Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : September 16, 2019 - September 18, 2019
Stiffness of structures for long time operation gradually decreases by stress or strain cyclic loading. Full field strain measurement technique can determine the distribution of decrement of the stiffness or a degree of material damage. Since the error occurs due to several noise source, 0.1% strain becomes a measurement limit. Digital Image Correlation (DIC) has been well studied and employed for such a strain measurement, however DIC needs random dot pattern, complete uniform lighting and computation time for wide view. Accordingly, the authors have employed Dot Centroid Tracking (DCT) at high speed and with high accuracy. DCT can be measured with minimal image processing and centroid location computation. The objective of this study is a determination of a dot mark size and the distance to keep accuracy of the measurement at 0.01% strain. An object with four dots is illuminated with light and photographed with a digital camera to obtain an average value. Based on the average value of the coordinates of 4 points obtained, Bayesian estimation is performed with a small number of sheets, and the average and variance are determined and expressed as a probability density function. We determine the dot size at which 0.01% strain can be measured by changing the dot radius and the distance between centroid.
