Deformation measurements by digital image correlation: Implementation of a second-order displacement gradient
Deformation measurements by digital image correlation: Implementation of a second-order displacement gradient
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DOI：
10.1007/bf02326485
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发表时间：
2000-12-01
影响因子：
2.4
通讯作者：
Cary, PD
中科院分区：
文献类型：
--
作者：
Lu, H;Cary, PD
本文概述了通过实现位移梯度的二阶近似来改进数字图像相关（DIC）方法的过程。二阶近似使得DIC方法可以直接测量非线性变形引起的一阶和二阶位移梯度。通过优化相关系数确定了13个未知参数，包括位移分量、一阶和二阶位移梯度以及灰度值偏移量。先前的DIC方法假设像素子集中的局部变形由位移梯度项的一阶泰勒级数近似表示，因此由高阶位移梯度组成的实际变形往往会扭曲无穷小应变测量值。通过改进测量一阶和二阶位移梯度的方法，可以在存在二阶变形的大变形情况下实现更精确的应变测量。在大多数情况下，新的改进允许DIC方法在一阶位移梯度上保持+/-0.0002的精度，在二阶位移梯度上达到每像素+/-0.0002的精度。
This paper outlines the procedure for refining the digital image correlation (DIC) method by implementing a second-order approximation of the displacement gradients. The second-order approximation allows the DIC method to directly measure both the first- and second-order displacement gradients resulting from nonlinear deformation. Thirteen unknown parameters, consisting of the components of displacement, the first- and second-order displacement gradients and the gray-scale value offset, are determined through optimization of a correlation coefficient. The previous DIC method assumes that the local deformation in a subset of pixels is represented by a first-order Taylor series approximation for the displacement gradient terms, so actual deformations consisting of higher order displacement gradients tend to distort the infinitesimal strain measurements. By refining the method to measure both the first- and second-order displacement gradients, more accurate strain measurements can be achieved in large-deformation situations where second-order deformations are also present. In most cases, the new refinements allow the DIC method to maintain an accuracy of +/-0.0002 for the first-order displacement gradients and to reach +/-0.0002 per pixel for the second-order displacement gradients.