Fatigue Crack Extension in an Incrementally Formed Tube

Fatigue properties of a thermally assisted incrementally formed steel tube with a fine graded microstructure were investigated. The gradation is characterized by a recrystallized microstructure on the one side and a recovered one on the other side. It was found, that fatigue cracks are significantly deflected when reaching the recovered microstructure, but only a minor influence on the local crack growth rate was observed during the experiments.