To realize the high efficiency mirror surface grinding of hard brittle materials (such as nano-ceramic material), this work firstly constructs an experimental platform for workpiece ultrasonic vibration and ELID combined plane grinding according to the processing mechanism of ultrasonic vibration assisted grinding and ELID grinding; then, based on the removal mechanism of hard brittle material, this work analyzes the kinematics of single abrasive grit with workpiece ultrasonic vibration plane grinding, and studies the effect of ELID plane grinding on the grinding depth; finally, based on the above work, this work proposes the mathematical model of material removal rate for the workpiece ultrasonic vibration and ELID combined plane grinding. Experimental results show that the material removal rate of combined plane grinding increases with the increase of the cutting depth and workpiece speed, the material removal rate of ultrasonic vibration and ELID combined grinding is higher than that of ELID grinding under the same conditions.
The optical detection of the crosslinking degree is very important to the forming quality’s on-line control of the hydrogel fibers and tissue engineering scaffolds in 3D printing process at room temperature. For the feature of small scale object, low contrast ratio and unclear outline of the crosslinked area, we processed the crosslinking image with the dual-threshold enhancement method. Firstly, the color image is decomposed into three two–dimensional RGB signals. Secondly, the RGB signals are processed through wavelet transform respectively, and those wavelet coefficients are amplified or reduced with dual-threshold method for the purpose of enhancement and denoising. Then, the new RGB signals are reconstructed by those wavelet coefficients. At last, the new RGB signals are regrouped to get enhanced crosslinking image. Experimental results show that, after processed with this method, the image has a strong sense of color gradation, the details of image are outstanding, and the distinction of the crosslinked zone of the hydrogel fiber is obvious. Moreover, measurement precision of crosslinking degree is improved by 4.58%. This is helpful to improve the performance of the real-time control of crosslinking process.
In order to better reveal the theoretical nature of internal ultrasonic grinding which is an efficient grinding technology, the characteristics of grits motion is analyzed under axial vibration and the grits kinematic equation is established. By using Matlab the single particles trajectory is simulated, then the displacement of a grit is given at any time they contact. Through the theoretical analysis and Matlab simulation, we can achieve that for axial ultrasonic vibration the influences of axial feed on the grits trajectory is too litter to be ignored. So when calculate the contact length of the grinding wheel and the work piece, the grinding wheels axial feed can be neglected. Then the contact length of the grinding wheel and the work piece is achieved. It has a significant value for simplifying the calculation of the grinding force and the analysis of internal ultrasonic grinding.
The oxide layer formed and removed on the surface of the grinding wheel has a significant influence on the grinding quality of ultrasonic-ELID multiplicate grinding. In this paper on the basis of the principles of electrochemical and ultrasonic vibration, the mechanisms of oxide layer formation and remotion were analyzed. Then, the predictive modeling of oxide layer thickness was proposed. The effects of main factors on the oxide film thickness were simulated and analyzed theoretically. The simulation results show that the layer thickness decreases with the decrease of the duty ratio or the grain volume ratio or the ultrasonic frequency ,and the increase of the electrode gap during the composite grinding process.
In order to reveal the theoretical nature of ultrasonic ELID composite grinding which is an efficient grinding technology, this paper theoretically analyzes a single grains motion characteristics in the process of internal cylindrical grinding under axial vibration and established a single grits kinematic equation. Then the grits trajectory is draw by matlab, and the contact length of the grinding wheel and the workpiece is achieved. At the same time the electrolysis parameters are introduced into the dynamic number of effective grits with analysis its electrochemical action. Thereby a force model for the ultrasonic ELID composite internal cylindrical grinding is established. Through analysis the model it is easy to find the force is fluctuated periodically with electrical current changing.
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