Structural health monitoring and Propagation of lamb waves to identification of crack

The paper presents the Structural health monitoring and the propagation of lamb wave and application to crack identification. The use of lamb waves or plate waves for crack detection is effective due to their long propagation range. Lamb waves are guided waves that can be generated in materials having thickness of the order of a few wavelengths Infinite number of modes are associated with a given plate wave problem. Lamb waves propagate through the thickness of the plate[1], and have complex vibrational patterns. The propagation of lamb waves depends on: operating frequency, material thickness, and density and elastic properties of the material. Different modes occur when the frequency and wave entry angle is varied. The basic modes are Symmetric (S) and Antisymmetric (A) modes. In Symmetric mode, the wave appears to be stretching and compressing the plate in wave motion direction. This mode can be efficiently produced when the exciting force is parallel to the plate. Antisymmetric (A) mode of the lamb waves is also known as flexural mode. Here most of the particle vibration takes place perpendicular to the plate. (C) 2015 Elsevier Ltd. All rights reserved.