Research on the relation between bulging and friction in cylinder upsetting

model based on the rigid-plastic finite element method for cylinder upsetting is built, by which the upsetting processes are simulated for the ratio of height to diameter 1.5 and 1.0 respectively when the friction factors vary from 0.1 to 1.0. The relation between bulging and friction factor in cylinder upsetting is quantificationally described. The relation can be used to eliminate the friction and to estimate the friction factor in cylinder upsetting.