An error elimination method for high-temperature digital image correlation using color speckle and camera

Digital image correlation method is a kind of displacement and strain measurement technique based on visible light illumination. It can realize non-contact and full-field measurement with lower requirements on the measurement environment, thus it's widely used in testing and research for mechanical properties of materials at high temperature. But there are many factors affecting the measurement accuracy due to the complexity of the high temperature environment, of which the influence of the thermal disturbance on digital image correlation method is the most obvious. In order to reduce the influence of it and improve the measurement accuracy, this paper proposes a measurement method for eliminating thermal disturbance error in high temperature deformation measurement based on color speckle and camera. Two kinds of grayscale field information of different colors were endued to the surface of specimen, and we collected images by color camera with channel separation for each frame of them. Then we processed the grayscale field of two channels separately combined with the digital image correlation method, analyzed the information carried by two different grayscale fields, and a simple mathematical model was performed to separate the thermal disturbance error from the measurement results. Finally, we set up the experimental system, built the mathematical model between the two channels through static measurement experiment, which was used to extract and correct the thermal disturbance error of measurement results of the rigid body motion experiment. The high consistency between corrected result and true displacement value proved the feasibility and accuracy of the proposed method.