Wave beaming and wave propagation in light weight plates with truss-like cores

Abstract

Wave propagation in light weight plates with truss-like cores is investigated. For generic light weight plates with periodicity in one dimension the wavenumber content is characterized by strong directional wave propagation. Also wave beaming results in some frequency bands, where local vibrations are of primary concern. The strong periodic pass- and stop-band behaviour detected previously for profile strips is transformed into a spatial stop- and pass-band distribution of high and low vibration zones. As a result, the stop-bands of the two-dimensional investigation are weakened for point excitation of full plates. This is manifested by a rising real part of the input mobilities. In these lateral stop-bands the imparted power is transmitted mainly in the direction parallel to the webs of the inner core. In the low frequency region, where global plate waves dominate, the vibrational behaviour can be reduced to equivalent plate models. For profiles with inclined webs, global orthotropicity is limited and global bending wave dispersion is similar irrespective of direction. For profiles with solely vertical webs, strong orthotropicity with significantly higher wavenumbers in the lateral direction, normal to the webs, is demonstrated. Different methods for the extraction of theoretical and experimental dispersion characteristics of the plates are applied and discussed. The theoretical dispersion characteristics are validated on a regional train floor section which serves as an application example.