Stresses built up in a rotating disk

I am trying to analyze the stresses built up in in rotating disk. This disk is not subjected to any external loading. Only forces applied is centrifugal forces due to rotation.

When I try to model the problem using Structural Mechanics>Solid Mechanics (solid) from COMSOL 4.2 it allows me to enter a linear velocity as a Prescribed Velocity. But I cant enter the rotational or angular speed.

Can I implement this problem in COMSOL using this Prescribed Velocity functionality?or Is there any other way to analyze the stresses in this rotating disk.?

Thank You Very Much.

Shehan