数字体图像相关方法中的残余灰度场计算研究  

Study on Gray Level Residual Field Calculation in Digital Volume Correlation

作　　者：潘兵[1] 张轩豪 王龙[2] Pan Bing;Zhang Xuanhao;Wang Long(National Key Laboratory of Strength and Structural Integrity,School of Aeronautic Science and Engineering,Beihang University,Beijing 100191,China;Science and Technology on Reliability and Environmental Engineering Laboratory,Beijing Institute of Structure and Environment Engineering,Beijing 100076,China)

机构地区：[1]北京航空航天大学航空科学与工程学院强度与结构完整性全国重点实验室,北京100191 [2]北京强度环境研究所可靠性与环境工程技术重点实验室,北京100076

出　　处：《光学学报》2024年第3期66-75,共10页Acta Optica Sinica

基　　金：国家自然科学基金(11925202)。

摘　　要：残余灰度场是变形前后数字体图像中对应体素点的灰度之差。在基于有限单元的全局数字体图像相关(DVC)方法中,残余灰度场作为计算区域各体素点匹配质量的目标函数,可直接计算获得,并可用于材料内部损伤演化或裂纹扩展的精细表征。然而,当前广泛使用的基于图像子体块的局部DVC只能获得计算区域内各离散计算点的位移、应变和相关系数信息,无法直接计算区域内各体素点的残余灰度。相较于相关系数和变形信息,残余灰度场可实现逐体素的匹配质量评价,在内部损伤或裂纹扩展的可视化观测和准确定位方面具有显著优势。为能在局部DVC中获得残余灰度场信息,提出一种简单有效的残余灰度场计算方法。该方法基于三维Delaunay四面体剖分算法,并利用有限元框架对局部DVC离散计算结果进行稠密插值,以获取逐体素连续位移场,并将其用于变形体图像校正。模拟和真实实验结果表明,基于局部DVC测量结果后处理计算获得的残余灰度场不仅可以实现精准的损伤定位,还能观测到裂纹形貌以及界面脱黏行为。所提方法弥补了当前局部DVC在精细化匹配质量评价方面的不足,有望拓展该方法在材料和结构内部损伤观测和定位中的应用。Objective Gray level residual(GLR)field refers to the intensity differences between corresponding voxel points in the digital volume images acquired before and after deformation.Typically,internal damage in materials induces substantial variations in grayscale values between corresponding voxel points.Therefore,the GLR field helps to reveal the damage location.In the finite element-based global digital volume correlation(DVC)method,the GLR field,as the matching quality evaluation criteria,can be readily calculated and has been employed to characterize the evolution of internal cracks.However,the widely used subvolume-based local DVC,which can output displacement,strain,and correlation coefficient at discrete calculation points,cannot obtain the GLR directly.Compared with correlation coefficient and deformation information,the GLR field achieves voxelwise matching quality evaluation,thus demonstrating superior performance in visualizing internal damage.Therefore,accurate GLR calculation in local DVC is undoubtedly valuable in compensating for its shortcomings in finematching quality evaluation and expanding its applications in internal damage observation and localization.Methods The GLR field is obtained by subtracting the reference volume image from the deformed volume image after full-field correction.The key of its calculation is to utilize the continuous voxelwise data,including contrast and brightness correction coefficients and displacement,to correct the deformed volume image.In this work,a dense interpolation algorithm based on finite element mesh is adopted to estimate the voxelwise data within the volume of interest(VOI).3D Delaunay triangulation algorithm is first utilized to generate tetrahedron element mesh from the discrete calculation points,and then the data of voxel points inside each tetrahedron element can be determined with the shape function of finite element.After acquiring the voxel-wise data of VOI within the reference volume image,the corrected deformed volume image can be reconstructed.Gi

关 键 词：三维图像处理 数字体图像相关方法 残余灰度场 内部损伤观测与定位 

分 类 号：O348.1[理学—固体力学]