21st Congress of International Council of the Aeronautical Sciences, Melbourne, Australia, 13-18 September, 1998
Paper ICAS-98-5.7.2

CRACK GROWTH PREDICTION USING AN ANALYTICAL CRACK CLOSURE MODEL FOR A SEMI-ELLIPTIC SURFACE FLAW LOADED IN COMBINED TENSION AND OUT OF PLANE BENDING

Walker K. F.
Aeronautical and Maritime Research Lab., Australia

Keywords: crack growth prediction, analytical crack closure model, semi-elliptic surface, flaw, tension, out of plane bending

The plasticity induced analytical crack closure model provides a scientifically based approach to predicting fatigue crack growth behaviour under spectrum loading. Stress ratio and load interaction effects are known to occur, and the crack closure concept has been demonstrated to account for these and therefore works well for through cracks in thin sheet materials. This paper details the application of the analytical crack closure model approach to predict the crack growth for a semi-elliptic surface flaw in a non-uniform stress field. This is a problem which hitherto has been analysed using standard LEFM and empirical load interaction models such as Wheeler and Willenborg. The analytical crack closure model has been found to perform better than the empirical models for the simpler through thickness flaw case in a uniform stress field and since it has a more sound theoretical base it was considered that it should also perform better for a more complex case. Basic material data from standard compact tension and centre crack specimen tests was utilised. The resulting prediction compares well with test results.

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