Predictive modeling of material removal modes in micro ultrasonic machining

This paper presents a model to predict ductile and brittle material removal modes when a brittle material is impacted by a single sharp abrasive particle in micro ultrasonic machining process. Analyses are performed based on the basic indentation fracture theory for hard angular particles. The conditions required for occurrence of both ductile and brittle removal during the interaction between sharp particles and brittle materials in micro ultrasonic machining are discussed. Subsequently, the quantitative criteria for brittle-ductile transition in material removal are presented using the threshold kinetic energy in promoting radial and lateral cracks. Finally, the adequacy of the proposed model is verified by the experimental results from single particle impingements in micro ultrasonic machining. In the experiments, polycrystalline diamond particles ranging from 0.37 to 3 mu m are used for processing of single crystalline < 100 > silicon and fused quartz. The ultrasonic frequency at 50 kHz is introduced at the horn tip which is set at amplitude from 0.8 to 4 mu m. The constellation of the experimental results clearly showed good agreement on the basis of comparative principle for the model validation. The outcome of the present research work can be used as an important platform to build reliable models for prediction of material removal rate based on the mode by which material removal takes place in micro ultrasonic machining process. The proposed model can be employed to enhance surface quality as well as process productivity. (c) 2012 Elsevier Ltd. All rights reserved.