A Lamb wave method for characterizing the surface properties of solid plates
Deng Mingxi *
(College of Logistics Engineering, Chongqing, 400016)
Abstract Based on the Ritec-SNAP system, a Lamb wave experiment system was established, and the feasibility of using Lamb wave amplitude-frequency characteristics to characterize the surface properties of solid plates was analyzed. The experimental results show that the amplitude-frequency characteristics of high-order, multi-mode Lamb waves can accurately characterize the changes in the surface properties of solid plates.
Keywords solid plate, Lamb wave, amplitude-frequency characteristics
Characterization of surfaces of solid plates using a Lamb wave approach
Deng Mingxi
(Logistics Engineering University, Chongqing, 400016)
Abstract On the basis of Ritec-Snap measurement system, the experimental set-up using a Lamb wave approach has been established. This paper analyzes the feasibility of using the amplitude-frequency characteristics of Lamb waves to characterize the surfaces of solid plates. The experimental results show that the amplitude-frequency characteristics of high-order, multimode Lamb waves can be used to effectively characterize the changes in properties of surfaces of solid plates.
Key words Solid plates, Lamb waves, Amplitude-frequency characteristics
1 Introduction
The solid board structure widely used in practice will change its surface properties due to corrosion or other reasons. For occasions where the surface properties of solid plates cannot be directly observed (such as the inner wall of an oil storage tank or the inner wall of a pressure vessel, etc.), it is very important to study practical detection methods that can accurately characterize surface properties. In general, the thickness of the solid plate structure is relatively small, and the use of the traditional ultrasonic echo method is limited; on the other hand, changes in surface properties are difficult to effectively affect the echo signal. In recent years, Lamb waves have been widely used as an effective means in the non-destructive testing of solid plate structures. Because of the multi-mode and dispersion characteristics of Lamb wave, Lamb wave detection method has more advantages than ultrasonic echo method in terms of detection sensitivity and detection speed [1]. The results of [2] show that the properties of the surface coating can be effectively characterized by measuring the dispersion relationship of Lamb waves. In fact, the change in the surface properties of a solid plate can be equivalent to a change in the thickness, density, elastic constant, and interface adhesion properties of a surface attachment layer. These factors will affect the propagation properties of Lamb waves.
From the practical application point of view, the use of diagonally split ultrasonic transducers can excite and receive Lamb waves on one side of the solid plate (such as the outer surface of the pressure vessel wall), thereby Surface). Changes in the surface properties of the solid plate will affect the phase velocity, amplitude, and attenuation of the Lamb wave. In addition, it can also affect the mutual conversion between multiple Lamb wave modes. In view of the many factors affecting the surface properties, it is difficult to comprehensively retrieve the relevant parameters of the surface properties through the Lamb wave dispersion relationship. In general, the Lamb wave dispersion characteristics before and after the surface property changes can be compared to determine the degree of surface property change. It should be noted that the influence of surface properties on the dispersion characteristics, amplitude and attenuation of different Lamb wave modes is different. It is very important to choose the appropriate Lamb wave mode [1-4]. From the perspective of practical application, the process of measuring the Lamb wave dispersion curve is relatively complicated, and it is not easy to operate in the field, and it is more convenient to measure the amplitude-frequency characteristics of the Lamb wave. This article first briefly analyzes the possible effects of changes in surface properties on the Lamb wave amplitude-frequency characteristics, and discusses the feasibility of using multi-mode Lamb wave amplitude-frequency characteristics to characterize the surface properties of solid plates; based on the Ritec-Snap system [5] The Mumbo experimental system, on this basis, experimentally studied the corresponding amplitude and frequency characteristics of the Lamb wave when the surface properties of the solid plate change. The experimental results in this paper show that the amplitude-frequency characteristics of high-order, multimode Lamb waves can effectively characterize the surface properties of solid plates.
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