Abstract
This paper presents an investigation of the effect of tool rake angle in single point diamond turning (SPDT) of silicon using experimental and simulation methods. Machining trials under the same cutting conditions were carried out using three different rake angle tools. In order to delve further into the rake angle effect on the output parameters including material removal, stresses and crack formation, at the onset of chip formation and steady-state conditions, a simulation study using smoothed particle hydrodynamics (SPH) approach was performed. The simulation results were incorporated and found in good agreement with experimental observations. The results indicate that diamond tool wear rate and surface generation mechanism significantly vary using different rake angle tools. The continuance of compressive and shear deformation sequence at the chip incipient stage governs the high-pressure phase transformation (HPPT) as a function of rake angle and tool wear. The capability of diamond tool to maintain this sequence and required hydrostatic pressure under worn conditions is highly influenced by a change in rake angle. The proportional relationship of cutting force magnitude and tool wear also differs owing to disparate wear pattern which influence distribution of stresses and uniform hydrostatic pressure under the tool cutting edge. This subsequently influences structural phase transformation and therefore frictional resistance to cutting. Mainly frictional groove wear was found dominant for all diamond tools in machining of silicon.
Highlights
Single crystal silicon is considered an ideal material in microphotonics and weight-sensitive infrared applications due to its low mass density, high refractive index and low thermal expansion coefficient
Due to the high anisotropy of single crystal silicon, machining mode is dependent on crystallographic orientation based on the orientation of dislocation and slip system relative to cutting direction
The effect of tool rake angles was investigated in Single point diamond turning (SPDT) of silicon using experimental and simulation methods
Summary
Single crystal silicon is considered an ideal material in microphotonics and weight-sensitive infrared applications due to its low mass density, high refractive index and low thermal expansion coefficient. SPDT of silicon is inherently a complex process that includes chipping, brittle fracture, ductile deformation, chemical reaction and phase transformation as a function of cutting parameters, material orientation and tool geometry. From the tool geometry perspective, negative rake angle tools were found to generate high hydrostatic pressure required for structural transformation of silicon ensuing brittle to ductile transition (BDT). Diamond tools with negative rake angle are assumed to provide cutting edge strength against any chipping or abrasive damage and more control on an abrupt tool wear. In SPDT of silicon, diamond tools with intermediate negative rake angle from − 20° to − 50° are considered ideal for ductile mode machining. In this paper, smoothed particle hydrodynamics (SPH)based numerical simulation study using Drucker-Prager (DP) material constitutive model was conducted in conjunction with machining experiments to investigate the effect of different rake angle tools. The experimental and numerical simulation results were evaluated by analysing the cutting force magnitude and trend, chip formation, surface finish and tool wear
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