Observations of fatigue crack behaviour in proton‐irradiated 304 stainless steel

Abstract

Thermoelastic stress analysis (TSA) has been used to monitor fatigue crack growth in compact tension (CT) specimens, made from 304 grade austenitic stainless steel, that have been subject to proton irradiation. Several specimens had a 10 × 10 mm area ahead of a 1‐mm precrack irradiated with a 1.6 MeV proton beam up to 0.216C to 0.648C of accumulated charge prior to fatigue testing. Subsequently, specimens were loaded sinusoidally at 20 Hz with an R ratio of 0.5, and TSA data were collected both at the loading frequency and its second harmonic. Irradiation appears to cause an increase in the fatigue life, with a reduction in crack growth rate observed in the irradiated specimens compared with the unirradiated control specimens. Irradiation damage caused a moderately linear change in both the parameters of the Paris law with accumulated charge from the irradiation.

Effects of Ion Irradiation on Stage II Fatigue Crack Growth and Plasticity

“…Past studies have reported no change or only a slight increase in fatigue life caused by irradiation. 2,[10][11][12][13]15 While this study found an overall decrease in fatigue life, caused by irradiation, stage II crack growth was examined here, meaning that crack initiation and short crack propagation were not considered. Additionally, large variations in irradiation procedures exist between this study and others, including ion energy and type, irradiation temperature, and flux leading to the large variation in experimental results.…”

“…Specimens were loaded with an Electropuls E3000 (Instron, Norwood, MA, USA). To generate the pre‐crack in a viable timeframe, a reducing load procedure was implemented at a test frequency of 80 Hz 13 . The initial load was 600 ± 200 N, and every 30,000 cycles the mean load and amplitude were reduced by 30 N and 10 N respectively, keeping R‐ratio at a constant of 0.5.…”

“…To generate the pre-crack in a viable timeframe, a reducing load procedure was implemented at a test frequency of 80 Hz. 13 The initial load was 600 ± 200 N, and every 30,000 cycles the mean load and amplitude were reduced by 30 N and 10 N respectively, keeping R-ratio at a constant of 0.5. When a load of 450 ± 150 N was reached, the load was maintained until a crack of 1 mm had grown.…”

“…11 For 316LN stainless steel, no difference in low cycle fatigue life was observed after high temperature irradiation between 450 and 750 C and fatigue testing at 550 C. 12 Specimens of 304 stainless steel irradiated with protons at 350 C showed a slightly increased fatigue life. 13 Fenici and Suolang found that 316 stainless steel irradiated in situ with protons had an increased time to crack to initiation. 14 In situ low cycle fatigue tests of 316L steel during neutron irradiation showed no significant changes compared with un-irradiated specimens.…”

Resurgence of a Nation’s Radiation Science Driven by Its Nuclear Industry Needs

“…Heavy ions are of particular interest in radiation damage studies as although their range in a material is limited, they create large amounts of damage in their short path. Some of these studies include candidate materials for plasma-facing walls and structural materials in fusion reactors [14][15][16][17], structural components for fuel assemblies inside nuclear cores [18,19], as well as investigation of potential new materials for use in such extreme environments [20,21].…”