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Analysis on cohesive crack opening displacement considering the strain softening effect

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science china(Physics,Mechanics & Astronomy) 2006年第1期49卷 88-101页

作者： WANG Limin1, XU Shilang2.& ZHAO Xiqiang3 1. Mechanics department, Shandong University of technology, Zibo 2.5049,{2. 2. civil engineering department, Dalian University of technology, Dalian 11602.,{2. 3. Mathematics department, Ocean University of{2., Qingdao 2.6071,{2. Mechanics department Shandong University of Technology Zibo 255049 China civil engineering {2. Dalian University of Technology Dalian 116024 China Mathematics department Ocean University of China Qingdao 266071 China

In order to investigate the crack propagation in quasi-brittle materials like rock, ceramic and concrete, Hillerborg and his co-researchers abstracted the fracture process zone in front of a stress free crack in terms of a “fictitious crack zone”. On the fictitious crack zone, cohesive stresses distribute following a given softening relationship of stress vs. crack opening. Based on the polynomial or power series expression of cohesive crack opening displacement, the relationship of the cohesive stress vs. the crack opening displacement is established using elastic theory and integral equation, and some unknown physics variables are obtained using variation approach. The calculation results gained in this paper are close to the experimentally test ones.

关键词： cohesive crack, softening, dissipation work, variation approach.

Entropy Assessment on environmental Influence of Condense Heat in Recovery System in Air-Conditioning Refrigerating Machine

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湖南大学学报（自然科学版） 2009年第S1期36卷 96-101页

作者： TANG Wen-wu1,2.WANG Han-qing1,2.1.school of Energy science and {2.,Central South University,Changsha,Hunan 410083,china 2.school of civil {2.,Hunan University of technology,Zhuzhou,Hunan 412.08,china) school of Energy science and {2. Central South University Changsha 410083 China school of civil {2. Hunan University of Technology Zhuzhou 412008 China

This paper presented an entropy evaluation method for the influences of condense heat recovery system on the *** at the damage of the condense heat to the environment,an entropy of resource loss and an emission entropy from the condense heat recovery system in the air conditioning refrigerating machine were *** the evaluation of the entropies,we developed a new algorithm for the parameter identification,called the composite influence coefficient,based on the Least Squares Support Vector Machine *** simulation,the numerical experiments shows that the Least Squares Support Vector Machine method is one of the powerful methods for the parameter identification to compute the damage entropy of the condense heat,with the largest training error being-0.02.(the relative error being-3.56%),and the biggest test error being 0.015(the relative error being 2.5%).

关键词： air-conditioning refrigerating machine condense heat entropy evaluation LS-SVM

Effect of Coarse Aggregate Size on Relationship between Stress and Crack Opening in Normal and High Strength Concretes

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Journal of Materials science & technology 2005年第5期21卷 85-94页

作者： Jun ZHANG Qian LIU and Lin WANGDepaxtment of civil engineering, Tsinghua University,{2. 100084, china department of civil {2. Tsinghua University Beijing 100084 China

Fine and coarse aggregates play an important role in the fracture of concrete. However, quantitative informationavailable on the effect of the coarse aggregate size on the fracture properties of concrete is still limited. In the presentpaper, the effect of coarse aggregate size (single grade of 5~10, 10~16, 16~2. and 2.~2. mm) on stress-crackopening (σ-ω) relation in normal and high strength concretes (compressive strength of 40 and 80 MPa, respectively)was studied. The investigation was based on three-point bending tests implemented by fictitious crack analysis. Theresult shows that coarse aggregate size and cement matrix strength significantly influence the shape of σ-ω *** a given total aggregate content, in normal strength concrete, smaller size of aggregate leads to a high tensilestrength and a sharp stress drop after the peak stress. The smaller the coarse aggregate, the steeper the σ-ω *** contrast, in high strength concrete, the effect of aggregate size on σ-ω relation almost vanishes. A similar σ-ωrelation is obtained for the concrete except for the case of 2.~2. mm coarse aggregate size. The stress drop afterthe peak stress is more significant for high strength concrete than that for normal strength concrete. Meanwhile, thesmaller the coarse aggregate size, the higher the flexural strength. Fracture energy and characteristic length increasewith increasing coarse aggregate size in both normal and high strength concretes.

关键词： Aggregate size Stress-crack opening relation Fracture energy Bending test

Removal of Volatile Organic Compounds by Adsorption and Photocatalytic Oxydation

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Journal of Wuhan University of technology(Materials science) 2007年第3期22卷 450-452页

作者：许德平黄正宏 Lab of Advanced Materials Department of Materials Science and EngineeringTsinghua University school of Chemical and environmental {2. China University of Mining and Technology

Based on the study of equilibrium adsorption on viscose rayon-based activated carbon fiber （ACF） by gravimetric method, mounting of TiO2.on PAN-based activated carbon cloth （ACC） and their photocatalytic activity as well as adsorption performance for benzene were investigated. The crystallinity of TiO2.and pore structure were characterized by XRD and N2.adsorption. The results show that crystallinity of TiO2.and pore structure could be postulated by heat treatment condition. Both crystallinity of TiO2.and pore structure of hybrid have effects on photocatalytic performance of TiO2.mounted ACC. It would be more attractive and prospective for the combination of TiO2.photocatalytic activity and adsorption ability of porous materials.

关键词： volatile organic compounds activated carbon cloth TiO2

Damage and progressive failure of concrete structures using non-local peridynamic modeling

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science china(Technological sciences) 2011年第3期54卷 591-596页

作者： HUANG Dan1,2. ZHANG Qing1,2.& QIAO PiZhong1,3 1 State Key Laboratory of Hydrology-Water Resources and Hydraulic engineering, Hohai University, Nanjing 2.0098, china 2.{2. of engineering Mechanics, Hohai University, Nanjing 2.0098, china 3 {2. of civil and environmental engineering, Washington State University, Pullman, WA 99164-2.10, USA 1. State Key Laboratory of Hydrology-Water Resources and Hydraulic engineering Hohai University Nanjing 210098 China2. Department of Engineering Mechanics Hohai University Nanjing 210098 China3. Department of Civil and Environmental Engineering Washington State University Pullman WA 99164-2910 USA

Peridynamics (PD), a recently developed theory of solid mechanics, which employs a non-local model of force interaction and makes use of integral formulation rather than the spatial partial differential equations used in the classical continuum mechanics theory, has shown effectiveness and promise in solving discontinuous problems at both macro and micro scales. In this paper, the peridynamics theory is used to analyze damage and progressive failure of concrete structures. A non-local peridynamic model for a rectangular concrete plate is developed, and a central pairwise force function is introduced to describe the interior interactions between particles within some definite distance. Damage initiation, evolution and crack propagation in the concrete model subject to in-plane uni-axial tension, in-plane uni-axial compression and out-of-plane impact load are investigated respectively. The numerical results show that discontinuities appear and grow spontaneously as part of the solution to the peridynamic equations of motion, and no special failure criteria or re-meshing techniques are required, which proves the potential of peridynamic modeling as a promising technique for analyzing the progressive failure of concrete materials and structures.

关键词： concrete damage progressive failure peridynamic model discontinuities

Expansive Behaviors of Self-stressing Concrete under Different Restraining Conditions

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Journal of Wuhan University of technology(Materials science) 2011年第4期26卷 780-785页

作者：常旭 College of civil engineering Henan Polytechnic University

The expansive behaviors of the expensive concrete under different restraining conditions were systemically studied. The experimental results indicate that expansive deformation obviously increases before 10 days and tends to be constant after 2. days regardless of the restraining conditions. The mixture ratio of expansive cement and restraining conditions are the main factors affecting expansive deformation. Self-stress can be obtained when the expansive deformation is restrained. The higher self-stress could be obtained when the expensive concrete is restrained by steel tube. For specimens under steel tube restraining, the wall thickness and the length of the steel tube have important influence on self-stress. Both the radial self-stress and axial self-stress in concrete core increase when wall thickness or length of the steel tube increases.

关键词： self-stress expansive concrete restraining condition

Vanadium recovery from clay vanadium mineral using an acid leaching method

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Rare Metals 2008年第2期27卷 116-120页

作者： LI Haoran FENG Yali LIANG Jianglong LUO Xiaobing DU Zhuwei State Key Laboratory of Biochemical engineering Institute of Process Engineering Chinese Academy of Sciences Beijing 100080 China civil and environmental {2. school University of Science and Technology Beijing Beijing 100083 China

A technique including direct acid leaching, vanadium precipitation with alkaline, sodium hydroxide releaching, impurity removing by adjusting pH value, precipitation vanadium with ammonium chloride, and vanadium pentoxide by roasting steps was proposed according to the characteristic of Xichuan clay vanadium mineral. The factors influencing leaching vanadium such as temperature and the concentration of sulfuric acid were investigated and optimized. The experimental results indicate that the extract ratios of V2.5 can reach 94% and 92. at a sodium chlorate ratio of 3% and a manganese dioxide ratio of 3%, respectivdy. A completely chemical precipitation method was adopted to decontaminate and enrich the vanadium in the acid leaching solution. The X-ray diffraction （XRD） pattern and the purity analysis of vanadium pentoxide indicate that the purity of final vanadium pentoxide can reach 99% and meet the standard specifications. The total recovery can reach about 75%. The technique has the characteristics of simplicity, less investment, and more environment safety as compared with the traditional salt roasting method.

关键词： clay vanadium mineral vanadium extraction acid leaching vanadium pentoxide

Coupling analysis of unsteady seepage and stress fields in discrete fractures network of rock mass in dam foundation

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science china(Technological sciences) 2011年第S1期54卷 133-139页

作者： CHAI JunRui 1,2.& XU WeiSheng 2.1 College of Hydraulic and environmental engineering,{2. Three Gorges University,Yichang 443002.{2. 2.College of Hydropower engineering,Xi’an University of technology,Xi’an 710048,{2. 1. College of Hydraulic and environmental engineering China Three Gorges University Yichang 443002 China2. College of Hydropower Engineering Xi’an University of Technology Xi’an 710048 China

The drag force of water flow through single fracture and the coupling characteristics of seepage and stress in single fracture surface are analyzed,and a three dimensional model of coupled unsteady seepage and stress fields is *** model is used to the analysis of foundation rock mass of a high *** the coupling effects are considered,the changes of boundary heads have less influence on the inner head of rock mass,and the strong permeability of main fractures *** the coupling effects are not considered,the fractures distribution affects the inner head more *** the upstream water head declines,the inner head of dam foundation slightly declines and the hydraulic gradient distribution becomes smoother.A bigger upstream water level declining velocity has a stronger lag effect,meanwhile the values of stress components change more *** the upstream water level declining velocity directly affects the stability of rock mass in dam foundation and we should take into account the above factors to make sure the safety of the dam during reservoir level fluctuation period.

关键词： hydraulic engineering unsteady seepage stress coupling fractures network rock mass

Electrical Measurement to Assess Hydration Process and the Porosity Formation

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Journal of Wuhan University of technology(Materials science) 2008年第5期23卷 761-766页

作者：魏小胜 department of civil {2. Huazhong University of Science and Technology

The change of electrical resistivity with time at early ages was used to investigate the hydration process and the porosity development. Porosity reduction process of cement-based materials hydration was developed by a proposed method. The porosity reduction is fast at the setting period. The results find that the pore discontinuity occurs faster at lower water/cement ratios than at higher water/cement ratios which is similar to the results of the Percolation method.

关键词： electrical resistivity hydration setting time percolation