Application of wavelet-spectrum analysis of acoustic signals for fatigue fracture diagnostics by free oscillation technique

Free oscillation technique (FOT) is widely used for research and diagnostics of fatigue cracks in metal parts, for revealing former in bolted and rivet joints etc. The main criteria for mechanical state evaluation using FOT is shift of natural frequency maxima in Fourier spectrum toward lower frequencies with increasing size of discontinuity. In this work with use of designed software for wavelet-analysis of 1D signals fatigue fracture of structural steel was investigated. The main informative features of wavelet-spectra used under FOT diagnostics are discussed. It is shown that consideration of wavelet-spectrum changes over frequency and time ranges allows increasing significantly reliability of diagnostics.