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A MODEL FOR CONCRETE DURABILITY DEGRADATION IN FREEZE-THAWING CYCLES

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Acta Mechanica Solida Sinica 2003年第4期16卷 353-358页

作者： Wei Jtm Wu Xinghao Zhao Xiaolong (sch.ol of civ.l eng.neering and mechanics,Huazhong University of Science and Technology,Wuhan 430074,China) sch. of civ. eng. and mechanics Huazhong Univ. of Sci./Technology Wuhan 430074 China

Up to now,how to control the durability of concrete structures is still a pending research topic in civ.l *** to the fact that concrete durability can be affected by many non-mechanical factors,it is very difficult to research durability only based on mechanics. However,the phenomenon of failure caused by non-mechanical factors is similar to that caused by *** frost durability reflects the comprehensive durability of concrete in a certain sense, the specific failure process is analyzed and a damage model is introduced,which can describe the durability degradation process of concrete in the whole freeze-thawing cycle.

关键词： concrete durability damage frost durability

A SEMI-ANALYTICAL AND SEMI-NUMERICAL METHOD FOR SOLVING 2-D SOUND-STRUCTURE INTERACTION PROBLEMS

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Acta Mechanica Solida Sinica 2003年第2期16卷 116-126页

作者： Xiang Yu Huang Yuying (College of civ.l eng.neering and mechanics,Huazhong University of Science and Technology,Wuhan 430074,China) Coll. of civ. eng. and mechanics Huazhong Univ. of Sci./Technology Wuhan 430074 China

Based on the transfer matrix method and the virtual source simulation technique, this paper proposes a novel semi-analytical and semi-numerical method for solving 2-D sound- structure interaction problems under a harmonic *** any integration segment, as long as its leng.h is small enough,along the circumferential curvilinear coordinate,the non- homogeneous matrix differential equation of an elastic ring of complex geometrical shape can be rewritten in terms of the homogeneous one by the method of extended homogeneous capacity proposed in this *** the exterior fluid domain,the multi-circular virtual source simulation technique is *** source density distributed on each virtual circular curve may be ex- panded as the Fourier's *** with the inverse fast Fourier transformation,a higher accuracy and efficiency method for solving 2-D exterior Helmholtz's problems is presented in this *** the aspect of solution to the coupling equations,the state vectors of elastic ring induced by the given harmonic excitation and generalized forces of coefficients of the Fourier series can be obtained respectively by using a high precision integration sch.me combined with the method of extended homogeneous capacity put forward in this *** to the superposition princi- ple and compatibility conditions at the interface between the elastic ring and fluid,the algebraic equation of system can be directly constructed by using the least square *** of acoustic radiation from two typical fluid-loaded elastic rings under a harmonic concentrated force are *** results show that the method proposed is more efficient than the mixed FE-BE method in common use.

关键词： sound-structure interaction acoustic radiatlon multi-circular virtual source simulation technique transfer matrix method inverse fast Fourier transformation semi-analytical and semi-numerical method

A VIRTUAL MESH METHOD FOR THE OPTIMIZED DESIGN OF COMPLEX STRUCTURES

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Acta Mechanica Solida Sinica 2003年第3期16卷 220-230页

作者： Du Taisheng.Huang Rongjie Song Tianxia Chen Chuanyao (College of civ.l eng.neering and mechanics,Huazhong University of Science and Technology,Wuhan 430074,China) Coll. of civ. eng. and mechanics Huazhong Univ. of Sci./Technology Wuhan 430074 China

Concepts for a virtual 3D space and a hyper-sphere are proposed and the formulae for determining the computable nodes of the mesh are *** a new optimization design method('Virtual Mesh Method'or V.M.M)is *** examples are given,showing that the method proposed is especially suitable for the optimized design of complex structures,and that the global approximate optimal solution can be searched with remarkably reduced computational work.

关键词： virtual 3D space computable nodes n-D hyper-sphere optimization design virtual mesh method

Effects of volume fraction condition on thermodynamic restrictions in mixture theory

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Science China Mathematics 2002年第5期45卷 640-647页

作者：牛永红苗天德 Department of mechanics Sch. of Phys. Science and Technology Lanzhou University Lanzhou 730000 China Stt. Key Lab. of Frozen Soil eng. Cold Arid Regions Environ. Eng. R. Chinese Academy of Sciences Lanzhou 730000 China

Volume fraction condition is a true constraint that must be taken into consideration in deducing the thermodynamic restrictions of mixture theory applying the axiom of dissipation. For a process to be admissible, the constraints imposed by the volume fraction condition include not only the equation obtained by taking its material derivative with respect to the motion of a given phase, but also those by taking its spatial gradient. The thermodynamic restrictions are deduced under the complete constraints, the results obtained are consistent for the mixtures with or without a compressible phase,and in which the free energy of each phase depends on the densities of all phases.

关键词： mixture theory, volume fraction condition, thermodynamic restrictions.

STUDY ON THE TENSILE FATIGUE DAMAGE OF QUASI-ISOTROPIC COMPOSITE LAMINATES

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Acta Metallurgica Sinica(eng.ish Letters) 2003年第1期16卷 1-7页

作者： I.G.Kim I.S.Kim O.S.Kim YaragarraK.D.V.Prasad Dept. of Aerosp. eng. Chosun Univ. Gwangju 501-759 South Korea Dept. of Mech. eng. Mokpo Natl. Univ. Chonam 534-729 South Korea Dept. of Mech. eng. Yosu Natl. Univ. Chonnam 550-749 South Korea sch. of Mech. and Med. eng. Queensland Univ. of Technol. Brisbane QLD 4001 Australia

Quasi-isotropic laminates have isotropic elastic properties in all in-plane directions. Therefore, this kind of laminate is widely used for structural elements. The simplest stacking sequence of quasi-isotropic laminates is [0/-60/60]s. When the direction of applied axial load to [0/-60/60]S laminate is inclined at a 30-degree angle, we have the other quasi-isotropic laminate [30/-30/90]s under axial load. The failure mechanisms of these two laminates are, however, entirely different from each other because these two laminates have different distribution of the interlaminar stresses. It was confirmed by tensile fatigue tests that the [0/-60/60]s laminate does not show any visible fatigue damage, but the [30/-30/90]s laminate develops edge-delamination during cyclic loading. The analytical results were in good agreement with the experimental results.

关键词： composite material delamination fatigue fracture mechanics interlaminar stress

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地下隧道在临近隧道爆破作用下的安全评估

岩石力学与工程学报 2004年第z2期23卷 4715-4720页

作者：马国伟赵坚张喜虎 sch. of civ.l and Environ. eng. Nanyang Technol. Univ. Singapore 639798 Singapore Dept. of civ.l and Resource eng. Univ. of Western Australia Crawley WA 6009 Australia Geotech. and Structural eng. Ctr. Shandong Univ. Jinan 250061 China

A numerical simulation method is proposed to evaluate the underground tunnel safety against explosion in adjacent tunnels. The dynamic constitutive relation used for rock material in the present study consists of a continuum damage model with the damage scalar depending on an equivalent tensile strain, a modified piecewise linear Drucker-Prager streng.h model allowing for the material streng.h degradation with damage, and a modified linear equation of state. The numerical model is calibrated by simulation of independent field explosion tests. Parametric study regarding the effect of the adjacent tunnel distance on the dynamic responses of underground tunnel is carried out. Failure zone around the explosion tunnel, and stress, strain and velocity on the adjacent tunnel wall are calculated. Safe separation distance between the adjacent tunnels is predicted and compared with empirical result.

关键词： AUTODYN Numerical simulation Rock damage Safe separation distance Underground explosion

地下爆炸作用下节理岩体力学响应的离散元法模拟

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岩石力学与工程学报 2004年第z2期23卷 4936-4940页

作者：焦玉勇赵坚 sch. of civ.l and Environ. eng. Nanyang Technol. Univ. Singapore 639798 Singapore Inst. of Rock and Soil Mech. Chinese Acad. of Sci. Wuhan 430071 China Coll. of Arch. and civ.l eng. China Univ. of Mining and Technol. Xuzhou 221008 China

To verify the capability of discrete element method (DEM) in modeling the dynamic response of rock masses to blasting loads, two underground explosion tests are numerically investigated. Results show that rock joints can significantly affect the transmission and the attenuation of shock waves, and can therefore influence the stability of the adjacent underground structures. Rock joints act as a kind of filters through which only low-frequency components of the shock waves are allowed to pass, and the high-frequency components of the shock waves do no harm to far-field tunnels if a predominant joint set exists in between. The spacing of joint set can also remarkably affect the propagation process. It indicates that as a discontinuum-based numerical approach, DEM is good at simulating the propagation and attenuation of blasting wave in jointed rock masses, and in modeling the stability of underground structures subjected to blasting loads.

关键词： DEM Frequency Numerical simulation Shock wave

Transient Exergy Analysis of the Condenser and Evaporator of an Air Source Heat Pump Water Heater

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Journal of mechanics eng.neering and Automation 2016年第7期6卷 339-347页

作者： Mehmet Mete Ozturk L. Berrin Erbay Transportation Vocational sch. Anadolu University Eskisehir Turkey sch.ol of eng.and Arch. Eskt'sehir Osmangazi University 26480 Ban Meselik Eskisehir Turkey

In this study the performance of an ASHPWH （air source heat pump water heater） is assessed from exergy point of view in component wise. In order to investigate the work potential of energy, the destruction on the exergy is analyzed and results are summarized for the components individually. The exergy destruction of the system is studied by considering real paths of the pressure and temperature data which are collected during the experiments of the ASHPWH under varying environmental conditions. In the following step, the evolution of the exergy destruction of the system is calculated by a code which is compiled on MATLAB along these temperature and pressure paths. The obtained results reveal the importance of the transient exergy analysis by providing detailed information about exergy destruction of the system such as where it drives up and reaches up to its max and where it drops down and evolves on a smooth path.

关键词： Transient exergy analysis heat pump condenser evaporator.