Documents published in 2022 : Scipedia

Model-Free Data-Driven Computing: Theory and Practice
M. Ortiz

complas2021.
- 9
- read
Numerical modeling of additive manufacturing: thermomechanical aspects
M. Bellet

complas2021.
- 12
- read
Data-driven based modulus prediction of cancellous bone and 3D printing for defect repair in clinic treatment
Z. Zhuang

complas2021.
- 8
- read
Data-driven mechanics – interesting aspects in the modelling of inelastic behaviour
S. Reese

complas2021.
- 13
- read
New advances for evolving meshes/discretization methods in 3D large deformation problems. Application to metal forming, wear, crack propagation and fluid-structure interactions using FEM, DEM and PFEM
J. Ponthot

complas2021.
- 11
- read
Hierarchical Deep Learning Neural Network (HiDeNN): an Artificial Intelligence (AI) Framework for Computational Plasticity
W. Liu

complas2021.
- 9
- read
A data-driven computation approach for history-dependent materials
P. Ladevèze

complas2021.
- 9
- read
Recent advances in FEMs and MPMs for Disaster Simulations
K. Terada

complas2021.
- 9
- read
Towards Computational Multiscale Shock-Absorbing Metamaterial Design: From the Upper-Scale to the Low-Scale
X. Oliver

complas2021.
- 8
- read
Computational multiscale analysis of mechanical and dynamical metamaterials
M. Geers

complas2021.
- 11
- read
FEA and IGA in Nonlinear Computational Mechanics
T. Hughes

complas2021.
- 9
- read
Computational Plasticity based on the Virtual Element Method
P. Wriggers

complas2021.
- 18
- read
Effect of cutting conditions on surface roughness of machined parts in CO2 laser cutting of pure titanium
I. Chaudhry, M. Boujelbene, A. Boudjemline

Materials Today: Proceedings (2021).

Abstract
Titanium (Ti) and its alloys machining has been a long standing issue in the manufacturing industry. The extraordinary Ti machining costs restrict its used in the specialised applications. To achieve improved surface quality, researchers are working tirelessly to optimize various cutting parameters. In this study, high-power CO
Abstract
Titanium (Ti) and its alloys machining has been a long standing issue in the manufacturing industry. The extraordinary Ti machining costs restrict its used in the specialised [...]
- 6
- read
Minimization of completion time variance in flowshops using genetic algorithms
I. Chaudhry, I. Elbadawi, A. Rafique, A. Boudjemline, M. Boujelbene, M. Usman, M. Aichouni

Rev. int. métodos numér. cálc. diseño ing. (2022). Vol. 38, (2), 22

Abstract
The majority of the flowshop scheduling literature focuses on regular performance measures like makespan, flowtime etc. In this paper a flowshop scheduling problem is addressed where the objective is to minimize completion time variance (CTV). CTV is a non-regular performance measure that is closely related to just-in-time philosophy. A Microsoft Excel spreadsheet-based genetic algorithm (GA) is proposed to solve the problem. The proposed GA methodology is domain-independent and general purpose. The flowshop model is developed in the spreadsheet environment using the built-in formulae and function. Addition of jobs and machines can be catered for without the change in the basic GA routine and minimal change to the spreadsheet model. The proposed methodology offers an easy to handle framework whereby the practitioners can implement a heuristic-based optimization tool with the need for advanced programming tools. The performance of the proposed methodology is compared to previous studies for benchmark problems taken from the literature. Simulation experiments demonstrate that the proposed methodology solves the benchmark problems efficiently and effectively with a reasonable accuracy. The solutions are comparable to previous studies both in terms of computational time and solution quality.
Abstract
The majority of the flowshop scheduling literature focuses on regular performance measures like makespan, flowtime etc. In this paper a flowshop scheduling problem is addressed [...]
- 125
- read
Analysis of PTS fracture loading of NR RPV
G. Galik, V. Kutis, J. Paulech, V. Goga

complas2021.

Abstract
The article describes a multistage modelling methodology proposed by the author for the modelling of emergency core cooling processes. The methodology is based on the best practice guidelines presented by the IAEA, it is applied to a specific scenario of emergency core cooling during a loss of coolant accident[1] with an effective break diameter of 20mm. A 3D thermohydraulic analysis was performed as the first step in the solution process, where the transient changes in the pressure, velocity and temperature fields within the reactor pressure vessel were studied [2]. The primary knowledge learned when processing the results of the first step, was the presence of an oscillating cold coolant stripe in close proximity to the pressure vessel wall. The next step in the methodology consisted of a three-dimensional thermo_x0002_mechanical analysis of the reactor pressure vessel [3]. In this step, pressure thermal shock induced critical zones of mechanical loading were identified and the influence of the oscillatory character of the cold stripe on the pressure vessel was studied. The last step of the methodology consisted of a fracture mechanics analysis of postulated defects during the pressure thermal shock. Acquired results from the final step shown, that the postulated defects’ sensitivity to the oscillatory nature of the cold stripe is highly dependent on the postulated defect’s orientation.
Abstract
The article describes a multistage modelling methodology proposed by the author for the modelling of emergency core cooling processes. The methodology is based on the best [...]
- 9
- read
On the Development of Dataset Supported Strategies for the Constitutive Parameters Identification of Metal Sheets
P. Prates, A. Pereira, J. Fernandes, N. Sakharova

complas2021.

Abstract
This contribution explores the viability of using numerical simulation datasets populated with cruciform tensile test results to identify constitutive parameters that describe the plastic behaviour of metallic sheets.
Abstract
This contribution explores the viability of using numerical simulation datasets populated with cruciform tensile test results to identify constitutive parameters that describe [...]
- 37
- read
Influence of rate dependent plasticity on a sheet metal bending process
C. Reisinger, C. Zehetner, H. Irschik, M. Krommer, W. Kunze

complas2021.

Abstract
The high demands on precision and quality of industrial sheet metal forming processes are increasing steadily. Therefore, more and more effects concerning the machines but also the material behaviour of the workpiece must be considered. Here, we consider an automatic panel bender of Salvagnini Maschinenbau GmbH. In this application, it turned out that the speed of bending is a relevant influence factor. Goal of this work is to estimate the influence of strain rate on bending forces and the shape of the bent profile.
Abstract
The high demands on precision and quality of industrial sheet metal forming processes are increasing steadily. Therefore, more and more effects concerning the machines but [...]
- 17
- read
Localisation of plastic deformation in stretching plates: microstructure effects
J. Dequiedt, C. Denoual

complas2021.

Abstract
The incidence of microstructural characteristics on the localization of plastic deformation in stretching plates in the form of necking was investigated by performing polycrystal plasticity simulations: crystal aggregates were generated by a Voronoї tessellation algorithm and crystal orientations were randomly distributed among the grains. The most outstanding results of this analysis, detailed in [1], are presented here. During dynamic extension, a transition is displayed between an initial grain scale strain organization towards the development of much larger patterns and a final stage during which one or a few localization zones develop drastically. The influence of the initial strain distribution on the final necking framework is enhanced when the number of grains in the plate thickness is reduced or the loading rate is moderate. Additionally, the sensitivity of the different stages of the localization process to texture has been highlighted: the co-existence of both favorably and unfavorably oriented grains raises the initial strain heterogeneity and triggers macroscopic localization at shorter times.
Abstract
The incidence of microstructural characteristics on the localization of plastic deformation in stretching plates in the form of necking was investigated by performing polycrystal [...]
- 12
- read
Modeling of austenitic TRIP-steels at small scales -- mean-field homogenization and simulation of oligo-crystals
S. Prüger, B. Kiefer

complas2021.

Abstract
A finite deformation mean-field homogenization approach is proposed based on an extended Mori-Tanaka scheme that incorporates additional eigenvelocity gradients associated with microstructural changes in austenitic steels such as twinning or solid-solid phase transformation. The deformation of the individual phases is described by a finite strain, hyperelastic and single crystal plasticity model, which is fully anisotropic and captures strong mutual interactions of individual slip systems. The resulting mean-field model is employed in the simulation of homogeneous deformation states with a prescribed microstructure evolution at the material point level, where a strong interaction between phase transformation and plasticity is observed in the individual phases.
Abstract
A finite deformation mean-field homogenization approach is proposed based on an extended Mori-Tanaka scheme that incorporates additional eigenvelocity gradients associated [...]
- 14
- read
New results in 3D-mesomechanical coupled analysis of external sulphate attack in concrete
C. Biscaro, A. Martínez, A. Pérez, C. López, G. Xotta

complas2021.

Abstract
External Sulphate Attack (ESA) is one of the main degradation processes affecting concrete structures. It takes place when the concrete is in an environment rich in sulphate ions and with a high humidity index. Once it has penetrated the concrete, sulphate undergoes chemical reactions that lead to the precipitation of expansive ettringite crystals that cause volumetric expansions of the cement paste/mortar, eventually leading to cracking and damage. The FE analysis is undertaken by representing concrete as composed by aggregate pieces inserted in a cement/mortar matrix. Zero-thickness interface elements are pre-inserted to represent potential fractures along all aggregate-matrix as well as along some selected matrix-matrix element contacts. A fracture-based non-linear constitutive law proposed by Carol et al. (1997) and later developed by Caballero et al. (2006) is used for the interface elements. Concerning the reactive transport problem, the model follows the initial work by Tixier and Mobasher (2003), which was introduced in a mesomechanical analysis with interfaces by Idiart et al. (2011) in 2D, and later in 3D (but no coupling) by Pérez et al (2017). In the present paper, the effects of the coupling between mechanical and diffusion/reaction in 3D, due to the cubic law of the interface diffusivity, are demonstrated. The new results obtained confirm that, also in 3D, penetration of ions, expansive reactions as well as subsequent cracking and degradation, all take place much faster when the coupling effect due to the open interfaces is introduced.
Abstract
External Sulphate Attack (ESA) is one of the main degradation processes affecting concrete structures. It takes place when the concrete is in an environment rich in sulphate [...]
- 14
- read
Homogenization of mesoscale discrete model for poroelasticity
J. Eliáš, G. Cusatis

complas2021.

Abstract
Biot's theory of coupled mechanical-transport behavior of porous materials is applied in the framework of discrete mesoscale modeling. The contribution presents asymptotic expansion homogenization of the discrete poromechanical model. The macroscale becomes homogeneous and continuous and contains all the coupling effects. In contrast, the microscale is discrete and completely decoupled, separate representative volume elements (RVEs) appear for mechanical and mass transport problems. Linear elastic material behavior is assumed, therefore response of the RVEs can be pre-computed in advance and used repetitively at integration points of the macroscopic model.
Abstract
Biot's theory of coupled mechanical-transport behavior of porous materials is applied in the framework of discrete mesoscale modeling. The contribution presents asymptotic [...]
- 6
- read
Numerical investigation of load sequence effect and energy dissipation in concrete due to compressive fatigue loading using the new microplane fatigue model MS1
M. Aguilar, A. Baktheer, R. Chudoba

complas2021.

Abstract
Modeling the fatigue behavior of concrete is a challenging task that has attracted the interest of researchers during the last decades. A new formulation of a microplane fatigue model denoted as MS1 introduced by the authors is employed. It aims to capture the basic inelastic mechanisms that are driving the tri-axial stress redistribution within a material zone during the fatigue damage process in concrete. In order to do so, the fatigue damage evolution is linked to a measure of the cumulative inelastic shear strain, reflecting the accumulation of fatigue damage owing to internal shear/sliding between aggregates at subcritical load levels. In the first place, numerical studies are presented, in which the elementary interface behavior and dissipation mechanisms are evaluated. Later on, an evaluation of the en ergy dissipation of experimental tests in terms of their hysteretic loops is displayed. This approach is called into question as available experimental data strongly suggests that this method underestimates the actual amount of energy being dissipated. The microplane material model MS1, which is able to reproduce the concrete behavior under monotonic, cyclic, and fatigue loading with consistent sets of material parameters, has been employed for evaluating the contributions of the different dissipative mechanisms for different load ing scenarios. Further studies assessing the ability of the model to reproduce the sequence effect for fatigue loading with varying amplitudes in terms of an energetic-based approach are presented.
Abstract
Modeling the fatigue behavior of concrete is a challenging task that has attracted the interest of researchers during the last decades. A new formulation of a microplane fatigue [...]
- 16
- read
Homogenization based two-scale modelling of fluid-saturated porous media with self-contact and flow in micropores
E. Rohan, J. Heczko

complas2021.

Abstract
The contribution is devoted to the numerical modelling of the homogenized fluid-saturated porous media subject to loads which, at the pore level, induce unilateral self-contact. The initial microstructure is periodic, being generated by a representative cell consisting of elastic skeleton and a rigid inclusion which is anchored in the skeleton on a part of its pore surface. The unilateral frictionless contact interaction is considered between the inclusion and the elastic skeleton on matching surfaces. Depending on the deformation due to applied macroscopic loads, the self-contact interaction alters the one between the solid and fluid phases. Both the disconnected and connected porosities are treated; in the latter case, quasistatic fluid flow is described by the Stokes model. A homogenized model is derived using the periodic unfolding and the method of oscillating test functions. The macroscopic model attains the form of a nonlinear Biot continuum, whereby the Darcy flow model governs the fluid redistribution. We propose an efficient algorithm for two-scale computational analysis with the numerical model obtained using the FE discretization of the homogenized model. For this, a sequential linearization is used which leads to consistent stiffness matrices of the macroscopic elasticity problem. At the local level, the contact problem attains the form of a nonsmooth equation which which is solved using the semi-smooth Newton method without any regularization, or a problem relaxation. Numerical examples of 2D deforming structures are presented.
Abstract
The contribution is devoted to the numerical modelling of the homogenized fluid-saturated porous media subject to loads which, at the pore level, induce unilateral self-contact. [...]
- 12
- read
Iterative strategies based on constitutive dissipation
L. Crusat, I. Carol

complas2021.

Abstract
FE formulation of solid mechanics problems typically require iterative strategies to solve the resulting nonlinear system. Basic strategies with prescribed load values, such as the Newton-Raphson method, are not valid in the presence of structural snap-back due to material or geometric non-linearity. In this case, the most common strategy is the cylindrical Arc-length method, which prescribes the norm of displacements as constraint, in order to obtain the load factor increment. However, because the constraint is quadratic, additional non-trivial criteria need to be introduced for choosing the appropriate solution, and the wrong choice may lead to potential spurious unloading among other problems. As a way to overcome these shortcomings, alternative methods have been proposed which are based on an energy dissipation constraint. Constitutive dissipation may be considered as an always increasing “time” parameter with the advantage that the corresponding constraint equation is always linear. Iterative methods based on a dissipation constraint can be found in the literature.]. But most of those formulations are based on specific constitutive models. In contrast, the present formulation is general in the sense that it is valid for any constitutive model, as long as the model subroutine provides, additional to the standard output, also the appropriate values of dissipation and dissipation derivatives. Some application examples in concrete structures with progressive fractures are also provided to illustrate the performance of the model proposed
Abstract
FE formulation of solid mechanics problems typically require iterative strategies to solve the resulting nonlinear system. Basic strategies with prescribed load values, such [...]
- 13
- read
Non-local numerical treatment of non-linear behavior by means of Helmholtz equation, with variable coefficients. Application to reinforced concrete structures.
R. Gontero, A. Millard, T. Vidal, A. Sellier, L. Sorelli

complas2021.

Abstract
Numerous work has been done with the aim of modeling the cracking of reinforced concrete (RC) structures. Among the recent methods proposed in the literature, the combination of reinforcement-concrete equilibrium combined with the linear behavior of the interface leads to a Helmholtz equation which takes account of the slip between the homogenized reinforcements and the concrete in presence of localized cracks [1][2]. In the case of large cracks openings, it is necessary to consider the non-linear behaviors of material and interfaces, such as the plasticity of reinforcements or the damage of the matrix-reinforcement interface. These phenomena induce variations of the coefficients in the Helmholtz equation, which leads to two levels of iterative procedures: one at a global level considering equilibrium of homogenized RC, and another one at a non-local level taking account of equilibrium between reinforcement and concrete. The implementation of a convergence criterion is then needed at each level. The goal of this paper is to describe the developments implemented in the Finite Element code Cast3m to perform non-local Helmholtz type calculations with non-constant coefficients. This method, using an acceleration method [3] is illustrated by the cases of reinforced concrete tie and beam, with homogenized reinforcements. References : [1] A. Sellier and A. Millard, “A homogenized formulation to account for sliding of non-meshed reinforcements during the cracking of brittle matrix composites: Application to reinforced concrete,” Eng. Fract. Mech., vol. 213, pp. 182–196, May 2019, doi: 10.1016/j.engfracmech.2019.04.008. [2] A. Sellier and A. Millard, “Traitement numérique non local de phénomènes physiques par l’équation d’Helmholtz : les effets d’échelle et le glissement renfort-matrice,” in Club Cast3M 2018, Paris, 2018, vol. 1, no. 1, pp. 12–18. Available: http://www-cast3m.cea.fr/html/ClubCast3m/club2018/Presentation_Sellier.pdf. [3] A. C. Aitken, “On the iterative solution of a system of linear equations.,” Proc. Roy. Sot. Edinburgh, pp. 52–60, 1950.
Abstract
Numerous work has been done with the aim of modeling the cracking of reinforced concrete (RC) structures. Among the recent methods proposed in the literature, the combination [...]
- 10
- read
Evaluation of four advanced plasticity and hypoplasticity models in simulating cyclic response of sands
J. Duque, M. Yang, W. Fuentes, D. Mašín, M. Taiebat

complas2021.

Abstract
Numerous constitutive models have been developed for the simulation of the response of granular soils under cyclic loading. While these models have succeeded in capturing certain aspects of the stress-strain response under a number of idealized loading paths, certain common limitations are encountered in simulating these and other paths, and also certain complex aspects of response. Examples of these include cyclic oedometeric stiffness, shear strain accumulation in cyclic mobility, cyclic liquefaction strength curves, among others. These limitations are rather crucial for the end-users. Discussing these limitations and providing the mechanisms to avoid them if possible, therefore, would be of great value for both applications and further developments. Relying on cyclic loading experimental test data of Karlsruhe fine sand, the present study conducts direct comparison between the experiments and the corresponding simulation results using four advanced constitutive models: two bounding surface elastoplasticity (Dafalias and Manzari 2004, Yang et al. 2021) and two hypoplasticity models (Niemunis and Herle 1997, Fuentes et al. 2020) – with the models in each category following a hierarchical order of complexity. The presented results elaborate on the specific capabilities and limitations of these advanced models in simulating several essential aspects of cyclic loading of sands.
Abstract
Numerous constitutive models have been developed for the simulation of the response of granular soils under cyclic loading. While these models have succeeded in capturing [...]
- 28
- read
Performance of different constitutive soil models: from element tests to the simulation of vibratory pile driving tests
J. Machacek, P. Staubach, M. Tafili, H. Zachert, T. Wichtmann

complas2021.

Abstract
The present study deals with the investigation of the applicability (by means of parameter calibration), robustness and prediction quality of advanced constitutive soil models for the numerical investigation of complex geotechnical problems. The range of available constitutive soil models extends from simple linear to time-dependent and hydromechanically coupled nonlinear modelling approaches. It is the user's task to select a constitutive model suitable for the problem at hand. This requires in-depth knowledge of the soil behaviour as well as the strengths and weaknesses of the available constitutive models, most of which have only been validated using element test simulations. The procedure from parameter calibration using laboratory tests under well-defined boundary conditions (element tests) to the simulation of boundary value problems is complex in many respects and is often not followed with advanced constitutive models due to the large number of parameters required and the necessary laboratory tests. In this paper, the prediction quality of three models, namely Hypoplasticity with Intergranular Strain, Sanisand and Hypoplasticity with Intergranular Strain Anisotropy is inspected. The investigation is carried out based on back-calculations of laboratory tests and a well-documented model test to evaluate their suitability in representing complex soil mechanical aspects, such as the material behaviour under cyclic loading, particularly pore pressure accumulation. The parameter calibration is performed both "manually" as well as with a specially developed automatic calibration software. Subsequently, model tests of vibratory pile driving in water-saturated sand are simulated using the previously calibrated parameters.
Abstract
The present study deals with the investigation of the applicability (by means of parameter calibration), robustness and prediction quality of advanced constitutive soil models [...]
- 42
- read
Evaluation of constitutive models in predicting ratcheting responses of a structure under thermo-mechanical loadings
J. Macedo, J. Bergheau, E. Feulvarch, H. Battie, O. Ancelet, A. Martin, S. Chapuliot

complas2021.

Abstract
empty
- 13
- read
Evaluation of Thermal Fatigue Life of Solder Joints in Electronic Devices Based on Stress and Strain Singularity Parameters
J. Liu

complas2021.

Abstract
It is well known that thermal fatigue easily occurs in the solder joints of electronic devices. In this study, we tried to evaluate thermal fatigue life of solder joints with the stress singularity parameters near the solder joint edges. Firstly, we made constitutive equations of the solder materials and confirmed its precision. Next, using finite element method (FEM) analyses, we calculated stress singularity parameters near the solder joint edges for power modules under the conditions of thermal cycle experiments and power cycle experiments. Finally, we made evaluation equations of thermal fatigue life for solder joints by connecting stress singularity parameters and experiment results with fatigue laws. It is clarified that the fatigue laws based on the stress singularity parameters is valid and useful for predicting the thermal fatigue life of solider joints in electronic devices.
Abstract
It is well known that thermal fatigue easily occurs in the solder joints of electronic devices. In this study, we tried to evaluate thermal fatigue life of solder joints with [...]
- 13
- read
Effect of the mean stress and the third invariant in the fatigue life assuming random loading
L. Malcher, R. Desmorat

complas2021.

Abstract
This work seeks to present a way to calculate the mean stress under conditions of random loading, as well as to show the effect of the third invariant of the deviatoric stress tensor in the prediction of fatigue life, under low and high number of cycles. Thus, it is proposed to use the so-called “exponential moving average scheme” to determine the mean stress, as well as a modification of the Gao yield criterion, to couple the effect of the mean value and use the third invariant to calculate the equivalent stress. The fatigue life is calculated based on incremental damage proposed by Lemaitre and modified by Malcher & Mamiya. The proposed approach shows that the reduction of the mean stress transient strongly affects the calculation of fatigue life. In addition, the calculation of the equivalent stress, taking into account the third invariant, mainly under shear loading conditions, also has a great influence on the life calculation. Finally, the proposal shows that incremental damage is a valid alternative for calculating fatigue life under random loading conditions.
Abstract
This work seeks to present a way to calculate the mean stress under conditions of random loading, as well as to show the effect of the third invariant of the deviatoric stress [...]
- 10
- read
Evaluation of a fracture indicator dependent on the normalized third invariant of the deviatoric stress tensor and equivalent plastic strain
L. DELGADO MORALES, L. Malcher

complas2021.

Abstract
This work presents a new fracture indicator, which incorporates the effects of the normalized third invariant of the deviatoric stress tensor and the equivalent plastic strain, in its formulation, The proposed indicator is also coupled with the post-processing step of the Gao constitutive model. The tests are applied to specimens manufactured from the AISI 4340 alloy in two heat treatment states. To compare the behavior of the material under different ductility conditions, numerical tests are performed for different stress states. The new fracture indicator presents satisfactory results when observing the forecast of the displacement in the fracture and the levels of reaction force, for the evaluated specimens used in the study.
Abstract
This work presents a new fracture indicator, which incorporates the effects of the normalized third invariant of the deviatoric stress tensor and the equivalent plastic strain, [...]
- 31
- read
Effects Of The Third Invariant On The Fatigue Life Assessment Of Metallic Materials in Low Cycle Conditions
L. Araújo, L. Malcher

complas2021.

Abstract
In this contribution, the effects of the third invariant on the fatigue life estimate for proportional and non-proportional loading paths of a J3-sensitive material.
- 7
- read
Analytical computational models for buckling and postbuckling of thin-walled stiffened composite panels
J. Schilling, C. Mittelstedt

complas2021.

Abstract
The loss of stability is critical regarding thin-walled composite structures which are widespread in weight critical applications. For the example of omega-stringer stiffened panels, the buckling and postbuckling behavior is investigated using closed-form analytical approximate solutions. They are derived based on energy methods and their focus lies on local stability behavior. Hereby, different load cases are included and the quality of the computational models is assessed in comparison to Levy solutions or finite element analyses.
Abstract
The loss of stability is critical regarding thin-walled composite structures which are widespread in weight critical applications. For the example of omega-stringer stiffened [...]
- 25
- read
A novel gradient-extended anisotropic two-surface damage-plasticity model for finite deformations.
H. Holthusen, T. Brepols, S. Reese, J. Simon

complas2021.

Abstract
A material model to deal with finite plasticity coupled with anisotropic damage will be presented. The presentation addresses mesh regularization problems and a novel approach for using gradient-extension in the context of damage. Since finite strains are considered, the strain measures chosen are logarithmic strains. To give the interested audience an idea of the behavior of the model, numerical examples are used for illustration.
Abstract
A material model to deal with finite plasticity coupled with anisotropic damage will be presented. The presentation addresses mesh regularization problems and a novel approach [...]
- 24
- read
On solving inconsistencies between different types of hardening models
S. Cooreman, S. Coppieters

complas2021.

Abstract
This paper presents the results of a numerical study in which different hardening models were compared. More specifically the following three hardening models were considered: isotropic hardening, combined isotropic-kinematic hardening and combined isotropic-kinematic-distortional hardening. Furthermore, all three models were used in combination with the same Hill 1948 yield surface. The isotropic hardening model was used to simulate tensile tests in different directions and a torsion test. It was then tried to reproduce the outcome of these simulations with the more advanced hardenings models. Therefore, the advanced models were calibrated based on one of the tests simulated with the isotropic hardening model. It was expected that different hardening models would predict the same behaviour for monotonous strain paths, but this is not the case for the models considered in this study. This seems to be an inconsistency complicating the calibration of more advanced constitutive models. In this paper it is shown that this inconsistency can be solved by scaling some parameters in the evolution equations of the kinematic and distortional hardening model with a ratio of two equivalent stresses.
Abstract
This paper presents the results of a numerical study in which different hardening models were compared. More specifically the following three hardening models were considered: [...]
- 9
- read
Increasing Precision of Batch Pipe Forming Method Using Burring and Ironing of Large Diameter Steel Pipe in FEM Analysis
T. Onizuka, K. Ogawa, S. Nishida

complas2021.

Abstract
This paper describes increasing precision of Batch Pipe Forming Method Using Burring and Ironing of Large Diameter Steel Pipe in FEM Analysis. Branch pipes are one of the components of the piping system in a factory that serves as a flow path for gases and fluids. The bifurcated tube is formed by burring as a typical molding technique. The burring process is to form a branch pipe by raising the peripheral portion of the prepared hole formed in the mother pipe. There is a problem that the cutting of the edge is required in the post process. Therefore, a branch pipe batch forming method has been developed in which burring processing that does not require a cutting step in the subsequent step is combined with ironing processing using FEM analysis. The purpose of this research is to improve the accuracy of FEM analysis in the branch pipe batch forming method using burring process and ironing process by cutting the material into a cylindrical shape and performing a compression test to obtain the deformation resistance of the actual material. The experimental results were compared with the analytical results and approximately good agreement was obtained.
Abstract
This paper describes increasing precision of Batch Pipe Forming Method Using Burring and Ironing of Large Diameter Steel Pipe in FEM Analysis. Branch pipes are one of the [...]
- 7
- read
Effects of Rotational Feed Emulating Four-Die Radial Forging on Forged Shape in Mandrel-Less Incremental Forging of Thick Circular Tube
T. Makiyama

complas2021.

Abstract
Tubes with variable wall thickness corresponded to their load distribution have advantages in weight-saving and resource-saving. Because of the advantages, those tubes are applied to bicycles frame and proposed to apply automotive driveshafts and railway axles. Those tubes should be tailor-made to reduce their weight effectively; therefore, flexible forming is suitable for their production. Most tubes with variable wall thickness are produced by radial forging, rotary swaging, cross-wedge rolling, and drawing. Those forming processes are relatively flexible; however, their dies and mandrels have to be prepared according to the tubes' size to be produced. The author proposed a new incremental forging to produce tubes with variable wall thickness. A circular tube is placed between two simple flat dies and held by a manipulator. No mandrels are used. Initially, the tube is compressed by the dies in the radial direction. Then, the tube is rotated by the manipulator around the longitudinal direction. After that, the compression and rotation are repeated alternately until an intended forging number. This incremental forging does not require preparing special dies and mandrels regardless of the tubes' size to be produced. One of the difficulties in the proposed incremental forging is to obtain the forming conditions to produce desired shapes because the tube freely deforms except a small area where the two flat dies are contacted. To examine the possibility of formability improvement, the author conducted finite element simulation using commercial software FORGE. As a fundamental research, the effects of rotational feed emulating four-die radial forging on forged shape ware clarified in this study.
Abstract
Tubes with variable wall thickness corresponded to their load distribution have advantages in weight-saving and resource-saving. Because of the advantages, those tubes are [...]
- 39
- read
3D Finite element model for prediction of the hot rolled strip crown and roll deformation.
A. Hamdam, M. Sano, M. Tsugeno, K. Ohara

complas2021.
- 8
- read
Fracture mechanics evaluation of V-bending die with a hole using parametric analysis system with coupling-matrix-free iterative s-version FEM
H. Suwa, Y. Yusa

complas2021.

Abstract
Operators of V-bending process have sometimes been injured because of broken piece of a die. To prevent this accident, a structure of the die that is tough to break is required. According to the previous study, introducing a hole in the V-bending die reduced stresses at the bottom of V-groove. Therefore, parametric study of a hole in a structure is necessary to find an appropriate design of the structure. However, parametric study of a structure with a hole using conventional FEM has difficulty in remeshing. Using coupling-matrix-free iterative s-version FEM, a mesh of the whole analysis domain and a mesh in the vicinity of the hole can be created separately as a global mesh and a local mesh, respectively. In this study, we proposed a parametric analysis system to analyze the die with a hole for V-bending process, and we evaluated the results in terms of fracture mechanics.
Abstract
Operators of V-bending process have sometimes been injured because of broken piece of a die. To prevent this accident, a structure of the die that is tough to break is required. [...]
- 132
- read
Finite element analysis of multi-stage deep drawing for forming deep rectangular case with high aspect ratio
S. Kajikawa, T. Takasan, T. Kuboki, K. Tamaoki, K. Onishi, A. Gunji, A. Yamauchi

complas2021.

Abstract
This paper presents investigations on multi-stage deep drawing for producing a flat and deep rectangular case, of which a cross section is high aspect ratio. Effects of a blank shape on a formability was investigated for preventing a local thinning and a large ear by using the finite element method (FEM) analysis. The multi-stage deep drawing was composed of four stages. The first and the second stage were deep drawing and redrawing process, and the third and the fourth stage were ironing process. The blank was the rectangle with the elliptic corners, and the longitudinal length and the elliptic corner length was changed. The local thinning and the ear were reduced by appropriately setting the longitudinal length and the elliptic corner length. In addition, the effect of the aspect ratio on the formability was small. Therefore, the optimized blank could be applied for forming the flat and deep rectangular case with various aspect ratio.
Abstract
This paper presents investigations on multi-stage deep drawing for producing a flat and deep rectangular case, of which a cross section is high aspect ratio. Effects of a [...]
- 15
- read
Fabrication of a ring groove on tube-inner surface by ironing from outer surface using displacement control of tube bottom end
I. Junki, K. Shohei, Y. Akira, G. Akira, O. Katsuyuki, K. Takashi

complas2021.

Abstract
This paper presents a improving method in a press forming for transferring convex shapes of an inner plug projection onto the tube-inner surface by applying outer-die ironing from the tube-outer surface. The previous study found that the concave shape was not perfectly formed and some “Non-filled-area” appeared around the upper and lower parts of the plug projection. This study tried to verify the effect of applying the reaction force on the tube-end surface by the finite element analysis (FEA) and experiment. The FEA showed the suitable amount of the reaction force and the optimum timing for reducing the force. The analytical results were verified by the experiment and the “Non-filled-area” was successfully reduced by the proposed method.
Abstract
This paper presents a improving method in a press forming for transferring convex shapes of an inner plug projection onto the tube-inner surface by applying outer-die ironing [...]
- 10
- read
Development of Twisting Method of Sheet Metal using Taper Roll
K. Avanish, T. Makiyama, S. Kajikawa, T. Kuboki

complas2021.

Abstract
Twisted shape of metal, like a propeller or screw, are usually manufactured by machining. However, machining processes generate many metal chips, resulting in yield loss. This paper proposed a new processing method called, “twist rolling”, which uses a pair of tapered rolls to obtain a continuous twisted shape. The effect of taper and skew angles on twist angle was investigated. The finite element analyses (FEA) and experiments were conducted for clarifying the effect of taper and skew angles. A commercial code, ELFEN, was used for the FEA, and a prototype machine was built for the verification using aluminium sheet metals. The FEA and experimental results were qualitatively in good agreement. The twist angle increased with the increase of the taper and skew angles. The sheet metal angle increased with the decrease of the sheet thickness. This study successfully verified the feasibility of the proposed method, “twist rolling”.
Abstract
Twisted shape of metal, like a propeller or screw, are usually manufactured by machining. However, machining processes generate many metal chips, resulting in yield loss. [...]
- 24
- read
FE-Analysis of end-notched beams and tenon joints – J-Integral versus cohesive zone modelling
T. Claus, W. Seim

complas2021.

Abstract
Improved wood-based materials, on the one hand, and computer-operated machinery, on the other, enable new types of timber-to-timber joints. Furthermore, new materials, such as laminated veneer lumber with cross-layers made of soft- or hardwood offer new possibilities regarding timber-to-timber connections like tenon and mortise. Experimental investigations have shown comparable failure mechanisms in mode I and mode II for tenon and multiple tenon joints, dovetail connections as well as for end-notched beams. In the field of fracture mechanics different concepts exists to describe the fracture behaviour such as the strain energy release rate, the stress intensity factors and the J-integral method for timber-to-timber joints. In this study the J-integral was determined around the crack tip in a finite element (FE) model in timber connections. The failure criterion was defined when the J-integral equals the energy release rate GcI+II in mixed mode of the timber material (Fig. 1a). A sensitivity analysis showed that the failure load Vc was not depending significantly on the initial crack length, the element size, the distance from the crack tip of the chosen contour Γ1 and the size of the chosen contour. In the next step, the model was validated on experimental test results of end-notched beams, tenon connections and multiple tenon connections (Fig. 1b). The experimental and numerical results showed very good accordance for different connection size and up to seven possible crack layers (Fig. 1c). Furthermore, a comparison between different fracture mechanic models with strain energy release rates and cohesive zones showed good performance of the new approach. Afterwards, the FE model using the J-integral failure criterion was used to perform a comprehensive study of geometrical parameters for end-notched beams and tenon connections. Finally, the dataset was used as a basis to develop a engineering model for three types of timber connections. The evaluation of the J-integral allows to determine the failure load due to crack initiation under a mixed mode loading in a linear elastic FE model with pre-defined cracks. The advantage of the J-integral method is the significant decrease of the computing time for extensive parameter studies. The model for end-notched beams, tenon joints and multiple tenon connections is insensitive to common variations of material properties as well as for the choice of the initial crack length. The application on timber structures under pure shear failure or tension failure perpendicular to the grain will be part of future research.
Abstract
Improved wood-based materials, on the one hand, and computer-operated machinery, on the other, enable new types of timber-to-timber joints. Furthermore, new materials, such [...]
- 20
- read
Digital twinning to predict the residual life of composite pressure vessels
N. Klebi, P. Kerfriden, B. Marchand, A. Thionnet

complas2021.

Abstract
This work is being carried out under the framework of a thesis at the center of materials Mines -Paristech. The goal of this thesis is to realize a first digital twinning for a composite structure which is the Composite Pressure Vessel (CPV). By using the technique of data assimilation, we have a numerical model which was developed in the laboratory of Mines and which consists of a simplified stochastic FE2 model. It turns out that this model is limited, because it is too expensive in terms of computing time and moreover it is only used for fixed finite elements. We therefore used the homogenization technique to have a deterministic constitutive model, which reduces the calculation time and which liberate us from the existing mesh. With this model, we aim to use machine learning techniques to be able to learn parameters that models the generation of acoustic emission data and to be able to assimilate it in order to determine the damage of the composite pressure vessel during its service.
Abstract
This work is being carried out under the framework of a thesis at the center of materials Mines -Paristech. The goal of this thesis is to realize a first digital twinning [...]
- 23
- read
Vibration of the cantilever beam using a piezoelectric actuator.
V. Goga, Š. Berta, V. Kutis, G. Galik, J. Paulech, L. Šarkán

complas2021.

Abstract
This paper deals with experimental and finite element analysis of vibration of the aluminum beam excited by a piezoelectric thin film actuator. One beam's end was fix supported and vibration of the beam's free end was measured using laser displacement sensor. Finite element model of the beam with piezoelectric actuator was created and three types of analyses were performed: modal, transient and harmonic. Results from finite element analyses were compared with data from experimental measurements.
Abstract
This paper deals with experimental and finite element analysis of vibration of the aluminum beam excited by a piezoelectric thin film actuator. One beam's end was fix [...]
- 7
- read
Actuator structure analysis using new electro-thermo-mechanical finite element for functionally graded materials.
J. Paulech, V. Kutiš, J. Murín, G. Gálik, V. Goga

complas2021.

Abstract
Proposed paper deals with electro-thermo-mechanical analysis of chosen actuator structure made od FGM using new finite element derived specially for this purpose. Rectangular cross-section of individual beams that form the von Mises structure with variation of material properties in longitudinal and lateral direction will be considered. Actuator action, electric voltage and temperature peak and also mechanical stress of the structure will be evaluated. Results from the analysis calculated using our new FGM beam finite elements will be compared to results from conventional FEM analysis where standard finite elements will be used.
Abstract
Proposed paper deals with electro-thermo-mechanical analysis of chosen actuator structure made od FGM using new finite element derived specially for this purpose. Rectangular [...]
- 11
- read
MOR of Piezoelectric Beam FEM Model and its Control
V. Kutis, J. Paulech, G. Galik, J. Murin, V. Goga

complas2021.

Abstract
This paper deals with the development of the FEM model of piezoelectric beam elements, where the piezoelectric layers are located on the outer surface of the beam core, which is made of functionally graded material. Subsequently, the FEM model created in this way is reduced by the so-called exact method, which is one of the MOR methods. Next MOR FEM equations are transformed into a state space model. Created state space model is connected to LQR controller and the reduced system is analysed. Developed FEM model, MOR technique, state space model and LQR control are implemented in FEM code MultiFEM.
Abstract
This paper deals with the development of the FEM model of piezoelectric beam elements, where the piezoelectric layers are located on the outer surface of the beam core, which [...]
- 7
- read
Numerical Modelling of Two-Phase Flow in Fractured Rock Masses Using Zero-Thickness Interface Elements
L. Barandiaran, J. Liaudat, C. López, I. Carol

complas2021.

Abstract
In recent years, the authors and co-workers have developed a 3D finite element model for coupled thermo-hydro-mechanical (THM) problems in fractured rock masses. Zero-thickness interface elements are used for taking into account explicitly the effect of fractures and discontinuities in the fluid flow as well as the effect of fluid pressure in the crack propagation. Furthermore, the use of zero-thickness elements as a discrete modelling approach for fractures and discontinuities makes it possible to account for the heat transport taking place within these elements, even when advection dominates over diffusion (high Peclet number) [1]. The model has been implemented in the finite element code DRAC5, which is equipped with fracture-based interface elements and MPI parallel capabilities [2]. The code was originally developed considering water-saturated porous medium and fractures. The new developments described in the present paper, include the extension of the original formulation to the case of two-phase (liquid and gas) flow within the porous medium and discontinuities. The liquid includes only liquid water species, while the gas phase includes water vapour and gas species. The formulation includes the equilibrium equation, the mass balance of water and gas species and the energy balance equation. The parameters of the retention and relative permeability curves for the interface elements, such as the gas entry value and the residual water saturation, are updated with the variation of the normal aperture. The new capabilities of the model are illustrated with some academic verification examples.
Abstract
In recent years, the authors and co-workers have developed a 3D finite element model for coupled thermo-hydro-mechanical (THM) problems in fractured rock masses. Zero-thickness [...]
- 18
- read
Embedded Discontinuity Finite Element Method (ED-FEM) for Modeling Fiber Failures in Random Fiber Networks
V. Tojaga, A. Kulachenko, S. Östlund

complas2021.

Abstract
Paper materials are natural composite materials where fibers are almost randomly distributed in a fiber network. Mechanical properties of fiber networks are known to be strongly controlled by fiber-fiber interactions and single fiber properties. A fiber network is often modeled as a beam network where beam-to-beam interactions are treated as cohesive zones and single beams stretch indefinitely without breaking. The latter assumption is not physically correct and leads to an overprediction of the mechanical response of the beam network. In this work, we present a computational modeling framework for simulating beam failures and thereby closing the gap to physically based micromechanical modeling of paper and packaging products. Modeling beam failure is a challenging engineering problem. At the onset of failure, the tangent stiffness tensor projected in a direction normal to the surface of discontinuity (commonly referred to as the localization tensor) is singular, i.e. we have a bifurcation point and the problem is ill-posed. Another implication of ill-posedness for the numerical simulation after a spatial discretization is a pathological mesh dependency of the computed result. We use the ED-FEM where a failure process zone (FPZ) is introduced into a multi-scale continuum mechanics formulation (i.e. the material is split into a small scale and a large scale defining the FPZ and the bulk material, respectively), making the computed result mesh independent. The multi-scale nature of the ED-FEM enables an operator splitting implementation method as opposed to carrying out the computations of the nodal displacement vector and the displacement discontinuity vector simultaneously with the global loop where the global stiffness matrix would be singular at the onset of failure. We show that fiber failures and fiber-fiber bond failures can contribute to the observed elastoplastic stress-strain response of paper.
Abstract
Paper materials are natural composite materials where fibers are almost randomly distributed in a fiber network. Mechanical properties of fiber networks are known to be strongly [...]
- 89
- read
Material models for highly dynamic metal forming processes
F. Katzmayr, C. Reisinger, T. Gross, S. Sieberer, W. Kunze, L. Wagner, C. Zehetner

complas2021.

Abstract
Nowadays, industrial processes like sheet metal bending or punching are performed with high precision. Further optimizations are only possible by simulation and appropriate material models and parameters. Goal of this work is to find a material model suitable for both, bending and punching processes, including the effects of plasticity at high strains and strain rates. The models are calibrated by material tests like tension or torsion tests.
Abstract
Nowadays, industrial processes like sheet metal bending or punching are performed with high precision. Further optimizations are only possible by simulation and appropriate [...]
- 16
- read
A Comparison Between Commercial and Open-Source Software for Finite Element Analysis of Elasto-Plastic Bending
A. Abdelaty, C. Zehetner, C. Reisinger, W. Kunze

complas2021.

Abstract
Nowadays, simulation is becoming more and more important in industries. Here we consider a typical industrial application in the field of sheet metal bending. A high number of simulations is necessary during the development process to perform parameter studies and optimizations. On the other hand, simulation tools should be also available for the customers of these machines, e.g., to plan the production of very specific profiles. In such cases, the optimal process parameters only can be found by simulation. Very important in this context are the license costs for commercial simulation software. Frequently, the simulations are not limited by computational power but by the number of available licenses, such that the duration for parameter studies is elongated. Also, with license costs it very expensive to provide a simulation platform to the customers. The presented case study has been carried out with the goal of comparing possible open source alternatives to expensive commercial Finite Element software. Exemplarily, we consider the elasto-plastic bending of a cantilever, using the Johnson Cook constitutive law. For this test case, a three dimensional Finite Element analysis is performed, comparing the results of open-source software (Salome-Meca) and a com mercial counterpart (Abaqus). Different element types and mesh sizes are compared, the usability of both tools, and the computational time. Considering the obvious price difference, both platforms show comparable results. Comparing the functionality of both programs, both are capable for modelling highly detailed and complex models for elasto-plastic material processing. However, for under standing the structure of the user interface of Salome-Meca is far more time consuming. Additionally, the performance of Salome-Meca on different operating systems is com pared: Salome-Meca on Linux, Salome-Meca on Linux, installed in a virtual machine on Windows, and finally Salome-Meca on Windows. All in all, it turned out that depending on the specific application Salome-Meca can be a powerful alternative to Abaqus for the considered industrial application.
Abstract
Nowadays, simulation is becoming more and more important in industries. Here we consider a typical industrial application in the field of sheet metal bending. A high number [...]
- 23
- read
Development of a through-process simulation workflow for spiral pipe forming including evolution of texture and dislocation substructure
M. Bönisch, H. Ghiabakloo, M. Seefeldt, A. Bael, N. Sanchez, S. Cooreman

complas2021.

Abstract
Spiral forming is a widely used industrial method for the manufacture of large diameter welded pipes from levelled steel strip. However, the multi-step helical forming process and post-treatment of the pipe influence the material behavior and alter the final mechanical anisotropy of the product. In addition, the complex microstructures of modern pipeline steels contain various sources of anisotropy including residual stresses, crystallographic and morphologic textures, and directional dislocation substructures. They do not only affect the local and global pipe strength, ductility and toughness during monotonic loading but also cause strong strain path change effects, e.g. a pronounced Bauschinger effect. Anisotropy thus poses a true challenge to pipeline designers making it difficult to accurately predict the final pipe behavior from the known properties of the hot-rolled high-strength coil, the starting point of the forming process. Still, such predictive power is vital to guarantee the structural integrity of pipelines without failure in case of in-service loads beyond the elastic range. The pipe manufacturing process can be simplified into two steps: decoiling (incl. levelling) and spiral forming. For subsequent quality control, samples are extracted from the pipe, per standard flattened and tensile tested in hoop direction. With regard to developing a computational twin of the complete manufacturing and testing process, we represent each step by a separate finite element (FE) model. The full through-process simulation workflow thus necessitates tools to transfer the material state between individual FE models. Here, we present such a workflow for the dislocation substructural hardening model by [Peeters et al., Acta Mater. (2001) 49:1607- 1619]. For each material point, macroscopic and microscopic state variables, including residual stress, crystallographic texture and dislocation densities, are first interpolated and then transferred to the next model. In this way, the evolution of different anisotropy sources can be studied starting from coil via pipe and ending with tensile testing
Abstract
Spiral forming is a widely used industrial method for the manufacture of large diameter welded pipes from levelled steel strip. However, the multi-step helical forming process [...]
- 10
- read
Solving an inverse problem concerning the sheet metal blank geometry in an industrial application to minimize the processing time
S. Mayr, C. Zehetner, C. Reisinger, W. Kunze

complas2021.

Abstract
This paper concerns the optimization of an industrial sheet metal forming process on an automatic panel bender from Salvagnini Maschinenbau GmbH combined with a corner former from an external company. By combining these two machines and optimizing the sheet metal blank geometry, production is much cheaper and faster because one processing step is eliminated.
Abstract
This paper concerns the optimization of an industrial sheet metal forming process on an automatic panel bender from Salvagnini Maschinenbau GmbH combined with a corner former [...]
- 8
- read
Effect of long-term pore pressure evolution on the integrity of cement plugs of abandoned oil wells in CCS sites
A. Martínez, J. Liaudat, C. Lopez, I. Carol

complas2021.

Abstract
In the context of Carbon Capture Storage (CCS) in abandoned hydrocarbon reservoirs, a preliminary study of the effects of pore pressure evolution on the integrity of oil-well cement seals is performed. A 2D cross-section of the sealed oil-well system (caprock-external cement sheath-steel casing-cement plug) is analysed along its service life (injection/production activities and abandonment) using the Finite Element Method with zero-thickness interface elements to represent potential cracks. In particular, these elements are pre-inserted in the analysis in between the contacts of caprock-external cement sheath, external cement sheath-casing and casing-cement plug. The results presented show that, depending on the initial state and range of pressure evolution, the different interfaces considered may open or close in a non-trivial manner during the pressure return process. This seems to indicate the importance of considering carefully the pressure return process and subsequent effective stresses evolution in abandoned reservoirs recycled to CCS, in order to avoid that new cracks in well cement seals may lead to potential CO2 leakage in the storage site.
Abstract
In the context of Carbon Capture Storage (CCS) in abandoned hydrocarbon reservoirs, a preliminary study of the effects of pore pressure evolution on the integrity of oil-well [...]
- 17
- read
Transient large heat advection in fractured rock: a zero-thickness interface formulation
A. Perez, I. Carol, P. Prat

complas2021.

Abstract
Two of the main mechanisms of heat transport in engineering problems are diffusion and advection. In a FEM context it is well known that if advection dominates over diffusion (Péclet number Pe > 1), traditional Galerkin formulations may lead to oscillatory results [1], although in many practical engineering situations, such as the case of geological materials, fluid velocities generally remain small due to the low permeability of the pore system and this problem may be ignored [2]. However, in the presence of preference paths of fluid circulation this situation may change. The existence of open fractures or cracks may produce high fluid velocities through them in comparison with those found in the surrounding porous medium. This situation can lead to exceeding the limit condition Pe > 1. In a FEM context, these preferential paths or cracks are sometimes modelled by using double-nodded zero-thickness interface elements. Thus, the paper discusses these concepts and presents a zero-thickness interface FE formulation for large advection, which consists of an implicit extension of Taylor´s explicit formulation for the transient problem based on characteristics [1], which has been developed for traditional continuum elements in its explicit form. Some verification examples are also presented, showing that even in the extreme case of pure advection (Pe → ∞), the formulation exhibits a good performance to represent the heat transport by the fluid along the mesh.
Abstract
Two of the main mechanisms of heat transport in engineering problems are diffusion and advection. In a FEM context it is well known that if advection dominates over diffusion [...]
- 8
- read
Investigating the Creep Behaviour of Marine Soft Structured Clay by FEM with an Elasto-viscoplastic Constitutive Model.
M. Jiang, C. Woyeya, J. Liu

complas2021.

Abstract
The time-dependent creep deformation of marine soft-structured clay is a major cause of foundation failure on soft grounds around the globe. This study focuses on the analysis of the drained and undrained time-dependent creep behavior of a normally consolidated (NC)-Kyuhoji marine soft-structured clay by FEM with a new Elasto-viscoplastic (EVP) constitutive model. One-dimensional creep and consolidated undrained creep element tests are simulated to analyze the creep behavior of soft clay under constant load conditions. The creep period of 1157days is used in the drained state with consolidation pressures from 100 kPa to 450 kPa with 50 kPa incremental intervals. The undrained time-dependent creep behavior of Kyuhoji clay is analyzed under varying constant creep stresses-qcrp (0.3qf, 0.5qf, 0.6qf, and 0.7qf, where qf is the undrained peak strength), and creep periods (11.6days, 463 days, and 5787days). The results show the capability of the new EVP model in analyzing creep failure behavior of marine soft-structured clayey and can explain the reason for the premature abrupt collapse of foundations on soil grounds where drainage is impeded under constant load.
Abstract
The time-dependent creep deformation of marine soft-structured clay is a major cause of foundation failure on soft grounds around the globe. This study focuses on the analysis [...]
- 65
- 5/5
- read
A rigorous variant of the shear strength reduction method and its geotechical applications
S. Sysala, E. Hrubesova, Z. Michalec, F. Tschuchnigg

complas2021.

Abstract
This paper is focused on a new optimization variant of the shear strength reduction (OPT-SSR) in non-associated Mohr-Coulomb plasticity. The OPT-SSR method mimics the limit analysis problem and enables to compute the factor of safety without performing an elasto-plastic analysis. It is shown that this optimization problem is well defined and closely related to recently developed Davis approaches used in combination with the standard SSR method. Next, the duality between the static and kinematic principles of OPT-SSR is introduced. For the numerical solution, a regularization method is suggested.
Abstract
This paper is focused on a new optimization variant of the shear strength reduction (OPT-SSR) in non-associated Mohr-Coulomb plasticity. The OPT-SSR method mimics the limit [...]
- 7
- read
Experimental and Numerical Study of Strength Prediction of Cold forged Parts Based on the Chaboche Combined Hardening Model.
Y. Shinkai, O. Kada, R. Nishimura, H. Narumiya, N. Yoshikawa

complas2021.

Abstract
The high manufacturing costs of heat-treated cold forged parts has necessitated the possible elimination of the heat treatment process for improving their mechanical properties. In such a scenario, the strength of the parts can be determined by the degree of work hardening during cold forging; moreover, optimizing the shapes of cold forged parts based on strength prediction via finite element analysis (FEA) can assist in realizing the weight reduction of these parts as well as the cost reduction. However, when the parts are subjected to tensile loads during operation in the opposite direction of compressive loads imposed during cold forging (the Bauschinger effect), predicting the strength of these parts using an isotropic hardening model is inappropriate because it overestimates their strength. Only a few studies have reported on FEA models that consider the influence of the Bauschinger effect in the field of bulk forming. In this study, a strength prediction method using a Chaboche combined hardening model was investigated for predicting the strength of cold forged parts that are not subjected to heat treatment after cold forging. Simple shear tests were performed to obtain stress–strain curves with reversed loading over a wide range of strains. The simple shear tests facilitated the accurate prediction of the strength of the cold forged parts.
Abstract
The high manufacturing costs of heat-treated cold forged parts has necessitated the possible elimination of the heat treatment process for improving their mechanical properties. [...]
- 10
- read
A comparative study of material hardening models for forming operations and prediction of kinematic hardening by means of an analytical indicator
U. Ahmed, R. Lafarge, A. Brosius

complas2021.

Abstract
This publication is focused on comparing three different material hardening models i.e. purely isotropic, mixed hardening and purely kinematic hardening model for the simulation of forming operations. The influence of nonlinear strain paths is investigated using deep drawing and strip tensile bending experiments and their comparison with numerical simulations. This comparison enables us to determine which of the three material models is more accurate for forming operations. Subsequently, the complex nonlinear strain paths are analyzed using an analytical indicator developed at the Chair of Forming and Machining Process, TU Dresden [3], to predict the influence of kinematic hardening by comparing the experimental results with a combined material hardening model as well as a purely isotropic and kinematic material model. The analytical indicator illustrates the regions in deformed samples that are most affected by kinematic hardening and shows the difference in target values as a result of mixed and purely isotropic hardening law
Abstract
This publication is focused on comparing three different material hardening models i.e. purely isotropic, mixed hardening and purely kinematic hardening model for the simulation [...]
- 38
- read
Numerical Analysis of the Effect of Friction during Forming of Tube with Differential Wall Thickness
N. Kawagoshi, S. Tamura, T. Kawachi

complas2021.

Abstract
Steel tubes with differential wall thickness are required to reduce the weight of automobiles. One of the forming processes of steel tubes with differential thickness is the ironing of the inner surface[1]. In the first process, the end of the steel tube is expanded. In the second process, the punch is pushed in and the inner surface of the steel tube is ironed. As a result, the steel tube with a wall thickness difference of 50% can be formed. In this report, the behaviour of the steel tube during forming and the possible forming condition were clarified using FEM (Finite Element Method) analysis. Abaqus/Explicit was used for FEM analysis, and analysis was performed using an axisymmetric model. As a result of the analysis, it was found that the friction coefficient difference Δμ needs more than the threshold in order to form the steel tube with differential thickness. If Δμ is larger than the threshold, the steel tube is fixed at the expansion part, and the steel tube with differential thickness can be formed. On the other hand, if Δμ is smaller than the threshold, the expansion part is slipping during forming and the steel tube with differential thickness cannot be formed. This result suggests that the effect of the friction coefficient can be evaluated quantitatively using FEM analysis.
Abstract
Steel tubes with differential wall thickness are required to reduce the weight of automobiles. One of the forming processes of steel tubes with differential thickness is the [...]
- 8
- read
Adaptive time stepping approach for Phase-Field modeling of phase separation and precipitates coarsening in additive manufacturing alloys
S. Fetni, J. Delahaye, L. Duchêne, A. Mertens, A. Habraken

complas2021.

Abstract
In the present work, the capacity of phase field method to highlight microstructural changes during the spinodal decomposition of a given binary alloy basing on the Cahn-Hilliard equation is presented. Then, growth and coarsening of precipitates are studied using the KKS (Kim-Kim-Suzuki) model, which includes Cahn-Hilliard and Allen-Cahn equations. The implementation of time stepping algorithms to resolve Phase-Field equations is illustrated. Within Fourier space, using semi-implicit spectral method, it has been demonstrated that it allows faster computing than schemes based on finite difference method. First, spinodal decomposition of a given binary alloy under isothermal loading is implemented and three time stepping approaches are applied: constant time stepping, non- iterative and an iterative method. While the non-iterative method is faster than the constant time stepping scheme, the iterative one, although relatively more CPU consuming, can guarantee the convergence of the computing. These methods are combined in an innovative approach tested on 1D, 2D and 3D grids. The effectiveness of the adopted adaptive time-stepping algorithm allows resolving equations in reasonable CPU time. It predicts different physical phenomena, such as phase separation and growth and coarsening of precipitates induced by important interfacial energies.
Abstract
In the present work, the capacity of phase field method to highlight microstructural changes during the spinodal decomposition of a given binary alloy basing on the Cahn-Hilliard [...]
- 134
- read
Shakedown analysis of 3D frames under multiple load combinations using mixed fiber beam elements
D. Magisano, L. Leonetti, G. Garcea

complas2021.

Abstract
If the stress intensity at a certain point of a structure made of ductile materials reaches the yield point, the structure does not necessarily fail or deform excessively. Instead, stress redistribution could take place and some further load increments could be supported. Thus, the actual load-carrying capacity of a structure is generally higher than the elastic limit and this overstrength can be exploited for a cost-effective design. However, during their operational life, structures are subjected to variable loads, whose law of variability in time is often unknown. Instead, it is usually possible to have a good estimate of the variability range in terms of maximum and minimum load amplitude. Within this context, shakedown analysis is able to provide a reliable safety factor against plastic collapse, loss in functionality due to excessive deformations (ratcheting) or collapse due to low cycle fatigue (plastic shakedown). This work presents an efficient fiber analysis for evaluating the shakedown safety factor of 3D frames under multiple load combinations. Mixed beam elements are employed for an accurate discretization of the structures. A continuation method, similar to an incremental elasto-plastic analysis, is used at structural level. It evaluates a fictitious equilibrium path made of a sequence of safe states with a converging non-decreasing load factor. Each point of the path is obtained by finding kinematic variables corresponding to self-equilibrated stresses satisfying Melan's condition for the current load factor to be safe. The stress admissible domain is defined at fiber level as a function of the load factor using the maximum and minimum effect due to all loads. An iterative state determination provides finite element stresses corresponding to assigned kinematic variables and load factor. The overall analysis differs from previous proposals for two novelty points. Firstly, a direct application of the Newton method is possible, without any need for constrained optimization solvers. Moreover, dimension and complexity of the load domain does not affect the computational cost of the nonlinear analysis. Numerical tests highlight an accurate estimate of the safety factor using a small number of fibers and an efficient solution also for large buildings.
Abstract
If the stress intensity at a certain point of a structure made of ductile materials reaches the yield point, the structure does not necessarily fail or deform excessively. [...]
- 7
- read
A Mixed Finite Element Formulation for Elastoplasticity
M. Nagler, A. Pechstein, A. Humer

complas2021.
- 8
- read
An MD-FE coupling simulation method applied to fracture of viscoelastic-viscoplastic glassy polymers.
W. Zhao, S. Pfaller

complas2021.
- 18
- read
Coupling of mechanics and transport in discrete meso-level model: model verification
J. Mašek, J. Eliáš

complas2021.

Abstract
In the contribution, a discrete meso-level lattice particle model is presented. A fully coupled mechanical and transport solver is validated using selected physical and numerical experiments from the literature. A water flow through a pre-cracked Brazilian disc is measured in dependence on opening of cracks scattered throughout the specimen. Secondly, a corrosion induced cracking is modelled and results compared against the physical experiment and numerical simulations.
Abstract
In the contribution, a discrete meso-level lattice particle model is presented. A fully coupled mechanical and transport solver is validated using selected physical and numerical [...]
- 16
- read
Characterization of Plasticity and Fracture Behavior of Aluminum 6061-T4 Sheet for Deep Drawing Simulation
S. Hoque, F. Duddeck

complas2021.

Abstract
A hybrid experimental-numerical approach to characterize plasticity and ductile fracture properties of aluminum 6061-T4 sheet is presented. The anisotropic elasto-plastic behavior is characterized by a Barlat89 model and the ductile fracture behavior by a GISSMO model in combination with the Xue-Wierzbicki model. We discuss then the validation procedure and the results related to a deep-drawing case where the simulation is carried out in a commercial FE-solver LS-DYNA. The drawing depth at fracture, as an exemplary result, shows a very good agreement between simulation and experiment.
Abstract
A hybrid experimental-numerical approach to characterize plasticity and ductile fracture properties of aluminum 6061-T4 sheet is presented. The anisotropic elasto-plastic [...]
- 51
- read
Mode I+III multiscale cohesive zone model: applications to facet orientation and toughening
V. Lazarus

complas2021.

Abstract
When subjected to some anti-plane shear mode III loading, segmentation of the crack front frequently occurs during propagation: even if the crack is initially planar, propagation produces facets/segments rotated toward the shear free direction [1]. These facets induce some modifications in the local loading of the crack tips that can be captured through a multi-scale cohesive zone model [2]: Assuming that the width of the facets is small in comparison to their length, the facets can be considered at the microscale, as a bidimensional periodic array of tilted cracks perpendicularly to the direction of propagation, and at the macroscale, as a growing Cohesive Zone. The model was developed initially supposing a constant period, small tilt angles and non-overlapping facets. We relaxed recently these assumptions to deal with more realistic cases including coarsening of the facets, large tilt angles and overlap. For this, the microscale problem is solved using XFEM and the outputs are further incorporated into the model to get some results on the macroscale, in particular the effective fracture energy. By comparing the results to some experiments [3], we demonstrate the ability of the approach (i) to determine the inclination of the facets and (ii) to quantify, in both fatigue and brittle fracture, the toughening due to the decrease of the crack opening driven by the unbroken ligaments between the facets.
Abstract
When subjected to some anti-plane shear mode III loading, segmentation of the crack front frequently occurs during propagation: even if the crack is initially planar, propagation [...]
- 12
- read
Influence of Topology Hybridization and Functional Grading on the Compressive Properties of TPMS-based Lattice Cores
C. Ejeh, I. Barsoum, R. Alrub

complas2021.

Abstract
New designs of lattice cores based on the mathematically-deduced sheet-triply periodic minimal surface is proposed in this work. Elastic-plastic simulations are performed to evaluate the superiority of the novel designs based on their quasi-static loading compressive properties.
Abstract
New designs of lattice cores based on the mathematically-deduced sheet-triply periodic minimal surface is proposed in this work. Elastic-plastic simulations are performed [...]
- 12
- read
Numerical analysis of the dynamic behaviour of a nonlinear preloaded intervertebral disc
L. Rouleau, J. Garcher, J. Deü

complas2021.

Abstract
In order to understand the mechanisms in degenerative disc disease and support the design of robust disc prothesis, accurate modelling of the intervertebral disc's (IVD) dynamics is necessary. Many experimental studies relate changes in the mechanical properties of the disk to the degenerative state of the IVD. However, further studies are necessary to better assess the influence of parameters which may affect those mechanical properties on the dynamic behaviour of the IVD, especially its dissipative behaviour. The goal of this work is to investigate the effect the static preload and the frequency of excitation through numerical simulations.
Abstract
In order to understand the mechanisms in degenerative disc disease and support the design of robust disc prothesis, accurate modelling of the intervertebral disc's (IVD) dynamics [...]
- 14
- read
Effects of Age and Loading Velocity on the Delamination Strength of the Human Aorta
L. Horný, L. Roubalová, Z. Petrivý, H. Chlup, J. Kronek, P. Tichý, T. Adámek, A. Blanková, T. Suchý

complas2021.

Abstract
Delamination strength is the mechanical property which plays a key role in the pathological process referred to as Arterial Dissection. This dissection, known especially for its occurrence in the thoracic aorta, is manifested by a separation of the layers of an artery wall, and may end with total rupture and internal haemorrhaging. Although its incidence is relatively rare, from 3 to 6 cases per 100 000 per year, it is a life-threating disease with a significant lethality [1-3]. The exact conditions under which the dissection is initiated, and as a crack propagates through the arterial wall, remain an open topic in computational as well as experimental mechanics. The aim of our study is to contribute to the deepening of our knowledge of Arterial Dissection, by collecting experimental data which is suitable for the purpose of showing how the delamination strength measured in the peeling experiments depends on age and anatomical location. In addition to the effects of age and location, our study also focuses on the effect of loading rate. The experimental branch of our research is complemented by a computational modelling of the delamination interface, in which we are looking for a numerical characterization of the material parameters describing discontinuity propagation. An XFEM model of the peeling experiment is built in Abaqus, which in our approach plays the role of the regression analysis, incorporating the cohesive zone (CZ) in order to model the delaminating arterial layers. The main objective is to obtain a detailed description of a set of constitutive parameters, which would be age- and location-specific. Our present data suggest that delamination strength strongly depends on age, and furthermore, the anatomical site also seems to be a significant factor. On the other hand, the loading velocity does not cause significant changes in results.
Abstract
Delamination strength is the mechanical property which plays a key role in the pathological process referred to as Arterial Dissection. This dissection, known especially for [...]
- 14
- read
Effect of Lode Parameter and Stress Triaxiality on the Effective Plastic Yield Properties of Triply Periodic IWP Ligament-Based Minimal Surface
N. Baghous, I. Barsoum, R. Al-Rub

complas2021.

Abstract
Due to the advancements in additive manufacturing and increased applications of additive manufactured structures, it is essential to fully understand both the elastic and plastic behavior of cellular materials, which include the mathematically-driven triply periodic minimal surfaces (TPMS). The elastic and plastic behaviors have been well established for many TPMS structures. These structures are however rather computationally expensive to model explicitly when used in meta-materials and hence the need to develop an accurate yield function in order to model their plastic behavior in a homogenized approach. In this study, the effect of different loading conditions is numerically investigated on the effective yield strength of IWP ligament based (IWP-L) TPMS.
Abstract
Due to the advancements in additive manufacturing and increased applications of additive manufactured structures, it is essential to fully understand both the elastic and [...]
- 18
- read
Thermomechanical FEM-based modelling for semi-crystalline polymers exhibiting the double yield phenomenon
P. Hao, V. Laheri, F. Gilabert

complas2021.

Abstract
Thermoplastic polymers nowadays are drawing attention in the automotive industrial thanks to their low cost, lightweight, and sustainability. They can be simply reshaped through the thermoforming process by heating up above their melting temperatures. Most thermoplastic polymers are semicrystalline ones that are composed of micro-spherulite structures with amorphous and crystalline regions. The amorphous region refers to the randomly distributed polymer chains whereas these chains are well-ordered lamellae in crystalline regions. These two phases interact with each other and result in a highly non-linear material response with the famous "double yield phenomenon". Therefore, to accurately predict the rate- and temperature- dependent semicrystalline polymers (SCPs) is still a challenge. Besides temperature increases due to the plastic dissipation under high-speed loading, inversely leading to the thermal softening and degrading the material performance. In this work, We proposed a thermomechanical modeling strategy for SCPs with a double yield phenomenon. Material characterization only requires few essential tests and the predicted results are promising.
Abstract
Thermoplastic polymers nowadays are drawing attention in the automotive industrial thanks to their low cost, lightweight, and sustainability. They can be simply reshaped through [...]
- 10
- read
Non-iterative numerical implementation for the constitutive modelling of pressure-dependent elastoplasticity using paraboloidal yield criteria
V. Laheri, P. Hao, F. Gilabert

complas2021.

Abstract
Paraboloidal plastic yield criterion appropriately conveys the nonlinear elastoplastic behaviour of the polymers. The elastoplastic stress and strain relationship for the paraboloidal yield criteria is devised using the radial return mapping algorithm. For the numerical implementation of the devised relationship, an exact solution method using the classical loading-unloading conditions is presented. It avoids the erstwhile iterative scheme and improves efficiency of the solution technique. The non-iterative mathematical implementation is verified with the polymer experimental results in tension, compression and shear for simple and real-sized geometries under large strain conditions using the Abaqus solver tool to prove its functionality and computational efficiency.
Abstract
Paraboloidal plastic yield criterion appropriately conveys the nonlinear elastoplastic behaviour of the polymers. The elastoplastic stress and strain relationship for the [...]
- 12
- read
Geometrically exact integral-based nonlocal model of ductile damage: basic properties and numerical treatment
A. Shutov, V. Klyuchancev

complas2021.

Abstract
We develop the integral approach for the analysis of nonlocal ductile damage in metals. The starting point is the previously proposed phenomenological model of finite strain plasticity. The original damage model is delocalized by the averaging operator, applied to damage-related quantities like porosity and continuity. Depending on the implemented delocalization procedure, at least one internal length parameter in introduced into the formulation. As a result, the damage localization is controlled by the presence of length-like parameters, thus regularizing the boundary value problem. Owing to the regularization, numerically robust and physically sound simulations of crack initiation and propagation are possible. Unphysical localization of strain and damage into a zero thickness layer is effectively prevented. From the theoretical standpoint, the basic properties of the new material model are analysed. Model’s thermodynamic consistency, objectivity, and w-invariance are established. Efficient numerical algorithms are proposed. To test the robustness of the integral-based approach, low-order meshless smoothed particle simulations are carried out. As a demonstration problem, we simulate crack initiation and propagation in a compact tension specimen. The resulting force-displacement curves, apparent fracture toughness, energy dissipation, and patterns of damage distribution provide insight into the mechanical phenomena, captured by the framework. The impact of the modelling assumptions on the predicted structural strength is clarified: Isotropic and anisotropic averaging is discussed; the delocalization is applied on various configurations; continuity is introduced as a dual damage variable to minimize the unrealistic diffusion of damage.
Abstract
We develop the integral approach for the analysis of nonlocal ductile damage in metals. The starting point is the previously proposed phenomenological model of finite strain [...]
- 13
- read
Some Computational Issues in the Elasto-Plastic Modelling of Snow
G. Vallero, M. Barbero, F. Barpi, M. Borri-Brunetto, V. Biagi

complas2021.

Abstract
In this work, the Authors describe some of the still open and unsolved questions related to the constitutive modeling of snow with reference to Elasto-Plastic approaches. Furthermore, some suggestions on possible computational solutions through Finite Element tools are highlighted. The goal is twofold: first, we try to summarize the current state-of-the-art of FE analysis on snow; and second, we suggest some possible research directions and computational solutions to improve the existing mechanical models.
Abstract
In this work, the Authors describe some of the still open and unsolved questions related to the constitutive modeling of snow with reference to Elasto-Plastic approaches. [...]
- 22
- read
A Comparison of FE Analysis of Columns Utilizing Two Stress-Strain Material Relations and Two Different Solvers: ANSYS vs. SCIA Engineer
D. Jindra, Z. Kala, J. Kala

complas2021.

Abstract
Paper presents a Comparison of Ramberg-Osgood and Bilinear Stress-Strain Material Relation of Duplex Stainless Steel CHS Columns in Compression Utilizing Two Different Implicit Numerical Solvers: ANSYS and FEM Solver of SCIA Engineer
Abstract
Paper presents a Comparison of Ramberg-Osgood and Bilinear Stress-Strain Material Relation of Duplex Stainless Steel CHS Columns in Compression Utilizing Two Different Implicit [...]
- 30
- read
New formulation of metallic materials constitutive models by an energy approach
B. Saade, A. Gavrus, J. Bodgi, N. Bejjani

complas2021.

Abstract
In a classical way the Cauchy stress tensor is expressed in function of instantaneous internal variables as the strain, the strain rate and the temperature. If good predictions of the response of materials are obtained under quasi-static loadings, inaccurate estimations are finding for some severe dynamic conditions where high plastic strain, high strain rate or temperature gradients and microstructures changes occur during the plastic flow. To describe the metals work hardening under specific loadings, the traditional laws reduce the influence of the material deformation history only through the cumulated plastic strain defined from the time integral of the generalized strain rate. From a thermodynamic point of view the material stress is rather related to the dissipated plastic strain energy responsible for any change in the material thermomechanical state. This work propose then a new formalism to define a material constitutive equation from an equivalent stress expressed as a function of the dissipated plastic deformation energy. This new approach takes into account the microstructure changes which govern a lot of the physical mechanisms responsible for plastic flows: work-hardening, dynamic softening and phase transformation. This formulation remains valid for large paths of material deformation and for all the spectrum of loading conditions: from static, transient until rapid dynamic ones. Variational energetic approaches were first mentioned by R. HILL [1] indicating that the work-hardening phenomenon depends on the plastic strain energy. Recently a new formalism introduced by M. YOSHINO et al. [2] define for a first time a named reference stress as a function of plastic strain energy. From a thermodynamics point of view a reliable energy approach must be based on the principle that any system finds its time evolution by minimizing the losses energies and minimising the generated entropy [3]. One of the main objectives of this work is to find in an energetic framework the proposed general constitutive laws [4] defining the equivalent stress as a mixture between a hardening and a saturation term via the material fraction undergoing dynamic softening (recovery, recrystallization or phase transformation) described by an Avrami law expressed in terms of plastic strain. Firstly will be finding the energetic form of the usual hardening formulations proving the equivalency between the new formulation and the traditional ones. The obtained new constitutive model will be discussed comparing to a numerical implementation on the incremental elastic-plastic Prandtl-Reuss equations resolution. References: [1] R. Hill, The Mathematical theory of plasticity, Oxford, The Clarendon Press, (1950). [2] M. Yoshino et T. Shirakashi, Flow-stress equation including effects of strain-rate and temperature history, Int. J. Mech. Sci., 39 (12) :1345-1362 (1997). [3] A. Bejan, Advanced Engineering Thermodynamics, 2nd ed. Wiley, New York, (1997). [4] A. Gavrus, Constitutive equation for description of metallic materials behavior during static and dynamic loadings taking into account important gradients of plastic deformation, Key Engineering Materials, 504-506:697–702 (2012).
Abstract
In a classical way the Cauchy stress tensor is expressed in function of instantaneous internal variables as the strain, the strain rate and the temperature. If good predictions [...]
- 31
- read
FIBRE4YARDS_Shipbuilding4.0_CompassIS_20220211
D. Sá

This presentation was made on the 11th of February 2022 at the Shipbuilding & Lifecycle Tech 4.0.

Abstract
The main objective of the FIBRE4YARDS project is to maintain European global leadership in ship building and ship maintenance, through implementation of the Shipyard 4.0 concept in which advanced and innovative FRP manufacturing technologies are successfully introduced. This project has received funding from European Union's Horizon 2020 research and innovation programme under grant agreement N° 101006860.
Abstract
The main objective of the FIBRE4YARDS project is to maintain European global leadership in ship building and ship maintenance, through implementation of the Shipyard 4.0 concept [...]
- 8
- read
Advances in maximum-entropy-based meshless methods
D. Kochmann

particles2021.
- 11
- read
Simulation of Demanding Manufacturing Processes
P. Eberhard

particles2021.
- 7
- read
Modeling and Simulation Tools for Industrial and Societal Research Applications: Digital Twins and Genome-based Machine-learning
T. Zohdi

particles2021.
- 10
- read
DEM as a critical tool for understanding particle flows
C. Hrenya

particles2021.
- 10
- read
Multiscale modeling of granular media: from geomechanics to 3D printing
J. Zhao

particles2021.
- 7
- read
New links between continuum and particle-/contact-mechanics
S. Luding

particles2021.
- 7
- read
The P-DNS method: a particle-based approach to solve turbulent fluid flows
S. Idelsohn

particles2021.
- 10
- read
Timestepping and Space and Time Errors and Stability in the Material Point Method
M. Berzins

particles2021.

Abstract
The choice of the time step for the Material Point Method (MPM) is often addressed by using a simple stability criterion, such as the speed of sound or a CFL condition. Recently there have been several advances in understanding the stability of MPM. These range from non-linear stability analysis, through to Von Neumann type approaches. While in many instances this works well it is important to understand how this relates to the overall errors present in the method. Although it has been observed that spatial errors may dominate temporal onesi at stable time steps, at the same time recent work has made more precise the forms of the different MPM errors. This now makes it possible to understand how the different errors and the stability analysis are connected. At the same time this also requires simple computable estimates of the different errors in the material point method. The use of simple estimates of these errors imakes it possible to connect some of the errors introduced with the stability criteria used. A number of simple computational experiments are used to illustrate the theoretical results.
Abstract
The choice of the time step for the Material Point Method (MPM) is often addressed by using a simple stability criterion, such as the speed of sound or a CFL condition. Recently [...]
- 17
- read
A discrete element contact model for fatigue crack growth analysis
L. Ma, G. Koval, C. Chazallon, Y. Descantes

particles2021.

Abstract
The proposed contact model offers a reliable technique for realizing continual crack growth in discrete samples. Such contact model could combine with Paris’ law, thus further enhancing its capacity of simulating fatigue crack growth. Based on the proposed contact model, calculation of stress intensity factor (SIF) only requires contact force and relative displacement of consisting particles, and its convenience indicates a promising generalizability in fatigue crack growth analysis for geomaterials.
Abstract
The proposed contact model offers a reliable technique for realizing continual crack growth in discrete samples. Such contact model could combine with Paris’ law, thus further [...]
- 35
- 4/5
- read
The 'Signature' of Particle Geometry - DEM Modelling Perspective
S. Lee, C. Lee, M. Shin, P. Tripathi

particles2021.

Abstract
This study evidences that the particle surface-area-to-volume ratio (A/V) and the particle volume (V) have the key information of particle geometry and the ‘signature’ is realized by a power-law relationship between A/V and V in a form of V = (A/V)α × β. We find that the power value α is influenced by the shape-size relationship while the β* term (β evaluated with a fixed value of α = -3) informs the average particle shape of a granular material regarding the overall angularity. This study also discusses how the particle shape can be retrieved in terms of Wadell’s true sphericity using the A/V and V. This concept is linked to another shape index M that interprets the particle shape as a function of surface area A, volume V, and size L. This paper explains the analytical aspects of geometric ‘signature’ and examines the idea using the example particles to address the DEM modelling-related questions.
Abstract
This study evidences that the particle surface-area-to-volume ratio (A/V) and the particle volume (V) have the key information of particle geometry and the ‘signature’ [...]
- 10
- read
A smoothed particle hydrodynamics study on modelling the flowability, passability and fill-ability of steel fibre suspended self-compacting concrete.
S. Kulasegaram, A. Mimoun

particles2021.

Abstract
Modelling of self-compacting steel fibre reinforced concrete (SCSFRC) by using smooth particle hydrodynamics (three-dimensional 3D simulation).
- 9
- read
Numerical Investigation of Churning Losses Caused by the Oil-Piston Interaction within a Calender Roll of a Paper Machine Using a Particle-Based Simulation Method
M. Britz, B. Grashof, P. Wegele, H. Linder

particles2021.

Abstract
Within the paper production process, certain surface properties of the paper web, e.g. smoothness and gloss, are produced or modified by so-called calenders. This paper machine device consists of several rolls, which apply high pressure and temperature on the paper web. Calenders exhibit large widths up to more than 10 m. Therefore, it is challenging to precisely adjust the required mechanical forces in order to apply a defined line load across the entire width of the paper web. By making use of Voith’s Nipco technology, both line load and roll deflection are controlled by multiple pistons which can be individually adjusted. This is achieved by pressure oil injection. The piston works also as a hydrostatic bearing in such a way that a thin lubrication film is formed between the stationary piston head and the rotating roll shell. Additional oil is injected into the roll for cooling purposes. Within this paper we present an industry-related approach to take advantage of present-day Moving Particle Simulation (MPS) methods. Hereto, we used the commercial software Particleworks® for a numerical investigation of the flow phenomena within a calender roll. The focus of our investigation were the churning losses caused by the interaction between the rotating oil and the mounted piston head. For this purpose, simulations of different oil volumes were performed. The results show that the piston head has a clear impact on the flow field. Firstly, the oil is reflected in upstream direction, causing disturbances in the subsequent flow. Secondly, the oil which streams around the piston rod leads to the formation of a Kármán vortex street. Thirdly, a reduction of oil volume results in a reduction of the churning loss.
Abstract
Within the paper production process, certain surface properties of the paper web, e.g. smoothness and gloss, are produced or modified by so-called calenders. This paper machine [...]
- 7
- read
A DEM Generalized Kelvin Contact model for Predicting Stiffness of Asphalt Mixtures
G. Câmara, N. Azevedo, R. Micaelo

particles2021.

Abstract
Rigid particle models based on the discrete element method (DEM) have been adopted in the study of fracture and viscoelastic properties of mastic and asphalt mixtures. In this work, a 3D particle model is proposed based on the Laguerre-Voronoi diagrams of the grain structure representing the asphalt mixture or of the mastic.
Abstract
Rigid particle models based on the discrete element method (DEM) have been adopted in the study of fracture and viscoelastic properties of mastic and asphalt mixtures. In [...]
- 20
- read
SPH based study of confined microflows characterized by abrupt changes in cross-sectional area
A. Liakopoulos

particles2021.

Abstract
In this paper, we investigate the application of Smoothed Particle Hydrodynamics (SPH) method to the computation of flows in microchannels with sudden expansion. Numerical modeling with SPH involves the treatment of flowing matter as distinct mass points, leading to discretization of the Navier-Stokes equations (or other appropriate PDEs) and providing great flexibility to handle large deformations. The computational methodology exhibits similarities with other particle methods, such as Molecular Dynamics (MD), Dissipative Particle Dynamics (DPD), and Smooth Dissipative Particle Dynamics (SDPD). These similarities lead relatively easily to the development of a weakly compressible SPH within the framework of Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). The LAMMPS environment, albeit mostly intended to MD simulations near the atomic scale, provides a fully parallelized framework for particle simulations, such as SPH. In this work we studied microchannel flows of variable cross section. Sudden expansions generate strong discontinuities in the flow field. Flow models based on various inlet/outlet boundary conditions for example, Periodic/Fixed BCs, and their implementations are presented in the context of 3-D simulations. Minor artifacts may be observed near the wall corner discontinuities, but, overall, the SPH captures the main flow characteristics and achieves very good accuracy
Abstract
In this paper, we investigate the application of Smoothed Particle Hydrodynamics (SPH) method to the computation of flows in microchannels with sudden expansion. Numerical [...]
- 7
- read
Development of MPS Method for Analysing Convection and Solidification of Multi-Component Corium in Severe Accident of a Light Water Reactor
T. Fukuda, A. Yamaji, L. Xin, J. Haquet, A. Boulin

particles2021.

Abstract
In this study, a numerical approach for analyzing the internal status of Molten CoreConcrete Interaction (MCCI) has been developed based on Moving Particle Semi-implicit (MPS) method. Among the key required models, such as accurate viscosity interaction model for solidifying particles and interface tension models of different liquid phases, preliminary attempts have been made with new models. Namely, a simple mixing model and gas hosting particle model has been implemented to simulate the experiment with affordable calculation cost. The analysis results for VULCANO VF-U1 experiment have shown the possible mechanisms responsible for the characteristic distribution of the solidified metallic corium, which seemed to be highly dependent on the density of surrounding oxidic corium
Abstract
In this study, a numerical approach for analyzing the internal status of Molten CoreConcrete Interaction (MCCI) has been developed based on Moving Particle Semi-implicit (MPS) [...]
- 5
- read
Stress Analysis of Soil Beneath Grouser Wheel for Planetary Rover by Using Discrete Element Method
S. Ono, R. Lichtenheldt, K. Yoshida

particles2021.

Abstract
Modeling the interaction between rover's wheel and soft terrain is of great importance in predicting or evaluating wheel performance for lunar and planetary rovers. The current wheel-soil interaction models predict or evaluate wheel performance under certain conditions. However, most of them do not consider the soil flow and deformation, and thus, they cannot capture the physical phenomena of wheel-soil interaction. Developing a new model that includes such physical phenomena contributes to the improvement of prediction accuracy. To develop such a model, it is necessary to analyze soil flow and deformation beneath the wheel. This study analyzes the stress distributions in the soil and soil flow fields beneath the grouser wheel by performing experiments using the discrete element method (DEM) with the particle simulation tool "Sir partsival". In addition to the single wheel simulation, two simple test simulations - an angle of repose test and a shear test - are performed to confirm the soil flow fields and stress distributions in the soil. In the field of fluid dynamics, (shear) stress generally exists along high gradients of flow velocity. These two tests confirm if the soil stress shows the same trend. The wheel simulations are performed under several slip conditions to investigate their influences on soil flow characteristics. The shape of the soil flow region - the shape of the slip line - can be divided into two patterns depending on the slip conditions. The stress increases along the slip line in all simulations. The findings of this study contribute to understanding the relationship between soil velocity field and stress distribution in the soil.
Abstract
Modeling the interaction between rover's wheel and soft terrain is of great importance in predicting or evaluating wheel performance for lunar and planetary rovers. The current [...]
- 5
- read
Grain deformability influence on the fracture behaviour of rock
N. Azevedo, M. Farinha

particles2021.

Abstract
It is known that the initially proposed circular/spherical rigid particle models are not able to match the ratio of the compressive strength to tensile strength that occurs in rock and the predicted macroscopic friction angle was much lower than the known hard rock experimental values. For this reason, several enhancements have been proposed to address these issues, namely the use of a clumped particle logic, the increase of the number of contacts per particle, the adoption of polygonal/polyhedral grain structures. A flexible 2D DEM based particle model that allows deformable particles to interact in a simplified away is presented. The flexible particle model is tested using biaxial tests and Brazilian tests. The results obtained are compared with those obtained with a rigid particle model with similar contact strength properties and with a flexible particle model, where the flexibility is due to the inner discretization of the grain with smaller particles. The results show that the proposed flexible particle model can predict a behaviour similar to a flexible particle model through inner particle discretization that is more computationally demanding. It is also shown that when compared with a rigid model, the flexible model predicts more reasonable indirect tensile strength to direct tensile strength ratio and requires a smaller value of contact fracture energy to give a good agreement with known experimental data.
Abstract
It is known that the initially proposed circular/spherical rigid particle models are not able to match the ratio of the compressive strength to tensile strength that occurs [...]
- 13
- read
Coupling of non-Newtonian meshless flow with structural solvers
M. Bašic, B. Blagojevic, B. Klarin, J. Bašic

particles2021.

Abstract
-Non-Newtonian fluids and granular flows may be simulated as continuums with large time steps in the meshless Lagrangian context, using the novel method. -Coupling of non-Newtonian meshless Lagrangian Differencing Dynamics (LDD) flow solver and Finite Element Method (FEM) solver. -The flow solver is volume–conservative, second–order accurate, and works directly on triangulated geometry.
Abstract
-Non-Newtonian fluids and granular flows may be simulated as continuums with large time steps in the meshless Lagrangian context, using the novel method. -Coupling of non-Newtonian [...]
- 11
- read
Optimizing the Shape of Planetary Rover Wheels using the Discrete Element Method and Bayesian Optimization
L. Stubbig, R. Lichtenheldt

particles2021.

Abstract
The MMX Rover is a contribution by CNES and DLR to JAXA's Martian Moons eXploration (MMX) mission and will explore the surface of the Mars moon Phobos. As there haven’t been any successful landers on Phobos, little is known about the conditions on the moon’s surface. Additionally, the gravity on Phobos is only about 1/2000 of Earth’s gravity and the behavior of regolith in such low gravity is still a topic of active research. In order to design a suitable wheel for the MMX Rover, we made worst-case assumptions about the soil conditions and implemented them in a simulation model using the Discrete Element Method. This simulation is then used within an optimization loop that automatically tests different wheel shapes on their suitability for reliable locomotion on Phobos. The result is an optimized wheel shape as well as a dataset showing how different wheel shapes affect wheel performance. These results are now being used to design the wheels for the MMX Rover.
Abstract
The MMX Rover is a contribution by CNES and DLR to JAXA's Martian Moons eXploration (MMX) mission and will explore the surface of the Mars moon Phobos. As there haven’t [...]
- 5
- read
Discrete Element Method to simulate interface delamination and fracture of plasma-sprayed thermal barrier coating
L. Leclerc, F. Ferguen, L. Lamini, M. Mebdoua, G. Mohamed

particles2021.

Abstract
This paper aims at investigating the potential and benefits of the Discrete Element Method (DEM) to predict failure mechanisms leading to interface delamination and fracture in air plasma sprayed Thermal Barrier Coating (TBC) systems. A hybrid lattice-particle approach is proposed to predict residual stress fields due to Coefficient of Thermal Expansion (CTE) mismatch and combined with a mixed-mode Cohesive Zone Model (CZM) to simulate interface delamination during the cooling-down phase. Numer ical calculations are first performed using a unit cell model with a perfectly sinusoidal interface profile, which comes from other contributions, in order to attest the suitability of the proposed DEM-based approach for that purpose. The case of a real microstruc ture is then discussed via an image processing based model which underlines the effect of porosity and surface roughness on the failure mechanism.
Abstract
This paper aims at investigating the potential and benefits of the Discrete Element Method (DEM) to predict failure mechanisms leading to interface delamination and fracture [...]
- 5
- read
Optimal design of particle dampers for structures with low first eigenfrequency under forced vibration
N. Meyer, R. Seifried

particles2021.

Abstract
Lightweight designs are becoming increasingly important these days to reduce energy consumption and natural resources. However, a smaller weight typically causes a decrease in stiffness and non-negligible vibration amplitudes over a wide frequency range. One passive damping technique to reduce such vibrations is the use of particle dampers. Thereby containers attached to a vibrating structure or holes embedded in the vibrating structure are filled with granular material. Due to the structural vibrations, momentum is transferred to the granular material which interacts with each other. As a result, energy is dissipated by impacts and frictional phenomena between the particles. Recently, the rolling attribute of spheres has been used to design efficient particle dampers for low amplitude vibrations. As long as the container’s acceleration stays below the gravitational acceleration, this rolling effect can be used to damp horizontal vibrations efficiently. The description of the damper’s energy dissipation is accurately possible using analytical formulas which are presented here. In this presentation, the workflow for a systematic damper design is presented using the analytical formulas and validated experimentally . A good agreement between analytical and experimental measurements is achieved for an optimized damper, validating the presented approach.
Abstract
Lightweight designs are becoming increasingly important these days to reduce energy consumption and natural resources. However, a smaller weight typically causes a decrease [...]
- 49
- read
Particle Resolved Thermo-Chemical Conversion of Pulverized Coal Clusters.
M. Kiss, M. Bösenhofer, M. Schatzl, M. Harasek

particles2021.

Abstract
Particle clusters form in the turbulent flow of boilers and furnaces when injecting pulverized coal. We study the difference in conversion behavior between a pul verized coal cluster and a single char particle. The simulations are done using a detailed particle model in OpenFOAM.The detailed particle model is capable of spatially resolv ing char particles and solving transport equations for heat and mass inside the particles. Furthermore, a surface chemistry model is employed for modeling gas-solid reactions in side the pores of the particles. The char particles are coupled to the surrounding bulk fluid phase using explicit Robert-Neuman coupling. 2-D simulations are carried out for a cluster of 16 particles and a single particle. Both simulations use the same initial con ditions, boundary conditions and particle properties. The results indicate that a lack of oxygen penetration toward the center of the particle cluster alters the thermo-chemical conversion behavior when compared to the single particle. On average this leads to a decrease of the thermo-chemical conversion rates for particles in the cluster, resulting in a reduction of solid carbon consumption compared to the same number of single particles.
Abstract
Particle clusters form in the turbulent flow of boilers and furnaces when injecting pulverized coal. We study the difference in conversion behavior between a pul verized coal [...]
- 3
- read