简介:ThispaperpresentstheparametricvariationalprincipleforPerzynamodelwhichisoneofthemainconstitutiverelationsofviscoplasticity.Theprinciple,bywhichthepotentialenergyfunctionisminimizedunderaconstrainedconditiontransformedbytheconstitutiverelationsofviscoplasticity,isfreefromtheboundofDrucker’spostulateofplasticflowandconsequentlysuitableforsolvingthenonassociatedplasticflowproblems.Furthermore,thepaperhasproventhepresentedprincipleanddiscussedthecreepproblem.