Sensitivity of transfer functions of transport of hydrogen in elastic metals to the uncertainty of their parameters

Abstract

A comparison of sensitivity of the estimates of bulk elastic modulus of the M–H system and diffusion coefficient of hydrogen, acquired from three alternative transfer functions (TFs) of transport of hydrogen through a thin membrane specimen of metal, was performed with respect to the uncertainty of equilibrium concentration of hydrogen, its partial molar volume and thickness of the specimen. In most cases, the estimate of elastic modulus is more sensitive to these uncertainties than the estimate of diffusion coefficient, and the effects of uncertainty of the partial molar volume are of utmost importance. However, in the case of relatively small concentrations of hydrogen, uncertainty of the specimen’s thickness is most important for the estimate of elastic modulus acquired from one-port flux TF, while the estimates of both parameters acquired from the concentration TF are immune to the uncertainties discussed here. Nevertheless, other factors determine that for practical use the one-port flux TF is the most adequate of the three.