Transition radiation in continua excited by a moving load

Abstract eng:
Transition radiation is emitted when a perturbation moves along a straight line at constant velocity in or near an inhomogeneous medium. Transition radiation of elastic waves is emitted, for example, by train wheels due to track inhomogeneities. Such radiation was analyzed using several 1—D and 2—D elastic systems, but few fundamental studies focus on elastic continua. In this study, we consider a continuum consisting of two elastic layers coupled at a vertical interface. Both layers are in plane strain, have a rigid bottom, and are subject to a load that moves along the upper surface and crosses the layer interface; the upper surface is either stress free or connected to a thin flexible plate. Using semi—analytical solutions, we study the characteristics of the excited free wave fields. Results show peculiar angular distributions of the associated energy flux, which strongly depend on the load velocity and the contrast in material parameters.

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