A rotational axial force is similar to a rotational spring because it produces a torque between two bodies at a point and about a rotational axis. However, a Rotational Axial Force uses a function expression to control the magnitude of the force rather than coefficients or a spline curve.
Figure 1 Axial Force and Rotational Axial Force
Figure 2 Rot.Axial icon of the Force group in the Professional tab