chap3_yield criteria.ppt
3YIELDCRITERIA31GENERALCONSIDERATION32YIELDSURFACEANDYIELDLOCUS33COORDINATEONPLANE34TRESCAYIELDCRITERION35MISESYIELDCRITERION36COMPARISONOFTHETWOYIELDINGCRITERIA37EXPERIMENTALVERIFICATIONOFYIELDCRITERIA38PLASTICWORK39EFFECTIVESTRESSANDEFFECTIVESTRAIN31GENERALCONSIDERATIONSYIELDCRITERIAMATERIALYIELDSPLASTICDEFORMATIONSTARTSTOOCCURWHENAPARTICULARSTRESSLEVELHASBEENREACHEDANYYIELDCRITERIONISAPOSTULATEDMATHEMATICALEXPRESSIONOFTHESTRESSSTATESTHATWILLINDUCEYIELDINGORTHEONSETOFPLASTICDEFORMATIONONONEHAND,ITISRELATEDTOSTRESSSTATE,ONTHEOTHERHAND,ITISRELATEDTOMATERIALPROPERTIESYIELDSTRESSELASTICDEFORMATION0DDWORKHARDENINGRELOADINGUNLOADINGSUBSEQUENTYIELDSTRESSTOTALDEFORMATIONO31GENERALCONSIDERATIONSYIELDCRITERIACFIJWHERECISEITHERAMATERIALCONSTANTINTHECASEOFINITIALYIELDINGORAFUNCTIONOFTHEAMOUNTOFDEFORMATIONFORWORKHARDENINGMATERIALANYPOINTSALONGAWORKHARDENINGSTRESSSTRAINCURVEMAYBEREGARDEDASSUBSEQUENTYIELDPOINTSTHESTRESSESATTAINAVALUEWHICHEXCEEDSTHATREQUIREDFORELASTICDEFORMATIONANDTHEMATERIA