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Featured Application: A 3D-DIC system based on a single 3CCD color camera and a cross dichroic prism is proposed in this paper, this system can be applied to situations where three cameras are required for DIC measurement. A robust three-perspective digital image correlation (DIC) system based on a cross dichroic prism and single three charge-coupled device (3CCD) color cameras is proposed in this study. Images from three different perspectives are captured by a 3CCD camera using the cross dichroic prism and two planar mirrors. These images are then separated by different CCD channels to perform correlation calculation with an existing multi-camera DIC algorithm. The proposed system is considerably more compact than the conventional multi-camera DIC system. In addition, the proposed system has no loss of spatial resolution compared with the traditional single-camera DIC system. The principle and experimental setup of the proposed system is described in detail, and a series of tests is performed to validate the system. Experimental results show that the proposed system performs well in displacement, morphology, and strain measurement. [ABSTRACT FROM AUTHOR]

A quick method to directly determine the true stress–strain curve over a large strain range is proposed. The true stress–strain curve includes the post-necking strain, is directly measured via a special multi-camera digital image correlation (DIC) system. A tension test with the standard dog-bone shape specimens is used in the system. The cross-section area of the specimen throughout the test is measured by the DIC, as well as the entire field true strain. The true stress is calculated based on the measured cross-section area and the load. A dual-phase steel with a minimum 780 MPa tensile strength (DP780), as a typical advanced high-strength steel (AHSS), is used in the test to demonstrate the method and to validate the result. The true stress–strain curve including the post-necking data of DP780 is presented. The test result is validated with the theoretical calculation as well as the experimental method. Furthermore, the measured true stress–strain curve is approximated by the power law equation to identify the material constants. The methodology, experimental test, and the evaluated result are described in detail. [ABSTRACT FROM AUTHOR]

A novel 3D digital image correlation (DIC) system based on a single three charge-couple device (3CCD) color camera is proposed in this paper. Images from three different perspectives are captured by a 3CCD camera using a reflective-based pseudo-vision system. These images are then separated by the different CCD channels, and the correlation algorithm for the multi-camera DIC system is adopted to evaluate the images. Compared to the conventional multi-camera DIC system, the proposed system is much more compact. In addition, the proposed system has no loss of spatial resolution, compares to the traditional single camera DIC system. The complex surface measurement ability and the measurement accuracy is significantly improved through the use of the multi-camera DIC algorithm. The principle of the proposed system is described in detail as well as the experimental setup. A series of validation tests are performed, and the results are verified with the commercial 3D-DIC system. [ABSTRACT FROM AUTHOR]

Three dimensional digital image correlation (3D-DIC) has been widely used by industry to measure the 3D contour and whole-field displacement/strain. In this paper, a novel single color camera 3D-DIC setup, using a reflection-based pseudo-stereo system, is proposed. Compared to the conventional single camera pseudo-stereo system, which splits the CCD sensor into two halves to capture the stereo views, the proposed system achieves both views using the whole CCD chip and without reducing the spatial resolution. In addition, similarly to the conventional 3D-DIC system, the center of the two views stands in the center of the CCD chip, which minimizes the image distortion relative to the conventional pseudo-stereo system. The two overlapped views in the CCD are separated by the color domain, and the standard 3D-DIC algorithm can be utilized directly to perform the evaluation. The system’s principle and experimental setup are described in detail, and multiple tests are performed to validate the system. [ABSTRACT FROM AUTHOR]

Three Dimensional digital image correlation(3D-DIC) has been widely used by industry, especially for strain measurement. The traditional 3D-DIC system can accurately obtain the whole-field 3D deformation. However, the conventional 3D-DIC system can only acquire the displacement field on a single surface, thus lacking information in the depth direction. Therefore, the strain in the thickness direction cannot be measured. In recent years, multiple camera DIC (multi-camera DIC) systems have become a new research topic, which provides much more measurement possibility compared to the conventional 3D-DIC system. In this paper, a multi-camera DIC system used to measure the whole-field thickness strain is introduced in detail. Four cameras are used in the system. two of them are placed at the front side of the object, and the other two cameras are placed at the back side. Each pair of cameras constitutes a sub stereo-vision system and measures the whole-field 3D deformation on one side of the object. A special calibration plate is used to calibrate the system, and the information from these two subsystems is linked by the calibration result. Whole-field thickness strain can be measured using the information obtained from both sides of the object. Additionally, the major and minor strain on the object surface are obtained simultaneously, and a whole-field quasi 3D strain history is acquired. The theory derivation for the system, experimental process, and application of determining the thinning strain limit based on the obtained whole-field thickness strain history are introduced in detail. [ABSTRACT FROM AUTHOR]

This article shows an experimental validation of the volume conservation assumption (zero plastic volume change assumption) for aluminum alloy (AA6000) sheet metal. A series of tensile tests were conducted. During the tensile tests, an optimized digital image correlation setup was used to simultaneously measure three principal strain components. The experimental results show that, at locations outside the necking band, AA6000 strictly follows the zero plastic volume change assumption throughout the duration of the test. Inside the necking band, AA6000 follows the zero plastic volume change assumption in the elastic range and early plastic range. However, before failure, a visible volume strain increase can be found inside the necking band, which shows that, in the deep plastic zone, AA6000 does not always follow the volume conservation assumption. The experiment plan, measurement setup optimization, experimental results and data analysis are shown in detail. [ABSTRACT FROM AUTHOR]