positioning tab in mast-mode coupling

[biz]

think of a hub made of a very soft material. thinking that the hub is stuck and the shaft in rotation, you would see the material flowing (sliding plan-cut-) in the inner part, the one you did not color. the cutting plane is just that black circular line inside the crown.
It is true that we must also consider a torque component for the colored area of black.
In that case, as you thought it was, great lines, correct. yields first to cut or torsion zone?

However, verification is important. when checking I would do a numerical analysis, considering the real geometry of the section.

thinking about the mechanism of surrender, the gross hypothesis I made, I repeat, is far enough from reality, as there is only a small part that makes strength against the hub, that is to the shattering (a face). it would be interesting to do an analysis to the finite elements, as they do not exist, that I know, analytical formulas to determine the outer diameter of the hub.