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Influence of rivet clamping stress on fatigue crack growth behaviour

Steel structures built between 1850 and 1940 are mostly made of mild steel. Riveting was the dominating joining technique. Fatigue failure respectively fatigue safety is of major concern if these structures are cyclic loaded such as bridges and hydraulic steel structures. Considering the period of operation of almost hundred years, the determination of the remaining fatigue life is the main aim of the assessment of these structures. The clamping force of the rivets significantly influences the crack propagation. Clamping stress is caused by the shrinkage of hot driven rivets while cooling down. The clamping force and the corresponding friction at the contact surfaces reduces notch stress at the rivet hole and thus also the crack driving force. In this paper, experiments for determining the rivet prestressing as well as the friction at the contact surfaces of riveted joints are presented. For typical design details numerical models are generated to determine notch stresses for uncracked components and stress intensity factors for cracked components. Regarding to crack growth rates, only few data have been published for old mild steels so far. Thus, the research program also includes experimental investigation of crack growth parameters.