Excitation of normal modes of a thin elastic plate by moving dislocations

TL;DR

This paper analyzes how moving dislocations in thin elastic plates excite specific harmonic wave modes, revealing mode-specific excitations and singular behaviors at certain velocities, advancing understanding of elastic wave phenomena.

Contribution

It introduces a detailed Fourier space analysis of dislocation-induced wave excitation, identifying specific Rayleigh-Lamb modes excited by screw and edge dislocations in thin plates.

Findings

Screw dislocations excite antisymmetric Rayleigh-Lamb modes.

Edge dislocations excite symmetric Rayleigh-Lamb modes and the lowest shear mode.

Singular behavior occurs at dislocation velocities matching mode phase velocities.

Abstract

We study the excitation of harmonic waves in thin elastic samples by a single dislocation in arbitrary motion. We consider both screw and edge dislocations that move perpendicularly to the surfaces of the layer. In Fourier space the displacement velocity and dynamic stress fields generated by the motion of the dislocations are factored as the product of two terms: one depends on the motion of the dislocation only, while the other is independent of it, and represents the medium's response. The latter term exhibits poles at frequencies that satisfy the dispersion relation of the harmonic modes of the plate. In the case of a screw dislocation the modes that are excited are a subfamily of the antisymmetric Rayleigh-Lamb modes. For an edge dislocation a subfamily of the symmetric Rayleigh-Lamb modes is excited, as well as the lowest lying shear mode. The expression corresponding to a uniformly moving screw is worked out in detail; it has singular behavior at velocities coincident with the phase velocities of the allowed modes.