THE SEA OF TWO COUPLED PLATES: AN INVESTIGATION INTO THE EFFECTS OF SUBSYSTEM IRREGULARITY

Abstract A system comprising two edge-coupled plates is considered. Theoretical predictions of the coupling power and coupling loss factor are made using traditional, “asymptotic” SEA wave theory and an analytical wave solution application to rectangular plates. These are compared to numerical frequency averages found by FEA of the complete system. Results are presented for variously shaped plates and different levels of damping. If the damping is large enough (i.e., for “weak” coupling) the response is independent of the shape of the plates. For lighter damping (i.e., “strong” coupling) the response depends significantly on the specific geometry of each plate: the coupling power is often substantially less than that predicted by traditional SEA theory, which also overpredicts the coupling loss factor. Both the coupling power and coupling loss factor are least for rectangular plates, for which the irregularity of the subsystems is least. The reasons for this behaviour are attributed to wave coherence or, in modal terms, to localisation of the global modes of the structure within one or other subsystem. A parameter γ0is given which provides an estimate of the strength of coupling. This parameter arises in the analysis of coupled rectangular plates and gives a conservative estimate for irregularily shaped plates.