ANALYSIS OF THE DISSIMILAR INTERFACE FRICTIONAL CONSTRAINTS DURING THE UPSETTING PROCESS

A thermo-elastic-plastic coupling model combined with frictional funct ions is proposed to analyse the plastic upsetting of a cylinder, accou nting for dissimilar interface frictional constraints. The pow stress of the deforming workpiece is considered as a function of strain, stra in rate and temperature, and the properties of the interface frictiona l constraints are approached through the use of two continuously varyi ng functions which are presented in terms of the amount of the workpie ce deformation . The effects of various combinations of dissimilar int erface frictional constraints at the top and bottom die surfaces on th e temperature, strain and strain rate distributions are investigated T he asymmetrical pow inducing uneven biller profiles, together with the variations in top and bottom die surface loads, are predicted. The re sults obtained are consistent with the observations of upsetting exper iments.