Wave propagation in stiffened plate systems has been analyzed with a finite element technique. This technique is shown to provide an effective tool for the analysis of mechanical waves propagating in waveguide systems built-up of thin-walled plate elements. The method has been used to calculate dispersion curves for waves propagating in geometries typical of ship hulls. The associated mode shapes are also calulated. It is shown that the flexural waves in such structures can be divided into three groups with respect to which parts of the structure determine the wavenumbers accociated with the waves. The first two groups of waves propagate energy either predominantly in the plate elements or in the stiffeners. The propagation constants of the modes in the first and the second groups can thus be determined from the properties of the base plate and the stiffening ribs respectively, treated as separate structural members. For the third group of modes, the rib-stiffeners deflect with the base-plate of the structure. These modes are referred to as structurally stiff in a frequency region just above cut-on. The frequency span for which a mode can be considered stiff varies. In the frequency region investigated, there are modes with stiff characteristics at practically all frequencies. Below the cut-on frequency of the first plate mode, only stiff modes propagate energy. In this frequency region the caluclated wavenumbers compare well with those determined by so-called equivalent plate theory, for which the plating is represented by an equivalent orthotropic plate with properties calclulated from the built-up system. However, also at higher frequencies at which plate modes are cut-on, stiff modes may propagate energy. Equivalent plate theory also gives reasonable estimates of the wavenumbers in the stiff region of the modes at high frequencies.
Calculation of wave propagation in rib-stiffened plate structures
Berechnung der Wellenausbreitung in rippenverstärkten Plattenstrukturen
Journal of Sound and Vibration ; 198 , 2 ; 203-224
1996
22 Seiten, 14 Bilder, 2 Tabellen, 14 Quellen
Aufsatz (Zeitschrift)
Englisch
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