PSI - Issue 32

O.V. Bocharova et al. / Procedia Structural Integrity 32 (2021) 299–305 Bocharova O.V., Andzjikovich I.E., Sedov A.V., Kalinchuk V.V. / Structural Integrity Procedia 00 (2021) 000 – 000

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object and increase the reliability of its work preventing emergencies it is important to develop a simple and effective non-destructive monitoring method that does not influence its performance characteristics. For defectoscopy of mechanical structures, machines and mechanisms, systems with wave low-frequency or ultrasonic effects are often used. According to the response of the structure to these effects, a conclusion is made about its state, the presence of a defect in the form of corrosion, cracks, interstices or foreign inclusions. In Dervilis et al. (2014) sonic approaches are used for detecting damages paddle blades of wind turbines at an early stage. An ultrasonic inspection was used by Kumar et al. (2016) for non-destructive studying of porosity on aerospace advanced carbon fiber epoxy resin system laminates. The porosity effects were evaluated in terms of ultrasonic wave attenuation. In Boopathy et al. (2017) the authors created a large review of traditional non-destructive techniques used for defectoscopy of aircraft parts. Advantages and disadvantages of ultrasonic, thermography, radiographic and electromagnetic testing, acoustic emission and stereography were analysed in this research. No modern advanced methods based on structural dynamics were covered in the review. The method of monitoring the natural frequencies of oscillations is effective for structures of limited dimensions (Akhtymov and Karimov 2013; Bocharova 2014). In Akhtymov and Karimov (2013) a method for identifying the beam cavity from two natural frequencies of bending vibrations, taken from different spectra, is given. In Bocharova (2014) the identification of cavity dimensions in an elastic cylinder is based on the use of the characteristics of its longitudinal oscillations and methods of perturbation theory. In Vatulyan and Denina (2012) the authors developed methods for determining the mechanical characteristics of heterogeneous structures by using the parameters of longitudinal, bending and torsional oscillations. Ruč evskis et al. (2009) proposed vibration-based damage detection method for localization of damage in laminated composite beams introduced by low-velocity impact. It was proposed to extract dynamic characteristics of the part by vibration experiments and use the magnitude of the mode shape curvature square for the detection of the damage location and size. The advantage of the proposed method is that it requires mode shape information only from the damaged state of the structure. Later Janeliukstis et al. (2019) adopted and successfully applied this method for cracking localization in prestressed railway concrete sleepers. 2. Methods In the present work, an effective method that allows determining the presence of a defect and its characteristics is proposed. The proposed method is based on the control of changes in the parameters of dynamic process and could be applied for structurally inhomogeneous bodies. Any change in the stress state or structure of the medium (the appearance or change in the geometric dimensions of the internal defect) leads to a change of the parameters of the surface wave field. Thus, by controlling the dynamic characteristics of the wave field on the surface of the controlled medium and comparing them with characteristics of nondefective medium, it is possible to control the structure and properties of the material at the production and exploitation stages. The advantage of this approach is its integrated character, based on the use of low-frequency vibrations. This allows to substantially increase the size of the area controlled by one sensor and thereby opens the perspective of creating systems of continuous monitoring - distance control of state of details and assemblies.

Fig. 1. Scheme of the experimental setup.