THE UBST APPROACH TO THE STRESS-ANALYSIS OF PLANE-STRAIN UPSETTING

A new numerical approach to analyze the stress distribution in the plane-strain upsetting process is developed. In this method, the function of the upper-bound stream function elemental technique (UBST) is increased with stress integration equations. The shear stress on the friction surfaces is controlled by a constrained method and changes with the degree of deformation. The dependency of stress field, load, and geometry changes of the free boundary on the frictions conditions is estimated. Three friction conditions are used to illustrate this method. The results show that the third friction condition, which has a deformation dependency factor, provides a good agreement with the experimental data.