Displacement vs Frequency graph for Natural Frequencies, could you help me ?

Altair Forum User

Hello experts,

I have question conserning the simulation of the natural frequencies and after that the ploting of displacement (nodes) vs frequencies.

So I have done a normal modes simulation, just by creating a constrains and EIGRL Load Collector and a Load Step ( type: normal modes, Spc for constrains and modal struct for EIGRL). For the EIGRL I choose ND 6 ( for 6 modes) an V2 1000 ( up to 1000 HZ). So far is everything ok, I can see all F1,F2,F3 in HyperView, the body vibrates und it works good.

But now I want to pick up a node and to plot its displacement against frequency. So first I created a entity of set, called it SETS (with a node , which I selected). After that I clicked on Analysis --> Control Cards and choose Global_Output_Request. For Form(1) I choose both, and for Option (1) I choose SID and after that the SETS (with the node). What I am doing wrong? I can't get the plot after simulating? The only thing I want is a natural frequency (for example mode F1 ) vs Displacement of the node?

Thank you!

Regards

Ivan

Altair Forum User

A normal modes analysis provides only the eigenvalue/eigenfrequencies. 'displacement' is not an available analysis result.

Regards

Altair Forum User

Hello,

Hmmm, some additional hints.

I get a contour plot called EIGEN MODE (v) and i think this are the normalized eigen vectors. You never get real displacements, but normalized.

My suggestion:

- Switch the animation type to transient (animation toolbar)

- Switch on a contour plot EIGEN MODE

- Create a measure group of type Nodal Contour

- pick your node / nodes (the results a always present for all nodes)

- create a curve (Y=Value), new plot

Now you have a plot of Y=displacement, X=Loadcase = Frequency (you have to change this in frequencies if you need, in curve, manually i think)

Regards,

Mario