Strain Measurement Using Moire by Shifting Model Grating and Its Image Processing

Abstract

Strain measurement using moire by shifting a model grating is a useful method for full field measurement of strain distribution. We can obtain moire fringes which show a strain distribution by means of only superposing two copies of a deformed model grating shifted one with respect to the other. However, its disadvantage in applications has been the photographic process which involves time-consuming development of the photographic film. Also it has been difficult to shift a model grating exactly.
This paper presents a method using a TV camera and a digital image processor which employs a personal computer whereby high speed and exact measurements of strain distribution are possible. Using this system, we present a method for strain analysis by means of superposing two copies of a deformed cross grating. In addition, the principle and limitation of this method are described and some applications are shown.