SYMPOSIA PAPER Published: 01 January 1985
STP36224S

Growth of Fatigue Cracks Under Combined Mode I and Mode II Loads

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Although the majority of fatigue crack propagation studies have been concerned with pure Mode I loading situations, in practice many cracks in components may initially extend by fatigue under a combination of all three crack growth modes, and this initial period may predominate during the fatigue lifetime. In this paper, the threshold and growth behavior of cracks under various combinations of Mode I and Mode II crack tip displacements are studied, showing the effect of the T-stress in the biaxial specimen. Four materials (AISI 316 stainless steel, DTD 5120 aluminium alloy, Ti-6A1-4V, and 1Cr-Mo-V steel) have been tested. Two different experimental procedures, four-point bending and biaxial loading of a plate, are employed.

An expression is derived for fatigue crack growth under combined mode load conditions relating growth to crack-tip reversed plastic deformation, which depends on the Mode I and Mode II crack-tip stress-intensity factors and also the T-stress. A secondary but important factor is the fracture ductility of the material around the crack tip, which itself is a function of biaxial stress state.

Author Information

Hua, G
Institute of Mechanics, Academia Sinica, Beijing, China
Alagok, N
Middle East Technical University, Ankara, Turkey
Brown, MW
University of Sheffield, Sheffield, U.K.
Miller, KJ
University of Sheffield, Sheffield, U.K.
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Details
Developed by Committee: E08
Pages: 184–202
DOI: 10.1520/STP36224S
ISBN-EB: 978-0-8031-4921-2
ISBN-13: 978-0-8031-0444-0