活量を変数とする物質拡散式の検討

概要

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The diffusion equation by which the local accumulation or segregation of mass can be analyzed is of non-Fickian type. Its equation form is not so simple as that of Fickian equation and it is, thus, difficult to solve mass segregation problems, especially in analytic manner. If the activity of diffusing mass instead of the concentration is taken as a variable in the equation the diffusion equation can be expressed by a very simple form as : ∂a/∂t=γ∇(D/γ∇a) In this equation the activity coefficient γ is a product of γ_0 and γ_p which represent the chemical potential term and kinetic potential term, respectively. The form of this diffusion equation is as same as that of heat conduction, γ being equivalent to a product of density and specific heat and D/γ equivalent to heat conductivity. It follows that the solution for the mass diffusion involving the local accumulation can be easily given by looking into the analytical solutions of heat conduction. More complicated problems such as hydrogen accumulation in the weldments can benumerically solved by making use of heat transfer computer programs.
社団法人溶接学会の論文
1979-09-05