A Study On The Thermo-Mechanical Fatigue Loading For Attaining Minimum Cycles In Fabricating An Artificial Cracked Specimen

Jooho Choi, Gyubeom Lee, Boyoung Lee
School of Aerospace & Mechanical Engineering, Hankuk Aviation University, Korea

The Fourth China-Japan-Korea Joint Symposium on Optimisation of Structural and Mechanical Systems, Kunming, China, Nov 6-9, 2006

In the nuclear facilities, fatigue cracks are often observed in pipes during the operation of the Reactor Coolant System (RCS), which originate from the cyclic loading caused by thermal stratification. Though the NDT methods are employed to detect the crack, sufficient number of repeated exercise should be preceded using artificial cracked specimen of a same kind for the reliable on-site detection. The crack of this kind, which has less than 150 m width, can not be made by the conventional machining methods such as EDM, but should be made under thermal cyclic load that is close to that of the RCS. The time for obtaining the wanted crack, however, is prohibitively long, which makes it difficult to be supplied in sufficient number for NDT evaluation. In this work, single edge crack of a rectangular plate is considered as a preliminary study, in which constant tensile as well as repeated thermal loads are applied to let the crack grow. Optimum loading condition is sought that minimizes the time for fabricating the wanted crack size. The crack growth phenomenon is evaluated through the coupling of crack growth simulation software Zencrack with the general purpose analysis code ANSYS.