Fatigue Behavior of Sheet-Bulk Metal Formed Components

Functional components manufactured by sheet-bulk metal forming will commonly be exposed to cyclic loading during operation. Due to the cold forming during sheet-bulk metal forming, work-hardening occurs and ductile damage is induced in the form of voids in the microstructure. To predict the influence of specific processing parameters on the components’ properties and their fatigue life, a fracture mechanics based fatigue life model was employed. Specifically, the evolution of ductile damage was analyzed and cyclic fatigue experiments as well as crack propagation experiments were carried out for different material conditions. Regarding ductile damage, the development of small to medium sized voids could be observed for an increasing degree of deformation. The fatigue model allows inferring the crack length by inverse calculation. It could be shown that the calculated initial crack lengths correspond well with the determined defect size caused by ductile damage. The parameterized fatigue model allows estimating the fatigue life of sheet-bulk metal formed components manufactured by various processing routes and exposed to different load cases and thus enables a fatigue life related process design.