Effect of Lateral Diffusion on Hydrogen Permeation Measurement in Thick Steel Specimens
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A finite element analysis is proposed to study the effect of specimen dimensions on lateral diffusion ofhydrogen during hydrogen permeation flux measurements. The error of measurement on thick specimensbecause of 1D diffusion approximation may be as much as 70%. A critical condition for accurate measurementsis to designate the area of hydrogen monitoring/exit surface smaller than the area of hydrogen charging/entrysurface. For thin to medium thickness specimens (ratio of thickness to specimen radius of 5:10 and below),the charging surface should be maximized and the monitoring surface should be minimized. In case ofrelatively thick specimens (ratio of thickness to specimen radius above of 5:10), use of a hydrogen-diffusionbarrier on the specimen boundaries is recommended. It would completely eliminate lateral losses of hydrogen,but cannot eliminate the deviation towards 2D diffusion near the side edges. In such a case, the chargingsurface should be maximized and the monitoring surface should be as closer in dimension as the chargingsurface. A regression analysis was carried out and an analytical relationship between the maximum measurementerror and the specimen dimensions is proposed.
Abstract
A finite element analysis is proposed to study the effect of specimen dimensions on lateral diffusion ofhydrogen during hydrogen permeation flux measurements. The error of measurement on thick specimensbecause of 1D diffusion approximation may be as much as 70%. A critical condition for accurate measurementsis to designate the area of hydrogen monitoring/exit surface smaller than the area of hydrogen charging/entrysurface. For thin to medium thickness specimens (ratio of thickness to specimen radius of 5:10 and below),the charging surface should be maximized and the monitoring surface should be minimized. In case ofrelatively thick specimens (ratio of thickness to specimen radius above of 5:10), use of a hydrogen-diffusionbarrier on the specimen boundaries is recommended. It would completely eliminate lateral losses of hydrogen,but cannot eliminate the deviation towards 2D diffusion near the side edges. In such a case, the chargingsurface should be maximized and the monitoring surface should be as closer in dimension as the chargingsurface. A regression analysis was carried out and an analytical relationship between the maximum measurementerror and the specimen dimensions is proposed.
참고문헌 (13)
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