Design of periodic pipes for structural vibration filtering

This paper concerns the design of periodic pipes seen as structural waveguides in which flexural, torsional and longitudinal waves can propagate. To control the propagation of these vibrations and reduce their possible sound borne annoyance, Bragg band gaps e ects can be reached by architecting the variations of the cross section. As a result, the tailored structural waveguide acts as a vibration filter. In industrial contexts, these filters can be used in a complex assembly for decoupling vibroacoustic subsystems. In many practical cases, all kinds of waves usually co-exist because of inevitable structural couplings. As a consequence, optimization of the geometrical and mechanical features of the unit cell has to be performed to mitigate at the same time several kinds of waves. For this purpose, dispersion relations are derived and analyzed based on the Floquet method and numerical Finite Element simulations. Demonstrators of finite size are also studied in order to illustrate the potential for practical applications.