An electromagnetic method for frequency analysis of transverse vibrations of a beam

Vibration-based diagnostics of constructions is an obligatory technical procedure in mechanical engineering. In this regard, there is a problem of an adequate theoretical description of vibration processes in various structures with account for end fixity conditions, as well as the creation of experimental facilities for non-contact testing. The paper presents a theoretical basis and experimental verification results for a method of electromagnetic frequency analysis of rod systems. The essence of the method is the experimental determination of natural oscillation frequencies and their comparison with reference values. The main attention is paid to a theoretical description of transverse vibrations of a cantilever conductive rod in an external magnetic field in order to determine reference frequencies of a defect-free sample. The presence of the external magnetic field gives rise to the distributed electromagnetic force exerted on the rod. In the case of natural oscillations, the magnetic force is damping, which leads to a change in damping factors of partial oscillations. The electromagnetic effect is selective towards vibrational modes; hence, the damping factors of various partial oscillations of the rod vary to different degrees. This fact allows one to determine an optimal location of the area with acting magnetic field, as well as its width when measuring a given frequency of sample testing. The proposed method has several advantages: indestructibility of the sample, non-contact measurements, invariability of mechanical properties of the sample during the tests.

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