Review on anti-loosening methods for threaded fasteners

Threaded fasteners naturally tend to loosen under vibration, impact, or alternating thermal load. Various anti-loosening methods or strategies are widely applied for preventing loosening, including a few anti-loosening designs and anti-loosening structures. In this review, a variety of influencing factors that improved the anti-loosening ability and helped guide the anti-loosening designs of threaded fasteners are summarized. Second, the anti-loosening structures are classified into two categories, that is, conventional and new-style anti-loosening structures. The former refers to widely used structures in engineering applications, while the latter refers to novel structures not available in the markets. The research on the evaluation and comparison of various conventional anti-loosening structures in terms of preventing loosening is summarized in detail and the new-style anti-loosening structures from five different aspects are also surveyed based on different structural characteristics. In the future, the effects of combined factors on loosening should be considered to achieve optimal anti-loosening designs. More quantitative research on the mathematical relationship between the anti-loosening performance of conventional structures and structural parameters must be conducted. Furthermore, novel structures with excellent abilities to prevent loosening are needed, and issues of difficulties in installation and disassembly, low strength at thread, large deformation, and temperature dependence also need to be addressed.