Strain accuracy enhancement of stereo digital image correlation for objects deformation with large rotations

2021 ◽  
Author(s):  
Rong Wu ◽  
Shili Zhao ◽  
Yi Liu ◽  
Shuiqiang Zhang
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Least Square ◽  
Image Correlation ◽  
Displacement Fields ◽  
Full Field ◽  
Rotation Matrices ◽  
Large Rotations ◽  
Value Decomposition ◽  
Stereo Digital Image Correlation

Abstract We propose a full-field stereo digital image correlation (DIC) strain measurement method in order to overcome the poor accuracy while measuring the deformation under large rotations. Such drawback comes from the missing of considering rotation movements of the deformed objects when calculating their strain values. To address that, we first used a DIC matching algorithm combined with rotated subset and feature point detection to obtain displacement fields. By employing a singular value decomposition (SVD) method, we then can calculate rotation matrices of the strain windows before and after deformations. Finally, in order to eliminate the strain errors caused by rotation, we introduced the rotation matrices into the classical pointwise least square (PLS) DIC strain calculation method. Both numerical simulations and experiments are performed, and the accuracy and effectiveness of the proposed method are confirmed by the experimental results.

scholarly journals Identification of a macroscopic anisotropic damage model using digital image correlation and the equilibrium gap method

2010 ◽  
pp. 229-240
Author(s):  
Laurent Crouzeix ◽  
Jean-Noël Périé ◽  
Francis Collombet ◽  
Bernard Douchin
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Damage Model ◽  
Field Measurements ◽  
Image Correlation ◽  
Anisotropic Damage ◽  
Biaxial Test ◽  
Displacement Fields ◽  
Full Field ◽  
Constitutive Parameters

The aim of the work is to demonstrate how an anisotropic damage model may be identified from full field measurements retrieved during a heterogeneous test. The example of a biaxial test performed on a 3D C / C composite is used. In a first step, the displacement fields measured by classical Digital Image Correlation are used as input data of a finite difference version of the Equilibrium Gap Method. A benefit from unloadings (assumed to be elastic) is shown to retrieve a damage law. In a second step, inelastic strains can be assessed from the total measured strain and the elastic estimated strains. The constitutive parameters relative to the inelastic part of the model are then identified.

scholarly journals Scheimpflug Camera-Based Stereo-Digital Image Correlation for Full-Field 3D Deformation Measurement

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Cong Sun ◽  
Haibo Liu ◽  
Yang Shang ◽  
Shengyi Chen ◽  
Qifeng Yu
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Rigid Motion ◽  
Deformation Measurement ◽  
Image Correlation ◽  
Depth Of Field ◽  
Full Field ◽  
Scheimpflug Camera ◽  
3D Deformation ◽  
Stereo Digital Image Correlation

To further extend the scope of stereo-digital image correlation (stereo-DIC) to more challenging environments, a novel Scheimpflug camera-based stereo-DIC is developed for full-field 3D deformation measurement, wherein the Scheimpflug condition, consisting of tilting the sensor plane with respect to the lens plane for the sake of larger depth of field (DOF) of the camera, is employed. The geometric imaging model of the Scheimpflug camera is described, on the basis of which a robust and effective stepwise calibration strategy is performed to calculate the intrinsic and extrinsic parameters of the stereo Scheimpflug rig. With the aid of a specially tailored stereo triangulation method and well-developed subset-based DIC algorithms, the three-dimensional shape and displacement of the specimen can be retrieved. Finally, practical experiments, including rigid motion tests and three-point bending tests, demonstrate the effectiveness and accuracy of the proposed approach.

Experimental Study on Flow-Induced Full-Field Vibration of a Flexible Splitter Plate Behind a Cylinder Using Stereo-Digital Image Correlation

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Ruili Xie ◽  
Liping Yu ◽  
Weidong Zhu ◽  
Bing Pan
Keyword(s):  
Wind Tunnel ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Plane Deformation ◽  
Splitter Plate ◽  
Image Correlation ◽  
Full Field ◽  
Out Of Plane ◽  
Stereo Digital Image Correlation ◽  
Deformation Measurements

Abstract The flow-induced vibration of a flexible splitter plate behind a circular cylinder is investigated experimentally in this study. Unlike previous studies that mainly devoted to flow dynamics, the full-field three-dimensional (3D) dynamic deformation of a splitter plate behind a cylinder in the wind tunnel is measured with an easy-to-implement, compact but practical single-camera high-speed (SCHS) stereo-digital image correlation (DIC) system. The system parameters of the wind tunnel, the configuration of the SCHS-DIC system, and the measurement principles are introduced first. Then, the effectiveness, accuracy, and stability of the SCHS stereo-DIC system are verified by the deformation measurements of the high-stiffness fixed cylinder. Finally, the full-field dynamic 3D deformation measurements of different splitter plates are carried out under different wind speeds. Results of the polyvinyl chloride (PVC) splitter plate show that the out-of-plane deformation is much larger than in-plane deformation. The maximum deformation occurs at the tip region of the plate, the position of which can move non-periodically along the free-end edge. The full-field deformation of the plate presents the characteristics of complex vortex distribution with high and low fluctuations, and exhibits an asymmetric and non-periodic oscillation in the out-of-plane direction. The comparison results reveal how the wind load and material type of the plate affect the oscillation characteristics.

scholarly journals A Simple and Practical Single-Camera Stereo-Digital Image Correlation Using a Color Camera and X-Cube Prism

Sensors ◽  
2019 ◽  
Vol 19 (21) ◽  
pp. 4726 ◽  
Author(s):  
Bo Dong ◽  
Fancang Zeng ◽  
Bing Pan
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
Image Correlation ◽  
Single Camera ◽  
Full Field ◽  
3D Shape ◽  
Stereo Digital Image Correlation ◽  
Deformation Measurements ◽  
Dic Technique

A simple and practical full-frame single-camera stereo-digital image correlation (stereo-DIC) technique for three-dimensional (3D) shape, displacement, and deformation measurements is proposed. The technique uses a compact X-cube prism-based color separation device and a color camera to capture images of blue and red colors from different optical paths, and then extracts the surface 3D shape and deformation information of a test sample by processing the captured two sub-channel color images using regular stereo-DIC algorithm. Compared with the existing full-frame single-camera stereo-DICs, the proposed one eliminates the need for a beam splitter and two bandpass filters to capture images, and offers more simple, compact, and easy-to-use optical arrangement. This novel single-camera stereo-DIC technique was validated by a series of baseline experiments involving 3D surface reconstructions, translation tests, and full-field deformation measurements, which provide a new flexible and practical avenue for measuring surface 3D shape and deformation, particularly in microscopic and high-speed applications.

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