Papers by Author: Wei Min Zhang

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Authors: Cheng Yu Wang, Chen Min, Xiong Guoxing, Wei Min Zhang
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Authors: Dong Ying Ju, Wei Min Zhang, Y. Matsumoto, Ryuji Mukai
Abstract: The objective of this paper is to extend the capability of analyzing the time dependence and coupling of temperature, stress and strain effects on the macroscopic and microscopic structures subjected to quenching, and to introduce a theory of the kinetic of the phase transformation. Strain due to phase transformation, transformation plasticity and thermal expansion are the dominant factors that need to be included in the simulation of a quenching process. The evolution of the microstructure also influences the constitutive equations. In particular, as the temperature changes from the high to phase transformation, temperature and then room temperature, the stress-strain relationship changes from elastic-plastic strain. Therefore, in order to obtain a high strength and ductility in carbon steels, transformation plasticity often has a major effect in increasing of the residual stress during quenching process. In this paper, we measured temperature change and distortion occurring during the quenching process of a carbon steel(SCr420) by thermal simulation machine (Gleeble 1500) are used to determine the parameter of transformation plasticity due to the generation of martensite. The modeling of martensitic transformation plasticity is also verified by using of computational simulation of the quenching process.
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Authors: Nai Lu Chen, Wei Min Zhang, Qiang Li, Chang Yin Gao, Bo Liao, Jian Sheng Pan
Abstract: In order to investigate the flow rate distribution and improve the flow rate uniformity of the quenchant in a quench tank, the ultrasonic Doppler velocimeter (UDV) was used to measure the flow rate of quenchant with agitation, and then a computational fluid dynamics (CFD) simulation was carried out to simulate the flow rate distribution without / with flow baffles. According to the CFD simulation results, the structures and positions of flow baffles in the draft-tube were optimized to obtain the uniform flow rate distribution in the quench zone, which were verified by experiments as well. The simulation and experimental results show that the UDV is suitable for measuring the flow rate of a large-size quench tank. This research provided a solid foundation for optimizing the structure design of flow baffles in production quench tanks.
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Authors: Yong Qiang Long, Ping Liu, Wei Min Zhang
Abstract: The micro structural evolution and the mechanism of recrystallization grain growth were studied during re-aging process in Cu-Ni-Si alloy containing finely pre-aging δ-Ni2Si precipitates using computer simulations based on a diffuse-interface phase-field kinetic model. In this model, the temporal evolution of the spatially dependent field variables is determined by numerically solving the time-dependent Ginzburg-Landau (TDGL) equations for the structural variables. The simulation results quantify the effects of the precipitation on recrystallization. It is shown that the finely dispersed pre-aging δ-Ni2Si precipitates exert a strong pinning effect on the recrystallization grain boundaries. The recrystallization grain growth for r = 3 fa = 0.015 can be described as R =1.04∗t 0.33 at the beginning, followed by a gradual transition to growth stagnation. The final grain size follows a Zener type relation lim 0.49 1.41 a R r f =     for 0.01 ≤ fa ≤ 0.21 and r = 2.5 or 3.
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Authors: Wei Min Zhang, Ye Ma, Lin Lin Li
Abstract: A fluid dynamic model was set up to describe the flow field of gas in a large sized pit type carburizing furnace when large sized gears were being carburized. The commercial software Fluent was adopted to carry out 3 dimensional computational fluid dynamics (3D-CFD) simulations of the gas flow field under different, actually four kinds of , furnace designs in this article. The flow fields of the carburizing gas around the part were analyzed. According to the simulations and analysis, it was shown that the number of fans on gear’s carburizing is not a primary factor, using a air inducting tub can improve the carburizing process significantly and proper loading tray design can also be positive. The results indicate that the simulation provides a reference to the furnace’s design optimization.
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Authors: Nai Lu Chen, Wei Min Zhang, Chang Yin Gao, Bo Liao, Jian Sheng Pan
Abstract: In order to investigate the effects of probe geometric shape on cooling curves of quenchants, the ISO Inconel 600 alloy probe and a flat probe (Dimension: 120 mm × 120 mm × 20mm, phase-transformation free CrNi-steel) were both adopted to measure the cooling curves of oil, water and aqueous polymer quenchant. By comparing and analyzing the cooling rate curves measured by the two kinds of probes, it can be found that the shape of water and oil’s cooling rate curves obtained using different probes are almost same. While those for the aqueous polymer quenchant are not, especially at the initial cooling phase. During the initial cooling phase the cooling rate measured by the flat probe fluctuates in a narrow range, whereas this phenomenon couldn’t be seen while using the ISO Inconel 600 alloy probe. The reason could be contributed to the geometric shape difference of the two kinds of probes and the property of inverse solubility of the aqueous polymer quenchant. In order to illustrate the inverse solubility property of the aqueous polymer quenchants the probe geometric shape should be considered.
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