High-Accuracy 2D Digital Image Correlation Measurements with Bilateral Telecentric Lenses: Error Analysis and Experimental Verification
High-Accuracy 2D Digital Image Correlation Measurements with Bilateral Telecentric Lenses: Error Analysis and Experimental Verification
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DOI：
10.1007/s11340-013-9774-x
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发表时间：
2013-06
影响因子：
2.4
通讯作者：
B. Pan;Liping Yu;Dafang Wu
中科院分区：
文献类型：
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作者：
B. Pan;Liping Yu;Dafang Wu
通过比较以不同配置记录的测试平面样本表面的两个数字图像，二维数字图像相关 (2D-DIC) 提供记录图像中亚像素精度的全场位移和全场应变。对于使用光学透镜的2D-DIC系统，通常使用简单的针孔成像模型来描述测量的传感器平面位移与物体表面的实际位移之间的线性关系。然而，在实际测量中，各种不可避免的不利因素，如加载后测试物体表面发生的小幅面外运动、相机自热或温度变化导致传感器目标产生小幅面外运动、成像镜头的几何畸变等，都可能严重损害或轻微改变原来假设的线性对应关系。在某些情况下，这些缺点可能会导致 2D-DIC 测量的位移和应变出现显着误差。在这项工作中，首先详细描述了由于上述三个不利因素而导致的 2D-DIC 测量误差。然后，为了最大限度地减少与这些缺点相关的误差，建立了使用双边远心镜头的高精度 2D-DIC 系统。使用易于实施的静态、面外和面内刚体平移测试，对已建立的 2D-DIC 系统和其他两个使用传统镜头和物方远心镜头的 2D-DIC 系统的性能进行了实验研究。详细的检查表明，高质量的双边远心镜头不仅对测试物体的平面外运动和相机的自热不敏感，而且镜头畸变可以忽略不计。还对铝样品进行了单轴拉伸试验，以定量比较所提出的 2D-DIC 系统和应变片玫瑰花测量的轴向和横向应变。两次测量之间的完美一致性进一步验证了所建立的 2D-DIC 系统的准确性。
By comparing two digital images of a test planar specimen surface recorded in different configurations, two-dimensional digital image correlation (2D-DIC) provides full-field displacements to sub-pixel accuracy and full-field strains in the recorded images. For the 2D-DIC systems using an optical lens, a simple pinhole imaging model is commonly used to describe the linear relationship between the measured sensor plane displacements and the actual displacements in the object surface. However, in a practical measurement, various unavoidable disadvantageous factors, such as small out-of-plane motion of the test object surface occurred after loading, small out-of-plane motion of the sensor target due to the self-heating or temperature variation of a camera, and geometric distortion of the imaging lens, may seriously impair or slightly change the originally assumed linear correspondence. In certain cases, these disadvantages may lead to significant errors in displacements and strains measured by 2D-DIC. In this work, the measurement errors of 2D-DIC due to the above three disadvantageous factors are first described in detail. Then, to minimize the errors associated with these disadvantages, a high-accuracy 2D-DIC system using a bilateral telecentric lens is established. The performance of the established 2D-DIC system and other two 2D-DIC systems using a conventional lens and an object-side telecentric lens are investigated experimentally using easy-to-implement stationary, out-of-plane and in-plane rigid body translation tests. A detailed examination reveals that a high-quality bilateral telecentric lens is not only insensitive to out-of-plane motion of the test object and the self-heating of a camera, but also demonstrates negligible lens distortion. Uniaxial tensile tests of an aluminum specimen were also performed to quantitatively compare the axial and transversal strains measured by the proposed 2D-DIC system and those measured by strain gage rosettes. The perfect agreement between the two measurements further verifies the accuracy of the established 2D-DIC system.