Performing Modal assurance criterion to get MAC number

[mohdgh]

Dear All,


I am trying to correlate the mode shapes from my FE modal to these extracted from experiment. The grid in the experiment is completely different from my mesh grid in ANSYS. I wanted to interpolate the nodal solution of my nodes to the points of the experiment. I hope this was clear. Any one able to help out?
Thanks,

Mohammad

 

[schurilov]

What kind of simulation are you trying to perform? Can you explain the experiment in more details?

 

[elogesh]

Hi,

Regarding the MAC correlation, these are the recommended steps,

1) Pre-test:
Perform FE Analysis. Extract the modes up to desired frequency range. Determine the optimum and best accelerometer location and excitor (Impact hammer/Shaker) locations, which will capture all the modes.These locations has to be communicated to Test team to perform the experimental modal analysis. It seems, you haven't performed this.

2) Correlation: First step, geometry correlation. Now you have the wire frame grid from Test. Overlap this on the FE model(This may require translation and rotation,etc). If the grids in experimental and test doesn't match. Then interpolate closest nodes in FE. Prepare simpler wireframe grid in FE. Map the full FE model mode shape results into wireframe modal results.

Now you have mode shape results on the wireframe on both FE and Test.Put these mode shape results in vector format and calculate the MAC.

It all needs good co-ordination between Test FE team.

There are commercial softwares available in the industry such LMS-Correlation and another similar product from Altair.

I use LMS-correlation for these Modal Model correlation process

Logesh