A New Ductility Criterion for Fatigue-Creep Life Prediction of High Temperature Components

Abstract

Ductility exhausted during fatigue-creep interaction loading is focused on predicting fatigue-creep life for high temperature components. Based on the exhaustion of static toughness and dissipation of total strain energy during fatigue failure, a new ductility criterion for fatigue-creep life prediction is presented in an attempt to develop ductility based life prediction approaches for general use in isothermal and thermo-mechanical fatigue loading. In this criterion, the fatigue toughness to failure of materials was established and the development of fatigue toughness to fatigue-creep failure analysis is presented. The accuracy of the proposed criterion was verified by comparison between model approximation and experimental results of 1.25Cr0.5Mo steel and GH4133 superalloy under different loading conditions. The comparison shows promising agreement, thus validating the capability of the proposed criterion to produce accurate fatigue-creep life prediction. Nomenclature ,, AC = material-specific constants E = Young's modulus p E = viscosity-based parameter n = cyclic strain hardening exponent f N = number of cycles to failure f W = energy required to facilitate fatigue failure t W  = total strain energy density lim W  = elastic strain energy density at the fatigue limit of the material p W  = plastic strain energy density e W   = tensile elastic strain energy density m T = fatigue toughness  = strain rate d  = dynamic viscosity t   = total strain range AIAA SciTech 2 e   , p   = elastic strain range and plastic strain range max  , min  = maximum and minimum stress sat   = saturated stress range   = stress range