## Applying a torque using FORCE and TRANSFORM constraints

About the development of the FEM module/workbench.

Moderator: bernd

KgoaOT
Posts: 66
Joined: Mon Jul 18, 2016 9:08 am

### Applying a torque using FORCE and TRANSFORM constraints

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

TorqueExample.fcstd
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 (44.07 KiB) Viewed 1584 times
Depicted below is pipe showing the displacement:
WithDisplacement.PNG (48.9 KiB) Viewed 1584 times
The new branch can be found here:
bernd
Posts: 11084
Joined: Sun Sep 08, 2013 8:07 pm
Location: Zürich, Switzerland

### Re: Applying a torque using FORCE and TRANSFORM constraints

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

https://github.com/berndhahnebach/FreeC ... meshregion
bernd
Posts: 11084
Joined: Sun Sep 08, 2013 8:07 pm
Location: Zürich, Switzerland

### Re: Applying a torque using FORCE and TRANSFORM constraints

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

screen.png (126.06 KiB) Viewed 485 times
bernd
Posts: 11084
Joined: Sun Sep 08, 2013 8:07 pm
Location: Zürich, Switzerland

### Re: Applying a torque using FORCE and TRANSFORM constraints

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 (133.2 KiB) Viewed 478 times
bernd
Posts: 11084
Joined: Sun Sep 08, 2013 8:07 pm
Location: Zürich, Switzerland

### Re: Applying a torque using FORCE and TRANSFORM constraints

My mechanical knowledge about twisted steel structures is limited. Is someone able to do the math for the example of the first post?
bernd
Posts: 11084
Joined: Sun Sep 08, 2013 8:07 pm
Location: Zürich, Switzerland

### Re: Applying a torque using FORCE and TRANSFORM constraints

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