Determination of optimal sample thickness and positions of transducer for the effective Higher Order Mode Cluster-guided wave generation

Higher Order Mode Cluster (HOMC) guided waves (GW) have recently been proposed for ultrasonic testing of plates and pipes. The incident wave through the plastic wedge generates the HOMC-GW. A propagated distance, namely the HOMC formation field, is necessary to create the wave signal. Unfortunately, the HOMC wave is unstable in the formation region, which needs a longer distance for stability. This research examines the effect of sample thickness on the HOMC generation process. ABAQUS CAE simulated the HOMC generation in various samples with different thicknesses, such as 6, 7, 10, 15, and 20 mm. The results show that HOMC stability was achieved at a shorter distance in the smaller sample (6 mm) compared to the larger sample (20 mm). Moreover, the ABAQUS-Explicit 2D-FEA model was used for notch detection in a mild steel sample based on the HOMC status. The result shows that the transducer’s strength decreases along the formation regions, and the reflected amplitude becomes more robust when it reaches the stable region. When it travels further, the amplitude gets weaker due to the reduction in its energy. The experimental study was conducted similarly to the 2D-FEA model to compare the simulation and experimental results. The empirical findings show good agreement with the simulation results throughout notch detection. The precise distance required for the HOMC wave to become stable was determined via this work, optimizing the selection and employment of single modes.