Microcracking Associated with the Scratching of Brittle Solids

Abstract

Observations of the microcracking about scratches in a number of brittle solids including sapphire and a variety of glasses are presented. The scratching was carried out primarily with a Vickers pyramid indenter under various loads at one scratching velocity. It is observed that the nature of the cracking is very similar to that occurring about a quasi-static pointed indenter. Directly beneath the indenter a well-defined median crack is formed, behind the indenter small partial Hertzian cracks form within the track and subsurface lateral cracking initiates from the region of the plastically deformed zone. With a Vickers pyramid the cracking phenomena may be conveniently divided into three regions with increasing load. At low loads (P 5 N) the plastically deformed track appears to shatter and the extent of lateral and median cracking is less than that occurring for the higher loads in the intermediate region.