Energy based analysis of ultrasonically assisted turning
|Effect of material feeding rate on average cutting force as a function for ultrasonically-assisted cutting of aluminium; Comparison of calculations (solid line) and experimental data.||Effect of ultrasonic vibration amplitude on cutting force. Comparison of calculations (solid line) and experimental data for turning ofaluminium.|
The process of ultrasonically-assisted turning (UAT) is a superposition of vibration of a cutting tool on its standard movement in conventional turning (CT). The former technique has several advantages compared with the latter, one of the main being a significant decrease in the level of cutting forces. In our investigation the effects observed in UAT are analysed employing ideas of dynamic fracture mechanics. The active stage of loading duration depends heavily on ultrasonic frequency and the feed rate of specimen (cutting speed).
An application of fracture mechanics and use of special dynamic fracture criterion based on the notion of incubation time makes it possible to give a new explanation of the effect and to calculate a dependence of this duration on its threshold amplitude. An estimation of energy, necessary to create a threshold pulse in the material, is made by solving the contact Hertz problem. The obtained time dependence of energy has a marked minimum. Thus, the existence of energy efficient loading duration is demonstrated. This explains the decrease in the cutting force resulting from superimposed ultrasonic vibration. The obtained results are in agreement with experiments on ultrasonic assisted machining of aluminium and Inconel 718 alloy. The research is performed jointly with the International Centre of Vibro-Impact Systems, Loughborough University, Leicestershire, UK. More details can be found here.