A modification to the theory for the load distribution in conventional nuts and bolts

Abstract

A discrepancy between experimental results and the generally accepted theory for the load distribution occurring in the threads of a nut-bolt connection is highlighted. This occurs at the loaded end of the bolt and is caused by the changing geometry of the thread form of the nut as the thread emerges from the loaded face of the nut. The result is a thread form which is not complete and which is progressively more flexible as the loaded face of the nut is approached. This results in a reduction of the load carried by these incomplete threads. Sopwith's analytical theory has been modified to allow for this effect by using finite element analysis to determine the varying stiffness of the threads. The results of this modified theory compare well with those from three-dimensional photoelastic analyses of the loads in the threads of two bolts fitted with conventional nuts.