A robust approach for analysing dispersion of elastic waves in an orthotropic cylindrical shell

Dispersion of elastic waves in a thin orthotropic cylindrical shell is considered, within the framework of classical 2D Kirchhoff-Love theory. In contrast to direct multi-parametric analysis of the lowest propagating modes, an alternative robust approach is proposed that simply requires evaluation of the evanescent modes (quasi-static edge effect), which, at leading order, do not depend on vibration frequency. A shortened dispersion relation for the propagating modes is then derived by polynomial division and its accuracy is numerically tested against the full Kirchhoff-Love dispersion relation. It is shown that the same shortened relation may be also obtained from a refined dynamic version of the semi-membrane theory for cylindrical shells. The presented results may be relevant for modelling various types of nanotubes which, according to the latest experimental findings, possess strong material anisotropy

Reduced model for the surface dynamics of a generally anisotropic elastic half-space

Near-surface resonance phenomena often arise in semi-infinite solids. For instance, when a moving load with a speed v close to the surface wave speed vR is applied to the surface of an elastic half-space, it will give rise to a large-amplitude disturbance inversely proportional to v − vR. The latter can be determined by a multiple-scale approach using an extra slow time variable. It has also been shown for isotropic elastic half-spaces that the reduced governing equation thus derived is capable of describing the surface wave contribution even for arbitrary dynamic loading. In this paper, we first derive the analogous evolution equation for a generally anisotropic elastic half-space, and then assess its applicability in the study of travelling waves in a half-space that is coated with a continuous array of spring-like vertical resonators or bonded to an elastic layer of different properties. Our results are validated by comparison with previously known results, and illustrative calculations are carried out for a fibre-reinforced half-space and a coated half-space that is subjected to a finite deformation

The edge bending wave on a plate reinforced by a beam (L).

The edge bending wave on a thin isotropic semi-infinite plate reinforced by a beam is considered within the framework of the classical plate and beam theories. The boundary conditions at the plate edge incorporate both dynamic bending and twisting of the beam. A dispersion relation is derived along with its long-wave approximation. The effect of the problem parameters on the cutoffs of the wave in question is studied asymptotically. The obtained results are compared with calculations for the reinforcement in the form of a strip plate

An edge moving load on an orthotropic plate resting on a Winkler foundation

Steady-state motion of a bending moment along the edge of a semi-infinite orthotropic Kirchhoff plate supported by a Winkler foundation is considered. The analysis of the dispersion relation reveals a local minimum of the phase velocity, coinciding with the value of the group velocity, corresponding to the critical speed of the moving load. In contrast to a free plate, the bending edge wave on an elastically supported plate possesses a cut-off frequency, arising due to the stiffening effect of the foundation. It is shown that the steady-state solution of a moving load problem corresponds to a beam-like edge behaviour. This feature is then confirmed from the specialised parabolic-elliptic formulation, which is oriented to extracting the contribution of the bending edge wave to the overall dynamic response

Dispersion of elastic waves in laminated glass

Elastic sandwich-type structures with high-contrast material and geometrical properties have numerous applications in modern engineering, including, in particular, laminated glass, photovoltaic panels, precipitator plates in gas filters, etc. Multi-parametric modelling of such structures assumes taking into consideration various types of contrast in stiffness, density and thickness. The present contribution is concerned with analysis of low-frequency dispersion of elastic waves in case of an antisymmetric motion of a three-layered symmetric plate, modelling laminated glass. The conditions on material and geometrical parameters, leading to the lowest non-zero thickness shear resonance frequency tending to zero, are formulated. In this case the dispersion relation possesses two low-frequency modes instead of a single fundamental low-frequency mode, which is typical for a homogeneous plate. A two-mode uniform asymptotic approximation is constructed, along with local approximations for the fundamental mode and the first shear harmonic

Dispersion of elastic waves in a strongly inhomogeneous three-layered plate

Elastic wave propagation in a three-layered plate with high-contrast mechanical and geometric properties of the layers is analysed. Four specific types of contrast arising in engineering practice, including the design of stiff and lightweight structures, laminated glass, photovoltaic panels, and electrostatic precipitators in gas filters, are considered. For all of them the cut-off frequency of the first harmonic is close to zero. Two-mode asymptotic polynomial expansions of the Rayleigh-Lamb dispersion relation approximating both the fundamental bending wave and the first harmonic, are derived. It is established that these can be either uniform or composite ones, valid only over non-overlapping vicinities of zero and the lowest cut-off frequencies. The partial differential equations of motion associated with two-mode shortened dispersion relations are also presented