Operational Deflection Shapes ODS

Hey all!

I'd like to enhance the investigation of the resonances of a mechanical system model incluing flexibles structures. Is it possible to extract operational deflection shapes from the System after the simulation using the Adams PPT? Or should I stop the Simulation at a certain time step(system state) and do a linear mode analysis?

What are your thoughts on this?

Kind Regards

Nils

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0 Kent West over 7 years ago
Hi Nils,

A Solver simulation script for this would look something like this:

sim/dyn, end=5, dtout=0.01 ! Get model into position

deactivate/joint, id=44 ! Remove that pesky joint..

sim/init ! or sim/static Need to do some kind of sim before the linear..

linear/eigen ! produces the 'normal modes' that I think you want.

You might not need to do the sim/init, but consider this:

after you deactivate the joints/forces your model is no longer in a feasible configuration. It *was* in a solution configuration, but now you've changed it. So Solver must do some kind of analysis (static, dynamic or just initialization) to get into some kind of feasible configuration before the linear analysis. You typically have to think about this: do you want a static analysis at that point or a short dynamic? Basically what happens to the real system after you've deactivated things?

HTH,

Kent
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0 Kent West over 7 years ago
Hi Nils,

A Solver simulation script for this would look something like this:

sim/dyn, end=5, dtout=0.01 ! Get model into position

deactivate/joint, id=44 ! Remove that pesky joint..

sim/init ! or sim/static Need to do some kind of sim before the linear..

linear/eigen ! produces the 'normal modes' that I think you want.

You might not need to do the sim/init, but consider this:

after you deactivate the joints/forces your model is no longer in a feasible configuration. It *was* in a solution configuration, but now you've changed it. So Solver must do some kind of analysis (static, dynamic or just initialization) to get into some kind of feasible configuration before the linear analysis. You typically have to think about this: do you want a static analysis at that point or a short dynamic? Basically what happens to the real system after you've deactivated things?

HTH,

Kent
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