Documents published in 2023 : Scipedia

Cellular Automata Simulation of Fully Equiaxed Microstructure Formation in Scalmalloy® during Additive Manufacturing with Adjustable Ring Mode Laser
M. Mohebbi, V. Ploshikhin

SIM-AM2023.

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

SIM-AM2023.

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

SIM-AM2023.

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

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

SIM-AM2023.

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

SIM-AM2023.

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

SIM-AM2023.

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

SIM-AM2023.

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

SIM-AM2023.

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

SIM-AM2023.

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

SIM-AM2023.

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

SIM-AM2023.

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

SIM-AM2023.

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

SIM-AM2023.

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

coupled2023.

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

coupled2023.

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

coupled2023.

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

coupled2023.
- 0
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A New Paradigm for Multiphysics Simulation: Its Initial Application to Fluid-Structure Interaction
K. Park, J. González

coupled2023.

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

J. of Dawn. R. (2023). Vol. 5, 8

Abstract
The real number integer exponents of the imaginary unit, 'i' has 4 possible values—i, -1, -i, -1. Traditional method to find such values without the use of computational devices, such as calculators and computers, require splitting the exponent to simpler numbers, which can be quite burdensome if the exponent is of very large value, like 38127938127. This paper presents a simple three-step algorithm for quickly computing large exponents of the imaginary unit 'i,' explained in a way that even the non-mathematicians will be able to understand it. This method simplifies complex number exponentiation, turning minutes of hard calculation into seconds with minimal effort, and can serve as an extremely effective tool in mental mathematical calculations. The algorithm combines the real/imaginary determination, division by 2 (and subtraction by 1 if odd) and sign determination, using only last two digits of the exponent. We further prove our method using modular arithmetic and demonstrate it using examples.
Abstract
The real number integer exponents of the imaginary unit, 'i' has 4 possible values—i, -1, -i, -1. Traditional method to find such values without the use of computational [...]
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CECM: A continuous empirical cubature method with application to the dimensional hyperreduction of parameterized finite element models
J. Hernández, J. Bravo, S. Parga

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

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

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

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

membranes2023.
- 3
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Form-finding of lightweight tension-compression structures with equilibrium-based graphical methods
P. D'Acunto

membranes2023.
- 0
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50 Years of Form Finding by the Force Density Method
K. Bletzinger

membranes2023.
- 8
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Thinking to close the loop in membrane architecture
C. Monticelli

membranes2023.
- 5
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The Evolution in the Design Tools for Membrane Structures
P. Beccarelli

membranes2023.
- 106
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Progressive Damage in thin 2D Woven CFRP Laminates due to Stress Concentrations at Free Edges and Notches
L. Heinzlmeier, S. Siberer, C. Kralovec, M. Schagerl, T. Wolfsgruber

composites2023.

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

composites2023.

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

composites2023.

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

composites2023.

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

composites2023.

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

composites2023.

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

composites2023.

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

composites2023.

Abstract
The CFRP wing box section under investigation is a stringer less wing-box (develop within the OPTICOMS research project) and consists of two portions: an upper part, made of co-cured spars and a top skin panel, and a bottom cured skin panel. The two portions are joined with a bonding process, giving rise to the final wing-box. During that final assembly step, distributed fibre optics were embedded between the spar caps and the bottom skin panel along the bonding lines. The embedded FO consists of six distributed fibres running within the bonding layer for about 1 m along the span direction. An irregular damage map was defined, by simulating the presence of manufacturing bonding defects by the intersection of teflon patches, different for width and length, to check an SHM system capabilities in detecting such flaws. The SHM system was tested after the final bonding process, by exploring the info contained within the “residual strains” data of the unloaded structure. Results obtained by post processing data for each fibre optic, are reported. The damage index associated to the eligible sensors is provided. Based on the available data, the SHM algorithm appeared to be sensible enough to hundreds of microstrain signals. Concerning faults detection, sensor density seems a key. Errors in the estimate of the damage extension can be assessed to be around 25%
Abstract
The CFRP wing box section under investigation is a stringer less wing-box (develop within the OPTICOMS research project) and consists of two portions: an upper part, made [...]
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Application of Model-based Design Approach on Dynamic Tensile Testing of Carbon/Epoxy Composites at Intermediate Strain Rates
S. Yoo, E. Kim, N. Toso, H. Voggenreiter

composites2023.

Abstract
The reliable strain rate-dependent material properties at intermediate strain rate levels (1-200 s-1 ) are crucial for an accurate crashworthy design of fibre-reinforced polymer (FRP) composite structures. However, the presence of unacceptable oscillations in measured force signals hinders the precise identification of the dynamic mechanical response of materials. The current work reports the results of gained in an initial study using a novel numerical model developed through a Model-based Design (MBD) approach. A multi-degree of-freedom (MDOF) mass-spring-damper model is employed to investigate the dynamic characteristics of a whole experimental test setup to gain insights into the dynamic interaction between the test machine and the test specimen. The developed model was calibrated by the results from dynamic tension testing of Aluminium Alloy 2024-T3. Then, the model parameters were optimised using a genetic algorithm (GA). Subsequently, the adaptability of the developed model to carbon/epoxy composites, IM7/8552, was examined. The proposed model is promising to identify the influence of the test setup on the measurements and effectively distinguish excessive oscillations caused by its inertial effect at intermediate strain rate levels. The model will offer a robust solution to identify oscillations and, therefore, expand the testing capabilities to a broader range of strain rates.
Abstract
The reliable strain rate-dependent material properties at intermediate strain rate levels (1-200 s-1 ) are crucial for an accurate crashworthy design of fibre-reinforced polymer [...]
- 29
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Tensile Testing of Pinned Hybrid CFRP/Titanium Joints and Damage Monitoring with Electrical Resistance Measurements
A. Dengg, C. Kralovec, M. Schagerl

composites2023.

Abstract
This contribution presents a new evaluation approach for Structural Health Monitoring of a pinned hybrid CFRP/titanium single-lap shear joint with the help of direct current electrical resistance measurements. The result is a dimensionless, load-independent damage indicator that is similar to an already developed evaluation approach by the authors but is simpler and more robust in comparison. Readily published test data is re-evaluated with the new evaluation approach and compared with the existing structural as well as the electrical resistance results. Finally, further test setup improvements for future tests are discussed.
Abstract
This contribution presents a new evaluation approach for Structural Health Monitoring of a pinned hybrid CFRP/titanium single-lap shear joint with the help of direct current [...]
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Effect of Ply Thickness on Dynamic Damage Progression in Cross-ply Laminates Under Low-velocity Impact
O. Batmaz, D. Coker

composites2023.

Abstract
: In this study, we have conducted in-situ LVI experiments on cross-ply CFRP beams having stacking layups [04/904/02]s and [02/902/02/902/02]s. The progression of damage is observed through high-speed photography. In addition to LVI, quasi-static indentation (QSI) experiments are performed to reduce challenges in monitoring damage progression during the short impact loading interval. QSI experiments provide magnified in-situ observations on the free edge of the beam using a traveling digital microscope. Numerical simulations of these experiments are carried out using the finite element method in ABAQUS/Explicit. The orthotropic constitutive material model, predicting fiber and matrix damage initiation and evolution, is implemented through a VUMAT subroutine. The comparison between numerical simulations and experimental observations allowed us to investigate the influence of ply clustering on the LVI-induced damage mechanisms.
Abstract
: In this study, we have conducted in-situ LVI experiments on cross-ply CFRP beams having stacking layups [04/904/02]s and [02/902/02/902/02]s. The progression of damage is [...]
- 141
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Investigation of Several Impact Angles for Predicting Bird-Strike Damage in a Riveted eVTOL Composite Wing
E. Kayar, G. Abdelal, B. Falzon, Z. Kazanci

composites2023.
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A 3D Damage Model for Simulating Damage Modes in Fibre Metal Laminates
I. Abuzayed, J. Curiel, N. Wiravan, C. Zhang

composites2023.

Abstract
This paper presents a 3D damage model utilized for studying the failure characteristics of GLARE. The current damage model adopted the 3D forms of Hashin’s and Puck’s failure criteria for predicting the onset of failure of fibres and matrix in the composite plies. Whilst the damage evolution is modelled based on the dissipation of fracture energy. In addition, a ductile damage model was employed to study the failure of metal layers and the delamination was assessed via a cohesive interface model. The current damage model was adopted to predict the failure modes and the blunt notch strength of GLARE; where various failure modes were observed, such as Fibre breakage, matrix cracking, delamination and plastic damage of aluminium layers. The model showed strong agreement with experimental results.
Abstract
This paper presents a 3D damage model utilized for studying the failure characteristics of GLARE. The current damage model adopted the 3D forms of Hashin’s and Puck’s [...]
- 77
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Virtual manufacturing of thick composite beams, investigating cure cycle and shrinkage induced stress
J. Vroon, N. van Hoorn

composites2023.

Abstract
Investigating cure shrinkage-induced stress in thick composite beams by virtual manufacturing is the focus of this study. The research aims to understand the behaviour of thick-walled composite structures, particularly in relation to curing shrinkage-induced damages. The curing process of resin is simulated thermally and mechanically to investigate the residual cure-induced stress. The study utilizes a finite element model in Abaqus, considering material properties, mesh, boundary conditions, and user subroutines. Ten different cure cycles are investigated, showing improvements in reducing internal stresses after curing compared to the manufacturer's cycle of about 20%. However, during curing, the investigated cycles provide marginal improvements. This study demonstrates the potential for optimizing cure cycles to reduce internal stresses in thick-walled applications. It is important to note that the proposed method is not experimentally validated and requires accurate measurements for validation.
Abstract
Investigating cure shrinkage-induced stress in thick composite beams by virtual manufacturing is the focus of this study. The research aims to understand the behaviour of [...]
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Free Vibration Analysis of Thermally Prestressed Constant and Variable Stiffness Laminated Beams using Strong Unified Formulation
S. Ojo, G. Zucco, P. Weaver

composites2023.

Abstract
Free vibration analysis is an essential requirement to capture the behaviour of composite structures subject to dynamic loading environment. To enhance the vibratory behaviour of composite structures, variable stiffness (VS) concept offers increased design flexibilities to tailor the structural response to meet a wide range of applications. Mechanically, the increased design space created by VS techniques leads to complexities of non-classical stiffness couplings which necessitate robust computational frameworks with enriched kinematics to predict the dynamic response accurately and efficiently. In this regard, this study proposes an enhanced differential quadrature based Strong Unified Formulation (SUF) to investigate the free vibration behaviour of thermally prestressed constant and variable stiffness composite beams. The proposed SUF model exploits the flexible kinematical description of the Theory of Unified Formulation to combine a hierarchical serendipity Lagrange-based 2D finite element (FE) with 1D differential quadrature method beam element for efficient free vibration characterisation of composite beams induced with prestress at different temperatures. The proposed SUF free vibration solutions of constant stiffness and VS beams demonstrate satisfactory accuracy and achieved improved efficiency with up to 99.9% computational savings when benchmarked against ABAQUS 3D FE solutions. Finally, a numerical study reveals that the effects of thermal prestress significantly contribute to the free vibration response of constant stiffness and VS laminated beams underscoring the importance of the study.
Abstract
Free vibration analysis is an essential requirement to capture the behaviour of composite structures subject to dynamic loading environment. To enhance the vibratory behaviour [...]
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On the Importance of Fibre Direction Mesh Alignment for Artificial Lightning Strike Simulations
S. Millen, B. Navagel, A. Murphy

composites2023.

Abstract
Composite materials, used in primary aircraft structures, produce weight reduction and improved fuel efficiency over legacy metal airframes but are more susceptible to lightning strike damage. Therefore, research into lightning strike damage and protection systems, through experiments and simulations, is an important research topic. For any FE simulation appropriate representation of the material behaviour, the loading and boundary conditions are key to accurate predictions. In addition, an aspect which has been under reported in many studies is the meshing strategy. Fibre direction mesh alignment has been reported to yield more accurate results in the modelling of mechanical damage (intralaminar damage initiation and propagation) in unidirectional fibre reinforced composite structures. However, this model meshing strategy has not found wide application and has not been used for the modelling of thermal damage events, e.g. lightning strike direct effect simulation. Instead, authors have typically refined the mesh around the arc attachment area. This paper, for the first time, examines the influence of fibre direction mesh alignment for artificial lightning strike simulations and the prediction of thermal damage. Initially, the mesh alignment is introduced partially in the central region of the specimen. The paper uses a mature modelling approach with a transient, fully coupled, thermal-electric step in ABAQUS with a lightning test Waveform A (40 kA, 4/20 µs) applied to the specimen. Specimen boundary conditions match those typically used in experiments and a mesh convergence study is undertaken to ensure no element size influence on the results. The use of this meshing strategy has been shown to significantly improve the prediction of both moderate and severe thermal damage profiles, when compared with the standard meshes used in previous research. The predicted moderate (2659 mm2 vs 2833 mm2 ) and severe (1059 mm2 vs 1061 mm2 ) damage areas were improved to within 4% and 1% of experimental results, respectively, using this meshing strategy.
Abstract
Composite materials, used in primary aircraft structures, produce weight reduction and improved fuel efficiency over legacy metal airframes but are more susceptible to lightning [...]
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Coupled problems in bio-inspired robotics
A. Simone

coupled2023.
- 7
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Determinants of invoice currency selection by Russian exporters
D. Kuznetsov

RUSSIAN PRESIDENTIAL ACADEMY OF NATIONAL ECONOMY AND PUBLIC ADMINISTRATION (2023). 220

Abstract
The presented paper empirically accesses the determinants of invoice currency choice by Russian exporters. The relevance of the work is dictated by the sanctions imposed against Russia, which, among other things, make international settlements in the dominant currencies difficult and facilitate the transition of Russian exporters and importers to settlements in other currencies. The existing economic literature considers the invoice currency as one of the most important factors of the magnitude of the exchange rate passthrough into prices and quantities. The basic assumption of such models is short-term price rigidity in terms of invoice currency, which is in line with the data. The dominant view is that the choice of contract currency made by exporters based on the desired medium-term exchange rate pass-through, which in turn depends on company’s share in the market and the intensity of imported components using. In this paper using the detailed data of customs statistics of the Russian Federation it is show that key determinants of the Russian exporter’s contract currency choice are the competitor’s choice of the contract currency, the firm’s market share, the invoice currency import structure and firm productivity, as well as the degree of differentiation of the exported product. The main conclusion is that the currency structure of export payments will change due to changes in the currency structure of imports, and in many product markets the short-term stability of the share of Russian exporters will suffer, including due to difficulties in using the US dollar as the currency for nominating exports.
Abstract
The presented paper empirically accesses the determinants of invoice currency choice by Russian exporters. The relevance of the work is dictated by the sanctions imposed against [...]
- 0
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Import Price Reaction to the Ruble Exchange Rate and Leaving the Russian market by Foreign Suppliers
A. Firanchuk

RUSSIAN PRESIDENTIAL ACADEMY OF NATIONAL ECONOMY AND PUBLIC ADMINISTRATION (2023). 221

Abstract
The aim of the work is an empirical analysis of the ruble exchange rate pass-through into prices under reorientation of imports to suppliers from neutral countries due to the withdrawal of some suppliers from the Russian market. The motivation is related to the structural transformation of Russian foreign trade and the continued volatility of the ruble exchange rate. I collected a database of Russian imports based on statistics of the main trading partners. The data shows three periods since February 2022: a drop of import flows from all countries in February-April 2022; a period of reorientation (increase) of imports from neutral countries in May – December; and following general stabilization of trade. The result of econometric analysis at commodity-group level consistent with the hypothesis of reorientation of imports: the average growth rates of import prices from 'unfriendly' countries during the considered period significantly exceed the rate of price growth in the pre-crisis period. The difference is from 1.9 to 4.9 percentage points in a year basis. At the same time, there is no evidence in favor of the hypothesis of an increase in the growth rate of import prices from neutral countries during the crisis period. The main conclusion is that, by the end of 2022, the ruble exchange rate pass-through into import prices returned to the characteristic values of previous periods. This suggests that the current weakening of the ruble will affect import prices and lead to a reduction of imports volumes. The period of turbulence and reorientation of Russian imports has ended. Its result was a multiple drop in imports from 'unfriendly' countries and a higher increase in the prices of imports from them.
Abstract
The aim of the work is an empirical analysis of the ruble exchange rate pass-through into prices under reorientation of imports to suppliers from neutral countries due to [...]
- 1
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FEM Simulations for Nonlinear Multifield Coupled Problems: Application to thixoviscoplastic flow
N. Begum, A. Ouazzi, S. Turek

coupled2023.

Abstract
In this note, we are concerned with the solvability of multifield coupled problems with different, often conflictual types of non-linearities. We bring into focus the challenges of getting EFM numerical solutions. As for instance, we share our investigations of the solvability of thixoviscoplastic flow problems in FEM settings. On one hand, nonlinear multifield coupled problems are often lacking unified FEM analysis due to the presence of different nonlinearities. Thus, the importance of treating auxiliary subproblems with different analysis tools to guarantee existence of solutions. Moreover, the nonlinear multifield problems are extremely sensitive to the coupling. On other hand, monolithic Newton-multigrid FEM solver shows a great success in getting numerical solutions for multifield coupled problems. Thixoviscoplastic flow problem is a perfect example in this regard. It is a two field coupled problem, by means of microstructure dependent plastic-viscosity as well as microstructure dependent yield stress, and microstructure and shear rate dependent buildup and breakdown functions. We adapt different numerical techniques to show the solvability of the problem, and expose the accuracy of FEM numerical solutions via the simulations of thixoviscoplastic flow problems in channel configuration.
Abstract
In this note, we are concerned with the solvability of multifield coupled problems with different, often conflictual types of non-linearities. We bring into focus the challenges [...]
- 0
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Modified Kirsch Problem Incorporating Surface Stresses under Plane Stress
A. Vakaeva, M. Grekov

coupled2023.

Abstract
We consider the Kirsch problem, taking into account the surface stresses at the boundary of the circular hole and on the front surfaces of the plate, in the framework of the original Gurtin–Murdoch model. The boundary conditions on the cylindrical surface of a circular hole in a nanoplate are derived in terms of a complex variable in the case of the plane stress state. The solution of the two-dimensional problem for an infinite plane with a circular hole under remote loading is explicitly obtained. Based on the analytical solution, we investigated the dependence of the elastic stress field on the nanosised plate thickness and dimension of the hole. Numerical examples are given in the paper to illustrate quantitatively the effect of the plate thickness at the nanoscale on the stress field at and near the cylindrical surface. The results are presented graphically as the dependence of the components of the stress tensor on the polar angle.
Abstract
We consider the Kirsch problem, taking into account the surface stresses at the boundary of the circular hole and on the front surfaces of the plate, in the framework of the [...]
- 46
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On Numerical Simulation of Fluid - Structure- Acoustic Interactions Related to Human Phonation Process
P. Sváček, J. Valášek

coupled2023.

Abstract
This paper focus on mathematical modelling and numerical simulation of human phonation process. The mathematical FSI model is presented consisting of the description of the structural model, the flow model and the coupling conditions. In order to treat the VFs contact, the problem of the glottis closure is addressed. To this end several ingredients are used including the use of suitable boundary conditions, modification of the flow model and robust mesh deformation algorithm. The FSI model is extended to FSAI problem by inclusion of the Lighthill model of aeroacoustics. The numerical approximation of the problem is presented and several numerical results are shown.
Abstract
This paper focus on mathematical modelling and numerical simulation of human phonation process. The mathematical FSI model is presented consisting of the description of the [...]
- 10
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X-Mesh: A new approach for the simulation of two-phase flow with sharp interface
J. Remacle

coupled2023.
- 9
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Sound Insulation Optimization of a Roller Shutter Box
S. Bakhnouche, W. Larbi, J. Deü, P. Macquart

coupled2023.

Abstract
This research aims to develop an advanced numerical model to accurately predict and optimize the acoustic insulation performance of roller shutter boxes, which are important for thermal and acoustic insulation in building facades. Traditional laboratory tests for evaluating sound transmission can be expensive and lack repeatability, particularly at low frequencies. To overcome these limitations, the proposed numerical approach utilizes the finite element method to model solid and fluid domains within the roller shutter box structure. Poroelastic layers are accounted for using a mixed displacement-pressure formulation of the Biot poroelasticity equations. Excitation and sound radiation are simulated using a diffuse field of plane waves with random phases and directions, employing the infinite elements method. The numerical model is validated by comparing its results with laboratory tests, which are described in detail. The practical application of this numerical method includes investigating factors such as assembly conditions, positioning of poroelastic layers, and the inclusion of heavy masses on the acoustic behavior of roller shutter boxes.
Abstract
This research aims to develop an advanced numerical model to accurately predict and optimize the acoustic insulation performance of roller shutter boxes, which are important [...]
- 42
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Global sensitivity analysis of sound transmission loss of double-wall with porous layers
S. Bakhnouche, R. Aloui, W. Larbi, J. Deü, P. Macquart

coupled2023.

Abstract
This study examines the acoustic performance of a double-wall system with a porous layer and conducts a global sensitivity analysis of sound transmission loss. The authors use the transfer matrix method to predict sound transmission, which provides cost-effective modeling of complex acoustic interactions and detailed high-frequency information. The method employs transfer matrices to represent sound wave propagation in each layer, considers material characteristics and layer thickness, and incorporates interface matrices for boundary conditions. The poroelastic layer is modeled using the Biot-Allard approach with nine parameters. Morris and Sobol methods are applied for global sensitivity analysis, identifying significant parameters. The investigation focuses on eleven parameters, including foam properties and layer thicknesses. The findings indicate the impact of geometric parameters at lower frequencies and foam properties at higher frequencies. This study is the first to optimize sound transmission in double-wall systems with porous layers using sensitivity analysis methods, offering insights for system behavior and design
Abstract
This study examines the acoustic performance of a double-wall system with a porous layer and conducts a global sensitivity analysis of sound transmission loss. The authors [...]
- 105
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Coupled Simulations of Extreme Fluid-Structure Dynamics
V. Aune, G. Valsamos, F. Casadei

coupled2023.

Abstract
This work presents ongoing research on the influence of fluid-structure interaction (FSI) effects on the ductile crack growth in blast-loaded steel plates. Thin steel plates with Xshaped, pre-formed defects are used to allow for large, inelastic strains and ductile fracture. FSI effects were studied by comparing the numerical predictions of the uncoupled and the coupled FSI approach, where experimental data served as a backdrop to evaluate the accuracy of the numerical simulations. Numerical simulations are conducted in the EUROPLEXUS software. The clear conclusion from this study is that ductile fracture and crack propagation are influenced by FSI effects during the dynamic response of the plate. That is, the crack growth was very sensitive to the actual loading on the plate. Moreover, because the increase in CPU cost may be significant when uniformly refining the mesh, adaptive mesh refinement (AMR) was found very promising in reducing the CPU cost and maintaining the solution’s accuracy. The performance of AMR is an interesting finding in the view of numerical simulations of coarsely meshed (prior to AMR) shell structures exposed to blast loading
Abstract
This work presents ongoing research on the influence of fluid-structure interaction (FSI) effects on the ductile crack growth in blast-loaded steel plates. Thin steel plates [...]
- 0
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Layered Model of Fluid-Structure Interaction in Dry Wire Drawing with Coupled Axial Velocity
M. Vervaecke, D. Fauconnier, J. Degroote

coupled2023.

Abstract
An innovative 2D axisymmetric fluid-structure interaction model of wire drawing is developed to numerically investigate the interaction between the thin lubricant film and the plastically deforming steel wire. The deformation of the wire is obtained from the linear momentum balance and the lubricant film has been calculated by the Navier-Stokes equations. Moreover, the coupling between wire and lubricant is performed by the IQN-ILS technique and a no-slip condition is imposed on the sliding fluid-structure interaction interface. In order to reduce the computational cost, a layering technique is implemented in the axially moving structure domain. This results on the one hand in monitoring the stresses and displacements of the structure and on the other hand in an observation of the hydrodynamic pressure build-up and wall shear stresses in the lubricant. Additionally, the evolution of the fluid film thickness is presented.
Abstract
An innovative 2D axisymmetric fluid-structure interaction model of wire drawing is developed to numerically investigate the interaction between the thin lubricant film and [...]
- 0
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Implicit Schur complement iterative modal solvers for multiphysics model order reduction
G. Buron, F. Thouverez, L. Jézéquel, A. Beley, F. Thévenon

coupled2023.

Abstract
In this work, we propose iterative modal solvers to generate multiphysics finite element reduced order models. We consider the strongly coupled problems defined through differential-algebraic equations with sparse discrete operators. Piezoelectric models are common examples of such problems. The approach we propose is based on the Model Order Reduction (MOR) after Implicit Schur method [1] which is used for the Krylov subspace reduction of piezoelectric devices. While their work uses the knowledge of the loading applied to the model to generate a Krylov subspace reduction basis, we propose to build a reduction basis with a priori unknown loading by modal synthesis. The basis is built from the eigenvectors of the problem after the static condensation by Schur complement of one of the physics. Typically, the Schur complement matrix is computed explicitly and it leads to dense operators [2] which limit the problem scales that can be studied due to large memory requirements and costly computations for the eigensolver used afterward. For Krylov-based eigensolvers, the most computationally difficult step is to obtain a basis spanning the eigenspace of the problem on the considered eigenvalue range. By generalizing the MOR after Implicit Schur method, this basis can be constructed by an iterative procedure using the original sparse operators instead of the dense condensed operators. The original model may be significantly larger compared to the condensed model for typical cases. However, keeping the sparsity is a critical computational advantage for the considered problems. This method is minimally intrusive for the eigensolvers that only require the implementation of a matrix-vector product. Comparing this implicit Schur complement approach to the explicit Schur complement approach shows large computational cost reductions. It also underlines the problem scale limitations of the explicit approach even on high performance computing hardware.
Abstract
In this work, we propose iterative modal solvers to generate multiphysics finite element reduced order models. We consider the strongly coupled problems defined through differential-algebraic [...]
- 5
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Time adaptive Waveform-Relaxation methods for Fluid Structure Interaction
P. Birken, N. Kortasky

coupled2023.

Abstract
We consider waveform iterations for dynamic coupled problems with respect to the role of time window length. We review existing theoretical results about the error of waveform iterations and the role of the time window length. Furthermore, we present numerical results for waveform iterations with both time adaptive sub solvers and with fixed time steps. This way, we are able to give a recommendation on the choice of the time window. The use of time windows can lead to an increase in efficiency. For fixed time grids, we can reliably achieve a small performance increase. For time adaptive solvers, more research is needed.
Abstract
We consider waveform iterations for dynamic coupled problems with respect to the role of time window length. We review existing theoretical results about the error of waveform [...]
- 58
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The effect of the number of subproblem iterations in partitioned fluid-structure interaction simulation
N. Delaissé, T. Spenke, N. Hosters, J. Degroote

coupled2023.

Abstract
In a partitioned fluid-structure interaction simulation separate flow and structure solvers, each with their own spatial domain, are coupled by exchanging data on the common interface. Its computational cost is dominated by the execution of these solvers, and the cost associated with the coupling algorithm and communication are often deemed negligible. From this point of view, the computational cost is in literature typically expressed by the number of required coupling iterations per time step or equivalently the number of solver executions. However, this reasoning implicitly assumes a constant solver cost and ignores the varying number of internal subproblem iterations, i.e., solver iterations in the nonlinear solvers. This work addresses this shortcoming and shows that the computational cost of a partitioned fluid-structure interaction simulation is significantly impacted by the number of subproblem iterations performed in each solver call. Specifically, it is demonstrated that performing subproblem iterations until the solver is fully converged in each call does typically minimize the number of coupling iterations, but does not lead to minimal computational time. Instead, under the assumption of constant subproblem iteration cost, the optimum is found by minimizing a weighted sum of both coupling and subproblem iterations. The weighting factors are determined by the problem itself as well as the computer architecture.
Abstract
In a partitioned fluid-structure interaction simulation separate flow and structure solvers, each with their own spatial domain, are coupled by exchanging data on the common [...]
- 0
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Introducing a cloud-based framework for creating, visualising, testing and automating complex simulation workflows
O. Stodieck

coupled2023.

Abstract
Engineers increasingly need tools that help them automate complex simulation workflows. Besides performance, robustness and usability requirements, tools should also be easily accessible. To fulfil these requirements, Dapta Ltd is developing a cloud-based framework, which is designed to be an all-in-one solution to create, visualise, test and automate simulation workflows. Here we demonstrate the use of the dapta platform with open-source software libraries, focusing on an FSI multiphysics example.
Abstract
Engineers increasingly need tools that help them automate complex simulation workflows. Besides performance, robustness and usability requirements, tools should also be easily [...]
- 12
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Multistep interface coupling for high-order adaptive black-box multiphysics simulations
L. François, M. Massot

coupled2023.

Abstract
Many multiphysics problem can be described by the coupling of several models through physical surfaces. Relying on existing model-specific solvers is very desirable, however they must be coupled in a way that ensures an accurate and stable coupled simulation. In this contribution, we present a multistep coupling scheme which relies on the history of the exchanged quantities to enable a high-order accurate coupling with time adaptation. Explicit and implicit variants are discussed in details. Numerical experiments conducted with an opensource demonstrator on a conjugate heat transfer problem show that high-order convergence is attained, and that stability is favourable compared to other classical approaches.
Abstract
Many multiphysics problem can be described by the coupling of several models through physical surfaces. Relying on existing model-specific solvers is very desirable, however [...]
- 0
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Partitioned MPM-FEM Coupling Approach for Advanced Numerical Simulation of Mass-Movement Hazards Impacting Flexible Protective Structures
V. Singer, A. Laresse, R. Wüchner, K. Bletzinger

coupled2023.

Abstract
The intensity and frequency of natural hazards such as landslides, debris flow, and mud flows have increased significantly over the last years due to climate change and global warming. These catastrophic events are responsible for numerous destructions of infrastructures and landscapes and often even claim human lives. Therefore, in addition to the prediction, the design and installation of protective structures are of tremendous importance. In recent decades, highly flexible protective structures have been favored due to their enormous energy absorption capacity while adapting well to the environment. However, dimensioning such protective structures is a very complex task requiring advanced numerical simulation techniques. To capture the behavior of such natural hazards on the one hand and the highly flexible protection structures, including complex elements such as sliding cables or brakes on the other hand, a partitioned coupling approach is proposed in this work. This way, the most appropriate solvers, treated as black-box solvers, can be selected for each physics involved while the interaction is shifted to the shared interface.
Abstract
The intensity and frequency of natural hazards such as landslides, debris flow, and mud flows have increased significantly over the last years due to climate change and global [...]
- 0
- read
Partitioned MPM-FEM Coupling Approach for Advanced Numerical Simulation of Mass-Movement Hazards Impacting Flexible Protective Structures
V. Singer, A. Laresse, A. Börst, R. Wüchner, K. Bletzinger

coupled2023.

Abstract
The intensity and frequency of natural hazards such as landslides, debris flow, and mud flows have increased significantly over the last years due to climate change and global warming. These catastrophic events are responsible for numerous destructions of infrastructures and landscapes and often even claim human lives. Therefore, in addition to the prediction, the design and installation of protective structures are of tremendous importance. In recent decades, highly flexible protective structures have been favored due to their enormous energy absorption capacity while adapting well to the environment. However, dimensioning such protective structures is a very complex task requiring advanced numerical simulation techniques. To capture the behavior of such natural hazards on the one hand and the highly flexible protection structures, including complex elements such as sliding cables or brakes on the other hand, a partitioned coupling approach is proposed in this work. This way, the most appropriate solvers, treated as black-box solvers, can be selected for each physics involved while the interaction is shifted to the shared interface.
Abstract
The intensity and frequency of natural hazards such as landslides, debris flow, and mud flows have increased significantly over the last years due to climate change and global [...]
- 0
- read
A certified wavelet-based physics-informed neural network for the solution of parameterized partial differential equations
L. Ernst, K. Urban

coupled2023.

Abstract
Physics Informed Neural Networks (PINNs) have frequently been used for the numerical approximation of Partial Differential Equations (PDEs). The goal of this paper is to construct PINNs along with a computable upper bound of the error, which is particularly relevant for model reduction of Parameterized PDEs (PPDEs). To this end, we suggest to use a weighted sum of expansion coefficients of the residual in terms of an adaptive wavelet expansion both for the loss function and an error bound. This approach is shown here for elliptic PPDEs using both the standard variational and an optimally stable ultra-weak formulation. Numerical examples show a very good quantitative effectivity of the wavelet-based error bound.
Abstract
Physics Informed Neural Networks (PINNs) have frequently been used for the numerical approximation of Partial Differential Equations (PDEs). The goal of this paper is to construct [...]
- 0
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Multiphysical Modeling of Soft Tissue-Stent Interaction
S. Reese, K. Manjunatha, J. Shi, M. Sesa

coupled2023.

Abstract
The prevalence of in-stent restenosis after percutaneous coronary intervention necessitates the development of computational tools to derive pathophysiological inferences and finetune interventional procedures patient-specifically. In this context, a multiphysics framework is presented herein that captures the chemo-mechano-biological interaction involved. Strategies that could potentially accelerate the computations as well as add versatility to them are shortly discussed. We hence take a minute step towards enabling computer-assisted clinical practices.
Abstract
The prevalence of in-stent restenosis after percutaneous coronary intervention necessitates the development of computational tools to derive pathophysiological inferences [...]
- 0
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On the 2D-1D Coupling in Numerical Simulations of Simplified Air Flow Model in Human Airways
coupled2023.

Abstract
This paper presents selected results regarding the implementation, validation and testing of a simple 2D-1D coupled model designed to capture some essential features of the oscillatory air flow in human respiratory system. The model relies on a 2D flow model solved by a simple finite-difference scheme in the immersed boundary setting. The incompressible fluid flow from this model is coupled to a simplified 1D fluid-structure-interaction model simulating the flow in a tube with elastic walls. Some first results obtained using the coupled 2D-1D model in an oscillating (Womersley-like) type of flow are presented and discussed in detail. The influence of model parameters is explored for a range of physically relevant settings.
Abstract
This paper presents selected results regarding the implementation, validation and testing of a simple 2D-1D coupled model designed to capture some essential features of the [...]
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Assessing Scaling and Kinematic Errors in a Coupled Experimental-Computational Infant Musculoskeletal Model
T. Chambers, C. Walck, V. Huayamave, E. Mannen

coupled2023.

Abstract
Musculoskeletal models are valuable tools that enable the study and quantification of biomechanical parameters, allowing researchers to better understand the mechanisms influencing or contributing to human movement. Furthermore, musculoskeletal models have the potential to serve as diagnostic tools for identifying pathologies and disorders, such as developmental dysplasia of the hip. However, current musculoskeletal models are developed using adult subjects, with only a few studies focusing on infant populations, despite the greatest growth rate being in early infancy. Therefore, the objective of this study was to evaluate the impact of multiple linear scaling approaches of increasing complexity on the development of an infant musculoskeletal model. Motion capture technology was used to collect data from the spontaneous kicking movement of a 2.4-month-old infant lying supine. The experimental motion capture data and anthropometric measurements were used to scale the generic gait2392 OpenSim model. Four linear scaling methods of increasing complexity were used: uniform (Uni), nonuniform (Non), nonuniform with knee and ankle joint centers (NAKJCs), and nonuniform with knee, ankle, and regression-derived hip joint centers (NHJCs). Results suggest that the maximum marker errors decreased with the increasing complexity of the scaling approach. The Uni scaling approach resulted in the largest scaling and kinematic errors, with maximum marker errors of 4.92 cm and 5.30 cm, respectively. The NHJCs scaling approach had the lowest maximum marker errors, with errors of 4.17 cm and 4.36 cm, respectively. The scaling method used to develop infant musculoskeletal models should be considered carefully, especially when using linearly scaling generic models developed using adult cadaveric data.
Abstract
Musculoskeletal models are valuable tools that enable the study and quantification of biomechanical parameters, allowing researchers to better understand the mechanisms influencing [...]
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A Novel Musculoskeletal-driven Exoskeleton Framework for Spina Bifida Rehabilitation in Infants
V. Huayamave, T. Chambers, E. Vela, W. Kim, E. Centero, B. Macumber

coupled2023.

Abstract
Soft exoskeletons are lightweight robotic devices currently used for physical therapy and rehabilitation. Most of the current research on soft exoskeletons has focused on the adult population, providing limited options for infant physical therapy and rehabilitation. Spina bifida, a condition affecting the infant’s brain and spinal cord, requires muscle movement treatment through physical therapy. Coupling physiological infant movement with soft robotics can provide solutions for rehabilitation and physical therapy. This study couples joint kinematics from a novel musculoskeletal model with a soft-robotic exoskeleton that uses vacuum-powered artificial muscles. The accuracy of the exoskeleton is assessed when replicating physiological infant kicks. Knee joint kinematics from the musculoskeletal model during infant movement were used to drive the soft exoskeleton. Preliminary results showed that the robotic system replicated infant kicks with lower frequency and small ranges of motion (RMS < 2 degrees) more accurately than those with higher frequency and large ranges of motion (RMS > 6 degrees). The proposed framework has the potential to replicate physiological infant kicks that could be used for infant physical therapy and rehabilitation.
Abstract
Soft exoskeletons are lightweight robotic devices currently used for physical therapy and rehabilitation. Most of the current research on soft exoskeletons has focused on [...]
- 102
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A mechanobiological bone remodelling model coupling bone physiology and systemic calcium and phosphorus homeostasis
J. Martínez-Reina, J. Calvo-Gallego, F. Gutiérrez-Milán, P. Pivonka

coupled2023.

Abstract
In this work we couple a physiologically based mathematical model of integrated calcium and phosphorus homeostasis to a cell population bone remodelling model and to a pharmacokinetics (PK) - pharmacodynamics (PD) model of denosumab (Dmab), an antiresorptive drug administered to combat osteoporosis (OP). The model of Ca and P homeostasis allows to incorporate the effect of factors such as Ca dietary changes, vitamin D supplementation, concurrence of renal deficiency or hyperparathyroidism into the study of OP and its treatment.
Abstract
In this work we couple a physiologically based mathematical model of integrated calcium and phosphorus homeostasis to a cell population bone remodelling model and to a pharmacokinetics [...]
- 0
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An HPC Multi-Physics Framework for Next-Generation Industrial Aircraft Simulations
E. Fadiga, F. Rondina, T. Benacchio, D. Malacrida, L. Capone, S. Oliani

coupled2023.

Abstract
The aerodynamic performance of industrial aircraft is strongly coupled with the structural deformation under aerodynamic load. Consequently, multi-physics simulations represent an important asset during the design and optimization phases. Most of the Fluid-Structure Interaction (FSI) coupling approaches adopted by researchers and engineers can be divided into monolithic and partitioned techniques. The monolithic coupling, which consists of a unique system of equations for the coupled problem, is usually characterized by higher robustness and easier scalability. However, this approach is inherently customized for specific applications and requires a significant development effort. The partitioned coupling links existing software on a higher level, benefitting from higher flexibility and lower time-to-solution. As the computational world marches towards the exascale, black-box coupling libraries such as preCICE [2] aim to combine the flexibility and user-friendliness of partitioned approaches with complete and efficient usage of the available computational power. This paper focuses on aeroelasticity analyses currently performed at the Leonardo Labs facilities, exploiting the recently installed davinci-1 supercomputer [14]. Open-source CFD and structural dynamics software applications are coupled using preCICE to conduct fully threedimensional FSI analyses of aeroelastic test cases of industrial interest. The activities are part of a broader Digital Innovation industrial strategy centred on Digital Twins combining high-fidelity, highly scalable numerical simulations with data-driven AI models.
Abstract
The aerodynamic performance of industrial aircraft is strongly coupled with the structural deformation under aerodynamic load. Consequently, multi-physics simulations represent [...]
- 0
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Hemodynamic evaluation of aortic aneurysms using FSI simulations
B. Chitneedi, C. Karliampas

coupled2023.

Abstract
The work focuses on understanding aortic blood flow dynamics and emphasize the importance of considering the flexible aortic wall model in assessing cardiovascular health and identifying potential risk factors for aneurysm and related conditions. In this paper, a fluidstructure interaction (FSI) study of vascular blood flow based on the partitioned approach using open-source software tools, OpenFOAM for Computational Fluid Dynamics (CFD) and CalculiX for Computational Structural Mechanics (CSM), coupled through the preCICE tool is presented. The FSI simulations were performed on raw and simplified (based on area of interest) patient-specific models of aneurysmatic blood vessels, considering Newtonian fluid and laminar flow assumptions. The arterial wall was modeled using the CalculiX’s isotropic linear elastic model and the communication of data is handled by preCICE. The biomedical metrics such as the Time-Averaged Wall Shear Stress (TAWSS) and the Oscillatory Shear Index (OSI) in correlation with cardiac cycles were quantified to predict rupture prone regions.
Abstract
The work focuses on understanding aortic blood flow dynamics and emphasize the importance of considering the flexible aortic wall model in assessing cardiovascular health [...]
- 0
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Data-Parallel Radial-Basis Function Interpolation in preCICE
D. Schneider, T. Schrader, B. Uekermann

coupled2023.

Abstract
We present data-parallel approaches to solve radial-basis function interpolation problems in the context of partitioned multi-physics simulations, where interpolation methods are required to transfer coupling data between non-matching vertex clouds. Data-parallel approaches are a key component for the efficient use of accelerator cards and thus for performance portability on modern compute platforms. The presented approach is integrated into the open-source coupling library preCICE. After discussing different implementation strategies, we introduce a solution based on thelinear algebra library Ginkgo, which provides a common abstraction layer for cross-platform performance with focus on solving sparse linear systems. The new implementation exploits accelerator cards for both, matrix assembly as well as solving the resulting linear system. The capability of the presented approach is compared to already existing implementations in preCICE using a turbine blade geometry
Abstract
We present data-parallel approaches to solve radial-basis function interpolation problems in the context of partitioned multi-physics simulations, where interpolation methods [...]
- 0
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Implementation and Formulation of a Multi-Region, Electromagnetic Solver for Discontinuous Media
A. Bogaers, W. Roos, Q. Reynolds, J. Zietsman

coupled2023.

Abstract
The formulation and implementation of a finite-volume, multi-region, electromagnetic solver into OpenFOAM, and coupled using preCICE is presented, to enable the solution of electromagnetic problems with large material discontinuities.
Abstract
The formulation and implementation of a finite-volume, multi-region, electromagnetic solver into OpenFOAM, and coupled using preCICE is presented, to enable the solution [...]
- 0
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Partitioned Flow Simulations with preCICE and OpenFOAM
M. Mühlhäußer, G. Chourdakis, B. Uekermann

coupled2023.

Abstract
Large and heterogeneous flow simulations could benefit from partitioning, where each subdomain is solved by an individual, dedicated code. In this paper, we investigate and validate the fluid-fluid module of the preCICE-OpenFOAM adapter by coupling two incompressible OpenFOAM fluid solvers via a surface Dirichlet-Neumann coupling approach. The results of various simple test cases are compared to monolithic OpenFOAM simulations. By utilizing a special pressure boundary condition, the coupled results show only a small error around the coupling interface. The magnitude of this error depends on the velocity gradient, the mesh width, as well as the cell orthogonality. Looking into the OpenFOAM source code reveals that higher accuracy is only possible by manipulating the solvers themselves and thereby violating the black-box approach of preCICE. The fluid-fluid module is extended to couple temperature with sufficient accuracy for one validation case. Furthermore, support for multiphase flow solvers is added to the adapter. Lastly, custom inlet-outlet boundary conditions are implemented for pressure and velocity, which switch their behavior dynamically, depending on the flow direction. The results shown in this presentation provide a basis for future fluid-fluid coupling applications with preCICE.
Abstract
Large and heterogeneous flow simulations could benefit from partitioning, where each subdomain is solved by an individual, dedicated code. In this paper, we investigate and [...]
- 0
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Towards Computational Efficient Fully Coupled Aeroelastic Simulations of Turbomachinery Blades with TRACE and CalculiX
M. Freimuth, C. Berthold, F. Herbst

coupled2023.

Abstract
In the industrial design of turbomachinery blades their aeroelastic behaviour is most commonly investigated by methods, that use linearization or rely on unidirectional coupling. To circumvent the limitations of those methods a new fully coupled simulation in the time domain with the structural solver CalculiX and the turbomachinery CFD solver TRACE is currently developed and presented in this paper. The coupling library preCICE is chosen to couple the mentioned elaborated single physics solvers due to its focus on high performance computing applications. Within this work the preCICE adapter for CalculiX has recently been enabled to work with a special CalculiX method, that allows to investigate dedicated eigenforms of the blades or other structural objects. It is furthermore shown that the use of this CalculiX method can lead to a massive speedup for use cases, where the structural dynamics response can be well described by a piece-wise linear approximation within each increment. On the other hand a completely new preCICE adapter for TRACE has been developed and is introduced here. The preCICE-coupled system of CalculiX and TRACE is successfully validated against a TRACE-internal coupling approach by investigating a simple testcase with a NACA profile blade that shows good agreement.
Abstract
In the industrial design of turbomachinery blades their aeroelastic behaviour is most commonly investigated by methods, that use linearization or rely on unidirectional coupling. [...]
- 99
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Implementing a Comprehensive Hydromechanical Model for Sedimentary Basins by Coupling a 3D Mechanical Code to a Classic Basin Fluid Flow Code with the PreCICE Library
J. Gratien, D. Colombo, S. Chaisemartin, A. Pasteau, B. Vialey

coupled2023.

Abstract
In this paper, we present a coupling strategy for the implementation of a comprehensive hydromechanical model for sedimentary basins [1]. The preCICE framework [2] has been used to efficiently implement an iterative coupling scheme between ArcTem, a sedimentary basin fluid flow code, and Code Aster [20], a finite element general purpose mechanical code. We discuss several issues related to different domain partitions used by the parallel codes, to the time evolutivity of the 3D meshes and to the different time stepping used by each code. We have used the preCICE framework communication system to efficiently exchange data between the codes and to interpolate fields between usually non-matching meshes. The iterative coupling scheme is managed by means of the functionalities provided by preCICE. We validate our coupled code on a real sedimentary basin study [19]. We evaluate the flexibility of the preCICE framework to efficiently implement advanced iterative coupling algorithms. We compare the performance of our solution to a standard approach based on a centralized supervisor controlling the coupling flow and using files to exchange data between the codes.
Abstract
In this paper, we present a coupling strategy for the implementation of a comprehensive hydromechanical model for sedimentary basins [1]. The preCICE framework [2] has been [...]
- 0
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Ensemble Kalman Inversion for reduced Multi-scale Model via Deep-learning
H. Bansal, Y. Hong, K. Veroy

coupled2023.

Abstract
In the context of nonlinear multi-scale problems, the inverse estimation of macroscopic distribution of some microscopic parameters based on macroscopic measurements poses significant challenges. These challenges arise from (1) the high computational cost to solve the complex forward problem, and (2) the need for derivatives of the complex multi-scale forward model, which combines macro-scale and micro-scale simulations, both of which are typically nonlinear. To address these challenges, we propose a novel approach that combines ensemble Kalman inversion for derivative-free inverse estimation and a physics-informed deep learningbased model order reduction (DL-MOR) to accelerate the micro-scale simulation. We evaluate the performance of our method using a non-linear hyper-elastic model. The results demonstrate the effectiveness of DL-MOR in significantly speeding up the micro-scale simulation and enabling relatively accurate estimation of the microscopic parameter using only macro-scale boundary measurements.
Abstract
In the context of nonlinear multi-scale problems, the inverse estimation of macroscopic distribution of some microscopic parameters based on macroscopic measurements poses [...]
- 0
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Non-Intrusive Model Order Reduction for Sintering Applications
R. Dhopeshawar, H. Bansal, K. Veroy, H. Shi, D. Giuntini

coupled2023.

Abstract
We are interested in thermo-mechanical problems arising in the context of a practically relevant manufacturing process called sintering. These models can be defined using a non-linear material model, namely the Skorohod-Olevsky Viscous Sintering (SOVS) constitutive model. This SOVS model is used to predict macroscopic sintering behavior, such as shrinkage and density evolution. Also, it relies on material properties such as temperature-dependent viscosity and surface tension. However, high-fidelity simulations of coupled, macroscopic, thermo-mechanical models are computationally intensive. Furthermore, developing reducedorder models addressing the non-linearities is challenging due to the history dependence and presence of internal variables. Performing parametric studies, optimization, real-time control, or parameter estimation for such problems, thus, becomes infeasible. In order to accelerate sintering simulations for such multi-query scenarios, a surrogate model is vital. Here, we present a non-intrusive reduced-order modelling framework based on proper orthogonal decomposition and Gaussian process regression. Furthermore, we discuss the performance of such a surrogate model using different metrics for the two-parameter Arrhenius-type viscosity function
Abstract
We are interested in thermo-mechanical problems arising in the context of a practically relevant manufacturing process called sintering. These models can be defined using [...]
- 0
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Component-based model order reduction procedure for large scales Thermo-Hydro-Mechanical systems
A. Iollo, G. Sambataro, T. Taddei

coupled2023.

Abstract
In this work we develop a component-based model order reduction (CB-pMOR) procedure for a class of problems in nonlinear mechanics with internal variables. The work is motivated by applications to thermo-hydro-mechanical (THM) systems for radioactive waste disposal. The THM system is coupled, time-dependent, and highly nonlinear; furthermore, the solution to the problem depends on several parameters, which might be related to the geometric configuration (e.g. the number of repositories, their distance or their size) or the material properties of the medium. We investigate the effectiveness of the proposed method in terms of accuracy and computational costs for a two-dimensional THM system in the case of overlapping partitions
Abstract
In this work we develop a component-based model order reduction (CB-pMOR) procedure for a class of problems in nonlinear mechanics with internal variables. The work is motivated [...]
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A Comparison Of Direct Solvers In FROSch Applied To Chemo-Mechanics
A. Heinlein, B. Keifer, S. Prüger, O. Rheinbach, F. Röver

coupled2023.

Abstract
Sparse direct linear solvers are at the computational core of domain decomposition preconditioners and therefore have a strong impact on their performance. In this paper, we consider the Fast and Robust Overlapping Schwarz (FROSch) solver framework of the Trilinos software library, which contains a parallel implementations of the GDSW domain decomposition preconditioner. We compare three different sparse direct solvers used to solve the subdomain problems in FROSch. The preconditioner is applied to different model problems; linear elasticity and more complex fully-coupled deformation diffusion-boundary value problems from chemomechanics. We employ FROSch in fully algebraic mode, and therefore, we do not expect numerical scalability. Strong scalability is studied from 64 to 4 096 cores, where good scaling results are obtained up to 1 728 cores. The increasing size of the coarse problem increases the solution time for all sparse direct solvers.
Abstract
Sparse direct linear solvers are at the computational core of domain decomposition preconditioners and therefore have a strong impact on their performance. In this paper, [...]
- 0
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Coupled Spatio-Temporal Dynamics and Nonlocality in Advanced Mathematical Models for the Analysis of Complex Neurodegenerative Disease Pathologies
S. Pal, R. Melik

coupled2023.

Abstract
One in six of the world’s population has to deal with neurodegenerative disorders, and while medical devices exist to detect, prevent, and treat such disorders, some fundamentals of the progression of associated diseases remain ambiguous. In this contribution, we focus on Alzheimer’s disease (AD), where amyloid-beta (Aβ) and tau proteins are among the main contributors to the development or propagation of AD. The Aβ proteins clump together to form plaques and disrupt cell functions. Moreover, the abnormal chemical change in the brain helps to build sticky tau tangles that block the neuron’s transport system. Astrocytes generally maintain a healthy balance in the brain by clearing the Aβ toxic plaques. Even so, over-activated astrocytes release chemokines and cytokines and also react to pro-inflammatory cytokines, further increasing the production of Aβ. We have provided details of a novel coupled mathematical model that can capture astrocytes’ dual behaviour, emphasizing the importance of spatio-temporal coupling and nonlocality. We have demonstrated that the disease propagation depends on memory effects, that is the disease’s earlier status, which involves non-Markovian processes. We have explained how to integrate brain connectome data in the network model and to study this effect, as well as the dual role of astrocytes as a coupled phenomenon. Depending on toxic loads in the brain, we have also discussed details of the analysis of the neuronal damage in the brain. We have explained how the memory effect can slow down the propagation of toxic proteins in the brain, decreasing the rate of neuronal damage. Representative numerical examples have been given, and special attention has been paid to nonequilibrium considerations and stochastic modelling frameworks in the study of neurodegenerative diseases.
Abstract
One in six of the world’s population has to deal with neurodegenerative disorders, and while medical devices exist to detect, prevent, and treat such disorders, some [...]
- 0
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Development of an FSI Environment for the Aerodynamic Performance Assessment of Flapping Wings
R. Poletti, M. Barucca, L. Koloszar, M. Mendez, J. Degroote

coupled2023.

Abstract
Insects and birds take advantage of their flexible wings to modulate the aerodynamic forces and increase their flight efficiency. A deep understanding of the aeroelastic benefits could be valuable to design Flapping Wing Micro Air Vehicles (FWMAVs) that exploit nature’s full potential. This work presents an open-source, high-fidelity, Fluid-Structure Interaction solver (FSI) to simulate flapping and deforming wings. The proposed approach uses the code CoCoNuT to couple the Computational Structural Mechanics (CSM) software Kratos Multiphysics with the Computational Fluid Dynamics (CFD) software OpenFOAM. The coupling code relies on the Interface Quasi-Newton with Inverse Jacobian method (IQNI). The CSM evaluates the wing deformation using a classic Finite Element Method with shell elements, while the CFD solver uses the deformable overset method. In the CFD solver, the deformation of the wing is interpolated onto the grid’s boundaries to accurately simulate wings with large motion and deformation. The FSI solver is tested in the case of an airfoil in heave motion and validated with experimental data. The results demonstrate the strong influence of wing deformation on its aerodynamic performance
Abstract
Insects and birds take advantage of their flexible wings to modulate the aerodynamic forces and increase their flight efficiency. A deep understanding of the aeroelastic benefits [...]
- 0
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A numerical approach for the characterization of the free-fall dynamics of thin disks
A. Lolli, G. Corsi

coupled2023.

Abstract
This study focuses on investigating numerically the dynamics of thin disks freely falling inside viscous and incompressible fluids. We solve the model by using the finite element method and the main falling modes are identified using the Reynolds number and dimensionless inertia moment. The results are mapped in a phase diagram for comparison with existing literature and validation of the simulations. The effect of introducing a hole in the disk geometry is investigated, analyzing variations in trajectories and Strouhal numbers. Furthermore, falling styles are quantified by examining the fluctuations of the orientation of the axis of the disks over time. Additionally, a quantitative analysis of the solid body velocities for the fluttering and tumbling modes highlights the significant differences between them. The study successfully characterizes the main falling modes through qualitative and quantitative analyses.
Abstract
This study focuses on investigating numerically the dynamics of thin disks freely falling inside viscous and incompressible fluids. We solve the model by using the finite [...]
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Efficient numerical methods for simulating cardiac electrophysiology with cellular resolution
F. Chegini, A. Foehly, N. Huynh, L. Pavarino, M. Potse, S. Scacchi, M. Weiser

coupled2023.

Abstract
The cardiac extracellular-membrane-intracellular (EMI) model enables the precise geometrical representation and resolution of aggregates of individual myocytes. As a result, it not only yields more accurate simulations of cardiac excitation compared to homogenized models but also presents the challenge of solving much larger problems. In this paper, we introduce recent advancements in three key areas: (i) the creation of artificial, yet realistic grids, (ii) efficient higher-order time stepping achieved by combining low-overhead spatial adaptivity on the algebraic level with progressive spectral deferred correction methods, and (iii) substructuring domain decomposition preconditioners tailored to address the complexities of heterogeneous problem structures. The efficiency gains of these proposed methods are demonstrated through numerical results on cardiac meshes of different sizes.
Abstract
The cardiac extracellular-membrane-intracellular (EMI) model enables the precise geometrical representation and resolution of aggregates of individual myocytes. As a result, [...]
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Multiphysics Numerical Investigations of Hot Components in a sCO2 Power Plant Turbine
G. Generini, I. Rafanellí, A. Andreini, M. Dozzini, A. Milani, M. Bigi

coupled2023.

Abstract
To achieve a higher energy conversion efficiency, the use of supercritical CO2 (sCO2) in closed-loop Brayton and Rankine cycles has become relevant in the last decades due to an increased interest in its properties. sCO2 allows a more efficient heat transfer, chemical stability, non-flammability, and greater system efficiency. The necessity of a sealing system, which creates a barrier between the high-pressure fluid in the turbine and compressor and low-pressure regions, became essential for high-efficiency preservation and plant emissions reduction. In this regard, Dry Gas Seals (DGS) become one of the substantial components for sCO2 turbomachinery design due to lower leakage and higher efficiency than a traditional labyrinth radial seal. The high fluid pressure and density, connected to a small size sealing clearance and a high rotational speed, results in a significant friction heat, which characterizes the domain temperature distribution. The necessity for a thermal analysis of the domain becomes compelling to respect the maximum temperatures allowed in the turbomachine. When drawing up a thermal analysis, the high computational costs of a 3D simulation of the fluid domain (CFD) could be unfavourable due to the different orders of magnitude of secondary flows cavity sizes and DGS seals gaps, and the necessity to run a high number of simulations to define a geometrical sensitivity and optimization of crucial zones. A segregated conjugate heat transfer (CHT) iterative procedure has been implemented, relating a commercial 1D fluid modeller (Altair Flow Simulator) and a commercial finite element solver (Ansys Mechanical). To assess the procedure developed, 3D CFD simulations and CHT analysis of specific critical areas of the domain have been carried out. The segregated approach, implemented within the European project CO2OLHEAT, showed results in line with 3D CFD and CHT analysis, reducing computational time and cost.
Abstract
To achieve a higher energy conversion efficiency, the use of supercritical CO2 (sCO2) in closed-loop Brayton and Rankine cycles has become relevant in the last decades due [...]
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The effect of inherent nonlinearities in coupled piezo-magneto-electric vibration energy harvester
R. Ardito, M. Rosso

coupled2023.
- 0
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Accelerating the FlowSimulator: Improvements in FSI Simulations for the HPC Exploitation at Industrial Level
M. Cristofaro, J. Fenske, I. Huismann, A. Rempke, L. Reimer

coupled2023.
- 0
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Influencia de los factores socioeconómicos en la mortalidad por COVID-19 en México
V. Soulé, C. Hernández-Vela

SMCCA (2023). 6

Abstract
La pandemia por el virus SARS-CoV-2 mostró la necesidad de realizar estudios multidisciplinarios que ayudaran a entender el riesgo de mortalidad por COVID-19. En este trabajo se buscó determinar la influencia de los factores socioeconómicos que existían dentro de la población mexicana mediante la aplicación del modelo de regresión lineal múltiple, para esto el análisis se hizo a nivel municipal en las 3 primeras olas de la pandemia, definiendo grupos poblacionales homogéneos para identificar cuáles son los factores socioeconómicos que tienen mayor influencia y nos ayudan a describir el riesgo de fallecer por COVID-19 en México.
Abstract
La pandemia por el virus SARS-CoV-2 mostró la necesidad de realizar estudios multidisciplinarios que ayudaran a entender el riesgo de mortalidad por COVID-19. [...]
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Tendencias actuales en los recursos humanos
P. Barrera

Colección Generación 2023 UTEQ (2023). 3

Abstract
New trends in human resource management include human talent management, focus on job performance, recruitment of qualified candidates,andemployeeperformance evaluation. Today, there is a growing adoption of cutting-edge technologies in the field of humancapitalmanagement.These technologies include artificial intelligence, data analytics, process automation and cloud platforms. One of the most prominent trends is the use of artificial intelligence and machine learning to improve efficiency and decision making in humancapitalmanagement.These technologies make it possible to analyze large amounts of data to identify patterns and trends, which helps HR professionals make more informed and strategic decisions. Anotherimportanttrendisprocess automation. More and more organizations are adopting systems and tools that automate repetitive and administrative tasks, such as payrollmanagement,recruitingand performance tracking. This frees up time for HR professionals to focus on more strategic activities, such as talent development and succession planning.
Abstract
New trends in human resource management include human talent management, focus on job performance, recruitment of qualified candidates,andemployeeperformance evaluation. Today, [...]
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- 5/5
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¿La obesidad tiene consecuencias en el desarrollo físico a causa del sedentarismo?
C. García, F. Ramos

Colección Generación 2023 UTEQ (2023). 2

Abstract
La obesidad es una enfermedad crónica compleja con múltiples factores causales, incluyendo genéticos, sociales y de estilo de vida. Se caracteriza por aumento en los depósitos de grasa debido a un desequilibrio entre la ingesta de energía y el gasto energético, resultando un aumento de peso. Este desequilibrio es la causa de la obesidad. La obesidad tiene consecuencias para la salud, incluyendo un mayor riesgo de desarrollar diabetes tipo 2, hipertensión arterial, enfermedades cardiovasculares y varios tipos de cáncer. Además, la obesidad conlleva estigmatización social y, en algunas sociedades, se asocia con menores ingresos laborales, especialmente en mujeres. Los costos directos e indirectos de la obesidad ejercen una presión significativa sobre los sistemas de atención médica y requieren una acción urgente basada en la evidencia científica para la prevención y control. Desde una perspectiva económica, se estima que la obesidad tiene un alto costo. En 2008, se calculó que el costo anual en atención médica directa para el sistema de salud público, derivado de complicaciones asociadas con la obesidad, ascendía a 42,000 millones de pesos. Además, se estimó un costo indirecto por pérdida de productividad de 25,000 millones de pesos en el mismo año. En total, los costos directos e indirectos de la obesidad en 2008 se situaron en 67,000 millones de pesos. Para 2017, se proyecta que los costos directos oscilen entre 78,000 y 101,000 millones de pesos, y los costos indirectos entre 73,000 y 101,000 millones de pesos, si las medidas gubernamentales actuales no generan un impacto significativo. Dentro del resumen se pueden apreciar palabras calves que serán útiles para la investigación, las cuales son: genéticos, obesidad, energía, sociedad y finalmente cardiovascular.
Abstract
La obesidad es una enfermedad crónica compleja con múltiples factores causales, incluyendo genéticos, sociales y de estilo de vida. Se caracteriza por [...]
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Algoritmo no supervisado para la segmentación de imágenes digitales de micrografías de nanopartíclas de plata (Ag).
A. Rivas, J. Fraga Almanza, C. García, A. Estrada, E. Villanueva

SMCCA (2023). 2

Abstract
La segmentación de imágenes es un tipo específico de agrupamiento de datos. El agrupamiento en este contexto es conocer grupos de píxeles en las imágenes para obtener información relevante que por lo general se encuentra implícita en ellas. La Microscopía Electrónica de Transmisión (MET o TEM, por Transmission Electron Microscopy) es un una técnica experimental y de alto costo monetario, en la que un haz de electrones suficientemente acelerado colisiona con una muestra (nanopartículas de plata (Ag) en este caso) delgada convenientemente preparada. En la muestra los electrones colisionan con respecto a algunas propiedades específicas (grosor y tipo de átomos), todo este proceso forma una imagen digital con distintas intensidades de gris que corresponde al grado de dispersión de los electrones incidentes. Propiedades como la cantidad y el diámetro de nanopartículas existentes en este tipo de imágenes es relevante conocer de forma automatizada, ya que por lo general conocer este tipo de propiedades se hace mediante procedimientos laboriosos. Sin embargo, analizar este tipo de imágenes utilizando algoritmos no supervisados simplifica este tipo de trabajo, pero implica enfrentarse al problema de alta densidad de pixeles existentes en ellas. El algoritmo KMeans es del tipo no supervisado y utilizado para hacer segmentación de píxeles en imágenes de micrografías como lo indican algunos autores y que en este trabajo en etapa inicial es utilizado para contabilizar y obtener el diámetro de nanopartículas de plata (Ag) que son las imágenes con las que se cuenta hasta el momento y son el resultado del grupo de trabajo experimental de la División de Ciencias e Ingeniería de la Universidad de Guanajuato Campus León. Para llevar a cabo todo el procesamiento computacional se utilizará una computadora de nueva generación llamada Parallella que es un proyecto de bajo costo monetario, poco consumo energético y diseñado para el alto desempeño de cálculo numérico, siendo estas características una opción que beneficiará a este proyecto por no contar con infraestructura computacional adecuada.
Abstract
La segmentación de imágenes es un tipo específico de agrupamiento de datos. El agrupamiento en este contexto es conocer grupos de píxeles en las [...]
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El algoritmo KMeans y el problema de los centroides iniciales
G. Torres Aguirre, A. Rivas, J. Fraga Almanza, J. Zul, J. Valdez

SMCCA (2023). 3

Abstract
El gran volumen de datos en el que se vive en la actualidad, hace evidente la necesidad de clasificar los datos para obtener relaciones, asociaciones y correlaciones de ellos. Para llevar a cabo esta clasificación es necesario emplear algoritmos de agrupamiento del tipo no supervisado y particionales. Un candidato de este tipo es el algoritmo KMeans, ampliamente utilizado para resolver el problema de agrupamiento. Sin embargo, este algoritmo necesita de argumentos iniciales como lo son el número de grupos y un conjunto de datos llamados centroides que son los representantes de cada uno de ellos. Esto puede ser una fortaleza pero a la vez puede representar limitaciones del algoritmo. Es por ello que en este trabajo se inicia con la caracterización general del algoritmo KMeans en base a la selección de los centroides iniciales para después estudiar la técnica de análisis de componentes principales y con esta proporcionar centroides iniciales óptimos, pero esa etapa aún está en desarrollo y por tanto solo se presenta la idea inicial. La herramienta computacional es clave para el trabajo con alta densidad de datos es por eso que en este trabajo también se tiene como objetivo implantar un marco de trabajo llamado Apache Spark.
Abstract
El gran volumen de datos en el que se vive en la actualidad, hace evidente la necesidad de clasificar los datos para obtener relaciones, asociaciones y correlaciones de ellos. [...]
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Simulación numérica sobre el efecto del plasmón localizado de nanopartículas de plata (Ag), bajo el marco de la teoría de Mie
J. Fraga Almanza, C. García, E. Mendoza, A. Rivas, G. Torres Aguirre

SMCCA (2023). 4

Abstract
Las nanopartículas (Nps) de metales nobles como plata (Ag) y oro (Au) en las últimas décadas son objeto de extensa investigación en el contexto de las nanociencias y la nanotecnología, principalmente esto se debe a sus propiedades ópticas únicas. En las Nps, el gas de electrones libres en ellas presenta propiedades de oscilación resonante, fenómeno conocido como el plasmón superficial localizado (PSL). Al irradiarse las Nps en el ultravioleta y visible del espectro, la absorción óptica, depende fundamentalmente del material constitutivo, la geometría de la Nps y su entorno. La dispersión de la radiación electromagnética de una esfera, es definida por la Teoría de Mie. Los cálculos al usar esta teoría pueden llegar a ser largos e incluso imposibles para aquellos con recursos hardware limitados. Por lo tanto en esta investigación que actualmente, se encuentra en desarrolló, se diseño e implanto una simulación numérica escrita en Python 3 para la obtención de los coeficientes de Mie en nanopartículas de plata (Ag) y contar con una herramienta computacional que generé escenarios permitiendo el estudio y obtención de los coeficientes de extinción de NPs de Ag, siendo esta metodología fácilmente adaptable para otros metales donde se pueden calcular y/o simular una variedad de propiedades ópticas.
Abstract
Las nanopartículas (Nps) de metales nobles como plata (Ag) y oro (Au) en las últimas décadas son objeto de extensa investigación en el contexto [...]
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Construction of a global vector autoregression with trade and financial relationships between countries and forecasting of Russian macroeconomic indicators
A. Zubarev, M. Kirillova

RUSSIAN PRESIDENTIAL ACADEMY OF NATIONAL ECONOMY AND PUBLIC ADMINISTRATION (2023). 219

Abstract
The purpose of this research is to analyze the impact of external shocks on the Russian economy and build forecasts for the dynamic of Russian macroeconomic variables within the framework of a global vector autoregression model. In this study, special attention is focused on including channels for transmitting not only real but also financial shocks into the model by using different weights for aggregating variables. Also, the model for the Russian economy has been expanded by including not only variables of the real sector, but also indicators of the inflation rate and interest rate. The results provide impulse response functions for Russian indicators in response to a US interest rate shock.
Abstract
The purpose of this research is to analyze the impact of external shocks on the Russian economy and build forecasts for the dynamic of Russian macroeconomic variables within [...]
- 3
- 3/5
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La Reinserción Social en el Estado de Querétaro
O. Ledezma

Colección Generación 2023 UTEQ (2023). 1

Abstract
Esta investigación se enfoca en la reinserción social de individuos privados de libertad en México, destacando su relevancia en el sistema penitenciario y la sociedad en general. Se definen conceptos clave, como la reinserción social, la diferencia entre cárcel y presidio, y la delincuencia. Los programas de reinserción se presentan como elementos cruciales para prevenir la reincidencia delictiva y promover la rehabilitación de aquellos que han transgredido la ley. Se adopta la Teoría de la Prevención como marco conceptual, que enfatiza la importancia de prevenir la reincidencia a través de la educación y la promoción de valores positivos. Además, se emplea el método de la Teoría Fundamentada, que se basa en la construcción de teorías a partir de datos recopilados de manera sistemática. Se describen las técnicas de descripción, ordenamiento conceptual y teorización como herramientas esenciales en la investigación. En resumen, esta investigación resalta la necesidad de una cultura de prevención en los programas de reinserción social en México para mejorar su efectividad y reducir los costos del sistema penitenciario. La reinserción exitosa no solo beneficia a los individuos que han cometido delitos, sino que también contribuye a la seguridad y el bienestar de la sociedad en general al reducir la delincuencia y fomentar la reintegración de ex delincuentes como miembros productivos de la comunidad.
Abstract
Esta investigación se enfoca en la reinserción social de individuos privados de libertad en México, destacando su relevancia en el sistema penitenciario y la sociedad en [...]
- 351
- 4.7/5
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ESTIMATES OF DISTORTIONS OF THE ECONOMIES OF THE EAEU COUNTRIES FROM EXISTING NON-TARIFF BARRIERS» (first stage)
V. Eremin, V. Sedalishchev

RUSSIAN PRESIDENTIAL ACADEMY OF NATIONAL ECONOMY AND PUBLIC ADMINISTRATION (2023). 217

Abstract
Inevitably, non-tariff barriers (NTBs) that exist in trade between countries generate rents associated with them, which can either be distributed in some ratio between trading partners or dissipate, thereby leading to a loss of resources. The valuation of these rents and their distribution is not an easy task, because the effect of NTBs in their entirety is usually difficult to quantify due to the different nature of the trade restrictions that make up NTBs. Nevertheless, in the light of the global trend towards tariff liberalization that has been going on for more than a hundred years, this task sometimes becomes more important in the study of trade than classical studies of the impact of import and/or export tariffs, since NTB rents can multiply tariff revenue. One of the possible tools for modeling the impact of NTBs on the economies of various countries (and in particular on the domestic prices of goods), taking into account the existing trade relations between states, are static CGE trading models (from the English Computable General Equilibrium models computable general equilibrium models). One of the objectives of this study is to prepare our own database based on the most recent available statistical data, similar in structure to the GTAP 10 database, but with a smaller number of regions and supplemented with information about the ad valorem equivalents of the goods we are interested in in the context of trading partners. As the results in this study, the following aspects of the work carried out can be distinguished, such as a review of the literature on existing approaches to assessing the imbalances of economies generated by NTM, as well as an analysis of trade in goods and services between the EAEU countries and their main partners, which is necessary for interpreting the results of the numerical modeling stage, a scheme for preparing input data for calibration of the used CGE models.
Abstract
Inevitably, non-tariff barriers (NTBs) that exist in trade between countries generate rents associated with them, which can either be distributed in some ratio between trading [...]
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Russia-CIS co-operation development in the context of world economic structural transformation. (Part I)
A. Knobel, K. Bagdasaryan, Y. Zaytsev, V. Sedalishchev, A. Firanchuk, M. Baeva, M. Kazaryan, D. Kuznetsov

RUSSIAN PRESIDENTIAL ACADEMY OF NATIONAL ECONOMY AND PUBLIC ADMINISTRATION (2023). 218

Abstract
The first part of the research studies theoretical approaches, models and factors in determining the structural transformation of the world economy and presents some empirical assessments. The object of this study is trade and economic cooperation of the CIS countries in the context of structural transformation of the world economy and new trade and political restrictions introduced against Russia and Belarus, which have a significant impact on the entire system of foreign economic relations. The aim of the study is to assess the changes in the level of integration in different spheres of Russia, the EU, China with the CIS countries and CIS countries among themselves and the impact of sanctions against Russia and Belarus on the CIS countries. The relevance of the work is justified by the transformation of economic ties of the CIS countries, the forced need for Russia to search for new international transport and logistics routes and financial schemes and the processes of transformation of the system of international economic relations, which together form a new economic reality for the CIS. The paper uses an empirical method of quantitative data research, econometric method of calculating various indicators and indices, as well as systemic analysis. The main results of the study consist in analyzing changes in the conditions of trade and economic cooperation of post-Soviet countries and integration in different spheres in 2022, including interrupted projects, including those with third countries.
Abstract
The first part of the research studies theoretical approaches, models and factors in determining the structural transformation of the world economy and presents some empirical [...]
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PROSPECTS FOR THE DEVELOPMENT OF THE LONGEVITY ECONOMY IN THE REGIONS OF RUSSIA
. I.Grishina, A. Polynev, A. Filatov

RUSSIAN PRESIDENTIAL ACADEMY OF NATIONAL ECONOMY AND PUBLIC ADMINISTRATION (2023). 216

Abstract
The relevance of the work is justified by the fact that it is devoted to the rapidly developing sector of the economy associated with the needs of the older generation. The growth of this sector is associated with the global trend of population aging. The subject of the study is the comparative level of the quality of life of senior citizens and the potential for the development of the longevity economy in the regions of Russia. Purpose of work: a comprehensive study of the factors and evaluation of the prospects for the development of the longevity economy in the regions of Russia and development of priority areas of regional policy. To achieve the goal, the following tasks were undertaken: analysis of scientific approaches to the study of the factors of formation and assessment of the prospects of the «longevity economy at the national and regional levels in the framework of foreign and domestic experience; development of an approach to a comprehensive assessment of factors and prospects for the development of the longevity economy in the regions of the Russia, taking into account the specifics of national and regional statistics; analysis of demographic, social and economic factors in the formation of the longevity economy and assessment of the prospects for its development in the regions of the Russia; a typology of the regions of the Russia in accordance with the assessment of the prospects for the development of the longevity economy; development of proposals on the priorities of regional policy, taking into account the course on import substitution in the conditions of sanctions pressure and the obtained estimates of the prospects for the development of the longevity economy in the regions of Russia. The scientific novelty of the work is determined by the justification of the typology of Russian regions on the basis of the developed integral quality of the older generation life index and the prospects for the development of the longevity economy. Research methods applied: system, factor and statistical analysis of sectoral development, index method, etc. Based on the application of the author's approach, several Russian regions that need additional federal support to improve the older generation life quality and to develop a longevity economy were identified. Priority measures of regional policy have been developed for such regions. The application of the authors’ approach is recommended for information and methodological support of the state regional policy of Russia and increasing of its effectiveness.
Abstract
The relevance of the work is justified by the fact that it is devoted to the rapidly developing sector of the economy associated with the needs of the older generation. The [...]
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Evaluation of Brain Signal Amplifier Circuit Performance by Polymer Biosensor in Portable Neurological Patient Monitoring System
S. Pirayeshfar;, M. Asadollahi;, R. Rahimi;

Current Neuropharmacology (2023). Pirayeshfar.S., Asadollahi.M., Rahimic. R. 2022, Evaluation of Brain Signal Amplifier Circuit Performance by Polymer Biosensor in Portable Neurological Patient Monitoring System. Current Neuropharmacology., 23(2). 201. 10.2174/1570159X20666220927093818

Abstract
Increasing the flexibility of electrodes by using flexible biocompatible biopolymer substrates as well as using conductive polymers with suitable electrical conductivity such as (PEDOT: PSS) instead of metallic base materials in the electrode channels has greatly contributed to this goal. But the next step is to increase the amplitude of the touched signal by the electrode in an amplifier circuit by suitable gain factor. Therefore, in the present study an electrical biosensor consisting of a 64-channel microelectrode with intra-structural amplification capability, external circuit precision for amplification of sensible brain signals on scale has been studied. Thereafter, the polymer biosensor to be integrated into a dry and portable monitoring system for monitoring neurologic disorders and identification of focal seizures symptoms e.g. in aura state for epilepsy. This has allowed by achieving a precise signal on scale even with a dry multichannel electrode, without no electrolyte gel between the surface of the electrode and the skin. Although, localization of the electrode is restricted, due to the importance of touching the prone signals in the frontal and partial lobes, it has been attempted to place the electrode on the frontal area to increase both signal sensibility and processing. Moreover, the error of muscle movements in frontal lobe is reduced by locating electrode in frontal-partial (FP) position to achieve a signal that overlapping both lobes to predicting seizure symptoms more accurately. This set-up has been successfully tested on patients, and along with the designed interface circuit, using an open-source oscillography application, signal touching has also been accomplished by an Android-based mobile phone.
Abstract
Increasing the flexibility of electrodes by using flexible biocompatible biopolymer substrates as well as using conductive polymers with suitable electrical conductivity such [...]
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Research on seismic performance of corrugated web rigid structures
C. huimin

cao huimin's personal collection (2023). 1

Abstract
Corrugated steel refers to steel that is wavy along the length direction and is widely used in beams, columns, walls, and other parts of building structures. It plays a connecting and supporting role. The wavy or folded shape of the web plate to some extent improves the shear instability ability and out-of-plane stiffness of the web plate. Industrial factories often use corrugated web H-shaped steel components. However, although corrugated web H-shaped steel components have the advantages of high strength, high stiffness, lightweight, and convenient construction, relevant regulations indicate that these components can only be used for lower intensities or higher intensities when certain conditions are met, One important condition is that the ratio of the design value of axial force including seismic action to the product of the cross-sectional area of the component flange and the design value of steel tensile strength should not exceed 0.4. In this regard, this article will further explore the seismic characteristics and applicable intensity of H-shaped steel structures with corrugated web plates under earthquake action through large-scale finite element ABAQUS simulation. The dynamic characteristics and failure situation of corrugated rigid frame structures will be observed through the elastic-plastic time history analysis method, and the plastic deformation characteristics of steel beam members will be observed by applying low-cycle repeated loads through the hysteresis analysis method. The research shows that under reasonable design conditions, Corrugated web H-shaped steel structural components can be appropriately increased in axial compression ratio for use in high-intensity areas.
Abstract
Corrugated steel refers to steel that is wavy along the length direction and is widely used in beams, columns, walls, and other parts of building structures. It plays a connecting [...]
- 0
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Failure of ETFE Film Membrane
D. Karádi, D. Hegyi

membranes2023.
- 2
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Plektotonik - Structural textile membrane from fast growing and formable trees (SRC)
N. Miodragovic, D. Suarez, K. Wolff, T. Kendir, N. Singer

membranes2023.
- 127
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