Evaluation of the J Integral of a Surface Crack by the Three-dimensional Local Hybrid Method

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.