A New Method for Fatigue Life Improvement of Screws

ABSTRACT Motivated by the failure of several giant bolts, a new method to improve the fatigue strength of bolts has been developed. The new method is named CD bolt and stands for “Critical Design for Fracture”. Improved thread profile greatly reduces the peak stresses. Fatigue limit testing has confirmed that the new profile approximately doubles the fatigue strength of bolts as compared to more traditional profiles. Improved strength is for both the pre-stressed and non pre-stressed conditions.