Opinion ON FEM Result

About the development of the FEM module/workbench.

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Laurie Hartley
Posts: 71
Joined: Mon Feb 27, 2017 5:33 am

Opinion ON FEM Result

Postby Laurie Hartley » Sat Nov 30, 2019 6:09 am

I have just attempted my first FEM attempt. here is link to the file.

https://mega.nz/#!3xgyXIqR!P1ZvoK81bVKX ... Ge8B094_qc

The parameters for my experiment are as follows:

The plate is 16 mm thick and I used calculix steel as the material

A force of 10 kN will be exerted by a bolt in opposite directions, away from the centre of the plate in the first set of two bolt holes
A force of 5 kN will be exerted by a bolt in opposite directions, away from the centre of the plate in the remaining two bolt holes
A force of 5 kn will be exerted by another set of 4 snug fitting plates, away from the centre of the plate, in four directions on the face at the end of each of the slots.

I used a maximum mesh size of 5 and minimum of 3.

I am trying to establish whether or not the plate will be pulled apart under these loads. I am not an engineer but my guess is the week point is the two corners at the end of each slot.

On first a appearances it looks like I have a good result but I would appreciate an opinion from any of you nice :D engineers on this board.

OS: Windows 8.1
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.16131 (Git)
Build type: Release
Branch: releases/FreeCAD-0-18
Hash: 3129ae4296e40ed20e7b3d460b86e6969acbe1c3
Python version: 3.6.6
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedStates (en_US)
thschrader
Posts: 1457
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

Re: Opinion ON FEM Result

Postby thschrader » Sun Dec 01, 2019 11:26 am

Hi,
I did some modifications on your model:
-deleted all fillets
-adding mesh refinement
When starting a FEM-analysis, try to "unrefine" your model as much as possible to avoid mesh errors.
The critical zone are the corners in the slot....
Plate_C1_FEM_TS.FCStd
(39.74 KiB) Downloaded 30 times
stresses.JPG
stresses.JPG (71.97 KiB) Viewed 565 times
User avatar
Kunda1
Posts: 6223
Joined: Thu Jan 05, 2017 9:03 pm

Re: Opinion ON FEM Result

Postby Kunda1 » Sun Dec 01, 2019 12:18 pm

Moved to FEM subforum
OP, please consider using v0.19 if you plan on working with FEM workbench per the recommendations of devs of this workbench. Thank you.
Want to contribute back to FC? Checkout:
#lowhangingfruit | Use the Source, Luke. | How to Help FreeCAD | How to report FC bugs and features
Laurie Hartley
Posts: 71
Joined: Mon Feb 27, 2017 5:33 am

Re: Opinion ON FEM Result

Postby Laurie Hartley » Mon Dec 02, 2019 10:18 am

Thank you very much thschrader. I can’t get to my PC until tomorrow. I will have a look at the amended file and post again.

Kinda I thank you for your advice. I will upgrade to V19.

Thank to all involved in the development of FreeCAD and the forum members who offer advice and help. I truly appreciate it.
Laurie Hartley
Posts: 71
Joined: Mon Feb 27, 2017 5:33 am

Re: Opinion ON FEM Result

Postby Laurie Hartley » Fri Dec 06, 2019 4:45 am

tschrader, thank you once more for your help. If you would be so kind could you answer one more question for me please.

I notice you have placed a fixed constraint on each of the four bolt holes. The outward forces on the plate (axial loads?) will be exerted by the bolts in the bolt holes. I have inserted a couple of jpegs of the completed assembly which will explain. The maximum loads will be exerted in the middle of the bottom series of chords of the spaceframe.

So my question is should I remove the fixed constraints that you inserted at the bolt holes?
Attachments
Bottom Chord Connection.JPG
Bottom Chord Connection.JPG (21.37 KiB) Viewed 405 times
Side View of Spaceframe.JPG
Side View of Spaceframe.JPG (30.15 KiB) Viewed 405 times
Laurie Hartley
Posts: 71
Joined: Mon Feb 27, 2017 5:33 am

Re: Opinion ON FEM Result

Postby Laurie Hartley » Fri Dec 06, 2019 5:28 am

tschrader - I should have mentioned that this warning popped up when I opened your modified file.

It doesn't mean anything to me but it may be significant for the developers>

Generic Warning: In ..\Common\Core\vtkInstantiator.cxx, line 265
vtkInstantiator::CreateInstance was deprecated for VTK 8.1 and will be removed in a future version.
Last edited by Laurie Hartley on Fri Dec 06, 2019 5:31 am, edited 1 time in total.
thschrader
Posts: 1457
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

Re: Opinion ON FEM Result

Postby thschrader » Fri Dec 06, 2019 12:31 pm

Laurie Hartley wrote:
Fri Dec 06, 2019 4:45 am
So my question is should I remove the fixed constraints that you inserted at the bolt holes?
Depends on what you want to calculate.
In general: for a static calculation in 3D-space the body (frame, plate, bridge, spaceframe...)
must be fixed in a way, that a movement/rotation along/among global x/y/z-axis is impossible.
Can you post the complete spaceframeß
vtk-error-warning: dont worry, I used an "old" FC.017 version
Laurie Hartley
Posts: 71
Joined: Mon Feb 27, 2017 5:33 am

Re: Opinion ON FEM Result

Postby Laurie Hartley » Sat Dec 07, 2019 8:45 am

Thanks thschrader - here is a link to the spaceframe.

https://mega.nz/#!bgwjXKjb!ClxJZsKGZnyX ... zb925yVnLI

The spaceframe is designed to sit on two rows of four screw jacks when in use as a support system for scaffolding or formwork.
The idea of the skates and channel tracks is so that the frame can be relocated.

My original intention was to do a complete analysis of the frame in the FEM workbench (I have inserted loads and support constraints) but FreeCAD says that it cannot perform multiple meshes at this stage.
thschrader
Posts: 1457
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

Re: Opinion ON FEM Result

Postby thschrader » Sat Dec 07, 2019 11:28 am

Laurie Hartley wrote:
Sat Dec 07, 2019 8:45 am
here is a link to the spaceframe.
https://mega.nz/#!bgwjXKjb!ClxJZsKGZnyX ... zb925yVnLI
wrong file... :o
wrong_file.JPG
wrong_file.JPG (13.49 KiB) Viewed 312 times
please post the file with FCStd extension (not the backup FCStd1)
Laurie Hartley
Posts: 71
Joined: Mon Feb 27, 2017 5:33 am

Re: Opinion ON FEM Result

Postby Laurie Hartley » Sat Dec 07, 2019 9:34 pm

tschrader - apologies. This is the file I should have linked.

https://mega.nz/#!OsYA1KTA!1EFc8XP9b_Jk ... uAGPk44mDg