Experimental research on new hole-making method assisted with asynchronous mixed frequency vibration in TiBw/TC4 composites

Abstract

With the gradual promotion and the application of difficult-to-machine materials such as titanium matrix composites in the aerospace field, high-quality hole-making technology has become a major demand in aviation manufacturing. In order to improve the hole-making quality of TiBw/TC4 composites, asynchronous mixed frequency vibration-assisted hole-making (AMFVAHM) method is proposed. The process consists of two steps: ultrasonic vibration-assisted drilling (UVAD) base hole and low-frequency torsional vibration-assisted helical milling (LFTVAHM) target hole. Based on this process, the cutting trajectory modeling is established, and the hole-making experiment on TiBw/TC4 composites is conducted. The experimental data show that during the hole expansion stage, the maximum XY-plane average milling force decreases by 30.96% and the maximum axial average milling force decreases by 24.49% compared with conventional helical milling (HM) when the torsional vibration frequency and the milling frequency are the same in LFTVAHM. The hole-making experiment shows that AMFVAHM can reduce the chip size, tool wear, and some other defects such as entrance/exit burrs, scratches, and fractures of the hole wall. Comparing with HM and UVAD, the verticality of hole wall increases by 71.43% and 86.21%, the inlet damage decreases by 27.98% and 31.60%, the outlet damage decreases by 2.80% and 14.47%, the hole wall roughness (Ra) decreases by 36.29% and 63.43%, and the maximum white layer thickness decreases by 19.99% and 67.66%. Meanwhile, AMFVAHM process not only reduces the cutting force and cutting temperature but also improves the hole-making quality due to the fretting friction effect of LFTVAHM in secondary hole expansion, which meets the need for high-quality hole-making of difficult-to-machine materials in practical engineering applications.