Presenting a new method for evaluating friction effects at extrusion die entrance based on combination of the open die backward extrusion and ring compression tests

In this article, a new combined approach including, the ring compression test and open die backward extrusion (ODBE) test, is presented to assess the friction coefficient in the extrusion process. It is assumed that the frictional behavior at the free surface of the die and the extrusion cavity is different. Firstly, the friction coefficient at the contact interface between the free surface of the die and the workpiece is obtained using the ring compression test. Then, to obtain the friction calibration curves at the contact interface between the workpiece and the extrusion channel, the finite element simulations of the ODBE test are performed for different friction coefficients in this area, and the friction coefficient is obtained comparing the experimental results and calibration curves. The comparison of the friction coefficients obtained from the three tests shows that the friction coefficient in the extrusion cavity is higher than that of the free surface.