Photogrammetric method of distant reconstruction of displacement fields in deformable solids

    Research output: ThesisDoctoral Thesis

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    Abstract

    [Truncated] Solids under stress are subject to changes in shape and these changes are normally very small before solids collapse. In many applications, it is important to monitor the small deformation in the solids to understand their behavior under stress and predict their potential failure. Examples are, monitoring performance and stability of structures at a range of scales, monitoring thermal expansion of different parts in electronic circuit boards, studying properties of materials under different conditions, monitoring structural health of aircraft and monitoring stability of mining excavations.

    Deformation monitoring involves measuring the change of position of each point of the object with high accuracy. The displacements of each point in different dimensions help to reconstruct displacement fields, while gradients of the displacements help to reconstruct strain fields. It is often desirable to reconstruct displacement and strain fields from a distance (contactless monitoring) since it reduces interference of the monitoring equipment with the operations of the system.

    An important photogrammetric technique for contactless measurements of deformationin solids with high accuracy is Digital Image Correlation (DIC). It requires only images in the visible range and therefore requires only a simple and inexpensive setup involving camera, computer and uniform lighting source. This gives it the potential to beused in a wide range of contexts, without high capital costs.

    DIC works by tracking points on images taken before and after deformation. It achieves subpixel accuracy by correlating two sections (subsets) of both images where the center of the subset is the point of focus and neighboring points helps to uniquely identify the point of focus in the image and improve accuracy.

    The accuracy achieved using DIC depends on many factors such as the pattern in the images, distortion in images introduced during the image capturing process and selection of subset and image sizes. One of the most critical limitation, however, is the assumption of displacement continuity in the deformation process. It presumes that displacement is continuous and neighboring points in the images remain the same.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    • The University of Western Australia
    Award date4 Jul 2016
    Publication statusUnpublished - 2016

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