Superconductor Conduits: Fatigue Crack Growth Rate and Near-Threshold Behavior of Three Alloys
Three superconductor sheath alloys were fatigue-tested at 4 K to evaluate their suitability for International Thermonuclear Experimental Reactor magnets. The alloys tested were low carbon 316LN (0.018C), niobium-modified 316LN (0.0090, 0.05Nb) and nickel-based alloy 908. Threshold stress intensity factors ΔKth at 10−10m/cycle and near threshold fatigue crack growth rates were measured using the short crack simulation technique which avoids crack closure. Results indicate some advantage of 908 over the 316LN alloys. Also, microstructural effects on fatigue resistance are identified, mainly for 316LN (0.018C), where ΔKth increases with decreasing grain size.
KeywordsStress Intensity Factor Crack Closure Intergranular Fracture Fatigue Crack Growth Rate International Thermonuclear Experimental Reactor
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