Rationalisation of the Multiaxial Stress Rupture Behaviour of Components

摘要

High temperature industrial componentsinvariably experience complex thermal and mechanical loadinghistories. With regard to degradation and failure as a result ofcreep deformation and rupture mechanisms, design andremaining life procedures rely extensively on conventionaluniaxial creep tests as a source of material and temperaturespecific property data. Plant assessment often proceeds basedupon relatively simple calculations that invariably incorporatedistinct levels of conservatism to compensate for inherentuncertainties within the design route. An improvedunderstanding of the influences of component geometry andstress-state upon component creep rupture behaviour will reduceunnecessary conservatisms and potentially extend service lifetime.In the present paper these concepts are developed to reconcileobserved multiaxial stress rupture criteria inferred from testsutilising a range of testpiece geometries. Component ruptureunder complex loading conditions is seen to depend upon boththe materials response and the mechanical interaction betweenthe structure and the loading. These mechanical factorsinclude the component geometry and the evolution of stressduring creep life, in addition to the more commonly preferreddescriptors of applied stress and stress state. Consideration ofthese additional elements during the presentation of materialstress rupture response enables the true position of componentcreep rupture results to be determined in relation to uniaxial baseline data.