FINITE-ELEMENT SIMULATION OF SHEET FORMING BASED ON A PLANAR ANISOTROPIC STRAIN-RATE POTENTIAL

Many finite element (FEM) formulations have been based on stress poten tials defined in the stress field. Nevertheless, there are formulation s where potentials defined in the strain-rate field are especially con venient to implement. These include rigid-plastic formulations based o n minimum plastic work paths, which can be used for process design as well as for process analysis. Based on a strain-rate potential recentl y proposed for anisotropic materials exhibiting orthotropic symmetry, a formulation for sheet forming process analysis has been developed us ing a Cartesian coordinate system in this paper. An efficient formulat ion to account for material rotation is also included. Earing predicti ons made for a cup drawing test of a 2090-T3 aluminum-lithium alloy sh eet showed good agreement with experiments. However, some discrepancie s were observed between predicted and experimental thickness strain an d cup height directional trends. The cause of the discrepancies was di scussed using a simple analysis based on Lankford (or plastic strain r atio, r) values.