Characterization of Moment of Inertia Variations by Holographic Interferometry

Holographic interferometry (HI) is a powerful tool for mapping of surface defects. In conjunction with various stressing techniques [l–4], it offers an NDT tool for the detection of flaws within the volume of materials. The method is advantageous for integrity characterization of components to serve under mechanical stress, where the detailed shape, size and depth of the flaw within the material are of no interest. For most applications, where integrity is tested, the moment of inertia may be used as a measure for classification of the product and for the estimation of its reliability. The presence of volumetric flaws, when the sample is under loading, is expressed in the holographic interferogram. The exterma of the fringe pattern are used for determination of the displacement distribution. The second derivative of the displacement distribution is related to the bending moment and the moment of inertia. The moment of inertia may be further processed to obtain a function free from degrading influence of the specific measuring system employed [5]