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Interpreting modal analysis

Altair Forum User

Hi,

I have a model with 3 components and 3 different materials, all combined as a blade. When I do modal analysis, I end up with 15 near-zero modes. Is this normal? If so, what is the frequency of my model as a whole then, because I would be finding values from the components only and not the combined model?

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Altair Forum User

Hi @sch

Can you check the connectivity between the three components?

If all the components are connected, it will act as a single part and should have 6 rigid modes.

I am attaching a file for your reference.

Unable to find an attachment - read this blog

Altair Forum User

Great I connected the components and it worked. However, my modal analysis gives me a natural frequency of over 100 Hz for the first mode (see attached). I used a freeze contact to connect the inner rod to the foam. Are the frequencies so high because of my choice of contact surface or because of my materials?

Unable to find an attachment - read this blog

gopal_rathore

Hi,

The frequency of the system depends on the mass and the stiffness of the system. Based on the type of contact, contact stiffness will vary in an assembly of components and thus will have an effect on frequency and needs to be verified how significant it is.

Also are you having a constraint model or performing a free free run. As in real life the system is constrained, the modal analysis can be performed by assigning constraints.