Learning Forum

[David Gonzalez-Nino]

Greetings;

I am interested on performing a modal analysis, but I am an issue with the number of mode to be extracted. The geometry is a power module encapsulated with a gel material. I am interested in to understand how it behaves under vibration. It looks like I need to extract a huge number of modes to obtain a significant ratio of effective to total mass, due to the gel material. Currently, I am extracting 600 modes and the ratio of effective to total mass is less than 0.1. How can I perform a modal analysis when I have material that differ greatly in mass and stiffness (gel and metal)? Is there is a way to reduce the number of modes needed to be extracted or reduce the number of modes "detected" by ANSYS and just extract the significant ones?

Thanks,

 

[Rahul Kumbhar]

Hi David,

If you know the range of actual condition operating frequency, then you can set the frequency range under Modal analysis setting. If you are planning to perform MSUP analysis in this frequency range, then for modal analysis you can select 1.5 - 2 times larger frequency range.

[David Gonzalez-Nino]

Hi Rahul;

I am restricting the frequency range, the problem is that it is extracting a new mode every 0.1Hz and all are related to the gel. 

 

Best wishes,

[peteroznewman]

Hi David,

Try changing the power module to be a rigid body. In that way, it will only contribute mass and not stiffness and the modes extracted will be the vibration of that rigid mass in the gel.