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1.
IntroductionIn 1 975,B .Mandelbrotadvancedtheconception“fractal”andestablishedhisfractalgeometrytheory .Nowadays,thefractalgeometryisregardedasoneofthebesttoolstodescribethenonlinearproblems.Italsoimprovedthedevelopmentofmanyrelatedfields,suchasdynamicssyst…  相似文献   

2.
IntroductionUptonow ,thetechnicalliteratureonseparatecracks,voids,inclusionsandtheinteractionsbetweencracksandinclusionshavebeenquiteextensive.However,thecontactproblemsofcrack_inclusiondonotseemtobeaswidelystudied .Thispapercanberegardedasthefurtherrese…  相似文献   

3.
IntroductionTheone_dimensionalMHDequationsunderLagrangecoordinateare τ t- u x=0 , u t P x 18π x(H2 y H2 z) =0 , Hy t Hyτ u x =0 , Hz t Hzτ u x=0 , S t=0 ,( 1 )whereu ,τ,Hy,HzandSthevelocity ,specificvolume,thecomponentsofmagneticfieldiny_andz_diectionsandtheentropyrespectively .T…  相似文献   

4.
Therearemanydocumentsthatdiscussblow_upofthesolutionsfortheinitial_boundaryvlueproblemsofthenonlinearSchr dingerequations,suchaspaper [1 ] .Butthepaper [1 ]hasoneweakpoint,thatis,itcannotunitediscussionforblow_upofthesolutionsfortheinitial_boundaryvalueprobl…  相似文献   

5.
IntroductionWhilewestudythestrengthandthecrackofpractisingcomponents,thematerialdefectionshouldbeconsidered .IntheopinionsofCrackMechanics,thematerialdefectioncanbereducedtoplanarcracksandinclusions.Besides,theproblemofshort_fibercompositematerialsuchas…  相似文献   

6.
IntroductionAnunevendistributionoftheclearanceofvane_tipalongthecircumferenceorientationcausedbytherelativeeccentricitybetweenimpellerandcylinderofsteamturbinewillresultunequalpneumaticforceofthevanesatthesamestage .Asaresult,inadditiontoatorque,thetra…  相似文献   

7.
RESEARCH ON THE EFFECT OF PARTICLE OF TWO-DIMENSIONAL SHEAR FLOW   总被引:2,自引:0,他引:2  
IntroductionTurbulentflowladenwithparticlesiscommoninbothnatureandindustry .Themixingdegreeofparticlesinthegas_solidflowissignificanttoindustrialapplications.Therecentresearchesindicatethatthecoherentstructuresexistinthemixinglayer.Croweetal.[1]evaluated…  相似文献   

8.
IntroductionThereexistmanyimperfectionsthatareimpossibletoavoidinanengineeringstructure.Someimportantexperiments[1,2]haveshownthatimperfectionsinastructuremaymakethecriticalloaddecreaseevidently.Sotheinfluenceofimperfectionsuponthecriticalloadofthest…  相似文献   

9.
IntroductionConservationlawofmechanicalsystemnotonlyhasimportanceinmathematicsbutalsorevealsprofoundphysicallaw .Therearemanymethodsinfindingconservationlawofamechanicalsystem .Inanalyticalmechanicsthetraditionalmethodistodirectlyderivethecircularinteg…  相似文献   

10.
1 ProblemintheResearchofToroidImpulsivedifferentialequationisanewimportantbranchofdifferentialequation.In1989,[1],[2]systematicallysummarizedresearchworkaboutimpulsiveordinarydifferentialequations.Inrecentyears,therearemanyliteraturesdealingwiththeoscillatio…  相似文献   

11.
IntroductionCompositelaminatedcylindricalpanelhasbeenusedextensivelyasastructuralconfiguration,mainlyintheaerospaceindustry .Oneoftherecentadvancesinmaterialandstructuralengineeringisinthefieldofsmartstructureswhichincorporatesadaptivematerials.Bytakingadvantageofthedirectandconversepiezoelectriceffects,piezoelectriccompositestructurescancombinethetraditionalperformanceadvantagesofcompositelaminatesalongwiththeinherentcapabilityofpiezoelectricmaterialstoadapttotheircurrentenvironment.Therefore…  相似文献   

12.
IntroductionInrecentyears,fiber_reinforcedcompositelaminatedpanelshavebeenwidelyusedintheaerospace,marine ,automobileandotherengineeringindustries .Theproblemofbucklingandpostbucklingofcylindricalpanelsunderaxialcompressionortorsionhasbeenextensivelystudied .Incontrast,theliteratureoncylindricalpanelsunderpressureloadingisrelativelyspares.Thesestudiesincludealinearbucklinganalysis (Singeretal.[1]) ,anonlinearbucklinganalysi(YamadaandCroll[2 ]) ,anelastoplasticbucklinganalysisusingreducedstif…  相似文献   

13.
A compressive postbuckling analysis is presented for a laminated cylindrical shell with piezoelectric actuators subjected to the combined action of mechanical, electric and thermal loads. The temperature field considered is assumed to be a uniform distribution over the shell surface and through the shell thickness, and the electric field is assumed to be the transverse component EZ only. The material properties are assumed to be independent of the temperature and the electric field. The governing equations are based on the classical shell theory with von Kármán–Donnell-type kinematic nonlinearity. The nonlinear prebuckling deformations and initial geometric imperfections of the shell are both taken into account. A boundary layer theory of shell buckling, which includes the effects of nonlinear prebuckling deformations, large deflections in the postbuckling range, and initial geometric imperfections of the shell, is extended to the case of hybrid laminated cylindrical shells. A singular perturbation technique is employed to determine the buckling loads and postbuckling equilibrium paths. The numerical illustrations concern the compressive postbuckling behavior of perfect and imperfect, cross-ply laminated cylindrical thin shells with fully covered or embedded piezoelectric actuators under different sets of thermal and electric loading conditions. The effects played by temperature rise, applied voltage, shell geometric parameter, stacking sequence, as well as initial geometric imperfections are studied.  相似文献   

14.
An elastic double-shell model is presented for the buckling and postbuckling of a double-walled carbon nanotube subjected to axial compression. The analysis is based on a continuum mechanics model in which each tube of a double-walled carbon nanotube is described as an individual elastic shell and the interlayer friction is negligible between the inner and outer tubes. The governing equations are based on the Karman–Donnell-type nonlinear differential equations. The van der Waals interaction between the inner and outer nanotubes and the nonlinear prebuckling deformations of the shell are both taken into account. A boundary layer theory of shell buckling is extended to the case of double-walled carbon nanotubes under axial compression. A singular perturbation technique is employed to determine the buckling loads and postbuckling equilibrium paths. Numerical results reveal that the single-walled carbon nanotube and the double-walled carbon nanotube both have an unstable postbuckling behavior.  相似文献   

15.
A buckling theory valid for finite prebuckling deformations is presented for thin homogeneous, isotropic and elastic shells. It is subject to the restriction of the Kirchhoff hypothesis. A set of stability equations is derived by decomposing strain and stress components into four classes according to their characteristics.The influence of the prebuckling deformations on the buckling of thin circular cylindrical shells under lateral pressure is investigated with the aid of the basic equations derived above and the results are compared with the solutions of the Flügge equations and those obtained by Yamaki.  相似文献   

16.
The size-dependent nonlinear buckling and postbuckling characteristics of circular cylindrical nanoshells subjected to the axial compressive load are investigated with an analytical approach. The surface energy effects are taken into account according to the surface elasticity theory of Gurtin and Murdoch. The developed geometrically nonlinear shell model is based on the classical Donnell shell theory and the von K′arm′an's hypothesis. With the numerical results, the effect of the surface stress on the nonlinear buckling and postbuckling behaviors of nanoshells made of Si and Al is studied. Moreover, the influence of the surface residual tension and the radius-to-thickness ratio is illustrated.The results indicate that the surface stress has an important effect on prebuckling and postbuckling characteristics of nanoshells with small sizes.  相似文献   

17.
This paper presents a study on the postbuckling response of a functionally graded cylindrical shell of finite length embedded in a large outer elastic medium and subjected to internal pressure in thermal environments. The surrounding elastic medium is modeled as a tensionless Pasternak foundation that reacts in compression only. The postbuckling analysis is based on a higher order shear deformation shell theory with von Kármán–Donnell-type of kinematic nonlinearity. The thermal effects due to heat conduction are also included and the material properties of functionally graded materials (FGMs) are assumed to be temperature-dependent. The nonlinear prebuckling deformations and the initial geometric imperfections of the shell are both taken into account. A singular perturbation technique is employed to determine the postbuckling response of the shells and an iterative scheme is developed to obtain numerical results without using any assumption on the shape of the contact region between the shell and the elastic medium. Numerical solutions are presented in tabular and graphical forms to study the postbuckling behavior of FGM shells surrounded by an elastic medium of tensionless elastic foundation of the Pasternak-type, from which results for conventional elastic foundations are obtained as comparators. The results reveal that the unilateral constraint has a significant effect on the postbuckling response of shells subjected to internal pressure in thermal environments when the foundation stiffness is sufficiently large.  相似文献   

18.
A postbuckling analysis is presented for a functionally graded cylindrical shell subjected to torsion in thermal environments. Heat conduction and temperature-dependent material properties are both taken into account. The temperature field considered is assumed to be a uniform distribution over the shell surface and varied in the thickness direction. The material properties of functionally graded materials (FGMs) are assumed to be graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents, and are assumed to be temperature-dependent. The governing equations are based on a higher order shear deformation theory with a von Kármán–Donnell-type of kinematic non-linearity. The non-linear prebuckling deformations and initial geometric imperfections of the shell are both taken into account. A singular perturbation technique is employed to determine the buckling load and postbuckling equilibrium paths. The numerical illustrations concern the postbuckling behavior of twist, perfect and imperfect, FGM cylindrical shells under different sets of thermal fields. The results reveal that the volume fraction distribution of FGMs has a significant effect on the buckling load and postbuckling behavior of FGM cylindrical shells subjected to torsion. They also confirm that the torsional postbuckling equilibrium path is weakly unstable and the shell structure is virtually imperfection–insensitive.  相似文献   

19.
A postbuckling analysis is presented for a shear deformable functionally graded cylindrical shell of finite length subjected to combined axial and radial loads in thermal environments. Heat conduction and temperature-dependent material properties are both taken into account. The temperature field considered is assumed to be a uniform distribution over the shell surface and varied in the thickness direction only. Material properties are assumed to be temperature-dependent, and graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents. The formulations are based on a higher order shear deformation shell theory with von Kármán–Donnell-type of kinematic nonlinearity. A boundary layer theory of shell buckling, which includes the effects of nonlinear prebuckling deformations, large deflections in the postbuckling range, and initial geometric imperfections of the shell, is extended to the case of functionally graded cylindrical shells. A singular perturbation technique is employed to determine the interactive buckling loads and postbuckling equilibrium paths. The numerical illustrations concern the postbuckling response of perfect and imperfect cylindrical shells with two constituent materials subjected to combined axial and radial mechanical loads and under different sets of thermal environments. The results reveal that the temperature field and volume fraction distribution have a significant effect on the postbuckling behavior, but they have a small effect on the imperfection sensitivity of the functionally graded shell.  相似文献   

20.
PLASTICBUCKLINGOFSTIFFENEDTORISPHERICALSHELLHaoGang(郝刚)ZengGuangwu(曾广武)HaoQiang(郝强)(ReceivedDec.30,1994:CommunicatedbyPanLizh...  相似文献   

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