Hi there, 

I have met a problem about applying torsional load on a annular surface show on the picture. From my understanding, only surface traction can possibly realize torsional load on a surface. However, so far I cannot ​​​​​​​find out how to make it a torsion in a full circle. I can only have it apply on half circle as in the first picture. If I mirror the model by ZX plane, the mirrored part will have a torsion in opposite direction. Does any one has any suggestions or should I use other load types?

Also, may I ask does the surface traction come with unit in MPa?

Cheers.