Affiliations: St.-Petersburg State University, St.-Petersburg,
Russia | Institute for Problems of Mechanical Engineering RAS,
St.-Petersburg, Russia | St.-Petersburg State Technological Institute,
St.-Petersburg, Russia | Wolfson School of Mechanical and Manufacturing
Engineering, Loughborough University, Loughborough, Leics., LE11 3TU, UK
Abstract: 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 this paper 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 cutting speed; he
application of the fracture criterion based on the notion of incubation time
makes it possible 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.
