PSI - Issue 79

Christoph Bleicher et al. / Procedia Structural Integrity 79 (2026) 239–247

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Nomenclature A Elongation at fracture Al Aluminum Cu Copper f Test frequency Fe Iron k Mn Manganese N Number of load cycles N Cycles to failure Ni Nickel N k k* K t

slope of the SN curve before the knee point slope of the SN curve after the knee point

Stress concentration factor

Number of load cycles at the knee point

N lim

Limit number of cycles

Sn R σ R m

Tin

Load ratio under stress

Tensile strength Yield strength Scatter band

R p0.2

T σ

Zn Zinc σ a,n

Nominal stress amplitude

Nominal stress amplitude for a probability of survival of 50%

σ a,n

1. Introduction Aluminum bronze alloys (CuAl bronze) are one of the most important cast materials used for the design of ship propellers, manifolds, fittings and other components that are subjected to high loads and a superimposed corrosive medium. The production of these large components with masses of several 10 tons means a high effort to the foundries to produce defect free, safe and sustainable products. This comprises in any case the understanding of the effect of defects and the local microstructure on the cyclic material behavior both in air and under corrosive environment. Even more, since these products have to endure more than 5·10 8 load cycles a demand arises for a fatigue assessment in the very-high cycle regime both under ambient air and corrosion. During the casting process, parameters such as the chemical composition of the alloy have a large influence on the local microstructure including defects and thus on fatigue strength. To design a reliable product, these influencing parameters need to be included in the product development process based on a fatigue assessment concept or a guide line. To assess the influence of corrosive environment on the fatigue and lifetime of aluminum bronze alloys the research project “Bross” was conducted. Up to now, the fatigue strength of aluminum bronzes has only partially been investigated in literature. Nonetheless, no design concept for the influence of corrosion in seawater has been proposed that allows the design of thick-walled components on the basis of fatigue strength values including also local scatter bands and the influence of casting process parameters. However, the fatigue strength of aluminum bronzes in air, distilled water and artificial seawater was investigated in Dies (1966) in form of a AlBz10Fe alloy for forged wrought material. In comparison to air, a significant reduction in the cyclic fatigue strength of these alloys was found when investigated in artificial seawater. Further investigations regarding the influence of the wall thickness of aluminum bronze was done by Wenschot (1983) in air and seawater. The material specimens were removed from cast samples and serial propellers with mean values for the chemical composition of 4.75 % Fe, 9.5 % Al, 1.5 % Mn and 5.0 % Ni. Wenschot (1983) reports a