PSI - Issue 41

Hryhoriy Nykyforchyn et al. / Procedia Structural Integrity 41 (2022) 326–332 Hryhoriy Nykyforchyn, Vitaliy Pustovyi, Olha Zvirko et al. / Structural Integrity Procedia 00 (2022) 000 – 000

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1. Introduction Hoisting and transporting equipment of various functional purposes (cranes, unloaders, railcar loaders, stackers etc.) is an important component of seaport infrastructure. This equipment in turn consists of certain units such as a cabin, counterweights, lifting mechanisms, handling grabs and other facilities. However, the most metal-consuming part is the load-bearing structures, made mainly from rolled and shaped carbon steel sheets. They should meet appropriate requirements for the mechanical properties of the metal which ensure their serviceability during the planned long-term operation under a combined action of cyclic operational stresses and corrosive marine environment. It should be taken into account that the mechanical properties of load-bearing structures of handling equipment are subjected to operational degradation, as shown by Kharchenko et al. (2014), Nemchuk et al. (2019). Its peculiarity consists in a sharp decrease in the resistance to brittle fracture determined by the Charpy testing. This corresponds to general regularities of the degradation of operated steels for various purposes, primarily pipelines, which have been comprehensively discussed by Nykyforchyn et al. (2009, 2021), Gredil (2009), Filippov et al. (2013), Maruschak et al. (2014), Okipnyi et al. (2020), Zvirko (2022) and others. Besides impact strength, Nykyforchyn et al. (2009, 2021) showed an essential drop of the fracture toughness characteristics (determined usually by the J-integral method for ductile steels). A low resistance to crack propagation increases the risk of abrupt failures of metal structures including hoisting and transporting equipment. It is important to note that this equipment is typically made of low-strength steels, and their strength change insignificantly during operation. Thus, long-term operation of such steels causes an untypical combination of both low strength and brittle fracture resistance. Tang et al. (2019) proposed a systematic approach to analyse the strength of the main structural component in ship-to-shore cranes under dynamic load. The potential influence of time-dependent aging and deterioration is also considered at developing fragility models for port structures described by Maniglio et al. (2021). At the same time, Pustovoi et al. (2015) noted that in-laboratory cyclic loading similar as long-term operation of portal cranes caused a decrease in both brittle fracture and corrosion resistance of steels. Fatigue is commonly the main reason of failure of port steel cranes, as demonstrated in numerous issues by Wang et al. (2013), Nemchuk et al. (2019) and others. It is also known from Ohaeri et al. (2018), Nykyforchyn et al. (2020), Zvirko (2022) that hydrogenation intensifies the operational degradation of steels, mainly due to the facilitation of microdamage development. Hredil (2011) pointed out that this microdamage is dissipated in the bulk of the metal and results in a decrease in the resistance to brittle fracture. Thus, the role of hydrogen in the implementation of low-energy fracture of operates steels is twofold: on the one hand, the intensification of the operational degradation, and on the other one the well known hydrogen-assisted fracture. Hredil and Tsyrulnyk (2010) established that the source of hydrogen is most often the electrochemical interaction of the metal with a corrosive environment accompanied by the evolution of atomic hydrogen which can penetrate deep inside the metal as shown by Domżalicki et al. (2008), Mohtadi-Bonab et al. (2013). Concerning hoisting and transporting equipment of seaports, Zvirko (2017) emphasized the probability of steel hydrogenation from the marine atmosphere. Domżalicki et al. (2008) noted that for marine structures, especially embedded ones, the hydrogen uptake was higher than that observed in the laboratory tests, which also highlights the need to take into account the hydrogen impact on the serviceability of seaport installations. Since metal structures of seaports are usually made of the steel produced by rolling, it is expected the impact of the steel texture on its mechanical properties. Mohtadi-Bonab and Ghesmati-Kucheki (2019) discussed the crystallographic texture and the grain boundary distribution as the factors effecting hydrogen-induced cracking in rolled steels. Lesiuk at al. (2019), Marushchak et al. (2019), Nemchuk and Krechkovska (2019) showed that specimens cut transversally to the rolling direction is more suitable for the estimation of the operational degradation of steels, and Nykyforchyn et al. (2022) proposed a methodology for the mechanical testing of custom transversal specimens. In this paper, the manifestation of two important factors in the operational degradation of carbon steels, namely, cyclic loading and marine atmosphere, have been analysed.