Complex Diagnostics of the State of Operated Elements of a Grab Reloader
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COMPLEX DIAGNOSTICS OF THE STATE OF OPERATED ELEMENTS OF A GRAB RELOADER P. О. Semenov1, 2 and V. М. Pustovyi1
UDC 621.875:539.4.01
We perform complex diagnostics of the technical state of steel structure of a grab reloader after operation for more than 40 yr by the methods of destructive and nondestructive testing. Fatigue cracks and mechanical defects caused by wear are detected on the shaped rolled products. By using the magnetic method with determination of the coercive force, we analyze the stress-strain states of various elements of the metal structure, which enables us to detect potentially hazardous zones. For these zones, we study, in particular by the fractographic analysis, the mechanical characteristics of strength, plasticity, and impact toughness and show that the degree of in-service degradation of the metal correlates with the estimates of its stress-strain state. Keywords: sea grab reloader, low-carbon steel, in-service degradation, diagnostics of the current state.
Introduction The in-service degradation of structural steels intended for long-term operation may lead to substantial deterioration of their brittle-fracture resistance [1–4]. Under cyclic loads and in the case of possible hydrogenation of the metal, the process of degradation is accelerated due to the development of dispersed microdefects in the volume of the metal [5–7]. The reloading equipment operating under the indicated conditions belongs to critical structures of the sea ports. This is why special attention is given to the diagnostics of the technical state of reloaders after exhaustion of their design service life [8–12]. As one of these reloaders, we can mention a grab reloader crane for bulk freights equipped with a grab with high load-bearing capacity and characterized by a high intensity of operation. Its metal structure is mainly formed by shaped sections made of low-carbon steel in the hot-rolled state. The design service life of this reloader in the case of operation under severe working conditions constitutes 20–25 yr for which the metal undergoes at least 106 loading cycles. The aim of the present work is to examine the technical state of the metal structure of a grab reloader after long-term operation with the help of a complex of destructive and nondestructive diagnostic methods. Methodical Aspects of Investigations The object of investigation is a grab reloader after operation under especially severe conditions for 40 yr. More precisely, our aim is to perform diagnostics of the elements of its steel structure. Thus, we detected macrodefects on the surfaces of rolled products, investigated the stress-strain state of various units of the metal 1 2
Odesa National Maritime University, Odesa, Ukraine.
Corresponding author; e-mail: [email protected].
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 56, No. 2, pp. 39–45, March–April, 2020. Original article submitted December 13, 2019. 1068-820X/20/5602–0181
© 2020
Springer Science+Business Media, LLC
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