Ratio of Flank Loads of Screw Threads in Hollow-bolt

Mechanical behaviors of a hollow-bolt are analysed by a finite element method (FEM) which can deal with the contact conditions of threaded portions correctly. The characteristics of the load of No.1 thread, which is the nearest one to the bearing surface of a nut, and the stress concentration at the root of No.1 thread of a bolt are discussed by varying the inside diameter of a hollow-bolt, the friction coefficient at pressure flank and the nominal diameter. The results obtained indicate that the values of the load of No.1 thread and the stress concentration factor show opposite features to the variations of the inside diameter and the nominal diameter. Therefore, the evaluations of strength of a hollow-bolt based on the load distribution are not always correct.