40 research outputs found
On the relative efficacy of electropermeation and isothermal desorption approaches for measuring hydrogen diffusivity
The relative efficacy of electrochemical permeation (EP) and isothermal
desorption spectroscopy (ITDS) methods for determining the hydrogen diffusivity
is investigated using cold-rolled pure iron. The diffusivities determined from
13 first transient and 8 second transient EP experiments, evaluated using the
conventional lag and breakthrough time methods, are compared to the results of
10 ITDS experiments. Results demonstrate that the average diffusivity is
similar between the second EP transient and ITDS, which are distinctly
increased relative to the first EP transient. However, the coefficient of
variation for the ITDS experiments is reduced by 2 and 3-fold relative to the
first and second EP transients, confirming the improved repeatability of ITDS
diffusivity measurements. The source of the increased error in EP measurements
is systematically evaluated, revealing an important influence of assumed
electrochemical boundary conditions on the analysis and interpretation of EP
experiments
A phase-field chemo-mechanical model for corrosion-induced cracking in reinforced concrete
We present a new mechanistic framework for corrosion-induced cracking in
reinforced concrete that resolves the underlying chemo-mechanical processes.
The framework combines, for the first time, (i) a model for reactive transport
and precipitation of dissolved Fe2+ and Fe3+ ions in the concrete pore space,
(ii) a precipitation eigenstrain model for the pressure caused by the
accumulation of precipitates (rusts) under pore confinement conditions, (iii) a
phase-field model calibrated for the quasi-brittle fracture behaviour of
concrete, and (iv) a damage-dependent diffusivity tensor. Finite element model
predictions show good agreement with experimental data from impressed current
tests under natural-like corrosion current densities
On the relative efficacy of electropermeation and isothermal desorption approaches for measuring hydrogen diffusivity
The relative efficacy of electrochemical permeation (EP) and isothermal desorption spectroscopy (ITDS) methods for determining the hydrogen diffusivity is investigated using cold-rolled pure iron. The diffusivities determined from 13 first transient and 8 second transient EP experiments, evaluated using the conventional lag and breakthrough time methods, are compared to the results of 10 ITDS experiments. Results demonstrate that the average diffusivity is similar between the second EP transient and ITDS, which are distinctly increased relative to the first EP transient. However, the coefficient of variation for the ITDS experiments is reduced by 2 and 3-fold relative to the first and second EP transients, confirming the improved repeatability of ITDS diffusivity measurements. The source of the increased error in EP measurements is systematically evaluated, revealing an important influence of assumed electrochemical boundary conditions on the analysis and interpretation of EP experiments
A phase-field chemo-mechanical model for corrosion-induced cracking in reinforced concrete
We present a new mechanistic framework for corrosion-induced cracking in reinforced concrete that resolves the underlying chemo-mechanical processes. The framework combines, for the first time, (i) a model for reactive transport and precipitation of dissolved Fe2+ and Fe3+ ions in the concrete pore space, (ii) a precipitation eigenstrain model for the pressure caused by the accumulation of precipitates (rusts) under pore confinement conditions, (iii) a phase-field model calibrated for the quasi-brittle fracture behaviour of concrete, and (iv) a damage-dependent diffusivity tensor. Finite element model predictions show good agreement with experimental data from impressed current tests under natural-like corrosion current densities
On the Size Complexity of Non-Returning Context-Free PC Grammar Systems
Improving the previously known best bound, we show that any recursively
enumerable language can be generated with a non-returning parallel
communicating (PC) grammar system having six context-free components. We also
present a non-returning universal PC grammar system generating unary languages,
that is, a system where not only the number of components, but also the number
of productions and the number of nonterminals are limited by certain constants,
and these size parameters do not depend on the generated language