Digital Image Correlation for Shape and Deformation Measurements
The essential concepts underlying the use of two-dimensional (2-D) digital image correlation for deformation measurements and three-dimensional (3-D) digital image correlation for shape and deformation measurements on curved or planar specimens are presen
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Digital Image 20. Digital Image Correlation for Shape and Deformation Measurements
Michael A. Sutton
response in a heterogeneous weld zone. Sections 20.11 and 20.12 present applications using 3-D image correlation to quantify material response during quasistatic and dynamic tension–torsion loading, respectively, of an edge-cracked specimen. Section 20.13 presents closing remarks regarding the developments.
20.1 Background ......................................... 566 20.1.1 Two-Dimensional Digital Image Correlation (2-D DIC) ................... 567 20.1.2 Three-Dimensional Digital Image Correlation (3-D DIC) ................... 568 20.2 Essential Concepts in Digital Image Correlation .................. 568 20.3 Pinhole Projection Imaging Model ......... 20.3.1 Image Distortion ........................ 20.3.2 Camera Calibration for Pinhole Model Parameter Estimation........ 20.3.3 Image-Based Objective Function for Camera Calibration ................
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20.4 Image Digitization ................................ 573 20.4.1 Discussion ................................. 573 20.5 Intensity Interpolation.......................... 573 20.5.1 Discussion ................................. 575 20.6 Subset-Based Image Displacements ....... 575 20.6.1 Discussion ................................. 577 20.7 Pattern Development and Application .... 577 20.7.1 Discussion ................................. 579 20.8 Two-Dimensional Image Correlation (2-D DIC) .............................................. 20.8.1 2-D Camera Calibration with Image-Based Optimization .. 20.8.2 Object Displacement and Strain Measurements ........... 20.8.3 Discussion .................................
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Part C 20
The essential concepts underlying the use of two-dimensional (2-D) digital image correlation for deformation measurements and threedimensional (3-D) digital image correlation for shape and deformation measurements on curved or planar specimens are presented. Twodimensional digital image correlation measures full-field surface displacements with accuracy on the order of ±0.01 pixels on nominally planar specimens undergoing arbitrary in-plane rotations and/or deformations. Three-dimensional digital image correlation measures the complete 3-D surface displacement field on curved or planar specimens, with accuracy on the order of ±0.01 pixels for the in-plane components and Z/50 000 in the out-of-plane component, where Z is the distance from the object to the camera, for typical stereo-camera arrangements. Accurate surface strains can be extracted from the measured displacement data for specimens ranging in size from many meters to microns and under a wide range of mechanical loading and environmental conditions, using a wide range of imaging systems including optical, scanning electron microscopy, and atomic force microscopy. In Sect. 20.2, the essential concepts underlying both 2-D DIC and 3-D DIC are presented. Section 20.3 introduces the pinhole imaging model and calibration procedures. Sections 20.4 and 20.5 describ
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