MODAL ANALYSIS
To realise a modal analysis using a finite element code there are some parameters to define:
Computation method: Lanczos in most practical cases.
Frequency range
Normalisation method
Mass: the most usual, minimise computational and storing requirements
{Φ}T[M]{Φ}=[I]
Maximum: Equals to 1 the largest displacement
Point: Choose a displacement component at which the value is always +1 or -1.
Modal displacements, stresses, etc are relative values, but are useful to identify problematic zones.
Strain energy indicates the location of large elastic deformation (energy), changing the properties of these elements should have more effect on natural frequency and mode shape.