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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. [ABSTRACT FROM AUTHOR]

Carbon fiber–reinforced plastics (CFRP)/titanium alloy (Ti) stacks are extensively applied in the aerospace industry due to their excellent mechanical properties. However, their poor machinability poses great challenges. In this study, longitudinal-torsional ultrasonic vibration drilling (LT-UVD) is innovatively introduced to improve the quality of CFRP/Ti drilling. First, the separation mode of LT-UVD is analyzed by kinematic equations. Then, an experimental platform is built based on the LT-UVD vibration actuator to perform CFRP/Ti drilling experiments. The thrust force, interface temperature, hole wall quality, hole defects, Ti chip morphologies, and tool wear in LT-UVD are experimentally compared against conventional drilling (CD) and longitudinal ultrasonic vibration drilling (L-UVD). The experimental results show that, compared with CD and L-UVD, the thrust force of CFRP in LT-UVD decreases by 20.36–40.55% and 2.04–14.61%, while the thrust force of Ti decreases by 19.08–24.83% and 1.95–9.34%. Moreover, a relatively low maximum interface temperature is achieved in LT-UVD. In addition, the hole size accuracy, surface roughness for the hole's inner surface, and delamination factor are improved in LT-UVD. Fiber pullout defects, chip-breaking performance, and tool wear of CFRP are improved due to torsional vibration in LT-UVD. Finally, according to the high-speed camera, damage forms of the interface area are different when drilling CFRP/Ti stacks with various drilling sequences. [ABSTRACT FROM AUTHOR]

This paper aims on slicing of monocrystalline silicon wafers using a newly developed diamond multi-wire reciprocating saw under ingot rocking process. A contact wire length model based on ingot rocking was established. The influence of motion parameters of ingot rocking on the surface quality of multi-wire sawn monocrystalline silicon wafers had been experimentally studied. The slicing surface morphology, surface roughness, and surface hardened layer were investigated by using scanning electron microscope, laser scanning microscopy, and microhardness tester. Results show that compared with the multi-wire cutting mode with an ingot rocking amplitude of 0°, ingot rocking (θm ≠ 0) can reduce the contact wire length of sawing by almost half at any time, and realize discontinuous and segmented sawing of large-diameter silicon wafers. By reducing the contact wire length, the cutting mode under ingot rocking can achieve better surface morphologies, and reduce roughness, thickness of the hardened layer and microhardness of the surface in silicon wafer cutting. Compared with the mode of multi-wire reciprocating sawing with an ingot rocking amplitude of 0°, an ingot rocking amplitude of 5°can reduce roughness, thickness of the hardened layer, and microhardness of the surface in silicon wafer cutting about 30.1%, 20.1%, and 11.3%. Though the ingot rocking amplitude did not significantly influence the contact wire length during the cutting process, the ingot rocking motion significantly influences the ingot feed speed, an ingot rocking amplitude of 5°instead of 3° or 7° is suggested for the best surface quality. [ABSTRACT FROM AUTHOR]