PREDICTION OF CREEP FAILURE IN AEROENGINE MATERIALS UNDER MULTIAXIAL STRESS STATES

The creep and creep rupture behaviour of two, significantly different, aeroengine materials, namely a nickel-base superalloy at 700 degrees C and a high temperature titanium alloy at 650 degrees C, were studied . Experimental creep tests were conducted on uniaxial specimens and ax isymmetric notched bars under constant tensile loads conditions. From the uniaxial creep test results, a creep continuum damage model was es tablished for each of the materials. The skeletal point stress approac h was used to obtain the approximate creep rupture stress criterion in the multi-axial generalization of the creep continuum damage models. This approximation was cross-checked using axisymmetric Finite Element (FE) analyses in a trial and error procedure. Multi-axial creep conti nuum damage models were then used in further FE creep analyses to pred ict the creep rupture times in specimens subjected to different tensil e loads. The FE predictions of the rupture times in these notched spec imens were found to be in good agreement with the experimental results for the nickel-base superalloy (Waspaloy) at 700 degrees C and the ti tanium alloy (IMI834) at 650 degrees C.