Effect of Friction Sliding on Filling Behavior of Workpiece Material into Micro Grooves on Surface of Forging Tool

摘要

The contact conditions between workpiece and tool surface with surface roughness (the micro grooves and asperities) were investigated. The filling state of the workpiece material into the grooves and the surface expansion of the workpiece at the micro asperities were examined for backward extrusion performed under various sliding conditions. The filling of a workpiece material into micro grooves on the surface of a forging tool with surface roughness was predominantly influenced by contact pressure. As the relative sliding velocity of the workpiece material with respect to the tools increases, the filling of the workpiece material becomes difficult, leading to a large difference in the pressure between the slopes in both sides of the asperities. The surface expansion strongly depends on the angle of asperity. The increase in the angle of asperity decreases the magnitude of surface expansion of the workpiece material. The existence of a film with a low deformation resistance (approximately 1/3 that of the base material of the workpiece) and a thickness approximately the same as surface roughness of the tool on the surface of the workpiece significantly influences the contact behavior between the workpiece and the tool.