Methods of improving the fatigue strength of rail bolts
To improve the fatigue strength of rail bolts, changes in the structure of both the bolt and nut can be implemented, although considerations regarding increased manufacturing and construction costs must be taken into account due to their widespread use.
One method involves increasing the minor radius of the rail bolt's thread, thereby enhancing the maximum fillet radius. This can be achieved without altering the basic thread profile, allowing for a significant increase in the fillet radius.
Another approach involves adopting circular arc-shaped thread profiles for both the bolt and nut. While this method can further reduce stress concentration and improve fatigue strength, it may lead to higher manufacturing costs. However, by simultaneously adjusting the thread profiles of both the bolt and nut, the fillet radius can be significantly increased without increasing the manufacturing cost of the nut.
By increasing the minor radius of the bolt and matching it with a modified nut thread profile, the stress concentration factor at the bolt root can be reduced, resulting in a substantial improvement in fatigue strength and service life. Compared to conventional bolts, these structural changes can lead to a significant reduction in stress concentration and improve the overall fatigue strength of rail bolts.