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what is AutoMAC and Cross MAC in LMS Test.Lab Modal Analysis

Creator
Creator

please any one explain what is AutoMAC and  Cross MAC in LMS Test.Lab Modal Analysis ?

8 REPLIES

Re: what is AutoMAC and Cross MAC in LMS Test.Lab Modal Analysis

Siemens Phenom Siemens Phenom
Siemens Phenom

Hello,

 

On the Modal Validation worksheet, you can press the AutoMAC button.  This will calculate the Modal Assurance Criteria for the Mode set in the active processing set to itself.  This will show how each mode in the mode set is correlated to the other modes.  The diagonal will be 1 since Mode 1 looks like Mode 1, etc.  If the off diagonals are high, then perhaps you selected too many poles and one can be deleted or perhaps you have spatial aliasing.  i.e. you need more response locations on the stucture to make each mode shape unique.

 

Per Cross MAC, I assume you mean the MAC button on the bottom of the Modal Validation worksheet.  This will do a MAC between the Mode set in the active processing set (mode set A) and the Mode Set defined at the bottom of the Modal Validation worksheet identified via the Section and Processing Set pull down or in the Input Basket (this is Mode set B).  This allows you to compare different analyses, or different designs,  or different boundary conditions, etc.

Re: what is AutoMAC and Cross MAC in LMS Test.Lab Modal Analysis

Creator
Creator

Thanks.

Re: what is AutoMAC and Cross MAC in LMS Test.Lab Modal Analysis

Experimenter
Experimenter

How do i do MAC between  modes obtained in LMS and Modes obtained in Ansys/Hypermesh??

Re: what is AutoMAC and Cross MAC in LMS Test.Lab Modal Analysis

Siemens Phenom Siemens Phenom
Siemens Phenom

Hello,

 

In order to do a MAC between two mode sets they need to have the same degrees of freedom.  i.e.  the Point ID's or Nodes need to match.  This is true between Test.Lab modes and Test.Lab modes and modes imported from Universal file, Nastran or ANSYS.   If the ANSYS and Test.Lab nodes are the same then add the ANSYS file (Test.Lab rev 17.2 or later) to the Input Basket and on Modal Validation select the Input Basket for mode set B and do the MAC.   If the ANSYS nodes and the Test.Lab nodes do not have the same name then you can use a Universal File and it's associated Node map file to map them.  To accomplish that:

 

1)  Export the ANSYS file to Universal file and turn on the option to create the node map file during export.  You might need to do this in two steps.  a)  Convert the Ansys file to a Test.Lab project and then b)  Export that Test.Lab project to Unviersal file and turn on the option to generate the node map file.

2)  Edit the node map file to map the ANSYS nodes to the Test.Lab nodes.

 

# LMS Test.Lab project-17A
#
# Test.Lab Point ID versus UF node number mapping table
#
# Universal file Test.Lab point ID
# node tag "comp:node"
# -------------- ---------------
1                    frame:1
2                    frame:2

etc.

 

 

3)  If you refresh Test.Lab and view the universal file modes now, the node names should now match the Test.Lab nodes.

4)  Add the Universal file to the Input Basket and use on Modal Validation as Mode set B to get the MAC between the Test.Lab modes and these modes.

 

Here are the Unvirsal File export options (Step 1 above):

4-17-2018 10-32-38 AM.jpg

 

 

For more information on using ANSYS files in LMS Test.Lab 17.2 and later view this article:  https://community.plm.automation.siemens.com/t5/Testing-Knowledge-Base/Import-ANSYS-Geometry-and-Mod...

 

Re: what is AutoMAC and Cross MAC in LMS Test.Lab Modal Analysis

Siemens Phenom Siemens Phenom
Siemens Phenom

Hello,

 

I should have mentioned that if the node names are different and if the geometries are in a different space (origin, orientation and scale) then correlation software could be use do correlate the TEST and CAE model.  Within our tools, Virtual.Lab Correlation, NX Correlation and Simcenter 3D Correlation could be used to accomplish this.

 

Kevin

Re: what is AutoMAC and Cross MAC in LMS Test.Lab Modal Analysis

Experimenter
Experimenter

Thank you for your help!!

 

Re: what is AutoMAC and Cross MAC in LMS Test.Lab Modal Analysis

Experimenter
Experimenter

I am still not able to do it. Do you have a demo video or something for the file conversion and nodemapping. I am quite new to LMS. I have explored few tools. Not many. Therefore, i wanted to try do MAC so that i can show the uniqueness of my shapes.

 

Re: what is AutoMAC and Cross MAC in LMS Test.Lab Modal Analysis

Siemens Phenom Siemens Phenom
Siemens Phenom

Hello,  I'm sorry but to make a video would be quite a bit or work and I am not sure that it would help more than the information above.  Let me clarify a little:

 

1)  If the ANSYS and TEST models have different locations in space, different scale and different node numbers and names then a correlation software package which handles such differences should be used.  Within Siemens we have LMS Virtual.Lab Correlation, Simcenter 3D Correlation and NX Correlation that can handle this.

 

2)  If the ANSYS and TEST models have the same location in space (i.e. the same orientation and scale) and just the node numbers \ point ID's are different then you export the ANSYS model to universal file and create a node map file along with the export.  That is an ASCII file that can map the ANSYS CAE node to the Test.Lab node. When importing the Universal file modes they will now use the TEST node names (from the node map file) and can be used in Test.Lab modal validation.  This is most useful when the number of nodes in TEST and CAE are the same.  If they are not the same, only same node numbers will be correlated.  With a lot of CAE nodes the Universal node map file becomes very large and harder to manage.

 

I really believe you should reach out to your local Global Technical Assistance Center (GTAC) team as they can do a screen share with your or you can provide both files and they can discuss your options.