Loosening resistance torque usability for anti-loosening performance assessment in frictional threaded fasteners

All newly developed anti-loosening fasteners, before mass production, should be tested for suitability for their intended application. Currently, prevailing torque (Tp) is a conventionally used assessment parameter. Previously we proposed loosening resistance torque (TuR) as a more reliable anti-loosening metric. However, its validity was proved only in one type of fastener. This study aims to validate TuR applicability to a variety of structurally different frictional fasteners. Using experiments and the finite element method, we examined five types of frictional fasteners under the same TuR condition. Then we did the loosening tests where the TuR values were equal in all fastener types. The results demonstrate that TuR magnitude is directly proportional to the fasteners' anti-loosening ability independently of the nuts' structure. As opposed to TuR, Tp cannot serve as such a universal indicator of loosening resistance. In addition, we developed a relatively simple TuR measurement method. Compared to the Junker and NAS vibration tests, our method is less laborious and does not require sophisticated equipment. Thus, our method can be useful for on-site fastener assessment. Moreover, being a feasible alternative to conventional tests, the TuR measurement might be helpful for engineers and researchers for quick fasteners' evaluation.