How to introduce the mass in ansys

[mohamedb]

Hi everybody;
Does any one could tell me ho to specify the mass in the modal analysis of a structure by ANsys software. I specified it through Inertia; Gravity commands but i got a very large value of frequency. I think the mass was zero.
Thanks.

 

[ASMS81]

Hello!

If you are working in millimiters you must specify the density in ton/mm^3.

If you are working in meters you must specify the density in kg/m^3.

I had also this problem in the past. Prepare a simple model of a beam and compare it with the analytical results and you will see that they match.

Note that the frequency independs on the gravity so you shouldn´t specify it.

 

[mohamedb]

Thanks ASMS81

 

[shaun8567]

"Note that the frequency independs on the gravity so you shouldn´t specify it."

This is not necessarily true; the loading condition could be such that the initial stress state caused by gravity affects the stiffness of the structure. If this is the case, then a pre-stressed modal analysis is needed.