Research On The Key Technology Of Digital Image Correlation

The digital image correlation method is a non-contact optical measurement method developed in the 1980 s.In recent years,researchers from various countries have made different degrees of research progress in its calculation speed,measurement accuracy,and measurement environment.However,no matter whether it is two-dimensional or three-dimensional digital image correlation method,there are certain problems.When the deformation field is measured in two-dimensional,the accuracy of the measurement result will be lower due to the influence of the algorithm itself and the surrounding environmental factors.Decrease in efficiency: In three-dimensional,due to its short development time,its theoretical research is not very complete,and compared with two-dimensional,adding a dimension,its calculation amount increases sharply,which will affect the calculation efficiency of measurement results.Therefore,this article will conduct in-depth research on the computational efficiency and measurement accuracy of digital image correlation methods(2D and 3D).The research content is as follows:(1)In terms of the two-dimensional digital image correlation method,this paper firstly analyzes and studies key technologies such as correlation function,deformation initial value estimation,and sub-pixel search algorithm,and then proposes an initial value estimation based on the beetle algorithm.Quickly find the integer pixel displacement,improve the calculation efficiency,and provide accurate initial displacement values for the next sub-pixel search algorithm.(2)In the three-dimensional digital image correlation method,when measuring the three-dimensional deformation field inside the object,in the two search stages of holistic and sub-voxel,it is necessary to use the correlation function to evaluate the similarity of the gray distribution of the sub-volumes before and after the deformation.When calculating the similarity of the gray distribution of the sub-volume blocks,the correlation function of is unable to distinguish the sub-volume blocks in different positions,which is not consistent with the actual situation.Therefore,this paper introduces the weight function into the correlation function,and proposes a three-dimensional digital image correlation algorithm with a weight factor correlation function.This method can distinguish the sub-volumes at different positions,and then obtain the displacement field before and after deformation.(3)On the basis of the above-mentioned improved theory,a digital speckle comparison experiment was carried out between the beetle algorithm proposed in the two-dimensional digital image correlation method and other algorithms of the same type.The results show that compared with other algorithms,the algorithm proposed in this paper can quickly and accurately find the entire pixel displacement.The digital image correlation method is used to obtain the strain field of the concrete specimen under uniaxial compression test and analyze the crack initiation,propagation and failure modes of the specimen under uniaxial compression.Two-dimensional digital image correlation method is used to measure the displacement field of concrete specimens under vibration environment and various light intensities.The results show that these factors will affect the measurement accuracy of digital image correlation method.This article proposes to reduce these influencing factors.The solution ideas.For the proposed new three-dimensional digital image correlation method,a computer controllable speckle experiment was carried out on a computer,and good measurement results were obtained.