Shaft Analysis, Expanding instead of twisting...

[CFitzy01]

So I have taken the PTC Mechanica Tutorial as well as done a few searches for TLAP, rotation, shafts, etc and come up with similar results stating to use the total load and point to apply a moment which translates to rotation.

The problem I am having is the moment is translating to outward force but not rotation. My constraints are set to allow for rotation but no translation using either the pin constraint or the displacement constraint...both yield similar results.

Based on the preview of my load in the first picture the load should be rotating? Or am I interpreting this wrong and it is actually outward force? The load shown in the deformed analysis clearly shows the force acting in the Z direction and not rotating...any help with this would be appreciated.

 

[neomechanikos]

Sorry for the late reply. Your question is answered on the following website:

PTC Community: Tad's Simulate This!: Deformed shape of a bar in torsion

"...this is a well-known phenomenon, and is due to the linear approximation used in the default static analysis. In a linear analysis, displacement and rotations are assumed to be small. When rotations are small, the displacement of a point on a disc that rotates is approximately the rotation (measured in radians) multiplied by the distance of the point from the center of rotation. When showing the deformed shape of such a rotation in Simulate, all displacements are exaggerated by scaling."

A large deformation analysis will not have this effect.

 

[superqualicast]

Great thread.. neomechanikos I really appreciate your answer.

 

[pramit.associat]

You can typically control in small deflection matrix but if you can specify the magnitude I can better suggest u the real outcome wether you need to go for larger def matrix or default in mechanica

Regards
PRAMIT KU SENAPATI
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