Numerical Simulations of 3D Tool Geometry Effects on Deposition Stresses in Diamond Coated Cutting Tools

Diamond-coated cutting tools are attractive alternatives to polycrystalline diamond tools for machining lightweight, high-strength components made of advanced materials such as composites. However, residual stresses induced by the diamond deposition process, due to thermal mismatch between diamond and the substrate, significantly impact the coating-substrate adhesion, and thus, the tool performance in machining. Moreover, the tool geometry, particularly at the very tip, complicates the stress fields because of the sharp geometry changes. The objective of this research is to investigate the effects of critical tool geometry parameters on the residual stress augmentations in diamond coated cutting tools. In this study, computer-aided design (CAD) software was used to create the solid model of various tool geometries. It was used to create an accurate model of the tool, which emulates each aspect of the tool geometry, e.g., as small as 5-micron edge radius on a 12.7-mm tool. The solid model was then exported to finite element analysis (FEA) software for 3D simulations of residual stresses generated in the tool with given deposition conditions. The obtained stress data was transformed to evaluate the interface stress profiles around the tool edges. To systematically investigate the tool geometry effects, a test matrix, determined using the design of experiments approach, includes 4 factors (edge radius, relief angle, corner radius, and corner angle) and 2 levels with a full factorial design. Analysis of variance was performed to quantitatively reveal the significant factors and interactions between the factors that dominate the stress concentrations. Results are summarized as follows. (1) The cutting edge radius is the most significant factor to the interface stresses. (2) For a 5 μm edge radius, the radial normal stress (σ_Γ) increases from 0 at the top uniform surface to about 1.5 GPa in tension, and the circumferential normal stress (σ_θ) increases from around 3.0 GPa in compression to over 3.7 GPa. (3) The corner radius is of secondary importance to σ_Γ, and the relief angle is of secondary importance to σ_θ.