Papers by Author: Bo Zhao

Abstract: In order to study the states of oxide layer under different pre-dressing process conditions in ultrasonic vibration and electrolytic in-process dressing combined grinding. The effects of electrical parameters, wheel speed, ultrasonic vibration on the oxide layer are investigated with indicators of oxide layer surface morphology and thickness characteristics. The results indicate that the oxide layer thickness increases with the decrease of inter-electrode gap and the increase of duty ratio with pre-dressing time. The effect of ultrasonic vibration cause thinning of the oxide layer. Oxide layer surface morphology allowing processing requirements are obtained by duty cycle of 5μs: 5μs, electrode gap of 0.3mm, wheel speed of 3200 r/min.

Abstract: One-dimensional tool ultrasonic vibration system was designed and manufactured, and the influence law of air gap, axis deviation, axis deflection on the coupling coefficient and the transmission efficiency were studied.The influence of the cross-sectional area, air gap and axis deflection angle on the coupling coefficient and transmission efficiency are very obvious, so must be paid special attention in the design and installation.

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: Residual stress of ceramics ground surface was detected by the X-ray instrument, and it was analyzed in present paper. The experimental results show that the content of metastable tetragonal phase of ZrO₂ and grinding stress are the primary factors which induce martensitic transformation on ZrO₂ ceramics ground surface; during grinding the deeper the grinding depth is, and the bigger abrasive grain size is, the grinding stress in material matrix is larger. After analyzing the influence of grinding parameters on residual stress, it can be found that martensitic transformation can prompt the compressive residual stress to some extent, so as to improve the quality of ground surface.

Abstract: 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.

Abstract: 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.

Abstract: Two dimensional ultrasonic vibration assisted grinding (TDUVG) is analyzed based on theoretical analysis of the cutting trace of a grain in the finished surface, and it gives the kinematical model of single grit during TDUVG, and the condition of the separate cutting is established, so two dimensional ultrasonic vibration are introduced into the system, which helps to form good machining way. Then TDUVG is applied in the ultra-precise machining of nanoZrO₂ ceramics, and grinding experiments on surface quality of nanoZrO₂ ceramics were carried out using diamond grinding both with and without ultrasonic vibration. Experimental results show that the surface quality after two dimensional ultrasonic assisted grinding is superior to that of diamond grinding. As a result, it is suitable for the ultra-precise machining of ceramics.

Abstract: In this paper, we describe a novel encryption algorithm, which converts a greyscale image into a colored JPEG image. Firstly, it creates MCU (Minimum Coding Unit) of the colored JPEG image from the DU (Data Unit) of the greyscale image by the 8x8 construction matrix randomly. Secondly, it shuffles all the DUs with quantized DCT (Discrete Cosine Transform) coefficients according to a random ergodic matrix. Lastly, it rearranges the DUs as the format of the colored JPEG image and proceeds with the normal compression and encoding. The results show that the encryption speed of the algorithm is fast enough for real-time transmission and the encrypted image has almost the same size as original image after direct compression.

Abstract: This paper Studied the milling thickness and milling force on two directions ultrasonic vibration assisted milling. X direction ultrasonic vibration assisted milling periodic can generate periodic separation between the tool tip and the workpiece during the cutting process, so the milling force can be reduced, and the effect of the pulse cutting can be produced. Y direction ultrasonic vibration assisted milling can reduce the average cutting force, and milling width can be increased in Y direction ultrasonic vibration assisted milling, so the surface quality can be improved.

Abstract: The node position of amplitude transformer was determined by the finite element method, and the flange was designed at the nod position for conveniently installation. By the finite element software, the amplitude transformer with flange was optimized and dressed, and its structural parameters were determined. During the actual manufacturing process, it was used impedance analyzer to test its vibration performance, the testing results show that this system vibration performance is good, its resonant frequency is 34.771kHz, anti-resonant frequency is 35.008kHz. The above-mentioned results are very much coincided with the system natural frequency of 34.893kHz which is drew by finite element method. Compared to the traditional dressing this method has many advantages such as convenience, green, environmental protection, low cost and others.