Accuracy-enhanced constitutive parameter identification using virtual fields method and special stereo-digital image correlation

Single‐camera special stereo‐digital image correlation applied for accurate virtual fields method identification

“…The measured strain fields become much smoother due to the load increasing. Compared with the corresponding strain fields in Zhang et al, which measured by a SS‐DIC system equipped with two cameras (with 2,448 × 2,048 pixels spatial resolution), there are more disturbances in the strain fields shown in Figure . The disturbances may be caused by the systematic error of the measuring system, since the errors of strain (Figure ) cannot be ignored compared with the amplitude of measured strain (Figure ).…”

“…To minimise the impact of the strain noise, an optimised piecewise virtual field is employed for the elastic parameters identification of the tested specimen . The details about the virtual fields are listed in Table , which are same with that in Zhang et al The and in Table represent the virtual displacement component of the vertical and horizontal directions, respectively. Note that the hole was deleted from the ROI in the correlation analysis.…”

“…Inspired by the two digital cameras‐based SS‐DIC and colour stereo‐DIC proposed in Zhang et al and Yu and Pan, a single 3CCD colour camera‐based SS‐DIC method is proposed (Figure ). The proposed SS‐DIC method composed of a 3CCD colour camera, a beam splitter prism located in front of the camera, a right‐angle prism placed before the beam splitter prism, a blue band‐pass filter attached to the right and front of the right‐angle prism, a red band‐pass filter attached to the left side of the beam splitter prism, two plane mirrors placed oblique to the left side of the beam splitter prism and right‐angle prism (with an oblique angle of 45°), and a plane mirror placed oblique to the right side of the right‐angle prism.…”

“…Stereo‐digital image correlation (stereo‐DIC) can minimise the impact due to out‐of‐plane displacement. However, the measured data points in stereo‐DIC are distributed unevenly in space since both the optical axis of two cameras are generally not perpendicular to the tested object. The unevenly distributed data points measured by stereo‐DIC are of different element area (or spatial resolution).…”

“…To accurately calculate the internal virtual work without bringing in redundant computation, a “special” stereo‐DIC method (SS‐DIC) was established recently . By making the sensor of the left camera parallel to the tested object and the sensor of right camera oblique to the measured object, SS‐DIC ensures the spatially evenly distributed data points on the planar object surface.…”