Friction and Lubrication in the Deformation Processing of Metals : 2nd Report, Surface Texture and Coefficient of Friction

Abstract

This paper is one of a series of investigations about the mechanism of friction and lubrication in metal forming processes. The friction occurring in the flange part of the cup being deep drawn is directly measured and the result is associated with the surface texture which is assessed by means of the light reflectivity method described in a previous paper. It appears that the frictional shearing stresses acting on the micro-plateau-areas of the asperities virtually in contact with the tool surface are independent of the tool pressure. Values of the frictional shearing stress per unit area of the plateau are found in accordance with the sort of lubricant, e.g., mineral, vegetable or animal oils, as well as soap suds. These stress values, to a considerable degree, seem to be associated with the coefficient of friction obtained by the four-ball-oiliness test.