Von Mises Stress of Mandible

D2 Cold work steel is used for production of forming tools. Machining of this type of material is difficult because of built-up transformational stress and thermal shock in the work material during machining. Possibility of austenite retention in this material promotes formation of continuous type of chip. This causes difficulty during chip disposal. Present paper illustrates an experimental investigation on different parameters which affect the cutting process and also cause significant response on the process of chip formation during machining of D2 cold work steel. D2 cold work steel was machined under different cutting velocity at constant depth of cut and constant feed rate. Brazed carbide tool was used for machining without the use of coolant. It was found that chip thickness and Von Mises stress reduce with increase in cutting speed. Further, chip samples were collected and examined under SEM and optical microscope and it was found that cracking at the chip top surface occurred because of thermal shock/ transformational stress. Moreover, globular carbides were observed in the chip microstructure during chip formation. I. INTRODUCTION D2 cold work steels are usually obtained in quenched and tempered condition and at this state some amount of retained austenite is usually found in this steel. These steels are sensitive to thermal shock. D2 steels have poor thermal conductivity and low heat absorption ability. Gitonde et al [1] studied about the effect of depth of cut and machining time on machinability aspects like power, surface roughness, cutting force, machining force and tool wear of AISI D2 steel material and came to the conclusion that machining force and power linearly increase upon certain depth of cut and then decrease Takacs and Farkas et al.[2] studied about the hard turning of AISI D2 steel and came to the conclusion that passive force is most dominant force component and they also concluded using FEM model that the theoretical cutting forces are 45-120% more than the measured forces. Arsecularatne et al. [3] studied about the parameters of machining of AISI D2 steel with PCBN tools and found that highest tool life and volume of the material removal rate can be obtained at the lowest speeds and higher feed values. Davim and Figueira [4] studied about the turning of hardened tool steel using ceramic tool without coolant over the traditional turning and cylindrical grinding practice in terms of increased productivity and reduced power consumption and they found that tool wear is highly influenced by cutting velocity. Tang et al. [5] performed finite element modelling and simulation in dry hard orthogonal cutting of AISI D2 tool steel with CBN tool and came to the conclusion that shear angles increase abruptly up to certain depth of cut with small increments in cutting speed but after that it decreases when certain value of depth of cut is reached. They also found that temperature in the machined surface first decreases and then increases with increase in depth of cut. In this study, an effort has been made to study about the cutting parameter effect on the von Mises stress, chip thickness etc. and chip formation mechanism was also studied through SEM examination and optical microscopy.