光学学报, 2020, 40 (11): 1112001, 网络出版: 2020-06-10
一种针对裂尖变形场测量的正则化全局DIC方法 下载: 969次
Regularized Global Digital Image Correlation Method for Crack Tip Deformation Field Measurement
测量 数字图像相关 裂纹尖端变形场 正则化 measurement digital image correlation crack tip deformation field regularization
摘要
裂纹尖端变形场测量是定量研究材料断裂特性和行为的关键。基于子区的局部数字图像相关(Digital Image Correlation,DIC)目前应用较多,但跨裂纹子区计算出的数据并无意义,且在测量复杂裂纹变形场时会面临欠匹配的问题。为了克服这些缺点,提出一种基于Hermite单元的正则化全局DIC(HRGDIC)方法。该方法采用高阶Hermite形函数构建全局DIC的有限元单元,建立同时考虑灰度误差与位移场光顺性的迭代方法。同时,在每次迭代求解的过程中使用广义交叉验证(GCV)方法来求解最优正则化参数。于是,HRGDIC方法不仅能处理尖端复杂高梯度变形,还可在迭代结束时获得平滑的位移场和应变场。从裂纹尖端变形图像的模拟和真实测量结果可知,与传统的局部DIC方法相比,所提方法测量精度更高,是解决裂纹尖端变形场测量的有效方法。
Abstract
Crack tip deformation field measurements are crucial for the quantitative study of material fracture characteristics and behavior. Subset-based digital image correlation (DIC) is commonly used for this purpose; however, results obtained across the crack are meaningless and are faced with under-match problems in measuring complex deformation fields around the crack. To solve these problems, we propose the Hermite-element based regularized global DIC (HRGDIC) method for deformation field measurements around the crack. HRGDIC uses the high order Hermite element function to construct each finite element in global DIC, and it establishes an iteration method that simultaneously considers the gray-scale error and the displacement field smoothness. During each iteration, the generalized cross-validation method is used to obtain the optimum regularization parameter. Therefore, the proposed HRGDIC method can not only handle the complex high-gradient deformation around the crack tips but also produce smoothed displacement and strain fields at the end of the iterations. Simulations and experimental results of crack tip deformation images show that compared with the traditional local DIC, the proposed HRGDIC has higher measurement accuracy, and it is an effective method for solving the high-gradient deformation field measurement problems around crack tips.
杜鉴昕, 赵加清, 王海涛, 孙立斌, 吴莘馨. 一种针对裂尖变形场测量的正则化全局DIC方法[J]. 光学学报, 2020, 40(11): 1112001. Jianxin Du, Jiaqing Zhao, Haitao Wang, Libin Sun, Xinxin Wu. Regularized Global Digital Image Correlation Method for Crack Tip Deformation Field Measurement[J]. Acta Optica Sinica, 2020, 40(11): 1112001.