检索结果-南通市图书馆

Base force element method (BFEM) on complementary energy principle for linear elasticity problem

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2011年第11期54卷 2025-2032页

作者： liu yinghua PENG YiJiang Applied Mechanics Laboratory Department of Engineering Mechanics Tsinghua University Beijing 100084 China Key Lab of Urban Security ＆ Disaster Engineering Department of Civil Engineering Beijing University of Technology Beijing 100124 China

Using the concept of base forces as state variables,a new finite element method-the base force element method (BFEM) on complementary energy principle for linear elasticity problems is ***,an explicit expression of compliance matrix for an element is derived through base forces by dyadic ***,the explicit control equations of finite element method of complementary energy principle are derived using Lagrange multiplier ***,the base forces element procedure for linear elasticity is ***,several examples are analyzed to illustrate the reliability and accuracy of the formulation and the procedure.

关键词： base forces elasticity problem complementary energy principle finite element method base force element method,Lagrange multiplier method compliance matrix

Structural dynamic responses of a stripped solar sail subjected to solar radiation pressure

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2020年第8期33卷 2204-2211页

作者： Junhui ZHANG Na WU An TONG yinghua liu School of Civil Engineering North China University of TechnologyBeijing 100144China School of Aerospace Engineering Tsinghua UniversityBeijing 100144China

The stripped solar sail whose membrane is divided into separate narrow membrane strips is believed to have the best structural *** this paper,the stripped solar sail structure is regarded as an assembly made by connecting a number of boom-strip components in *** the coupling effects between booms and membrane strips,an exact and semianalytical method to calculate structural dynamic responses of the stripped solar sail subjected to solar radiation pressure is *** case study of a 100 m stripped solar sail shows that the stripped architecture helps to reduce the static deflections and amplitudes of the steady-state dynamic *** prestress of the membrane strips will decrease stiffness of the sail and increase amplitudes of the steady-state dynamic *** thickness of the boom will benefit to stability of the sail and reduce the resonant *** proposed semi-analytical method provides an efficient analysis tool for structure design and attitude control of the stripped solar sail.

关键词： Distributed transfer function method Frequency response Solar radiation pressure Solar sail Structural dynamic response

Thermoelastic coupling problems caused by thermal contact resistance:A discontinuous Galerkin finite element approach

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2011年第4期54卷 666-674页

作者： ZHENG XiaoPing liu DongHuan liu yinghua Applied Mechanics Laboratory Department of Engineering Mechanics Tsinghua University Beijing 100084 China Department of Mathematics and Mechanics University of Science & Technology Beijing Beijing 100083 China

A discontinuous Galerkin (DG) finite element method is presented to solve the thermoelastic coupling problems caused by temperature and pressure dependent thermal contact resistance (TCR).The whole analysis is made up of two parts,thermal and mechanical *** thermal analysis,the DG method is employed to simulate the temperature jump phenomenon,which satisfies the imperfect thermal contact condition in a straightforward *** mechanical analysis,the impenetrability condition is fulfilled through a DG approach with penalty *** Picard iteration procedure with a relaxation technique is also adopted to accelerate the rate of convergence and avoid numerical *** examples show that the present method is an attractive approach for solving thermoelastic coupling problems caused by *** methodology can also be expanded to solve problems with friction finite deformation contact,node-to-segment contact and node-to-surface contact,*** a straightforward manner.

关键词： thermoelastic coupling thermal contact resistance discontinuous Galerkin method penalty method relaxation technique

A LOWER BOUND LIMIT ANALYSIS OF DUCTILE COMPOSITE MATERIALS

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2005年第3期18卷 215-224页

作者： Zhang Hongtao liu yinghua Xu Bingye Department of Engineering Mechanics FML Tsinghua University Beijing 100084 China

The plastic load-bearing capacity of ductile composites such as metal matrix composites is studied with an insight into the microstructures. The macroscopic strength of a composite is obtained by combining the homogenization theory with static limit analysis, where the temperature parameter method is used to construct the self-equilibrium stress field. An interface failure model is proposed to account for the effects of the interface on the failure of composites. The static limit analysis with the finite-element method is then formulated as a constrained nonlinear programming problem, which is solved by the Sequential Quadratic Programming （SQP） method. Finally, the macroscopic transverse strength of perforated materials, the macroscopic transverse and off-axis strength of fiber-reinforced composites are obtained through numerical calculation. The computational results are in good agreement with the experimental data.

关键词： limit analysis homogenization theory interface failure temperature parameter method

MODE III 2-D FRACTURE ANALYSIS BY THE SCALED BOUNDARY FINITE ELEMENT METHOD

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2013年第6期26卷 619-628页

作者： Shenshen Chen Qinghua Li yinghua liu Zhiqing Xue College of Civil Engineering Hunan University of Technology Department of Engineering Mechanics School of AerospaceTsinghua University

The scaled boundary finite element method （SBFEM） is a novel semi-analytical technique that combines the advantages of the finite element method and the boundary element method with unique properties of its own. This method has proven very efficient and accurate for determining the stress intensity factors （SIFs） for mode I and mode II two-dimensional crack problems. One main reason is that the SBFEM has a unique capacity of analytically representing the stress singularities at the crack tip. In this paper the SBFEM is developed for mode III （out of plane deformation） two-dimensional fracture anMysis. In addition, cubic B-spline functions are employed in this paper for constructing the shape functions in the circumferential direction so that higher continuity between elements is obtained. Numerical examples are presented at the end to demonstrate the simplicity and accuracy of the present approach for mode Ⅲ two-dimensional fracture analysis.

关键词： fracture mechanics scaled boundary finite element method mode Ⅲ stress in- tensity factors

PLASTIC LIMIT ANALYSIS OF DUCTILE COMPOSITE STRUCTURES FROM MICRO-TO MACRO-MECHANICAL ANALYSIS

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2009年第1期22卷 73-84页

作者： Hongtao Zhang yinghua liu Binge Xu Department of Civil Engineering University of Science and Technology Beijing Beijing 100083 China Department of Engineering Mechanics Tsinghua University Beijing 100084 China

The load-bearing capacity of ductile composite structures comprised of periodic composites is studied by a combined micro/macromechanicai approach. Firstly, on the microscopic level, a representative volume element （RVE） is selected to reflect the microstructures of the composite materials and the constituents are assumed to be elastic perfectly-plastic. Based on the homogenization theory and the static limit theorem, an optimization formulation to directly calculate the macroscopic strength domain of the RVE is obtained. The finite element modeling of the static limit analysis is formulated as a nonlinear mathematical programming and solved by the sequential quadratic programming method, where the temperature parameter method is used to construct the self-stress field. Secondly, Hill＇s yield criterion is adopted to connect the micromechanicai and macromechanical analyses. And the limit loads of composite structures are worked out on the macroscopic scale. Finally, some examples and comparisons are shown.

关键词： periodic composites limit analysis homogenization micro/macromechanics

Boundary element analysis for elastic and elastoplastic problems of 2D orthotropic media with stress concentration

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2005年第5期21卷 472-484页

作者： Xiushan Sun Lixin Huang yinghua liu Zhangzhi Cen Department of Engineering Mechanics Tsinghua UniversityBeiiing 100084 China College of Civil Engineering and Architecture Guangxi University Nanning 530004 Guangxi China

Both the orthotropy and the stress concentration are common issues in modem structural engineering. This paper introduces the boundary element method （BEM） into the elastic and elastoplastic analyses for 2D orthotropic media with stress concentration. The discretized boundary element formulations are established, and the stress formulae as well as the fundamental solutions are derived in matrix notations. The numerical procedures are proposed to analyze both elastic and elastoplastic problems of 2D orthotropic me- dia with stress concentration. To obtain more precise stress values with fewer elements, the quadratic isoparametric element formulation is adopted in the boundary discretization and numerical procedures. Numerical examples show that there are significant stress concentrations and different elastoplastic behaviors in some orthotropic media, and some of the computational results are compared with other solutions. Good agreements are also observed, which demonstrates the efficiency and reliability of the present BEM in the stress concentration analysis for orthotropic media.

关键词： Boundary element method (BEM) . Fundamental solution . Orthotropic medium . Stress concentration .Elastic and elastoplastic problems

MICRO/MACROMECHANICAL PLASTIC LIMIT ANALYSES OF COMPOSITE MATERIALS AND STRUCTURES

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2001年第4期14卷 323-333页

作者： Li Huaxiang liu yinghua Feng Xiqiao Tsing Hua Univ Dept Engn Mech Beijing 100084 Peoples R China

The load-bearing capacities f ductile composite materials andstructures are studied by means of a combined micro/macromechanicsapproach. Firstly, on the microscopic scale, the aim is to get themacroscopic strength domains by means of the homogenization theory ofmicromechanics. A representative volume element (RVE) is selected toreflect the microstructures of the composite materials. Byintroducing the homogenization theory into the kinematic limittheorem of plastic limit analysis, an optimization format to directlycalculate the limit loads of the RVE is obtained. And the macroscopicyield criterion can be deter- mined according to the relation betweenmacroscopic and microscopic fields.

关键词： composite homogenization theory representative volume element finiteelement method

STRENGTH PROPERTIES OF JOINTED ROCK MASSES BASED ON THE HOMOGENIZATION METHOD

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2012年第2期25卷 177-185页

作者： Hongtao Zhang Jianming Zhu yinghua liu Bingye Xu Xiaochun Wang Department of Civil Engineering North China University of TechnologyBeijing 100144China Department of Engineering Mechanics Tsinghua UniversityBeijing 100084China

This paper aims to determine the strength properties of jointed rock masses by means of the homogenization method. To reflect the microstructure of jointed rock masses, a representative element volume （REV） is selected. Assuming being rigid and perfectly plastic and utilizing the Mohr-Coulomb yield criterion for rock and joints, an upper bound limit analysis method is proposed based on the homogenization theory. By using the finite element method and Goodman joint element, a nonlinear mathematical programming with equality constraints is formulated, which can be solved by a direct iterative algorithm. Numerical results show the strength of jointed rock masses behaves anisotropy with different joint directions. This method presents an effective tool for the strength analysis of jointed rock masses.

关键词： jointed rock mass homogenization representative element volume (REV) upperbound limit analysis anisotropy