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Behavior of stress-corrosion crack in a high-strength aluminum alloys structure
Bore Jegdić
Stress-corrosion cracking (SCC) tests are performed in the laboratory using the fracture mechanics approach (constant crack opening displacement COD methodology). Double-cantilever beam (DCB) specimens have been used for testing SCC high-strength aluminum alloy in distilled water and the 3.5% aqueous solution of NaCl at room temperature. These SCC data are applied for predicting the behavior of the crack in the structure (exposed to simultaneous effects of tensile stress and corrosive environment) as well as for calculating the lifetime of a structure. In the cases when existing SC crack relatively fast propagate in the given structure, possibility to reduce the applied stress to the value when the crack stops to grow (KI is lower than KISCC) is discussed, as well as the possibility to apply the same alloy with other heat treatment or to choose other metallic material which provides higher SCC resistance (higher KISCC and lower SC crack propagation rate). A general block scheme of the design/performance model (adapted from Jackson and Wight) is given for the cases when SC has a dominant role during exploitation.
Key words: stress-corrosion cracking (SCC), fracture mechanics testing, aluminum alloys, threshold stress intensity factor KISCC, SC crack propagation rate, nondestructive evaluation.
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