TY - JOUR AU - Pokluda, J. AU - Vojtek, T. AU - Hohenwarter, A. AU - Pippan, R. PY - 2015/09/28 Y2 - 2024/03/29 TI - Effects of microstructure and crystallography on crack path and intrinsic resistance to shear-mode fatigue crack growth JF - Frattura ed Integrità Strutturale JA - Fra&IntStrut VL - 9 IS - 34 SE - Miscellanea DO - 10.3221/IGF-ESIS.34.15 UR - https://www.fracturae.com/index.php/fis/article/view/1566 SP - AB - <p>The paper focuses on the effective resistance and the near-threshold growth mechanisms in the<br>ferritic-pearlitic and the pure pearlitic steel. The influence of microstructure on the shear-mode fatigue crack<br>growth is divided here into two factors: the crystal lattice type and the presence of different phases.<br>Experiments were done on ferritic-pearlitic steel and pearlitic steel using three different specimens, for which<br>the effective mode II and mode III threshold values were measured and fracture surfaces were reconstructed in<br>three dimensions using stereophotogrammetry in scanning electron microscope. The ferritic-pearlitic and<br>pearlitic steels showed a much different behaviour of modes II and III cracks than that of the ARMCO iron.<br>Both the deflection angle and the mode II threshold were much higher and comparable to the austenitic steel.<br>Mechanism of shear-mode crack behaviour in the ARMCO iron, titanium and nickel were described by the<br>model of emission of dislocations from the crack tip under a dominant mode II loading. In other tested<br>materials the cracks propagated under a dominance of the local mode I. In the ferritic-pearlitic and pearlitic<br>steels, the reason for such behaviour was the presence of the secondary-phase particles (cementite lamellas),<br>unlike in the previously austenitic steel, where the fcc structure and the low stacking fault energy were the main<br>factors. A criterion for mode I deflection from the mode II crack-tip loading, which uses values of the effective<br>mode I and mode II thresholds, was in agreement with fractographical observations.</p> ER -