Moire Analysis of Strain by Fourier Transform

Abstract

A "complex moire pattern" is obtained by shifting the discrete Fourier spectrum of the image of a deformed grating. The strain distribution is given as the derivatives of the phases of the complex moire fringes. The analysis is completely automated by digital image processing. All of the laborious and subjective procedures required in conventional analysis, such as fringe sign determination, fringe ordering, and fringe interpolation, are completely eliminated, and objective, fast and accurate analysis is performed.