Fatigue life estimation of treated welded attachments via High Frequency Mechanical Impact treatment (HFMI-treatment)

Book chapter, 2021

High-Frequency Mechanical Impact (HFMI) is one of the newest post-weld treatment methods that can be used to repair cracks in welded structures. The main effect of this method is to extend the fatigue life by putting the cracks under compression. Linear Elastic Fracture Mechanics (LEFM) is to be used as an analysis tool accompanied by Paris law. Crack growth curves are presented in this work. The effects of the induced residual stress, the initial crack size, the clamping stress, and the stress range are all incorporated in the analysis. Subsequently, the analysis results are compared to experimental results obtained from fatigue testing on transverse non-load-carrying welded attachment. The scatter in fatigue test results is found to be mainly attributed to the scatter in both the induced residual stresses and the variation in the existing crack sizes before treatment. Moreover, the analysis could successfully expect at what conditions the crack would not propagate through incorporating the concept of threshold stress intensity factor.