Study Of In-plane Displacement Measurement Based On Speckle Digital Image Correlation

Digital image correlation method is a new non-contact optical measurement technique based on computer vision. Its basic principal is that using CCD to collect two digital speckle images of original and deformed surface, through computer to open correlation matching algorithm to find displacement and strain of the whole field. The characteristic of the technology determines the field of its application. Compared with other optical measurement techniques, digital image correlation method has many superiority, such as full-field analysis, non-contact measurement, simple path of rays, adjusted field size, unable to deal with interference fringes.The application of this method has been extended from the initial experimental stress analysis to many fields. such as solid mechanics,fluid mechanics,bio-mechanics,wood mechanics, microscale mechanics experiment,electronic packaging,engineering surveying and nondestructive testing. In the field of theory application, as a kind of important method which searches the matching areas in two-dimensional plane, digital image correlation has gotten a great development and progress.In this paper, the two-dimensional digital speckle correlation technology is deeply studied. On the basis of finished the whole pixel matching work, In order to improve the calculation precision and searching efficiency, studied the different methods of sub-pixel, include gray level interpolation method and curved surface fitting and so on. And according to the requirements of the actual measurement, write the sub-pixel displacement localization algorithm. In the related search link, a near field search method is proposed to improve the computational efficiency. On the basis of theoretical research, we set up a two-dimensional digital speckle correlation measurement system. Through the analog to digital speckle image of rigid-body translational experiment, the precision of the measuring system was verified. In practice, we do the cantilever beam bending experiment, using improved measuring device measured on the surface of the aluminum plate deformation information. Using ansys software simulate the model of cantilever bending under5mm. The simulated values and in comparison with the measured value of digital speckle measurement system, we get the calculation precision in the measurement system in the actual measurement.