Sliding contact fracture on glass and silicon

Abstract

Surface crack geometry produced during sliding contact on amorphous glass specimens and silicon single-crystal specimens was investigted. The experiments were performed by sliding a spherical indentor on a surface with increasing normal load in ambient air and oil environments. The results show that the cracks formed on the contact surface due to sliding motion are governed by the stress field generated. Cracks tend to follow the maximum principal tensile stress trajectories in amorphous glass specimens, but the cracks generated on silicon were strongly influenced by the planes of easy cleavage on the contact surface. The normal load P, friction coefficient of contact and crystallographic cleavage plane directions were found to have a large influence on the surface crack patterns. A general relation, W ∝ P^1/3, was obtained for the measurement of crack widths W in all testing conditions. Crack-morphologies were related to material removal. Studies showed that the latter is often due to chip formation which occurs between very closely spaced cracks.