Health Monitoring of Plate Structures Based on Tomography With Combination of Guided Wave Transmission and Reflection

Corrosion and damage occurring in the metallic structure threaten the normal operation of instruments and systems. Timely inspection of corresponding components are quite significant to spot the damages. The ultrasonic guided wave inspection technique has become a powerful solution to quantify and image the structural defect. This work proposes a novel tomography scheme to comprehensively utilize guided wave transmission and reflection, which facilitates the imaging performance. To achieve this goal, the disperse Lamb wave is adopted and omni-directional electromagnetic acoustic transducer is introduced. The bent acoustic ray model forms the base of the proposed method. The acoustic paths are obtained by the ray tracing technique according to the time of flight of received transmission wave and reflection wave. Further, the slowness distribution is reconstructed and it can be transformed to the thickness distribution. The case from simulation firstly validates the feasibility of this proposed method. In addition, the complicated case is set in the experimental section and the comparison with tomography from only transmission wave is conducted. The quantitative merits are also designed to measure the depth error and global error. The results of comparisons demonstrate the superiority of proposed scheme. Therefore, this scheme could be an alternative approach for better damage reconstruction.