NDE Applications of an Optical Technique for Noncontact Measurements of In-Plane Strains
Measuring whole field strain over two-dimensional fields is important in NDE, especially if such measurements permit the qualitative representation of data, allowing for the imaging and detection of defects. A number of techniques have been used to achieve this, including moire interferometry, holographic interferometry and speckle interferometry. Although all of these methods can provide qualitative images representative of the deformation field, they share the disadvantage of being difficult to analyze quantitatively. This is due to the need for the interpretation of the fringes generated by these techniques, which is time consuming and requires highly skilled practitioners. Additionally, even though these experimental techniques provide a whole-field qualitative appraisal of a two-dimensional field, quantitative data are obtained only at discrete points over the areas of interest.