fea - torsion rigidity calculation

[PabloPicasso]

Hi.
use autodesk inventor for designing assimi parts in 3d and I have been trying for some time to use the integrated fea module.

I should calculate the torsion rigidity of a tube frame in ft*lbs/deg

Suppose the frame is a simple square, the method I used in the fea analysis was to "block" two corners of one side and apply a force (say 100 n) on the other two, but in reverse way to create a torque moment.

the results I obtain however are only in mm of deformation and mpa (von mises stress)

Can you help me?

 

[cacciatorino]

Hi.
use autodesk inventor for designing assimi parts in 3d and I have been trying for some time to use the integrated fea module.

I should calculate the torsion rigidity of a tube frame in ft*lbs/deg

Suppose the frame is a simple square, the method I used in the fea analysis was to "block" two corners of one side and apply a force (say 100 n) on the other two, but in reverse way to create a torque moment.

the results I obtain however are only in mm of deformation and mpa (von mises stress)

Can you help me?

I'd say that knowing the shift and length of your edges, it's not very difficult to get back at a torque moment and a twist angle. . . .

If you put a drawing on your load pattern, maybe it's easier to answer. But in order to exist a twist, it would be necessary that the geometric entity to which the stress is applied is a solid and not a flat figure. from what I understand, yours is a case of bending and not twisting.

 

[PabloPicasso]

In fact I think I can get it by doing:

force * distance from the central axis of the frame/rotation angle

Now however the problem is to understand how to calculate the angle of rotation. on my fea module I can't trace a measure between the original and the modified position. I think it's better to open a discussion in the inventor section.... :biggrin: