Residual stress (RS) on the machined surface is considered a key factor affecting the service performance of components. However, the underlying microscopic mechanism of RS formation on the machined surface, as well as the underlying effect mechanism of ultrasonic vibration, remains insufficiently studied. In this work, a molecular dynamics-based cutting model of polycrystalline nickel-based alloy was established to investigate the thermo-mechanical evolution behavior during the cutting process and its influence on microstructural evolution. The relationship between the post-machining microstructure and RS was also analyzed. The results indicated that surface material is driven into the subsurface during grinding, causing inhomogeneous plastic deformation and vigorous dislocation multiplication and movement. Dislocations induced a certain degree of lattice distortion, and the microscale stress caused by the distortion gradually accumulated to form macroscopic RS. The high instantaneous shear stress induced by ultrasonic vibration promoted dislocation emission, multiplication, and glide. High dislocation density and high dislocation glide velocity led to more intense lattice distortion and a deeper distorted layer, thereby increasing both the magnitude and depth of RS. • The thermo-mechanical evolution behavior during the UVAFG and CG processes was revealed. • Based on molecular dynamics, the relationship between microstructure and the residual stress was elucidated. • A transition in the plastic deformation mechanism under ultrasonic impact was observed. • The microscopic mechanism of ultrasonic-induced generation of higher compressive residual stress was discussed.
Liu et al. (Mon,) studied this question.