Detection of fatigue cracks in steel bridges by self-reference lock-in thermography

摘要

A new remote nondestructive inspection technique that is based on thermoelastic temperature measurement by infrared thermography was developed for the evaluation of fatigue cracks propagated from welded joints in steel bridges. Fatigue cracks were detected from localized high thermoelastic temperature changes observed at crack tips induced by stress singularity under variable loading resulting from traffic on the bridge. A self-reference lock-in data processing technique was developed for improving the signaloise ratio of the thermal images recorded in the crack detection process. In this study, remote and nondestructive detection of fatigue cracks in an actual steel bridge in service was performed by the self-reference lock-in thermography method. The accuracy of this method was improved with a motion compensation technique.