Abstract
A Nondestructive and noncontact technique for evaluating the plastic region near a crack by using infrared thermography is proposed. The welded sheet specimen with a through-thickness center crack is used. A pre-crack is located between two welding beads and is desired to be in the compressive residual stress field parallel to the crack. A uniform tensile load perpendicular to the crack is applied to the specimen. The temperature rise of specimen surface is measured by the infrared thermography. The effect of the welding residual stress on the shape and dimensions of the heated region is examined. The heated region and the temperature rise are compared with the plastic zone and the work of plastic deformation obtained by the elastoplastic finite element analysis. The validity and the limitations of the application of infrared thermography to the evaluation of the plastic region are discussed.
