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Test.Lab Operational Modal Analysis

Creator
Creator

Hi community,

 

with LMS Test.Lab I created different components (e.g. form1, form2,  ....) with the geometry modul for modal analysis. Then I have done under different sections (section1, section2, ...) some meeasurements.

With the modul: operational modal analysis I load under Op.DataSelection the measurements from the section (e.g. section1).  In geometry display I see all components (e.g. form1, form2, ...). Because I cannot seperate these components, the calculations under Op. Time MDOF are incorrect.

 

Question: On which way I can assign the components (form1, form2, ...) to measurements under the different sections (section1, section2, ...)?

 

Can you help me?

 

Thank you

Berger

 

 

11 REPLIES

Re: Test.Lab Operational Modal Analysis

Siemens Genius Siemens Genius
Siemens Genius

Hello - 

 

I'm not fully understanding your question, but suspect that you may need to load the different measurements from the multiple sections into the processing all at once; to do so, the easiest route is the 'Input Basket'.  Individually add the functions from the various sections by a combination of "Replace" (first time) and then "Add" (second, third, etc.), such that you have a single list of all the measurements that you want to analyze in the Operational Modal.  Then simply change from adding the data from a single section to that temporarily stored in tne Input Basket.

 

If instead you want to analyze only Section1 with GeoPoints1, then your data selection is fine, but of course any points for which you don't have measurement data there will be no displacement.  In that case you could simply use the Component Visibility in the display to turn of the visualization of the components that are not part of the current analysis.

 

Hopefully this helps - 

Jason

Re: Test.Lab Operational Modal Analysis

Creator
Creator

Hi Jason,

 

sorry for the misunderstanding.

 

I have different components, but the coordinates are very similar. Therefore I created with the geometry modul different components (e.g. form1, form2, ...). Each component  (e.g. form1, form2, ...) includes specific measurements, which I saved under a sections (e.g. section1, section2, ...). Each measurement is a part of a very specific component (e.g. section1 and form1, section2 and form2, ....). With the help of the basket the measurement for every section are available for further calculation for the modal analysis. But I can not separate in the same way the individual geometry models (e.g. form1, form2,...) from each other. Under the modal analysis I have the seperated measurement but all geometry models (e.g. form1 + form2 + ....). The nodes within a geometry models (e.g. forma1, form2, ...) are interconnected, but the nodes of different geometry models are not linked. Here is the problem. The program Test.Lab links in the modal analysis program all nodes. Therefore, I have to detach the individual geometry models (e.g. form1, form2)of the overall package (geometry).

 

I hope my observations do not further confused.
 
Berger

Re: Test.Lab Operational Modal Analysis

Siemens Genius Siemens Genius
Siemens Genius

What is the actual 'problem' - the display of the results does not look correct to you?  The calculation of the results is independant of the geometry - that is only used for display purposes.  Do you need to simply deactivate the display of one or more components?

Re: Test.Lab Operational Modal Analysis

Creator
Creator

Hi Jason,

 

for the modal analysis you need a geometry model. Without the geometry you can not calculate a modal analysis. The program has to now where is the accelerometer and where is the hammer. With these inputs and the results of the measurements (FRF, phase) the program calculate the modal analysis and show it on the screen.

 

Berger

 

 

Re: Test.Lab Operational Modal Analysis

Siemens Genius Siemens Genius
Siemens Genius

Agreed and understood - so what is not working for you?  Do your geometry node names exactly match the measurement point ID's?

Re: Test.Lab Operational Modal Analysis

Creator
Creator

Hi Jason,

 

I try to explain.

 

I have 2 component (for example two shafts). Shaft one get the geometry name: form1, shaft two get the geometry name: form2.

The geometry of form1 (shaft 1) has for example the following coordinates (z-direction): 0.15m, 0.25m, .... , 1.45m.

The geometry of form2 (shaft 2) has for example the following coordinates (z-direction): 0.1m, 0.2m, .... , 1.5m.

For the measurement I created two sections: section1, section2.

 

Measurements 1:  With the help of the geometry (form1) together with section1 I use the impact testing measuring module of test.lab to measure every single point (see also layout impact testing / measure).  Every measurement in the section correlates with the nodes of the geometry name: form1

Measurements 2:  With the help of the geometry (form2) together with section2 I use the impact testing measuring module of test.lab to measure every single point (see also layout impact testing / measure).  Every measurement in the section correlates with the nodes of the geometry name: form2

 

After the measurement I  switch to the modal analysis program. With the help of the basket I extract the results of 1st measurements (CrossPower: CSD). When I continue in the program: Op.Data Selection, Op. Data MDOF / Band .../ Stabilization. At the latest from this point, the user notices that the program gives incorrect results. The reason lies in superpositions of the individual geometry models (form1, form2, ...= 0.1m, 0.15m, 0.2m, ..., 1.45m, 1.5m). But for the shaft 1 the following measuring at positions (0.1m,  0.2m, ..., 1.5m = form2) are missing for the program. Therefore the calculations of the program are incorrect!

 

Therefore I have to assign the geometry form1 to section1 and form2 to section2.

 

My question: how does it work?

 

Thanks

Berger

Re: Test.Lab Operational Modal Analysis

Siemens Genius Siemens Genius
Siemens Genius

I think we've gone beyond what can be solved via an exchange of text on this forum - I'll try to verify a couple of things below, but suggest that you call your GTAC support line or contact them at www.siemens.com/gtac.  A direct discussion with a support engineer will likely clear up any confusion very quickly!

 

There is no 'assigning' of geometry to a set of data - the matching of a measurement function to a component is done completely through the naming.  If your geometry / components / nodes look like this:

 

Geometry

    Form1

        1

        2

    Form2

        1

        2

 

Then your measured data needs to be named / formatted with appropriate Primary / Secondary ID's.  As an example, if you impact on shaft one, point one, in the minus Z direction, you'd potentially have two output functions (presuming an accelerometer at points 1 and 2 on Form1 measuring in positive Z):

 

    Form1:1:-Z / Form1:1:+Z

    Form1:1:-Z / Form1:2:+Z

 

 

The primary ID in this case is the hammer input location and direction, and the secondary ID is the accelerometer output location and direction.  If you then independently measure on shaft two, again impacting at point one and measuring at both outputs 1 and 2, your functions should be labeled like this:

 

    Form2:1:-Z / Form2:1:+Z

    Form2:1:-Z / Form2:2:+Z

 

 

Thus when you do the modal analysis, the input / output points, via their primary / secondary ID's, are automatically calculated and animated on the correct geometry in the display.

 

Re: Test.Lab Operational Modal Analysis

Creator
Creator

 

Hi Jason,

in the print screen below you can see two different forms.

LMS.gif

 

How can I hide one of the two?

 

Thank you

Berger

Re: Test.Lab Operational Modal Analysis

Siemens Genius Siemens Genius
Siemens Genius

Just rt-click in the geometry display, check that "Use Component Visualisation" is turned on, and then select "Component Visualisation" to turn on / off different geometry components.

 

6-15-16 9-23-29 AM.jpg