Experimental characterization and comparison of planar and corrugated aluminum sheets

To evaluate the effect of the corrugation [1] on the mechanical behavior of aluminum plates, a corrugated sheet on aluminum alloy Al1050 is characterized under tensile mechanical tests at room temperature. To characterize anisotropic behavior of the material, tensile experiments are carried out in three different tensile directions i.e. 0, 45 and 90° with respect to the rolling direction. All experiments are performed until final failure using both planar and corrugated sheets for comparison issues. Concerning the experimental supplies, a tensile testing machine is used which can handle forces until 5 kN and can perform monotonic tensile as well as cyclic displacement and force controlled tests. The tensile machine is connected with a digital image correlation background. The measurement apparatus is equipped with two cameras for the detection of displacement fringes. The equipment is able to detect transversal and longitudinal displacements and calculate strain values at also virtual rectangular gauges or along straight lines. The responses of both planar and corrugated plates are compared in the macroscopic level within the force-displacement curves, damage localization zones and macroscopic crack propagation paths. The experimental data for Al1050 is quite interesting because it will be used for the material parameters identification of anisotropic elasto-plastic models combined with mixed hardening and isotropic damage [2]. The implemented models are validated later by comparisons between finite element simulations of Marciniack tests in the FE code Abaqus® and complementary experimental data

Numerical simulation based on FEM/MLS coupling for solid mechanics

This paper presents the development of Meshless Methods based on the weighted least squares approximation (MLS) [1,3,14] to solve 2D mechanical problems. A particular construction support of weight functions involved in the construction of the MLS shape functions is elaborated. We propose a numerical simulation based on the coupling between the FEM and the MLS method. A Huerta et al. formulation is used to build the MLS shape function in the transition area FEM/MLS

Thermodynamics and Multi-physical Model for Application to the Effect of Severe Environment on Metallic Alloys

In this paper, we have formulated a fully coupled thermo-elasto-visco-plastic-damage theory, which includes both kinematic and isotropic hardening, and takes also into account the diffusion of several species in metals. This theory is based on the thermodynamics of irreversible processes under small strain hypothesis. Each specie is supposed to diffuse in both lattice and trapping sites. In order to take correctly into account of different coupling effects, the diffusion fluxes vectors depend not only on the gradient of chemical potential, but also on the gradient of temperature (thermodiffusion) and on the gradient of pressure (barodiffusion). The heat flux also depends not only on the gradient of temperature, but also on the chemical potential gradient of each specie, according to the thermodynamics of irreversible processes. This model is implemented into Abaqus/Standard using the Uel user subroutine. An application is made for the diffusion of hydrogen in TA6V after welding

An elasto-plastic self-consistent model for damaged polycrystalline materials: Theoretical formulation and numerical implementation

Elasto-plastic multiscale approaches are known to be suitable to model the mechanical behavior of metallic materials during forming processes. These approaches are classically adopted to explicitly link relevant microstructural effects to the macroscopic behavior. This paper presents a finite strain elastoplastic self-consistent model for damaged polycrystalline aggregates and its implementation into ABAQUS/Standard finite element (FE) code. Material degradation is modeled by the introduction of a scalar damage variable at each crystallographic slip system for each individual grain. The single crystal plastic flow is described by both the classical and a regularized version of the Schmid criterion. To integrate the single crystal constitutive equations, two new numerical algorithms are developed (one for each plastic flow rule). Then, the proposed single crystal modeling is embedded into the self-consistent scheme to predict the mechanical behavior of elasto-plastic polycrystalline aggregates in the finite strain range. This strategy is implemented into ABAQUS/Standard FE code through a user-defined material (UMAT) subroutine. Special attention is paid to the satisfaction of the incremental objectivity and the efficiency of the convergence of the global resolution scheme, related to the computation of the consistent tangent modulus. The capability of the new constitutive modeling to capture the interaction between the damage evolution and the microstructural properties is highlighted through several simulations at both single crystal and polycrystalline scales. It appears from the numerical tests that the use of the classical Schmid criterion leads to a poor numerical convergence of the self-consistent scheme (due to the abrupt changes in the activity of the slip systems), which sometimes causes the computations to be prematurely stopped. By contrast, the use of the regularized version of the Schmid law allows a better convergence of the self-consistent approach, but induces an important increase in the computation time devoted to the integration of the single crystal constitutive equations (because of the high value of the power-law exponent used to regularize the Schmid yield function). To avoid these difficulties, a numerical strategy is built to combine the benefits of the two approaches: the classical Schmid criterion is used to integrate the single crystal constitutive equations, while its regularized version is used to compute the microscopic tangent modulus required for solving the self-consistent equations. The robustness and the accuracy of this novel numerical strategy are particularly analyzed through several numerical simulations (prediction of the mechanical behavior of polycrystalline aggregates and simulation of a circular cup-drawing forming process)

Pseudo inverse approach for cold forging processes and its comparison with adaptive incremental approach

La simulation numérique des procédés de mise en forme fortement non-linéaire nécessite souvent des méthodes numériques performantes. Les couts de calcul qui sont souvent important rende difficile l'utilisation d'un outil de simulation numérique dans une boucle d'optimisation. Nous proposons dans ce papier de simuler un procédé 2D axisymétrique de forgeage d'une roue en utilisant une approche pseudo-inverse et une approche MEF adaptive incrémentale. Ces deux approches seront ensuite comparées en termes de temps de calcul et prédictibilité sur la forme des bruts de forge

A hybrid Meshless-FEM field transfer technique minimizing numerical diffusion and preserving extreme values: Application to ductile crack simulation

International audienc

Numerical simulation based on FEM/MLS coupling for solid mechanics

This paper presents the development of Meshless Methods based on the weighted least squares approximation (MLS) [1,3,14] to solve 2D mechanical problems. A particular construction support of weight functions involved in the construction of the MLS shape functions is elaborated. We propose a numerical simulation based on the coupling between the FEM and the MLS method. A Huerta et al. formulation is used to build the MLS shape function in the transition area FEM/MLS

An advanced elastoplastic framework accounting for induced plastic anisotropy fully coupled with ductile damage

We present in this investigation an advanced phenomenological approach combining the computational efficiency of classical phenomenological plasticity models and the accuracy and high resolution of multiscale crystal plasticity schemes. Within this advanced approach, a new phenomenological constitutive framework has been developed and implemented into ABAQUS/Standard finite element (FE) code. Compared to classical approaches, this framework allows accounting for initial and induced plastic anisotropy, isotropic nonlinear hardening and the full coupling with isotropic ductile damage. Material parameters corresponding to this phenomenological constitutive framework are identified based on multiscale polycrystalline simulations, where the self-consistent scheme is used to ensure the transition between the single crystal and polycrystal scales. The single crystal mechanical behavior is assumed to be elastoplastic (rate-independent), and microscopic material degradation is well-considered by introducing a scalar damage variable at each crystallographic slip system for each individual grain. The evolution of polycrystalline yield surfaces, induced by the evolution of crystallographic texture, is accurately reproduced by the new constitutive modeling, where the anisotropy parameters are assumed to evolve during plastic deformation. Their evolution laws are identified based on multiscale simulations. The different identification procedures are presented and extensively discussed. The robustness and reliability of this advanced model are analyzed through some relevant numerical predictions obtained by applying a combined tensile/shear test.French program Plan d'Investissement d'Avenir (PIA) Agence Nationale de la Recherche (ANR