Severe tool wear is always considered as a main negative result in the process of drilling Ti-6Al-4V alloy. Although the idea of employing one-dimensional longitudinal ultrasonic vibration in the drilling process to reduce tool wear has been proposed for many years, studies on longitudinal-torsional composite ultrasonic vibration–assisted drilling (LT-UAD) are seldom reported. LT-UAD is a hybrid machining process in which high-frequency and low-amplitude vibrations are superimposed simultaneously on the rotational direction and the axial direction of the drilling bit respectively. In this study, a hollow vibration converter with thread grooves is presented for LT-UAD purpose. Based on an in-depth kinematic analysis, a condition for separating the tool from the workpiece is derived, indicating that a lower feed rate, a lower spindle speed, and a higher amplitude are more advantageous. Machining experiments are performed, wherein good agreement is found between the experimental and theoretical results. The results show that LT-UAD has obvious advantages over longitudinal ultrasonic vibration–assisted drilling and conventional drilling in reducing tool wear. Additionally, the influences of the vibration amplitude, spindle speed, and feed rate on the flank wear width are analyzed, revealing the influences of the three factors in descending order are feed rate, amplitude, and spindle speed. The optimum machining parameters are obtained as 23 μm of amplitude, 385 r/min of spindle speed, and 0.06 mm/r of feed rate. Furthermore, a reliable regression model of flank wear width is established based on response surface methodology. With this prediction model, the flank wear width of drill bit under different machining parameters can be accurately predicted.

严重的工具磨损一直被认为是Ti-6Al-4V合金钻孔过程中的主要不利结果。尽管已经提出了在钻削过程中采用一维纵向超声振动来减少工具磨损的想法，但是很少有关于纵向扭转复合超声振动辅助钻探（LT-UAD）的研究报道。LT-UAD是一种混合加工过程，其中高频和低幅振动分别同时叠加在钻头的旋转方向和轴向上。在这项研究中，提出了一种带有螺纹槽的中空振动转换器，用于LT-UAD。根据深入的运动学分析，得出了将刀具与工件分离的条件，表明进给速度较低，主轴转速较低，振幅越高越有利。进行机加工实验，其中在实验结果和理论结果之间找到了很好的一致性。结果表明，LT-UAD与纵向超声振动辅助钻孔和常规钻孔相比，在减少工具磨损方面具有明显的优势。此外，分析了振动幅度，主轴转速和进给速率对侧面磨损宽度的影响，揭示了降序进给速率，幅度和主轴速度这三个因素的影响。最佳加工参数为振幅为23μm，主轴速度为385 r / min，进给速度为0.06 mm / r。此外，基于响应面方法建立了侧面磨损宽度的可靠回归模型。有了这个预测模型，