Abstract
Using a dynamic mechanical analyzer, the comparative studies of a low-cycle bending fatigue were carried out for AISI 1022 low-carbon steel after extreme thermal exposure, simulating the severe beyond-design-basis accident at nuclear power plants. In the as-delivered state, the steel has a high resistance to low-cycle fatigue (the fatigue strength at N = 3.5 × 104 cycles (σNf) was 360 MPa). Long-term thermal exposure led to a slight decrease in the resistance to low-cycle fatigue of steel: σNf is decreased by 9%. The influence of AISI 1022 steel structure on the characteristics of fatigue strength and fracture mechanisms is analyzed.
Highlights
Resistance of Low-Carbon Steel.Currently, low-carbon steels remain the most popular structural material for civil and industrial construction of buildings and structures [1,2,3]
In this work, using a dynamic mechanical analyzer (DMA), the comparative studies of low-cycle bending fatigue of AISI 1022 low-carbon steel, having different types of structures obtained under prolonged thermal exposure and simulating the conditions of severe beyond-design-basis accident at nuclear power plants, are carried out
According to the results of comparative tests using a dynamic mechanical analyzer for low-cycle bending fatigue of AISI 1022 low-carbon steel specimens in the as-delivered state and after extreme thermal exposure in two modes—(1) slow cooling from 650 ◦ C for 7 days and (2) holding at 1200 ◦ C for 3.7 h with slow cooling—the following conclusions were made: (a)
Summary
With the development of a severe beyond-design-basis accident, when the corium falls outside the reactor core, the CC-vessel, according to calculations, heats up to 1000–1200 ◦ C with subsequent long-term cooling [8,9] Under such conditions, a significant change in the steel structure can occur and, as a consequence, cause the degradation of the mechanical properties of steel (due to the growth of austenitic grain and the development of reversible temper embrittlement), leading to a loss of strength in the CC-vessel and an increase in the risk of its fracture. In this work, using a DMA, the comparative studies of low-cycle bending fatigue of AISI 1022 low-carbon steel, having different types of structures obtained under prolonged thermal exposure and simulating the conditions of severe beyond-design-basis accident at nuclear power plants, are carried out
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