| Nowadays, there are more and more attentions on the precision and ultra-precision processing technology of engineering ceramics parts, and different finishing processing methods have been proposed and put to use. The new developed high efficiency lapping technology with solid diamond abrasive based on traditional free abrasive lapping, possessing both the advantages of ultra-precision grinding and traditional lapping, is suitable for the precision processing of engineering ceramics. For it, the weaknesses of low efficiency, serious waste of abrasive, difficulty to control the quality and so on in the traditional lapping are resolved, and the severe dependence on the environment and machine tool in the ultra-precision grinding is overcomed. Meanwhile, considering the unique advantages of the ultrasonic vibration machining in the processing of hard-brittle materials, in order to ultra-precision lap engineering ceramics parts with high efficiency, a new ultrasonic aided high efficiency lapping technology for engineering ceramics cylinder is developed in this study by combining the ultra-precision lapping technology with the USM technology.Sponsored by Henan Innovative Fund for Outstanding Scholars (No. 0421001200) and Henan Natural Science Fund (No. 0411053500), a series of theoretical and experimental studies on the ultrasonic aided high efficiency lapping mechanism and surface machining quality of Al2O3,ZrO2 and ZTA engineering ceramics are carried out in this project. The main contents of this study are as follows: 1. Ultrasonic aided high efficiency lapping technology of engineering ceramics is put forward and the corresponding machining device is researched to meet the precision machining requirements for engineering ceramics cylindrical parts. The vibration characteristics of acoustic system in the ultrasonic lapping device are clarified on the base of finite element analyses (FEA) and vibration characteristics experiments. The system natural frequencies within the adjustable scope of generator and corresponding vibration modes are analyzed, and the vibration amplitude distribution characteristics along the two paths of diamond pellet installation location in the lapping tool are obtained. The study results provide a powerful guarantee to the research of ultrasonic aided high efficiency lapping mechanism and related experiments.2. Single-grit motion models with additional axial, radial and tangential ultrasonic vibration and without additional ultrasonic vibration are established respectively through the analyses of the movement characteristics in the process of ultrasonic aided lapping of the engineering ceramics cylinder. Based on indentation fracture mechanics and ultrasonic aided pendulum scratch tests with single-point diamond, the material removal mechanisms in the three ultrasonic aided scratch modes are investigated. The reasons that ultrasonic assistance can enlarge the ductile regime are analyzed. Based on the impulse theory and the vibration machining theory, the material removal rate (MRR) models in ductile and brittle regime are established and the influencing factors and rules on MRR in ultrasonic aided lapping of engineering ceramics are discussed qualitatively.3. The effect of lapping parameters on the proportions of ductile removal and brittle fracture removal is discussed experimentally, and the relationship between the ratio of lapping component forces and material removal character is investigated. The characteristic frequency range of material removal is obtained through the time-frequency analysis of the acoustic emission signals in single point diamond pendulum scratch of ZTA engineering ceramics together with the CCI images of scratch marks. The in-process identification system of material removal mode in the process of ultrasonic aided lapping of engineering ceramics is constructed, and the in-process material removal criteria is established based on the wavelet packet frequency band energy decomposition of AE signals.4. The surface processing quality characteristics in ultrasonic aided lapping of ZrO2, Al2O3 and ZTA engineering ceramics are investigated experimentally. The influence rules of different lapping modes and parameters on the surface quality are researched from different aspects including surface topography, surface roughness, surface fractal characteristic, surface residual stress and surface phase structures, etc. The research results show that surface quality is improved to a certain extent for the assistance of ultrasonic vibration.5. The prediction models of surface roughness and material removal rate in the process of ultrasonic aided lapping are built using response surface methodology (RSM). To deal with the relationship between the high efficiency and precision synthetically, taking the maximum material removal rate as target variable and the surface roughness as bounded variable, and considering the actual constraint between the machine tool and the workpiece, the parameters optimization mathematical model is constructed, and the optimized parameters are solved by genetic algorithm (GA) and validated by the contrast experiments.The research results are help to reveal the precision and high efficient mechanism of ultrasonic aided lapping, develop the new technology of solid abrasive lapping of engineering ceramics, and further promote the applications of engineering ceramics.
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