Effect of surface roughness on friction coefficients during upsetting processes for different materials

Presented study is focused on the investigation of the effect of the surface roughness on the frictional properties for different materials and conditions. Three types of steel, commercially pure aluminium and annealed CuZn40Pb2 brass were used as the test materials in the experimental part of the study. Ring compression test procedure was applied to the specimens using flat end upsetting dies. Dimensional changes of the specimens after the tests were measured in order to obtain the variations of the increments in the inner diameters versus upset ratios. Experimental results were placed into ring compression calibration curves for each of the material type and surface conditions. Roughness measurements were carried out using a digital roughness meter. Upsetting tests were carried out using a hydraulic press of 150 metric tons with 5 mm/s ram speed.