Papers by Author: H.X. Wang

Abstract: Molecular techniques are transforming our understanding of cellular function and disease. However, accurate molecular analysis methods will be limited if the input DNA, RNA, or protein is not derived from pure population of cells or is contaminated by the wrong cells. A novel Ultrasonic Vibration Microdissection (UVM) method was proposed to procure pure population of targeted cells from tissue sections for subsequent analysis. The principle of the Ultrasonic Vibration Cutting is analyzed, and a novel microknife is designed. A multilayer piezoelectric actuator is used to actuate a sharp needle vibrating with high frequency and low amplitude (Approx. 16–50 kHz, and 0-3μm) to cut the tissue. Contrast experiment was done to test the feasibility of UVM method. Experimental results show that the embedded tissue can be quickly and precisely cut with the ultrasonic vibration micro-dissection method.

Abstract: The method of single point diamond turning is used to machine KDP crystal. A regression analysis is adopted to construct a prediction model for surface roughness and cutting force, which realizes the purposes of pre-machining design, prediction and control of surface roughness and cutting force. The prediction model is utilized to analyze the influences of feed, cutting speed and depth of cut on the surface roughness and cutting force. And the optimal cutting parameters of KDP crystal on such condition are acquired by optimum design. The optimum estimated values of surface roughness and cutting force are 7.369nm and 0.15N, respectively .Using the optimal cutting parameters, the surface roughness Ra, 7.927nm, and cutting force, 0.19N, are obatained.

Abstract: In this work, a coupled thermo-mechanical plane-strain large deformation FE cutting model is developed to simulate diamond turning based on the updated Lagrangian formulation. As expected, the effects of friction coefficient on cutting forces, chip deformation, cutting temperature, flow stresses and shearing angle are investigated by FE simulations. The simulated results can be adopted as a reference to select the reasonable friction coefficient in diamond turning process.

Abstract: In precision turning, the quality of surface finish is an important requirement for machined workpiece. Thus, the choice of optimal cutting parameters is very important for controlling the required surface quality. The focus of the present study is to find a correlation between surface roughness and cutting parameters (feed rate, depth of cut) and nose radius in turning 3J33 maraging steel, and to derive mathematical models for the predicted surface roughness based on both of cutting parameters and nose radius. The experimental design is carried out using the quadratic rotary combination design. The regression analysis shows feed rate and nose radius influence surface roughness significantly. With F-ratio test the proposed model is adequate. The method could be useful in predicting roughness parameters as a function of cutting parameters and nose radius.

Abstract: In this paper, mechanical characteristics of KDP crystal anisotropy are analysed theoretically. Vickers indentation experiments are adopted to validate the variation rule of hardness and fracture toughness in different orientation of KDP crystal plane (100), and a model to calculate critical cutting thickness of brittle-ductile transition is proposed for the KDP crystals. The result shows that, on the crystal plane (100), the minimum value of critical cutting thickness of KDP crystal in brittle-ductile transition appears in the direction [110], but the maximum appears in the direction [010]. Finally, the ultra-precision machining of KDP crystal is performed, and the results agree well with the theoretical conclusions. Super-smooth surface with a roughness RMS of 6.6nm is reached as machined in the crystal direction [010], and 11.2nm to the direction [110].

Abstract: In order to avoid the stochastic damage of micro cleavage on cutting edge, a brittle-ductile transition lapping mechanism is proposed for the mechanical lapping of single crystal diamond cutting tools to direct the tools lapping. As expected, the critical depths of cut for brittle-ductile transition in different orientations and on different crystal planes are calculated. According to the theoretical results, the actual dynamic depth of cut is controlled within the critical depth of cut, which ensures that the tool lapping is carried out in ductile regime and the changes of cutting edge radius characterize with some specific time laws in lapping. Therefore, the time series and nonlinear least square methods are used to analyze the changing laws of cutting edge radius. As a result, a coupled model to build a bridge between the cutting edge radius changes and lapping time is developed. In terms of this developed model, a required cutting edge radius restricts a tool’s lapping time. Above all, the cutting edge radius is known in advance and has no needs measuring. So the production efficiency of diamond cutting tools is improved and its production cost is reduced accordingly.

Abstract: In this paper, a new cutting force model is presented for diamond turning, and the ‘size effect’ is also integrated into this new model. Utilizing this new model, the effects of feed rate and depth of cut on cutting forces are analyzed, the specific law of cutting forces in micro thin-layer metal cutting is investigated at the same time. Through the detailed theoretical analysis and experimental validations, it is found that if the selected feed rate or depth of cut is less than a certain value, a particular phenomenon will appear, thus the thrust cutting force Fp is greater than the principal cutting force Fc, especially when the depth of cut or feed rate is of the same order as the rounded cutting edge radius. For the micro thin- layer metal cutting, the smaller the feed rate and depth of cut, the greater is the influence of these two parameters on cutting forces.

Abstract: In this paper, Based on regression analysis of tests, three comprehensive experimental models were presented in precision turning high-strength spring steel, Vicker’s hardness, residual stresses and surface roughness can be predicted utilizing these models. And the influence of tool geometry on machined surface integrity was analyzed systematically. The analytical results show that Vicker’s hardness and compressive residual stress will increase with the decrease of rake angle, clearance angle, cutting edge angle or minor cutting edge angle, surface roughness increases with an increase of rake angle or clearance angle and decreases with an increase of cutting edge angle or minor cutting edge angle.