Influence of thermoelectric coupling on pacemaker activity generated by mechano-electric feedback in a one-dimensional ring-shaped model of cardiac fiber

Peer reviewe

Particle Finite Element Method for simulations of Selective Laser Melting with vaporization

editorial reviewedThe purpose of this work is the simulation of selective laser melting processes. Such processes involve multiple physical phenomena that need to be taken into account altogether such as thermo-mechanical coupling, solid-liquid-solid phase change, surface tension and vaporization. The variety of different physical phenomena, as well as the presence of a highly deformed fluid free surface, implies multiple constraints on the required numerical procedure. Notably, the need to compute the free surface position and curvature leads to complex interface tracking algorithms in the widely-used Eulerian-based models. The Particle Finite Element Method (PFEM), a Lagrangian method with fast triangulation and boundary identification algorithms, has been chosen to overcome some of the difficulties mentioned previously. A new version of the 2D/3D PFEM code presented in (S. Février, “Development of a 3D Compressible Flow Solver for PFEM Fluid Simulations”, ULiège Master Thesis, 2020) has been developed to take into account the aforementioned physical phenomena, notably Marangoni forces and recoil pressure, and the interactions with a laser. Alongside the presentation of the mathematical formulation and the description of its numerical implementation, some simulations involving a moving laser melting a block of material are presented and discusse

Particle Finite Element Method for simulations of Selective Laser Melting with vaporization

editorial reviewedThe purpose of this work is the simulation of selective laser melting processes. Such pro- cesses involve multiple physical phenomena that need to be taken into account altogether such as thermo-mechanical coupling, solid-liquid-solid phase change, surface tension and vaporization [Cook et al., 2020]. The variety of different physical phenomena, as well as the presence of a highly deformed fluid free surface, implies multiple constraints on the required numerical procedure. Notably, the need to compute the free surface position and curvature leads to complex interface tracking algorithms in the widely-used Eulerian-based models [Chen, 2018]. The Particle Finite Element Method (PFEM), a Lagrangian method with fast triangulation and boundary identification algorithms, has been chosen to overcome some of the diffi- culties mentioned previously [Février, 2020]. A new version of the 2D/3D PFEM code presented in [Février, 2020 ; Cerquaglia 2019] has been developed to take into account the aforementioned physical phenomena, notably Marangoni forces and recoil pressure, and the interactions with a laser. Alongside the presentation of the mathematical formulation and the description of its numerical im- plementation, some simulations involving a moving laser melting a block of material are presented and discussed

On some drawbacks and possible improvements of a lagrangian finite element approach for simulating incompressible flows

In this paper a Lagrangian finite element approach for the simulation of incompressible flows is presented, based on the so-called Particle Finite Element Method (PFEM). The spatial discretization and the definition of the boundary terms are discussed in detail with a specific focus on free-surface flows. Additionally, some problems that can arise from the use of such a method are pointed out. Some numerical examples are given and discussed in the last section of the paper

Comparison of residual stresses on long rolled profiles measured by X-ray diffraction,ring core and the sectioning methods and simulated by FE method

Sheet piles are produced by hot rolling, a cooling step and, if required, by a straightening operation. Numerical simulations indicate that the stress field is almost homogeneous through the thickness, justifying the comparison of X-ray diffraction, ring core and the sectioning methods applied after the cooling step and after the straightening process. The equipment, the steps of the experimental procedures and the results are detailed, showing the limits, the specificities and the advantages of each method. Moreover, the amplitude and the distribution of the stresses along the width of the sections present good agreement with results of numerical simulations

Phase change driven adaptive mesh refinement in PFEM

peer reviewedThe particle finite element method (PFEM) is used to simulate a simple phase change problem. This is a first step towards the simulation of additive manufacturing (AM) processes at the meso-scale, where the liquid melt pool interacts with the surrounding solid material and undergoes phase change. The focus of this paper lies on strategies to deal with the release or absorption of latent heat in the PFEM, especially with regard to mesh refinement. We briefly describe how mesh refinement in PFEM works and how it can be chosen specifically to achieve convergence despite the highly non-linear latent heat term. It is found that good agreement with the literature can be achieved on a simple 1D phase change test case, while using an automatic local mesh refinement

Element activation method and non-conformal dynamic remeshing strategy to model additive manufacturing

peer reviewedModeling of Additive Manufacturing (AM) at the part scale involves non-linear thermo-mechanical simulations. Such a process also imposes a very fine discretization and requires altering the geometry of the models during the simulations to model the addition of matter, which is a computational challenge by itself. The first focus of this work is the addition of an additive manufacturing module in the fully implicit in-house Finite Element code Metafor [1] which is developed at the University of Liège. The implemented method to activate elements and to activate and deactivate boundary conditions during a simulation is adapted from the element deletion algorithm implemented in Metafor in the scope of crack propagation [2]. This algorithm is modified to allow the activation of elements based on a user-specified criterion (e.g. geometrical criterion, thermal criterion, etc.). The second objective of this work is to improve the efficiency of the AM simulations, in particular by using a dynamic remeshing strategy to reduce the computational cost of the simulations. This remeshing is done using non-conformal meshes, where hanging nodes are handled via the use of Lagrange multiplier constraints. The mesh data transfer used after remeshing is based on projection methods involving finite volumes [3]. The presented model is then compared against a 2D numerical simulation of Direct Energy Deposition of a High-Speed Steel thick deposit from the literature [4]

Addition of a finite element activation method in an existing thermomechanical finite element code to model additive manufacturing

With the rise of Additive Manufacturing (AM) technologies in the industry, it becomes more and more important to have a good understanding of such processes. However, there is still a crucial lack of fundamental knowledge regarding AM. Hence, there is a high demand for the implementation of a model to accurately simulate an AM process. The complexity of such a simulation comes from multiple sources. Firstly, from the nature of the process. Indeed, it requires geometrically non-linear thermo-mechanical simulations. Secondly, the modeling of the material law is complex. Lastly, the geometry of the process imposes a very fine discretization (layers can be as small as a few μm). This creates models that are computationally costly. Moreover, the process requires altering the geometry of the model during the simulation to model the addition of matter, which is a computational challenge by itself. This work presents the addition of additive manufacturing in the fully implicit in-house Finite Element code “Metafor”, which considers large strains and includes thermo-mechanical simulations and crack propagation simulations. The focus of the work is to add an “additive manufacturing module” to the existing thermomechanical code Metafor. The implemented method to activate elements and to activate and deactivate boundary conditions during a simulation is adapted from the element deletion algorithm implemented in Metafor in the scope of crack propagation. Indeed, in crack propagation the deactivation of an element in a simulation was already possible, i.e. an element could be deactivated based on a certain crack propagation criterion. This algorithm is modified to allow the activation of elements based on a criterion (which can, in the case of AM, be the presence or not of the element in a certain “activation volume” modeling the moving laser). After implementing other AM specificities (heat source model, annealing temperature for alloys, etc), an effective thermomechanical simulation of Additive Manufacturing is obtained. The model is then compared against the literature, including numerical and experimental results from a thermal experimental calibration and a thermo-mechanical analysis of blown powder laser solid forming of Ti-6Al-4V. Temperature, deformation and stress fields are analyzed as well as the influence of different process parameters