Flexural Wave Control Using a Far Field Adaptive Vibration Neutraliser

The subject of this paper is the control of flexural waves on an infinite beam using a vibration neutraliser located in the far field of a forcing input. The neutraliser analytical model consists of a beam carrying three concentrated masses that can be further simplified to a mass-spring-mass system given the system symmetry. Depending on the input frequency, position and value of the masses, the neutraliser can be tuned either to maximise the power reflection or the power absorption. The bandwidth of attenuation is limited so the neutraliser may become ineffective when the forcing frequency changes. To overcome this limitation, shape memory alloy wires are used to design an adaptive beam neutraliser. The wires, made of a Nitinol alloy, exhibit a change with temperature in the elastic modulus of the material caused by a lattice structure reorganisation. This property allows adaptive tuning for different input frequencies via flexural rigidity variation. A preliminary design of the neutraliser is proposed. Analytical and experimental data are compared to assess the validity of the model.