Wavelet transform of acoustic emission signals in failure of model composites

Characterisation of Al corrosion and its impact on the mechanical performance of composite cement wasteforms by the acoustic emission technique

“…The primary frequency, defined as the most energetic frequency component in the Fourier spectrum, has been used to classify different failure modes in concrete and composites [17,28,29]. However, the FFT is of a fixed resolution at all frequencies and can obscure small, high frequency events which usually last for a very short interval of time (a few tens of μs) [29,30]. These events can be characterised by WT.…”

“…The scale b in WT corresponds to the scale used in maps, i.e., high scale is used for low frequencies which correspond to global information of the signal and low scale for the frequencies that can provide more details for important mechanical events usually lasting for very short time [17,[29][30][31]. Different mother wavelet functions ( ) t ψ have been studied and applied for analysis of complex signals such as AE transients.…”

“…Different mother wavelet functions ( ) t ψ have been studied and applied for analysis of complex signals such as AE transients. However, the Gabor analysing wavelet was shown as suitable to differentiate failure modes in various materials [29,30]. Gabor mother wavelet ( ) t ψ is given as [31]: (Fig.…”

“…The WT analysis can be also used to provide information on the time of occurrence and the duration of the low and high frequency components found in acoustic signal waveforms [29]. 2D plots of WT at frequencies of 34 kHz and 107 kHz are illustrated in The dominant low frequency component at 34 kHz, as shown in Figs 9b and 10b, lasted during the first 100 μs whereas the selected high frequency wave mode at 107 kHz was present for less than 20 μs of the duration of the hit.…”

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“…Зокрема, Огіра й Пао досліджува-ли процес зародження мікротріщини у компак-тних зразках товщиною 25 мм, виготовлених із корпусної реакторної сталі А533В, під час ви-пробувань на тріщиностійкість [33,34]. Для цьо-го використовували восьмиканальну АЕ-систе-му з широкосмуговими перетворювачами, які мали верхню частотну межу 3000 кГц та попе-редніми підсилювачами зі смугою пропускання 10…2000 кГц і підсиленням 60 дБ.…”