Abstract
The bolts and nuts are widely used in various fields as an important joining machine element. It is known that failures usually happen at the root of the first bolt thread where the maximum stress concentration occurs. Moreover, loosening induced by the vibration and external loads is still problematic. Previously, a lot of special bolts and nuts were proposed; however, they are not useful for both of stress-reducing and anti-loosening. In this paper, a special nut is studied which can prevent the loosening and reduce the stress concentration at the root of the first bolt thread effectively. This kind of nut is designed with providing slightly different pitches between the bolt and nut, so that the prevailing torque is appearing that can prevent the loosening. Moreover, since the contact condition of each thread is different from the normal bolt and nut, the stress concentration at the first thread can be decreased. In this study, the anti-loosening performance is analyzed with the application of the finite element method. Moreover, the reduction of the stress concentration is considered under dynamic bolt axial forces.
