Dear Joseph,

thanks for your answer. It`s very informative, but I need something different.

In finite element analysis of structures in some cases largest eigenvalues are considered, and sometimes smallest ones are considered. I just wonder in which cases largest eigenvalues are important/required, and in which cases smallest ones are important/required.

This thread might help you.

https://www.researchgate.net/post/Eigenvalues_in_FEM

Dear Mahdi,

thank you for your suggestion, but the question and all answers are about positivity and negativity of eigenvalues, so not of much help.

Thank you dear Hassan, that`s exactly what I needed for the largest eigenvalues.

In addition to the above by Hassan Sarmadi, another use of eigen parameters is to use it to build the stiffness matrix K or the flexibility matrix F of the structure. If you have few of the highest frequency mode shapes, you can create a fairly accurate K matrix. If you have few of the lowest frequency mode shapes, you can create a fairly accurate F matrix. If you have all the mode shapes, you can create the K and F matrices accurately.

regards,

Rahul Leslie