ИСТИНА

In upset forging of solid cylinders, disks and strips with high friction, material that is originally on the free surface folds over to come into contact with the die. The attempts to incorporate foldover into theoretical analysis have been reported in several publications. In particular, the upper bound theorem has been utilized in some of them. However, the upper bound theorem in plasticity is formulated for a given configuration and results in an approximate velocity field whereas the analysis of foldover requires a displacement field. A sequential upper bound method is in general applicable for predicting of foldover. However, this method is usually used in conjunction with a finite element procedure, which makes the overall approach time consuming. On the other hand, it is known that faster methods of analysis are needed for some applications. Such a method is developed in the present paper for upset forging of solid cylinders. The final solution is verified by experiment.