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INTERACTION OF OVERLOADS ON FATIGUE CRACK GROWTH FOR 40CrNi STEEL
Author(s) -
Yang Shuilong,
Li Hua
Publication year - 1991
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1111/j.1460-2695.1991.tb00724.x
Subject(s) - paris' law , structural engineering , crack closure , amplitude , materials science , fracture mechanics , wedge (geometry) , engineering , mathematics , physics , geometry , quantum mechanics
This work was designed to improve the general understanding of loading sequence effects on fatigue crack growth and lead to the development of improved methods for predicting crack propagation behaviour. Two loading histories were selected (1) a baseline amplitude with periodic overloads or underloads, and (2) several overloads without interactive effects. The specimen used was of a Wedge Opening Loading type and the material was a low alloy high strength steel, i.e. 4OCrNi. It was found that the Linear Summation of Damage (LSD) assumption could be applied in predicting fatigue crack growth rate (FCGR) under periodic overloads or underloads within the scatterband of the constant amplitude data obtained using an Alternating Current Potential Drop technique for measuring crack length for multiple specimens with several load amplitudes. A discrepancy existed between the FCGR predicted from LSD and the one actually measured during several hundreds of loading cycles immediately following every non‐interactive overload of the latter loading history although the overload ratio was the same as that of periodic overloading. The causes of this phenomenon are discussed.