Abstract
The series of the previous studies have concentrated on diagnosis of damage and deviation in structures using non-destructive tapping test. We have demonstrated the efficiency of tapping diagnostics using a simple structural model of the aluminum bar with a free end. This study deals with diagnosis of defect using a simple structural model of ABS resin bar with a free end. According to FEM model simulation, it becomes clear that natural vibration frequencies of the bar decrease when there is an internal crack. On the other hand, when the crack is located near the natural vibration node, there are very small or no changes at all. Whether or not the crack exists was assessed from correlation of the Wavelet coefficients for test ABS resin bars with and without crack. Rough location of the damage is determined from the relationship among natural frequencies. Using RMS analysis carried out by the maximum correlation of spectrogram of tapping sound signal, the analysis results demonstrate that the method by RMS can be an effective means to find position of defect and to judge presence of defect.
