Predictive modeling of residual stress in minimum quantity lubrication machining

Residual stress is one of the critical characteristics for assessing the surface integrity of machined components as it poses a strong bearing on the service quality, functionality, and life of the machined components. The machined-in residual stresses can be affected by cutting parameters, tool geometry, material properties, and lubrication conditions. A physics-based relationship between residual stresses and processing conditions could support process planning in achieving desirable part quality and functionality. This paper presents an analytical model that predicts the residual stresses in machining under minimum quantity lubrication (MQL) condition as functions of cutting parameters, tool geometry, material properties as well as MQL application parameters. Both the lubrication and cooling effects caused by MQL air–oil mixture contribute to changes in friction due to boundary lubrication as well as changes in the thermal stress due to heat loss. The cutting force and cutting temperature are coupled into a thermal–mechanical model which incorporates the kinematic hardening and strain compatibility to predict the resulting residual stress under lubricated conditions. The residual stress prediction model is verified for orthogonal tube facing of TC4 alloy. The predicted residual stresses captured the measured results well in terms of the trend and magnitude.