Applying a torque using FORCE and TRANSFORM constraints

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KgoaOT
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Applying a torque using FORCE and TRANSFORM constraints

Postby KgoaOT » Fri Dec 09, 2016 8:08 am

The transform constraint has been extended to allow for applied forces to be transformed into in a new coordinate system.

- start FreeCAD --> StartWB --> load "TorqueExample" file
TorqueExample.fcstd
(738.21 KiB) Downloaded 155 times
Essentially in this a example, a force is applied to the external surface of a pipe and then the coordinate system of the external surface is transformed into a cylindrical coordinate system. The direction of the applied force is in the global Y direction (this corresponds to the Tangential direction after the coordinate transformation).

Depicted below is pipe showing no displacement:
WithoutDisplacement.PNG
WithoutDisplacement.PNG (44.07 KiB) Viewed 1584 times
Depicted below is pipe showing the displacement:
WithDisplacement.PNG
WithDisplacement.PNG (48.9 KiB) Viewed 1584 times
The new branch can be found here:
https://github.com/makkemal/FreeCAD/tre ... traint/src
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bernd
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Re: Applying a torque using FORCE and TRANSFORM constraints

Postby bernd » Sat Dec 10, 2016 8:03 pm

works great ! Added to my development branch for next FEM pull request.

https://github.com/berndhahnebach/FreeC ... meshregion
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bernd
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Re: Applying a torque using FORCE and TRANSFORM constraints

Postby bernd » Wed Jul 22, 2020 10:39 am

I wanted to calculate the results myself. For this I used a simpler example.

full cylinder
lenght = 1000 m
diameter = 60 mm
G = 81000 MPa --> E = 210600 MPa
Twist (delta) = 0.4 degree

twisting moment (torsional moment):
Mt = (delta_in_rad x Pi X r^4 x G) / (2 x l) = (delta x Pi^2 X r^4 x G) / (180 x 2 x l)
Mt = (0.4 x 3.14^2 x 30^4 x 81000) / (180 x 2 x 1000)
Mt = 71.80e4 Nmm

max twisted stress:
max tau = 2 x Mt / (Pi x r^3)
max tau = (2 x 78.80e4) / (3,14 x 30^3)
max tau = 17.0 N/mm2

Force = 71.8 N/mm / 30 mm = 29933.33 N on top edge.

max deformation x = max deformation y = max deformation = 30 mm sin 0.4 degree = 0.209 mm

attached is the file ...


torque_simple_1.FCStd
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screen.png
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bernd
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Re: Applying a torque using FORCE and TRANSFORM constraints

Postby bernd » Wed Jul 22, 2020 10:51 am

max Tresca stress is red in the bar and constant around 18.08 N/mm2 similar to max tau = 17.0 N/mm2 from the math

screen1.png
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bernd
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Re: Applying a torque using FORCE and TRANSFORM constraints

Postby bernd » Wed Jul 22, 2020 10:53 am

My mechanical knowledge about twisted steel structures is limited. :oops: Is someone able to do the math for the example of the first post?
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bernd
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Re: Applying a torque using FORCE and TRANSFORM constraints

Postby bernd » Wed Jul 22, 2020 3:51 pm

bernd wrote:
Wed Jul 22, 2020 10:53 am
My mechanical knowledge about twisted steel structures is limited. :oops: Is someone able to do the math for the example of the first post?
thschrader wrote: :bell: