Papers by Author: Zhen Qing Wang

Abstract: In this paper, the size effect of copper, aluminum and silver nanoindentation has been studied by adopting the new multiscale method. According to the analysis and comparison of load-displacement cures for the three materials under the four specimens, the effects of various physical parameters on the dislocation nucleation have been discussed. For different specimen lengths, simulation results show the apparent size effect, especially in the initial elastic deformation stage, the difference of the curve slope is very obvious. Comparing these three kinds of metal materials of the load displacement curve, it can be found that the metal copper thin film and the metal aluminum thin film in the load process, only experience one time reduced the process, but the metallic silver thin film reveals a fluctuation.

Abstract: The reliability of a reinforced concrete beam has been largely discounted when it under the action of fire. For a more accurate description of concrete beams’ reliability, the impact of cracks in reinforced concrete beams has been taking into account. Concrete is divided into elastic zone and plastic zone to calculate its strength. A simple and feasible time-variant model of reliability index of reinforced concrete beams under fire has been given. The effect of ISO834 temperature rising curve on the reliability index of concrete beam at different time has been analyzed. The reliability of a reinforced concrete beam under the ISO834 standard heating curve was assessed by first order second moment method.

Abstract: The increasing of equivalent floor live-loads is used to describe the weakening of ultimate carrying capacity of the structure by analyzing variety of the beam’s ultimate moment and ultimate shearing force and the carrying capacity and stability of the column of steel-frame in fire, the formulas of the beam’s ultimate shearing capacity, the carrying capacity and stability of column and the equivalent floor live-loads have been derived based on these. The variety rules of the carrying capacity of beam and column of the steel-frame with different thickness of the protection layers and the equivalent floor live-load have been analyzed in the example, the results showed that different equivalent floor live-load may be used to analyze the infection of fire temperature to the carrying capacity of structure in the computations of steel-frame in fire according to different time and fire temperatures of structure members, the mechanics computations of structure would be predigested and the variety of ultimate carrying capacity of steel-frame also could be estimated.

Abstract: Three kinds of shear buckling parameters of corrugated steel web beam under high temperature of fire in different time are analyzed and the high temperature effect on structural steel property is taken into account, the expressions of local buckling parameter, overall buckling parameter and interactive buckling parameter are proposed and their variation trends with the high temperature change are analyzed, a recommendation is proposed in order to provide more accurate predictions for the load-carrying capability status of corrugated steel web beam under high temperature, the buckling parameters variation should be unbiased estimated above all. Numerical results show that high temperature has obvious effect on the buckling parameter changes of the corrugated web steel beam.

Abstract: Based on the theory and semi-empirical formulas, the surface heating flux of hypersonic flying vehicle under aerodynamic heating is calculated by using reference enthalpy method. On this basis, the thermal response of structure made of ultrahigh temperature ceramics(UHTCs) is simulated by using finite-element method. The results show that thermal stress shock is able to cause material to damage in a very short time

Abstract: The damage assessment of reinforced concrete structure after fire was investigated by the pertinent theory of fuzzy mathematics and a mathematical model was established. With the establishment of the assessment system, the ascertain of the factorial weighting, the numeric quantification of various qualitative factors and quantitative factors and the application of fuzzy assessment , a new assessment system which based on the theory of fuzzy mathematics and was suitable to the damage assessment of reinforced concrete structure after fire was formed. An elaborate introduction on the establishment of the means and process of the assessment model was made, finally a practical example was showed to concretely illustrate the means and process of the assessment system.

Abstract: In the present paper, the mechanical model of dynamic propagation interface crack of the compression-shear mixed mode is proposed by using the elastic-viscoplastic constitutive model. Then the governing equations of propagation crack interface at crack tip are given. The numerical analysis is accomplished for the interface crack of compression-shear mixed mode by introducing a displacement potential function and some boundary conditions at interface crack tip. The distributed regularities of stress-strain fields of interface crack tip are discussed with several special parameters. The numerical results show that the viscosity effect is a main factor of interface propagating at crack-tip field, and the interface crack-tip is a viscoplastic field that is governed by viscosity coefficient、Mach number and singularity exponent.

Abstract: Shape memory alloy (SMA) is a new intelligent material and is used widely in various structures. But the constitutive model of SMA is so complex and particular that it is difficult to calculate by finite element software. In this paper, a special constitutive model of SMA is chose and the constitutive variables are discretized. Through the derivation, it is made possible that the constitutive relation of SMA is put into the UMAT (user-defined material mechanical behavior) subroutine in ABAQUS. So it is available to calculate the structure contained SMA by finite element method.

Abstract: To further study the field of the mixed-mode interface crack tip under compression and shear, we analyze the problem on the quasi-static propagating of the interface crack theoretically and numerically.In this paper,we assumes that the artifical viscosity cofficient is in inverse proportion to power law of the plastic strain rate,and the stress of the interface crack possesses power law singularity. The viscosity of material,the friction touch effection of the crack-tip surface and the load hybrid parameter are considered. The asymptotic solution is established for elastic-viscoplastic field at the mixed-mode propagating crack-tip under comprission and shear.It is shown in numerical results and analysis that for the mixed-mode crack-tip field under compressing and shear is whole plastic without elastic unloaded section;viscosity effection is an important factor when propagating crack-tip field is studied; viscosity coefficient, mach number and singularity exponent are the control factors of singular field at the crack-tip.

Abstract: Ceramic insulating tile is the main insulation material used on space shuttle thermal protection system at present, but this material has low strength, high brittleness and easy to be damaged. So the study of thermodynamic response of damaged rigid ceramic insulating tiles is very important. In this paper the temperature field and thermal stress field of the damaged ceramic insulating tiles under aerodynamic heating are simulated by ABAQUS code. The analyzed results indicate that the sharp degree of the damage shape has minor influence on the temperature field, but is more significant for the maximum thermal stress. Meanwhile the larger loading is, the bigger influence is.