Properties of metal sheets with 3-D designed surface microgeometry prepared by special rolls

Abstract

Aluminium sheets are processed to have circular surface microcavities of 100 μm in diameter and 10 to 20 μm deep by a combined process of ion-beam etching, rotary coining of rolls and passive rolling. The deformation and lubrication behaviour of the sheets in sheet metal forming are simulated by a strip draw test using round dies. The slid surfaces ofthe sheets are analyzed by a Scanning Laser Microscope (SLM) and Atomic Force Microscope (AFM) to obtain quantitative evaluation of the change in surface microgeometry. It is found that the surface microcavities show lowered friction even in low viscosity oil lubrication. The deformation of the microcavities and, hence, lubrication process is decomposed to the following stages: (a) preliminary flattening, (b) lateral shrinkage, (c) establishing mechanical seal under compression and sliding, and (d) unloading. A quantitative change in microcavity capacity suggests a major effect of squeezing the before establishing mechanical seal.