Sébastien Thibaud

A Macro Modeling Of Phase Transition In Austenitic Stainless Steels And TRIP Steels

The paper describes a model and an inverse identification procedure for the material behaviour of new austenitic stainless steels used for car body panels, exhibiting transformation induced plasticity effects. The modelling is based on a phenomenological macroscopic approach and describes well the evolution of martensitic phase during deformation. The identification is based on a combination of experiment simulations by FEM and optimization. The resulting model and parameters are then used to illustrate in typical sheet metal forming cases the main effects associated to these new materials exhibiting martensitic transformation.

Miniaturization of the tube bulging test

The paper focuses on the miniaturization of the bulging test for material characterization of micro tubes. For the design of the experimental device, numerical simulations are conducted first. Even if no scale effect is taken into account in material modeling, numerical results give some information before designing the set‐up and performing experimental works: level of pressure inside the tube, volume of fluid necessary to create such a level of pressure and bulge height to measure. The main results are a design of the experimental device and choices for its instrumentation.

A New Modelling of Blanking for Thin Sheet in Copper Alloys with Dynamic Recrystallization

Precision blanking process is widely used by electronic and micromechanical industries to produce small and thin components in large quantities. To take account of the influence of strain rate and temperature on precision blanking of thin sheet in copper alloys, we have proposed a thermo‐elasto‐visco‐plastic modelling. In addition, dynamic recrystallization takes place in Cual copper alloy during the blanking process of thin sheet. A new modelling of dynamic recrystallization based on the thermodynamics of irreversible processes is presented. Blanking simulations of Cual copper sheet are carried out in order to analyze the softening effect induced by dynamic recrystallization.

Numerical Design Of Experiments to Analyse the Contact Conditions in Microforming

In microforming, the so‐called size effects can be observed in the material flow behaviour as well as in the frictional behaviour. In order to study the frictional behaviour a preliminary numerical characterization of the surface tribology has been carried out. A numerical design of experiments (DOE) is based on cylinder upsetting tests to define the influence of surface geometric properties on the resultant force. The simulations have been performed with the finite element software LS‐Dyna by using an axisymmetric model. The mechanical behaviour of the cylinder specimen was described by an elastic‐plastic material law, whereas the upsetting plates were assumed to be rigid. The workpiece is considered to be a copper alloy (CuZn10). The average roughness Ra and the average mean spacing Sm have been chosen to describe surface roughness properties. The tool and workpiece surfaces have been modelled using a sinusoidal profile. The five input parameters of the DOE are the amplitude and the period of the two si...

A New Modelling of Dynamic Recrystallization — Application to Blanking Process of Thin Sheet in Copper Alloy

Blanking process is widely used by electronic and micromechanical industries to produce small and thin components in large quantities. To take into consideration the influence of strain rate and temperature on precision blanking of thin sheet in copper alloy, a thermo‐elasto‐visco‐plastic modelling has been developed in [1]. Furthermore the blanking of thin sheet in Cual copper presents dynamic recrystallization. A new modelling of dynamic recrystallization based on the thermodynamics of irreversible processes is proposed. Blanking simulations of Cual copper sheet are performed to analyze the softening effect induced by dynamic recrystallization.