Modeling of the instantaneous subsurface damage mechanism of vibration cutting GH4169 based on strain gradient

Nickel-based superalloy GH4169 is widely used in key aircraft engine components due to its excellent thermal strength, stability, and fatigue resistance. However, it is difficult to machine, and ultrasonic vibration cutting is often employed to improve its processability. Sub-surface damage induced during cutting can significantly compromise the fatigue life and reliability of the workpiece. Considering the scale-dependent deformation mechanisms and dislocation behavior in materials, this paper develops an instantaneous sub-surface damage depth prediction model for vibration cutting of nickel-based superalloys based on strain gradient theory. A strain gradient-enhanced constitutive equation for vibration cutting is established with cutting time t as the independent variable. By analyzing real-time cutting force and cutting heat, the coupled effect on sub-surface damage within each vibration cycle is investigated. The von Mises yield criterion is applied, and MATLAB is used to predict instantaneous damage depth. The variation of damage depth with cutting time t is studied, along with its underlying mechanisms. Results show that the maximum instantaneous damage depth occurs when the instantaneous cutting depth peaks. Experimental validation confirms good agreement between predicted and measured damage depths. The key contribution of this work is an instantaneous damage depth prediction model for elliptical vibration machining of GH4169, incorporating strain gradient theory. This model enables the determination of damage depth at different cutting instants, offering insight into damage evolution within each vibration cycle.