engleski

Use of real time wavelet analysis for processing of acoustic waves in impact-echo measurements

A range of mechanical engineering methods for testing and evaluation of materials and structures are based on acoustic wave analysis. Some mechanical and other physical processes, while occurring, generate a number of short acoustic wave pulses. Depending on the location and type of source of these acoustic waves we can distinguish three main groups : 1. External source, impact excitation: IMPACT-ECHO 2. External source, sine wave excitation: ULTRASONIC TESTING 3. Internal generation, wave shape "as is": ACOUSTIC EMISSION Detetecting, measuring, and processing these acoustic pulses (sometimes called events) is recognized as one very promising method of discovering existence of flaws in mechanical engineering structures and elements, friction and other phenomena (including even such as corrosion). Frequency range of acoustic waves of interest is from 20 kHz to approximately 1 MHz, and amplitude levels usually encountered are very small, sometimes only slightly above the noise level of the current measurement abilities. As part of the work on the project under grant No: 023041 of Croatian Ministry of Science, extensive research in acoustic wave phenomena was undertaken and some of the results are presented in following sections. A complete data acquisition and processing has been developed, in a way that allows easy hardware and software changes, and low space and power consumption. Such a solution offers portability and stand-alone operation as an option. Results of wavelet transformation show good contrast between acoustic wave data and noise, and some features of the processed signal are clearly visible.

Impact-Echo; DSP; Wavelets

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