Browsing by Author "Coetzee, Corne J."

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    Evaluating the displacement field of paperboardpackages subjected to compression loading using digital image correlation (DIC)
    (Elsevier, 2020-09) Fadiji, Tobi; Coetzee, Corne J.; Opara, Umezuruike Linus
    Digital image correlation (DIC) is a full-field non-contact optical technique for measuring displacements in experimental testing based on correlating several digital images taken during the test, particularly images before and after deformation. Application of DIC cuts across several fields, particularly in experimental solid mechanics; however, its potential application to paperboard packaging has not been fully explored. To preserve fresh horticultural produce during postharvest handling, it is crucial to understand how the packages deform under mechanical loading. In this study, 3D digital image correlation with two cameras and stereovision was used to determine the full-field displacement of corrugated paperboard packaging subjected to compression loading. Strain fields were derived from the displacement fields. Results obtained from the displacement fields showed the initiation and development of the buckling behaviour of the carton panels. The displacement was observed to be largely heterogeneous. The displacement field in the horizontal direction was smaller compared to that of vertical and out-of-plane directions. In addition, the strain variation increased as load increased, which could be a precursor to material failure. The technique proved to be efficient in providing relevant information on the displacement and strain fields at the surface panels of corrugated paperboard packages used for handling horticultural produce. In addition, it offers prospects for improved mechanical design of fresh produce packaging.
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    The modelling of granular flow using the particle-in-cell method
    (Stellenbosch : University of Stellenbosch, 2004-03) Coetzee, Corne J.; Basson, A. H.; Vermeer, P. A.; University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    Granular flow occurs in a broad spectrum of industrial applications that range from separation and mixing in the pharmaceutical industry, to grinding and crushing, blasting, stockpile construction, flow in and from hoppers, silos, bins, and conveyer belts, agriculture, mining and earthmoving. Two totally different approaches of modelling granular flow are the Discrete Element Method (DEM) and continuum methods such as Finite Element Methods (FEM). Continuum methods can be divided into nonpolar or classic continuum methods and polar continuum methods. Large displacements are usually present during granular flow which, without remeshing, cannot be solved with standard finite element methods due to severe mesh distortion. The Particle-in-Cell (PIC) method, which is a so-called meshless method, eliminates this problem since all the state variables are traced by material points moving through a fixed mesh. The main goal of this research was to model the flow of noncohesive granular material in front of flat bulldozer blades and into excavator buckets using a continuum method. A PIC code was developed to model these processes under plane strain conditions. A contact model was used to model Coulomb friction between the material and the bucket/blade. Analytical solutions, published numerical and experimental results were used to validate the contact model and to demonstrate the code’s ability to model large displacements and deformations. The ability of both DEM and PIC to predict the forces acting on the blade and bucket and the material flow patterns were demonstrated. Shear bands that develop during the flow of material were investigated. As part of the PIC analyses, a comparison between classic continuum and polar continuum (Cosserat) results were made. This includes mesh size and orientation dependency, flow patterns and the forces acting on the blade and the bucket. It is concluded that the interaction of buckets and blades with granular materials can successfully be modelled with PIC. In the cases conducted here, the nonpolar continuum was more accurate than the polar continuum, but the polar continuum results were less dependent on the mesh size. The next step would be to apply this technology to solve industrial problems.