Research On 3D Structure Deformation Based On Binocular Vision

In the automotive,heavy machinery,aerospace industry and other industries,numbers of new composite materials and large complex work pieces are applied,a quick,convenient,and suitable for field method is required for three-dimensional contour shape and deformation strain testing.Traditional three coordinates measuring equipment(such as three coordinate machine,laser tracker,etc.)and the strain test method(such as strain gauge,amplify meter,etc.)are low efficiency,small measuring range,more difficult to achieve three dimensional full size tests.With the development of the digital image correlation method,the accuracy of the machine vision can reach the sub-pixel level,with low cost and operating environment,which can quickly realize the measurement of the full size or strain field.In this paper,3D-DIC combined with the binocular vision technology is studied,measuring 3d displacement field and strain field,to solve the problem of 2D-DIC cannot measure off-surface displacement.Due to the 3D-DIC still exists some shortage,the research content is aimed at improving the measuring accuracy.The research results contend,(1)Lacking of three-dimensional speckle in 3D-DIC,a method to generate 3D speckle images is proposed,which can avoid the interference factors such as calibration error,camera distortion,environments errors.It can be also used to verify the initial value estimation,shape function selection,correlation function,3D reconstruction and the algorithm accuracy of 3D strain calculation.(2)An initial value estimation methods of shape function interpolation and linear interpolation based on SIFT feature matching is proposed,which improves the computation speed and precision.Due to image matching strategy problems in 3d reconstruction,two kinds of stereo matching strategies are analyzed,then sums up its applicability of the scene.(3)In the calculation of three-dimensional strain field,due to the existing algorithm robustness is poorer,apply of the least-square fitting planar differential element fitting method for calculating strain,getting good robustness.(4)Experiments are made for the contents of the above 3 points(full size measurement and deformation measurement),the results showing that the algorithm is correct,effective and reliableThe research achievements in this paper can improve the calculation precision of the 3D-DIC,provide the algorithm of 3D-DIC,and improve the system of algorithm and application scope.