Steady State Dynamics, Modal. Set a constant displacement at the first resonance

[ThijsMas]

Hi all,

I want to model something that is not completely straightforward to me.

First I've conducted a frequency analysis of my part. Next, I perform a Steady State Dynamic, Modal analysis to construct FRF's of my system. I want to be able to specify the displacement at the first resonant frequency. The harmonic input force should thus be modified accordingly. If I understand correctly I can only apply a harmonic force in this step. The amplitude of this force is unknown beforehand.

Does anyone have experience using this type of analysis and do you have any tips on how to solve my problem?

If you're interested in my goal:
I'm modelling a composite plate with a crack. I can modify the crack length in my part and run the simulation multiple times. The crack length will influence the stiffness of the system and thus its modal characteristics. The FRF components will shift. By setting the displacements at the first resonance constant, the stresses and strains will be of the same order of magnitude for that specific frequency.


Thijs

 

[FEA way]

Mode based SSD analysis can solve at natural frequencies, just select the "Modal: Use eigenfrequencies to subdivide each frequency range" option in step settings. In this type of analysis you can’t specify nonzero BCs directly but you can use displacement type base motion.

 

[ThijsMas]

As I understand it describing a base motion is not what I want.

What I want, is to define the displacement amplitude output of one unique node, and solve the problem backwards. My input force will thus change accordingly