Papers by Author: Xiao Xun Zhang

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Authors: Qiu Hui Liao, Xiao Xun Zhang, Qin Chao Ruan
Abstract: The accurate prediction of warpage of injection molded parts is important to achieve successful mold design with high precision. In this study, effects of polymer-filler properties, such as filler aspect ratio (L/D), filler modulus parallel to major axis (E1) and filler modulus perpendicular to major axis (E2), on warpage displacement of automobile door were studied quantitatively by experimental investigation and numerical simulation. The numerical results are in good agreement with the experimental measurements. It is also found that: (1) the thermal displacement decreases as E1 and E2 decrease, (2) the PVT displacement is not influenced by change of L/D, E1 and E2, (3) the orientation effect displacement is neglected small when L/D=1 and E1= E2, and it also increases as L/D and E1/E2 increase.
2511
Authors: Xiao Xun Zhang, Tuo Lin, Shuang Shuang Zhu, Sheng Ling Zhang, Zhen Wang, Lei Ha
Abstract: Internal cracks in 30Cr2Ni4MoV steel were produced by compressing cylindrical sample with drilled hole. In order to consider the effects of deformation degree, temperature, strain rate and holding time on the crack healing, the hot compression tests were performed on Gleeble-1500 thermo-simulation machine under different process conditions. By in situ observation under optical microscope and scanning electron microscope, effects of process condition on crack healing and the behaviours of crack healing were revealed successfully: (1) the result of crack healing improves as the melt temperature, reduction and holding time increase, (2) the effect of crack healing decreases as the strain rate increases. By the energy dispersive spectroscopy, it is also found that the chemical composition of the healed crack area is different from that of the matrix.
854
Authors: Xiao Xun Zhang, Luo Wang, Qiu Hui Liao
Abstract: Polypropylene specimens were made by the injection molding experiments under different processing conditions. The crystallinity of each polypropylene specimen was obtained using the X-ray diffraction method. The effects of the injection molding processes on the crystallinity of polypropylene were revealed: (1) the crystallinity decreases as the melt temperature increases, and the higher the melt temperature, the slower the crystallinity decreases, (2) the crystallinity decreases as the mould temperature increases, and the higher the mould temperature, the faster the crystallinity decreases, (3) the crystallinity increases as the injection speed increases, and the larger the injection speed, the faster the crystallinity increases. By the tensile experiments of the injection molded specimens, it is also found that the crystallinity has a major impact on the mechanical properties of polypropylene. The yield strength and tensile strength of polypropylene specimens increase as the crystallinity increases.
2809
Authors: Xiao Xun Zhang, Yun Hua Sun, Ye Ling Zhu
Abstract: Prediction and control of the microstructure to improve product performance are very important for the industry practice. In this study, microstructure evolutions of 30Cr2Ni4MoV steel under different conditions were simulated by changing the process parameters using the Deform 3D software. Effects of the forming process parameters on the microstructure were revealed: (1) the higher the temperature and the lower the strain rate, the smaller the strain are needed for the dynamic recrystallization; (2) when strain is enough, the higher the strain rate, the easier the uniform and small grain size can be obtained; (3) under a certain strain rate, the grain size increases as the deformation temperature increases. The microstructure of metal can be predicted and controlled according to the effects of hot forming process parameters on the microstructure evolution.
170
Authors: Xiao Xun Zhang, Chi Ying Ma, Yun Hua Sun, Fang Ma
Abstract: The hot forging process of automobile engine crankshaft was simulated in the present study on the basis of the finite element software DEFORM-3D. The materials of die and crankshaft workpiece are H13 steel and L1438 steel, respectively. The material flow in the die, contact pressure distribution and temperature distribution of the die were investigated. The interaction forces between the workpiece and the dies were mapped onto die faces to serve as load boundary conditions for die stress analysis. The results showed that the die stress reduces with increasing temperature and increases with increasing strain rate. Such behavior is likely associated with flow stress of the workpiece, which reduces with increasing temperature and increases with increasing strain rate. High flow stress results in high die stresses and hence more easily leads to die failure.
1994
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