Fatigue and creep-fatigue crack growth in aviation turbine disk simulation models under variable amplitude loading

This study analyzes the simulation model configuration and its loading conditions in fatigue and subsequent crack growth tests. Following the simulation principles, a full-size 3D finite element analysis of a representative GTE turbine disc was performed. With the aim of reproducing the simulation model, the in-service critical zone of both the stress–strain state and damage accumulation is studied. Based on the parametric computations, the block type loading conditions of the simulation models are determined and verified. Experimental study of the surface crack growth rate in the simulation model under harmonic and block loading at elevated temperature is performed for the fatigue and creep-fatigue interaction conditions. To interpret the experimental data, we calculate the nonlinear stress intensity factor distributions along the semielliptical crack front for flaws growing on the inner surface of the hole in the simulation model using numerical procedures. It is found that in terms of the nonlinear fracture resistance parameters, the sections of the fatigue fracture diagrams form one common curve representing the previous and subsequent increasing stages of block loading in pure fatigue and creep-fatigue interaction loading conditions. The possibility of using the proposed simulation model, tested under variable amplitude loading, to assess the structural integrity of GTE turbine disks is discussed.