Digital-image-correlation observation of cyclic plastic strain field during the damage-accumulation mode of fatigue crack propagation under pure cyclic mode II loading for cold-rolled SUS430 steel

Fatigue cracks propagate intermittently by the cyclic initiation and coalescence of voids in front of the fatigue crack tip during fatigue crack propagation in the damage accumulation mode. In this study, digital image correlation is used to measure the evolution of the measured plastic strain distr...

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Bibliographic Details
Published in:Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2022-06, Vol.845, p.143246, Article 143246
Main Authors: Hamada, Shigeru, Araki, Yamato, Noguchi, Hiroshi
Format: Article
Language:English
Subjects:
Cold-rolled steel
Crack initiation
Crack propagation
Crack tips
Cyclic loads
Cyclic mode II loading
Cyclic strain localization
Damage accumulation
Damage accumulation mode
Digital imaging
Evolution
Fatigue crack propagation
Fatigue cracks
Fatigue failure
Ferritic stainless steels
Metal fatigue
Plastic deformation
Plastic strain
Propagation
Propagation modes
Strain concentration
Strain distribution
Strain localization
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Summary:Fatigue cracks propagate intermittently by the cyclic initiation and coalescence of voids in front of the fatigue crack tip during fatigue crack propagation in the damage accumulation mode. In this study, digital image correlation is used to measure the evolution of the measured plastic strain distribution near the crack tip with loading and cyclic loading during one cycle. The evolution is estimated based on strain distribution measurements results and mechanical considerations. The strain is set at the unloading point because results indicate that the crack propagated in the region where the experimental shear plastic strain is the maximum in the first quarter cycle (at the first maximum load); the measured plastic strain is almost constant in the region where the crack propagates, and the crack is initiated by a subsequent cyclic strain localization and coalescence with the main crack. This study clarified the damage accumulation mode fatigue crack propagation mechanism with the measured strain behavior, and presents a method to use continuum plastic strain at the crack tip as a mechanical driving force for this mode.
ISSN:0921-5093
1873-4936
DOI:10.1016/j.msea.2022.143246