The static deflection method can be used for estimating the fundamental frequency of a grounded dynamic system. A 1 G body load is applied to the system for this analysis.
The method can be used as a “ballpark” check for finite element models in conjunction with modal analysis.
Here is a tutorial paper.
The paper also demonstrates the use of the static deflection shape as the starting vector for the inverse power iteration method for obtaining a better estimate of the fundamental frequency.
Matlab script: inverse_power_iteration_manual.m
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– Tom Irvine