Propagation of Fatigue Cracks in Notched Specimens of EN AW 7475-T761

Abstract:

The influence of single overloads on the fatigue crack initiation and propagation of an EN AW 7475-T761 alloy was investigated using SEN-specimens. Into a base load with an amplitude of 80 MPa and an Rvalue of R=-1 tension compression overloads with an amplitude of 240 MPa have been introduced every 10,000 cycles. The crack length was measured with a DC-Potential drop method. The experiments have shown that cracks are initiated in the first 5% of the total lifetime and, therefore, the cyclic lifetime is dominantly determined by crack propagation. The investigation of the crack surfaces exhibit that a different number of individual cracks propagates within the specimens. The differences in the cyclic lifetimes indicate that the interaction between these cracks directly influences the cyclic lifetime. This shows that the differences in the crack propagation behaviour are responsible for the scatter of the determined cyclic lifetimes.

• Periodical: Key Engineering Materials (Volumes 592-593)
• Pages: 789-792
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.592-593.789
• Online since: November 2013
• Authors: Jürgen Bär, Gero Wilhelm
• Keywords: Crack Propagation, Fatigue, Overload, Potential Drop Method

References

[1] Polak J., In: Ritchie, R.O., Murakami, Y., editors. Comprehensive structural integrity. Cyclic loading and fracture, Vol. 4. Elsevier; (2003) 1–39.

[2] Bär, J. and Wilhelm, G., In: Proceedings of the 19th European Conference on Fracture (ECF-19), Kazan, Russia, 26-31 August.

[3] Preibisch,S., Saalfeld, S., Tomancak, P., Bioinformatics, 25 (2009), 1463-1465.

[4] Zerbst, U., Madia, M., Hellmann, D., Engineering Fracture Mechanics 82 (2012) 115–134.

[5] Wu, W.F., Ni, C.C., Probabilistic Engineering Mechanics 18 (2003) 107–118.

[6] Kocańda, D., Jasztal, M., International Journal of Fatigue 39 (2012) 68–74.