Corrosion Fatigue Mechanism Of High Strength Aluminum Alloy And Full-life Engineering Model For Corrosion Fatigue

Corrosion fatigue is the fracture behavior of structures under the combined actions of fluctuating loads and corrosive environment. The available data show: More than half wrecks of aeroplane is relative to corrosion or corrosion fatigue. It is obvious that corro- sion fatigue is very universal and dangerous. With respect to the typical aircraft materiall agent system of high strength alumin- um alloy/ Nacl solution, the present paper carries out the following work: (1) The corros- ion fatigue mechanism of high strength aluminum alloy. (2) The corrosion fatigue experiment of high strength aluminum alloy. (3) The full-life engineering model for corrosion fatigue (1) Corrosion fatigue mechanism of high strength aluminum alloy According to the peculiarity of the crack (or notch)/ agent system, the mechanics- electrochemistry testing of high strength aluminum alloy in3.5%Nacl solution is designed and carried out. With reference to the mechanics-electrochemistry data and the stress- strain analysis near crack-tip (or notch-tip), the paper explores the corrosion fatigue mechanism of high strength aluminum alloy. The results show: The corrosion fatigue cracking mechanism of high strength aluminum alloy is due to the embrittlement of material and mild corrosion; The corrosion fatigue crack propagation is due to the embrittlement mechanism of material. (2) Corrosion fatigue experiment of high strength aluminum alloy With respect to 7475-T761 and LY12CZ aluminum alloy 梩wo materials commonly used in aviation region, the corrosion fatigue experiment under spectrum loads is carried out. The experiment involves the following contents: (1) Exploring the influence on structure endurance from different corrosion environments, different fastener-holes, and different loading frequencies; (2) Obtaining the basic parameters of structure initial fatigue quality (IFQ); (3) Supporting experiment data for evaluating the following full-life engineering model for corrosion fatigue. 桰II? (3) The full-life engineering model for corrosion fatigue. The paper develops a model of initial crack length and corresponding fatigue life, and establishes a model of fatigue crack propagation. Uniting the models, a full-life engineering model for corrosion fatigue is formed. In addition, the paper still puts forward a corrosion fatigue full-life analysis methodology basing on air environment and environment conversion factor. The results show: the fatigue full-life engineering model in the paper is very effective, economical and practical. The paper organically unites the research on corrosion fatigue mechanism, corrosio- n fatigue experiment, and the corrosion fatigue full-life analysis. It forms an idea to analyze corrosion fatigue. At the same time, it also supports a practical way for corrosion fatigue durability and damage tolerance analysis.