An algorithm for structural health monitoring by digital image correlation: Proof of concept and case study

• Full-field analysis offered by Digital Image Correlation (DIC) is used for structural health monitoring applications. • Model order reduction techniques applied to displacement fields provide a small number of “modes” that can account for displacement fields characterizing a sound structure. • Projecting any current displacement field onto the sound modal basis may spot damage thanks to error indicators or outlying amplitudes. • Fast one-step (non-iterative) integrated DIC was designed based on such reduced displacement modal basis and its amplitude statistics. In the field of structural health monitoring, the use of Digital Image Correlation (DIC) on relevant surfaces offers remarkable advantages. Such a method is presented herein. The statistically stationary nature of usual loads makes it possible to determine, by training with DIC, a reduced kinematic basis (composed of “modes”) and a statistical amplitude distribution for each mode. Further, a specific DIC technique is proposed to deal with such particular kinematics by introducing an extractor per mode that operates on images after a filtering step. This per-mode DIC measurement reduces to a simple scalar product between the image and the corresponding extractor, which allows for very fast and non-iterative processing. As an illustration, this methodology is deployed on a test case of fatigue crack propagation.