Effect of variational friction and elastic deformation of die on oscillating cold forging for spline shaft

Oscillating cold forging (OCF) is an extrusion method with pulse ram motion. Compared with conventional cold forging (CCF), the OCF can greatly reduce the forming force, which can be contributed to the factors including friction, elastic deformation of die and the metal flow according to the simulations and experiments. To investigate the differences between the OCF and CCF, forming experiment, hardness test and micro observation were performed. In consideration of the different friction condition and variational velocity, a friction modal considering sliding and velocity was used in simulation. The force-stroke curve got from the horizontal oscillating extrusion machine shows that OCF can reduce the load about 25% than CCF and that oscillating frequency affects the friction as well as the forming force. Moreover, the results of experiment and simulation indicate the surface quality of OCF is better than CCF because lower friction leads to less metal pileup.