Energy Analyses for the Imaging Technique of Bonded Regions and Delaminations in a Thin Plate

Abstract

Defect imaging by a scanning laser source technique has been theoretically and experimentally investigated for a notch and a wall thinning in a plate. This study discusses the applicability of the imaging technique to bonding regions and delaminations in a thin plate. The variations of flexural wave energy generated at a laser source close to a plate edge, a junction of two thin plates, a bonded region, and a delamination are discussed using the Kirchhoff–Love plate theory and a semi-analytical finite element method. The numerical analyses reveal that the flexural wave energy generated in the vicinity of the reflection objects are significantly different in such a source type as normal loading and dipole loading modeled for elastic wave generations due to ablation and thermo-elastic effects, respectively. In particular, the numerical analyses reveal that the dipole loading is more effective to the imaging because the generation energy significantly varies at the boundaries between bonded and separated regions. Moreover, the images of a plate with a bonded region are obtained using an experimental system in which the thermo-elastic effect is dominant for generating elastic waves, and they exhibit similar tendencies with calculated results.