Stress concentration factors within bolt-nut connectors under elasto-plastic deformation

The elasto-plastic stress distributions within straight and tapered bolt-nut connectors are studied in this paper by using the virtual contact loading method. Based on a simplified axisymmetrical model, the virtual contact loads are used to simulate the elasto-plastic contact phenomena between the mating screw flanks and the detailed stress and load distributions along the threads have been found. The calculated results show that dangerous stress occurs at the thread roots and the first pair of thread roots are the first to undergo the plastic deformation.