Friction Study in Equal Channel Multi Angular Pressing: Load Curve and Ring Compression tests

Abstract

The majority of process parameters in different severe plastic deformation (SPD) methods are completely dependent on friction factor. So precise analysis of this complicated factor is always useful. Equal channel multi angular pressing (ECMAP) process, enhances the productivity of equal channel angular pressing process that is the most popular technique among SPD methods. In this article, the frictional behavior of ECMAP process was studied. Route C was selected as the multi-pass route in ECMAP process and samples were prepared from Al5754 alloy. During the process, die and strip surfaces were not in full contact with each other thus making the friction situation complicated. Thus, the values of friction coefficient were obtained by two typical methods: ring compression test and ECMAP load curve test. For the first method, to extract friction calibration curves, FE simulations were done on the compressing ring for different friction coefficients. Also, experimental works were done on prepared rings. The results of both FEM and experimental works were used to acquire the final value of friction coefficient. For the second method, ECMAP process was simulated via FEM by different friction coefficients, leading to different load stroke curves. Also, load stroke curves were achieved from experimental works, using manufactured die. Then the friction coefficient value was extracted from the comparison between the results of experiments and FEM curves. It could be concluded that in the best case scenario, the results of both methods were close to each other but in the weakest situation there was 13.6 % difference between two methods. It was inferred that, in ECMAP practical works, there were some parameters like die clearance or non-uniform lubrication surfaces that had effect on load stroke curves and, as a result on the friction coefficient estimation.