A monopole-dipole resonator for flexural waves in a rod

For flexural waves in a rod, a simplest resonator responding not only displacements but also to the inclination (the derivative of the displacement) of the rod axis is studied. The resonator consists of two springmass systems attached through a rigid (nonbending) bar to the elastic rod in which a flexural wave propagates. One of the springs is oriented perpendicularly to the rod, and the other is parallel to it. It is shown that, at a certain friction, the single monopole-dipole resonator under consideration completely absorbs the incident resonance-frequency flexural wave, which propagates in the elastic rod.