Prediction of critical cutting depth for ductile-brittle transition in ultrasonic vibration assisted grinding of optical glasses

The modes of material removal in machining of brittle materials consist of ductile mode and brittle mode. It is believed that there is an obvious distinction between the energy expenditures in these two modes. In this paper, the specific energies expended in ductile and brittle modes removal are modeled as a function of ultrasonic vibration parameters, grinding parameters, and work-material intrinsic properties. An approach to predict the critical cutting depth for ductile-brittle transition in ultrasonic vibration assisted grinding of glasses is proposed based on the analytical expressions for the specific cutting energies consumed in ductile and brittle modes of machining. The critical cutting depth is identified at the point where both curves of specific energies expended in ductile and brittle modes intersect. Scratching tests of BK7 and JGS1 optical glasses are conducted to verify the validity of the proposed model. Experimental results are found to correspond well with the predicted data.