Piezoelectric sensor for in-situ measurement of stress intensity factors

A method for monitoring fatigue cracks in thin-walled shell-structures using piezoelectric polyvinylidene fluoride (PVDF) films is presented. By means of a spatially resolved measurement, it allows the simultaneously localization of the crack tip and determination of the K - factors by solving the resulting inverse problem. In previous publications [1], [2] only the K-I - factors as well as the position of the crack tip could be determined with sufficient accuracy but not the K-II - factor. Therefore, the concept will be tested and verified using the example of a crack in an infinite plate. From that we deduce some recommendations for the electrode placement and the solution of the inverse problem. In addition, a first experiment of a cracked aluminum specimen is reported.