Investigation On Damage Detection In Structures Based On Wavelet Theory

Cracks present a serious threat to the performance of structures since most of the structural failures are due to material fatigue. For this reason, methods allowing early detection of cracks have been the subject of intensive investigation, which help management the structure and reducing the cost for refinement. As we know, defects in the structure will cause some changes in the dynamic character, such as frequency, mode shape and damp, which can be used to indicate the state of the structure. So a lot of researchers devote their attention to detect the damage in the structure and develop many methods based on the dynamic character of structure. In recent, the applying of wavelet time-frequency get the interesting of the researchers which was considered as the method can detect both local damage and the whole character of the structure. But there still have some problem need to consider, such as "how to describe and select the damaged mode in mathematic viewpoint"; "the principle of selecting wavelet function should be considered"; "the affection of the surroundings on the identified result need to study further"; "lack discuss to acquire the completely damaged information" etc. Considering the above problem, the author studied that the first mode is applied to wavelet analysis and singularity analysis using wavelet spatial-frequency analysis for mutil-scale. The location of the crack is detected by the sudden change in the spatial variation of the transformed response. The intensity factor, which defined by Lipschitz condition and...