Abstract
The texture of die surface plays an important role in the tribology of metal forming processes. The surface texture is defined by surface roughness and its orientation, which is influenced by the manufacturing processes. In this research, the effects of various die machining operations on the frictional condition in the forming process of CK45 steel are investigated by means of ring compression test. The dies are fabricated through six machining operations, including horizontal and vertical milling, electrical discharge machining, grinding, polishing and turning. Moreover, the ring specimens are compressed by parallel die plates. Effects of different parameters such as machining method, lubrication condition and deformation percentage on the friction coefficient are investigated with the help of design of experiments and analyzing the results. Finite element simulation is also used to obtain the calibration curves in the ring compression test. The obtained results reveal the significant effect of die machining process on friction coefficient. In addition, the maximum and the minimum friction coefficient values are associated with the electric discharge machining and grinding with polishing, respectively. Furthermore, it is found that despite the approximately same values of mean roughness value (Ra) in vertical milling, electrical discharge machining and turning, different frictional coefficients are obtained due to the dissimilar mean roughness depth (Rz), surface hardness and surface texture of the inserts