Modeling of Residual Stress in Grinding of Nodular Cast Iron

In grinding operations, the high specific energy generates high temperatures in the grinding zone, and therefore causes various types of thermal damage on the workpiece surface such as burn or high tensile residual stresses. High tensile residual stresses attract significant attention because they may initiate cracks on the surface, either immediately after grinding or under in-service loading. Cracking will significantly reduce component life. Thus, avoidance of surface damage in general, and residual stresses in particular, dominates any discussion of quality/productivity trade-offs in grinding. By increasing the material removal rate (MRR) productivity is enhanced but the temperature and temperature gradient in the grinding zone are increased as is the likelihood and severity of surface damage. Currently there is no analytic or numerical tool for predicting residual stresses in ground parts. Thus developing a robust grinding process while minimizing residual stress is a lengthy trial and error process. This report proposes an analytic model, based on the temperature profile in the workpiece, for predicting the severity of the residual stress under various grinding cycles. Further, the model also comprehends the cumulative effects of multiple grinding passes (which are routinely employed in any production grinding environment) and predicts the final residual stress after the complete process cycle has been completed. In addition to achieving excellent correlation with measured residual stresses, the validity of the model assumptions was evaluated and independently verified.