Research On Measurement Techniques Based On Digital Speckle Correlation Method

With the continuous development of materials technology, a variety of new materialscontinue to emerge, so that the application of the relevant scientific fields has also beenwidespread concerned. Measuring the mechanical properties of material providesimportant data basis for materials technology’s development. Compared with thetraditional measuring method, digital speckle correlation method has advantages ofnon-contact, full field, high precision and low requirements in experiment environment.In this dissertation, in order to improve the accuracy and efficiency of digital specklecorrelation method, the key technologies of digital speckle correlation method aretheoretical and experimental studied.The primary coverage of this thesis is as following:(1)After analyzing the object deformation’s mathematical model and correlationfunction, the experiment using computer simulation speckle pattern to comparebasically correlation search methods shows that particle swarm algorithm has moreapplicable range for searching integer pixel than climbing algorithm andNewton-Raphson method of partial differential correction has higher precision thangray-gradient algorithm for searching sub-pixels.(2)Adaptive decision inertia weight PSO correlation searching algorithm is proposedin this dissertation. And its advantage that it can be smarter to determine whether to endthe iteration makes this method can be more efficient to get accurate results.(3)After theoretical derivation of the camera projection model, this dissertation usescamera calibration using2D planar target proposed by Zhang et al. to solve the cameradistortion and transformation between pixel space and physical space. Simultaneously,camera calibration experiment is done to verify this method.(4)In this dissertation, digital speckle correlation software is designed based on VisualStudio2010and experiment system is developed to do actual measuring experiments,which include rigid body displacement, comparative experiment with extensometer andstrain concentration in specimen during the specimen being extruded. The results ofexperiments show the measurement system can achieve measurement functions.