Affiliation:
1. Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890
Abstract
When a structure deviates from axisymmetry because of circumferentially varying model features, significant changes can occur to its natural frequencies and modes, particularly for the doublet modes that have non-zero nodal diameters and repeated natural frequencies in the limit of axisymmetry. Of technical interest are configurations in which inertia, dissipation, stiffness, or domain features are evenly distributed around the structure. Aside from the well-studied phenomenon of eigenvalue splitting, whereby the natural frequencies of certain doublets split into distinct values, modes of the axisymmetric structure that are precisely harmonic become contaminated with certain additional wavenumbers. From analytical, numerical, and experimental perspectives, this paper investigates spatial modulation of the doublet modes, particularly those retaining repeated natural frequencies for which modulation is most acute. In some cases, modulation can be sufficiently severe that a mode shape will “beat” spatially as harmonics with commensurate wavenumbers combine, just as the superposition of time records having nearly equal frequencies leads to classic temporal beating. An algebraic relation and a diagrammatic method are discussed with a view towards predicting the wavenumbers present in modulated eigenfunctions given the number of nodal diameters in the base mode and the number of equally spaced model features. [S0739-3717(00)01501-4]
Reference25 articles.
1. Zenneck, J.
, 1899, “Ueber die freiea Schwingungen nur anna¨hernd vollkommener kreisformiger Platten,” Ann. Phys. (Leipzig), 67, pp. 165–184.
2. Tobias, S. A.
, 1951, “A Theory of Imperfection for the Vibrations of Elastic Bodies of Revolution,” Engineering,172, pp. 409–411.
3. Tobias, S. A.
, 1958, “Non-linear Forced Vibrations of Circular Disks,” Engineering, 186, pp. 51–56.
4. Thomas, D. L.
, 1974, “Standing Waves in Rotationally Periodic Structures,” J. Sound Vib., 37, pp. 288–290.
5. Thomas, D. L.
, 1979, “Dynamics of Rotationally Periodic Structures,” Int. J. Numer. Methods Eng., 14, pp. 81–102.
Cited by
45 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献