抄録
A new remote nondestructive inspection technique, based on thermoelastic temperature measurement by infrared thermography is developed for evaluation of fatigue cracks propagated from welded joints in steel bridges. Fatigue cracks are detected from localized high thermoelastic temperature change at crack tips due to stress singularity under variable loading by traffics on the bridge. After the crack detection, stress distribution under variable loading by the traffic is precisely measured by the infrared thermography. Stress intensity factors K_I and K_<II> for a mixed mode crack are obtained from measured stress distribution. It is found that stress intensity factors K_I and K_<II> can be evaluated with the reasonable accuracy by the proposed technique. It enables us to assess an exigency of maintenance and to evaluate remaining life based on crack propagation rate.
