Abstract
We present a phase method for ultrasonic thickness measurement of materials with significant attenuation and variants for its improvement in order to increase the efficiency of detection of informative signals and the accuracy of determining their time position. At present, composite materials have become widespread in various technical fields. Various methods, including acoustic, are used for their non-destructive testing. It should be noted that a large part of such materials has significant coefficients of attenuation of acoustic oscillations. Therefore, extending the capabilities of methods for ultrasonic thickness measurement of articles made from such materials is an important task. There are two ways that are proposed to improve the method: by using a combination of procedures for preliminary filtering of the investigated signals based on empirical mode decomposition and subsequent adaptive median filtering of r-statistics, as well as applying weight processing of r-statistics. We carried out computerized measurement experiments, which allowed the justification of choosing the aperture of a sliding window in the devised methods; we obtained dependences of signal/noise values of the initial informative characteristics on signal/noise values of the investigated signals. It is shown that the error in determining a time position of the detected echo impulses, when using the improved methods, is 1.5–2 times less than the error when the basic method is applied. The results obtained could be used for the development of new ultrasonic echo impulse thickness measurement devices with improved metrological characteristics.
Highlights
There is a steady tendency to extend application scope of the ultrasonic non-destructive testing (UNDT) and improve quality indicators of testing tools through the use of new information-measuring technologies
Composite materials have a significant attenuation of ultrasonic oscillations, which complicates a process of detection and analysis of ultrasonic thickness measurement (UTM), and makes it impossible to implement UNDT by existing means in some cases
We used the following notation for the elements of the scheme: EMD is the module of empirical mode decomposition, CF is the module for selection of informative components and restoration of UTM signal, НD is the module for the discrete Hilbert transform, phase characteristic of a signal (PCS) is the PSC determination module, Σ is the module for determining φ[ j], WP is the module of window processing and determination of θ[k, Mr], r is the module for determining r statistics, adaptive median filtration (AMF) is
Summary
There is a steady tendency to extend application scope of the ultrasonic non-destructive testing (UNDT) and improve quality indicators of testing tools through the use of new information-measuring technologies. This applies to such an important segment of UNDT as the study of composite materials. One of the common methods of investigation of materials and products is the echo impulse ultrasonic thickness measurement (UTM) [1]. It is an important task to improve UNDT in order to increase reliability of detection of UTM signals when studying materials with significant attenuation of ultrasonic oscillations. UTM possibilities depend on the way of formation of information signals in the system “ultrasonic transducer – TO”, and on the selected informative parameters and characteristics of a signal, as well as the processing method
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