Experimental Study On Ultrasonic Elliptical Vibration Assisted Turning Of Slender Shaft

The slender shaft is typically defined as a shaft part possessing a length-diameter ratio greater than 20. It mainly serves to the mechanical connection and transmission system. A wide range of applications can be found in the fields of civil engineering,mechanical engineering, aviation and aerospace industry, etc. Since the slender shaft is characterized by the large aspect ratio, poor rigidity and high axial linear expansion, it is susceptible to the bending deformation arising from the cutting force and the cutting heat in the conventional machining process. As a result, it is difficult to reach a sufficient high accuracy level. In order to tackle these problems of turning slender shaft,we introduce a ultrasonic elliptical vibration assisted turning processing method(UEVT) herein. In essence, the impact energy is applied on the cutting unit in pulse by exerting a periodical and continuous impact force on the workpiece, leading to a repeat contact-separate cutting motion between the tool and workpiece.To the author’s knowledge, the experimental study concerning assisted turning based on back-plane ultrasonic elliptical vibration has been a subject of rather limited research work. In this work, we first analyze the principles and characteristics of the ultrasonic elliptical vibration assisted turning. Then, we measure the amplitude of ultrasonic elliptical vibration assisted turning tool unit by using laser Doppler vibrometer, and investigate the power supply of different ultrasonic amplitudes in three directions. These efforts contribute to the theoretical and experimental bases for the ultrasonic vibration turning of slender shaft. Moreover, the ultrasonic elliptic vibration vibration assisted turning experiment involving slender shaft(6061 aluminum alloy) is fully developed and implemented. We carry out the comparative experiment between the ordinary cutting and ultrasonic elliptic vibration assisted turning, which compares the cutting force and surface roughness of different area of the slender shaft obtained by employing the two different processing methods. In addition, we further use the three-way dynamic dynamometer(Kistler, 9257B), the surface roughness measuring instrument and the digital microscope to measure and compute the cutting force,surface roughness, surface texture and chip morphology of new proposed method. The experimental results show that, under the same cutting parameters, the cutting force in three directions in UEVT are relatively smaller than the counterparts of CT, and they will further decrease with the increase of amplitude. The surface roughness of themiddle region is worse than the slender shaft at both ends. However, for UEVT, it turns out that the uniform consistency of the surface roughness along the longitudinal direction of the slender shaft(reflected by the surface roughness coefficient of variance)is better than ordinary turning. It is observed that the surface grains of UEVT is more meticulous and the breaking effect of the chips shows a better performance than the normal turning. It is worth noting that the chip generated from CT is continuous resulting in a heavy winding phenomenon whereas the chip generated from UEVT is of the intermittent form and this broken effect of chip enhances with the increase of the amplitude.Finally, a preliminary experiment was carried out for the typical slender shaft with ultrasonic vibration assisted turning. According to the two different dimensions and accuracy requirements of the given slender shaft parts which combines ultrasonic vibration-turning, we present a special jig and proper technological methods. The development of different processing routes and processing programs to achieve the size and precision requirements of the drawings.