Experimental study on the single grit interaction behaviour and brittle–ductile transition of grinding with a diamond micro-grinding tool

This study presents new information on single grit interaction behaviour and its brittle–ductile transition in micro-grinding single crystal silicon using a single grit diamond tool. A model to describe the energy interaction between the cutting behaviour of a single grit and the workpiece in micro-grinding is established based on the single grit geometry model, which was indicated in Fig. 1a, the critical condition of the volume of material removed and the conservation of energy. The tip angle of the single-point diamond tool has been considered. To reveal the material removal mechanism of micro-grinding, a series of scratching experiments, which conducted with a low cutting speed (0.036 to 0.6 m/s), have been performed in this study. The fractures of the micro-grooves machined using single-point diamond tools have been examined by a microscope and a surface profilometer, thus revealing different processing modes (brittle and ductile). The variation curves of the fracture length c have been presented on the condition of different tool tip angles θ (60° and 120°). It is found that the fracture size of grooves machined by a grit with a blunt angle is comparatively larger than that of a grit with a sharp angle for the same scratching parameters. The scratching speed v and penetration depth p 0 have a direct effect on the fracture length c , which increases obviously with the rising of v and p 0 . The critical condition has been investigated based on the experimental results; the blunt grit (with a larger tip angle: θ = 120°) and the sharp grit (with a smaller tip angle: θ = 60°) have different brittle–ductile transitions and different critical cutting depths, which are 334 nm ( θ = 60°) and 607 nm ( θ = 120°), respectively. The effects of the scratching speed v are investigated. The brittle–ductile transitions of the different scratching speeds have been compared. The relationship between the fracture length c and the volume of material removed in unit time V has been discussed; V is an important measuring constant for the fracture formation and critical ductile cutting condition. This study reveals the mechanism of the single grit interaction in micro-grinding with an ultra-small grinding tool and provides theoretical and experimental validation for ductile micro-grinding of single crystal silicon.