Identify load proportionality at a notch

Hi 

I want to check the stress biaxiality at critical location in FE model. the load applied is  proportional cyclic but the at stress concentrator lacation and due to the complex load states (multi-axial) I am not sure if the stresses proportional or not as that will effect the critrerion suits this case.

Is the check to be for the principle stress ratio (S2/S1) only.

should the check be conducted on one line of nodes (along the maximum stress location), or all node/or element in the area surround the stress concentrator.

Thanks