An overview of sheet metal forming simulations with enhanced assumed strain elements

Abstract

Sheet metal forming operations are characterized by extreme shape changes in initially flat or pre-formed blanks, thus needing complex and robust simulation tools for their correct virtual analysis. Among numerical approaches, finite element procedures are one of the most common techniques in modelling and simulation of such manufacturing applications. However, reliable simulations of complex parts’ sheet forming must be able to correctly reproduce the deformation patterns involved but also accurately predict the appearance of defects after or during forming stages. Among the most common defects in the forming of metallic parts, spring-back and wrinkling are of crucial importance in manufacturing viewpoint. Spring-back appearance can be traced to the onset of traction instabilities when the tools depart the blank due to a rearrangement of stress fields after forming (or forming stages) and so, the unloaded blank reaches a new equilibrium. On the other side, wrinkling defects can be seen as compressive dominated defects and, in this sense, be dealt with as buckling-type structural instabilities. In this work, a class of solid-shell finite elements [1,2,3,4], based on distinct features but relying on the enhanced assumed strain approach, are tested in the simulation of sheet metal forming operation in metallic components. Results obtained from these elements, specially designed to treat transverse shear and volumetric locking effects, are then compared with well-established references in the literature, including experimental and numerical studies, where, for the latter case, shell finite elements are dominantly used (as can be seen, for instance, in reference [5]).