The bolts and nuts are widely used in various fields as important joining elements with long history. However, screw loosening is easily induced by vibration and external loads, and sometimes causes very serious accident without notice. In this paper, a special stud bolt named Super Stud Bolt (SSB) is studied, which can prevent loosening effectively. Between the upper threads and the lower threads, there is a thin walled tube which can be deformed along the axial direction so that the phase difference is designed and SSB is developed. During fastening, this phase difference induces the contrary forces on the surfaces of the upper threads and the lower threads, which bring out the anti-loosening performance. In this stydy, both courses of processing and fastening are simulated, and the relationship between axial force and displacement is illustrated with the finite element method. In this analysis, the large plastic strains and elastic-plastic large deformation theory are applied to 4 nodes axial symmetric FEM models. Through the comparison among the results, the desirable range of the phase difference of lower and upper threads is decided. Since the thin walled tube is the heart of anti-loosening mechanism, optimum original dimensions are discussed in this study.
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