Influence of the metallurgical transformation induced by grinding on the residual stresses computation

Grinding is one of the important metal cutting processes used extensively in the finishing operation to get components of desired shape, size and accuracy. A perfect control of this process is thus necessary to ensure correct final part and limit damage. Lifetime of machined part depends on the surface integrity especially in terms of microstructure changes and residual stresses. The best way to control those factors is to study the way they appear. Thus, it is important to set up experimentation to get the maximum informations during the grinding process, with in situ measurements and after, on the final surface. On one side, forces and power were measured, on the other side temperature measurements were conducted using an infrared digital video camera. In fact the grinding temperature and the temperature gradients are the major factors which influence surface integrity. Experimentations show white layers in the near ground surface and the measured temperature is higher than the austenitizing temperature. The workpiece subsurface was then characterized by observing and measuring microstructural changes of surface layer. Numerical simulations, using SYSWELD software are performed to formalize what is modeled. Metallurgical transformation is then taken into account in the grinding FE model. The comparison showed that numerical model is capable to accurately predict the white layer thickness and residual stresses values.