MODELLING THE VIBRATION BEHAVIOUR OF INFINITE STRUCTURES BY FEM

In vibration power flow analysis, often the vibration behaviour of infinitestructures is required. The modelling of infinite structures using the finite elementmethod has been discussed. By considering the impedance of a finite beam andfinite plate, theoretical formulae for a spring–damper combination to match theseimpedances are derived. Examples are given for a rather short (200 mm) beam anda small (400 mm diameter) plate with spring–dampers applied to the edges of thestructures using the finite element method. Results of the driving point mobilityindicate that these finite structures simulate an infinite beam and an infinite platevery well. Furthermore, the surface mobility of an infinite plate over a squarecontact area subject to a uniform conphase force excitation has been calculatedsuccessfully using just under 8 times fewer elements than a previous study.