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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 200072,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.

Model test on sand retaining wall reinforced with denti-strip inclusions

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Science china(Technological Sciences) 2008年第12期51卷 2259-2269页

作者： ZHANG MengXi1 & ZHOU Huai1,2.1 department of civil {2.,shanghai university,shanghai 200072,china 2.shanghai Chengtou City Land(Group) Corporation,shanghai 2.0438,china department of civil {2. Shanghai University Shanghai 200072 China shanghai Chengtou City Land (Group) Corporation Shanghai 200438 China

In conventional reinforced soil structures,the reinforcements are often laid hori-zontally in the *** this paper,a new concept of soil reinforced with denti-strip inclusions was proposed and a series of laboratory model tests were carried out on sand retaining wall reinforced with denti-strip *** the horizontal displacements of the facing,the lateral earth pressures acting on vertical elements were measured.A microscopic measurement was performed to investigate the deformation and progressive failure of the sand within model retaining *** on the image analytical technique,the bearing capability and interaction mechanism of reinforced sand retaining wall were *** model of the initial shear failure and potential failure surface were also put *** the experimental results,it is shown that denti-strip inclusions can increase the bearing capability of retaining wall significantly and restrict the facing displacements efficiently,as compared with conventional horizontal reinforcement.

关键词： denti-strip inclusions reinforced sand retaining wall model test horizontal facing displacements lateral earth pressure on denti-elements failure surface

A study of mechanical behavior of rock-fill materials with reference to particle crushing

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Science china(Technological Sciences) 2007年第z1期50卷 125-135页

作者： HUANG WenXiong1?, REN QingWen1 & SUN DeAn2.1 department of engineering Mechanics, Hohai {2., Nanjing 2.0098, china 2.department of civil engineering, shanghai university, shanghai 200072, china department of engineering Mechanics Hohai University Nanjing 210098 China department of civil {2. Shanghai University Shanghai 200072 China

In rock-fill dams of 2.0 to 300 m high, maximum compressive stress can exceed 6 MPa. At such a high stress level, rock-fill materials may experience particle crushing during shear. The material behavior is highly sophisticated exhibiting pressure and density dependency as well as particle crushing effects. Through scrutinizing the relevant experimental data on rock-fill materials and sands published in the literatures, this paper is focused on understanding basic mechanical characteristics of this sort of materials in the light of constitutive modelling.

关键词： rock-fill materials granular materials compressibility shear dilatancy particle crushing

A complex variable meshless method for fracture problems

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Science china(Physics,Mechanics & Astronomy) 2006年第1期49卷 46-59页

作者： CHENG Yumin1 & LI Jiuhong2.1. shanghai Institute of Applied Mathematics and Mechanics, shanghai university,{2., china 2. department of Building engineering, Xi’an university of Technology, Xi’an 710048, china shanghai Institute of Applied Mathematics Mechanics Shanghai University Shanghai 200072 China department of Building engineering Xi’an University of Technology Xi’an 710048 China

Based on the moving least-square (MLS) approximation, the complex variable moving least-square approximation (CVMLS) is discussed in this paper. The complex variable moving least-square approximation cannot form ill-conditioned equations, and has greater precision and computational efficiency. Using the analytical solution near the tip of a crack, the trial functions in the complex variable moving least-square approxi- mation are extended, and the corresponding approximation function is obtained. And from the minimum potential energy principle, a complex variable meshless method for fracture problems is presented, and the formulae of the complex variable meshless method are obtained. The complex variable meshless method in this paper has greater precision and computational efficiency than the conventional meshless method. Some examples are given.

关键词： moving least-square approximation, complex variable moving least-square approximation, meshless method, complex variable meshless method, fracture.

Virtual multi-dimensional internal bonds model and its application in simulation of rock mass

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Science china(Technological Sciences) 2008年第2期51卷 192-201页

作者： ZHANG ZhenNan1,2.& GE XiuRun3,4 1 department of civil {2.,shanghai university,shanghai 200072,china 2.shanghai Institute of Applied Mathematics and Mechanics,shanghai university,shanghai 200072, china 3 Institute of Geotechnical {2.,shanghai Jiao Tong university,shanghai 2.0030,china 4 Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan 430071,china 1. department of civil {2. Shanghai University Shanghai 200072 China 2. shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 China 3. Institute of Geotechnical engineering Shanghai Jiao Tong University Shanghai 200030 China 4. Institute of Rock and Soil Mechanics Chinese Academy of Sciences Wuhan 430071 China

VMIB (virtual multi-dimensional internal bonds) is a multiscale mechanical model developed from the VIB (virtual internal bond) theory. In VIB theory,the solid mate-rial is considered to consist of random-distributed material particles in microscale. These particles are connected with normal bonds. The macro constitutive relation is derived from the cohesive law between particles. However,in VMIB,the micro particles are connected with both normal and shear bonds. The macro constitutive relation is derived in terms of bond stiffness coefficients. It has been theoretically certified that there exists a corresponding relationship between the two bond stiffness coefficients and the two macro material constants,i.e. the Young’s modulus and Poisson ratio. This corresponding relationship suggests that it should be necessary and sufficient to simultaneously account for the normal and shear interactions between particles. Due to the fact that the fracture criterion is directly incorporated into the constitutive relation,both VIB and VMIB present many advantages in simulating fractures of materials. In the damage model of rock mass,a damage tensor is usually defined to describe the distribution of cracks. The damage value in one direction determines the relative stiffness of rock mass in this direction. In VMIB solid,the relative distribution density of micro bonds in one direction determines the relative macro stiffness of the material in this direction. The effects of the damage value and the relative distribution density of bonds are consistent. To simulate the failure behavior of rock mass with VMIB,the presented paper sets up a quantitative relationship between the damage tensor and the rela-tive distribution density of bonds. Comparison of the theoretical and the experi-mental results shows that VMIB model can represent the effect of distributed cracks on rock mass with this relationship. The presented work provides a founda-tion for further simulating fracture behavior

关键词： VMIB (virtual multi-dimensional internal bonds) rock mass VIB (virtual internal bonds) multi-cracked body numerical simulation

The complex variable reproducing kernel particle method for elasto-plasticity problems

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Science china(Physics,Mechanics & Astronomy) 2010年第5期53卷 954-965页

作者： CHEN Li1 & CHENG YuMin2.1 department of engineering Mechanics,Chang’an {2.,Xi’an 710064,china 2.shanghai Institute of Applied Mathematics and Mechanics,shanghai {2.,shanghai 200072,china 1. department of engineering Mechanics Chang’an University Xi’an 710064 China2. Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 China

On the basis of reproducing kernel particle method(RKPM),using complex variable theory,the complex variable reproducing kernel particle method(CVRKPM) is discussed in this *** advantage of the CVRKPM is that the correction function of a two-dimensional problem is formed with one-dimensional basis function when the shape function is *** the CVRKPM is applied to solve two-dimensional elasto-plasticity *** Galerkin weak form is employed to obtain the discretized system equation,the penalty method is used to apply the essential boundary *** then,the CVRKPM for two-dimensional elasto-plasticity problems is formed,the corresponding formulae are obtained,and the Newton-Raphson method is used in the numerical *** numerical examples are given to show that this method in this paper is effective for elasto-plasticity analysis.

关键词： meshless method reproducing kernel particle method(RKPM) complex variable reproducing kernel particle method(CVRKPM) correction function elasto-plasticity

FREE-SURFACE WAVES AND FAR WAKES GENERATED BY A FLOATING BODY IN A VISCOUS FLUID

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Journal of Hydrodynamics 2003年第4期15卷 10-16页

作者： Lu Dong-qiang department of Mechanical engineering, The {2. of Hong Kong, Hong Kong, china shanghai Institute of Applied Mathematics and Mechanics, shanghai university, shanghai 200072, china department of Mechanical engineering The University of Hong Kong Hong Kong China shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 China

The free-surface waves and the flow field due to a body moving on the surfaceof an incompressible viscous fluid of infinite depth were studied analytically. The floating bodywas modeled as a normal point pressure on the free surface. Based on the Oseen approximation forgoverning equations and the linearity assumption for boundary conditions, the exact solutions inintegral form for the free-surface elevation, the velocities and the pressure were given. Byemploying Lighthill's two-stage scheme, the asymptotic representations in far field for largeReynolds numbers were derived explicitly. The effect of viscosity on the wave profiles was expressedby an exponential decay factor, which removes the singular behavior predicted by the potentialtheory.

关键词： free-surface waves velocity distribution floating body viscosity asymptotic representation light-hill's two-stage scheme

Optimal motion planning of an underactuated spacecraft using wavelet approximate method

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Progress in Natural Science:Materials International 2006年第8期16卷 868-873页

作者： GE Xinsheng, CHEN Liqun and LIU Yanzhu (Beijing Institute of Machinery, Beijing 100085, china department of Mechanics,{2., shanghai 200072, china department of engineering Mechanics, shanghai Jiaotong university, shanghai 2.0030, china) [a]Beijing Institute of Machiner Beijing China [b]department of Mechanics Shanghai University Shanghai China [c]department of engineering Mechanics Shanghai Jiaotong University Shanghai China

An optimal motion planning scheme using wavelet approximation is proposed for an underactuated spacecraft. The motion planning of an underactuated spacecraft can be formulated as an optimal control of a drift-free system. A cost functional is used to incorporate the control energy and the final state errors. The motion planning is to determine control inputs to minimize the cost functional. Using the method of wavelet, one can transform an infinite-dimensional optimal control problem to a finite-dimensional one and use Gauss-Newton algorithm to solve it for a feasible trajectory which satisfies nonholonomic constraints. The proposed scheme has been applied to a rigid spacecraft with two momentum wheels. The numerical simulation results indicate that optimal control with wavelet approximation is an effective approach to steering an underactuated spacecraft system from the initial configuration to the final configuration.

关键词： underactuated spacecraft motion planning optimal control nonholonomic constraint wavelet analysis.

Some variational principles in electroelastic media under finite deformation

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Science china(Physics,Mechanics & Astronomy) 2008年第9期51卷 1390-1402页

作者： KUANG ZhenBang department of engineering Mechanics,{2. Jiaotong university,{2. 2.02.0,china department of engineering Mechanics Shanghai Jiaotong University Shanghai 200240 China

It is proposed that the universal thermodynamic energy variational principle is in-cluded in the first law of thermodynamics. Some variational principles in the elec-troelastic media under finite deformation are derived from this universal thermo-dynamic variational principle. It is suggested that in the general electroelastic analysis the environment should be considered together with the discussed elec-troelastic medium. For the variational principle of nonlinear electroelastic media the variation of the electric potential is coupled with the virtual displacement,and the variation of the initial volume should be considered. The Maxwell stress in the initial configuration is naturally derived from this variational principle and it is unique in the second order precision.

关键词： first law of thermodynamics variational principle the electroelastic media the governing equation