著者

小出 祐一 中川 正紀 福士 直己 石垣 博邦

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 C編 (ISSN:03875024)

巻号頁・発行日

vol.73, no.725, pp.66-71, 2007-01-25 (Released:2011-03-04)

参考文献数

9

被引用文献数

1 1

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In vibration design, we need to estimate the damping ratio to calculate the dynamic response of a structure. In particular, an estimation of its probability distribution is important to carry out so-called probabilistic design. For this paper, we developed an estimation method using the Bayesian approach to generate the probability distribution of the damping ratio from a vibration test with a small sample size. The Bayesian approach has special significance to engineering design, where available test data is invariably limited, for the approach can systematically incorporate subjective judgments based on experience or indirect information with observed data. We supposed that the probability distribution of the damping ratio has a normal distribution. Therefore, we applied the Bayesian approach to estimate unknown parameters of the distribution. In addition, we compared this method with a method of moments classified as a classical estimation and investigated the influence of sample size by conducting an evaluation test. With the results of our analysis, we came to the following conclusions. First, he true standard deviation of the damping ratio is less than 0.4, and the prior distribution of the standard deviation ranges between 0 and 0.5. (1) The estimated probability distributions determined by the Bayesian approach and the classical approach almost fully agree across more than 40 specimens. (2) The Bayesian approach provides good agreement, less than 10 percent error, with a true standard deviation for approximately 10 specimens. Even though the prior distribution of standard deviation ranges between 0 and 1.0, almost the same accuracy is obtained for approximately 10 specimens.

著者

小出 祐一 石垣 博邦 松永 博充 福士 直己 白木 智美

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集C編 (ISSN:18848354)

巻号頁・発行日

vol.77, no.774, pp.319-328, 2011 (Released:2011-02-25)

参考文献数

14

被引用文献数

1 1

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In the seismic design of the boiling water reactor, we need to estimate the dynamic insertion behavior of control rods into the core region to secure the safety of the reactor under seismic events. In particular, estimation of the insertion time is one of the most important design tasks affecting the scrammability of the reactor. We developed a numerical analysis model to predict the control rod insertion time under seismic events using multibody dynamics. The effect of the interaction force between the control rod and the fuel assemblies is considered in three-dimensional contact analysis. This interaction force causes resistance force acting on the control rod under insertion. The hydraulic control unit and the control rod drive, which provide the control rod with driving force, were modeled in the concentrated parameter system considering dynamic characteristics, such as the inertance of the working fluid in the scram piping and the capacitance of the working gas in the accumulator. The numerical analysis can simulate the realistic insertion behavior of the control rod by coupling these models together and using an interactive process to calculate how they interact. The validity of the numerical analysis model was confirmed by comparing the analytical results with the experimental ones. The results of our analysis showed that the numerical analysis model provides good agreement with the insertion time of the control rod.