Papers by Author: Hirohisa Oyama

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Authors: Kenji Machida, Gaku Mizukami, Hirohisa Oyama
Abstract: To evaluate the 3-D stress field inside a specimen from displacement data on the free surface obtained from the 2-D intelligent hybrid method, we developed the 3-D local hybrid method based on inverse problem analysis. In a previous study, when a uniform load was applied to a structure with a surface crack, it was demonstrated that the stress field was analyzed with high accuracy. In this study, the 3-D local hybrid method was applied to a structure with a surface crack subjected to bending load. However, a suitable solution was not able to be obtained on a bending problem. Therefore, another method was applied. The relative error between the J integral value of the whole model and the local model was compared, and accuracy was investigated. First, the variation of accuracy with width and thickness was examined. If thickness is increased, the relative error decreases as found in the uniform load case. Moreover, as width increases, the relative error decreases. However, even if width and thickness become large, accuracy does not necessarily become better. Therefore, the relative error was compared and a suitable hybrid size was examined.
Authors: Kenji Machida, Takanori Ueno, Hirohisa Oyama
Abstract: The interior stress field of the surface crack specimen subjected to a uniform tensile load has been successfully analyzed by the 3-D local hybrid method. In this study, it was examined whether the 3-D local hybrid method was applicable to the specimen subjected to the bending load. It has been understood that the decision of the optimal size of the local model is indispensable in the improvement of accuracy from the previous research. Then, the width and thickness of the local model were changed widely, and analyses were carried out to find the optimal hybrid local model size. Moreover, it was examined how to decide the optimal size of the hybrid local model with various crack length and aspect ratio of the specimen. The optimal size of the hybrid local model was examined from the comparison with the J integral of the whole model.
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