Crack displacement field measurement is one of the challenges in the application of digital image correlation(DIC)methods.The reliable subset DIC method combines the advantages of SIFT feature matching and DIC method.Subsets(reliable subsets)in the DIC method here are selected by SIFT feature matching.The correlation operations of these subsets are not easily affected by cracks.In this method,the deformation parameters of points of interest(POIs)are obtained by fitting displacements of the center points of reliable subsets around them.The displacement field near the crack has discontinuity,which can lead to significant errors in displacement measurements of POIs near the crack by use of a continuous fitting function.A method of classifying reliable subset center points within fitting regions is used to reduce the errors.Firstly,displacement variation coefficients were used to determine whether there were cracks in fitting regions before classifying.Then,reliable subset center points in fitting regions with cracks were classified by the displacement extremum comparison method.Finally,deformation parameters of POIs were obtained by fitting a suitable type of data points.The effectiveness of the RS-DIC method was verified by a simulation speckle pattern experiments of mode Ⅰ crack and a uniaxial compression experiment of similar material.The results indicate that the RS-DIC method has high accuracy and reliability for crack displacement field measurement.
关键词
数字图像相关方法/裂纹/位移场测量/可靠子区/数据分类
Key words
digital image correlation method/crack/displacement field measurement/reliable subset/data classification
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