FATIGUE CRACK PROPAGATION BEHAVIOUR UNDER VARIABLE AMPLITUDE LOADING IN THE NEAR-THRESHOLD REGION OF A HIGH-STRENGTH LOW-ALLOY STEEL |
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| Authors: | G. Hé naff,,J. Petit, B. Journet |
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| Affiliation: | Laboratoire de Mécanique et de Physique des Matériaux, URA CNRS 863, ENSMA, 20 rue Guillaume VII, 86 034 Poitiers Cedex;Aérospatiale, Centre Commun de Recherches Louis Blériot, Département Matériaux, 12 rue Pasteur, B.P. 76, 92 152 Suresnes Cedex, France |
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| Abstract: | The near-threshold behaviour of a high-strength low-alloy steel used in helicopter rotors under variable amplitude loading is investigated in ambient air and in vacuum. Strong sequence effects occur, in particular a high decrease in crack growth rates after overloads of 40% on maximum load while keeping the amplitude constant. A detailed study of the retardation phenomenon due to the overloads provides an explanation for the different behaviour observed in air and in vacuum and has laid the basis for a method of predicting crack propagation under helicopter loading spectra. |
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