Fundamental Research On Rotary Ultrasonic Drilling Of Advanced Ceramics

As one of the cost-effective machining methods for advanced ceramics, rotary ultrasonic drilling (RUD) is a hybrid machining process that combines the material removal mechanisms of conventional ultrasonic drilling and diamond grinding. Compared with conventional ultrasonic drilling, RUD revolutionizes the whole sector both in reducing the cost and in improving the efficiency.Based on the thorough analysis on the state of arts of RUD and the existing problems, the experimental and theoretical studies on RUD are conducted in this thesis. The main work of this thesis can be summarized as follows:1. Under the machining condition of constant feed rate, the effect of RUD and conventional diamond drilling on drilling process are compared. The effects of the process parameters of RUD on drilling process are systematically conducted.2. Based on a single-point diamond grinding model and the elasticity theory, the stress field model in conventional ultrasonic drilling and RUD are deduced. Based on the deduced models and the indentation fracture mechanics, material removal rate (MRR) in RUD being higher than that in conventional ultrasonic drilling is explained.3. Based on the two modes of material removal (brittle fracture mode and ductile mode), two MRR theoretical models in RUD are developed. The influences of parameters (ultrasonic amplitude, ultrasonic frequency, static force, rotating speed, grit number, and grit diameter) on MRR are studied in RUD.4. The tool wear mechanism is studied by using a digital microscope to observe the topography of the diamond tool in RUD of advanced ceramics.5. A new technical method— intermittent rotary ultrasonic drilling (IRUD)— is introduced by improving the conventional tool of RUD. The experiment is conducted to compare the effect of IRUD and conventional RUD on drilling process.Through experimental study and theoretical analysis, the following achievements and conclusions can be obtained:1. Under the machining condition of constant feed rate, RUD is superior to conventional diamond drilling. Compared with conventional diamond drilling, RUD can significantly decrease the cutting force, decrease the surface roughness of drilled holes, and avoid the fracture of advanced ceramics during RUD process.2. Spindle speed, feed rate, and ultrasonic power have significant effects on RUD process...