Finite element modelling and simulation of metal flow in bulge forming

Abstract

The research and application of finite element methods in the area of material processing has increased rapidly in recent years. Application of FEM is reported in the processing of most engineering materials including new materials like metal matrix composites. In metal forming, FEM is mostly applied to conventional forming situations like forging and upsetting, extrusion, drawing, rolling, sheet metal forming, casting and moulding and machining Most of these forming operations are also well analysed by theories of plastic deformation like limit theorems, slip-line field theory etc. In contrast, new and unconventional metal forming cases, which are often very complex, are relatively under-analysed either by the theoretical methods mentioned above or by numerical methods like finite element. This work is mainly devoted to computer simulation and study of one of the unconventional metal forming process called bulge forming. There are various type of industrial products made by bulge forming process. In some processes the main forming load is the hydrostaic pressure on the surface of the blank plate or shell. While in others, an in-plane compressive load is also applied simultaneously with the pressure load. Depending on the initial blank shape and final product shape, the simultaneous loading case becomes a complex forming situation. This project has simulated the later category of bulge forming by finite element method. Number of such cases were simulated to cover initial blank shape viz flat circular plate, flat rectangular plate and initially curved shell In the latter category axisymmetric expansion of tubes, T-branch forming from straight cylindrical tubes and forming of box-sectioned elbow from cylindrical tubes were simulated. In each case different loading and friction conditions were tried Distribution of stress and strain were studied for all the cases Companson were made between comparable forming conditions. Response of certain parameter with respect to the changes of different forming variables of the process were also studied for most of the simulated cases. In case of the bulging of flat circular plate, optimum forming condition were identified for different objective criteria Taguchi parameter design method was applied to transform the above optimum values to practicable engineering values. All the simulations were carried out using well known commercial finite element packages. Both static frontal solvers and explicit dynamic solvers were used for the simulations