A thermographic method for remaining fatigue life prediction of welded joints

An in situ technique for predicting the Remaining Fatigue Life (RFL) of metal specimens is used to study welded joints. Uniaxial tension–compression tests were carried out using welded and heat treated tubular specimens of carbon steel 1018. An infrared camera was used to capture thermographic data from the specimens during testing. Short-time excitation (STE) tests were used to determine the slope of temperature increase at several points throughout the fatigue life to characterize the damage. Verification tests were carried out at different stress levels to study the accuracy of the RFL prediction method on welded specimens. The presented results show good agreement between the predicted and experimentally measured fatigue lives. However, tests with welded specimens containing flaws showed significantly shorter fatigue lives. The prediction method discussed in this paper does not characterize the RFL of flawed specimens.