Learning Forum

[MHND]

Hello, 
I have performed a pure bending test on a beam element (angle of rotation 60° at both ends), so I have two results: 
First: reaction moment (Probe - Moment Reaction) This moment would be calculated in the direction of the global coordinate system ([1, 0, 0], [0, 1, 0], [0, 0, 1]) but you can choose at which position to calculate the moment (default setting the centroid of the geometry).
Second: (Beam Results - Bending Moment) here Ansys take the solution coordinate system to calculate the moment, which means the element coordinate system that you can get it from Solution - Elemntal Triads BUT the end will rotate during the bending test, which means the Beam Element at the end will rotate 60°.
My question is, how would the beam results be calculated in this case, in relation to which coordinate system? in relation to the first position of the element coordinate or in relation to the final position (after rotation)?

 

[dlooman]

If Large Deflection is On, the element coordinate system rotates with the element so the results will be relative to the deformed position of the element.  Nodal coordinate systems don't rotate, even with large deflection on, so nodal results, like reaction forces are in the undeformed nodal coordinate system, frequently the global coordinate system if the node hasn't been rotated. 

[MHND]

thanks for your help 
yes the large Deflection is On.

First: can I have the element coordinate system relative to the deformed position? Because In the Elemental Triads, you can have the element coordinate system relative to the start position and not the end position. 

Second: That is, forces and moments from the probe refer to nodal constraint reactions in the undeformed coordinate system in the global coordinate system, but the moment is the force integrated about the surface using the moment arm. 
moment_arm  = (x+ux, y+uy, z+uz) - (sx, sy, sz)
In this case what is the surface and moment arm when I have just point (constrained node)!? I am confused about the moment reaction they get from probe on vertex?

[MHND]

In this example, the end of the beam will rotate, but the solution of the elemental triads will remain fixed in the starting position.