撮影画像を用いたひずみ分布計測法に関する研究

—ひずみ計測精度に及ぼす被測定物の面外変位の影響とその補正—

抄録

In order to inspect the strength and reliability of structures, measurement using a strain gauge is widely adopted. However the measurement of real structures using a strain gauge requires dangerous preparatory work such as fixing strain gauges onto the structure and connecting them via cables to strain meters located in a remote place. Moreover, strain gauges detect strain only at the points where they are attached. Therefore there is a growing demand for a more reliable and accurate strain distribution measurement of structures. The purpose of this study is to develop a strain distribution measurement system based on the sub-pixel digital image correlation (Sub-DIC) method. However, the Sub-DIC method has several problems concerning accuracy; an out-of-plane deformation of structures has an adverse effect on the measurement accuracy. In this study, the effect of the out-of-plane deformation is taken into account. We formulate a model of the out-of-plane deformation, and discuss the effect of the theoretical equation given on the strain measurement accuracy. Furthermore, we show the effectiveness of the theory by a model experiment. Moreover, a compensation method for the out-of-plane deformation is proposed. It is found that the Sub-DIC method with the proposed compensation system is superior to existing strain distribution measurement systems, on the basis of a series of experimental examinations using the four-point bending test.