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Research


 
  Photo Elisabeth Massoni

Director of the CEMEF                


Center for Material Forming
CEMEF - MINES ParisTech
06904 Sophia-Antipolis -  France
tel.  +33 (0)4 93 67 89 01
fax. +33 (0)4 92 38 97 52
office: Bat C. R021d
email: elisabeth.massoni@mines-paristech.fr

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Research Interests
Keywords:
  • Thermo-mechanical coupling and metallurgy
  • Solid state phase change materials 
  • Localization phenomena & striction criteria during forming processes
  • Deep-drawing
  • Hydroforming of sheets and tubes
  • Finite Element methods for simulating different material forming processes: deep-drawing, welding, stir welding, heat treatments, stamping, hydroforming, steel melting and casting, flow forming, heating and quenching of ingots and parts



1- Modelling of thin sheet metal forming processes

 

We are interested in the prediction of elastic springback and residual stresses, two topics that are badly treated in most commercial "explicit" software. Better results can be obtained using the implicit approach of FORGE software, together with constitutive equations including non-linear kinematic hardening, which are identified by flexion tests. A second objective is formability analysis. Different criteria for localized necking are studied and developed, by comparison with experimental forming limit curves.

Pic Stamping

 

2- Simulation of titanium alloys behaviour for cold forming processes of metal sheets

 

Simulation of titanium alloys behaviour for cold forming processes of metal sheets. We are interested in the mechanical behaviour of a titanium alloys. It is modeled for the cold forming processes. The elasto-plastic constitutive law is decomposed in an anisotropic plastic criterion, an isotropic hardening and a kinematic hardening. Non quadratic criteria have been developed by Cazacu et al. to model the plasticity of hexagonal closed packed materials. The implementation of this model in a finite element software switches between two bases, the equilibrium is calculated in a reference basis and the anisotropy axes define a local basis, updated by the deformation gradient. An identification procedure, based on tensile tests, allows to define all the parameters needed to model the elasto-plastic behaviour. Simulation of cold forming processes (bulging and deep drawing) have been done to validate this model. Numerical results are compared with experimental data, obtained from speckles analysis.

 

 

 

Pic titanium


3- Formability study of magnesium alloy AZ31B


We are interested in the formability of the AZ31B magnesium alloy at various temperature and strain rates. The tensile tests are performed to describe the rheological behavior of material, and the constitutive law is identified with Voce law  which contains a softening item. The law is proved effectiveness by fitting the equation with the experimental data. Nakazima experiments with hemispherical punch have been performed at CEMEF on a hydraulic testing machine. Six strain paths are selected by performing various sample geometries. The Aramis Optical strain measurement system has been used to obtain principle forming limit strain. The Forming Limit Diagram (FLD) is obtained by the critical point on the specimen surface at various temperatures. It is shown that the forming limit curve is higher at high temperature. Based on the Voce law model, finite element simulations of deep drawing test have been done with the commercial finite element code FORGE® in order to investigate the feasibility of hot stamping process for AZ31. In the simulation, the punch load and the thickness distributions have been studied. Meanwhile, the cross-shaped cup deep drawing simulations have been conducted with the data provided in the conference Website. The similar conclusion are obtained that the formability of AZ31 improve at high temperature and the simulation is effective in hot stamping processing. The study results are helpful for the application of the stamping technology for the magnesium alloy sheet.


 
B.P. 207 - 06904 Sophia Antipolis Cedex
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