Papers by Author: Da Hai Zhang

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Authors: Chun Jun Liu, Yue Zhang, Da Hai Zhang, Zhong Ping Li
Abstract: In this paper the composite fracture process has been simulated via the finite element method. A micromechanics model was developed to predict the stress-strain response of a SiO2f/ SiO2 composite explicitly accounting for the local damage mechanisms such as fiber fracture and interfacial debonding. The effects of interfacial strength and fiber volume fraction on the toughness of fiber-reinforced ceramic matrix composites were investigated. The results showed that the composite failure behaviors correlated with the interface strength, which could achieve an optimum value for the elevation of the composite toughness. The increase of fiber volume fraction can make more toughening contributions.
Authors: Fan Wei Zhang, Qui Ang Zhu, Yuan Fa Ding, Yue Zhang, Da Hai Zhang, Zhong Ping Li
Abstract: Molecular dynamics simulations are performed to research the diffusion behavior of amorphous silica with hydroxyl group. Muliken analysis is employed for the determination of initial charge status of simulated systems with various hydroxyl contents. Modified BKS potentials for the interactions between introduced hydroxyl groups and other atoms, are adopted in the present molecular dynamics simulations. Short-range atomic arrangement and self diffusion coefficients of hydroxyl-doped amorphous silica systems are calculated and hereafter compared with those of pure amorphous silica. The calculation results suggest that the doped hydroxyl groups play an important role for the mobility of atoms within the system, which can be employed to the theoretical interpretation of the oxidation process of the ceramics such as silicon nitride.
Authors: Yuan Fa Ding, Yue Zhang, Fan Wei Zhang, Da Hai Zhang, Zhong Ping Li
Abstract: Vitreous silica, as high temperature resistant material, has not been completely studied with the influence of extreme working conditions due to experimental limitations. In this work, the structure correlations of vitreous silica were investigated by molecular dynamics method at elevated temperatures from 0 K to 4000 K. COMPASS force field was firstly used in simulating vitreous silica. The temperature dependence of volume for vitreous silica was studied and a maximum of volume was found. The calculated density and the thermal expansion coefficient are close to experimental results. The evolutions of structure in thermal history were discussed in detail. The correlations between the average Si-O bond length and the Si-O-Si bond angle is shown in agreement with the studies used other potentials in literatures. It is proved that the COMPASS force field is appropriate for simulating vitreous silica in some extent, especially in depicting the Si-O interaction and the [SiO4] tetrahedron. Finally, the origin of the volume maxima was discussed based on the analysis of the structure.
Authors: Yu Hong Zhao, Yue Zhang, Da Hai Zhang
Abstract: Based on the Potts model, the grain growth of Si3N4 in liquid phase sintering process was simulated by Monte-Carlo method. A two-dimensional, square lattice is used to digitize the microstructure and the components and grain orientation are distributed randomly. The periodical boundary condition is applied. In the initial simulation, the grain growth and coarsening process driven by the reduction in interfacial free energy within a complex system involving a liquid phase were investigated with 32 orientations and different fraction of a liquid phase has been considered. Simulation was carried out with 200×200 lattice. The effects of the liquid amount on the grain growth mechanism and microstructures were discussed.
Authors: Fan Wei Zhang, Song Bang Zhou, Yue Zhang, Da Hai Zhang, Zhong Ping Li
Abstract: Improved genetic algorithm, combined with artificial neural network, is present for the optimal design of 2.5D braided composite. Dispersal simulation data, including maximal stresses and elastics properties, are adopted by artificial neural network for the calculation of strength property. Based on calculation method of strength mentioned above and other calculation models for other mechanical properties, genetic algorithm is employed for the design of structure parameters of 2.5D braided composite, such as wrap fiber density, fill fiber density and interface strength. These structure optimal parameters are finally optimized for practical application.
Authors: Chao Zou, Da Hai Zhang, Yi Li, Wen Jian Weng, Kui Cheng, Chen Lu Song, Gao Ling Zhao, Pi Yi Du, Ge Shen, Jian Xun Wang, Gao Rong Han
Abstract: Aluminum phosphate is one of the best inorganic binders, and the addition of chromium oxide can improve the properties of the binder. In this work, the phase evolutions in chromium phosphate system and aluminum-chromium-phosphate system during heat-treatment were investigated. The initial binder solutions were prepared by dissolving Al(OH)3 and Cr2O3 in aqueous H3PO4 solution. The binder solutions consolidated at 100°C. The as-consolidated products were heated at different temperature. The experimental results showed the phase evolution of the consolidated products as: amorphous phase in 300~800°C, Cr(PO3)3 and Cr4(P2O7)3 in 900~1200°C for chromium phosphate system binder; amorphous phase in 300~1000°C, Cr(PO3)3 and AlPO4 in 1100°C, Cr4(P2O7)3 and AlPO4 in 1200°C for aluminumchromium- phosphate system binder. The addition of chromium oxide demonstrates to strengthen amorphous network, which further improves the thermal stability.
Authors: Zhi Feng Wang, Xian Yan Zhou, Da Hai Zhang
Abstract: The structural use of wood has increased steadily in recent times, including a renewed interest in the use of timber as a bridge material. As the only environment-friendly and resource-saving building material, wood has been gradually uesd for short and medium span bridges in China. In 2014, The domestic largest single-span glued-laminated timber (glulam) deck arch bridge crossing a freeway was completed and put into operation in Zhangjiajie City, central China' Hunan province. In order to know the bearing capacity of superstructures and assess its working conditions, in-site static and dynamic testings has been carried out. Many measures including finite element simulation, field test and comparision between test results and calculated results have been employed to study responses of the bridge under static loads and dynamic loads as well. The researches indicate this glulam footbridge has performed well in service and appear to be cost effective when compared with the cost of installing traditional concrete and steel bridges.
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