Modeling of the in-plane biaxial residual stresses from machining

It is well known that machining processes create residual stresses in the surface of machined components. Depending upon their nature, these residual stresses can have significant effects upon component life by influencing fatigue, creep, and stress corrosion cracking resistance. In addition, machining-induced residual stresses can have detrimental effects upon component geometry and result in parts that do not meet specified tolerances. Thus it is of significant industrial importance to predict the nature of machining-induced residual stresses in a component based upon the machining conditions and material behaviors which give rise to them. A feasible and accurate method of prediction does not currently exist.; Research will be presented which serves to address this need for a predictive model. Experimentation on orthogonal and controlled oblique machining indicates a simplification in the expression of residual stresses when viewed from a workpiece coordinate frame. Further experimentation on turning and endmilling processes demonstrate the extension of this simplification to conventional machining processes. A one-dimensional rationale based on a careful treatment of the mechanics of residual stress formation provides general guidelines for the development of machining-induced residual stress and demonstrates the pronounced effect of a thermal mechanism in the generation of machining-induced residual stress. A predictive model coupling the thermal and mechanical mechanisms of residual stress generation provides predictions of the temperatures developed in the workpiece surface and the full in-plane residual stress profiles existing at and beneath the newly generated surface. Experiments on orthogonal machining, controlled oblique machining, turning and endmilling serve to evaluate the predictive model for residual stress. The results show great promise for understanding the development of machining-induced residual stress and optimizing conventional machining processes.; In addition, novel experimentation has been conducted to demonstrate the effects of machining-induced residual stress on part warpage. The experimentation indicates the strong influence of machining-induced residual stresses on component geometry. Finite element solution techniques are utilized to predict the part warpage resulting from the machining-induced residual stresses. The predicted results show strong agreement with the experimentation and serve to demonstrate the use of the warpage prediction in a production environment.