In modern machinery, fasteners account for approximately 60% of the total number of machine parts, and thread connections are among the most commonly used forms of mechanical connections. The self-locking property of threaded fasteners may lead to loosening under variable loads, impacts, vibrations, or significant temperature changes, resulting in a decrease in preload.
The friction coefficient is an important design parameter that affects the material strength utilization and the anti-loosening performance of bolts. Bolts with a high friction coefficient have good anti-loosening properties but a smaller preload; conversely, bolts with a low friction coefficient have a larger preload but poorer anti-loosening properties.
This paper takes a certain specification of flange bolts as an example and explores the anti-loosening characteristics of bolts with different friction coefficients through transverse vibration experiments, providing a meaningful reference for the design and selection of the friction coefficient for high-strength connection bolts.
The anti-loosening methods for fasteners include theoretical analysis and experimental analysis. In the theoretical analysis, the forces on the thread are studied using the square thread as the research object, analyzing the impact of the friction coefficient on the anti-loosening performance of bolts. In the experimental analysis, bolts of the M101.2565-8.8 model were selected, and the friction coefficient was varied through different surface treatments for transverse vibration experiments.
The experimental results show that bolts with a higher friction coefficient exhibit a slower decay of axial force after vibration, indicating better anti-loosening performance; whereas bolts with a lower friction coefficient show a faster decay of axial force, indicating poorer anti-loosening performance. The conclusion is that the friction coefficient is a key factor affecting the anti-loosening performance of bolts. The selection of the friction coefficient requires a balance between anti-loosening performance and strength efficiency utilization, and considerations of the bolt model and application scenario must be taken into account.