Recent Advances of the Use Of Lamb Waves for Material Characterization

Abstract

In recent years Lamb waves have been successfully used for detecting defects in homogeneous metal plates, coated plates, and multi-layered composite plates. Different Lamb modes generate various stress and displacement profiles in the plate. These stress and displacement components are altered by the internal defects, and thus the defects are detected. All Lamb modes are not equally sensitive to a particular defect. A number of studies have been carried out to identify which Lamb mode is most effective for detecting a defect at a specific location of the plate. Superiority of the Lamb wave inspection technique compared to the conventional ultrasonic technique using P-waves has been established. The overwhelming success of the Lamb wave inspection technique for metal and composite plate inspection has encouraged Kundu and his coworkers to investigate its applicability for some new problems. The new applications include internal defect detection in metal pipes, concrete beams, as well as some new applications in composite plate inspection. One such new application is to generate the “Near-Lamb Mode Image” of a multi-layered composite plate, instead of the “Lamb Mode Image”. Advantage of the ”Near-Lamb Mode Image” is that it can distinguish between the layers of mirror symmetry in a composite plate. The pipe inspection has been carried out by the higherorder non-axisymmetric flexural modes instead of the commonly used longitudinal and torsional modes. A brief review of these recent advances of the Lamb wave inspection technique is presented in this paper.