Detection of Defects in a Plate Using Rayleigh-Lamb Waves

Nondestructive testing of materials is essential wherever they are used in safety critical applications. Conventional ultrasonic techniques, such as C-scanning, generally use waves propagating normal to the plane surface. While accurate, such methods are slow for structures with large plane areas. The use of longitudinal waves offers the possibility of quicker testing of such structures. This paper considers the reflection of low frequency Rayleigh-Lamb waves by a two dimensional, centrally embedded vertical defect in aluminium plate. A numerical method is used, based on results from dimensionless analytical work. It is shown that such longitudinal ultrasonic waves can successfully detect structural defects.