A New Technique for Enhancement of Fatigue Life of Bolt-nut Connections

摘要

In this work, a new technique for enhancement of fatigue life of bolt-nut connections is introduced. In this technique, the threaded part of the bolt where it comes into contact with the nut is axially holed. A hole will have two opposite effects; (1) it will reduce the load carrying capacity of the bolt and (2) it will results in a more uniform load distribution. It is the subject of this investigation to find the optimum size of the hole for a specific bolt diameter. It is evident that a too small hole will have no significant effect on fatigue load and a too large hole, despite reducing the load concentration, will reduce the load capacity of the connection too. In this work, the metric bolt, M16 was selected for the experiments. Five diameters of 4, 5, 6 and 8 mm were examined in this work. The experiments were conducted under the load levels of 50 to 120 kN. The results suggest (ⅰ) the fatigue life remarkably increases for the holed specimens provided the optimum value for the hole diameter is determined and (ⅱ) the increase in fatigue life reduces as the load increases.