A parametric study of load distribution in bolt-nut joints is performed by the method of finite element contact analysis. The contacting surface is assumed unbonded and frictionless. Multi-body contact analysis is performed in elastic region under the assumption of axi-symmetric stress state.
Load acting on the first thread from the fastened plate is much greater than that on the other threads in the standard setting. But the load distribution is shown to be improved by making the center of contact force acting on the nut surface move outwards. Such a modification is possible by enlarging the gap between bolt shank and fastened plate or by inserting suitable washers.
Shape modification of the standard nut by the making a groove and a step on the nut surface is also suggested, which results in almost uniform load distribution and considerable decrease in the maximum stress of the joint.
