PSI - Issue 59

Jesús Toribio et al. / Procedia Structural Integrity 59 (2024) 90–97 Jesús Toribio / Procedia Structural Integrit y 00 (2024) 000 – 000

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5. Conclusions A fracture mechanics approach to hydrogen-assisted micro-damage (HAMD) in pearlitic steel is presented, in such a manner that the tearing topography surface (TTS) zone is modeled as a macroscopic post-crack prolonging (extending) the original fatigue pre-crack and involving linear elastic fracture mechanics (LEFM) principles. Following the afore-said approach, the critical parameter for hydrogen assisted cracking (HAC) is the critical stress intensity factor (SIF) K H in a hydrogen environment, i.e., that intensity level determining the change from sub critical TTS to critical cleavage in the crack growth kinetics (CGK) curve d a /d t - K . When a high fatigue pre-cracking load is applied, the value of the critical SIF K H in a hydrogenating environment is higher due to compressive residual stresses in the vicinity of the crack tip ( overload retardation effect ), so steels that are subjected to heavier pre-cracking exhibit a higher resistance to HE and hydrogen damage. TTS zones with the highest crack aspect ratio ( a H /b H near to unity, i.e., TTS zone geometries resembling a semicircular shape) have lowest value of K H , so it can be thought that hydrogen effect is higher in such a quasi circular TTS regions with a high aspect ratio. Acknowledgements The author wishes to kindly and sincerely acknowledge the continuous and long-standing financial support to his scientific research in the field of fracture & structural integrity provided by the following Spanish Institutions: Ministry for Science and Technology (MICYT; Grant MAT2002-01831), Ministry for Education and Science (MEC; Grant BIA2005-08965), Ministry for Science and Innovation (MICINN; Grant BIA2008-06810), Ministry for Economy and Competitiveness (MINECO; Grant BIA2011- 27870) and Junta de Castilla y León (JCyL; Grants SA067A05, SA111A07, SA039A08 and SA132G18). In addition, acknowledgement is given to two companies: E MESA T REFILERÍA (La Coruña. Spain) and T REFILERÍAS Q UIJANO (Los Corrales de Buelna, Santander, Spain) for providing the pearlitic steel wires to be used in the experimental programme. References Athanassiadis, A., Boissenot, J.M., Brevet, P., Francois, D., Raharinaivo, A., 1981. Linear elastic fracture mechanics computations of cracked cylindrical tensioned bodies. International Journal of Fracture 17, 553-566. Caspers, M., Mattheck, C., Munz, D., 1986. Fatigue crack propagation in cylindrical bars. Materialwissenschaft und Werkstofftechnik 17, 327 333. Shin, C. S., Cai, C. Q., 2004. Experimental and finite element analyses on stress intensity factors of an elliptical surface crack in a circular shaft under tension and bending. International Journal of Fracture 129, 239-264. Toribio, J., Álvarez, N., González, B., Matos, J.C., 2009. A critical review of stress intensity factor solutions for surface cracks in round bars subjected to tension loading. Engineering Failure Analysis 16, 794-809. Toribio, J., Lancha, A.M., 1993. Effect of cold drawing on susceptibility to hydrogen embrittlement of prestressing steell. Materials and Structures 26, 30-37. Toribio, J., Lancha, A.M., 1996. Effect of cold drawing on environmentally assisted cracking of cold-drawn steel. Journal of Materials Science 31, 6015-6024. Toribio, J., Lancha, A.M., Elices, M., 1991a. Characteristics of the new tearing topography surface. Scripta Metallurgica et Materialia 25, 2239-2244. Toribio, J., Lancha, A.M., Elices, M., 1991b. Hydrogen embrittlement of pearlitic steels: Phenomenological study on notched and precracked specimens. Corrosion 47, 781-791. Toribio, J., Lancha, A.M., Elices, M., 1992. The tearing topography surface as the zone associated with hydrogen embrittlement processes in pearlitic steel. Metallurgical Transactions 23A, 1573-1584.