Sahil Sura
Ansys Employee

Hi Weihan Lin,
Since the material, I'm assuming is used in the analysis is a nonlinear material, it might be a bit difficult to converge at first using the default settings, thus it would be a good idea to converge the static structural system in a standalone way to get the required plots and then link it to the modal system.
You can turn on the Large deflection in the static structural system and also consider the Auto time-stepping option and define the adequate amount of timesteps or substeps to help the model get converged.
Also, note that the modal analysis is a subset of the Linear Dynamic Analyses, and as the name suggests the nonlinearities will be invalidated in the same, so please find the following video which helps to solve the Pre-stressed Modal Analysis.
How To Perform Prestressed Modal Analysis — Lesson 2 - ANSYS Innovation Courses 

Hope this helps!



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