Abstract:
Carbon fiber reinforced polymer (CFRP) is widely used in the aerospace industry, and drilling process is a critical process in component assembly. Due to the high abrasiveness of carbon fibers, tool experiences rapid wear during drilling process, compromising hole quality. Low frequency vibration-assisted drilling can reduce friction and extend tool life by enabling periodic contact and separation between the tool and workpiece. However, conventional sinusoidal vibration lacks flexibility in adjusting contact duration. This paper proposes replacing the single sinusoidal waveform with higher-order shapes to optimize duty cycle (M1~M4 with duty cycles of 0.35, 0.39, 0.419, and 0.452 respectively), aiming to reduce tool-workpiece contact duration and thereby mitigate tool wear. The experimental results indicate that the thrust forces and torques of different vibration shapes are similar for the first 10 holes. When reaching the 20th hole, the higher-order vibration shape M1 demonstrates reductions in thrust force and torque by 9.92% and 11.99% respectively compared to the conventional vibration shape M0 (with a duty cycle of 0.419). Tool wear is primarily dominated by abrasive wear, accompanied by chip adhesion. Compared to the M0 vibration shape, the M1 vibration shape reduces flank wear by 43.82%, exhibits a smaller hole diameter and roughness value variation range, and decreases the exit delamination factor by 10.6%. In summary, reducing the duty cycle can reduce drilling force and tool wear while improving hole quality. The optimized high-order vibration shape M1 demonstrates enhanced effectiveness in suppressing tool wear and machining defects. The research results provide a reference for the optimization of high-order vibration shapes in the low frequency vibration-assisted drilling process of CFRP.