Prediction of machining induced residual stresses in turning of titanium and nickel based alloys with experiments and finite element simulations

Titanium and nickel alloys represent a significant metal portion of the aircraft structural and engine components and the residual stresses induced by machining are very critical due to safety and sustainability concerns. This paper presents experimental investigations and finite element simulations on turning of Ti-6Al-4V titanium alloy and IN100 nickel based alloy with uncoated and TiAlN coated tools. Face turning of Ti-6Al-4V and IN00 using uncoated tools with various edge radii and TiAlN coated carbide tools is conducted; and residual stresses are measured in radial and circumferential directions using X-ray diffraction technique. 3-D finite element (FE) modeling is utilized to predict forces and machining induced stress fields. The feasibility and limitations of predicting machining induced residual stresses by using viscoplastic finite element simulations and temperature-dependent flow softening constitutive material modeling are investigated. A friction determination method is utilized to identify friction coefficients in presence of tool edge radius. The predicted stress fields are compared against measured residual stresses. Effect of tool edge radius and coating on the predicted stress profiles is also investigated. The results are found useful in predicting machining induced surface integrity that is critical to determine the fatigue life of nickel and titanium alloy components. (C) 2012 CIRP.