PSI - Issue 54

Mihaela Iordachescu et al. / Procedia Structural Integrity 54 (2024) 52–58 Mihaela Iordachescu et. al / Structural Integrity Procedia 00 (2023) 000–000

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and the specimen fails. Hydrogen uptake from FIP medium is not enough to produce a severe assisted cracking process until the barriers restraining plastic strain at the crack tip vanish. This suggests that some plasticity based, damage micro-mechanism operates in the assisted cracking of the analyzed steel. 5. Conclusions The slow strain rate tensile tests carried out in a medium with a high embrittlement capacity on previously damaged specimens reveal the sensitivity of the high-strength lath martensite steel bars to hydrogen embrittlement, whose action consists of extending pre-existing damage in two stages of assisted cracking: one of initiation and the other of propagation. The transition from one stage to another occurs at the end of the SSY regime and the resistance that the steel opposes to cracking is severely reduced in the propagation phase. However, the steel embrittlement by hydrogen uptake remains localized at the crack front and is insufficient to cause the brittle fracture before the plastic collapse of the resistant ligament. The damage micro-mechanism producing this behavior is the detachment of the martensitic packages through their boundaries, limited in the initiation phase to those belonging to previous austenitic grains. The damage tolerance behavior of the studied steel is highly satisfactory, as crack size causing failure under a given load level is similar to the required one for plastic collapse of the resistant ligament. However, assisted cracking seriously worsens this behavior because crack growth occurs with no load increase from the level of crack initiation. This load level roughly coincides with the one that determines the end of the small scale yielding regime for the pre-existing crack. Acknowledgements The authors gratefully acknowledge the grants RTI-2018-097221-B-I00, PRE-2019-088263 and UP2021-035 funded by MCIN/AEI/10.13039/501100011033 and respectively by “ERDF A Way of Making Europe”, “ESF Investing in Your Future” and “Next Generation EU/PRTR”. References De Abreu, M., Iordachescu M., Valiente A., 2018. On hydrogen induced damage in cold drawn lean-duplex wires, Eng Fail Anal 91, 516-526. E399. 2022. Standard Test Method for Linear-Elastic Plane-Strain Fracture Toughness of Metallic Materials, ASTM. E722: 2003. Standard Specification for Uncoated-High Strength Steel Bars for Prestressing Concrete, ASTM. Iordachescu, D., Blasco, M., Lopez, R., Cuesta, A., Iordachescu, M., Ocaña, J.L., 2011. Recent achievements and trends in laser welding of thin plates. Journal of Optoelectronics and Advanced Materials, 13(8), 981-985. Iordachescu, M., Ruiz-Hervias, J., Iordachescu, D., Scutelnicu, E., Porro, J.A., 2008. Residual stress analysis of friction stir processed AA6061, Welding in the World, 52(Spec. Iss.), 753-757. Iordachescu, M., Pérez-Guerrero, M., Valiente, A., Elices, M., 2018. Environmental effects on large diameter high-strength rods for structural applications, Engineering Failure Analysis, 83, 230-238. Iordachescu, M., Santos, P., Valiente A., de Abreu, M., 2022. Stress corrosion assisted collapse in flat tensile specimens of high-strength structural steel, Procedia Structal Integrity, 42, 602-607. Morris J. W., 2011. On the Ductile-Brittle Transition in Lath Martensitic Steel, ISIJ International 51(10), 1569–1575. Morris, J.W., Kinney, C., Pytlewski, K., Adachi, Y., 2013. Microstructure and cleavage in lath martensitic steels. Sci. Technol. Adv. Mater. 14, 014208 (9pp), doi:10.1088/1468-6996/14/1/014208. prEN10138-4: Prestressing steels-Part 4: Bars, CEN 2005. Tada, H., Paris P., Irwin, G.R., The stress analysis of cracks Handbook, 3th ed, ASME Press, New York, 2000. UNE-EN ISO 15630-3 Steel for the reinforcement and prestressing of concrete — Test methods — Part 3: Prestressing steel, ISO, 2019. Valiente, A., Pérez-Guerrero, M., Iordachescu, M., 2016. New testing method for assessing the cracking sensitivity of stressed tendon rods in aggressive environments, Engineering Failure Analysis , 68, 244-253.