材料力学英文版ch09.1-3.ppt

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1、Chapter9Stengththeories9.1Introduction9.2Strengththeoriesforfracture9.3Strengththeoriesforyielding9.4Combinedbenging–torsion;combinedbending-axialload-torsion9.5Generalcasesof§combinedloadsforbarswithrectangularcross-section9.6Thin-walledpressurecircularcylinders9.7Experimen

2、talverificationoffailuretheories9.8MohrtheoryoffailureStrebgthTheories一、Complicationoffailureofmaterials9.1IntroductionMPBasicassumption：Simpletestcanbeusedtosetupstrengththeoriesatcomplicatedstressstate.FailuretypesFracture（Brittle）Yielding（Plastic）WhyfailureRelatedtoMATERI

3、ALS,STRESSSTATEAnystregnththeoriesmusttobeverifiedbyexperimentOnefactor（stress、strain、strainenergy）,ultimatevalueofwhichisindependentofthestressstateStrebgthTheories1、Maximumtensilestresstheory（最大拉应力理论）（伽利略播下）2、Maximumtensilestraintheory（最大拉应变理论）（马里奥特关于变形过大引起破坏的论述是该理论萌芽)3、Ma

4、ximumshearingstresstheory（最大切应力理论）（杜奎特：C.Duguet提出)4、Maximumdistortionenergytheory（最大畸变能理论）（vonMises提出）2、CommenstrengththeoriesStrebgthTheories9.2Strengththeoriesforfracture一、Maximumtensilestress（firststrength）theory：Marerialfractureisduetomaximumtensilestress.Oncethemaximumt

5、ensilestressreachestheultimatestrengthunderone-direnctionaltension,thefracturetakesplace.1、Fracturecriterion：2、Strengthcriterion：3、Rangeofapplication：Brittlefracture.StrebgthTheories二、Maximumtensilestrain(Thesecondstrength)theory：Marerialfractureisduetomaximumtensilestrain.O

6、ncethemaximumtensilestrainreachestheultimatetensilestrainunderone-direnctionaltension,thefracturetakesplace.2、Strengthcondition：3、Rangeofapplication：Brittlefracture.Failurecriterion：1、Failurecriterion：EquivalentStrebgthTheories一、Maximumshearingstress(thethirdstrength)theory：

7、1、Failurecriterion：3、Rangeofapplication：Membersdamagedintheformofyielding.2、Strengthcondition：Failurecriterion：9.3StrengththeoriesforyieldingMarerialyieldingisduetomaximumshearingstress.Oncethemaximumshearingstressreachestheultimateshearingstressunderone-direnctionaltension,

8、theyieldingtakesplace.EquilalentstressStrebgthTheories二、Maximumdistortionen