A basic study of the influence of surface topography on mechanisms of liquid lubrication in metal forming

摘要

Applying a transparent tool technique the tool/workpiece interface in plane strip drawing of aluminium is studied. The strips are provided with macroscopic lubricant pockets, and the compression and eventual escape of trapped lubricant by themechanisms Micro Plasto HydroDynamic Lubrication (MPHDL) and Micro Plasto Hydrostatic Lubrication (MPHSL) is observed and quantified experimentally with respect to the lubricant pocket parameters, shape, volume, and angle to the edge. The two mechanismshave proved to depend very differently upon these parameters. The level at which the hydrostatic pressure is stabilized is shown to be independent of the volume of a pocket and the MPHDL mechanism is therefore solely dependent on the angle to the edge,which is shown both experimentally and theoretically by a fluid mechanic analysis. For the MPHSL mechanism a dependency of the volume is observed.