Visualization of Stress Distribution by Photoelastic Method Under Ultrasonic Grinding Condition

Abstract

This study investigates phenomena in ultrasonic vibration-assisted grinding. The appropriateness of a stress visualization method is proven through comparison of a Hertzian contact stress analysis using finite element methods. The stress distribution on soda-lime glass caused by a 3-mm-diameter diamond electro-deposited wheel is visualized using a photo-elasticity method. The study compares the local stress concentrations caused by grains with and without ultrasonic wheel vibration. The global reaction force is measured by a dynamometer. The ultrasonic vibration leads to a reduced fluctuation of force, as well as a reduced time-averaged force. It is thought that the ultrasonic vibration causes a smaller local stress beneath the grains, which generates chips. In contrast, typical photo-elasticity methods are applicable for plane stress conditions. However, the stress distribution in a workpiece under a face grinding condition is distributed three-dimensionally, and the stress distribution cannot be recognized directly from the phase difference. Assuming that the stress distribution is sufficiently stable in a wheel rotation, continuously-captured images can be reconstructed to produce a 3D stress distribution, using computed tomography. The experimental tomographic images show a spatially-dispersed phase difference image caused by the electro-deposited wheel, with several discontinuous diamond grains on the end face of the wheel.