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Wang J.,China Institute of Water Resources and Hydropower Research | Jia B.-H.,Beijing Institute of Technology | Li W.,China Aviation Engine Establishment | Wang R.-L.,CAS Center for Space Science and Applied Research
Beijing Ligong Daxue Xuebao/Transaction of Beijing Institute of Technology

To research the mechanical behavior of concret under dynamic loadings, the mechanical behavior and the failure modes of concrete under quasi-static or dynamic compressive loadings were investigated by a two-dimensional finite element model which was established by a self-developed program. Random distribution of coarse aggregate in concrete was obtained by using this program. In the developed program, concrete was regarded as a two-phase composite material of cement mortar and coarse aggregate. The effectiveness of established finite element model was verified by comparing of numerical predictions with experimental results. Then, the effects of coarse aggregate size distribution and coarse aggregate volume fraction on the mechanical behavior and failure modes of concrete under dynamic loadings were analyzed. The results of this research could provide a basis for the structural optimization and design of concrete. Source

Shi D.,Beihang University | Dong C.,Beihang University | Yang X.,Beihang University | Sun Y.,Beihang University | And 2 more authors.
Materials and Design

Experiments are carried out at elevated temperature to investigate the effect of brazing itself and post-brazing heat treatment on the lifetime of directionally solidified (DS) superalloy. Meanwhile, a new lifetime prediction methodology based on continuum damage mechanics (CDM) is proposed to predict the lifetime of DS superalloy and its brazed joints. After creep and fatigue testing, the fractured specimens are observed by means of Optical Microscope (OM) and Scanning Electron Microscope (SEM) with the Energy Dispersive X-ray Spectrometer (EDXS) to understand their failure mechanisms. The results showed that: (1) under the same test condition, all the brazed joints exhibited a lower creep and fatigue lifetime compared with a typical DS superalloy; (2) the creep and fatigue lifetime of heat treated brazed joint was longer than that of non heat treated one; (3) the developed CDM method can be used to predict the lifetime of all the specimens; (4) all the brazed joints fractured in the brazing seam; and (5) there were many distinctive differences between the failure mechanics of DS superalloy and its brazed joints. © 2012 Elsevier Ltd. Source

Jia Z.-G.,China Aviation Engine Establishment | Wang R.-Q.,Beihang University | Hu D.-Y.,Beihang University | Fan J.,Beihang University | Shen X.-L.,Beihang University
13th International Conference on Fracture 2013, ICF 2013

The multi-field coupled analysis, a higher precision, is an interaction effect among the fluid, the structure strength and the thermal on the turbine design. Considering the coupled effect in the multidisciplinary optimization design (MDO) could further excavate the design potential and improve the optimization precision on the turbine. Thus the paper firstly shows the automatic process of the fluid-solid closely coupled analysis method based on the ALE which would be the foundation of the turbine MDO. The comparison between the analysis result of the couple and the single discipline on the turbine blade proves the transdisciplinary influence each other. Based on kinds of the different precise analysis methods, this paper secondly puts forward the multiple-precision strategy in order to balance the cost and the precision on turbine MDO. This strategy studies the variable complexity method (VCM) which is improved by the two-point scale function and the periodic updating technology and three kinds of precise models including the fluid-solid closely coupled analysis, the single discipline analysis and the approximate equation. The strategy solves the difficulty of disciplinary decoupling and coordination by the collaborative optimization (CO) strategy. Finally, the new strategy could finish the turbine MDO with acceptable performance. Source

Huang Y.,Beihang University | Zhao R.,Beihang University | Li W.,China Aviation Engine Establishment
Journal of Geophysical Research: Atmospheres

A particle superposition model combined with a Monte Carlo ray tracing method, which is used to study the radiative characteristics of large nonspherical particles, is proposed. The goal of the model is to provide a new approach that not only allows the modeling of large irregular particles of arbitrary shape but also possesses a clear and systematic basic structure that is easy to program. A detailed flow chart and algorithm description are provided in the paper. The data characteristics of four types of irregular particles were calculated and analyzed. The comparison showed that this particle superposition model can be used to calculate the radiative properties of large irregular particles with good accuracy, while at the same time remaining general and extendable to many applications, thus providing a new way to study nonspherical particles. Key Points A particle superposition method is proposed Capable to calculate particles of arbitrary shape and inhomogeneous medium Comparisons of data validate the good accuracy of the method ©2013. American Geophysical Union. All Rights Reserved. Source

Sun C.,China Aviation Industry General Aircraft Co. | Ren Y.,Hunan University | Chen F.,China Aviation Engine Establishment | Zou D.,China Aviation Industry General Aircraft Co.
Cailiao Kexue yu Gongyi/Material Science and Technology

To predicate the life of composite structures, the prediction methods of composites fatigue life were reviewed. The residual stiffness model was established and the concept of residual strain was proposed. Using finite element analysis tool Abaqus, a user defined subroutine UMAT was embedded into the general FEA package to realize the life prediction of composite structures. Fatigue properties of the composite material TS800 were studied and some experimental data for engineering applications was obtained. Finally, the life prediction of the composite structures was conducted, which agrees well with the test data. © 2015, Harbin Institute of Technology. All right reserved. Source

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