Fracture wear of grinding wheels

Abstract

Evidence is presented which supports the argument that the fracture type of wear process is the most important with regard to the loss of abrasive material from a wheel during a grinding operation and that fracture occurs as a consequence of the high stresses induced in the grains by the grinding forces to which they are subjected. Abrasive materials exhibit much higher strength properties when loaded in compression than when loaded in tension and therefore grain fracture will be readily caused by induced tensile stresses of relatively low magnitudes. Experimental data, namely grinding force components and wheel wear rates, are extracted from published works and the forces are applied to a model grain thought to be representative of an average real grain in a grinding situation. Stresses within the model grain are evaluated using a finite element method, particular attention being paid to the maximum value of tensile stress and the relative values of tensile and compressive stresses. Indications are that it is the tensile stresses which are the more likely to initiate fracture and good correlation is found between the maximum value of tensile stress induced in the model grain and the appropriate wheel wear rate (grinding ratio) obtained from published data. It is concluded that the general level of tensile stresses induced in abrasive grains is the best indicator to wheel wear rates during a grinding operation.