13th International Conference on Fracture June 16–21, 2013, Beijing, China -2- While many examples of fatigue dominated and creep dominated in-service damage can be presented, the most problematic situation from a predictive point of view is when the effects are interactive. Under these conditions the primary concern is whether damage accumulates more quickly than would be expected for either mechanism alone. As power generating systems seek maximum flexibility from available plants, increasing numbers of components must operate in creep-fatigue conditions. Moreover, recent installation of combustion turbines and heat recovery steam generators have increased the number of materials and components that operate in high-temperature, cyclic conditions. In addition, high-efficiency coal plants operate with even higher steam and metal temperatures than those of traditional plants. Thus, creep-fatigue damage will occur more frequently and in more materials, including low-alloy ferritic steels, austenitic steels, nickel-based alloys, and creep-strength-enhanced steels. The present paper documents the current state of knowledge on creep fatigue behaviour and outlines achievements from the EPRI collaborative work. 2. Achievements EPRI’s long-range research program (Technology Innovation) initiated a set of activities in 2006. The initial goals of the work were to: – Examine how problems of Creep-Fatigue assessment are addressed internationally – Identify deficiencies that exist with current knowledge and approaches, and – Recommend improvements in application of the available technology and identify future Research and Development needs. EPRI’s overall approach to establishing solutions to assessing creep fatigue performance has involved facilitating discussion at annual expert workshops, preparation of critical reports and publications, facilitating the preparation and review of new ASTM standards for laboratory creep fatigue testing and establishing a platform and associated knowledge base of materials behavior. EPRI’s Fossil Materials & Repair Program has funded many specific activities, but the overall success of this effort is due to broad international collaboration with participants bringing their own resources and expertise together including focusing their scopes of work for the benefit of the group. Key elements of these achievements are presented here. 2.1. Expert Workshops A series of EPRI facilitated Formulative Expert Workshops has succeeded in presenting up-to-the- minute information concerning the current state-of-knowledge of creep-fatigue damage interaction. The meetings have been hosted at different global locations and the presentations made at these workshops have been published by EPRI, Table 1. In addition, the discussions held resulted in the development of an agreed listing of key issues for future consideration. These issues have been reviewed and updated as necessary and continue to be used to guide current and future work. Table 1. Annual Expert Creep Fatigue Workshops Year Location EPRI Reference 2006 Amsterdam, Holland 1014482 2007 Marco Island, USA 1018511 2008 Kyoto, Japan 1018512 2009 Paris, France 1020673 2010 San Antonio, USA 1024440
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