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1.
IntroductionThemovingbehaviorofasymmetricmultistorybuildingswithregularasymmetryissimilartosinglestoryasymmetricbuildingsinelasticrange ,andthusthesinglestorybuildingisalwaysconsideredasarepresentativebuildingofasymmetricinelasticrange .Butinelasticsei…  相似文献   

2.
IntroductionEquationsforcircularringshellsaredifficulttosolve.Theresearchofthisproblemstartedatthebeginningofthiscentury.Inthelate1970sandearly1980s,W.Z.Chien(1979,1980,1981)[1~3]rebuiltthecomplexequationsofaxis_symmetricallyloadedringshellspresented…  相似文献   

3.
IntroductionInthispaper,westudytheunsteadyaxisymmetricincompressibleflowbetweentwoconcentricspheres.Thisflowiscalledasspheric...  相似文献   

4.
IntroductionAgeneraltheoryoftheleast_squaresmethodhasbeendevelopedbyAKAziz,RBKelloggandABStephensin[1].Themostimportantadvantageleadstoasymmetricpositivedefiniteproblem.JHBrambleandJANitshepresentedaleast_squaresmethodforDirichletproblemsin[2].Themethodge…  相似文献   

5.
IntroductionU_shapedbellowsareusuallyseeninthepipelinesystem (Fig .1) ,whichareusedtocompensatefortheaxialmovement,therotationandthedeflectionofthepipelinesduetothethermalaction ,thebaseunequalsettlementsandtheinstallationerrors.Theaxisymmetricaldeformatio…  相似文献   

6.
GENERAL SOLUTION FOR U-SHAPED BELLOWS OVERALL-BENDING PROBLEMS   总被引:1,自引:0,他引:1  
IntroductionU_shapedbellows,anelasticelement,showninFig .1 ,isusedinmanywaysandingeneralsubjecttopressure ,axialforce ,lateralforcesandmoments.Inresearch ,itisusuallysimplifiedintoringshellsandringplates.TheaxisymmetricalproblemsofU_shapedbellowshavebeendee…  相似文献   

7.
IntroductionInseveralpreviouspapers[1,2,3],Eringendiscussedthestateofstressnearthetipofasharplinecrackinanelasticplatesubjecttouniformtension,shearandanti_planeshear.Thefieldequationsemployedinthesolutionoftheseproblemsarethoseofthetheoryofnon_locale…  相似文献   

8.
Recursionoperatorsarequiteusefulforconstructingthesymmetriesofdifferentialequationsandforsomerelatedquestions.TheirgeneralformswerefirstpresentedbyOlver(1977),thoughtherecursionproperties,especiallyonevolutionequations,hadbeeninvestigatedwellbymanyot…  相似文献   

9.
IntroductionThediscoveryofquasicrystalaround 1 984 [1,2 ,3]issignificantbreakthroughforcondensedmatterphysicsinrecentyears.Thequasiperiodicsymmetryofsolidpresentsgreattheoreticalsignificance .Numerousquasicrystallinematerialswithstablepropertywereproduced ,thi…  相似文献   

10.
IntroductionThepurposeofthispaperistodevelopacuratediferencemethodforthefolowinginitialvalueproblem,whichisinsingularperturba...  相似文献   

11.
复杂结构动态应力的准确计算是一个没有圆满解决的问题。本文以最小余能原理为基础,提出了计算结构动态应力的最小伤痛有法。该方法采用二次分析思想,首先采用常规有限元对结构进行适当离散,计算输出结构所需应力区域的有限元结点位移和加速度动力时程反应,再应用最小余能法计算所求部位的动态应力值。这种方法的优点是它可以与现有的有限元程序有机结合,方便使用;动应力在区域内的分布规律可以由计算者根据具体情况而确定,一般情况下,可以选用二次曲线来逼近动应力在区域内的实际分布,避免了常规有限元法计算结构动应力时必须对单元形函数求导的做法,从而提高了动应力计算精度。计算结果表明:本文方法计算结构动态应力结果较常规有限元法的计算结果有明显改进,特别是当结构变化剧烈时,改进效果更为明显。  相似文献   

12.
The effect of the first non-singular stress term on the fracture behavior of notched structures was investigated under symmetric geometry and loading conditions. According to the Williams series expansion, for a large domain of notch angles the non-singular stress terms of sharp notches are functions of complex eigenvalues and their corresponding complex coefficients. Hence, a new representation of stress field near the notch tip was developed in which the higher order terms are expressed as several explicit functions of real and imaginary parts of both the complex eigenvalues and their complex coefficients. A critical stress criterion was then applied to the new stress formulations to assess the influence of the first non-singular stress term on the apparent fracture toughness. Several finite element analyses were also performed on two laboratory specimens in order to show the effects of first non-singular term on the near field stress distribution of notched specimens. The results demonstrated that neglecting the first non-singular stress term could lead to significant errors in predicting the apparent fracture toughness of notched components.  相似文献   

13.
结构安定分析的Galerkin边界元方法   总被引:2,自引:0,他引:2  
基于Melan静力安定定理,利用Galerkin边界元方法建立了多组交变载荷作用下结构安定分析的下限计算格式.在给定载荷域的载荷角点所对应载荷作用下,采用Galerkin边界元法计算相应的虚拟弹性应力场,并且利用结构在Galerkin边界元弹塑性增量计算中同一增量步中不同迭代步之间的应力差作为自平衡应力场的基矢量,通过这些基矢量的线性组合构造了自平衡应力场,大大降低了所形成的数学规划问题的未知变量数.并通过复合形法对非线性规划问题直接进行求解,得到了结构在交变载荷作用下的下限安定乘子.计算结果表明,所采用的方法具有较高的精度和计算效率.  相似文献   

14.
A stress function-based approach is proposed to analyze the free-edge interlaminar stresses of piezo-bonded symmetric laminates. The proposed method satisfies the traction free boundary conditions, as well as surface free conditions. The symmetric laminated structure was excited under electric fields that can generate induced strain, resulting in pure extension in the laminated plate. The governing equations were obtained by taking the principle of complementary virtual work. To verify the proposed method, cross-ply, angle-ply and quasi-isotropic laminates were analyzed. The stress concentrations predicted by the present method were compared with those analyzed by the finite element method. The results show that the stress function-based analysis of piezo-bonded laminated composite structures is an efficient and accurate method for the initial design stage of piezo-bonded composite structures.  相似文献   

15.
By considering the characteristics of deformation of rotationally periodic structures under rotationally periodic loads, the periodic structure is divided into some identical substructures in this study. The degrees-of-freedom (DOFs) of joint nodes between the neighboring substructures are classified as master and slave ones. The stress and strain conditions of the whole structure are obtained by solving the elastic static equations for only one substructure by introducing the displacement constraints between master and slave DOFs. The complex constraint method is used to get the bifurcation buckling load and mode for the whole rotationally periodic structure by solving the eigenvalue problem for only one substructure without introducing any additional approximation. The finite element (FE) formulation of shell element of relative degrees of freedom (SERDF) in the buckling analysis is derived. Different measures of tackling internal degrees of freedom for different kinds of buckling problems and different stages of numerical analysis are presented. Some numerical examples are given to illustrate the high efficiency and validity of this method.  相似文献   

16.
针对夹层板力学性能解析法难于计算复杂结构的夹层板且通用性差的问题,本文采用有限元分析法研究了夹层板性能的等效方法。对夹层板的代表体单元模型施加位移约束,模拟弯曲变形时线性独立的应变分量和弯曲内力;根据夹层板内力与应变的本构关系,求出刚度矩阵;最后由刚度矩阵得出宏观等效弹性常数,从而把夹层板等效成连续材料的单层板单元。将该方法与解析法计算结果进行比较得到的夹层板单元四个主要弹性常数误差在0.2%以内,验证了该方法的有效性;另外采用该方法等效三种典型结构夹层板,比较实际模型和等效模型的弯曲响应,得到的误差均在1.4%以内,表明该方法在不考虑复杂多变的夹芯结构时具有通用性。  相似文献   

17.
从工程数学求解和有限元分析角度对复合材料结构的稳定性分析方法进行研究,基于这两个方面分别建立了同时考虑壁板稳定性约束和气动弹性约 束的气动弹性优化技术,并以大展弦比复合材料机翼为对象,进行气动弹性综合优化设计。研究表明,机翼气动弹性优化中若不考虑稳定性约束条件,虽然可以获得较小结构重量,但往往不满足稳定性要求;相比从有限元角度考虑结构失稳特征的气动弹性综合优化设计方法,通过工程数学方法对机翼结构进行分区失稳分析优化可以更加精准地控制变量,在满足各项性能指标,特别是稳定性约束的同时,进一步减轻了结构重量,提高了结构失稳因子。  相似文献   

18.
Hybrid equilibrium finite elements based on the direct approximation of the domain stress and boundary displacement fields are presented. The structure is divided into a far field, which is considered as an infinite super element, and a near field, which is in turn discretized into finite elements. The displacements in the domains of typical finite elements are obtained from the assumed domain stress field by using the dynamic equilibrium equations. The Helmholtz equation is satisfied in the domain of the infinite super element, and the domain stress fields are associated with elastic and compatible displacements. The resulting governing system is symmetric, sparse, and, if well done, positive. Numerical applications are presented to illustrate the performance of the formulation  相似文献   

19.
A strategy for the mixed-dimensional coupling of finite shell elements and 3D boundary elements is presented. The stiffness formulation for the boundary element domain is generated by the 3D symmetric Galerkin boundary element method and thus can be assembled to the global finite element formulation. Based on the equality of work at the coupling interface, coupling equations in an integral sense are derived for curved coupling interfaces and formulated as multipoint constraints in terms of kinematic quantities. Several examples show the highly accurate results compared to a strict kinematic coupling technique.  相似文献   

20.
The symmetric Galerkin boundary element method (SGBEM) instead of the finite element method is used to perform lower bound limit and shakedown analysis of structures. The self-equilibrium stress fields are constructed by a linear combination of several basic self-equilibrium stress fields with parameters to be determined. These basic self-equilibrium stress fields are expressed as elastic responses of the body to imposed permanent strains and obtained through elastic-plastic incremental analysis. The complex method is used to solve nonlinear programming and determine the maximal load amplifier. The limit analysis is treated as a special case of shakedown analysis in which only the proportional loading is considered. The numerical results show that SGBEM is efficient and accurate for solving limit and shakedown analysis problems. Project supported by the National Natural Science Foundation of China (No. 19902007), the National Foundation for Excellent Doctorial Dissertation of China (No. 200025) and the Basic Research Foundation of Tsinghua University.  相似文献   

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