Steel sheet surface topography and its influence on friction in a bending under tension friction test

In order to investigate the frictional response of different surface topographies for steel sheet materials, a Bending-Under-Tension friction test was used. The test included six different surface topographies, of which two were shotblasted (SB), three were electron beam-textured (EBT), and one had electro-chromium deposition (ECD). The testing was performed in mixed lubrication under equal conditions for all materials used. For measurement of the sheet surface-topography. a 3D stylus instrument was used and the ball-filtering technique was applied. The surface topography was measured in the contact zone on the test samples. The ECD material showed the lowest friction coefficient, and an SB material the highest. In order to describe the frictional behaviour caused by the two main lubrication mechanisms. MPHDL and MPHSL, a so-called Wihlborg-Crafoord index (WC index) was determined. The WC index is the number of isolated oil pockets (NIOPt) multiplied by the border length of the lubricant area at the area fraction of contact (BLalfa) divided by the area fraction of contact (a). This WC index describes how effective the supply of lubrication is at the contact zones and correlates well with the friction coefficient. (C) 2001 Elsevier Science Ltd. All rights reserved.