Numerical prediction of machining induced residual stresses when hard cutting AISI 4140

Abstract

In today’s manufacturing industry, there is a clear focus not only on the accurate manufacturing of geometrically dimensional workpieces but also on maintaining strict tolerances on workpiece rim zone properties. These workpiece rim zone properties, such as grain sizes, deformation zones or, in particular, residual stresses, are generally summarized under the term Surface Integrity. While changes in the Surface Integrity properties of the machined surface can have positive effects, such as compressive stresses induced by hammering, there is at the same time a risk of lasting damage to the rim zone due to a negative change in these properties. As a consequence, a weakening of the workpiece rim zone may later on lead to component failure. For this reason, the design of manufacturing processes for safety-critical components according to the current state of the art is complex, time-consuming and cost-intensive, as it is largely empirical and based on experience. Knowledge-based prediction of process-induced changes in Surface Integrity changes, on the other hand, enables process design times to be shortened and process quality to be increased at the same time. The basis of such a knowledge-based process design is, on the one hand, the knowledge of the physical interactions and, on the other hand, an adequate description of these interactions within the framework of either analytical or numerical models. With the aim of predicting the occurring residual stresses after hard machining of hardened AISI 4140, a numerical chip formation and residual stress model is presented in the following paper and subsequently validated with the aid of experimental test data.