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应力应变的关系和行为外文文献翻译、中英文翻译、外文翻译.docx

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文档介绍:该【应力应变的关系和行为外文文献翻译、中英文翻译、外文翻译 】是由【zhuwo11】上传分享,文档一共【15】页,该文档可以免费在线阅读,需要了解更多关于【应力应变的关系和行为外文文献翻译、中英文翻译、外文翻译 】的内容,可以使用淘豆网的站内搜索功能,选择自己适合的文档,以下文字是截取该文章内的部分文字,如需要获得完整电子版,请下载此文档到您的设备,方便您编辑和打印。原文:
Stress-StrainRelationshipsandBehavior
INRODUCTION
MODELSFORDEFORMATIONBEHAVIOR
ELASTICDEFORMATION
ANISOTROPICMATERIALS
SUMMARY
OBJECTIVES
Becomefamiliarwiththeelastic,plastic,steadycreep,andtransientcreeptypesofstrain,aswellassimplerheologicalmodelsforrepresentingthestress-strain-timebehaviorforeach.
Explorethree-dimensionalstress-strainrelationshipsforlinear-elasticdeformationinisotropicmaterials,analyzingtheinterdependenceofstressesorstrainsimposedinmorethanonedirection.
Extendtheknowledgeofelasticbehaviortobasiccasesofanisotropy,includingsheetsofmatrix-andfibercompositematerial.

Thethreemajortypesofdeformationthatoccurinengineeringmaterialsareelastic,plastic,,polymers,,butnotbreaking,,thetwotypesofinelasticdeformationinvolveprocesseswhereatomschangetheirrelativepositions,,itisclassedascreep,asdistinguishedfromplasticdeformation,whichisnottimedependent.
Inengineeringdesignandanalysis,equationsdescribingstress-strainbehavior,calledstress-strainrelationships,orconstitutiveequations,,inelementarymechanicsofmaterials,elasticbehaviorwithalinearstress-.
Stress-,,analysistodeterminestressesanddeflectionsalwaysrequiresappropriatestress-strainrelationshipsfortheparticularmaterialinvolved.
Forcalculationsinvolvingstressandstrain,weexpressstrainasadimensionlessquantity,asderivedfromlengthchange,£=△L/,strainsgivenaspercentagesneedtobeconvertedtothedimensionlessform,£=£%/100,asdostrainsgivenasmicrostrain,£=£/IO6.
M
Inthechapter,wewillfirstconsiderone-dimensionalstress-strainbehaviorandsomecorrespondingsimplephysicalmodelsforelastic,plastic,,startingwithisotropicbehavior,,wheretheelasticpropertiesvarywithdirection,,discussionofthree-dimensionalplasticandcreepdeformationbehaviorwillbepostponedtoChapters12and15,respectively.

Simplemechanicaldevices,suchaslinearsprings,frictionalsliders,andviscousdashpots,.
Elasticdeformation,(a),,x=P/k,,(b),|Jareassumedtobeequal,sothatthereisacriticalforceformotionP°=Jmg,'islessthanthecriticalvalue,P'<P0,,ifitisgreater,P'>P0,theblockmoveswithanacceleration
a=(P'-P0)/m ()
Whentheforceisremovedattimet,theblockhasmovedadistancea=at2/2,,themodelbehaviorproducesapermanentdeformation,x.
p
-statecreep,(c),
Description
Model
问PJastlc
.'PI
(cjSteady-sSate£阳已口F=盛
(dirransientereeo
,whichisanelementwherethevelocity,x=dx/dt,,sothataconstantvalueofforceP'givesaconstantvelocity,x=P'/c,,themotionstops,sothatthedeformationispermanent---thatis,,,smallamountsofoilleakpastthepiston,,andthedisplacementwillremainafterallforceisremoved.
Thesecondtypeofcreep,iscalledtransientcreep,(d),'isapplied,,sothatlessforceisavailabletothedashpot,
appliedforceisremoved,thespring,havingbeenextended,nowpullsagainstthe
.
二卩
Siress口-P'A
Strain:―祖df/dt:A讯
FrgureW
関Tof^delsto收赣叔讪“rate,inabarofmateriaL
Rheologicalmodelsmaybeusedtorepresentstressandstraininabarofmaterialunderaxialloading,,theconstantofproportionalitybetweenstressandstrainistheelasticmodulus,alsocalledYoung^smodulus,givenby
E=o/£
()
Substitutingthedefinitionsofstressandstrain,andalsoemployingP=kx,
yieldstherelationshipbetweenEandk:
E=kL/A
()
Fortheplasticdeformationmodel,theyieldstrengthofthematerialissimply
oo=P0/A ()
Forthesteady-statecreepmodel,thematerialconstantanalogoustothedashpotconstantciscalledthecoefficientoftensileviscosity1andisgivenby
()
Where£=d£/=
relationshipbetweennandc:
cL
()
.
Beforeproceedingtothedetaileddiscussionofelasticdeformation,itisusefulto
furthertodiscussplasticandcreepdeformationmodels.

AsdiscussedinChapter2,theprincipalphysicalmechanismcausingplasticdeformationinmetalsandceramicsissliding(slip)betweenplanesofatomsinthecrystalgrainsofthematerial,'sresistancetoplasticdeformationisroughlyanalogoustothefrictionofablockonaplane,(b).
Formodelingstress-strainbehavior,theblockofmassmcanbereplacedbyamasslessfrictionalslider,whichissimilartoaspringclip,(a).Towadditionalmodels,whicharecombinationsoflinearspringsandfrictionalsliders,areshownin(b)and(c).Thesegiveimprovedrepresentationofthebehaviorofrealmaterials,byincludingaspringinserieswiththeslider,sothattheyexhibitelasticbehaviorpriortoyieldingattheslideryieldstrengthaInaddition,model(c)hasasecondlinearspringconnectedparalleltotheslider,(a)issaidtohaverigid,perfectlyplasticbehavior;model(b)elastic,perfectlyplasticbehavior;andmodel(c)elastic,linear-hardeningbehavior.
',,formodels(a)and(b),thestressremainsataobeyondyielding.
Formonotonicloadingofmodel(c),thestrain£isthesumofstrain£1inspringE1andstrains2inthe(E2,ao)parallelcombination:
£=S十匕,£=— ()
1 2 1E
1
Theverticalbarisassumednottorotate,,thesliderpreventsmotion,sothatstrains2iszero:
=0,£
2
(a<ao)
()
SincethereisnodeflectioninspringE2,itsstressiszero,,thesliderhasaconstantstressao,sothatthestressinspringE2is(a-ao).Hence,thestrains2andtheoverallstrainsare
()
0
0;
.3
ComeEpondiog
SirainResponses
芯—3tte2'£
r
nq
—cr
Fi野Rhmbgj询mo4?lsfor丽船deformationandtheirresponsestothree*;響蠶胖畀呵has牝辰湎畑lirigi^perfectlypfastfc;(b)elastic,FrOmthesecond$扯蒯0儿熾6対Ope'Ofthestress-straincuraincurveisseentobe
()
dQ
==12dE eE+E
WhichistheequivalentstiffnessEe,lowerthanbothE1andE2,correspondingtoE1andE2inseries.
,(b)and(c),,,冬,thatisrecoveredcorrespondstotherelaxationofspringE「Thepermanentorplasticstrain£-straincurvesasin(c),butwithelasticunloadingbehaviorsimilartothatoftherheologicalmodels.
NowconsidertheresponseofeachmodeltothesituationofthelastcolumninFig.
,wherethemodelisreloadedafterelasticunloadingtoo=,yieldingoccursasecondtimewhenthestrainagainreachesthevalue£=-hardeningmodelnowyieldsatavalueo=o”,o1isthesamevalueofstressthatwaspresentat£=£”,,yieldingagainoccursatthesameo-£pointfromwhichunloadingoccurred,.
WewillreturntospringandslidermodelsofplasticdeformationinChapter12,wheretheywillbeconsideredinmoredetailandextendedtononlinearhardeningcases.
译文:
应力应变的关系和行为





目标
熟悉弹性应变,塑性应变,稳态蠕变和瞬态蠕变等应变类型,以及每个用来表示应力一—应变与时间相关的简单的流变类型。
探讨在各向同性材料中线性弹性变形的三维的应力应变关系,分析应力应变在多个方向上施加的相互作用力
扩展在各向异性材料中以及一些基体纤维复合材料中弹性形变的基本情况的知识。

工程材料发生变形的三种主要类型是弹性变形,塑性变形,蠕变变形。这些已经在金属聚合物和陶瓷行为的物理机制和一般趋势的观点的第2章中被讨论过了,记得弹性变形与拉伸相关,但是不打破化学键。相比之下,这两种涉及原子的相对位置变化的过程类型的非弹性变形,比如晶面滑移和链分子滑动。如果非弹性变形取决于时间,它被归类为蠕变,区别于不取决于时间的的塑性变形。
在工程设计和分析中,应力应变行为的方程描述,称为应力应变的关系或本构方程是很必要的。比如,在基础材料力学中,与线性应力-应变相关的弹性行为是被假定和用来计算简单的构件如梁和轴的应力和变形的。在更复杂的几何和加载情况下,可以由弹性理论的形式使用相同的基本假设分析。现在经常利用被称为与数字计算机相关的有限元分析的数字科技来完成。
应力应变关系需要考虑在三维中的行为,除了弹性应变外,这个方程可能还需要包括塑性应变和蠕变应变。处理蠕变应变要引入时间作为一个额外的变量。不管用什么方法,对于特定的材料分析确定应力和变形总是需要适当的应力-应变关系。对于应力和应变的计算,我们把应变作为一个无量纲的量表达,来自于长度的变化,£=△L/L。因此,应变给定的百分比需要被转换成无量纲形式,£=£%/100,也可以把应变百分比做为微应变E:=£p/106。
在本章中,我们将首先考虑一维应力应变行为和一些相应的弹性,塑性,蠕变变形的简单的物理模型。弹性变形的探讨将扩展到三个维度,从各向同性行为开始,在所有的方向中的弹性性质是相同的。我们也会考虑在复合材料中各向异性的简单情况,其中的弹性性质随方向而变化。但是,三维塑性变形和蠕变变形行为探讨将分别推迟到第12章和15
章。