What are advantages of running free free modal analysis?
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Hi,
Free-Free analysis = Free Constraints and Free Loads. A rigid body “in space” should have 3translational and 3rotational degrees of freedom. That’s why you should have the six first rigid body modes frequencies equal or near to zero (if no other mechanism has been intentionnally defined).
If the 7th mode have a frequency equal/or near to zero then you should check the connectivity of the nodes of your model.
In your case the 6th mode frequency is about 2.15. Try
to animate this mode to see how the structure behaves. One of the six rigid body modes is not free.
If you are running the free-free modal analysis just to check the FEM then having the first six rigid body modes frequencies near to zero is enough to overview the model connectivity. Note that Free-Free analysis is one of the several methods we generally use to check the FEM.
If possible drop your model and we'll take a look.
Free-Free analysis = Free Constraints and Free Loads. A rigid body “in space” should have 3translational and 3rotational degrees of freedom. That’s why you should have the six first rigid body modes frequencies equal or near to zero (if no other mechanism has been intentionnally defined).
If the 7th mode have a frequency equal/or near to zero then you should check the connectivity of the nodes of your model.
In your case the 6th mode frequency is about 2.15. Try
to animate this mode to see how the structure behaves. One of the six rigid body modes is not free.
If you are running the free-free modal analysis just to check the FEM then having the first six rigid body modes frequencies near to zero is enough to overview the model connectivity. Note that Free-Free analysis is one of the several methods we generally use to check the FEM.
If possible drop your model and we'll take a look.
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Answer:
In general in finite element analysis modal analysis is conducted in two methods one is free free analysis were first six frequencies will be almost zero from seventh onwards natural frequency value will be obtained in constrained method the first frequency will be having value, in practical in machine tool application eg base of machine tool it is constrained to ground therefore analysis should be with constraints (that is what I feel correct me if I am wrong) then why free free analysis results are required.
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