1985 年 3 巻 3 号 p. 497-504
In this work, the trapping effect of inclusions on hydrogen diffusion was quantitatively evaluated and numerical method were applied to analyze local hydrogen concentration at the crack tip. The results obtained in this report are summarized as follows;
(1) The validity of hydrogen diffusion model being based on effective hydrogen concentration was confirmed in the case of varying micro structure, plastic strain and inclusion contents.
(2) The trap parameter, by which micro structure, plastic strain and inclusion contents were quantitatively evaluated, was proposed. And this trap parameter was applied to hydrogen diffusion equation based upon the concept of effective hydrogen concentration.
(3) Hydrogen concentration at the crack tip was analyzed by using the finite element: method based upon above hydrogen diffusion equation. From this result it was appeared that hydrogen concentration at the crack tip was slowed down and the maximum content of hydrogen accumulation was decreased with increasing inclusion contents. Furthermore, it was shown by this analysis that with increase of inclusions critical hydrogen concentration for crack initiation was lowered inspit of the incuvation time being inceased. This result agree with the previous conclusion obtained from the model of hydrogen embrittlement.
(4) Also FEM analysis was carried out in the case of considering stress induced hydrogen diffusion. And similarly above effect of inclusions was shown.