Monocular Vision Digital Image Correlation System And The Application In Large Deformation Measurement

It is the basis of studying the properties of material materials to realize the measurement of large deformation strain field and to perfect the description of large deformation.In recent years,more and more strain measurement methods have been developed.It is important to find a measurement method with good universality and high precision.First of all,we introduce the common strain measurement methods such as optical measurement and electric measurement,and compare their working principle and application in different fields.Determined the great advantages of digital image correlation methods in large deformation strain measurement.Combined with the computer vision system,we can accurately describe the 3D morphology and deformation characteristics of the surface of the object.This paper elaborates the key techniques of digital image correlation method from three aspects: camera calibration,feature extraction and matching,3D reconstruction.For the camera calibration technique,we introduced the linear pinhole imaging model firstly,then compared the self-calibration method,active visual calibration method and traditional camera calibration method.For feature extraction and matching techniques of image information,we mainly introduced SIFR and SURF feature matching methods.Finally,we briefly introduced the 3D reconstruction of binocular stereoscopic vision,and described the 3D reconstruction process of monocular stereo vision in detail.Based on the principle and technology of digital image correlation method,this paper designed and constructed a set of large deformation measuring device of monocular vision digital image.We described the overall design index in detail include the working mechanism and design purpose of each module.Then we obtained the displacement field of rubber in large deformation experiment by using the existing material testing machine.Combined with experimental data,we analyzed the tensile and rotational deformation of the line element under the deformation state.We obtained the strain and curvature of rubber specimens under large deformation.Finally we improved the measurements of large deformation.