ABAQUS evaluation of UR

[D_Bioeng]

Goodmorning,

I am simulating a simple bar fixed at one extreme and subjected to rotational displacement (UR) at the other end. From the odb I can evaluate the rotational displacement as UR3 (the bar can move only in the x-y plane, no out-of-plane motion are allowed).

However, if I take the coordinates of the reference point where the rotational displacement is applied at the first and last step and evaluate the angle between the two vectors, the angle is not equal to UR3. I applied a rotational displacement of 40° but from the evaluation from the coordinates of the reference point it results in a rotation of almost 20°, why it occurs?

Does anyone knows how ABAQUS calculate the rotational displacement UR?

thanks a lot for your help!

 

[FEA way]

UR is just the rotation of the reference point around itself (when it rotates in place). You can see it if you simulate torsion of a bar where the RP doesn’t experience any translational movement.

Basically, it’s the value of the (rotational) nodal degree of freedom. In this case, prescribed one.