Papers by Author: Dun Wen Zuo

Abstract: It is one of the difficult problems in the manufacture of the integrated aircraft part of Machining distortion caused by residual stress. According to the characteristics of aluminum alloy pre stretched thick plate, the modified removal method for measuring residual stress in thick pre-stretched aluminum plates is proposed and the stress-strain relation matrix is deduced by elasticity theory. Moreover, the residual stresses in the specimen of 7075T7351 plate is measured by the proposed method, and the results are finally analyzed and compared with the data obtained by other methods. The results indicate that the proposed method is effective in measuring the residual stress in thick pre-stretched aluminum alloy plates. The measurement results can be used for the quantitative analysis of aerospace parts machining distortion caused by residual stress, and it has higher value in engineering application.

Abstract: Ti-Si-C films were prepared on cemented carbide by chemical vapor deposition. The reactive gas system was CH₄, (CH₃)₄Si, TiCl₄ and H₂. The film was analyzed and tested by SEM, AFM, EDS, XPS, microhardness tester, friction and wear tester. The results indicate that the film is continuous and dense. At higher substrate temperature, the hardness of the film will be higher. When the substrate temperature is 850°C, the adhesion of the film is highest with coefficient of friction only 0.14.

Abstract: A discretization method is used in pre-stretching simulation to separate an aluminum alloy thick plate into layers. When the equivalent plastic strain in each layer is defined according to the residual stresses during quenching, the yield strength model can be developed to estimate its yield strength. Again, the curve of elasticity modulus is fitted in the light of the experimental data, which can reveal how the elasticity modulus changes with plastic deformation. Finally, in consideration of the non-uniformity of yield strength and elasticity modulus, the pre-stretching of the quenched 7075 aluminum alloy thick plate is taken as an example to numerically simulate the value and distribution of residual stresses at the pre-stretching ratio of 1.8%, 2.2% and 2.5%, respectively. It is known from the simulated results that, by using the proposed method in this paper, the obtained results of the distribution and magnitude of the residual stresses are in good agreement with the experimental measurements.

Abstract: This paper established the model base, knowledge base, application base and test base for the cold extrusion process of internal thread and developed decision support system which realized the centralized management of related information for cold extrusion process of internal thread, maintained the consistency of data in real time and enforced the degree of information sharing. By using of the decision support system, expert system, intelligent inference technology and depending on the application requirements of the system, the overall structure of the decision support system for cold extrusion process of internal thread was established based on J2EE technology. Two accessorial decision-making methods of hybrid forecasting and application modification facilitated modeling the system business. Three-dimensional frame structure was used to represent the application example of the internal thread by cold extrusion process and to achieve the application type, information scalability of internal thread by cold extrusion process. Hybrid fast predicting mechanism which was the dynamic integration of internal thread by cold extrusion process knowledge and instance inference was applied to seek the optimal degree of internal thread by cold extrusion process.

Abstract: This report describes a two-dimensional monitoring system for milling machines using small-diameter tools. Small-diameter tools are used for high-speed milling, and they are indispensable for high-quality and high-productivity manufacturing. However, tool breakage occasionally occurs, and this becomes a serious problem in automated production. This study aims to develop a system for monitoring the cutting state that can prevent tool breakage. The proposed system consists of two charge-coupled device (CCD) cameras, an image processing device, a man-machine controller (MMC), and a machining center with an open computer numeric (CNC). This monitoring system is connected to the machining center by Ethernet. It enables the precise measurement of tool deflection during high-speed milling. In an experiment, we applied this system to the end milling of a steel plate under different cutting conditions, and we examined the relationship between tool deflection and the cutting conditions. In addition, we applied this monitoring system to measure tool wear, and we examined the relationship between tool deflection and tool wear. It was found that the proposed system enabled in-process monitoring of the cutting state and tool wear.

Abstract: The necessity of fixed abrasive CMP in polishing semiconductor materials processing was analyzed. Compared the shortcomings of traditional free abrasive polishing with the advantages of fixed abrasive polishing, the applications of fixed abrasive polishing technology in semiconductor processing were described. A variety of fixed abrasive polishing pad production methods were introduced. The development trend of fixed abrasive polishing was prospected.

Abstract: Milling process of jointing blank of 7022 aluminum alloy was simulated by ANSYS. The results show that the maximum residual tensile stress and pressure stress are mainly concentrated in the jointing seam zone when the jointing blank is milled. The milling deformation of jointing blank is shown as “wave” shape. The milling deformation of key eye side is shown upwarp. The jointing initiating terminal is shown downward displacement. The maximum downward displacement is present to the middle of jointing seam central line. In additional, the milling deformation along sheet length direction is shown outward extension.

Abstract: This paper comprehensively uses a combination of methods of theoretical analysis, numerical simulation as well as the model test to do the structural analysis to some type of the passenger cabin doors, so as to set up the model for the descriptions of the part subjected to explosion impact loading; Through the tests, we gets the explosion impact loading and other important physical parameters. Aimed at the material of the door as well as the simplified models subjected to the explosion impact loading, the numerical simulation is put up by the finite element software ABAQUS. The necessity of the reinforcement is deeply analyzed as well as the difficulties during the process of the reinforcement, furthermore, the reinforcement measures are proposed to the airliner door. Keywords: Numerical simulation; Explosion impact loading; Explosion-combustion power equipments

Abstract: Nanocrystalline diamond film was deposited on silicon by double bias hot filament chemical vapor deposition (HFCVD) system. The effect of substrate temperature on the microstructure and mechanical properties of the film were investigated systematically. More defects and non-diamond contents were found as the decrease of grain size, which cause the decrease of hardness and elastic modulus. It is shown that the proper substrate temperature is in the range of 720~760 . The excessively high substrate temperature leads to the °C dramatic increase of nondiamond content and the decrease of mechanical properties.

Abstract: In the process of modeling the squashed piece of powders for the simulation of the temperature field of laser cladding, the metallurgical model and the pore model were proposed separately. The effects of the organizational form, the contact resistance and the thickness of the squashed piece of powders on the temperature were considered. Different values of physical parameters of the squashed piece of powders were converted, different contact resistances were calculated and the laser absorptivity for different process parameters of laser cladding was determined. The temperature curves of six typical nodes and the temperature gradient of two nodes in the molten pool of the substrate were discussed from different aspects.