Fatigue analysis of threaded connections using the local strain approach

AbstractThe fatigue assessment of bolts and bolted joints is done using nominal approach, for example the German VDI guideline 2230 . For threaded components, the nominal approach and therefore the guideline is no more applicable. The calculation of the fatigue strength of threaded connections according to the German FKM guideline “Analytical strength assessment for machine components” does not lead to satisfying solutions. So far, there is no procedure for the assessment of general threaded connections. Based on the mechanics of the local strain approach the paper shows a fatigue assessment of threaded components and general threaded connections. Prediction results are compared to own experimental data from tested bolt and nut connections in different nominal sizes, different strength categories and subjected to high and low mean stress. A simple model to describe the local cyclic creep as a function of stress amplitude is developed. Furthermore the phenomena related to transferability (size, stress gradients, multiaxiality, crack growth) are discussed