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Hovanesian Rochester, Michigan 48309Kalamazoo, Michigan 49008 A modified shearographic (speckle -shearing) method for the rapid detection of residual stress in elastic engineering materials and components has been introduced. A coherent monochromatic light source (laser) is required to enable interference fringes to appear in the recording medium as a result of path length changes occurring between the two separate exposures during the evaluation.The path length change is a function of the objects surface displacement. The method employs a special image -shearing camera permitting quasi -full field measurement of surface displacement.

This paper presents a method for evaluating residual stresses. The approach is based on measuring the deformation due to the relief of stresses produced by a hole drilling technique. The deformation is measured by digital shearography al. In addition, the technique is extended to evaluating stresses in concrete structures. In this application, the stresses in concrete are treated as residual stresses. Since concrete materials are weak in tensile strength, one method of assessing the integrity of concrete structures is to look for the presence of tensile stresses in concrete. Unlike holography and ESPI, digital shearography does not require special vibration nor ambient light independence. These features make the method practical for detection of residual stresses in a production/field environment.

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