Study of High Speed Machining by Using Split Hopkinson Pressure Bar

Abstract

The purpose of this paper is to study the effect of cutting parameters such as speed, feed and rake angle on the chip formation mechanism and the main cutting force by simulating an orthogonal cutting operation on a testing apparatus based on a split Hopkinson pressure bar. This device can produce two chips on either sides of the specimen. Cutting tests were carried out on four different materials at different speed feed and tool geometry. Microstructural observations of the chips produced show a change in the morphology of the chip in accordance with the increase of the cutting speed. The chip presents instabilities by adiabatic shearing, without any doubt. It changes from a continuous chip to indented one and to completely sheared off. The Appearance of shear band in the case of indented and completely sheared chip is probably due to strain localization accompanied by a large local growth of the temperature which is a necessary condition to have adiabatic shearing. This phenomenon might be desirable in reducing the level of the cutting forces and by improving chip's evacuation especially in automatic production of parts. Similar results are obtained by .[1] [2] [3] [4] [7]. Cutting force shows a decrease versus the cutting speed. This decrease is more important for larger feeds. The increase of the cutting angle from 5 to 15° also causes a reduction of the cutting force that evolves asymptotically. With high cutting speeds, the energy of plastic deformation in the primary zone of the chip formation is transformed mainly in heat which causes a thermal softening which outweighs the hardening generating therefore a reduction in the cutting force; these results are in accordance with those obtained by .[5] [7].