IHS ESDU Fatigue strength of steel stud threads under axial and combined axial and bending loading. 85004

ESDU 85004 gives stress-endurance curves through the results extracted from the literature of some 80 constant amplitude fatigue tests on five different types of studs with machined threads torque-tightened into a steel block. The studs failed at the first loaded thread in the block; for fatigue failures in the thread of the nut, see ESDU 84037. The relative merits of the five designs are compared. In particular, the provision of a proper seating allows the initial tightening torque to give a beneficial pre-tension that relieves the load subsequently applied to the stud thread by the assembly of a component on it. A discussion of the load paths through an assembly is included since detail design affects that and hence the fatigue strength. A worked example illustrates how such an analysis is used to establish the fatigue strength of a stud in a practical situation.