The process design of trimless bolt heading is studied in connection with reduction of number of processes. The process is designed as three stages of forming operations with no trimming instead of conventional four-stage forming operations.
Two typical stages, i.e., bulge upsetting and filling stages are analyzed using an upper-bound method. For the bulge upsetting stage, a general bulge upsetting is studied permitting different frictional conditions at the upper and lower flat surfaces of an axisymmetric specimen. In the filling stages, a method of analysis is proposed in obtaining the load to form a bolt head.
Experiments are carried out according to the proposed process design of trimless bolt heading. Analytic predictions are in good agreement with the experimental observation. The advantages of this new design method are discussed.
