Abstract
Optical methods for measuring stress and strain can perform whole field analysis, unlike point-wise methods such as strain gages. However, it is time-consuming to analyze the whole field data because of a huge amount of data. Therefore image processing is widely used recently to save labor. In the early stage of the image processing for fringe pattern analysis, the method detecting the fringe center lines was used. It is, however, difficult for the method to obtain accurate results and to perform automated analysis. After the stage, some new methods using the characteristics of image processing have been developed. Especially, phase analysis methods using all data of an image are widely used because of the ability of highly accurate and fully automated analysis. This paper introduces the Fourier transform moire and grid method (FTMGM) and the phase shifting method using Fourier transform (PSM/FT). The former uses a 2-D image and the latter does a 3-D image. The principle for measuring accurate stress and strain distribution, and some examples applied to composite materials, honeycomb materials, rubber tubes, rubber plates, glass plates and epoxy plates are shown.
