PSI - Issue 28

NikolayA. Makhutov et al. / Procedia Structural Integrity 28 (2020) 1378–1391 N.Makhutov, M.Gadenin, D.Reznikov / Structural Integrity Procedia 00 (2019) 000–000

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number of loading cycles, τ is the duration of exposure to loading, t is the temperature, S are parameters of resistance of materials and structural components to external and internal impacts. Limit states of a technical facility during its life may be reached at different rates and along various trajectories depending on the conditions, modes and nature of loading. At the same time, at each stage of the facility’s life cycle, an assessment of the accumulated damage under various loading conditions is carried out (Fig. 1) and a decision regarding the possibility of its further operation is made, with taking into account the accumulated damage and possibility of extending the facility design life (Makhutov, 2008; Gadenin, 2014; Gadenin, 2018).

Fig. 1. Parameters of damage at various stages of facility life cycle

A well-developed methodology for the calculation of a set of parameters that determine the degree of damage for the analyzed facility at the stage of its normal operation is usually available (Makhutov, 2008). At the same time, the system of calculations characterizing design basis, beyond design basis and hypothetical situations is based on the analysis and consideration of the conditions for the occurrence of damaged and limit states that lead to emergency and catastrophic situations. In the transition from the analysis of normal operation conditions to the analysis of beyond design basis and hypothetical emergency and catastrophic situations the criteria and regulatory bases for conducting calculations is currently practically missing (Makhutov, 2017; Makhutov, Gadenin, Reznikov, 2017). Fig. 2 illustrates conditions of operation of engineering facilities. The factors of external impacts on the facility and its reactions on these impacts S * are depicted on the vertical axis while the horizontal axis shows the level of influence of factors of operating conditions F e (number loading cycles, time of exposure to load, temperatures, corrosive environments).

Fig. 2. States, scenarios and factors of operational loading