Observations of the tool-chip boundary conditions in turning of aluminum alloys

Interface boundary conditions are critical to the determination of the tool temperatures and stresses which in turn are needed to design better tools and select better cutting conditions. Friction at the interface has been studied for 60 years and yet the accurate modeling of friction has presented a formidable challenge, especially in operations such as turning where the interface is inaccessible due to the continuous contact between chip and tool. A historical perspective of friction in machining is provided to better evaluate the purpose of this article. The contradictions arising in the assumptions regarding friction are analyzed. This is substantiated by experimental observations regarding seizure and sliding and their domains of validity at the interface. This paper concentrates on turning operations in the machining of aluminum workpieces using carbide cutting tools, at a range of speeds common to conventional practice.