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-   -   Eigenfrequencies static and modal analysis (http://www.cfd-online.com/Forums/ansys/101737-eigenfrequencies-static-modal-analysis.html)

Laura_mecheng May 12, 2012 18:25

Eigenfrequencies static and modal analysis
 
Hello,

I am doing an ANSYS analysis and now I don't understand something. The construction I am analyzing is a goal (like from soccer) and in the middle a force of 1000 N is applied. First I did a static analysis and calculated the natural frequency with √ (k/m)/(2∏).
Where k is the stiffness and described by F/δ_middle so δ_middle is defined where the force is applied and therefore the maximum deflection.

After that I did a modal analysis and calculated the first 5 eigenfrequencies. The first eigenfrequency is now around two times higher as the frequency calculated with the static analysis.

Where does this difference come from? So the difference between the natural frequency calculated with the static analysis and the first eigenfrequency calculated with the modal analysis.

What is exactly the difference between the static and dynamic calculation in ANSYS? With statics it does not take mass and accelerations into account I think but I don't see how this exactly works in ANSYS.

Thanks for helping in advance :).

Laura_mecheng May 15, 2012 03:40

Anyone? :)


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