A reverse time migration-based multistep angular spectrum approach for ultrasonic imaging of specimens with irregular...

Area of Science:

• Materials Science
• Non-Destructive Testing
• Ultrasonic Imaging

Background:

• Non-destructive testing (NDT) is crucial for evaluating material integrity.
• Imaging internal defects in specimens with irregular surfaces presents significant challenges.
• Existing methods like total focusing methods (TFM) have limitations in contrast and efficiency.

Purpose of the Study:

• To develop and validate a novel ultrasonic imaging framework for NDT of immersed specimens with irregular surfaces.
• To accurately depict multiple hidden damages and their lower surfaces within such specimens.
• To enhance computational efficiency and imaging contrast compared to conventional techniques.

Main Methods:

• A multistep angular spectrum approach (ASA) was employed for forward and backward wavefield propagation.
• Reverse time migration (RTM) with a zero-lag cross-correlation imaging condition was applied.
• The framework was validated through numerical simulations and experimental characterization of aluminum blocks with artificial defects.

Main Results:

• The framework successfully visualized multiple side-drilled holes (simulating damages) in aluminum blocks with irregular surfaces.
• Accurate localization of individual damages and precise imaging of their lower surfaces were achieved.
• The proposed RTM-based algorithm effectively utilized wave reflections for improved imaging.

Conclusions:

• The developed ultrasonic imaging framework accurately detects and characterizes multiple hidden damages in specimens with irregular surfaces.
• The method offers improved computational efficiency and imaging contrast over existing NDT techniques.
• This approach advances the capability of ultrasonic NDT for complex geometries and internal defect assessment.