序論Kazuki Shibanuma, Shuji aihara and Shigeru OhtSuka Synopsis : It is known that a cracking of brittle phase such as cementite works as a trigger of cleavage fracture initiation. This study shows a microscopic observation of cracked cementite and its quantitation of the cracking nucleation in ferrite-cementite steels. Seven steels with various sizes of microstructures are produced by laboratory scale vacuum melting and rolling. The cementite particle thickness was measured by SEM observation and image analysis. Tensile tests using circumferential notched round bar specimens were conducted. A trace analysis was carried out to identify crystal plane of cleavage surface of cementite using EBSD analysis. The results indicated a possibility that the cleavage surface is formed on (010)-plane. Distributions of length of cementite particle crack were measured for various strain and stress conditions. In order to understand a microscopic internal stress of cementite particle, a finite element analysis was carried out. An estimation formula of internal stress of the cementite particle from macroscopic stress and strain was developed based on the numerical results. A nucleation of cementite cracking should be quantitated based on a stochastic framework because of its uncertainties such as distribution, shape, orientation and so on. The measured distributions of cementite particle thickness and crack length were approximated by introducing a distribution function considering upper limit. Probability of nucleation of cementite cracking was formulated as a function of cementite particle thickness and macroscopic stress and strain, based on the approximated distribution function and the estimation formula of internal stress of the cementite particle.

It is known that a cracking of brittle phase such as cementite works as a trigger of cleavage fracture initiation. This study shows a microscopic observation of cracked cementite and its quantitation of the cracking nucleation in ferrite-cementite steels. Seven steels with various sizes of microstructures are produced by laboratory scale vacuum melting and rolling. The cementite particle thickness was measured by a SEM observation and an image analysis. Tensile tests using circumferential notched round bar specimens were conducted. A trace analysis of cleavage surface of cementite using the EBSD analysis indicated a possibility that the cleavage surface coincides with (010) plane. Distributions of cementite particle crack lengths were measured for various strain and stress conditions. In order to understand a microscopic internal stress of cementite particle, a finite element analysis was carried out. An estimation formula of internal stress of the cementite particle from macroscopic stress and strain was developed based on the numerical results. A nucleation of cementite cracking should be quantitated based on a stochastic framework because of its uncertainties such as distribution, shape, orientation and so on. The measured distributions of cementite particle thickness and crack length were approximated by introducing a distribution function considering upper limit. Probability of nucleation of cementite cracking was formulated as a function of cementite particle thickness and macroscopic stress and strain, based on the approximated distribution function and the estimation formula of internal stress of the cementite particle.

ABSTRACT:The facilitated transport of ethyl docosahexaenoate (DHA-Et) through the thin solution-cast perfluorosulfonated ionomer membranes has been studied. The carrier of DHA-Et was silver ion and was immobilized in the support ionomer membrane by electrostatic forces. In this system, the feed phase, membrane phase, and receiving phase had the same solvent. This system was already proved to be highly stable in our previous work. When ethanol/water (85/15) was used as the solvent, the DHA-Et permeance in the cast membrane was about four times higher than that in the commercial Nafion 117 membrane, due to the smaller membrane thickness. In the case of acetone solvent, a high selectivity of DHA-Et to ethyl oleate of 42 and a high facilitation factor of 153 were obtained. These membrane performances were superior to those of the Nafion 117 membrane. The effects of membrane preparation conditions, such as annealing temperature and kinds of polar solvents added to the ionomer solution before annealing, on the membrane performance was investigated in detail. Furthermore, small-angle X-ray scattering (SAXS) measurement was carried out to study the membrane structure. The experimental result suggests higher crystallinity in the cast membrane annealed at higher temperature.

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