Friction and Surface Morphological Studies in Plastic Deformation under Boundary Lubrication Condition

Abstract

A new testing technique has been developed to represent a surface plastic deformation process under high sliding speed and load and under boundary lubrication conditions. The technique involves oblique plastic impact with a steel ball, in which a boundary lubricant film on a steel surface is subjected to the simultaneous action of high load and sliding speed. The purpose of this is to explore the behavior of boundary lubricants under solid surface plastic deformation conditions. By varying the angle of impact and height, large variations in sliding speed and load can be achieved. The lubricant is applied with a nominal thickness of 1.0 μm reducing the possibility of hydrodynamic effects. Detailed examination of impact craters by microscopy distinguished the different lubricants effectively. A distinction could be made between oleic acid, stearic acid, palm oil and base oil. Some commercial oils were also studied and their differences could be distinguished. Friction during contact was also studied by noting the distance travelled to a second impact and modeling the ball motion through simple kinematics. This approach leads to approximate evaluation of friction coefficient, which is also taken into account in analyzing the lubricant behavior. A portion of this work was presented in the International Conference on Industrial Tribology (1).

KEY WORDS:

• Boundary Lubrication
• Plastic Deformation