A Viterbi-Based Ray Tracing Technique for Ultrasonic Linear Array Imaging of L-Shaped CFRP Structures

The aerospace industry extensively utilizes carbon fiber-reinforced plastic (CFRP) materials due to their high strength and low density. A reliable non-destructive testing technology that can efficiently measure and detect internal flaws, such as delamination, in the L-shaped structure of CFRP material is crucial to ensure the safety and reliability of aircraft structures. While conventional ultrasonic testing has limited efficiency, array ultrasonic full-focus imaging detection technology depends on precise sound propagation delay. To address the challenge of calculating sound wave delay caused by anisotropy and multi-layer refractive interfaces within the CFRP materials, a sound ray tracing technique employing the “Viterbi search algorithm” is proposed. This technique is employed to compute the time delay of array ultrasonic full-focus imaging detection. The heuristic delay-and-sum beamforming Total Focusing Method (TFM) is selected to generate a fully focused image of the L-shaped CFRP structure. The TFM imaging prerequisite is to compute ultrasonic ray paths that are challenging due to the multilayered structure, elastic anisotropy, and curved geometry. The results of this study would prove beneficial in enhancing testing methods and guiding accurate imaging procedures based on the TFM method.