Research On Key Technologies Of Digital Image Correlation Methods In Special Application Scenarios

DIC technology is essentially an image processing technology,which has non-contact and full field measurement ability.In addition,DIC also has some unique characteristics,such as simple experimental device,low price,easy implementation,wide application range,adjustable spatial and temporal resolution,and robustness to environmental vibration and environmental light changes.These outstanding advantages has made DIC technology popularized rapidly in the past 40 years,and various commercial DIC systems have been launched.DIC technology has surpassed the competitors such as interferometric optical technology,electronic speckle pattern interferometry and moire interferometry,and has established a dominant position in the field of experimental mechanics.DIC technology has also been widely used in material science,biomechanics,civil engineering,electronic printing,mechanical manufacturing,geotechnical engineering and aerospace engineering.Although DIC technology has become mature in both theoretical research and engineering application,there are still some challenges that cannot be overcome by traditional DIC technology.First,as the Poisson's ratio of the measured object is often not 0,the object will move out of the plane when the object is stretched or compressed,resulting in the systematic error of the measurement results.Second,the large deformation of the object itself will lead to the decrease of the correlation between the reference sub-region and the deformation sub-region,so that there is no obvious peak in the correlation map and the matching position can not be obtained,which is the so-called decorrelation phenomenon.Furthermore,not only the large deformation of the object will lead to decorrelation,some objects without large deformation but their photo have large deformation also can lead to decorrelation.For example,the global rotation(such as wind turbine blades)and global translation(such as opening and closing of flytrap)of an object can also lead to decorrelation.In view of the above challenges of DIC technology in the above application scenarios,the main research work of this paper is as follows:(1)In order to solve the problem of systematic error caused by out-of-plane motion and non-perpendicular alignment in the measurement of large deformation objects,a more perfect integrated error model is proposed in the second chapter.Based on this error model,we only need to measure the out-of-plane motion(including out-of-plane translation and rotation)and non-perpendicular alignment angle to calculate and compensate the pseudo strains.This paper also proposes a cross-shaped structured light method to reconstruct the spatial position of the plane to be measured in real time,and then the values of each error source can be obtained.In order to avoid the mutual influence between structured light stripe and speckle image,this paper also proposes to capture speckle image and structured light stripe with different channels of color camera.(2)In order to overcome the decorrelation of DIC when large inter-frame rotation deformation occurs,in chapter three,the rotation invariant DIC(RIDIC)algorithm based on ring projection transform feature and orientation code feature is proposed.In order to further improve the speed of RIDIC algorithm,this paper proposes a more efficient local ring pattern feature and wavelet pyramid hierarchical search method,and finally obtains the fast-RIDIC algorithm.(3)In order to overcome the decorrelation of DIC when large inter-frame scaling deformation occurs,a new idea of DIC matching using color information is proposed in the fourth chapter.Due to the scale-and rotation-invariance of color histogram features,a scale-and rotation-invariant DIC(SRIDIC)algorithm based on color histogram features is proposed.To make full use of color information,the correlation function in sub-pixel matching is improved,and the new correlation function is more robust to the change of light intensity and position.