Effects of Machining Parameters on the Microhardness of Chips

It has been found that the shear strain acceleration governs the machining parameters like tool-chip interface temperature, shear angle, tool wear, etc. It is therefore speculated that microhardness of the chips for the same machining conditions but for different shear strain accelerations would be different. To test this hypothesis, experiments have been conducted using mild steel as work material and cemented carbide bits as cutting tools. Experiments were performed in two ways: longitudinal turning and accelerated cutting. Chips were collected at the same machining conditions but at different shear strain acceleration. Microhardness of the chips has been measured using the Leibtz-microhardness tester and the results have been analyzed using a computer program CADEAG-1. Using the responses (i.e., microhardness), mathematical models have been evolved. Effects of different parameters (cutting speed, feed, etc.) on the microhardness of the chips in all the three cases (i.e., longitudinal turning, facing, and taper turning) have been studied. It has been concluded that the microhardness of the chips obtained during accelerated cutting is governed by the shear strain acceleration and its governing parameters.