a validity of the result 1

[thundersky]

Dear Everybody,
This time,my problem is about the big amplitude of the deformation in my model. I am working on tractor frame and modal analysis. I use the dimension in the model as meter.
So my young`s modulus will be Pa. But I have problem about density. At this model ,I use unit as kg/m^3 but I got a very big deformation in my reasults.
When I am considering about the validity,it is impossible when the tractor frame can have a deformation about 40 cm.
Does anybody have a comment about this?

Thank you very much

 

[meshparts]

Hi thundersky,

What elemnents are you using for your model??

What material??

You units apear to be wright... The maximal displacement must be meters, so 0.4 m?

If your material is stell, the common properties are vaguely:

MP,EX,1,210e9
MP,DENS,1,7800
MP,NUXY,0.3

But then again, you must provide more information about you model.

Regards,
Alex

 

[thundersky]

My materials property is mild steel. I used soild 45 for this model.It will be
et,1,solid45
Mp,ex,1,205e9
Mp,nuxy,1,0.3
Mp,dens,1,7850

But I just don`t understand why the amplitude is so large.

 

[meshparts]

If you are doing a modal analysis, the amplitude ist not a real amplitude!

It is just a relative number in the eigenvector to describe the eigenmode!

If you are intrested in the real desplacements, you must do a harmonic analysis whith damping.

Regards
Alex

 

[thundersky]

Dear mihaiupb,
Thank you for your comments. At this time, I do understand the results.

Best reagard,

 

[meshparts]

The mode shapes are usually normalized to the mass matrix:

Phi'*M*Phi=I,

where Phi is the matrix of the eigenvectors, M the mass matrix and Phi' the transposed matrix of the eigenvectors.

Alex