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1、原文:Stress-StrainRelationshipsandBehavior5.1INRODUCTION5.2MODELSFORDEFORMATIONBEHAVIOR5.3ELASTICDEFORMATION5.4ANISOTROPICMATERIALS5.5SUMMARYOBJECTIVESlBecomefamiliarwiththeelastic,plastic,steadycreep,andtransientcreeptypesofstrain,aswellassimplerheologicalmodels
2、forrepresentingthestress-strain-timebehaviorforeach.lExplorethree-dimensionalstress-strainrelationshipsforlinear-elasticdeformationinisotropicmaterials,analyzingtheinterdependenceofstressesorstrainsimposedinmorethanonedirection.lExtendtheknowledgeofelasticbehav
3、iortobasiccasesofanisotropy,includingsheetsofmatrix-and–fibercompositematerial.5.1INRODUCTIONThethreemajortypesofdeformationthatoccurinengineeringmaterialsareelastic,plastic,andcreepdeformation.ThesehavealreadybeendiscussedinChapter2fromtheviewpointofphysicalme
4、chanismsandgeneraltrendsinbehaviorformetals,polymers,andceramics.Recallthatelasticdeformationisassociatedwiththestretching,butnotbreaking,ofchemicalbonds.Incontrast,thetwotypesofinelasticdeformationinvolveprocesseswhereatomschangetheirrelativepositions,suchassl
5、ipofcrystalplanesorslidingifchainmolecules.Iftheinelasticdeformationistimedependent,itisclassedascreep,asdistinguishedfromplasticdeformation,whichisnottimedependent.Inengineeringdesignandanalysis,equationsdescribingstress-strainbehavior,calledstress-strainrelat
6、ionships,orconstitutiveequations,arefrequentlyneeded.Forexample,inelementarymechanicsofmaterials,elasticbehaviorwithalinearstress-strainrelationshipisassumedandusedincalculatingstressesanddeflectionsinsimplecomponentssuchasbeamsandshafts.Morecomplexsituationsof
7、geometryandloadingcanbeanalyzedbyemployingthesamebasicassumptionsintheformoftheoryofelasticity.Thisisnowoftenaccomplishedbyusingthenumericaltechniquecalledfiniteelementanalysiswithadigitalcomputer.Stress-strainrelationshipsneedtoconsiderbehaviorinthreedimension
8、s.Inadditiontoelasticstrains,theequationsmayalsoneedtoincludeplasticstrainsandcreepstrains.Treatmentofcreepstrainrequirestheintroductionoftimeasanadditionalvariable.Regardle