| ABSTRACT: | REFLECTION AND TRANSMISSION OF LAMB WAVES AT DISCONTINUITY IN PLATE
Z.Liu, NDT Systems & Services AG, Stutensee, Germany
Lamb waves are usually used for testing large and thin plate because they provide great potential for
improving inspection efficiency and sensitivity. In this paper, numeric analysis implemented by boundary
element methods (BEM) and the normal mode expansion technique is used to study the Lamb wave
reflection and transmission coefficients at discontinuity in plate. It is considered the interaction of Lamb
waves with two basic discontinuitiesÑ thickness step and thickness incline. Interaction of individual Lamb
wave modes with discontinuity in a plate is investigated by calculating the reflection and transmission
coefficients for varying incident Lamb wave modes, frequency, and discontinuity shape. A0 and S0 Lamb
mode in aluminium plate incident at frequency to 1.5 MHz, the plate thickness variation from 0.5 mm to 2.0
mm and incline angle from 0¡ to 75¡ at the point of discontinuity are considered. The mode conversion
phenomena through step and incline discontinuity in a plate are also given. Results in this paper can be used
to improve inspection sensitivity and penetration power for a variety of practical NDE applications, notably
those in which thickness variation is found.
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