PSI - Issue 35

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Martin Ferreira Fernandes et al. / Procedia Structural Integrity 35 (2022) 141–149 Martin Ferreira Fernandes et al. / Structural Integrity Procedia 00 (2021) 000 – 000

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Fig. 9. Fracture surface of dwell- fatigue test at 950 MPa (18630 cycles). (a) Overview and details of regions (b) “A”, (b) “B” and (d) “C”.

4. Conclusions The dwell-fatigue data indicated that Ti-6Al-4V alloy is dwell sensitive at room temperature since a significant dwell-life debit was observed for all stress levels tested. The dwell-life debit was more pronounced for higher stress levels (i.e., 1000 MPa and 975 MPa) than the lower stress level (i.e., 950 MPa). The dwell-fatigue life debits for dwell periods of 10 s at 1000 MPa, 975 MPa, and 950 MPa were 10.2, 10.0, and 4.5, respectively. The results suggest that the dwell sensitivity of Ti-6Al-4V alloy increases at high-stress levels. A significant plastic strain accumulation occurred during the dwell periods for the Ti-6Al-4V alloy during the first dwell-fatigue cycles. The dwell periods changed the fracture surface morphology from typical fatigue to ductile fracture at high-stress levels. The morphology of dwell-fatigue fractures combined aspects of ductile with fatigue fractures. Acknowledgements This work was supported by Sao Paulo Research Foundation, FAPESP (Grant Number 2019/02125-1). References Billot, T., Villechaise, P., Jouiad, M., Mendez, J., 2010. Creep-fatigue behavior at high temperature of a UDIMET 720 nickel-base superalloy. International Journal of Fatigue 32, 824–829. Cuddihy, M. A., Stapleton, A., Williams, S., Dunne, F.P.E., 2017. On cold dwell facet fatigue in titanium alloy aero-engine components. International Journal of Fatigue 97, 177–189. Everaerts, J., Gontcharov, D., Verlinden, B., Wevers, M., 2017. The influence of load holds on the fatigue behaviour of drawn Ti-6Al-4V wires. International Journal of Fatigue 98, 203–211. Fernandes, M. F., Santos, J. R. M., Velloso, V. M. O., Voorwald, H. J. C., 2020. AISI 4140 Steel Fatigue Performance: Cd Replacement by Electroplated Zn-Ni Alloy Coating. Journal of Materials Engineering and Performance 29, 1567–1578. Ghonem, H., 2010. Microstructure and fatigue crack growth mechanisms in high temperature titanium alloys. International Journal of Fatigue 32, 1448–1460. Goswami, T.; Hänninen, H., 2001. Dwell effects on high temperature fatigue behavior Part I. Materials and Design 22, 199–215. Joseph, S., Joseph, K., Lindley, T.C., Dye, D., 2020. The role of dwell hold on the dislocation mechanisms of fatigue in a near alpha titanium alloy. International Journal of Plasticity 131, 102743. Lavogiez, C.; Hémery, S.; Villechaise, P., 2020. Analysis of deformation mechanisms operating under fatigue and dwell- fatigue loadings in an α / β titanium alloy. International Journal of Fatigue 131, 105341. Lefranc, P., Doquet, V., Gerland, M., Sarrazin-Baudoux, C., 2008. Nucleation of cracks from shear-induced cavities in an α/β titanium alloy in fatigue, room-temperature creep and dwell-fatigue. Acta Materialia 56, 4450–4457. Sinha, V., Mills, M. J., Williams, J. C., 2004. Understanding the Contributions of Normal-Fatigue and Static Loading to the Dwell Fatigue in a Near-Alpha Titanium Alloy. Metallurgical and Materials Transactions A 35, 3141–3148. Xi, G., Lei, J., Qiu, J., Ma, Y., Yang, R., 2020. A semi-quantitative explanation of the cold dwell effect in titanium alloys. Materials and Design 194, 108909.