Assessment of High Speed Imaging Systems for 2D and 3D Deformation Measurements: Methodology Development and Validation

Abstract

Ultra high-speed and moderate speed image acquisition platforms have been characterized, with special emphasis on the variability and accuracy of the measurements obtained when employed in either 2D or 3D computer vision systems for deformation and shape measurements. Specifically, the type of image distortions present in both single channel cameras (HS-CMOS) and multi-channel image intensified cameras (UHS-ICCD) are quantified as part of the overall study, and their effect on the accuracy of experimental measurements obtained using digital image correlation have been determined. Results indicate that established methods for noise suppression and recently developed models for distortion correction can be used effectively in situations where the primary intensity noise components are characterized by minimal cross-talk and stationary spatial distortions. Baseline uniaxial tension experiments demonstrate that image correlation measurements using high speed imaging systems are unbiased and consistent with independent deformation measurements over the same length scale, with point-to-point strain variations that are similar to results obtained from translation experiments. In this study, the point-to-point variability in strain using the image intensified system is on the order of 0.001, whereas the non-intensified system had variability of 0.0001. Results confirm that high speed imaging systems can be utilized for full field two and three-dimensional measurements using digital image correlation methods.

Full-Field Strain Measurement and Identification of Composites Moduli at High Strain Rate with the Virtual Fields Method

“…Their main drawback is the fact that they record frames on different CCD or CMOS sensors which can generate systematic errors coming from intensity variations, small misalignments, etc. A recent paper by Tiwari et al clearly underlines the problems encountered with such cameras and proposes a few solutions to try to improve the performances [7]. Another drawback for these types of cameras is that they only allow to record a constant limited number of frames (equal to the number of sensors) which limits the duration of the acquisition and thus requires a very accurate control of the triggering.…”

Identification of the Dynamic Properties of Al 5456 FSW Welds Using the Virtual Fields Method

“…This camera possesses 16 CCD sensors and a beam splitter spreading the light through the 16 channels, enabling extremely fast imaging as the limiting factor is electronic gating. However, the downside of this technology concerns the use of light ampliers (ICCD sensors) causing issues in the imaging, as will be demonstrated later on in this article and illustrated in previous studies [21,22]. Some details concerning the camera and lens are reported in Table 1.…”

“…The camera was positioned facing the specimen with the lens axis normal to the observed surface. performed on the images [22]. All images were processed using the 2D-DIC software VIC-2D [49].…”

“…Studies regarding the performance of high speed and ultra-high speed imaging systems have been reported in the past few years, e.g. [21,22]. These technologies enable temporal resolutions on the order of a microsecond and below with good spatial resolution, making it possible to measure both full-eld strains and accelerations with excellent temporal and spatial resolutions; this is essential for the current study.…”

Identification of Materials Mechanical Properties from Full-Field Measurements: Latest Advances in the Virtual Fields Method

“…Many artefacts exist that must be corrected for, and there are also difficult issues with consistent lighting. An interesting discussion on this topic can be found in [20]. Some applications have been attempted recently for elasto-plastic materials [21,22] but the subject is still in its infancy, particularly for strain rates above 100 s -1 , using ultra-high speed cameras.…”