A study on the thickness effect on the bending correction coefficient for the fatigue strength of cruciform joint

Abstract

Fatigue strength of a cruciform joint subjected to bending stress is studied under various combinations of main plate thicknesses and attached plate thicknesses, using FE analysis and Siebel diagram. Conventional approach to deal with the fatigue strength under bending used to be to multiply the stress range by the bending correction factor of 0.8, and apply the typical S-N curve obtained from axial fatigue test. However, in this study, it was revealed that axial force and bending have different sensitivity of main plate thickness and attached plate thickness to the fatigue strength, and therefore, actual bending correction factor depends on the combination of the thicknesses. As a result, the authors proposed an approximate formula of bending correction coefficient covering all the combinations with an appropriate safety margin.