Abstract
Titanium alloy (Ti) has been widely used in aerospace industry due to excellent mechanical properties and the demands of Ti parts with a high length-to-diameter ratio and a large diameter are increasing. However, deep hole drilling of large-diameter Ti holes is usually both time-consuming and cost-consuming due to a series of problems such as unfavorable chip removal, helical structure on the hole surface, poor hole precision and severe tool wear. This paper reports on the cutting mechanism and experimental results of low-frequency vibration-assisted single-lip drilling (LFVASLD) of large-diameter Ti holes (O17mm) for the first time. In this paper, a novel rotary low-frequency vibration device was developed and the vibration generation mechanism was analyzed. Thereafter, the material removal mechanism of LFVASLD was established. Then, the comparative experiments between LFVASLD and conventional single-lip drilling (CSLD) of Ti were conducted. The experimental results show that, compared with CSLD, LFVASLD can significantly prolong the drilling depth by 9 times due to reduced tool wear and alleviate helical structure on the hole surface due to the separated cutting mode. Furthermore, the influence of drilling parameters in LFVASLD on hole quality were also investigated. It is concluded that, the LFVASLD method is suitable for deep hole drilling of large-diameter titanium alloy and the developed rotary low-frequency vibration device can be used as a machine tool accessory to significantly improve the processing capacity in the industrial practice.
Highlights
This paper investigated the feasibility of low-frequency vibration-assisted single-lip drilling (LFVASLD) of largediameter titanium alloy for the first time
This suggests that conventional singlelip drilling (CSLD) process is not competent for machining larger-diameter titanium alloy deep holes
In the paper, an innovation LFVASLD device was developed firstly, and its feasibility was verified by the comparative experiments
Summary
The requirement of titanium alloy holes with a high length-to-diameter ratio (L/D>50) and a large diameter (D> ∅15mm) is increasing for airplanes and ships. In the deep hole drilling process, a single-lip drill with an asymmetrical single-edged design is commonly employed [4]. The unfavorable long and continuous chips mixed with cutting fluid are ejected along the tool straight flute during deep hole drilling with a single-lip drill. Chip jamming problem is induced, which can significantly deteriorate hole quality and reduce tool life as well as process efficiency. It is generally considered that chip removal during the single-lip drilling is the key factor for hole quality, tool wear and process stability in this process [5]
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