Fazilay Abbès

Finite Element Simulation of the Strength of Corrugated Board Boxes Under Impact Dynamics

In this study, we propose a model based on the finite element method to study the behavior of corrugated cardboard boxes subjected to shocks. To reduce the preparation of the CAD model and the computational times, we have developed an elastoplastic homogenization model for the corrugated cardboard. The homogenization consists in representing a corrugated cardboard panel by a homogeneous plate. A through-thickness integration on a periodic unit cell containing a flute and two flat linerboards is proposed. Each constituent is considered as an orthotropic elastoplastic material with specific hypotheses for the corrugated medium. The model was implemented in the finite element software ABAQUS. Damage boundary curve (DBC) for corrugated cardboard boxes are defined by experimental testing and finite element simulations using the proposed model. The numerical results obtained are in good agreement with the experimental results.

2D modeling of direct laser metal deposition process using a finite particle method

Direct laser metal deposition is one of the material additive manufacturing processes used to produce complex metallic parts. A thorough understanding of the underlying physical phenomena is required to obtain a high-quality parts. In this work, a mathematical model is presented to simulate the coaxial laser direct deposition process tacking into account of mass addition, heat transfer, and fluid flow with free surface and melting. The fluid flow in the melt pool together with mass and energy balances are solved using the Computational Fluid Dynamics (CFD) software NOGRID-points, based on the meshless Finite Pointset Method (FPM). The basis of the computations is a point cloud, which represents the continuum fluid domain. Each finite point carries all fluid information (density, velocity, pressure and temperature). The dynamic shape of the molten zone is explicitly described by the point cloud. The proposed model is used to simulate a single layer cladding.Direct laser metal deposition is one of the material additive manufacturing processes used to produce complex metallic parts. A thorough understanding of the underlying physical phenomena is required to obtain a high-quality parts. In this work, a mathematical model is presented to simulate the coaxial laser direct deposition process tacking into account of mass addition, heat transfer, and fluid flow with free surface and melting. The fluid flow in the melt pool together with mass and energy balances are solved using the Computational Fluid Dynamics (CFD) software NOGRID-points, based on the meshless Finite Pointset Method (FPM). The basis of the computations is a point cloud, which represents the continuum fluid domain. Each finite point carries all fluid information (density, velocity, pressure and temperature). The dynamic shape of the molten zone is explicitly described by the point cloud. The proposed model is used to simulate a single layer cladding.

A coupled thermo-mechanical pseudo inverse approach for preform design in forging

Hot forging is a process used to form difficult to form materials as well as to achieve complex geometries. This is possible due to the reduction of yield stress at high temperatures and a subsequent increase in formability. Numerical methods have been used to predict the material yield and the stress/strain states of the final product. Pseudo Inverse Approach (PIA) developed in the context of cold forming provides a quick estimate of the stress and strain fields in the final product for a given initial shape. In this paper, PIA is extended to include the thermal effects on the forging process. A Johnson-Cook thermo-viscoplastic material law is considered and a staggered scheme is employed for the coupling between the mechanical and thermal problems. The results are compared with available commercial codes to show the efficiency and the limitations of PIA.

Orientation-Dependent Response of Pure Zinc Grains Under Instrumented Indentation: Micromechanical Modeling

This chapter concerns the micromechanical behavior modeling of a pure zinc polycrystal. An inverse optimization strategy was developed to determine plastic deformation properties from instrumented indentation tests performed on individual grains of cold-rolled polycrystalline sheets. Nanoindentation tests have been performed on grains using a spherical–conical diamond indenter, providing load-penetration depth curves. The crystalline orientation of those grains has been determined using an EBSD analysis. Furthermore, a crystal plasticity model has been implemented in the finite element code Abaqus using a user material subroutine. To identify the constitutive model parameters, the inverse identification problem has been solved using the MOGA-II genetic algorithm coupled with a finite element analysis of the nanoindentation test. In a first approach, the identification procedure used the load-displacement curves issued from the indentation performed on a grain of given crystalline orientation. A good agreement is achieved between experimental and numerical results. This constitutive model has been validated by simulating the indentation response of grains of distinct crystalline orientations, involving different slip systems activity rates.

Analytical Homogenization for In-Plane Shear and Torsion of Honeycomb Sandwich Plates with Skin and Height Effects

Numerical modeling of honeycomb structures is too tedious and time consuming. The homogenization of these structures enables to obtain an equivalent homogeneous solid and its elastic stiffness thus to make very efficient simulations. In the present study, the skin effect is taken into consideration for the in-plane shear and torsion problems, in which the two skins are much more rigid than the honeycomb core. An analytic homogenization method, using trigonometric function series and based on the membrane plate theories, is proposed to study the influence of the honeycomb height on these properties, and the upper and lower bounds of the equivalent elastic stiffness of their curves are analyzed. A numerical H-model is established for the in-plane shear and torsion problems.