Method to eliminate thermal disturbance errors in digital image correlation measurement based on projection speckle.

Abstract

Digital image correlation (DIC) technology is an optical measurement method of material strain displacement based on visible light illumination. With the increasing application of DIC technology in the field of high-temperature measurement, however, the effect of thermal disturbance on measurement accuracy becomes more and more serious. To solve this problem, a method to eliminate thermal disturbance in material measurements based on projection speckle is proposed. First, the gray surface information of two different colors is assigned to the surface of the test piece by artificial splashing and projector projection. The pictures are collected using a color camera, and the channels are separated for each frame of the picture. After that, the displacement field recorded by different channels can be obtained by DIC calculation so the thermal disturbance error can be separated from the real displacement and eliminated. Subsequently, an experimental system is built. Finally, the corrected results are compared with the true displacement value of the stage. The results show that the two sets of values are highly consistent, which verifies the feasibility and accuracy of the proposed method.