S.K. Tso, F. Tong, and M.Y.Y. Hung (PRC)
Fault detection, impact-acoustics NDT, fuzzyassessment, tile-wall inspection
: Owing to the danger caused by falling of debonded tiles from tall buildings, a rapid and effective non-destructive testing (NDT) and evaluation (NDE) technique based on sounds excited by controlled impact is developed to assess the tile-wall bonding quality with robotic aid and high personnel safety. To facilitate result evaluation and maintenance planning, whenever defects are present, it is also important to estimate the approximate size of the adhesive degradation area. Though it is well-known that the natural frequency of flexural vibration reflects the relative size of the debonding area, strong multiple mode frequencies caused by complex shapes of defects or by not having impacts at the center of defects pose significant difficulties to the automatic extraction of the natural frequency. In this paper, a fuzzy scheme is introduced to improve the robustness and accuracy of assessment. Based on fuzzy theory, vibration principle and human experience, a fuzzy logic model relating the characteristics of impact sounds to the approximate size of the defect is developed and utilized. The design of the fuzzy system including membership functions and fuzzy reasoning rules is introduced. To demonstrate the validity of the proposed method, experimental results obtained from physical tile-walls are presented and discussed.
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