In-Situ Thermography Investigation of Crack Growth in Armco Iron under Gigacycle Fatigue Loading

A non-destructive thermographic methodology based on the temperature field is utilized to determine crack tip position during very high cycle fatigue (VHCF) test of pure iron and deduce corresponding growth rate (FCGR). To this end, a piezoelectric machine employed 1 mm thick samples at 20 kHz in push–pull loading. Two cameras are placed each side plate sample, an infrared one for measuring fields specimen surface optical visualizing verification. The centre section notched initiate crack. converted into intrinsic dissipation quantify inelastic strain energy according conservation. maximum value thermal image related thus allows monitoring evolution test. obtained results show that specific broke 7.25 × 107 cycles presence low-stress amplitude (122 MPa). It observed has low-constant level initiation short cracking, then sharply grows long cracking. This transition visible polished where plasticity appears cracking slightly before. material parameters Paris equation from close available literature as well those by camera.