Accurate ex situ deformation measurement using an ultra-stable two-dimensional digital image correlation system.
Accurate ex situ deformation measurement using an ultra-stable two-dimensional digital image correlation system.
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DOI：
10.1364/ao.53.004216
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发表时间：
2014-07
期刊：
影响因子：
1.9
通讯作者：
B. Pan;Liping Yu;Dafang Wu
中科院分区：
文献类型：
--
作者：
B. Pan;Liping Yu;Dafang Wu
基于二维数字图像相关(2D-DIC)和固定摄像机的平面形变原位测量已经在许多已发表的著作中得到了充分的研究，并被广泛应用于各种领域。然而，在某些特殊情况下(例如，工程结构的长期变形监测，或承受异常载荷的试件的变形测量)，使用2D-DIC进行原位变形测量是非常困难或不可能的，必须对重新定位的试件进行非原位2D-DIC测量或使用重新定位的相机。为了实现准确的测量，必须识别和最小化非原位2D-DIC测量的误差源，并量化非原位2D-DIC测量的应变精度。在这项工作中，首先详细讨论了非原位2D-DIC测量的潜在误差源。然后，为了减少与这些问题相关的误差，建立了一个结合了主动成像思想和精心设计的双边远心透镜的超稳定2D-DIC系统，该系统不受环境光照的潜在变化以及物体表面和/或图像平面可能出现的微小离面运动的影响。首先将建立的超稳定2D-DIC系统与常规2D-DIC系统进行比较，以确定无应变样品的表面应变。然后，利用打孔技术和建立的2D-DIC系统进行了残余应力的非原位测量，并与实际测量结果进行了比较。研究结果表明，利用该系统进行的非原位2D-DIC变形测量具有较高的精度，可用于实际非原位试验中的精确变形测量。
In situ planar deformation measurement using two-dimensional digital image correlation (2D-DIC) and a fixed camera has been fully investigated in many published works and widely used for various applications. However, in certain special cases (e.g., long-term deformation monitoring of engineering structures, or deformation measurement of a specimen subjected to uncommon loading), it is very difficult or impossible to carry out in situ deformation measurement using 2D-DIC, and necessitates ex situ 2D-DIC measurements for a repositioned specimen or using a relocated camera. To achieve accurate measurements, the error sources of ex situ 2D-DIC measurements should be identified and minimized, and the strain accuracy of ex situ 2D-DIC measurements should be quantified. In this work, the potential error sources of ex situ 2D-DIC measurements are first discussed in detail. Then, to mitigate the errors associated with these issues, an ultra-stable 2D-DIC system combining the idea of active imaging and a well-designed bilateral telecentric lens is established, which is invariant to the potential variations in ambient lighting and the possible small out-of-plane motions in object surface and/or image plane. The established ultra-stable 2D-DIC system is first compared with the regular 2D-DIC setup in determining the surface strains of an unstrained sample. Then, ex situ residual stress measurement using the hole-drilling technique and the established 2D-DIC system was conducted and compared with the applied ones. The results of this work confirm that the accuracy of ex situ 2D-DIC deformation measurements using the proposed system is of high fidelity, and can be used for accurate deformation measurement in practical ex situ tests.