Torsion angle of square bar
Torsion angle of square bar
(OP)
I want to verify the torsion angle on a square bar with FEA software (NX 6). The bar has dimensions of 50mmx50mmx100mm. The bar is fixed on one end and on the other a moment of 200Nm is exerted. Is it possible to calculate the torsion angle with the nodal displacements using an approximating formula? And if so, which formula?





RE: Torsion angle of square bar
twist due to torque is in just about any structures text book ... theta (radians) = TL/(G*(a^4/6)) ...
i have to admit the "/6" is my interpretation of the polar moment of inertia, my reference has 0.141 (not quite 0.1667)
RE: Torsion angle of square bar
RE: Torsion angle of square bar
Try using a much more slender bar, if you are just trying to validate your method.
The torsional elastic constant for non circular shapes is a rather exciting topic, in general.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Torsion angle of square bar
you could take the four corner nodes and see how they've deflected relative to the center node (or relative to their average deflection).
RE: Torsion angle of square bar
RE: Torsion angle of square bar
could you calculate the angle between a line on the undeformed beam and the deformed section ?
RE: Torsion angle of square bar
25 0,0023904 1,882E-08 2,99E-06
12,5 0,0026496 1,298 3,31E-06
5 0,0027616 7,636 3,45E-06
Theoretical values:
thèta = 0,0028
tau max = 7,7 MPa
By the way, the torsion angle values are thèta = s/(0.5a/0.5L)
muliplied by 2. Could you explain why this formula could be correct?
RE: Torsion angle of square bar
RE: Torsion angle of square bar