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This study aims to explore the variation law of threaded joints' loosening under transverse vibration and examine the mechanical behavior during the loosening process. Using a single-bolted, single-lap joint structure, a preload degradation model for bolted connections was developed. Friction torque and shear models were established for both the bearing surface and thread surface. The friction-shear model for the bearing surface and the thread surface caused by the additional bending moment was also established. The impacts of vibration amplitude, thread pitch, and initial preload on the variation of bolt preload were analyzed, and the failure mechanism of bolt loosening was explored through case studies. A transverse vibration test bed was designed and fabricated, and the preload decline curves under different parameters were obtained, verifying the rationality of the theoretical model between loosening factors and the preload. The results indicate that when the loosening torque exceeds the combined friction torque of the bolt head's bearing surface and the thread surface, the bolt reaches the critical condition for loosening. The friction torque between the bolt head's bearing surface and the thread pair's surface decreases when the vibration amplitude increases. When the vibration amplitude reaches the critical value, the bolt loosening further accelerates. A higher initial preload makes loosening harder to reach and slows preload decay. Under identical conditions, larger vibration amplitude and thread pitch accelerate preload decline.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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