Establishing a multi-laboratory test plan for environmentally assisted fatigue

The European project INCEFA-PLUS will characterize environmental fatigue in pressurized water reactor (PWR) conditions. The aim is to develop new guidelines for assessing environmental fatigue damage susceptibility of nuclear power plant (NPP) components. The consortium consists of 16 public and private organizations from across Europe. The project is structured in two phases: The first phase is an extensive fatigue testing program; in the second phase, a procedure for estimating the environmental fatigue degradation of the materials will be formulated. During the test phase, a selection of austenitic stainless steels used in NPPs will be characterized with regard to fatigue. The test matrix will focus on the effects of mean strain, strain amplitude, hold time periods, and surface roughness on fatigue life. Sensitivities to these parameters will be tested in PWR environments with additional tests in air for reference purposes. The study of hold time effects will lead to very long testing times, limiting the total number of tests. It is therefore crucial to establish a test matrix that allows the study of the principal effects of interest while taking into account the nuisance effects, such as different specimen geometries, particular material microstructures, and other laboratory-dependent factors that may not be well-controlled. Methods and considerations for establishing a single test matrix are presented in this work.