A Study for establishment of passive creep-fatigue test techniques using the difference of thermal expansion coefficients of the materials

Wakai, Takashi ; Ando, Masanori ; Okajima, Satoshi ; Toyota, Kodai ; Onuma, Terumitsu*; Takahashi, Ryoya*; Asayama, Tai 

This paper describes an experimental study for establishing a passive creep-fatigue test technique that mainly utilizes the difference in thermal expansion coefficients of the materials as material surveillance test technique that can be applied to evaluate the structural integrity of the fast reactor components when the components are used beyond the period assumed in the design. Using the test article designed with the aid of a finite element analysis, a long-term creep-fatigue test data has been successfully obtained. In the designing of the test article, it was essential to generate a adequate strain at the gauge portion of the specimen due to the difference of thermal expansion coefficients of the materials, without buckling. After much trial and error, an optimal shape and dimensions of the test article and the cyclic thermal load conditions are established. In the future, miniaturization of the test article for applying the established test technique to the actual nuclear reactors will be required.