Pseudo Spackle Pattern Photography Algorithm Development and Experimental Calibration

摘要

The measurement of in-plane surface strain is very important in structural material research. The traditional strain measurement techniques, however, have their clear constraint and inconveniency in terms of both sensor system arrangement and data analysis. This paper presents the development of a novel technique for estimating the local surface strain over a region. The key element of the technique is a high accurate image displacement detection algorithm. This algorithm is based on the Optical Flow concept and implemented in a multi-scale analysis scheme. This technique is aiming at covering large viewing area and detecting small deformation components on the top of large translation with high accuracy. A numerical differentiation procedure is also discussed to derive strain field from the displacement field. The test procedure of this technique is also presented in this paper. The test procedure consists of absolute translation calibration and strain calibration against strain-gauge measurement. The experimental results show a very good agreement between the proposed technique and the well-established traditional measurement.