Ultrasonic inspection of partially completed welds using EMAT-generated surface wave technology

Weld inspection is a recurring topic in nondestructive testing because of the potential safety and environmental impact associated to poor weld quality. Thick-wall, multi-pass welds are very common in construction, bridge building, ship building, pressure vessel, and many other industries. This paper presents a novel technique to provide process and quality control of a partially completed weld after each individual weld pass, which can provide significant savings in time and money. The technique uses electromagnetic acoustic transducer (EMAT) to generate surface acoustic waves that detect defects on the top-most layer of a multi-pass weld. The paper describes the theory and empirical verification on a partially finished weld with 100mm thick base metal.