Research And Application Of In-plane Displacement Measurement Based On Digital Image Correlation Method

Digital image correlation method(DCIM)is a combination of traditional optical measurement technology and modern digital image processing technology.Compared with other measurement methods,digital image correlation method has outstanding advantages,because of the light path of this method is simple,non-contact,high precision,has been in the material testing,civil engineering,machinery manufacturing and other traditional areas,and even aerospace,nanoscience,Biomechanics and other sophisticated areas have been widely used,is the most active modern experimental mechanics,the most important and most widely used one of the optical measurement method.The digital image correlation method is to calculate the displacement field or strain field of the object by searching and matching the speckle image before and after the deformation of the object surface.Digital image correlation method of the eight key issues namely: 1,the correlation coefficient formula;2,the whole pixel search method;3,the sub-pixel search algorithm;4,speckle image;5,noise reduction technology;6,compensation technology;7,transition between displacement field and strain field;8,measurement of three-dimensional strain field.At present,the research of digital image correlation method mainly focuses on two aspects: 1,computational efficiency;2,measurement accuracy.Based on the discussion and improvement of these two problems,this paper deeply studies the basic principle,correlation coefficient,whole pixel search method and subpixel search algorithm of digital image correlation method in in-plane displacement measurement.On the basis of the completion of the whole search matching work,the selection of the correlation coefficient and the process of the sub-pixel search calculation are also improved,and the related operation software is verified.In terms of computational efficiency,this paper first analyzes the six correlation coefficient functions which are common in the matching search process,and compares the computing performance of each aspect and puts forward somesuggestions to improve the speed of calculation.time.Then,several common pixel search algorithms are introduced.Through theoretical analysis and simulation,it is proved that the three step search method has better matching effect,faster computation and easier programming.In terms of measurement accuracy,combined with gray interpolation method and fitting the legal properties and advantages of these two algorithms,this paper proposes a new improved Sub-pixel Search algorithm combined with interpolation algorithm,and its accuracy in the sub-pixel displacement measurement and search on the anti noise ability is verified.Finally,based on the MATLAB software to write the digital image correlation calculation program,and through the cantilever beam bending test and rigid body translation test to verify the proposed proposed interpolation interpolation algorithm and DICM calculation software in the practical application of the feasibility and accuracy of the experiment The results of a higher degree of credibility.