Fatigue damage diagnosis using statistical, spectral, and wavelet analysis techniques

The objective of this work is to illustrate a comparative investigation into the signatures of crack initiation and propagation using vibration and displacement signals. Experimental tests were performed on low carbon steel specimen under fully reversed bending cycles in a cantilever support configuration. Accelerometer and displacement-sensor vibration signals were collected using a National Instrument data acquisition system. Several methods, such as statistical moments, FFT, Wavelets, and short-time-frequency analysis techniques, were used to analyze the collected signals. It was found that the wavelet analysis gave the most consistent patterns in tracking crack initiation and propagation. For the wavelet analysis, extensive comparative investigation was conducted to select the optimum combination of wavelet packets for crack detection and monitoring.