Investigation of Warping Effect on Coupled Torsional-axial Vibrations of Drilling Tool
Koya, Narahara Gopal
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Coupled torsional-axial vibration of the drilling tool plays a significant role in the machining dynamics of the drilling process. The torsional-axial vibration of the drilling tool due to the warping deformation of the pretwisted flute is modeled in this thesis. The warping dependent cross sectional properties of the drill flute are obtained from proposed 2D finite element method. Natural frequency and mode shape corresponding to the torsional-axial vibration of the drill are predicted with experimental validation. The effects of helix angle, web thickness and aspect ratio on the coupled torsional-axial dynamics are analyzed for conventional and micro drills. The proposed model is able to provide optimum geometric configuration of the drilling tool for required torsional-axial dynamic behavior with high computational efficiency, and guide the drilling process in order to reach desired hole quality. Clamping boundary conditions highly influences the drilling tool dynamics. An enhanced receptance coupling model is developed to predict coupled torsional-axial vibrations of the drilling tool considering the dynamics of fixing structure and clamping conditions. Rigid and flexible receptance coupling methods are used to predict the dynamics of the drilling tool including the joint dynamics between the tool and the tool-holder. Experimental validation of the predicted results indicates the efficiency of the proposed model in obtaining the exact dynamics of the drilling tool considering the clamping boundary conditions.
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