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論文
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津田, 政明 ; 広瀬, 幸雄 ; 黒瀬, 雅詞 ; 松岡, 三郎 ; 黒部, 利次 ; 田中, 啓介
概要:
金沢大学大学院自然科学研究科<br />Stress corrosion tests were conducted by using SNCM439 steel in 3.5% NaCl solution under various cat
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hodic potentials. The crack profiles obtained in these tests were analyzed by fractal geometry. The results obtained were summarized as follows : (1) The more base the cathodic potential is, the slower the crack growth rate becomes and the larger the branching width becomes. (2) The profile of main cracks under cathodic polarization has the fractal character. The fractal dimension measured by the yardstick method is of no significance to the stress intensity factor and polarized electrode potential. (3) The fractal character of stress corrosion crack branching under cathodic polarization measured by the box counting method shows the single region for the case of only micro branching, and it shows the double regions for the case of mixture of micro and macro branching.
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論文
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土成, 昭弘 ; 保木井, 利之 ; 下林, 修 ; 金岡, 千嘉男
概要:
Changes in the structure and physical properties of porous magnesia ceramic containing TiO_2-Al_2O_3 matrix with TiO_2-Al_2O_3 molar ratio 0.96 and 15 wt% content were studied at different sizes and firing temperatures for controlling
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the pore shape. The shape of pore was complicated depending on the grain size and firing temperature, and pores were found to have a fractal nature. While the fractal dimension increased with increasing firing temperature for small grains, it decreased with increasing firing temperature for large grains. The fractal dimension of each MgO grain size tends to converge at a lower firing temperature which is close to the temperature at which the MgAl_2O_4-Mg_2 TiO_4 solid solution is formed. Specimens with small grains were found to shrink on firing, but the expansion was observed for large grained specimens. These phenomena were explained by the densification and molar volume of MgAl_2O_4-Mg_2TiO_4 solid solution and CaTiO_3 formed. From the above facts, it was possible to controll the pore shape by grain size and firing temperature.
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論文 |
論文
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土成, 昭弘 ; 保木井, 利之 ; 下林, 修 ; 金岡, 千嘉男
概要:
Changes in the structure and permeability of porous magnesia ceramic with a TiO_2-Al_2O_3 matrix with a TiO_21Al_2O_3 molar ratio of 0.96 were studied at different matrix contents. The shape of pores became complicated and pores
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tended to have fractal nature as the matrix content increased. It was proposed that the change of pore shape was caused by the increase in the amount of the matrix and its reaction with MgO grains. Both mean pore diameter and permeability showed a maximum at a matrix content, 10 wt% and 15%, respectively. On the other hand, the fractal dimension of pore shape changed from 1.39 at 5 wt% to 1.65 at 20 wt% of matrix. The fractal dimension changed sharply between 10-15 wt%. The permeability was found to agree well with that of a nonspherical particle system by using pore size modified by the its fractal dimension.
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