Residual Stress Modelling in Cylindrical Grinding of an Alloyed Steel

Abstract

Grinding is a cost-intensive machining process, often carried out in the final stages of manufacturing. Improperly performed grinding can induce residual tensile stresses in the workpiece, potentially leading to its rejection and the loss of already invested resources. Additionally, residual tensile stresses adversely affect the component’s service life, particularly if induced at the surface.

This study proposes a novel modelling methodology, referred to as the Unified Contact Length Model (UCLM), to predict the residual stress state induced by external cylindrical grinding of an AISI/L6 cylindrical component. The methodology is realised within a modelling framework that integrates the three residual-stress-inducing mechanisms to investigate the impact of key process parameters on residual stresses. The selected key process parameters are the feed rate and the work speed, as they are known to affect the resulting residual stresses.

The three considered mechanisms are plastic deformation due to abrasive grain contacts, thermal expansion and contraction of the workpiece surface, and phase transformation-induced volume changes. First, a Cutting Model featuring a single abrasive grain is developed using the SPH (Smoothed Particle Hydrodynamics) method. Subsequently, a data-driven surface load model is established based on the contact forces simulated with the Cutting Model and an analytically calculated con-tact area. Stresses caused by phase transformation-induced volume changes in the metal are accounted for by modifying the coefficient of thermal expansion based on the phase volume fractions. A moving heat flux representing the thermal effects of grinding, leading to thermal expansion and contraction, is then developed. Finally, all sub-models are incorporated into a two-dimensional finite element implementation of the UCLM under plane strain conditions.

The model has been validated by comparing the residual stress profiles it produces under different process parameters to those obtained from experiments conducted using a grinding machine. Both the feed rate and the work speed affect the residual stresses. The residual stresses on the surface of the workpiece increase with higher feed rates, as do the subsurface residual stresses. As work speed increases, surface residual stress decreases, while subsurface residual stress increases. Furthermore, feed rate and work speed interact, so changing one parameter alone may not yield the desired outcome when controlling the grinding-induced residual stresses.