Research On Concrete Ct Image Information Extraction Method Based On Aggregate Shape Matching

Concrete CT image contains important information about the internal damage development process of concrete.How to find cracks in CT images as early as possible is the key research content.The observation and regularity on the mesa-crack evolution proces.s can help to reveal the meso-damage mechanism of concrete,quantitatively evaluate the damage value,and explore the cause of the macro-mechanical properties of concrete and provide a basis for further establishing an objective macro-constitutive relationship.The research in this paper can be summarized as the following aspects:(1)The procedure on concrete CT test using medical CT and homemade matching loading device is introduced.The existing problem is that it is very difficult to obtain the whole process CT images including crack initiation,extension and penetration.Because the scanning chance is difficult to grasp and CT resolution is limited,the easy to implement is to find the cracks which not easily found by conventional methods in the existing massive CT images of concrete.(2)The gray image method is more intuitive,but it cannot quantitatively analyze the evolution process of cracks in the image.The contour method and the equal-density image segmentation method can distinguish the aggregate,mortar and crack in the CT image clearly,but it is more difficult to determine the CT number threshold given by the CT image on above two methods.Using the method of differcential image,the crack display is more clear,but it is greatly affected by the movement,deformation and scanning positioning error at the test process.The method of gradient image can enhance the edge information of the image,but the crack information in the image is easily interfered by the aggregate and cavity edge information.(3)The Digital Speckle Correlation Method(DSCM)obtains the displacement field and strain field of the internal deformation process of the concrete specimen according to the correlation analysis of the mean and variance of the CT number in the sub-area,and the crack strain field of the internal deformation process of the concrete specimen according to the correlation analysis of the mean and variance of the CT number in the sub-area,and the crack according to the strain localization zone can be predicted.This method has advanced concepts.However,due to too many pixel points in the sub-area,the accuracy of displacement field and strain field reduced much.(4)An algorithm for Aggregate Shape Matching Method(ASMM)on concrete is proposed to solve the strain field.In the CT image,the image of the aggregate region is brighter,relatively easy to segment,and the aggregate geometric shape is easy to identify and match.The displacement field is calculated according to the displacement of the aggregate,and then strain field is obtained.The strain localization zone is used to predict the location and shape of future cracks,that is,the crack evolution process is reflected by the uneven variation of the strain field,which is a substantial improvement of the speckle method,and the accuracy of the strain field is obviously improved.The innovation of this paper is to propose a new idea on concrete aggregate shape-matching algorithm to solve the internal displacement field and strain field on concrete.It provides a new way to study the quantitative description of the mesoscopic damage on concrete and the process of strain field localization.