Numerical study of chip formation and cutting force in high-speed machining of Ti-6Al-4V bases on finite element modeling with ductile fracture criterion

Abstract

This paper suggests a novel numerical model to accurately simulate the chip formation for a wide range of high cutting speeds. It consists of finite element (FE) modeling of orthogonal machining of titanium alloy (Ti-6Al-4V) in which the Johnson-Cook (JC) material law which can reflect the strain rate hardening and thermal softening influences, and the JC damage law coupled with the displacement-based ductile failure criterion are implemented during the chip formation. Orthogonal machining simulations are performed in a conventional high cutting speed range of 170 to 250 m/min and at the extreme high cutting speeds ranging from 1200 to 4800 m/min, and saw-tooth chips are occurred. The development of chip serration and cutting force are analyzed. It is found that saw-tooth chip formation in high-speed machining of Ti-6Al-4V is the result of ductile fracture. When the cutting speed is increased from conventional to extreme high speeds, the chip morphology changes with varying the fracture behavior. The numerical model is also verified by comparing predicted results with available experimental data in the literature. The results indicate that chip morphology and cutting force can be accurately acquired using the ductile failure criterion in high-speed machining of Ti-6Al-4V.