Strain accumulation during microstructurally small fatigue crack propagation in bcc Fe-Cr ferritic stainless steel

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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
9
51-59
Series
Acta Materialia, Volume 144
Abstract
Strain accumulation was studied by digital image correlation technique (DIC) during microstructurally small fatigue crack propagation in polycrystalline 18%Cr ferritic stainless steel. Load-controlled fatigue testing was performed with R-ratio of 0.1 and frequency 10 Hz. The maximum applied stress was well below the yield stress of the studied material. The effect of the observed strain field on crack growth rate variation is discussed. Fracture surfaces were studied by scanning electron microscopy (SEM) evidencing the connection between the mechanism of the fatigue crack growth, accumulated strain and crack growth rate. Detailed study of fracture surface morphology was carried out by atomic force microscopy (AFM). Results indicate two processes of material damage accumulation and failure during cyclic loading: 1) local shear strain zones form successively ahead of the crack tip, and 2) fatigue crack growth occurs by both single- and multiple-slip mechanisms. The place and intensity of shear strain localization zones vary during the crack growth that is related closely to the local variation of crack growth rate.
Description
Keywords
bcc crystal structure, Digital image correlation, Microstructurally small fatigue crack, Shear strain localization
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Citation
Malitckii , E , Remes , H , Lehto , P , Yagodzinskyy , Y , Bossuyt , S & Hänninen , H 2018 , ' Strain accumulation during microstructurally small fatigue crack propagation in bcc Fe-Cr ferritic stainless steel ' , Acta Materialia , vol. 144 , pp. 51-59 . https://doi.org/10.1016/j.actamat.2017.10.038