Achieving machining residual stresses through model-driven planning of process parameters

The residual stress profile in a machined workpiece is often one of the important integrity attributes because of its direct effect on fatigue life. Machined residual stresses are difficult to predict due to the complicated interactions between chip formation, ploughing, transient stresses distributions, temperature gradients, and material responses during cutting. A fair amount of study has been documented to predict residual stress in a workpiece using analytical, experimental, and numerical modeling methods. However, machining process planning often needs to achieve specified residual stresses by the selection of process parameters and tool geometries. No method has been available that could calculate cutting process and tool geometry parameters based on final residual stresses as pre-specified inputs. This paper presents a physics-based modeling approach to quantitatively suggest the cutting condition and tool geometry parameters according to pre-specified surface residual stresses resulting from machining. To achieve this, inverse calculations procedures for the rolling/sliding contact theory, the McDowell hybrid residual stress algorithm, the specific cutting energy, and the Waldorf slip line model are developed to construct the quantitative model. Experimental data are used for model validation. The outcome of this study provides a methodology for the planning of process parameters and tool geometry to achieve prespecified residual stresses into machined parts.