Using arrays of ellipsoidal particles in the Discrete Element Method (DEM) is one of the means to enhance simulations of granular materials. A major challenge in implementing ellipsoidal element to DEM is the development of an efficient and stable contact detection algorithm in order to properly detect contact formation and compute contact forces on the elements. In view of the current available methods in two-dimensional (2D) condition, two different contact detection algorithms for ellipsoidal particles in 3D modelling are identified. Their accuracy and efficiency are compared and the results favour the algorithm based on the geometric potential concept. This algorithm has been implemented in the recently developed DEM code ELLIPSE3D.
Engineering simulation has a significant role in the process of design and analysis of most engineered products at all scales and is used to provide elegant, lightweight , optimized designs. A major step in achieving high confidence in computational models with good predictive capabilities is model validation. It is normal practice to validate simulation models by comparing their numerical results to experimental data. However, current validation practices tend to focus on identifying hot-spots in the data and checking that the experimental and modeling results have a satisfactory agreement in these critical zones. Often the comparison is restricted to a single or a few points where the maximum stress / strain is predicted by the model. The objective of the present paper is to demonstrate a step-by-step approach for performing model validation by combining fullfield optical measurement methodologies with computational simulation techniques. Two important issues of the validation procedure are discussed, i.e. effective techniques to perform data compression using the principles of orthogonal decomposition, as well as methodologies to quantify the quality of simulations and make decisions about model validity. An I-beam with open holes under three-point bending loading is selected as an exemplar of the methodology. Orthogonal decomposition by Zernike shape descriptors is performed to compress large amounts of numerical and experimental data in selected regions of interest (ROI) by reducing its dimensionality while preserving information; and different comparison techniques including traditional error norms, a linear comparison methodology and a concordance coefficient correlation are used in order to make decisions about the validity of the simulation.
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