Siva Venkatachalam

Effects of Ploughing Forces and Friction Coefficient in Microscale Machining

This paper discusses the effects of ploughing and friction in microscale machining. The friction coefficient has previously been shown to be sensitive to the geometry of the abrasive particle and the depth of indentation. From a micromachining standpoint, the friction coefficient is modeled to be a function of the tool edge radius and the undeformed chip thickness, wherein the tool edge is modeled as a sliding cylinder on a flat workpiece. The contributions of ploughing force, which assumes significance in microscale machining, are better modeled using an integration approach over the edge of the tool. Two force models for the estimation of ploughing forces are compared, wherein one model uses a slip-line field analysis and the other uses a method of force balance on the deformation boundary. Basic microcutting (shaping) experimental data are presented and compared to the prediction results. The results show that a nonuniform friction coefficient improves the predictability of the force model.

Microstructure Effects on Cutting Forces and Flow Stress in Ultra-Precision Machining of Polycrystalline Brittle Materials

This paper presents a physics-based analysis to quantitatively describe the effects of grain size, grain boundaries, and crystallographic orientation on the flow stress of the polycrystalline material and thereby on the cutting and thrust forces. The model has been experimentally validated, in terms of the force intensities and sensitivities to microstructure attributes such as the grain size and the misorientation by comparing the forces to measured data in micromachining of polycrystalline silicon carbide (p-SiC). Molecular dynamics (MD) simulations are performed to explore the effects of grain boundaries and misorientation and to validate the modeling analysis in the context of resulting force ratios. [DOI: 10.1115/1.4029648]