3D quantitative shape analysis on form, roundness, and compactness with μCT

Abstract

Particle shape plays an important role in determining the engineering behaviour of granular materials. In this regard, characterisation and quantification of particle shape are essential for understanding the behaviour of granular materials. X-ray micro-computed tomography (μCT) enables observation of particle morphology at ever-greater resolutions. The challenge has thus become extracting quantified shape parameters from these rich three-dimensional (3D) images. In this paper, we implement X-ray μCT to obtain 3D particle morphology and utilize image processing and analysis techniques to quantify it at different scales. A novel framework is proposed to measure 3D shape parameters of form, roundness, and compactness. New 3D roundness indexes were formulated from the local curvature on reconstructed triangular surface mesh. Subsequently, this method is utilized to study the change of particle shape by single particle crushing tests on Leighton Buzzard sand (LBS) particles. It is found that compactness value (i.e., sphericity) could be influenced by both form and roundness. Then, the distributions of shape parameters are characterised by Weibull statistics. It shows that single particle crushing tests generate more irregular fragments which have smaller shape parameters with larger variance for the measured shape parameters.

Quantification of the morphology of shelly carbonate sands using 3D images

“…The aim of this mesh-smoothing step is to remove the small-scale features that will fall into roughness classification rather than overall form, according to the definitions given by Barrett (1980). The smoothing process consisted of reducing the number of triangles of a grain to a target value, in this case set to 1500, as suggested by Zhao & Wang (2016), using reducepatch. This function reduces the number of triangles, while preserving the overall shape of the original grain.…”

“…The mean curvature, taken as the average of k 1 and k 2 , was reported to be adequate to capture the curvature of a vertex on the 3D surface mesh for silica sand grains (Zhao & Wang, 2016). For the case of shelly carbonate grains, the highly irregular and concave shapes lead to negative k 2 values, and for this reason k m was obtained by averaging the absolute values of k 1 and k 2 .…”

Application of spherical harmonics analysis on LBS particles and LBS fragments

“…LBS particles and LBS fragments were scanned with X-ray micro-tomography (μCT) systems with a resolution of 15 μm and 3 μm, respectively. The LBS particles have particle size between 1 and 2 mm, while the LBS fragments are larger than 0.001 mm 3 . The raw CT images were put through a series of image processing methods to obtain the smooth triangular surface mesh [3], based on which we performed the spherical harmonics analysis and shape quantification at form, roundness and compactness.…”

“…We followed the framework proposed in [3] to quantify the surface reconstructed with spherical harmonics at form, /b). Then, the representative aspect ratio (AR) was defined as the average value of EI and FI.…”

“…mechanical behaviour of granular materials) [1] and understand the broad class of phenomena that involve shape evolution (e.g. weathering and fragmentation) [2][3][4]. The simplest way to obtain shape parameters (e.g.…”