Papers by Author: Chang Juan Zhang

Abstract: In order to clarify the material removal characteristics of Al₂O₃ engineering ceramics in ultrasonic aided high efficiency lapping, a series of ultrasonic and conventional lapping contrast experiments were carried out on precision lathe with self-made ultrasonic lapping device. The research results show that the value of material removal rate in ultrasonic aided lapping is about 2~4 times that in conventional lapping, especially in ultrasonic axial lapping. In ultrasonic aided lapping, the better removal characteristics can not be obtained by adopting too high or too low lapping parameters, and there are optimum lapping parameters from which a higher material removal rate value can be achieved.

Abstract: Ultrasonic lapping can effectively improve machining efficiency and obtain higher machining precision, which can be as the final process. This paper discusses the ultrasonic lapping mechanism through simulating the lapping tracks. Based on the contrast experiments between common and ultrasonic lapping, the influence of different lapping parameters on material removal rate and surface roughness were studied and the surface microstructure of workpiece was analyzed. The experimental results show that material removal rate of ultrasonic lapping is nearly two times that of the common lapping, especially in ultrasonic axial lapping, and the better surface quality can be obtained during ultrasonic lapping. Meanwhile, the reasons for material removal rate increasing and surface quality improving were analyzed.

Abstract: This paper researched the crack propagation and the variation of microstructure for ZTA ceramics under ultrasonic vibration grinding. To interpret the phenomenon, the nonlocal theory was introduced to establish the constitutive model under the ultrasonic vibration. Grinding experiments on surface quality of nanoZrO2 ceramic are carried out using diamond grinding in different condition, both with and without ultrasonic vibration. Experimental results show the surface quality after two-dimensional ultrasonic assisted grinding is superior to that after common grinding. Meanwhile, the effects of amplitudes and frequencies on ZrO2 ceramics crack propagation were analyzed by SEM. The results show that the crack propagation rate decrease with the amplitudes and frequencies increasing, this is because that the nonlocal attenuation ratio reduced and the nonlocal effects also the strongest. The results of experiments are in accordance with the theoretical conclusions drawn from the nonlocal theory, which verifies that the act ion of ultrasonic vibration can actually postpone the ceramic crack propagation rate.

Abstract: Hard brittle materials have been popular used in manufacture experience because of the excellent performances. However the low plasticity, frangibility and non-conduction make the machining very difficult. Therefore, ultrasonic vibration was introduced to common lapping for the purpose of higher removal rate and fine surface quality. The acoustic model of ultrasonic lapping was proposed, the track equations of ultrasonic lapping with different vibration modes were deduced, the influencing factors of lapping tracks were obtained, and the lapping tracks with different lapping parameters had been emulated. It can be concluded that ultrasonic lapping is a high efficient processing method adapting to ceramic materials.

Abstract: In this paper, the natural frequency and the vibration mode of the lapping tool in ultrasonic vibration lapping are analyzed, the resonance mechanism of the lapping tool is researched by establishing its mechanical model and displacement equation, and the experimental study is carried out in ultrasonic vibration lapping of engineer ceramics. The conclusions include: 1) The natural frequency of the designed lapping tool is ; 2) The acoustic system in ultrasonic vibration lapping is simplified to equivalent many-degrees of freedom system, while the damp is ignored, the lapping tool is resonant with itself-natural frequency, the joint of the horn and the lapping tool is a displacement node, and the whole system is in resonant condition. 3）While the experimental condition is no-load and ultrasonic, the vibration frequency of the lapping tool is 21.3125 , which is further closed to the calculated natural frequency, at that time the amplitude of the lapping tool is maximal and the system is in resonant condition. Moreover, while the resonance frequency of the horn and the lapping tool is different, the good vibration effect of the lapping tool can be obtained by adjusting the excitation frequency of generator.

Abstract: Engineering ceramics have been widely used in recent years because of its excellent performances. However, the high hardness and brittleness make it very difficult to process with high efficiency and good quality, especially in precision and ultraprecision machining. Therefore, a method of ultrasonic drilling and grinding is provided to the hole machining of Al¬2O3 engineering ceramics. In the paper, with different machining parameters, the surface roughness of micro hole in ultrasonic and traditional drilling and grinding is compared and analyzed. Moreover, the surface micro profile and the wear condition of drilling-grinding tool in ultrasonic and traditional drilling and grinding are observed through SEM. Finally, it is concluded that ultrasonic drilling and grinding is a kind of high efficient processing method adapting to micro holes of hard - brittle materials etc.

Abstract: Hard-brittle materials have been popular used in manufacture experience because of their excellent performances. However the low plasticity, frangibility and non-conduction make the machining very difficult, especially in ultra-precise surface fabrication. Therefore, ultrasonic vibration is introduced to conventional lapping for the purpose of proper lapping force, higher removal rate and fine surface quality. Through conventional and ultrasonic lapping experiment of hard-brittle materials with different lapping parameters and different vibration models, the empirical formula of lapping force in ultrasonic lapping is deduced by orthogonal regression analysis, the optimum lapping parameters are put forward and the primary and secondary influencing sequence of parameters on lapping force is presented. Moreover, the influencing rule of different lapping parameters such as rotational speed, feed speed, oilstone grit and lapping depth etc. on lapping force is carried out. Experimental results show that ultrasonic vibration lapping is a high efficient processing method adapting to hard-brittle materials.