IHS ESDU Fatigue strength of steel screw threads with large root radii under axial loading. 67020

The results of 270 constant-amplitude fatigue tests on axially loaded solid steel bolts are presented in the form of S-N curves, the alternating stress being presented non-dimensionalised by the tensile strength of the material. Data are presented for threads form-rolled before heat treatment and heat treated before form rolled. All threads were of the unified type. Mean endurance curves and upper and lower limit of scatter curves within which 90 per cent of the data fall are presented. The data show that threads that are heat treated before form-rolling have the best fatigue endurance.