Effects of precrack environment on subsequent corrosion fatigue crack growth behavior of a squeeze-cast aluminum alloy
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This work was supported by the Korea Science and Engineering Foundation through the Center for Interface Science and Engineering of Materials. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9.
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Effects of Precrack Environment on Subsequent Corrosion Fatigue Crack Growth Behavior of A Squeeze-Cast Aluminum Alloy KAZUAKI SHIOZAWA and SHUMING SUN Corrosion fatigue occurs in all materials exposed to a corrosive environment and subjected to fatigue-type stresses. As in corrosion fatigue cracking, there are several aspects of the problem arising from mechanical, environmental, and metallurgical properties, which affect corrosion fatigue susceptibility. Corrosion fatigue crack propagation behavior will be obviously affected by different precrack conditions. However, studies regarding prefatigue crack environmental effects on subsequent corrosion fatigue crack growth and associated damage mechanisms are lacking to date. Recently, a relatively long through-thickness crack (prefatigue crack length >5 mm in compact tension (CT) specimen) corrosion fatigue result of a squeeze-cast aluminum alloy was investigated under different precrack environmental conditions. The fatigue crack growth results indicated an anomalous high growth rate in a near-threshold regime before a reduction in growth rate reached somewhat a plateau and increased to join the regular da/dN vs zlK curve at higher growth rates after a air precracking program, which is similar to the small surface fatigue crack growth behavior. It is now accepted that small surface cracks can grow at an accelerated rate in the near-threshold regime, compared with the growth rate of longer cracks, especially longer through-thickness cracks in fatigue condition.t.~.2.3J The typical "small" and "long" cracks geometries and fatigue growth behavior are illustrated in Figure 1. A lot of results and several models have been developed to describe this growth behavior of small fatigue eracks.t~-71 However, this anomalous rapid growth behavior of the relatively long corrosion fatigue crack, which is just an associated effect of precrack environment on subsequent corrosion fatigue, is not clear. The present article gives a corrosion fatigue growth behavior of a through crack artificially obtained from long cracks relating to a different experimental p
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