USI 98

Usinagem - USI 98

Title :

Ruling and indentation tests used for the investigation of the brittle/ductile transition in brittle materials

Abstract :

The ability to machine brittle materials in a controlled manner is required to significantly improve productivity and also to reduce the sub-surface damage thus eliminating the need for lapping and polishing. Much effort has been made by researchers to investigate the feasibility of turning/grinding brittle materials and to identify criteria for ductile mode machining. For brittle materials of interest, cutting depths are generally in the sub-micron range. This requirement, among with others, is well beyond the capability of conventional turning/grinding machines and the research on brittle materials is limited to polishing, indentation and scratching when super-rigid machines are not available. Indentation and ruling tests were used to investigate the effects of elasto/plastic deformation in the micrometre scale. Material properties which affect the ductile/brittle behaviour have been identified and characterised. Brittle materials have been quasi-static indented and ruled with a range of tool conditions and speeds. A ductile/brittle transition was observed when these materials were ruled. The role of material removal mechanisms such as plastic flow, cutting, delamitation and brittle fracture were observed. In this study delamitation and plastic flow were obtained more favourable with tools with large negative rake angles and cutting. Plastic flow and delamitation however can provide lower material removal rates and worse dimensional control when compared with cutting mechanisms.

Autores :

Beltrão, Paulo André de Camargo
Corbett, John

Trabalho Completo :