Thermo-mechanical fatigue crack propagation experiments in Inconel 718

✍ Scribed by Lars Jacobsson; Christer Persson; Solveig Melin

• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 837 KB
• Volume: 31
• Category: Article
• ISSN: 0142-1123
• DOI: 10.1016/j.ijfatigue.2009.02.041

✦ Synopsis

An experimental test facility was developed to perform thermo-mechanical fatigue crack growth experiments. The thermal cycles were generated using hot and cold air flows distributed by a nozzle onto the test specimen. With the equipment it was possible to obtain TMF cycles with cycle times of 120 s with less than 10 °C temperature variation over the measurement length of the sample, cycling between 200 °C and 550 °C. The equipment allows TMF crack propagation tests up to, at least, 600 °C. The crack length and the crack closure level were determined using the potential drop technique. Thermo-mechanical fatigue crack propagation experiments were performed in-phase and out-of-phase with various Rvalues on samples of Inconel 718. Cylindrical specimens with a small starter crack were cycled in nominal total strain control. The crack propagation rate was determined and the correlation to the effective J-integral range, DJ eff , corrected for crack closure presented. The fracture surfaces showed a dominance of trans-granular crack propagation with striations, indicating a low degree of time dependency in the procedure.