Fretting fatigue tests and crack initiation analysis on zircaloy tube specimens

Grid-to-rod fretting damage remains as a significant cause of nuclear fuel failure in pressurized water reactors (PWRs). By using a self-designed apparatus, fretting fatigue tests directly on thin-wall tube specimens were carried out. The S–N curve of the Zr-4 tube under some given fretting contact pressure is obtained, which is substantially lower than its life without fretting. And the initial crack occurs at the edge of the contact area where the amplitude of stress is confirmed to reach the maximum by FEM simulation. The position can be predicted by half-length of the initial contact region and the slip displacement.