The UBST approach to the stress analysis of plane-strain upsetting with a newly constructed model of the slip-line field

This research presents a new model for constructing a slip-line field by combining the concepts of stream-lines. For the purpose of finding the strain-rate field of plane-strain upsetting, the upper-bound stream function elemental technique (UBST) method is used to find the optimal flow patterns with the technique of constraint. From the calculated strain-rate field and the above-mentioned model, the slip lines are drawn, along which slip lines the stress field can be found easily from Hencky's equations. The results indicate that the slip-line field constructed by this method shows a good agreement with the shear boundary conditions, and that the trend of the normal pressure along the friction boundary is reasonable.