Rubbing & plowing phases in single grain grinding

The preliminary rubbing and plowing phases of material removal in the grinding process were considered in this work. Experimental, analytical, and numerical investigations into the grinding action of a single grain were used to explore the micro-mechanics of the rubbing and plowing phases. These phases are traditionally very difficult to quantify, as their scale and transient nature limit visual, direct inspection. As a consequence, a finite element (FE) model was developed and validated against experimental results for these phases and subsequently used to determine the dominant energy consuming mechanisms for each. The FE model was initially validated using indentation tests to verify the normal load generated by a grain pressed into a workpiece. Subsequently a sliding action was introduced to simulate the rubbing phase and the tangential force was verified. The onset of plowing was determined to occur at a depth 3 μm, permitting the isolation of the rubbing and plowing phases. The FE model validation was completed with the simulation of the formation of a scratch on the workpiece surface, producing one of the first models capable of simulating both phases accurately. The validated FE model was used in two case studies were the effect of grain size and depth were examined. It was found that with increasing grain size the energy consumed by friction decreases while the energy imparted to workpiece deformation increases. With increasing depth an energy peak is observed at the transition from the rubbing to plowing phases. This peak is attributed to the rapidly increasing workpiece deformation energy which begins the drop markedly with the onset of plowing.