Now showing 1 - 3 of 3
  • Publication
    A simple method for particle shape generation with spherical harmonics
    (Elsevier, 2018-05-01) ; ;
    The increasing interest in particle shape influence on granular mechanics necessitates a fast and robust particle shape generation method. We describe a new approach based on rotation-invariant spherical harmonic (SH) analysis. The core of this method is to construct morphology features at various length scales and superimpose them together to form the overall morphology. This method uses four rotation-invariant SH factors to construct SH coefficient matrices. We quantify particle shape at form, roundness, and compactness to establish the linkage between SH factors and traditional shape parameters. It is found that SH factors effectively control particle features at different scales. This method has a great potential to facilitate the research on granular mechanics considering particle shape effects.
      261Scopus© Citations 59
  • Publication
    Particle shape quantification using rotation-invariant spherical harmonic analysis
    (ICE Publishing, 2017-06-01) ; ;
    A three-dimensional (3D) particle surface can be mathematically represented by a spherical harmonic (SH) coefficient matrix through surface parameterisation and SH expansion. However, this matrix depends on not only the particle shape but also the size, position and orientation. This study adopts a rotation-invariant analysis to explore the relationship between SH coefficient matrices and particle shape characteristics. Particle shapes are quantified at different scales (i.e., form, roundness and compactness). These methods are applied to two groups of particles (i.e., Leighton Buzzard sand (LBS) particles and LBS fragments) with distinct shape features. By using rotation invariants, the multi-scale nature of particle shape is illustrated, and two novel shape descriptors are defined. The results in this paper serve as a starting point for the generation of particle shapes with prescribed shape features using spherical harmonic.
      267Scopus© Citations 27
  • Publication
    An FDEM study of particle breakage under rotational point loading
    The most commonly adopted method to test the strength of single sand particles is based on platen experiments. This setup tends to align the loading direction towards the particle minimum axis and provide an upper limit for the breakage stress. This paper numerically bypasses such limitation by using a combined finite and discrete element method (FDEM). FDEM was first validated via a mesh size analysis of a spherical particle and calibrated by in-situ experimental compressions of the single quartz sand particle, where the particle shape was obtained by X-ray micro-computed tomography (XCT) and then imported into the numerical model. Systematic point loading tests were recreated to explore the role of the curvature at contacting points on the breakage behaviour. The simulations allow to probe the same non-spherical particles, i.e., realistic quartz sand and ellipsoid particles, with multiple measurements highlighting the importance of the loading direction, which was inaccessible experimentally. Results show that FDEM can capture not only the crack initiation but also fracture patterns, while taking into account realistic shapes. It is found that the distance between two contact points and their combined curvedness reflecting the particle morphology are the two major factors governing fracture patterns and stresses. When loading is roughly parallel to the minimum principal dimension of particles, the obtained breakage stress and the number of fragments approach the upper limits.
      225Scopus© Citations 41