Need an help in Modal Analysis

[bhartish]

Need an urgent help in Modal Analysis

I am doing an modal analysis of audio system attached to an Instrumental panel in a car using ANSYS 13 version software. I have used SHELL281 element for meshing and Black Lanczos method to extract the modes. This shell element has six degrees of freedom. I Have extracted 12 modes but the first six frequencies I am getting zero value. I am not able to interpret the results. request anyone to guide .

 

[AlephZero]

The first 6 frequencies will be zero if your structure is a free body. They conrrespond to the 6 rigid body motions of the structure (3 translations and 3 rotations).

It would probably be better to assume the panel is fixed rigidly at the points where it is connnected to the rest of the car.

 

[joslopher]

Hi,
Why did you perform a free-free modal analysis? Why it is useful for? I mean, you should always have into account the constraints, shouldn't you?