Influence of Lubricant Pocket Geometry upon Lubrication Mechanisms on Tool-Workpiece Interfaces in Metal Forming

Micro lubricant pockets located on the surface of plastically deforming workpieces are recognized to improve the performance of fluid lubrication in a metal forming processes. This work investigates the joint influence of pocket geometry and process working conditions on micro lubrication mechanisms, during upsetting and strip drawing, by means of a rigid viscoplastic finite element formulation.

Special emphasis is placed on the effect of pocket geometry on the build up of hydrostatic pressure, which is responsible for the onset of micro lubrication mechanisms. A good agreement is found between the numerically predicted and the experimentally measured distributions of hydrostatic stress.