Papers by Author: Zu Guang Zhang

Abstract: Health assessment of a structure is various. In architecture and civil engineering, a natural frequency is calculated by conducting the frequency analysis of the response waveform of the structure. The natural frequency measurement has been performed with a speedometer, an acceleration sensor and a laser Doppler velocimeter, but possibility of the evaluation of the natural frequency by the digital image correlation method was examined mainly. In the case of the digital image correlation method, if a picture and time are connected, the displacement response of the structure is obtained. Hence, we considered the applicability of it to the vibration phenomenon. We carried out displacement comparison with the finite element method, and then investigated the accuracy of the displacement response waveform. Furthermore, it succeeded in assessment of the natural frequency by the frequency analysis. The health assessment of the structure is possible by using the digital image correlation method and frequency analysis.

Abstract: Since the method of performing displacement measurement and stress assessment of material by non-contact comes to capture the spotlight, study of the digital image correlation method which adopted the pattern-matching method for asking for displacement by deformation of a surface speckle pattern has been advanced. When the configuration for an analysis was settled in the rectangle and the square region, the whole-field mesh generation was also possible, but when it became a complicated configuration, the background etc. entered and mesh generation was affected. In order to solve such a problem, even if the object for an analysis was a complicated configuration, it aimed at generating a mesh automatically and obtaining appropriate analysis output in the displacement analysis and stress analysis using the generated mesh. In addition, the validity of the result was verified by the comparison with the finite element method. By this study, the convenience and availability of the digital image correlation method was improved remarkably, and it became clear to become a leading tool in health monitoring.

Abstract: Most measurement by experiment is about a structure surface and it is dramatically difficult to measure the stress state inside a structure. Although the stress analysis of a big structure is possible by the 3-D finite element method, great time, labor, and expense are needed for modeling and calculation. Then, we developed the 3-D local hybrid method which analyzes only the local model of a structure and can evaluate the stress field inside it from surface data obtained by easy measurement. In previous studies, the good result was obtained with the surface cracked specimen subjected to uniform tension and a cantilever subjected to bending. However, with an actual structure, it is not thought that simple bending deformation which is produced under an experiment environment arises. In this study we examined whether the 3-D local hybrid method would be able to apply to the structure subjected to bending and torsion by using the displacement on front surface and the displacement of upper and lower sides of a local model. It was clarified that the 3-D local hybrid method is very useful to the 3-D stress analysis of the structure subjected to the complicated loading (uniform, bending and torsion, etc.).