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Application of wavelet and EEMD combined denoising in nonlinear ultrasonic testing of concrete

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Document pages: 11 pages

Abstract: The health condition of concrete is deteriorating during use. Nonlinear ultrasonic testing based on fundamental and second harmonic amplitudes is considered to be a powerful tool to find concrete microcracks. However, the research on nonlinear ultrasonic signal processing is not enough. In order to highlight the real frequency domain components of nonlinear ultrasonic signals, wavelet and integrated empirical mode decomposition (EEMD) are combined to denoise numerical signals and measurement signals. The optimal wavelet basis and decomposition level are determined by signal-to-noise ratio (SNR). Then, the wavelet threshold denoising signal is decomposed by EEMD to omit the high-frequency components, and finally achieve the desired denoising effectdenoising effect. The denoising result of the test signals demonstrates that this method is effective in denoising the details of the ultrasonic signal and improving the reliability and adaptability of the nonlinear ultrasonic testing. In this experiment, the concrete with the microcrack was tested by linear and nonlinear ultrasonic methods. Based on the variation regularity of the nonlinear ultrasonic coefficient and velocity , we can conclude that the nonlinear ultrasonic parameter is more sensitive to the microcrack in concrete than the traditional wave velocity . The nonlinear ultrasonic testing can be an important supplement to the current nondestructive testing technique of the concrete.

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