1991 Volume 40 Issue 448 Pages 58-64
The thermal load due to the frictional heat in a material during the two-dimensional sliding contact between a hard indenter and a brittle material is theoretically shown to relax the tensile stress induced by the mechanical load in the surface layer of the material behind the indenter. This implies that the plastic deformation which generally occurs only by a sharp indenter appears even by a much blunter indenter without any elastic cracking. In this paper, the indenter's transition radius was defined as the critical radius which distinguishes the occurence of the first plastic deformation from the elastic cracking as the first damaging event. In the analysis, both the fracture criterion and the yield criterion were employed. It was shown that the transition radius Rc increased steeply and then slowly with an increase in sliding speed V. The both speeds which give Rc to increase steeply and slowly varied depending on thermal diffusivity κ and thermal constant M=α·E/{2·(1-ν)·ρ·C} (where, α: coefficient of expansion, E: Young's modulus, ν: Poison's ratio, ρ: density, C: specific heat) as well as their relative values. The above speeds were almost the same for Si3N4, Al2O3, and glass, but they were much higher for SiC.
