21st Congress of International Council of the Aeronautical Sciences, Melbourne, Australia, 13-18 September, 1998
Paper ICAS-98-5.2.3

PREDICTION OF FATIGUE CRACK GROWTH FROM BOLT HOLES IN A TITANIUM DISC

Zhuang W. Z., Stocks G. J., Wang C. H.
DSTO, Australia

Keywords: fatigue crack, bolt holes, titanium disc

The growth of a comer crack emanating from tie bolt holes in a representative gas turbine compressor disc is analysed using a crack closure model. Experimental observations showed that a comer crack first initiated at the hole edge and then propagated to become a through crack, whose growth lead ultimately to the failure of the disc. It is found that when the influence of the biaxial stress is ignored, viz, the problem is treated as a comer crack growing from a hole under uniaxial loading, much shorter fatigue life is predicted. To account for the biaxial loading effect, it is .assumed that the ratio of the stress intensity factors under biaxial loading and uniaxial loading is the same for a comer crack and a through crack, for a given crack length. This allows the influence of the biaxial loading to be readily determined using the through crack solution, which can be obtained using a two dimension weight function method. Predictions using the improved stress intensity factor appear to correlate reasonably well with the experimental results obtained from spin rig tests.

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