WAVE PROPAGATION, REFLECTION AND TRANSMISSION IN TUNABLE FLUID-FILLED BEAMS

This paper concerns wave motion in tunable fluid-filled beams. The beams comprise two elastic faceplates with a central core of tunable fluid such as electro-rheological or magneto-rheological fluid. Free wave propagation is considered and three wave modes are seen to exist. The corresponding wavenumbers depend on the viscoelastic properties of the tunable fluid, which in turn depend on the field applied to the fluid. Consequently, the wavenumbers can be controlled. A systematic technique for describing wave transmission and reflection in one-dimensional waveguides is described. This involves transformations between wave amplitudes and waveguide displacements and internal forces. Expressions are derived which describe wave reflection at a boundary, reflection and transmission at a change in section and reflection and transmission at an attachment. Numerical results are presented for electro-rheological fluid-filled beams and the junction between such a beam and an Euler–Bernoulli beam. The reflection and transmission coefficients also depend on the applied field so that the transmission characteristics are tunable.