Three-dimensional finite element analysis for prevailing torque in the screwing process of bolt and nut connections with pitch difference

In the previous studies, a bolt-nut connection with slight pitch difference was considered towards realizing anti-loosening performance and high fatigue strength through axisymmetric finite element method (FEM) as well as experiment. In this study, screwing process before the nut touching the clamped body is analyzed through three dimensional FEM. Then, it is found that the prevailing torque during this screwing process is in good agreement with the experimental result. The prevailing torque varies depending on the pitch difference from 5 to 25 Nm and anti-loosening behavior is confirmed. After the nut toughing a clamped body, the tightening process is also analyzed. For normal nut, the tightening force coincides with the empirical formula. The tightening torque and tightening force relations are discussed with varying the pitch difference.