Measurement of Elastic-plastic Strain of Curved Surfaces by the Moire Effect.

A copying technique for object-gratings based on an X-ray activated fluorescent layer attached to the object surface which generates visible light recorded by sensitive photographic material is described. By placing a line-grating between the fluorescent layer and the film deformed by loading, the wanted object photo appears and by superposing this photo on a reference grating the Moire effect arises. If a cross-grating is applied instead of the object-line-grating, the orthogonal displacement components may be determined by spatial filtering. Furthermore the accuracy of the measurement becomes greater by multiplication of the grating. The method is suitable for analysis of given curved surfaces.