PSI - Issue 7

Stanislav Žák et al. / Procedia Structural Integrity 7 (2017) 254 – 261

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Stanislav Žák et al. / Structural Integrity Procedia 00 (201 7 ) 000 – 000

4. Conclusions The geometrically induced shielding effects of micro-tortuous crack fronts loaded in the remote mode II were theoretically investigated. Besides the numerical simulations based on the finite element method and applied to real-like tortuous crack fronts, an analytical approach utilizing the tensor transformation related to a simplified one-facet model of these crack-fronts with equal linear roughness was also employed. The results revealed that both approaches give shielding effects comparable within a small difference of 4%. When measuring the linear roughness of the fatigue precrack fronts in ARMCO iron specimens, the experimentally determined values of effective mode II threshold K IIth, eff can be corrected with respect to the shielding effect. A rough estimation of this effect indicates that this correction could bring the experimental value of the fatigue threshold very close to that theoretically predicted by multiscale models. Acknowledgements The authors acknowledge the financial support of this work by the Czech Science Foundation (GACR) in the fra me of the Project No. 17 -15716Y. References Anderson, T.L., 1995. Fracture mechanics: Fundamentals and applications, 2nd ed. ed. CRC Press, Boca Raton (Florida). Ansys Inc., 2017. Ansys R17.2 help (manual). Beretta, S., Foletti, S., Valiullin, K., 2011. Fatigue strength for small shallow defects/cracks in torsion. Int. J. Fatigue 33, 287–299. Cotterell, B., Rice, J.R., 1980. Slightly curved or kinked cracks. Int. J. Fract. 16, 155–169. Faber, K.T., Evans, A.G., 1983. Crack deflection processes-I. Theory. Acta Metall. 31, 565–576. Gross, T.S., Mendelsohn, D.A., 1989. Mod e I Stress Intensity Factors Induced by Fracture Surface Roughness under Pure Mode III Loading : Application to the Effect of Loading Modes on Stress Corrosion Crack Growth. Metall. Trans. A 20. Hassan, A.R., Radhi, S.H., 2013. Effect of the Crack Geometry and Notch on Stress Intensity Factors in Bonding of Materials. Acad. Res. Int. 4, 93–103. Horníková, J., Žák, S., Šandera, P., 2015. Numerical Fracture Analysis of Compact Tension Shear (CTS) Specimens with Tortuous Crack Fronts. Key Eng. Mater. 665, 77–80. Plank, R., Kuhn, G., 1999. Fatigue crack propagation under non-proportional mixed mode loading. Eng. Fract. Mech. 62, 203–229. Pokluda, J., Pippan, R., 2005. Can pure mode III fatigue loading contribute to crack propagation in metallic materials? Fatigue Fract. Eng. Mater. Struct. 28, 179–185. Pokluda, J., Pippan, R., Vojtek, T., Hohenwarter, A., 2014. Near -threshold behaviour of shear-mode fatigue cracks in metallic materials. Fatigue Fract. Eng. Mater. Struct. 37, 232–254. Pokluda, J., Šandera, P., 2010. Micromechanisms of Fracture and Fatigue, 1st ed, Engineering Materials and Processes. Springer London, London. Pokluda, J., Šandera, P., Horníková, J., 2004. Statistical approach to roughness -induced shielding effects. Fatigue Fract. Eng. Mater. Struct. 27, 141–157. Riemelmoser, F.O., Gumbsch, P., Pippan, R., 2001. Dislocation Modelling of Fatigue Cracks: An Overview. Mater. Trans. 42, 2–13. Richard, H.A., 1981. A new compact shear specimen. Int. J. Fract. 17, R105–R107. Richard, H.A., Fulland, M., Sander, M., 2005. Theoretical crack path prediction. Fatigue Fract. Eng. Mater. Struct. 28, 3–12. Sapora, A., Cornetti, P., Carpinteri, A., 2014. Analytical Stress Intensity Factors for cracks at blunted V-notches. Procedia Mater. Sci. 3, 738– 743. Vatne, I.R., Stukowski, A., Thaulow, C., Ostby, E., Marian, J., 2013. Three-dimensional crack initiation mechanisms in bcc-Fe under loading modes I, II and III. Mater. Sci. Eng. A 560, 306–314. Vojtek, T., Hohenwarter, A., Pippan, R., Pokluda, J., 2016. Experimental evidence of a common local mode II growth mechanism of fatigue cracks loaded in modes II, III and II+III in niobium and titanium. Int. J. Fatigue 92, 470–477. Vojtek, T., Pokluda, J., Šandera, P., Horníková, J., Hohenwarter, A., Pippan, R., 2015. Analysis of fatigue crack propagation under mixed mode II+III in ARMCO iron. Int. J. Fatigue 76, 47–52. Zerbst, U., Vormwald, M., Pippan, R., Ganser, H.-P., Sarrazin-Baudoux, C., Madia, M., 2016. About the fatigue crack propagation threshold of metals as a design criterion - A review. Eng. Fract. Mech. 153, 190–243. Zerres, P., Vormwald, M., 2014. Review of fatigue crack growth under non-proportional mixed-mode loading. Int. J. Fatigue 58, 75–83. Zhang, G.P., Wang, Z.G., 1997. Short fatigue crack growth under mixed mode loading in Ni3A1 alloy single crystals. Mater. Sci. Eng. 229, 129-136. Žák, S., Horníková, J., Šandera , P., 2017. Stress intensity factors for rough cracks loaded in mode II, Solid State Phenomena.