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Research on nonlinear constitutive relationship of permanent deformation in asphalt pavements

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Science China(Physics,Mechanics & Astronomy) 2006年第6期49卷 671-682页

作者： PENG Miaojuan1 & XU Zhihong2.1. department of civil {2.,Shanghai university,Shanghai 2.0072.China 2. School of Transportation {2.,Tongji university,Shanghai 2.0092.China 1. department of civil {2. Shanghai University Shanghai 200072 China 2. School of Transportation engineering Tongji University Shanghai 200092 China

To predict correctly the rut depths in asphalt pavements,a new nonlinear viscoelastic-elastoplastic constitutive model of permanent deformation in asphalt pave-ments is presented. The model combines a generalized Maxwell model with an elasto-plastic one. Then from the creep theory,the linear and nonlinear constitutive equations of the generalized Maxwell model are obtained. From the nonlinear finite element method for the rutting of the asphalt pavement,the rut depths of 4 asphalt-aggregate mixtures are obtained. And the results are compared with the ones from the finite element method by SHRP and the experiments by SWK/UN. The results in this paper are better than the ones by SHRP,and agree with the ones of the experiment by SWK/UN. This shows that the nonlinear viscoelastic-elastoplastic constitutive model,which is presented in this paper for the rutting of the asphalt pavement,is effective. The properties,such as nonlinear elastic-ity,plasticity,viscoelasticity and nonlinear viscoelasticity,which affect the rutting of an asphalt pavement,can be shown in the model. And the characteristics of the permanent deformation of the asphalt pavement can be presented entirely in the model.

关键词： asphalt pavement,permanent deformation,nonlinear viscoelastic-elastoplastic constitutive relationship,generalized Maxwell model,creep compliance.

Comment on:Recurrence after spontaneous separation of epiretinal membrane in a young woman:a case report

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International Journal of Ophthalmology(English edition) 2024年第4期17卷 783-784页

作者： Yusuke Kameda Yutaka Kaneko Karin Ishinabe Nichika fukuoka Yotsuya-sanchome Ekimae Eye Clinic Tokyo 160-0004Japan department of Ophthalmology and Visual Sciences Yamagata University Faculty of MedicineYamagata 990-9585Japan

Dear Editor,Herein,we provide a commentary on the recently published article by Zeng QZ and Yu WZ[1].This case report provides interesting novel insights into the recurrence of epiretinal membrane(ERM)following self-separation in a young *** addition to the study,we have been investigating spontaneous ERM release for many years and have recently published a related paper[2..

关键词： separation young release

PRECIPITATION BEHAVIOUR AND HARDENING OFB2.ORDERED Ni(Al, Ta)

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Acta Metallurgica Sinica(English Letters) 1997年第2期10卷 99-104页

作者： W.H. Tian and M. Nemoto2.department of Materials Physics, university of Science and Technology Beijing, Beijing 100083, China)(department of Materials Science and engineering, Faculty of engineering, kyushu university, 812.fukuoka, Japan) Univ of Science and Technology Beijing Beijing China

Precipitation of Ni2.l in supersaturated NiAl containing Ta and corresponding hardening have been investigated by hardness measurements and by transmission electron microscope observations. Selected area electron diffraction, high resolution electron microscopy and energy dispersive X-ray spectrometer analysis have shown that the Ni2.l with a hexagonal structure precipitates coherently in the B2.NiAl matrix. Ni2.l is an ordered phase with a. unit cell parameter, aNi2.ll=aNiAl and CNi2.l= aNiAl. The orientation relationship between the Ni2.l precipitate and the B2.NiAl matrix is (0001)Ni2.l (111)NiAl and [112.]Ni2.l[110]NiAl. NiAlhardens appreciably by the precipitation of Ni2.l phase.

关键词： intermetallic compound precipitation hardening TEM HREM,EDS

Boundary element-free method for elastodynamics

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Science China(Physics,Mechanics & Astronomy) 2005年第6期48卷 641-657页

作者： CHENG Yumin1 & PENG Miaojuan2.1. Shanghai Institute of Applied Mathematics and Mechanics, Shanghai university, Shanghai 2.0072. China 2. department of civil engineering, Shanghai university, Shanghai 2.0072. China 1. Shanghai Institute of Applied Mathematics and Mechanics Shanghai University 200072 Shanghai China 2. department of civil engineering Shanghai University 200072 Shanghai China

The moving least-square approximation is discussed first. Sometimes the method can form an ill-conditioned equation system, and thus the solution cannot be obtained correctly. A Hilbert space is presented on which an orthogonal function system mixed a weight function is defined. Next the improved moving least-square approximation is discussed in detail. The improved method has higher computational efficiency and precision than the old method, and cannot form an ill-conditioned equation system. A boundary element-free method (BEFM) for elastodynamics problems is presented by combining the boundary integral equation method for elastodynamics and the improved moving least-square approximation. The boundary element-free method is a meshless method of boundary integral equation and is a direct numerical method compared with others, in which the basic unknowns are the real solutions of the nodal variables and the boundary conditions can be applied easily. The boundary element-free method has a higher computational efficiency and precision. In addition, the numerical procedure of the boundary element-free method for elastodynamics problems is presented in this paper. Finally, some numerical examples are given.

关键词： moving least-square approximation, improved moving least-square approximation, elastodynamics, boundary integral equation, meshless method, boundary element-free method, Fourier eigen transform.

Electro-mechanical response of functionally graded beams with imperfectly integrated surface piezoelectric layers

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Science China(Physics,Mechanics & Astronomy) 2006年第5期49卷 513-525页

作者： YAN Wei1 & CHEN Weiqiu1,2.1. department of civil {2., Zhejiang university, Hangzhou 31002., China 2. State Key Lab of CAD & CG, Zhejiang university, Hangzhou 31002., China 1. department of civil {2. Zhejiang University Hangzhou 310027 China 2. State Key Lab of CAD & CG Zhejiang University Hangzhou 310027 China

The time-dependent behavior of a simply-supported functionally graded beam bonded with piezoelectric sensors and actuators is studied using the state-space method. The creep behavior of bonding adhesives between piezoelectric layers and beam is characterized by a Kelvin-Voigt viscoelastic model, which is practical in a high temperature circumstance. Both the host elastic functionally graded beam and the piezoelectric layers are orthotropic and in a state of plane stress, with the former being inhomogeneous along the thickness direction. A laminate model is employed to approximate the host beam. Moreover, the coupling effect between the elastic deformation and electric field in piezoelectric layers is considered. Results indicate that the viscoelastic property of interfacial adhesives has a significant effect on the function of bonded actuators and sensors with time elapsing.

关键词： functionally graded beam piezoelectric layers Kelvin-Voigt model state-space method

Factors Affecting the Relation of Fracture Toughness V_(GC) with Critical Void Growth Ratio R_C/R_O

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Journal of Materials Science & Technology 1998年第6期14卷 574-576页

作者： Li ZHOU(department of civil {2., Wuyi university,Jiangmen 52.02., China) department of civil {2. Wuyi University Jiangmen 529020 China

The relationship between fracture toughness VGC and critical void growth RC/RO was studied for ten kinds of Steel. The macroscopic fracture toughness VGC was determined by using notched tensile specimens. and the microscopic parameters of critical void growth ratio RC/RO were quantitatively measured under SEM. Then, the coefhcient C in the relation VGC = C In(RC/RO) proposed in author's past work was specifically explored. The correlation of C with tensile proderty parameter φ=σyδ/(Eφn) was presented for the Steel investigated, and the effects of low temperature on C were also discussed. Results show that the coefficient C is linearly related to the parameter and insensitive to low temperature.

关键词： GC with Critical Void Growth Ratio R_C/R_O Factors Affecting the Relation of Fracture Toughness V

A three-dimensional prediction system for water quality polluction in coastal waters

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Journal of Environmental Sciences 2000年第4期12卷 430-438页

作者： SHEN Yong\|ming\+1, ZHENG Yong\|hong\+1, Toshimitsu KOMATSU\+2.(1. State Key Laboratory of Coastal and Offshore engineering, Dalian university of Technology, Dalian 11602., China {2., kyushu university, fukuoka 812.85 State Key Laboratory of Coastal and Offshore engineering Dalian University of Technology Dalian 116023 China department of civil {2. Kynshu Univemity Fukuoka 812-8581 Japan

The hydrodynamics and water quality in Hakata Bay, Japan are strongly affected by the seasonal variations in both the gravitational circulation and the stratification in the bay. The three\|dimensional hydrodynamics and water quality model has been developed to simulate the long\|term transport and fate of pollutants in the system. The model is unique in that it completely integrates the refined modelling of the hydrodynamics, biochemical reactions and the ecosystem in the coastal waters. It is a 3\|dimensional segmented model which is capable of resolving mean daily variations in all the parameters relevant to pollution control. It predicts daily fluctuations in the oxygen content at different depths in water throughout the year. It takes into account transport and settling of pollutant particles. It predicts light penetration from computed turbidity variations. It includes interactions between the ecosystem and water quality through nutrient cycling and photosynthesis. The model has been calibrated well against the data set of historical water quality observations in Hakata Bay.

关键词： coastal waters water quality ecosystem turbulence model numerical modelling

Experimental study on bed-load sediment transport under irregular wave and current combined flow

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Acta Oceanologica Sinica 2001年第2期20卷 271-280页

作者： Wu Yongsheng,Qin Chongren (1. department of Hydraulic engineering, Tsinghua {2., Beijing 100084, China 2. School of civil engineering, Tianjin {2., Tianjin 300072. China) department of Hydraulic engineering Tsinghua University Beijing 100084 China

Using an irregularly oscillating tray and flume, a series of experiments are completed to evaluate bed-load sediment transport rate under irregular wave -current coexistent field. Testing conditions include three interaction angles 0', 45', 90' and two kinds of median sizes (0.38 and 1.10 mm). The results of transport rate show that the net sediment transport rate can be expressed approximately as the function of the maximum bottom shear stress of waves, mean shear stress of current and the grain size.

关键词： Irregular wave-current bed-load transport rate

Rock matrix-fractured media model for heterogeneous and fractured coal bed

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中国有色金属学会会刊：英文版 2011年第S3期21卷 621-625页

作者： ZHANG Chun-hui1, YU Guang-ming2. ZHANG Chun1 1. School of civil engineering, Hebei {2. of Science and Technology, Shijiazhuang 050018, China 2. School of civil engineering, Qingdao Technological {2., Qingdao 2.6033, China [a] School of civil engineering Hebei University of Science and Technology Shijiazhuang 050018 China [b] School of civil engineering Qingdao Technological University Qingdao 266033 China

Coal was considered rock matrix-fractured media composed of rock matrix and fractures, and the rock matrix-fractured media model for heterogeneous and fractured coal bed was presented. In this model the rock matrix is heterogeneous, and the mechanical parameters such as elastic modulus and strength follow Weibull distribution. Fractures in coal bed were generated with the discrete fracture network method, and the properties of fractures were simulated with Desai element. Then the virtual generating system (VGS) of natural heterogeneous and fractured coal bed was developed in Matlab 6.0. The coupled model of gas flow and deformation process based on the rock matrix-fractured media model method and VGS for heterogeneous and fractured coal bed was presented, and the numerical code was developed in Matlab 6.0. The gas flow process in the heterogeneous and fractured coal bed was simulated in a numerical case. The main conclusions are: 1) The natural heterogeneous and fractured coal bed could be simulated by the rock matrix-fractured media model and VGS; 2. The fractures connected with the well have much more effects on gas flow than those non-connected.

关键词： heterogeneity fractures rock matrix-fractured media