Environmentally Assisted Fatigue Component Test: Test Program Overview and Transient Benchmark Evaluation

Abstract Environmentally Assisted Fatigue (EAF) correlations have been developed based predominantly on testing performed on small, simple specimens under mechanical loading and isothermal conditions. EPRI is currently leading an effort to conduct testing on realistic components with plant-representative transients. This work aims to assess whether using components and/or component-like features under plant-representative loading conditions will provide additional insights on the current EAF models for both fatigue crack initiation and propagation that have been developed from small-scale specimens tested under mechanical loading conditions. A test loop was designed in 2018 to subject a thick pipe to thermal strains from changing fluid flow conditions. The planned test transients were thermal shocks, moderate ramp rates, and slow ramp rates. After a series of delays, in 2023 the project was restarted, and the test loop commissioning activities began. This paper provides an overview of the test effort, initial results of thermal and strain benchmarking, and an overview of the non-destructive examination (NDE) tools and techniques to be used to identify crack initiation and propagation. Test specimens fitted with a series of strain gauges, thermocouples, and through-wall temperature sensors were subjected to the various test transients. The data are being used to assess the original design calculations and test duration predictions and refine them for the upcoming prototype testing that will be performed in the next phase of this effort.