Determination of the plastic zone by laser-speckle correlation

Abstract

Laser-speckle-pattern correlation is used for the determination of elastic-plastic boundary on the surface of well polished metal specimens. The method employs a converging laser beam to illuminate the test object. Diffracted verging laser beam to illuminate the test object. Diffracted images are recorded and processed on a computer-based vision system. Subsequent image-correlation analysis yields information on the surface deformation of the test objects. The technique is applied to a flat tensile specimen with two circular notches at the central portion. Measured plastic zone is compared with results obtained by the finite-element method.