Measurement of Y-notch tip plastic zone by the laser speckle technique

Abstract

This paper presents a laser speckle method for the measurement of plastic zone ahead of a Y-notch tip on metallic specimens. The method employs an unexpanded laser beam to illuminate the test object. Diffracted images are captured on a ground glass and recorded using a CCD camera. The recorded images were digitised and subsequently analysed on a personal computer. The plastic strain at the notch tip was correlated with its corresponding speckle image using a recently proposed parameter known as the integrated peak spectral intensity coefficient. Specimens containing Y-notches of various angles were tested and the results compared well with that predicted by theory.