COMPUTED SPECKLE DECORRELATION (CSD) FOR THE STUDY OF FATIGUE DAMAGE

A video-based laser speckle technique has been developed for non-conta ct analysis of fatigue in situ and at speeds approaching video frame r ates. This technique, computed speckle decorrelation (CSD), makes use of the speckle decorrelation associated with surface deformation. It i s a method of full field inspection which both locates fatigue damage sites and measures damage severity. In its current application, CSD ha s been used to study the fatigue deformation progression in reverse be nding fatigue of a cylindrically notched aluminum specimen. However, f ilm based studies have shown the usefulness of laser speckle decorrela tion to analyze fatigue deformation of thick graphite/epoxy composite materials as well. With the development of the CSD method it will now be possible to examine in greater detail the progression of fatigue da mage in these materials, allowing a much faster and more quantitative analysis than was previously available.