302 超微細結晶粒P/Mアルミニウム合金の変動荷重下における疲労き裂進展挙動(GS-4 疲労・クリープ)

概要

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Fatigue crack growth tests were carried out using CT specimens of ultra fine-grained P/M (Powder Metallurgy) aluminum alloy of which grain size was from 200 to 500nm. Fatigue crack growth behavior was investigated under constant amplitude and repeated two-step load sequences. It was found that roughness-induced crack closure played an important role in closure behavior of this material although the roughness of fracture surface was smaller than the other conventional aluminum alloys, as the crack tip opening displacement (CTOD) is rather small due to the low fracture toughness. Under repeated two step loading, crack opening load was smaller than that under constant amplitude loading with the same K as the high level load, and the crack growth retardation caused by the load history was not prominent comparing with other aluminum alloys.
2004-03-17