Influence of crack tip plasticity on fatigue behaviour of laser stake-welded T-joints made of thin plates

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2018-02-01
Major/Subject
Mcode
Degree programme
Language
en
Pages
12
112-123
Series
International Journal of Mechanical Sciences, Volume 136
Abstract
The paper investigates the crack tip plasticity of laser stake-welded T-joints when the thickness is varied. For thin joints, mixed-mode condition is dominant, and the Minimum Plastic Zone Radius (MPZR) criterion is employed to estimate the crack initiation direction. Subsequently, the same first-order plastic zone size ry as defined by Irwin is kept equal for the selected load levels in the MPZR direction, and finite element (FE) analyses are carried out to investigate the stress gradient over ry comparing different thicknesses. The results allow us to explain why the fatigue slope m is different for thin and thick joints. Moreover, a new method is proposed that permits the number of cycles to failure of thin joints to be derived directly from the fatigue curve of thick joints, employing an effective J-integral. The results prove that the method is able to give an estimation of the number of cycles to failure for thin joints with acceptable error.
Description
Keywords
Crack, Fatigue assessment, Laser stake-welds, Plastic zone, Slope of fatigue curve
Other note
Citation
Gallo , P , Guglielmo , M , Romanoff , J & Remes , H 2018 , ' Influence of crack tip plasticity on fatigue behaviour of laser stake-welded T-joints made of thin plates ' , International Journal of Mechanical Sciences , vol. 136 , pp. 112-123 . https://doi.org/10.1016/j.ijmecsci.2017.12.011