Harmonic response in Algor 1

[GGuillaume]

I'm pretty new to Algor (with the linear dynamics extender), on which I've spent a few weeks.I easily got used to modal analysis and had good results.
I'm now trying to apply a pair of harmonic forces which frequency is a natural one.

I want to set the amplitude of the forces and a damping in the model in order to get the displacements.
The tutorial explains how to excite a few nodes, but it seems not possible to create a set of several nodes, or to excite directly a surface.

Actually, and according to the tech support, I have to create as many node sets as the number of excited nodes...

The worst is I have to write on a paper all the numbers of the excited nodes....
About 100 in my case... This really sucks.
If some people have allready experienced the same problem, contact the tech service in order to make'em do a "RCP" ASAP!!

If someone has found a tip related to this...

 

[GBor]

I'm a little "old school" here, but let me throw some things out and see if they help:

First, I'm assuming you are performing a "Frequency Response" analysis. With this type of analysis, there are several ways to apply the forcing function. One of them is defining the various node sets, but there is also a way to input the load at any location with a boundary condition. For this, when you are setting up the analysis, you select the "Base Acceleration Mode". With "Base Acceleration Mode", you don't have to input specific nodes...it applies the forcing function to all nodes having a boundary condition. For this type of analysis, "base acceleration mode" has generally been pretty helpful.

If your situation does not allow this, post a little more detail about your model...there may be a better way.

Garland E. Borowski, PE
Borowski Engineering & Analytical Services, Inc.

http://www.borowskiengineering.com

 

[GGuillaume]

Hi Gbor,

First, thanks for your answer,

Your assumption's right : I'm performing a frequency response analysis since i'm not interrested in transient effects.
I've tried "the base acceleration mode", unfortunately, I get an error message which says "ground excitation force is not avalaible".
This is very frustrating, given the fact that we've got the linear dynamics extender...

Here's more details about my model:
The pair of forces I want to apply replaces the effect of a piezoelectric stack that is subject to an electrical excitation (a sinusoidal voltage applied on opposed surfaces that provides a harmonic movement). The frequency of the applied voltage(and also the force) matches one of the resonant frequency.

I hope someone can help me solve this problem...
Thanks in advance

 

[GBor]

To what are you applying the force and how are you scanning for the node numbers?

I'm not sure why you are getting the "ground excitation force not available" error, but one way to stop from having to write down all of the node numbers would be to "check" your model and then in the "Display Options" of FEMPRO's post-processor, select "Show Node Numbers". You can then print screen shots from different angles as needed.

Garland E. Borowski, PE
Borowski Engineering & Analytical Services, Inc.

http://www.borowskiengineering.com