Fast Algorithms On Digital Image Correlation For Full-field Measurement And Its Applications

Digital Image Correlation(DIC) is one of the optical measurement methods whichbases on digital speckle images and numerical analysis. DIC has the advantages of theoptical measurement methods, such as non-contact and full-field measurement, comparedwith the electrical measurement methods. Furthermore the arrangement of DIC’s measuredevice is more simple than the other optical methods and has less stringent requirementsof light and environment. So DIC is widely used in science research and engineering inrecent years. With the real-time applications of DIC, it is found that there is still a need tofurther improve its measurement precision, computing speed, and avoid the measurementerror. This thesis mainly focus on how to further improve the calculation speed of DIC,then based on which develops the DIC software to better meet its applications of scienceresearch and engineering measurement.First this thesis studies the basic parameters of DIC, as calculation window, specklesize, fitting window, and obtain the best size of them, which lays a foundation of thesubsequent research. Through the deep analysis of the correlation coefficient calculationformula, zero-normalized cross-correlation coefficient formula, and combined with themathematics, an improved method is developed to calculate the correlation coefficients.This improved method could effectively avoid the repetitive operation of the traditionalmethod, so it makes the computing speed of DIC nearly doubled. With the introduction ofthe three step search, one of the motion estimation fast algorithms in the video image, thecomputation speed of DIC is further improved. Therefore, combined with the principal ofthe motion estimation fast algorithm, a fast algorithm for DIC is developed, which muchmore further increases the calculate speed.On the basis of theoretical analysis, this thesis also introduces the DIC measuresoftware with friendly user interface, and it is successfully applied in the tensileexperiment and three point bending test, thus to some extent showes the superiority of theDIC.