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

Abstract

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 which are base hole drilling assisted with ultrasonic vibration (UVAD) and hole expansion by helical milling assisted with low-frequency torsional vibration (LFTVAHM). Based on this process, the cutting trajectory modeling is established, and the hole-making experiment on TiBw/TC4 composites is conducted. The experimental data shows that 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 of high-quality hole-making of difficult-to-machine materials in practical engineering applications.