Effects of X-Ray Irradiation on the Self-Friction of Potassium Chloride

Abstract

The forces of static and sliding friction between mechanically polished x-ray irradiated KCl were found to satisfy the equations: F (static)=AN12+BNand F (sliding)=B′N+D′N32,where F is the force of friction, N is the normal force, and A, B, B′, and D′ are numerical coefficients. Various models of friction were examined, and it was shown that both the functional relationships between friction and the normal force and between the changes in the numerical coefficients and the F-center concentration are consistent with a modification of the theories of Bowden and Tabor and of Rabinowicz. In this modification, the coefficients are given by A/B=MW/p12B=B′=s/pD′=M′p−12,where s is the shear strength of the junctions of the contacting asperities, p is the flow pressure of the asperities, W is the work of adhesion per unit area, and M and M′ are numerical constants. The changes of the frictional coefficients A/B, B, B′, and D′ were proportional to the square root of the F-center concentration induced by the x-ray irradiation and were consistent with the theory of defect hardening proposed by Fleischer and the flow stress experiments of Nadeau and of Sibley and Sonder.