To investigate the dynamic characteristics of local structures in naval architecture and ocean engineering, the dynamic boundary equivalence method between truncated model and original model is proposed.

The finite element method is used to calculate the natural frequencies and vibration modes of the V-shaped plate model with one side elastically supported under free boundary conditions, and the isolated plate model with three sides under free boundary conditions. The natural frequencies and vibration modes of the V-shaped plate model are compared with those of the isolated plate model to investigate the dynamic boundary equivalence of the truncated plate model.

The research shows that with an increase in the thickness of the attached plate, the half-wave number m of the (m, n) order of the main plate of the V-shaped plate is constant along the coupled edge direction, and the half wave number n perpendicular to the coupled edge direction increases; with the increase of the length of the attached plate, the half wave number m of the (m, n) order of V-shaped plates mode is constant along the coupled edge direction, while the half-wave number n perpendicular to the coupled edge direction decreases. When the coupling angle α between the main plate and the attached plate is between 40° and 90°, the attached plate of the V-shaped plate provides a fixed support boundary condition for the main plate.

A fast prediction method for the natural frequency of partial modes of the V-shaped plate is proposed.