Fatigue behavior of 316L austenitic stainless steel in air and LWR environment with and without mean stress

Abstract

The fatigue life design curves in nuclear codes are generally derived from uniaxial straincontrolled fatigue test results. Evidently, the test conditions are very different from the actual components loading context, which involves much more complex thermo-mechanical loading including mean stress, static load holding time and variation in water chemistry, etc. In this work, the mean stress and environmental effects on fatigue life of 316L austenitic stainless steel in air and light water reactor (LWR) environment were studied using hollow fatigue specimens and testing under load-controlled condition. Both positive (+50 MPa) and negative (-20 MPa) mean stresses showed beneficial effect on fatigue life in LWR environment and in air. This is tentatively attributed to mean stress enhanced cyclic hardening, which leads to smaller strain response at the same loading force. -20 MPa mean stress was found to increase fatigue limit, whereas the effect of +50 MPa mean stress on fatigue limit is still unclear. The preliminary results illustrate that the environmental reduction of fatigue life is amplified in load-controlled fatigue tests with tensile mean stress.

Environmental Fatigue Behavior of a Z3CN20.09M Stainless Steel in High Temperature Water

“…In Figure 4, the ASME design fatigue curve and the fatigue life in air at RT are also presented [4,8]. As is seen, in the same loading condition, the fatigue life of the Z3CN20.09M ASS in water at 300 • C was shorter than that in air at RT [2,3,6,9,[13][14][15]. It indicates that the involvement of corrosive medium or the interactions of corrosive medium with applied load might be responsible for the decrease in the fatigue life of the Z3CN20.09M ASS [16,17].…”

“…Furthermore, the difference in the fatigue life at these three strain rates became more pronounced at higher strain amplitude. It might be caused by the higher corrosion rate of the tested material at higher strain amplitude in the autoclave environments [6,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27].…”

In-Situ Hollow Sample Setup Design for Mechanical Characterisation of Gaseous Hydrogen Embrittlement of Pipeline Steels and Welds

“…By combining the setup with heating and cooling apparatus, he manages to characterise at a large range of temperatures. Chen and Spätig use a hollow sample as a containment volume for high temperature hydrogenated water [36]. Kogut and Pan'ko characterise the HE susceptibility of a weld metal by cracking a notched cylindrical specimen, welding the two halves back together over a part of the wall thickness and subjecting it to another test [37].…”

Interaction of Cyclic Loading (Low‐Cyclic Fatigue) with Stress Corrosion Cracking (SCC) Growth Rate

“…Recent studies have shown that SCC and fatigue, i.e., cyclic loading, both are present at a time on many structures of metallic materials [25,26], and the SCC environment (load, environmental conditions, and material susceptibility) has many influences on the fatigue crack growth rate, and vice versa. As an example, strain-induced corrosion cracking (SICC) is used for the situation where cracking takes place under increasing load which may not be increasing necessarily monotonically, but also some cyclic variations are present at start-up and shut down situations of the plants [27]; also during smooth operation, both the loadings, i.e., fatigue (cyclic) and stress corrosion, are present.…”