TL;DRAbstract
The elements of a methodology are described to calculate the scatter in fatigue lifetime which arises from statistical variations in alloy microstructure from sample to sample within a uniform heat of material, and from variations in mean grain size and in the ductility of the alloy surface from heat-to-heat. The modeling is formulated for certain structural aluminum alloys for which the dominant mode of crack initiation is by fracture of constituent particles near the alloy surface. For one of these, an Al 2219-T851 alloy, small amounts of internal hydrogen at contents less than 1 ppm are found to affect surface ductility and both crack initiation and early growth. The application of models of crack initiation and short crack growth to predict the combined effects of grain size and hydrogen on fatigue lifetime is demonstrated for smooth bar specimens of two heats of Al 2219-T851. Experiments confirm predictions that fatigue lifetime is increased by decreasing both grain size and alloy
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The elements of a methodology are described to calculate the scatter in fatigue lifetime which arises from statistical variations in alloy microstructure from sample to sample within a uniform heat of material, and from variations in mean grain size and in the ductility of the alloy surface from heat-to-heat. The modeling is formulated for certain structural aluminum alloys for which the dominant mode of crack initiation is by fracture of constituent particles near the alloy surface. For one of these, an Al 2219-T851 alloy, small amounts of internal hydrogen at contents less than 1 ppm are found to affect surface ductility and both crack initiation and early growth. The application of models of crack initiation and short crack growth to predict the combined effects of grain size and hydrogen on fatigue lifetime is demonstrated for smooth bar specimens of two heats of Al 2219-T851. Experiments confirm predictions that fatigue lifetime is increased by decreasing both grain size and alloy
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