Wave Propagation in Three-Layered Plates. Application to Ultrasonic Delay Lines

摘要

The propagation of trains of straight crested harmonic waves in infinitely long isotropic, traction free, three-layered plates is investigated on the basis of the three-dimensional linear theory of elasticity. It is established, that as in the case of waves traveling in homogeneous plates, the face shear motion and the longitudinal - flexural motion exist uncoupled. However, independent symmetric and antisymmetric modes exist only in the case of three-layered symmetric plates; that is, plates having identical outer layers. The frequency equations have been evaluated numerically. The possibility is discussed of utilizing thin three-layered symmetric strings as delay media in guided wave ultrasonic delay lines having a linear delay versus frequency relation. (Author)