Determination of vibrodiagnostic parameters of the breathing crack presence in the beam structural elements of different cross sections
Journal Title: Вісник Тернопільського національного технічного університету - Year 2015, Vol 79, Issue 3
Abstract
This paper is concerned with the determination of the regularities in the influence of a “breathing” crack on the vibration characteristics of beam structural elements with a different cross-sectional shape. The forced vibrations of damaged cantilever beams of rectangular and circular cross sections at super- and subharmonic resonances are considered. The calculations were performed by varying the point of application of the harmonic exciting force along the length of the beams. To make the calculations, the finite element models of the beams are used in which the “breathing” crack is represented as a mathematical cut, and the mutual “non- closure” of the crack faces was provided by solving the contact problem. The ratios of the amplitudes of the dominant harmonics of displacements – for the finding of which the Newmark method, allowing the obtainment of the time dependence of the free beam end, and the FFT-analysis, resulting in the obtainment of the amplitudes of the displacement harmonics, were used – were regarded as a vibration-diagnostic parameter of the presence of a crack. Based on the results of the performed calculations, the dependences of the maximum amplitudes of the displacement harmonics at super- and subharmonic resonances on the point of application of the exciting force were determined. It is shown in the paper that the degree of nonlinearity of the vibrating process is strongly dependent on the point of application of the exciting force. As is staled by the author, that the shape of the cross-section does not practically influence the regularities in the variation of the ratio of the dominant harmonic amplitudes with the point of application of the exciting force, and the behavior of the dependence is defined by the resonance mode.
Authors and Affiliations
Yevgen Synenko
Keywords
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