An experimental and 3D finite element analysis of a form rolling process

Abstract

This thesis investigates a cold forming process called Form Rolling. Form Rolling is an innovative method of producing near-net shape parts, which is being implemented in particular by fastener manufacturers. In this study, a 3D finite element analysis of a flat die Form Rolling process that formed two different depth grooves on a rolling workpiece was simulated and compared to experimental tests. The FEA package used for this study was DEFORM3D which is an implicit Lagrangian adaptive remeshing finite element code that has the ability to characterise the workpiece material stresses and deformation behaviour. The objective of this study is to attempt to explain the underlying mechanisms responsible for various defects and failures associated with Form Rolled components. In particular, the generation of lapping and twisting which are failure mechanisms influenced by material flow behaviour. The stress distributions that are generated in the workpiece during the process are also investigated to describe the conditions that led to the generation of a crack on the surface of the workpiece. The complex material behaviour of the workpiece material was successfully modelled to reveal the mechanisms by which lapping and twisting occur. It was also found that a crack on the surface of the workpiece was generated by large tensile axial stresses combining with large shear stresses, at 90 degrees to the die/workpiece interface.