Learning Forum

[jonsys]

Based on previous discussions (e.g. this), I implement a displacement on the edge of the beam

and then I shorten the beam length(less elements) to apply a remote displacement:

with details like:

 

From this I should expect same results right? But they are not the same (displacement as well):

Did I do something wrong?

attached is also the file.

Regards,

[peteroznewman]

It's very commendable that you built models to test your understanding of how things work Jon, excellent!

In the case above, if you want the same stress near the root of a cantilever beam for a full model and one using a remote point, you must apply a force to the tip and not a displacement. If you do that, then the stress at the root will be the same.

Regards,
Peter

[jonsys]

thank you Peter,

yes you are right, it works when remote force is applied.

is there a reason why remote displacement does not give same results?

I mean, if the results are not same, then the usage of remote displacement is limited. But to what case/purpose, if not to the above mentioned one?

Regards,

[pibeking]

Bump on this question from jonsys. Why does remote force only (and not remote displacement) cause both solutions to be the same?

 

[munkhunur]

Did you find the reason of the difference on the results between remote displacement and displacement? If so, please share with us. Thanks 

[peteroznewman]

Consider a cantilever beam with a tip load of F that results in a tip displacement d. Now chop off 80% of the beam and replace it with Rigid Elements. If you apply the same tip force to the rigid elements, the beam elements at the base see the exact same shear force and bending moment so the stress will be the same, but the displacement at the tip of the rigid elements will be much less, because 80% of the flexibility was removed.

  

If you apply the same displacement d to the tip of the rigid elements, you will get much higher stress in the beam elements at the base.

[HarsihilZLHZ]

Hello Peters,nI have seen your Ansys file of remote force.nis it possible to get stress/deformation at the remote force location?nThanks.nn

[peteroznewman]

If you want stress at the remote force location then you need material at that location. If you cut away that material, there is nothing there to compute stress from.n