A Seizure Initiation Mechanism in Cold Metalworking Processes : Effect of Tool Surface Roughness on the Critical Oil Film Thickness

Abstract

An extrusion-type friction test and a forced sliding test have been carried out to examine the critical conditions for seizure initiation in different tool surface roughnesses using a commercially pure aluminium as a word-metal. The thinner the applied lubricant oil film thickness, the earlier the seizure occurred in every tool surface roughness. However, the critical punch stroke for seizure initiation decreased significantly with the increase of the tool surface roughness. The oil film thickness trapped in the tool-work interface was measured experimentally and estimated theoretically. As a result, it has been clarified that the critical oil film thickness for seizure initiation increases with the increase of the tool surface roughness.