STRAIN MEASURED ON THE SURFACE OF PLATES AND DISKS BY MEANS OF THE SHEAROGRAPHIC METHOD

The shearographic interferometry is employed as a nondestructive, full -field, optical testing method without contact. Fringes of constant st rain can be observed real-time on the surface of the investigated mach ine parts and are represented by the shearograms. In the tele-lens of the camera a shearing element inside resp. outside the focus is integr ated. Rigid body motions of the specimen are not recorded. The shearog ram shows dark and bright fringes which are the functions of the displ acement derivative. The holographic interferometry measures the out-of -plane deformations directly. A term of the out-of-plane strain can be determined by the shearographic method as well as the in-plane strain fringes under certain conditions which are described in the following . For this purpose the fringe patterns generated by the basic types of loading are presented and compared with the photo-elastic patterns sh owing obvious analogies.