Arnaud Lejeune

Influence of material and process parameters on bursting during hydroforming process

Abstract Bursting is predicted using a 3D-necking criterion based on local instability analysis. First, forming limit diagram (FLD) are built to validate the approach and the influence of material parameters is illustrated. Secondly, the criterion is implemented in a finite element code devoted to the simulation of hydroforming processes. Bursting predictions are presented and the influence of process parameters is studied.

The Diamant Approach for an Efficient Automatic Differentiation of the Asymptotic Numerical Method

Based on high-order Taylor expansions, the asymptotic numerical method (ANM) is devoted to the solution of nonlinear partial differential equation (PDE) problems arising, for instance, in mechanics. Up to now, series were mainly handwritten and hand-coded. The note discusses the automation of the specific derivative computations involved in the ANM and presents the automatic differentiation (AD) approach Diamant. As any AD tool, Diamant is generic and may be used to differentiate the code of any differentiable behaviour law. Numerical performances, measured while solving a mechanical PDE problem, prove the efficiency of the Diamant approach.

Object-oriented design to automate a high order non-linear solver based on asymptotic numerical method

The Manitoo library is devoted to the resolution of analytical non-linear problems using a high order method called asymptotic numerical method. We describe here the Object Oriented design of this library and especially the choices made to obtain a quite generic and flexible numerical solver. Through classical examples, we present a comparison with some existing tools implemented in Matlab and Fortran 77.

An optimization strategy for the determination of material and process parameters to avoid segregation defects during metal injection powder

An explicit 3D software “FEAPIM” has been developed at LMARC to perform efficiently the injection simulation to predict and simulate a segregation effect in the mixture flows during MIM, and segregation is the most defect in metal injection molding. In order to reduce it on suggest optimization strategy.A cost function is first defined to account it, and optimization strategy has been developed using the Design Of Experiments (DOE) to find the most influent parameters. Four sensitive parameters are found : Powder volume fraction, Interaction coefficient, Powder density, and Binder density. In order to decrease the computational cost associated to optimization, the response surface, using the Moving Least Square Approximation (MLSA), is used to approximate the cost function. Then a genetic algorithm is coupled with this response surface to obtain the optimal values in reasonable time. The optimization strategy proposed in this paper has been applied to the tensile test. Optimization results are compared to...

Damage in sheet metal forming: prediction of necking phenomenon

ABSTRACT Necking is a phenomenon limiting sheet metal-forming processes. The linearised perturbation technique is presented and adapted to various cases of yield criteria, damage models and 2D/3D stress states. Some aspects about calculations are given. Finally two applications of these works are shown. The first one validates the theory by establishing Forming Limit Diagrams. The second one is the implementation in a FE code and presents the necking predictions obtained on industrial cases of metal-forming.