Effect of Humidity on Fatigue Crack Propagation of Aluminum Alloys(Student Poster Session)

概要

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Aluminum alloys, A5083 and A7075, have the highest strength among the non-heat treated and the heat-treated aluminum alloys. They are widely utilized in the transportation systems because of their specific strength. Fracture mechanics design needs the information on the fatigue properties of the materials. The experiments were carried out to study the effect of the environment on the fatigue crack propagation of both alloys. The tests were conducted in the atmosphere of controlled humidity. The crack propagation behavior was analyzed using the Paris equation, da/dN = C(ΔK)^m . The constant, C strongly depends upon the environment, while the exponent, m is associated with the fracture mechanism. The ductile fatigue crack propagation shows m 〜 2 for both alloys at any environment. The constant, C is expected to be higher under wet conditions. The aggressive environment together with the frequency can increase the fatigue crack growth rate. The most aggressive environment was moisture which was composed of hydrogen and oxygen atoms. Hydrogen in the water can be decomposed into atomic state on the new aluminum surfaces which are introduced by the fatigue fracture and result in the acceleration of the fatigue crack propagation.
2001-10-20