The objective of this paper is to determine the very long fatigue life of ferrous alloys up to 1

In this study, the effect of pre-existing corrosion pits on the fatigue behavior of 7075/T6 aluminium alloy in very long life range and in the near threshold regime was investigated by using piezoelectric accelerated fatigue test. The results indicate that the presence of pre-existing corrosion pits, produced by 1-day, 4-day, and 7-day immersion in salt water significantly reduces the fatigue life of the aluminum alloy by a factor of 10-100.

The effect of inclusions on crack initiation and propagation in gigacycle fatigue was investigated experimentally and analytically in six high strength low alloy steels. Fatigue testing was performed at very high numbers of cycles through ultrasonic fatigue tests at 20kHz. Inclusions at subsurface are common sites for fatigue crack nucleation in these alloys when cycles to failure was 107 cycles. A significant change in the slope of the S-N curve was observed accompanying the transition from surface to subsurface crack initiation. A deterministic model has been developed to predict the total fatigue life, i.e. crack initiation life and crack propagation life, from the measured inclusion sizes. The predicted fatigue strength agreed reasonably well with the experimental results. It is a tendency that smaller inclusions are associated with longer fatigue life. The results demonstrated that the portions of life attributed to subsurface crack initiation between 107 and 109 cycles are>99%. Science Ltd. All rights reserved.

Corrosion-fatigue is one of the damage mechanisms affecting the structural integrity of the aging aircraft. Simple analytical and probabilistic models for predicting pitting corrosion and corrosion-fatigue life in aluminum alloy 2024/T3 used in aircraft structures is presented. The developedmodel includes the effect of the interaction of cyclic load and the corrosive environment on the fatigue life, and considers all stages of the corrosion-fatigue process. The probabilistic model investigated considers the uncertainties in initial pit size, corrosion pitting current, and material properties due to scatter found in the experimental data.The analytical model shows very good quantitative agreement with the existing experimental data and analytical models over a wide range of parameters. The results predicted that the crack initiation life varies approximately 10-40% as compared to crack propagation life in corrosion-fatigue problems.