Computational model for carbon diffusion and methane formation in a ferritic steel during hydrogen attack

Hydrogen attack is a material degradation process which involves partial dissolution of the microstructure in favor of the growth of methane-filled cavities. The various physical-chemical processes involved are strongly coupled. We present a numerical microstructural model for two of these processes, based on a variational approach. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved

Low-density series expansions for directed percolation IV. Temporal disorder

We introduce a model for temporally disordered directed percolation in which the probability of spreading from a vertex $(t,x)$, where $t$ is the time and $x$ is the spatial coordinate, is independent of $x$ but depends on $t$. Using a very efficient algorithm we calculate low-density series for bond percolation on the directed square lattice. Analysis of the series yields estimates for the critical point $p_c$ and various critical exponents which are consistent with a continuous change of the critical parameters as the strength of the disorder is increased.Comment: 11 pages, 3 figure