Structural and Smart Materials II

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Authors: Bin Hong, Zhen Dong Gao, Jian Ye Gao, Ya Ji, Shun Ya Lv
Abstract: Due to its specific structural features, the packaging technology is quite essential for the conductive slip-ring (CSR) encapsulating with epoxy molding compounds (EMC). In this work, a modified vacuum packaging technology has been proposed which includes a pouring process and a followed soaking process. Based on the experimental results; the reliability of the CSR packaged obtains a significant improvement as its thermal stability and electric insulating property are obviously advanced, comparing with that fabricated by the normal vacuum packaging method.
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Authors: Jiao Yan Yu, Duan Wei Shi, Zhi Li, Shuang Yang Yu, Yang Zhang
Abstract: The crack repair experiment with argon arc welding technology was carried out to repair large cracks in the large-module gear and rack of the shiplift. The experiment studied the influence of process parameters including welding current and prehearing temperature on the properties of the weld by using 40CrMo piece with pre-made cracks as the substrate material and TIG-R30 wire. In addition, Rockwell hardness tester and material high temperature performance tester were used to test the hardness and tensile properties of the weld. The result shows that the best performance of the welds was obtained when the welding current was 150A, the preheating temperature was 100°C and the argon flow was 15L/min. At this point, the hardness of the weld was 12.8% higher than that of the substrate with the tensile strength reaching 786Mpa, the elongation being 8% and no cracks or pores.
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Authors: Yun Hai Jia, Jian Mei Guo, Yan Guo, Fan Yu
Abstract: With the demand of modern cutting technology for ‘high efficiency, precise, flexibility and green manufacturing’, polycrystalline diamond materials as cutting tools have been widely used in automobile, aerospace and non-metal processing. Electro-spark erosion is one of the most effective ways to machine polycrystalline diamond materials. Single pulse discharge is one of the research foundations of micro-EDM. Using 2 micron granularity polycrystalline diamond as experiment material, the influence of single pulse discharge technology on the removal efficiency of materials was studied, such as pit radius, pit depth and radius-depth ratio, etc. The experimental results show that, with the extension of the pulse duration, the radius of the discharge pit begins to increase rapidly, then slowly increases, and finally to slow down; while the radius of thermal influence zone increases rapidly and then continues to increase slowly. With the extension of pulse duration, the ratio of pit depth to radius changes within the range of 0.05 ~ 0.25, which shows a downward trend basically.
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Authors: Ran Zhu, Yong Kang Zhang, Gui Fang Sun, Pu Li
Abstract: The confined laser shock peening (LSP) is an innovative surface treatment technique designed to improve the fatigue performance of materials by imparting compressive residual stresses into materials. A 3D finite element model was developed to predict the surface residual stress and plastically affected depth of the TC11 titanium alloy after LSP. The modeling procedure consists of two successive explicit analysis steps. The performance of finite element model was verified by comparing simulated results with the experimental data. With the validated finite element model, the influence of the process parameters (LSP path, thickness of the sample, number of impacts) was investigated on the surface residual stress and plastically affected depth of the TC11 titanium alloy after LSP. Some simulated results can be used to mentor the optimization of the process parameters of LSP.
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Authors: Xia Zhu, Keiji Ogi, Nagatoshi Okabe
Abstract: The hardness test, Charpy impact test, and axial expansion experiment were performed on a medium carbon steel S35C specimen typically used for shaft materials after first subjecting it to quenching and tempering heat treatment under different heating temperatures/time conditions. The effect of the tempering conditions on the mechanical properties of the specimen and the limit of the diameter-enlarged ratio used for evaluating the workability of the partial diameter-enlarged were investigated. The summary of the results are as follows: after quenching at 880 °C, a fine troostite or sorbite structure was obtained under all heat treatment conditions at heating temperatures of 550 °C to 675 °C, and heating times of 0.5 h to 1.5 h. An improvement was shown in the limit of the diameter-enlarged ratio because the quenching and tempering heat treatment led to an increase in the Charpy impact value/ductility as well as a reduction in the hardness, tensile strength, and yield strength; the partial diameter-enlarged process could be performed on the heat treated material at almost the same deformation speed as a cold-drawn material with a much lower axial pressure; it was possible to estimate the diameter-enlarged deformation behavior using the tempering parameter M. We confirmed that the quenching tempering heat treatment performed in this study facilitates the improvement of the workability of the diameter-enlarged.
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Authors: Xia Zhu, Keiji Ogi, Nagatoshi Okabe
Abstract: This study focus on the diameter-enlarged ratio, which is an important parameter for evaluating the workability of a partial diameter-enlarged process. Moreover, the study attempts to explain the influence of the fillet radius of the die end on the fatigue characteristic of the test piece after forming and the limit of the diameter-enlarged ratio without fatigue damage in the forming process. Three types of dies with different fillet deformations were used, and tensile tests were carried out after the processing was performed on three types of carbon steel. The fatigue properties of the test specimens after forming and the limit of the diameter-enlarged ratio at which no fatigue damage occurred were investigated. The results obtained are as follows: increasing the fillet radius of the die helped to ease the stress concentration at the root of the diameter-enlarged part, and shaft diameter-enlarged processing could be done without fatigue damage. Using a die having a radius equal to or larger than the appropriate fillet radius helped to increase fatigue strength, without causing fatigue damage, even if the diameter-enlarged ratio increased; notch sensitivity increased with an increase in the diameter-enlarged ratio, but the apparent notch sensitivity coefficient decreased with an increase in fillet radius in all the test pieces. A large limit for the diameter-enlarged ratio without fatigue damage may be obtained by using a die with an appropriate fillet radius.
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Authors: Xia Zhu, Keiji Ogi, Nagatoshi Okabe
Abstract: The purpose of this research is to determine the state inside the material using finite-element analysis and to improve the performance of a rotary-draw bending forming by clarifying the mechanism of wrinkle generation. An analytical model of rotational drawing was made by using the general-purpose nonlinear finite-element analysis software MSC Marc, and the analytical results were compared with experimental results to verify the validity of the model. Furthermore, the mechanism of wrinkle generation was investigated. With the progress of processing, wrinkles occur not in the R part but in the original tube-side straight-tube part. The coefficient of friction between the tube material and the R portion of the bending mold promotes the occurrence of wrinkles and the growth of the generated wrinkles. Because wrinkles occur even if the friction coefficient between the tube material and bending mold R part is ignored, the generation condition of wrinkles also depends on parameters other than the friction coefficient.
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Authors: Kun Liang Zhang, Bin Hong, Li Peng Zhang, Ya Ji, Zhen Dong Gao, Jian Ye Gao
Abstract: Based on its specific structural features, the packaging technology is extraordinary significant for the conductive slip-ring (CSR) encapsulating with epoxy molding compounds (EMC). In this work, a modified vacuum packaging technology has been proposed which includes a pouring process.By the construction of the relevant models, the packaging technology was calculated by MATLAB and discussed. It indicates that the EMC can be easily poured into the concentric ring slit of the CSR only with a differential pressure of 200 Pa between the outside pressure and the inside pressure. On the bases of the experimental results; the EMC can easily flow up from the bottom to the top of the CSR packaging mold vertically.
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Authors: Li Peng Zhang, Bin Hong, Kun Liang Zhang, Jian Ye Gao, Ya Ji, Zhen Dong Gao
Abstract: Due to its specific structural features, the packaging technology is extraordinary significant for the conductive slip-ring (CSR) encapsulating with epoxy molding compounds (EMC). In this work, a modified vacuum packaging technology was put forward for which includes a soaking process.By the construction of the soaking models, the packaging technology was calculated by MATLAB and discussed. The soaking model reveals that the soaking time is strongly influenced by the space of the exhaust vent and the added pressure. When the soaking pressure is set at 6 atm with the vent of 0.02 mm width, the EMC can be completely soaked into the tiny spaces of the CSR in 5 min.
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