Consideration of frictional boundary modelling in metal forming

Scope and method of study. A General methodology for finite-element modelling of friction in non-symmetric geometries has been developed. The approach provides for the inclusion of a sticking-critical shear model for large scale deformation found in metal forming. This method does not require the use of GAP elements at the die-metal interface.; An elastic-plastic finite element computer program was developed for plane strain deformation which provided the capability of evaluating various frictional boundary condition models. The effect of rigid body rotation was considered in this development. The stability of the program was examined by obtaining the solution of upsetting of a rectangular block.; A review of the methods of incorporating friction as a boundary condition in large scale plastic deformation was conducted and the methods classified into three categories. The basic friction models were tested using the finite element code. The results of the simulations using these different methods of modelling friction were compared with experimental deformation data obtained from the deformation of wedge-shaped specimens under plane strain conditions. The recently proposed friction model by Bay (2), when incorporated into the FEM code, provided the best correlation with the experimental results. The Bay model of sticking/friction at the die-workpiece boundary is an attempt to more accurately model the tribological/metallurgical events taking place in deformation.; Findings and conclusions. The capability of the FEM elastic-plastic code, incorporating the friction model proposed by Bay, to predict the location of the neutral point in complex shapes was established by compression of a wedge-shaped specimen. It is no longer necessary to use other methods, such as the slab method, to predetermine the position of neutral points and the direction of flow at the boundary.