The detection of zones of strain concentration in welded joints by holographic interferometry

The paper is concerned with studies of strain-concentration zones in welded specimens by holographic interferometry. Plates of St 3 steel 80 mm thick and 450 mm wide were welded with a V-butt weld or with a single-sided shear U-groove weld. The amount of nonfusion (defect) was determined by the size of the root face of the edge bevel. The experimental setup for holographic interferometry includes a laser, a lens, a mirror, a loading device, a photographic plate, a camera, and a set of shutters located in front of the photographic plate for reproduction of the development of strain. It is shown that holographic interferometry is suitable for investigation of the formation and location of strain-concentration zones on the surface of a welded joint, both for static and cyclic loading, as well as for investigation of the kinetics of defect initiation and propagation up to complete fracture of the specimen.