Prediction of crack growth in a nickel-based superalloy under fatigue-oxidation conditions

摘要: Prediction of oxidation-assisted crack growth has been carried out for a nickel-based superalloy at elevated temperature based on finite element analyses oxygen diffusion, coupled with viscoplastic deformation, near fatigue tip. The material constitutive behaviour, implemented in the code ABAQUS via user-defined subroutine (UMAT), was described by unified model non-linear kinematic and isotropic hardening rules. Diffusion assumed to be controlled two parameters, diffusivity deformation-assisted mobility. Low frequencies superimposed hold periods peak loads significantly enhanced concentration Evaluations near-tip deformation were performed, which led construction failure envelop consideration both accumulated inelastic strain then utilised predict rates compact tension (CT) specimen under fatigue-oxidation conditions selected loading ranges, dwell periods. predictions from compared well experimental results triangular waveforms, marked improvements achieved over those predicted alone. also agree slow-fast but not fast-slow waveforms where effect oxidation is much reduced.