – the Empirical Interscale FE method – for modeling heterogeneous structures in the small strain regime, for both dynamic and static analyses. The method combines a domain decomposition framework, where interface conditions are established through “fictitious” frames, with dimensional hyperreduction at subdomain level. Similar to other multiscale FE methods, the structure is assumed to be partitioned into coarse-scale elements, each of these elements is equipped with a fine-scale subgrid, and the displacements of the boundaries of the coarse-scale elements are described by standard polynomial FE shape functions. The distinguishing feature of the proposed method is the employed “interscale” variational formulation, which directly relates coarse-scale nodal internal forces with fine-scale stresses, thereby avoiding the typical nested local/global problems that appear, in the nonlinear regime, in other multiscale methods. This distinctive feature, along with hyperreduction schemes for nodal internal and external body forces , greatly facilitate the implementation of the proposed formulation in existing FE codes for solid elements. Indeed, one only has to change the location and weights of the integration points, and to replace a few polynomial-based FE matrices with “empirical” operators, i.e., derived from the information obtained in appropriately chosen computational experiments. We demonstrate that the elements resulting from this formulation are not afflicted by volumetric locking when dealing with nearly-incompressible materials, and that they can handle non-matching fine-scale grids as well as curved structures. Last but not least, we show that, for periodic structures, this method converges upon mesh refinement to the solution delivered by classical first-order computational homogenization. Thus, although the method does not presuppose scale separation, it can represent solutions in this limiting case by taking sufficiently small coarse-scale elements.
Abstract
This work proposes a special type of Finite Element (FE) technology – the Empirical Interscale FE method – for modeling heterogeneous structures in the small strain [...]
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Experiment and SHM on the membrane structure of Shanghai Kunshan Football Stadium
Q. Zhang, Y. Huang, G. Zhang

membranes2023.
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Form-finding of lightweight tension-compression structures with equilibrium-based graphical methods
P. D'Acunto

membranes2023.
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50 Years of Form Finding by the Force Density Method
K. Bletzinger

membranes2023.
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Thinking to close the loop in membrane architecture
C. Monticelli

membranes2023.
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The Evolution in the Design Tools for Membrane Structures
P. Beccarelli

membranes2023.
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Progressive Damage in thin 2D Woven CFRP Laminates due to Stress Concentrations at Free Edges and Notches
L. Heinzlmeier, S. Siberer, C. Kralovec, M. Schagerl, T. Wolfsgruber

composites2023.

Abstract
Stress concentrations are present at cut-outs, notches, and generally at free edges in woven CFRP structures. Under cyclic loading, damage initiates from these stress raisers and progresses into the laminate, leading to strength reduction and structural failure. The present contribution provides a literature review summarizing analytical, experimental and numerical investigations regarding damage initiation and propagation in the presence of free edges and at notches in thin plain-woven 2D CFRP laminates. For free edges, initiation of damage is given as interlaminar matrix cracking. Modelling approaches for the progression by cohesive zone models or linear-elastic fracture mechanics are summarized. Recent advances using image correlation and numerical modelling are presented. In terms of notches, a brief survey of relevant literature is given, followed by a more detailed treatment of the damage progression originating from a circular hole. Additionally, the shortcomings of standard specimens with holes for fatigue damage progression investigations are addressed, since both mechanisms, damage from the free edge and the hole, interact. Latest research to uniquely identify the damage emanating from the hole is presented
Abstract
Stress concentrations are present at cut-outs, notches, and generally at free edges in woven CFRP structures. Under cyclic loading, damage initiates from these stress raisers [...]
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Investigation into the Manufacture of Hybrid Wear Resistant Forging Tools using Tailored Forming Technology
M. Till

composites2023.

Abstract
Forging tools that are subject to high thermo-mechanical loads require a correspondingly high heat resistance, hardness and ductility to prevent undesirable failure patterns due to wear, plastic deformation and crack formation. These properties are mainly required in the layer of the tool engraving close to the surface, as this area is exposed to the highest loads due to the contact with the hot workpiece. With the heat transfer from the workpiece to the tool, a cyclic tempering process of the tool material often occurs in this area, resulting in a decrease in wear resistance. Diffusion treatments of the tool surface, such as additional nitriding, cannot provide sufficient protection in thermally highly stressed tool areas, as the heat-affected zone in these areas extends beyond the surface modification. As a result, a tempered layer forms under the nitrided layer, on which it can slide off or break as a result of the high process loads and the wear protection is lost. The use of nickel-based alloys promises an improvement in service life due to their high specific heat. However, these alloys are much more expensive than hot-work tool steels and are more difficult to machine, which has a negative effect on the economic use as a die material. Furthermore, nickel-based alloys do not have the high strength of steel that is often required in the base material that is subject to low thermal loads. To reduce the material usage of nickel-based alloys, but to fully take advantage of their positive properties, the suitability of the Tailored Forming concept in thermo-mechanically highly stressed areas were investigated within the scope of this research. For this reason, hybrid forging tool inserts with a base material of hot-work tool steel and a protective nickel-based alloy surface layer were produced. The hybrid tools are manufactured through a process combination of rotatory friction welding and die forging. The surface enlargement as a result of the forming process is to be used specifically to protect the relevant tool areas with a layer of nickel-based alloy and at the same time minimize the use of the expensive material. The effects of the thermo mechanical treatments occurring in the joining zone were examined and the potential of the technology was investigated
Abstract
Forging tools that are subject to high thermo-mechanical loads require a correspondingly high heat resistance, hardness and ductility to prevent undesirable failure patterns [...]
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Evaluation of Bend-Twist Coupling in Shape Memory Alloy Integrated Fiber Rubber Composites
A. Annadata, A. Endesfelder, M. Koenigsdorf, J. Mersch, T. Gereke, M. Zimmernann, C. Cherif

composites2023.

Abstract
Advancements in textile technologies such as the integration of wire shaped Shape Memory Alloys (SMAs) on to the fabric with the help of Tailored-Fiber-Placement (TFP) method, and weft insertion of SMAs during manufacturing of textiles using knitting machines are helping to create composites capable of bending deformations without any external loads. These advancements laid the foundations for versatile applications especially in soft robotics. One such application is Interactive Fiber Rubber Composites (IFRC). The aim of this project is to evaluate the bend-twist coupling in the IFRC. The SMA reinforced composite is made of polydimethylsiloxane (PDMS) and has two layers of glass fibers stacked upon one another and joined with the help of TFP machine. This work focuses on the simulation of this approach in ANSYS with the Woodworth & Kaliske material model for SMA. The important feature of this model is that the shape memory effect can be achieved for different profiles of SMA, thus eliminating the necessity for a pre-stretch in contrast to the built-in model. The experimental values are evaluated from Multi-DIC technique, which is capable of determining deformations with respect to all directions. A comparative study with simulation and experimental results of the deformation and twisting angles is carried out. The derived conclusions will be helpful in obtaining and evaluating 3D spatial movements in IFRC structures with multiple joints in the future projects
Abstract
Advancements in textile technologies such as the integration of wire shaped Shape Memory Alloys (SMAs) on to the fabric with the help of Tailored-Fiber-Placement (TFP) method, [...]
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Analysis of Cure Behaviour Uncertainties in Thermoset Composite Parts using Particle Filter
A. Balaji, C. Sbarufatti, D. Dumas, O. Pierard, F. Cadini

composites2023.

Abstract
Process-induced deformations result from internal residual stress caused by the anisotropic properties of thermoset composite parts. The study’s focus is diagnosing the polymerization process, or curing, and considering how uncertainties in boundary conditions affect cure kinetics. This is achieved through a Particle Filter approach, utilizing a Bayesian framework. This framework recursively estimates the evolving cure state’s posterior distribution based on observed measurements from Differential Calorimetry Scanning tests and thermocouples. The algorithm simultaneously estimates the cure state parameters and predicts part temperature and process-induced deformations, which are closely tied to cure behaviour. This is accomplished using diffusion cure kinetics and analytical deformation models. Furthermore, it introduces an augmented cure state formulation to address uncertainties in cure boundary conditions, which conventional models overlook. The developed stochastic approach adeptly captures uncertainties related to cure evolution while providing comparable deformation predictions with minimal computational costs and memory usage. Experimental measurements of process-induced deformations in C-shaped thermosetting parts, made of unidirectional 8552/AS4 fibres and cured following the Manufacturing Recommended Curing Cycle, are validated using the developed algorithm. After validation, the proposed model is employed to predict outcomes, which are then utilized to determine the optimal curing cycle using a Genetic Algorithm.
Abstract
Process-induced deformations result from internal residual stress caused by the anisotropic properties of thermoset composite parts. The study’s focus is diagnosing the [...]
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Numerical Simulation of the Fatigue Damage Growth in Unidirectional Composites based on Fibre-Matrix Debonding
A. Seidel, B. Sørensen, K. Drechsler

composites2023.

Abstract
A methodology for investigating the micromechanical fatigue behaviour of unidirectional composites based on fibre-matrix debonding is developed. The fatigue damage mechanism is based on the progressive failure of fibres caused by debond crack tip stress fields resulting from fibre breaks in previous load cycles. The methodology combines an analytical model to describe the debond crack initiation and growth with a numerical finite element model to calculate resulting stresses. The methodology is applied on a two-fibre model composite. It can qualitatively predict the stress development within the simulation domain as well as the mechanism of a debond crack tip stress field triggering a break in a neighbouring fibre. Both is consistent with microscale observations in the literature.
Abstract
A methodology for investigating the micromechanical fatigue behaviour of unidirectional composites based on fibre-matrix debonding is developed. The fatigue damage mechanism [...]
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Micromechanical Homogenization Methods of Short Glass Fiber-reinforced Injection-molded Bio-based Composite Material
O. Schwahofer, K. Dreschler, F. Otero, P. Camanho

composites2023.

Abstract
Herein, microscale approaches were explored to determine the homogenized properties of short fibre reinforced polymer material. The analytical homogenization follows the shear lag principle to approximate elastic modulus in the case of longitudinally oriented short fibres. For the finite element-based homogenization, a periodic 3D representative volume element of the composite is constructed to apply forward numerical homogenization. This unit cell is discretized by tetrahedral 3D finite elements resulting in a periodic mesh. An effective spring element method was further developed to homogenize the properties of short fibre-reinforced material. The reduced order spring method predicted the elastic properties almost equally to the finite element-based homogenization. A novel bio-based polyamide matrix with 40% glass fibre content and a traditional polyamide with 30% glass fibre reinforcement serve for the application and validation of the developed micromechanical methods. An additional effectivity parameter must be considered to capture the manufacturing imperfections of the injection molding process. This parameter can be calibrated based on experimental data from tensile testing. The developed numerical frameworks show good potential for extensions to more advanced modelling of the composite, such as nonlinear behaviour or failure mechanism.
Abstract
Herein, microscale approaches were explored to determine the homogenized properties of short fibre reinforced polymer material. The analytical homogenization follows the shear [...]
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Impact damage modelling in composite laminates – numerical implementation of a strain rate dependent damage model
D. Ivančević, J. Ratkovic

composites2023.

Abstract
In this work, a numerical methodology for simulation of impact damage in laminated CFRP structures has been developed and implemented into the Abaqus/Explicit software. The methodology is based on the recent insights into the mechanical behaviour of CFRP materials at various strain rates. Failure initiation is modelled using the failure theory that was introduced in Coles et al. (2019). This approach has been modified to include the strain rate effects according to work presented in Raimondo et al. (2012) and to account for the mesh objectivity of the damage process in this work. The model has been implemented into Abaqus/Explicit using the user material subroutine VUMAT and details of the implementation are discussed in the work. The model has been applied to the simulation of two impact simulations demonstrating that the damage modes of the composite plate, as well as damage scope and displacement fields, have been simulated accurately. The methodology has been previously developed for application in unidirectional composite plates, whereas this work and current research phase focus on woven composites. Additionally, only the in-plane failure modes are currently considered whereas the out-of-plane damage modes will be investigated in the future research.
Abstract
In this work, a numerical methodology for simulation of impact damage in laminated CFRP structures has been developed and implemented into the Abaqus/Explicit software. The [...]
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