Abstract
The micro-groove structure on the planar surface has been widely used in the tribology field for improving the lubrication performance, thereby reducing the friction coefficient and wear. However, in the conventional cutting (CC) process, the high-quality, high-precision machining of the micro-groove on titanium alloy has always been a challenge, because considerable problems including poor surface integrity and a high level of the material swelling and springback remain unresolved. In this study, the ultrasonic elliptical vibration assisted cutting (UEVC) technology was employed, which aimed to minimize the level of the material swelling and springback and improve the machining quality. A series of comparative investigations on the surface defect, surface roughness, and material swelling and springback under the CC and UEVC processes were performed. The experimental results certified that the material swelling and springback significantly reduced and the surface integrity obviously improved in the UEVC process in comparison to that in the CC process. Furthermore, for all the predetermined depths of the cut, when the TSR (the ratio of the nominal cutting speed to the peak horizontal vibration speed) was equal to one of twenty four or one of forty eight, the accuracy of the machined micro-groove depth, width and the profile radius reached satisfactorily to 98%, and the roughness values were approximately 0.1 μm. The experimental results demonstrate that the UEVC technology is a feasible method for the high-quality and high-precision processing of the micro-groove on Ti-6Al-4V alloy.
Highlights
Titanium alloys have been increasingly used in aerospace, aviation, shipbuilding and biomedical fields because of their excellent properties such as high yield stress, high toughness, high strength to weight ratio, high creep and corrosion resistivity and good biocompatibility [1]
The results showed that, due to the influence of the ultrasonic elliptical vibration assisted cutting (UEVC) technology, the cutting forces reduced, the critical cutting depth increased and the machining accuracy of the micro-groove improved
The deviation value reached 20%, when the predetermined depth of the cut was 8 μm. This can be explained by the fact that the increase of the predetermined depth of the cut led to an obvious increase in cutting forces and the friction force, the cutting temperature was higher, which greatly increased the level of material swelling and springback
Summary
Titanium alloys have been increasingly used in aerospace, aviation, shipbuilding and biomedical fields because of their excellent properties such as high yield stress, high toughness, high strength to weight ratio, high creep and corrosion resistivity and good biocompatibility [1]. The surface hardness of titanium alloy is not usually high (approximately 30 HRC), which leads to a poor wear resistance of the titanium alloy part [2,3]. The failure of titanium alloy part is often caused by its poor wear resistance [4,5]. The studies on the improvement of the wear resistance of titanium alloy hold great significance for improving its reliability and service life. The micro-groove structure has been proven to be useful for improving the lubrication performance during the wet sliding contact condition, thereby reducing the friction coefficient and wear [6]. Numerous fabrication technologies have been proposed for the machining of the micro-groove, including lithographic machining [7], micro electrical discharge machining [8], micro electrochemical
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