Lamb wave scattering analysis for reflector characterization

Abstract

The potential use of guided waves for defect characterization is studied. The influence of defect shape and size on transmitted and reflected fields is considered. Using the hybrid boundary element technique, the reflection and transmission coefficients for selected guided wave modes are numerically calculated and compared to experimental data. Selecting the aspect ratio as a shape parameter for various defects, the transmission and reflection coefficients are measured for certain guided wave modes input to the defect. The influence of defect size is then studied by monitoring the transmission and reflection coefficients for defects of various shapes and depths. The studies presented indicate that defect characterization is possible if a proper mode selection criteria can be established. The suitable features related to transmission and reflection coefficient data can also be used for algorithm development and implementation purposes of defect characterization.

Reflection and transmission of Lamb waves at an imperfect joint of plates

“…Investigations reported so far include Lamb wave interaction with free and fixed edges [22][23][24][25] and various types of defects. [26][27][28][29][30][31][32][33][34] Lamb wave transmission through a strip weld has been analyzed by Al-Nassar et al 35 and Predoi and Rousseau. 36 To the best of the present authors' knowledge, however, the corresponding issue for a spring-type joint of plates has not been explored in the foregoing literature in spite of its importance in clarifying the physical background to evaluate closed defects in thin-walled structures.…”

Second-harmonic generation of the lowest-order antisymmetric Lamb wave at a closed parallel crack

“…To confirm this, the eigenfrequency analysis is performed using Comsol Multiphysics for a segment of plate of the length 4d containing the thin layer as shown in Fig. 5 in Fig. 6 for the three lowest eigenfrequencies.…”

“…1,2 The scattering characteristics of Lamb waves by different types of defects in plates have been studied by a number of investigators. [3][4][5][6][7][8][9][10][11] Among others, Rokhlin 3,4 analyzed the Lamb wave scattering by a finite crack parallel to the surfaces of an elastic plate and the associated resonant behavior due to the multiple reflection at two ends of the crack. The Lamb wave scattering characteristics of perpendicular cracks as well as notches were analyzed by Castaings et al, 7 Lowe and Diligent, 8 Lowe et al, 9 and Flores-L opez and Gregory.…”

Applications of Piezoelectric Materials in Structural Health Monitoring and Repair: Selected Research Examples

“…However, they could not fully model the piezoelectric effects in their models. Some recent progresses were contributed by the FE method [101,102], the boundary element method [21,103,104,105,106], finite difference method [107,108,109] and time-reversal of ultrasonic fields [110,111]. FE method has the advantage in modeling the complicated electrical and mechanical boundary conditions of IDT, and eliminates the need for lengthy analytical solution [112].…”