Prediction of crack growth from bolt holes in a disc

Fatigue crack growth from tie bolt holes in a representative gas turbine compressor disc is analysed using a weight function method and a strip-yield crack closure model. The study emphasis is placed on the effect of biaxial loading and the bolt hole plastic zone on the fatigue crack growth from the bolt hole when the disc is subjected to cyclic rotation speed. A solution of the ratio of the stress intensity factors under biaxial loading to those under uniaxial loading for a crack entirely or partially embraced by the bolt hole plastic zone is obtained. The crack propagation rate predicted by the modified crack growth model is found to correlate better with the experimental data measured in the spin rig test than that predicted by the conventional model which simply ignores the biaxial load and the bolt hole plastic zone effect.