NONDESTRUCTIVE EVALUATION AND FATIGUE CRACK DETECTION OF DOUBLE BEVEL T-JOINT BY ULTRASONIC TESTING

Abstract

Double bevel T-joint is one of the most fundamental joints of steel bridges. Double bevel T-joint can be seen at beam-column connection of bridge piers. In the Japanese specifications, the welding should be full penetration. Fatigue cracks can be propagated from the weld defects such as incomplete penetration. Incomplete penetration should be avoided. The authors have developed a tandem array transducer. Specimens of double bevel T-joint were made. Ultrasonic test was conducted for those specimens. Detectability of incomplete penetration was investigated. Image reconstruction of incomplete penetration by synthetic aperture focusing technique was carried out. Height of incomplete of penetration could be estimated accurately. When a fatigue crack exists in a welded joint, crack tip opening occurs. Crack tip opening can be observed by echo height from the crack tip. Fatigue crack could be detected by comparing echo height between when load was applied and no load was applied.