Papers by Author: Yohtaro Matsuo

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Authors: Kazuhiro Yasuda, Yutaka Sekiguchi, Junichi Tatami, Yohtaro Matsuo
Authors: T. Kubota, K. Kuroki, Yohtaro Matsuo, N. Takahashi
Authors: Ryoichi Furushima, Yohtaro Matsuo, Tadashi Shiota, Kouichi Yasuda
Abstract: Damage evaluation for alumina/graphite refractory was conducted under uni-axial compressive loading. Apparent sonic velocity during a loading-unloading cycle was measured by ultrasonic method. Quasi-elastic-plastic behavior was observed in the stress-strain curve for each cycle. However, it is difficult to detect damage from the stress-strain curve during each loading- unloading cycle. On the other hand, using the result of change in apparent sonic velocity during a loading-unloading cycle, it is possible to estimate damage to some extent. The apparent sonic velocity kept approximately constant during the first loading process, but it decreased remarkably during the first unloading one. In the subsequent loading-unloading cycles, it increased in the loading process and decreased in the unloading one. Consequently, it is concluded that damage mechanism during the first loading-unloading cycle is different from that during the subsequent loading- unloading cycles for alumina/graphite refractory.
Authors: Tadashi Shiota, Yasuo Toyoshima, Kouichi Yasuda, Yohtaro Matsuo
Abstract: The photon emission accompanying fracture of a polycrystalline MgO was investigated at room temperature under N2 gas pressures from 10-4 to 105 Pa. At fracture, the ultraviolet, visible and infrared photon emissions instantaneously increased, and then rapidly decreased in most of the experimental conditions. However, in a N2 gas pressure of around 100 Pa, their peak counts lasted for about 10 milliseconds, and the amount of the UV photon emission was fifteen times larger than those obtained in the other N2 gas pressures. This abrupt increment in the emission was explained by the luminescence due to N2 gas discharge according to the classical Townsend’s theory. In conclusion, the photon emission accompanying fracture of a polycrystalline MgO mainly originated from the excited defects as reported by the authors previously, but the N2 gas discharge had a supplementary effect on the emission around a specific N2 gas pressure.
Authors: H. Nakashima, T. Kubota, Y. Murakami, H. Kondo, Shoichiro Tanigawa, K. Ohshima, Yohtaro Matsuo
Authors: K. Takashima, E. Nomura, K. Matsui, Y. Matsumaru, S. Iijima, Yohtaro Matsuo, K. Sato, S. Furuta, Takahiro Hirabayashi
Authors: Yohtaro Matsuo, Tadashi Shiota, Kouichi Yasuda, Kazuyuki Suzuki
Abstract: Strength reliability of ceramics depends on accuracy of parameters involved in the probability distribution function for fracture. The parameters are usually estimated by use of strength data. However, one may have additional information in the experiment, such as fracture cause data, fracture location data, flaw-size data and flaw-orientation data. In this paper, we will incorporate these additional information in the parameter estimation to improve the accuracy of the reliability. A new theory on the asymptotic variances is presented.
Authors: Kazuhiro Yasuda, Junichi Tatami, Tomohiro Harada, Yohtaro Matsuo
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