Papers by Author: Ya Zhou Sun

Abstract: In this paper, according to the principle of building the constitutive model of polymer material, the one-dimensional structure of the ZWT material constitutive model is added to dashpot element in parallel, and in which strain rate and coefficient of viscosity is introduced and the nonlinear viscoelastic constitutive model of Polycarbonate material is achieved. Additionally, tensile test at low strain rate and Hopkinson test at high strain rate of polycarbonate material are carried out, and the change rule of yield strength of polycarbonate material is obtained both at high strain rate and low strain rate. According to the experimental data, the parameters of the constitutive model have been optimized and fitted using ant colony algorithm, and then the fitted results are compared with experimental results. The comparative results show that the improved ZWT constitutive model can reasonably represent the nonlinear characteristics of polycarbonate material at different strain rate.

Abstract: An experimental study of quartz glass grinding with ultrasonic torsional vibration assistance is presented. The grinding forces and surface roughness are measured. The results show that the grinding force and surface roughness with ultrasonic torsional vibration assistance are much less than those in conventional grinding. The grinding force increases with the feed rate of workpiece and the depth of grinding, and decreases with the speed of wheel spindle. This research indicates that the ultrasonic torsional vibration-assisted grinding can enhance grinding performance and be an effective method for the machining of hard and brittle materials.

Abstract: This essay briefly introduces a structure scheme design of a high diameter-length ratio rotary plate. This structure scheme is unique from any well-known schemes. In this scheme, there is only one flat act as the working flat for both main thrust bearing and aux thrust bearing. It minimizes the faces which need lapping. At the same time, this scheme minimizes the number of assembling parts. So, it will be easier for this scheme to achieve high accuracy. This essay includes the process of design: calculation for bearings and schemes compare.

Abstract: Laser cooling is one of the critical problems in the research of high power semiconductor lasers. This paper provides an overview of microchannel heat sink which is used to cool the high power semiconductor lasers. The method of polishing after cutting is the current processing method of the heat sink, which is because the ordinary cutting method cannot meet the requirements of high quality of surface and edge burrs. This paper proposes ultra-precision fly cutting method for heat sink machining to omit the polishing processing to improve the machining efficiency, and verifies by experiments that the feasibility of the processing method and the edge quality improved by workpiece superposition processing method.

Abstract: Dynamic properties of mechanical joint surfaces are researched, majorly contains the study of basic mechanism and factors affect the dynamic properties of joint surfaces. Equivalent stiffness and damp are analyzed. Orthogonal experiments are arranged in order to analyze the weight of every major factor that affects the joint surfaces dynamics. Two common materials HT200, 2Cr13 under different processing methods, surface roughness and surface areas are used.

Abstract: An experimental study of grinding force in microgrinding zirconia ceramics using small grinding tool is presented. In the experiments, the grinding tool used is electroplated diamond microgrinding wheels of 0.41, 0.63 and 0.76 μm in diameter, and the machining operations were conducted in side grinding under dry cutting. The process parameters include the diameter of the microgrinding wheel, feedrate, and rotational speed of the grinding spindle. The microgrinding forces were measured by a Kistler three-component dynamometer. The experimental results show that the normal forces are much larger than the tangential forces, the effects of process parameters selected on the variation of experimental results is almost the same for tangential forces, and that is the feedrate, diameter of the microgrinding wheel and rotational speed of the grinding spindle in turn for normal forces. As the feedrate increases or diameter of the wheel increases, the microgrinding forces increase, and the magnitudes of increase are more significant at higher radial grinding depth.

Abstract: The machining-induced residual stresses are strongly dependent on the work-piece material and the chosen process parameters. A 2D finite element (FE) model of ultrasonic vibration assisted micro-milling (UVAMM) is established using ABAQUS. Johnson-Cook’s work-piece material and shear failure principle are used, while friction between tool and work-piece uses modified Coulomb’s law whose sliding friction area is combined with sticking friction. By means of FE analysis, the influence rules of spindle speed, vibration frequency and work-piece material on the surface residual stresses are obtained, which provides a basis for choosing optimal process parameters and improving the longevity and reliability of micro-component.

Abstract: In order to analyze the dynamic mechanical property of steel 4340 during its micro-milling, finite element method is used to simulate the process of elastic-plastic micro-milling. The curves of logarithmic strain, plastic strain, strain rate changing as cutting time goes on are shown in the process of simulation, with the distribution of logarithmic strain, plastic strain, equivalent plastic stain and stain rate analyzed. The results provide a basis for the further reaserch of materials’ dynamic mechanical properties during their cutting process.