I think the question is wrong! Kt is a factor for nominal theory. In FE you can calculate local stresses. Naturally you can calculate in some special cases the Kt. Forexample: You can create a model for a notched speciment. YOu can aply the a simple tension force on it. In that case you can see the Von Mises stress in the smooth area and in the notched area. You can devide them. This will be the Kt. (Remark: Some fatigue software uses the notch theory. These software compare the result stress distribution with a simple bending or tension compression stress distribution. )
Best regards,
Irwin