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An elastic-plastic constitutive law embedding cohesive cracks with plasticity-induced damage is proposed to realize degradation of strength and toughness under cyclic loading. A conventional elastic-plastic constitutive law with isotropic and kinematic hardening is combined with our cohesive-force embedding damage model to realize plastic deformation and fracture behavior under monotonic and cyclic loading by solving two kinds of conditional equations. One of them is local balance equation between cohesive traction and principal stress and the other is yield function with nonlinear isotropic and kinematic hardening law. The relationship between the cohesive traction and the crack opening displacement is determined by a cohesive zone model associated with energy release rate to represent process of stress release due to formation of crack surface. In addition, a new plasticity-induced damage is introduced into the cohesive zone model to realize the degradation of the tensile strength and the energy release rate caused by the accumulated plastic strain. On the other hand, the difference of the plastic deformation under various ranges of cyclic loading is represented by additional hardening law depending on a memory surface that is corresponding to plastic strain range. After the material parameters are identified from three experimental results under monotonic and cyclic loading, the capability of our proposed constitutive law is demonstrated by prediction of residual tensile strength and breaking strain of a metal after cyclic loading.

Using a high purity sapphire plate, the corrosion rate of alumina in molten carbonates was measured with a laser microscope. Results indicate that, when the CO2 partial pressure in the atmospheric gas is low and the operating temperature is high, the corrosion layer increases in thickness in proportion to a two-thirds power with time. As lithium aluminate, the corrosion product, tends to assume a granular shape and corrosion layers are likely to be porous, molten carbonates are believed to readily reach the surface of the alumina. For this reason, this phenomenon deviates from the square root rule which is, in general, applied in evaluating the corrosion of materials. When an alumina plate, blended with silica, is immersed in molten carbonates, part of the silica dissolves into the molten carbonates, thereby increasing the alumina plate surface roughness. The contact area between the alumina and the molten carbonates increased, resulting in increased corrosion.

Many concerns have been raised concerning the mechanism whereby the thickness of electrodes in molten carbonate fuel cells is reduced over time. We reported in a previous paper that when CO2 partial pressure in the atmospheric gas is low and the temperature of molten carbonates is high, porous nickel oxide deforms easily under compressive stress. In this paper, the mechanism of cathode deformation, which has not yet been clarified, was investigated. Results indicate that cathode deformation occurs when particles in a highly stressed porous nickel oxide dissolve and then reprecipitate to adjacent particles which are less stressed.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 152.14.136.77 Downloaded on 2015-03-17 to IP

The electrolyte tile of molten carbonate fuel cells consists of a matrix prepared from lithium aluminate powders impregnated with molten alkaline metal carbonate. The increase in lithium aluminate particle size in the molten carbonate accelerates degradation of the electrolyte tile. We investigated the mechanism of lithium aluminate particle growth. Results indicate that, although the particles basically grow through a dissolution‐precipitation mechanism, with lithium aluminate passing through the molten carbonate, growth tends to occur readily in the interior of agglomerates resulting from the coagulation of fine particles. As fine pores fill fully with lithium aluminate precipitate in the interior of the agglomerates, and then are amalgamated into other surrounding particles, the particles can grow at higher rates than individual particles, which grow by the dissolution‐precipitation mechanism.