APPLICATION OF A PHASED ARRAY EQUIPMENT APPLIED SYNTHESIS APERTURE FOCUSING TECHNIQUE FOR FATIGUE CRACKS OCCURRED FROM ROOT OF RIB-TO-DECK WELDS IN ORTHOTROPIC STEEL BRIDGES

Abstract

 In recent years, many fatigue cracks propagating from the weld root of trough rib-to-deck welds have been detected in orthotropic steel bridges. These cracks are occurred from the root of rib-to-deck welds, and thus cannot be detected using visual inspection. Non-detective testing can effectively detect these cracks. Especially, ultrasonic testing is the most reliable non-destructive method for these cracks. Various ultrasonic testing equipment has been developed so far, but it is difficult to detect small cracks. It is necessary to detect these cracks at the early stage of its propagation. A phased array ultrasonic equipment applied synthesis aperture focusing technique has been developed in order to detect internal cracks. In this study, to confirm the crack detection accuracy of the developed equipment, crack investigations using the equipment were carried out using specimens with fatigue cracks induced by experiments. Crack detection accuracy is evaluated by comparing with real cracks induced in specimens.