DIRECT MEASUREMENT OF FLEXURAL STRAINS IN PLATES BY SHEAROGRAPHY

Strains in a flexed plate are directly related to the second derivatives of the plate deflections. A technique is developed which enables shearography to measure second derivatives of deflection directly. The technique is based on generating fictitious carrier fringes in the form of periodic linear fringes of uniform spacing. The carrier fringes are distorted when the plate is deformed. The change in the pitch of the carrier fringes due to deformation yields the flexural strain directly. The pitch of the carrier fringes is equivalent to gage length.