A Recent Development in Creep-Fatigue Testing

Procedures for the assessment of components subject to cyclic loading at high temperatures require material property input data that characterize the creepfatigue deformation response and resistance to cracking. For many years, there was no testing standard or code of practice to ensure that such information was generated in a uniform way. This was mainly because the creep-fatigue test data requirements for organizations in various industrial sectors appeared to be so different that the need for standardization was questioned. In the mid-2000s, it was recognized that even though it would make no sense to be prescriptive about such details as cycle shape, there were many aspects of creep-fatigue testing for which guidance would be beneficial to ensure acceptable uniformity in deformation and endurance data generation. In response to this realization, the state of the art relating to creepfatigue interaction was extensively reviewed by an international group of specialists, and the generated knowledge base was used to underpin a new ASTM testing standard, ASTM E2714-09. The gathered knowledge is reviewed. There is a requirement for all ASTM standards to include a precision and bias statement, and an international interlaboratory creep-fatigue test comparison activity was facilitated to form the basis of this section of ASTM E2714-09. An integral part of the guidance given in the new standard is the recommendation for post-test metallurgical inspection and the way in which this information can be used to give added value to creep-fatigue crack initiation endurance results. The evidence gathered from this study is also examined.