Abstract
The cyclic behavior and endurance of austenitic stainless steels tested under NPP-relevant laboratory conditions has been studied. It had been earlier shown that long intervals between fatigue transients can affect the fatigue performance in stainless steels that are generally used in NPP primary piping. If this can be confirmed, then the transferability between laboratory results, design curves and the fatigue behavior of NPP components during plant operation shall be addressed. In addition to coolant water environmental effects, the material response during steady state normal operation should also be accounted for. Advanced Fatigue Methodologies (AdFaM), a joint project of European research laboratories, vendors and plant operators was focused on empirical and mechanistic investigations to confirm the claimed effects of hold times on fatigue life. Strain-controlled fatigue tests incorporating accelerated hold times at temperatures between 290°C and 420°C were performed on stabilized and non-stabilized stainless steel grades, which are used in Germany and the UK. Two material batches of both alloy types (304L and 347) were studied. The mechanisms responsible for the observed variations in stress response and fatigue life have been investigated using a range of microscopy techniques. The results confirmed the extension of fatigue life due to hold times in both stabilized and non-stabilized grades. This life extension appears to be linked to hold hardening observed in the cyclic behavior of both alloys. Tests incorporating hold times may be more representative of material behavior in NPPs, where temperature transients due to start-ups, shutdowns and major power changes may be separated by long periods of steady state operation. This gives reason to consider the transferability of standard laboratory test data to fatigue assessments of NPP components, and to propose a new factor ( Fhold ) as part of an advanced fatigue methodology and realistic transferability factor: F real = F en X F hold .
| Original language | English |
|---|---|
| Title of host publication | ASME 2017 Pressure Vessels and Piping Conference |
| Subtitle of host publication | Codes and Standards |
| Publisher | American Society of Mechanical Engineers (ASME) |
| Volume | 1A |
| ISBN (Print) | 978-0-7918-5790-8 |
| DOIs | |
| Publication status | Published - 1 Jan 2017 |
| MoE publication type | A4 Article in a conference publication |
| Event | ASME 2017 Pressure Vessels and Piping Conference, PVP 2017 - Waikoloa, United States Duration: 16 Jul 2017 → 20 Jul 2017 |
Conference
| Conference | ASME 2017 Pressure Vessels and Piping Conference, PVP 2017 |
|---|---|
| Country/Territory | United States |
| City | Waikoloa |
| Period | 16/07/17 → 20/07/17 |