Papers by Author: Zhen Qing Wang

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Authors: Chun Yu Zhang, Zhen Qing Wang, Mu Qiao
Abstract: The system reliability of prestressed space grid structures were using as control parameters. Branch-bound method was used to determine main failure modes. The reliability of system was calculated by PNET method. Improved genetic algorithm was used in the minimum weight optimum design of the structure system under reliability constraint. Using this method, the complex sensitivity analysis of structural systems could be avoided and made optimum design of the structure system easy. The result of an example showed that the effectiveness of the method.
Authors: Qing Hua Meng, Wen Yan Liang, Zhen Qing Wang
Abstract: The stress and strain field near the tip of Mode I growing crack in materials under creep conditions is examined. The case of the effective stress equal to zero is considered. The asymptotic equations for the crack of the crack tip field are derived and solved numerically. It is concluded that the rates of stress and strain posses the rδ-1 singularity near the tip crack, and the stresses remain finite at the crack tip.
Authors: Hong Shuai Lei, Zhen Qing Wang, Bo Zhou, Yu Long Wang
Abstract: Shape Memory Alloy (SMA) is widely used and plays an important role in various engineering fields due to its special characteristics of shape memory effect and super-elasticity. In this paper the phase transformation behavior and thermo-mechanics behavior of 50.0at%Ni-Ti SMA are investigated though differential scanning colorimeter (DSC) and tensional tests respectively. Optical micrographs show the transformation of austenite and twinned martensite. The comparing numerical calculation result with tensional test result shows the new macro-mechanical constitutive equation can express the thermo-mechanical behavior of SMA effectively.
Authors: Zhen Qing Wang, Zhi Cheng Xue, Mu Qiao
Abstract: For the mechanical properties of reinforced concrete under high temperature with large deterioration, the reliability of reinforced concrete beams have been largely discounted. A calculation of fire resistance based on failure probability is given by this paper. Reinforced concrete beam is usually working with cracks. Since each section with cracks has possibility of destruction, the reliability of the beam is calculated by the minimum value of n crack-sections’ resistance. The plastic zone resistance of concrete under high temperature is considered in this paper. A simple and feasible time-variant model of the resistance of reinforced concrete beams under fire and a reliability index analysis method of reinforced concrete beams under fire has been given. The action of ISO834 temperature rising curve on the reliability index of different specifications of concrete beams at different time is analyzed. The action of main parameters on the reliability index changes with time is shown. The fire resistance considers the failure probability is given. The results show that increase the reinforcement ratio and concrete cover thickness appropriately are effective measures to improve the fire resistance limit of reinforced concrete beams.
Authors: Jia Lei Li, Bin Jia, Zhen Qing Wang, Bao Jun Pang
Abstract: An elastic-viscoplastic constitutive mode was adopted to analyze asymptotically the tip field of a mode I quasi-statically propagating crack in rate-sensitive materials under plane stress condition. Under the assumption that the viscosity coefficient is a power law function of the rate of effective plastic strain, it was obtained through dimension match that the crack tip field possesses power law singularity. And the singularity exponent is uniquely determined by the power law exponent in the supposed viscosity coefficient. The elasticity, plasticity and viscosity of material at crack-tip only can be matched reasonably under linear-hardening condition. Variations of crack tip field characters according to each material parameter were discussed by means of numerical computation. The stress intensity is dominated by the material viscosity whereas the hardening coefficient has less significant influence on tip field. Furthermore, the solution can be transformed to the elastic-nonlinear-viscous one of Hui and Riedel if the limit case of zero hardening coefficient is considered.
Authors: Fang Liu, Zhen Qing Wang, Wen Yan Liang, Yong Wei Qu
Abstract: Based on Zwick/Roell,this paper had carried on flexural experiments of epoxy resin filled with nano-silica particles, obtaining related mechanical properties.Microstructures of nanocomposites were analyzed by scanning electron microscopy (SEM) in the meanwhile. The flexural experiments revealed that nano- silica particles strengthened epoxy resin very well, and flexural modulus of modified matrices rised due to rigid silica particles, compared with pure epoxy matrices. Flexural strengths of epoxies modified by silica nanoparticles improved significantly.
Authors: Zhen Qing Wang, Bing Liu, Da Lei Zhu, Mu Qiao
Abstract: Steel and concrete are poured together with a certain way which can be regarded as a fiber reinforced composite material. For this composite material, the issues of bond and pull-out are very important. The bond property of reinforced concrete at normal temperature is different from the property at elevated temperature. The exposure of reinforced concrete structural elements to high temperatures during an aggressive fire leads to significant losses in its structural capacity due to the reduction in the strength of the concrete, possible plastic deformation of embedded steel and most importantly loss of bond between reinforcing steel and concrete. This paper aims to investigate the influence of high temperature to the bond slip of reinforced concrete. The bond behavior between reinforced concrete and reinforcing steel bars was evaluated under elevated temperatures. Based on the energy principle, the debonding criterion of the steel bars and concrete at a high temperature is derived. It was concluded that the bond slip should be included in order to reflect the unloading of the concrete surrounding the reinforcing steel exposed to fire temperature.
Authors: Yong Jun Wang, Zhen Qing Wang, Hong Qing Lv, Yu Long Wang
Abstract: In order to investigate the performance of shape memory alloy wire, two types of alloy wire were studied. The results showed that the phase transition temperature of the superelastic wire were: Ms and Mf were 21.18 °C and 7.08 °C; As and Af were 12.32 °C and 25.13 °C. The phase transition temperature of memory effect alloy wire were that Ms =- 11.85 °C, Mf =- 29.37 °C, As = 36.77 °C, Af = 43.35 °C. By the tensile test of the SMA wire, the stress - strain curves of the two kinds of alloy wire were obtained.
Authors: Bao Lai Wang, Zhen Qing Wang, Guo Dong Fang, Jun Liang, Li Min Zhou
Abstract: Based on changing the braid angle and geometrical sizes, the compressive experiment of 3D braided four-directional Carbon/Epoxy braided composites is researched. It is found that failure of the braided composites exhibits compressive and shear failure mode. The failure crack propagates mainly in one or two 45º shear direction. Epoxy matrix among braid yarns of the braided composites is squeezed out to form epoxy band. The stress-strain relations of the braided composites with 45º and 30º braid angles all appear nonlinear apparently. Meanwhile the correlation of failure modes and constitutive relation with geometrical sizes of the braided composites is obtained. The compressive stress-strain relations of the braided composites are not great affected by the geometrical sizes. The compressive strengths with great discrete behaviors do not have obvious rules with height of the braided composites.
Authors: Zhen Qing Wang, Song Zhou, Jian Sheng Zhou, Xiao Di Wu
Abstract: In this paper, the influence of geometrical parameters on failure load of bolted single-lap composite joint was investigated. The composite laminate was manufactured from HTA/6376, a high-strength carbon fiber–epoxy material currently used in primary structures in the European aircraft industry. Two geometrical parameters which were plate width-to-hole diameter ratio (W/D), and the edge-to-hole diameter ratio (E/D) were analyzed. To avoid modeling each ply of the laminates discretely, the laminates were modeled using equivalent linear elastic properties. the failure analysis was modeled by Extend Finite Element Method (XFEM) in ABAQUS. Maximum principal stress criterion (Maxps) was used to determine the failure load.
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