Abstract: In view of the difficult-to-cut materials such as titanium alloy, the machining method of longitudinal torsion ultrasonic vibration assisted milling (L-TUM) is put forward to realize the anti-fatigue manufacturing. Firstly, the milling process is converted to the oblique cutting model, and a 3D FEM equivalent model of L-TUM is established, it effectively improved the computation efficiency and realized longitudinal torsional ultrasonic vibration and cutting process compound. According to the formation mechanism of the machining induced residual stress (RS), through mechanical and thermal stress loaded and released, the simulation of RS is realized. Then, the difference between the traditional milling and L-TUM is compared from the cutting force, the cutting temperature and the machining induced residual stress, it is concluded that cutting force and temperature are reduced, surface compressive stress and compressive stress layer depth are increased in L-TUM. The experiments are carried out to verify the equivalent model of L-TUM, the results show that the 3D model predicts cutting force, cutting temperature and residual stress with high precision. The influence of tool geometry parameters and ultrasonic characterization parameters on machining residual stress is studied by FEM, It lays a foundation for the compressive stress manufacture of titanium alloy's.

Key words: 3D FEM model, experimental verification, longitudinal torsion ultrasonic vibration assisted milling, model transformation, Ti-6Al-4V