SIMULATION OF ASPERITY PLOWING IN AN ATOMIC-FORCE MICROSCOPE PART-I -EXPERIMENTAL AND THEORETICAL METHODS

The plowing of a soft workpiece by a hard tool asperity is recognized as a fundamental tribological problem and key contributor to friction and wear in bulk metal forming processes such as rolling and extrusion . However, experiments on an asperity scale have been difficult to per form to date since measurements of plow track geometry, the forces req uired to create the plow track, and the plowing speed must be made ove r a very small length scale. It is therefore the purpose of this paper to describe a new experimental method that simulates single asperity plowing of a soft workpiece material in an atomic force microscope. Us ing a sharp diamond indentor as a tool asperity, plow tracks were form ed in 99.99% pure aluminum which was chosen to demonstrate that the me thod gave repeatable results over a range of forces and speeds. A math ematical model of plowing was modified to take the plow track geometry , the measured normal and plowing forces, and the plowing speed as inp ut variables and provide a measure of the friction factor (and hence s hear stress) along the indentor-workpiece interface, as well as the wo rkpiece flow strength. The companion paper presents the results of asp erity plowing experiments (based upon the methods presented in the pre sent article) on specific aluminum alloys of differing hardnesses. (C) 1998 Elsevier Science S.A.