Changing Self weight magnitude
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- Posts: 3
- Joined: Sat Jun 06, 2020 5:05 pm
Changing Self weight magnitude
Hi, I'm new, I hope I'm in the correct section..
I'm new to Freecad and I was trying to understand the FEM workbench futures.
I'm studying some static equivalent load applied to quite-complex shapes.
So I tried to use the Self-weight load changing the magnitude of the gravity but it doesn't work, I get the same result with like 1g or 10g.
So I tried it with a "beam" 1x0.01x0.01m and I got the same result.
I checked .inp file and also I tried to change the numbers directly from it but nothing changed.
OS: macOS 10.15
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.16146 (Git)
Build type: Release
Branch: (HEAD detached at 0.18.4)
Hash: 980bf9060e28555fecd9e3462f68ca74007b70f8
Python version: 3.6.7
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: Italian/Italy (it_IT)
I'm new to Freecad and I was trying to understand the FEM workbench futures.
I'm studying some static equivalent load applied to quite-complex shapes.
So I tried to use the Self-weight load changing the magnitude of the gravity but it doesn't work, I get the same result with like 1g or 10g.
So I tried it with a "beam" 1x0.01x0.01m and I got the same result.
I checked .inp file and also I tried to change the numbers directly from it but nothing changed.
OS: macOS 10.15
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.16146 (Git)
Build type: Release
Branch: (HEAD detached at 0.18.4)
Hash: 980bf9060e28555fecd9e3462f68ca74007b70f8
Python version: 3.6.7
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: Italian/Italy (it_IT)
Re: Changing Self weight magnitude
Hello,
it might be a bit confusing because FreeCAD gui enables only to set direction vector (default is 0,0,-1), but it does not influence acceleration magnitude. By now, magnitude must be changed manually in *.inp file, e.g. for the Earth acceleration, there is by default 9810 mm/s^2,
but if you would like to calculate with a Moon gravity acceleration 1625 mm/s^2 it would be
it might be a bit confusing because FreeCAD gui enables only to set direction vector (default is 0,0,-1), but it does not influence acceleration magnitude. By now, magnitude must be changed manually in *.inp file, e.g. for the Earth acceleration, there is by default 9810 mm/s^2,
Code: Select all
*DLOAD
Eall,GRAV,9810,0.0,0.0,-1.0
Code: Select all
*DLOAD
Eall,GRAV,1625,0.0,0.0,-1.0
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- Posts: 3
- Joined: Sat Jun 06, 2020 5:05 pm
Re: Changing Self weight magnitude
Thanks a lot, you made my day
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- Posts: 3
- Joined: Sat Jun 06, 2020 5:05 pm
Re: Changing Self weight magnitude
What if I want to combine 2 different accelerations for example 1000 on y and 5000 on z?
Do I need to compute like to put sqrt(1000^2 * 5000^2), that is 5099, as magnitude and then use:
where 0.02 and 0.98 comes from the projection?
Can I combine two different loads like this:
Do I need to compute like to put sqrt(1000^2 * 5000^2), that is 5099, as magnitude and then use:
Code: Select all
*DLOAD
Eall,GRAV,5099,0.0,0.02,0.98
Can I combine two different loads like this:
Code: Select all
*DLOAD
Eall,GRAV,1000,0.0,1.0,0.0
*DLOAD
Eall,GRAV,5000,0.0,0.0,1.0
Re: Changing Self weight magnitude
use version 0.19 there it might be possible. If not change value in file https://github.com/FreeCAD/FreeCAD/blob ... nstants.py in your FreeCAD mod directory.
For FEM you should use 0.19 FreeCAD version.
For FEM you should use 0.19 FreeCAD version.
Re: Changing Self weight magnitude
It seems that superposition works. You can prescribe more accelerations, they will be combined. Direction vector is normalized by CalculiX, so you should obtain same results for these inputs
where total magnitude is (5000**2+1000**2)**0.5 = 5099.0195
Code: Select all
*DLOAD
Eall,GRAV,1000,0.0,1.0,0.0
*DLOAD
Eall,GRAV,5000,0.0,0.0,1.0
Code: Select all
*DLOAD
Eall,GRAV,5099.0195,0.0,1.0,5.0
Code: Select all
*DLOAD
Eall,GRAV,5099.0195,0.0,10.0,50.0
Re: Changing Self weight magnitude
Try to input 2.0 in self weight object. It may use 2x9.810 but I am not sure. I am not on a computer on the weekend.
Re: Changing Self weight magnitude
Input fields in FreeCAD have effect on direction vector
Code: Select all
*DLOAD
Eall,GRAV,9820,0.0,0.0,-1.0
Code: Select all
*DLOAD
Eall,GRAV,9820,0.0,0.0,-2.0