Research for Evaluation Method Based on Lamb Waves for Thickness of Ship Deck Beams

As the main force component of contemporary ships, the ship deck beam is of great significance and needs to be maintained regularly under the severe conditions of long-term complicated external loads form waves. The maintenance methods are usually related with the thickness of the beams. Due to the limited detecting methods, the thickness of beams cannot be evaluated accurately when maintaining. Therefore, in this paper, a detecting method based on active Lamb waves is proposed, which could evaluate the thickness of beams. On one hand, the two-dimension (2D) finite element simulation model of beams is established and the ability of three damage indexes of A0 mode signal at beams with different thickness is studied. On the other hand, experiments are carried out. To suppress measurement noise effectively, variational mode decomposition (VMD) is used to extract experimental signal feature parameters and the three damage indexes are also used to evaluate the thickness of beams. The experimental results show that the variation trend of the three damage indexes is consistent with the simulation results. Moreover, the damage index with the energy of the scatter signal based on the A0 mode has a better ability for the beams thickness. Thus, this method is proved to be feasible to evaluate beams with different thickness.