Study on Application of Fatigue Strength Reduction Factor and Stress Concentration Factor in Fatigue Analysis of Screw Threads

Taking the reactor pressure vessel as an example, the theoretical relationship of fatigue strength reduction factor (K_f) and stress concentration factor( K_t ), the reasonable values of K_f and K_t, the principles of equivalency of K_f and K_t in engineering project and the methods and techniques of how to use K_f and K_t in fatigue analysis are presented. An example of fatigue analysis for screw threads of reactor pressure vessel (RPV) stud with certain K_f is given. Consequently, definitions and differences of K_f and K_t are classified. Opinions on the application of K_f to high strength alloy stud are given, which can be used as a reference to the stud selection and the structure design in the engineering application.