Abstract
The numerous methods of a crack detection have been developed for the purpose of assessing the integrity of the structure. Among them, pattern recognition techniques for digital image are to evaluate cracks morphologically based on image processing, which are effective in the case that the crack on the surface is visually apparent. However, fault detection might be unavoidable in principal of the system for the crack which is difficult to identify visually due to surface condition of the observation structures.
An attempt is made in this study to develop an invisible crack detection system based on non-contact displacement measurements. The maximum principal strain and the principal direction, which are calculated from the displacement vectors, are the prime parameters for crack identification. Based on the maximum principal strain and principal direction, the proposed system detects crack in each discretized elements on the digital image. The validity of the proposed SHM system is demonstrated through laboratory experiment.
