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Interpreting Complex Modes As A Wave Propagation Phenomenon
Registro en:
9073802725; 9789073802728
Proceedings Of The 25th International Conference On Noise And Vibration Engineering, Isma. , v. , n. , p. 597 - 604, 2000.
2-s2.0-13444301002
Autor
Ahmida K.M.
Arruda J.R.F.
Institución
Resumen
In this paper it is shown how complex modes can result from wave propagation phenomena (geometric damping). Four simple examples of straight, homogeneous beam structures are used to illustrate the discussion: a finite clamped-free beam, an infinite beam with a discontinuity in mass and stiffness replacing the clamp, a semi infinite beam, and an infinite beam. The system input/output transfer relations are all obtained using a spectral formulation known as the Spectral Element Method (SEM) which is able to model infinite structures using a throw-off element. Using a mode complexity coefficient which consists of the correlation coefficient of the mode shape plot in the complex plane, it is shown that the clamped-free beam has a unitary complexity coefficient (purely reverberant, normal mode) while the infinite beam has a zero coefficient (a circle in the complex plane, no mode exists). The other two structures present an intermediary situation where complex modes exist and have complexity coefficients between zero and one.
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