Effects of microstructure and crystallography on crack path and intrinsic resistance to shear-mode fatigue crack growth
DOI:
https://doi.org/10.3221/IGF-ESIS.34.15Keywords:
mode II and mode III cracksAbstract
The paper focuses on the effective resistance and the near-threshold growth mechanisms in the
ferritic-pearlitic and the pure pearlitic steel. The influence of microstructure on the shear-mode fatigue crack
growth is divided here into two factors: the crystal lattice type and the presence of different phases.
Experiments were done on ferritic-pearlitic steel and pearlitic steel using three different specimens, for which
the effective mode II and mode III threshold values were measured and fracture surfaces were reconstructed in
three dimensions using stereophotogrammetry in scanning electron microscope. The ferritic-pearlitic and
pearlitic steels showed a much different behaviour of modes II and III cracks than that of the ARMCO iron.
Both the deflection angle and the mode II threshold were much higher and comparable to the austenitic steel.
Mechanism of shear-mode crack behaviour in the ARMCO iron, titanium and nickel were described by the
model of emission of dislocations from the crack tip under a dominant mode II loading. In other tested
materials the cracks propagated under a dominance of the local mode I. In the ferritic-pearlitic and pearlitic
steels, the reason for such behaviour was the presence of the secondary-phase particles (cementite lamellas),
unlike in the previously austenitic steel, where the fcc structure and the low stacking fault energy were the main
factors. A criterion for mode I deflection from the mode II crack-tip loading, which uses values of the effective
mode I and mode II thresholds, was in agreement with fractographical observations.
Downloads
Downloads
Published
Issue
Section
Categories
License
Copyright
Authors are allowed to retain both the copyright and the publishing rights of their articles without restrictions.
Open Access Statement
Frattura ed Integrità Strutturale (Fracture and Structural Integrity, F&SI) is an open-access journal which means that all content is freely available without charge to the user or his/her institution. Users are allowed to read, download, copy, distribute, print, search, or link to the full texts of the articles in this journal without asking prior permission from the publisher or the author. This is in accordance with the DOAI definition of open access.
F&SI operates under the Creative Commons Licence Attribution 4.0 International (CC-BY 4.0). This allows to copy and redistribute the material in any medium or format, to remix, transform and build upon the material for any purpose, even commercially, but giving appropriate credit and providing a link to the license and indicating if changes were made.