ABSTRACT
This chapter explores the theoretical background for such inspection, lists advantages of the guided wave inspection technique over conventional ultrasonic techniques, and presents results from a number of plate and pipe inspection experiments. A wave-guide is a structure with boundaries and/or interfaces that help elastic waves to propagate from one point to another. An elastic wave that propagates through a wave-guide is called a guided wave. Like Lamb waves, the guided waves through a rectangular bar or a cylindrical rod also show multiple modes and the wave speeds for these modes are generally dispersive. The chapter discusses Lamb wave propagation in a plate, which is in a vacuum or immersed in a fluid, has been studied by decomposing the particle motions into their symmetric and anti-symmetric components. Elastic waves can propagate in axial and circumferential directions of a pipe, or at an angle other than 90° relative to the axial direction.
