Development of the NDIF Method Based on the Sub-domain Method to Overcome the Non-extraction Problem of Low-order Eigenvalues for Concave Membranes: Part 2(Example Studies and Considerations)

The first part of this paper proposed a theoretical formulation of an improved NDIF method designed to overcome the issue of non-extraction of low-order eigenvalues in the NDIF method when applied to the sub-domain method. The validity of the proposed formulation was confirmed using membranes of simple geometries. In this second part of the paper, example studies are conducted on concave membranes with various shapes, including V-shaped, L-shaped, and concave circular membranes, in order to verify the validity and accuracy of the NDIF method theory presented in Part 1.