Dissipation of wave energy in a viscoelastic junction between elastic bars: Dependence on transmission direction

Dissipation, reflection and transmission of an incident extensional wave and its energy at a non-uniform viscoelastic junction between two equal and collinear elastic bars are considered. In particular, the dependence of the energy dissipation, reflection and transmission coefficients on the transmission direction has been studied theoretically and experimentally. With the use of a 1-D linear model it is shown that the dissipated energy, and the reflected wave and its energy, generally depend on the transmission direction, while in contrast, the transmitted wave and its energy, as a manifestation of reciprocity, do not. Significant differences between the dissipated energies, and between the reflected waves and their energies, for the two transmission directions were obtained experimentally for four non-symmetric junctions. Good agreements were obtained between the corresponding transmitted waves and their energies for the two transmission directions. The bars used in the experimental tests were made of steel, and the junctions consisted of segments of polypropylene, high density polyethylene and polymethyl methacryalate between end segments of aluminium. For a junction made of polymethyl methacryalate and aluminium, numerical simulations were carried out and fair agreement was obtained with the experimental results. (C) 1997 Academic Press Limited.