Wear of Fluorapatite Single Crystals : IV. Influence of Sliding Direction on Frictional Behavior and Surface Failure

Abstract

Frictional anisotropy of the basal plane of natural fluorapatite single crystals was observed ; the coefficient of friction (β) in the [ 2110] direction (β = 0.217) was approximately 12% higher than that in the [ 0110] direction (β = 0.193). The load at which the ductile-to-brittle transition occurred (Ω) was significantly higher in the [ 2110] direction (Ω = 77 gm) than in the [ 0110] direction (Ω = 15 gm). A mechanism is proposed involving the maximum normal stress and probable cleavage planes.