Determination of necking zone using laser speckle

Abstract

This paper presents a whole field laser speckle method for the measurement of the necking zone on the surface of metallic specimens. The method employs an expanded laser beam to illuminate the test object. Diffracted images are recorded on a high resolution photographic film and subsequently filtered using pointwise filtering. The intensity of the diffracted halo is measured with a photo-sensor and the intensity distributionon the specimen yields information on the necking zone of the test object. The technique is applied to a flat tensile specimen with two circular notches at the central portion. Measured necking zone is compared with results obtained by other conventional methods.