difference between G & GE dampings

Altair Forum User

Hi,

 

I would like to know, what is the difference in specifying damping as PARAM,G and GE in MAT1 card and how differently the damping works in modal frequency response analysis when we specify as G & GE. 

 

 

Thanks,

Srinivas.G

Rahul_P1

They are alternate methods to specify the damping with no effect on the results,

G specifies the uniform structural damping coefficient in the formulation of dynamics problems. To obtain the value for the parameter G, multiply the critical damping ratio, C/C0 by 2.0.
Ge is also obtained by multiplying the critical damping ratio, C/C0, by 2.0.

the GE entry is 'used to specify the overall structural damping for the elements that reference this material entry ' http://www.me.rochester.edu/courses/ME443/NASTRAN/Damping.pdf

so the difference if any, seems to me, is that here unlike G we only specify damping to the elements that reference this material,

Altair Forum User

Thanks a lot Rahul for your response. Just I would like to confirm following 2 points

 

1) If I have an assembly consists of 2 components of different materials and want to specify structural damping I should have to use GE , because the materials have different damping - Is it right ? If I use PARAM,G , it is a kind of applying same damping for both the components, which should not be the case.  

 

2) on the other-way if both the components are of same materials,then it wouldn't matter if i use PARAM,G (or) GE in MAT card - Is it right ?

 

Thanks,

Srinivas.G

Rahul_P1

That is my understanding, however it is best to try this out in a simple model and review the results, please share any such results in the forum so we can discuss further.