topic Re: Frame Analysis in Inventor Forum

Frame Analysis

pmw-eng — Tue, 17 Mar 2015 13:23:26 GMT

I have a 2400mm long RHS beam measuring 60x40x3. On fixing the ends and applying a load of 100N at the centre, I get the correct reaction forces which basically is 50N at each end but the Force diagram I get is slightly different than expected. What the diagram implies is that the force is not applied at the centre.

From mechanics, when a force is applied at the centre of a beam, a straight line at the centre of the beam rather than the inclined one shown in the diagram is expected. What could be the reason for this?

Re: Frame Analysis

admaiora — Tue, 17 Mar 2015 13:56:21 GMT

Hi Pmw,

Something like this?

it depends on which constraints do you use.

Fixed constraints will remove all translations and all rotations in the nodes, so in this case it will be present moment in the nodes.

Look a this video where custom constraints are used.

Re: Frame Analysis

pmw-eng — Tue, 17 Mar 2015 14:36:30 GMT

Thanks for the help but still short of what I'm looking for. At the point of load application, there should be an abrupt change of force also where the bending moment will be maximum. The force diagram should look as the attached but what I'm getting is different. Look at the point of load application and compare the two.

Re: Frame Analysis

admaiora — Tue, 17 Mar 2015 16:57:27 GMT

Hi Pmw,

that gradient is just visual to point out graphically the drop of the force.

However i would listen another interpretation by Ravi Burla.

Re: Frame Analysis

pmw-eng — Tue, 17 Mar 2015 17:05:54 GMT

Thanks for the help, and still on the same topic of beams, is there a way to an analysis of curved beams? I've tried it before but the nodes don't get created

Re: Frame Analysis

blair — Tue, 17 Mar 2015 17:49:37 GMT

Not in Frame Analysis, you would have to use the conventional FEA and mesh the model.

Re: Frame Analysis

raviburla — Tue, 17 Mar 2015 18:29:34 GMT

Hi,

Thanks for mentioning me in the post.

I think the force diagram (shear diagram) is accurate is being shown in Frame Analysis. Please see the attached image - it shows the free body diagrams to compute the shear forces ( ignored the moment diagram). Please let us know if this answers your question.

Thanks,

Ravi Burla

Re: Frame Analysis

admaiora — Tue, 17 Mar 2015 18:36:37 GMT

Thank you Ravi for your contribution.

Pmw is was referring too to the shear force diagram edges, they should be vertical has you have drawn and he was wondering why they are like this:

Re: Frame Analysis

raviburla — Tue, 17 Mar 2015 18:40:16 GMT

Hi,

Thanks for the explanation! I think the reason for the slanted line is purely graphical, we choose discrete points on the beam axis to plot the diagrams, so this leads to the slant. I will update if I find more information.

Thanks,
Ravi Burla

Re: Frame Analysis

admaiora — Tue, 17 Mar 2015 18:42:13 GMT

Thank you Ravi for the support!

Re: Frame Analysis

pmw-eng — Wed, 18 Mar 2015 09:38:41 GMT

Thank you all for the support, I do appreciate. Though I'd suggest Autodesk to work on that as sometimes one just wants to copy the generated SF and BM diagrams to a report as opposed to plotting them using other applications or drawing them manually.

Thanks

Re: Frame Analysis

raviburla — Wed, 18 Mar 2015 15:52:19 GMT

Hi,

There are options to set the number of segments in the beam diagrams. Please see the image below:

The image looks like this after the setup, you may have to recompute the solution.

If this feature is important for your workflows, can you please log it in Inventor Idea Station?

Thanks,

Ravi Burla

Re: Frame Analysis

admaiora — Wed, 18 Mar 2015 15:58:58 GMT

Great call Ravi!

I didn't know that !

Thank you!

Re: Frame Analysis

pmw-eng — Wed, 18 Mar 2015 16:26:53 GMT

Wow, problem solved. Didn't know that...Thanks!!