Frame Generator - Custom Section: swept surface?!

[jamiebryson]

Hi,

I'll try to explain what I'm attempting to do as plainly as I can (sorry for any waffle)! :

I have built a frame using frame generator (see screenshot1 attached). I do this often, then export the frame as a .iges and .step file so that the frame can be evaulated using third-party FEA software which uses surfaces.

To make life easier for the FEA chaps, I replace the content centre standard SHS Section with a solid square to remove the sections' inside faces and corner rads.

We also produce a lot of frames using I-sections. The FEA guys would like me to also replace the ISO I-Section used with a custom I section.

However, what they require is a simple I section beam that consists of three surfaces; one web and two flanges. I am trying to produce a method of doing this in frame generator.. somehow sketching 3 lines and trying to 'extrude' or 'sweep' these lines into a frame made of surfaces... (see screenshot 2 attached).

Is this possible at all? I realise extrusions can only happen with a closed-loop sketch profile.. and so I'm not sure how to go around getting what I need.

Any ideas would be appreciated GREATLY!

Thanks

Jamie

[safiredesignengineers]

Hi Jamie

do you mean like this

Adrian

[jamiebryson]

Yes!

That's exactly what I'm after! ..

.. I can extrude one line of the sketch into a surface, but then the sketch is consumed by that surface, and I can't seem to add the other two lines to the profile..

.. the next step is somehow encoporating that into frame generator?!

Thanks

Jamie

[safiredesignengineers]

Hi Jamie

once you have extruded the first one, right click on the sketch in the tree and select share sketch then you can extrude the other two as two separate extrusions.

Then in frame generator select the edges of the surfaces and apply the frame members.

See enclosed.

be carfull with the frame generator as it has know issues, see:

http://forums.autodesk.com/t5/Autodesk-Inventor/Should-auto-desk-be-held-accountable-for-errors-caus...

regards Adrian

[jamiebryson]

Hi,

Thanks! That's a great help regarding getting those 3 surfaces in order..

You've misunderstood a bit regarding the frame generator part of my question.. what I want is those 3 surfaces (effectively making an I-beam) to be my member in the frame generation.. i.e. my screenshot 2 is the member section that the beam is created from..

does that make sense?

so effectively my frame created by FG is a load of members consisting of 3 surfaces each..

Thanks

Jamie

[safiredesignengineers]

you need to create the end profile and extrude it as a new part, then save it out as a structural member, entering all the settings you need.

however most members are already in the content centre?

regards Adrian

[jamiebryson]

Yes, all the structural members we use are in the content centre.. (SHS, RHS, HEB, IPB etc)

However for FEA purposes, they want a frame using the simplified '3 surfaces' I-beams rather than a normal I-Beam profile with corner rads and plate thicknesses..

I will have a go at producing the 3-line end profile, extruding a 3-surface ipart and authoring a structural shape.

Thanks for all the help!

Jamie

[safiredesignengineers]

I think you can only produce frame members from solids as opposed to surfaces, but from what I can see this is OK for you as if you need plate thicknesses, then you just need to draw the H section in 2d allowing for the plate thickness then extrude and author.

see enclosed.

regards Adrian

[PaulMunford]

You can only extrude an open geometry into a surface, so to get this in one hit you would have to draw a continuos line that doubles back over itself. 

I have no idea weather you can add frame generator parts that consistof surfaces only - let us know how you get on with that!

[blair]

If you are using a Pro version of Inventor, have you looked at the "Frame Analysis" module? We use both Inventor and Simulation (formery Algor), but if I am working with a model that was done in Frame-Gen, this gives me a simplified model that runs much faster. Much like the old 3D line model in Algor.

[stevec781]

You could use shrinkwrap to create a part without internal faces and then derive surfaces/faces into a new part.

But I wonder why your fea guys want surfaces for beam models.  The math behind beam elements and shell elements is different and modelling a beam type structure using surface/shell elements can give incorrect results if the mesh is too course.  (They should have a minimum of 3 shell elements across the web).  It sounds to me that they are doing it the hard and time consuming way, and possibly incorrectly as well.  But even if they want to use shell elements, the model might still be incorrect as the outer surfaces from your Inventor model will be in the wrong position for where the nodes should be.  You should be giving them the mid planes.  The significance of this will depend on thicknesses and aspect ratios.

[jamiebryson · Accepted solution]

Hi,

I have come up with a solution (which doesn't completely resolve what I want but it'll do unless anyone knows of any other method) but I thought I'd post it on here for those who want a round-up on this issue..

The steps I have taken are:

1. I created my frame structure using Frame Generator, consisting of standard ISO I-Beam Sections, applying all necessary end treatments

2. I then highlighted all the beams and changed from the ISO section to my own custom section (which I published using iparts etc).. my custom section can be seen in the attachment 'I-Beam example'. - This off-set geometry allowed me to pick 3 surfaces from it (shown in red) which gives me the centre-planes of the web&flanges..

3. (The time-consuming part).. I then dervied (as a set of *orange* surfaces) each individual beam , saved as a new part, and deleted all the surfaces apart from the three mid-plane ones I wanted to keep.. so now i.e. representing my I-beam as 3 mid-section planes.

4. Then, in my frame assembly, right clicking and going component>replace, I replaced each beam with its derived surface identical.

This has resulted in me from having a frame produced in frame generator, to the same frame assembly, but the beams represented by 3 mid-plane surfaces, which represent the I-Beam, with all end treatments still intact.. (see attached 'screenshot1'. The reason I said it hasn't fully resolved the issue is that there is that the FEA guy has to extend the web surface to touch the two flange surfaces due to the section used (which cant be helped).  However, its a process that will save my FEA team a lot of time with post-processing my frame generator model to use in third-party FEA software!

Hope this is useful to someone else!

Thanks

Jamie