Three-dimensional finite element analysis during tightening of bolt-nut connection having slight pitch difference

type:Journal Article
In a wide industrial field, the bolt-nut joint is unitized as an important machine element although anti- loosening performance is always required. In this paper, the effect of slight pitch difference between bolt and nut is studied. The prevailing torque required for the nut rotation is analyzed before the nut touches the clamped body as well as the tightening torque after the nut touches the clamped body. The results show that a large pitch difference may provide large prevailing torque that causes an anti- loosening effect although a very large pitch difference may deteriorate the bolt tightening force even under a certain tightening torque. By taking into account the anti-loosening and clamping abilities, the most desirable pitch difference is proposed to improve anti-loosening.