A Nonlocal Lattice Particle Framework for Modeling of Solids

2016 ◽  
Author(s):  
Hailong Chen ◽  
Yongming Liu
Keyword(s):  
Discrete Element ◽  
Discrete Models ◽  
Poisson's Ratio ◽  
Particle Model ◽  
Spatial Derivative ◽  
Solid Materials ◽  
Numerical Examples ◽  
Anisotropic Solid ◽  
Discontinuous Problems ◽  
Lattice Particle

In this paper, we present a nonlocal lattice particle framework for modeling the brittle behaviors of both isotropic and anisotropic solid materials. Different from other continuum based models, the formulation of this lattice particle model is discrete and there is no spatial derivative involved. This avoids the singularity issues of discontinuous problems, which commonly exists in continuum based models. The model is also nonlocal that a discrete element can interacts with its neighbors up to certain distance. This nonlocality better solves some issues in other discrete models, such as fixed range of Poisson’s ratio. The modeling capability and accuracy are demonstrated using numerical examples.

scholarly journals Analysis of Inter-particle Contact Parameters of Garlic Cloves Using Discrete Element Method

2021 ◽  
Author(s):  
Donghyeok Park ◽  
Chun Gu Lee ◽  
Doee Yang ◽  
Daehyun Kim ◽  
Joon Yong Kim ◽  
...  
Keyword(s):  
Discrete Element Method ◽  
Discrete Element ◽  
Prediction Equation ◽  
Angle Of Repose ◽  
Particle Model ◽  
Bulk Properties ◽  
Simulation Results ◽  
Contact Parameters ◽  
Number Of Particles ◽  
Residual Number

Abstract Purpose The discrete element method (DEM) can be used in agricultural fields such as crop sowing, harvesting, and crop transportation. Nevertheless, modeling complex crops as appropriately shaped particles remains challenging. The modeling of particles and the calibration of input parameters are important for simulating the realistic behaviors of particles using the DEM. Methods In this study, particle models representing the morphological characteristics and size deviations of garlic cloves were proposed. Additionally, the coefficients of friction were analyzed as the contact parameters of the particles based on the heap formation experiments and simultations of the swing-arm method using 150 garlic cloves. Results The simulation results were analyzed that the residual number of particles, a bulk property that can be measured simply in the experiment, is related to the coefficients of friction. In the heap formation experiments with low particle counts, the bulk properties were more clearly differentiated by the residual number of particles than the angle of repose. Moreover, the bulk properties similar to the actual garlic could not be expressed as a spherical particle model. Thus, an equation for predicting the residual number of particles was derived for the non-spherical garlic clove particle model. Five sets of coefficients of friction were presented using the prediction equation, and all the simulation results were close to the actual residual number of particles and angle of repose of the garlic. Conclusions Although the sizes of garlic cloves have a wide distribution, appropriate inter-particle contact parameters could be predicted. Therefore, the calibration process of the DEM can be shortened using the proposed prediction equation for the residual number of particles with non-spherical particles.

scholarly journals Wave-induced stress and breaking of sea ice in a coupled hydrodynamic–discrete-element wave–ice model

2017 ◽  
Author(s):  
Agnieszka Herman
Keyword(s):  
Sea Ice ◽  
Wave Attenuation ◽  
Wave Model ◽  
Discrete Element ◽  
Two Dimensions ◽  
Particle Model ◽  
Time Step ◽  
Bonded Particle Model ◽  
Induced Stress ◽  
Wave Induced

Abstract. In this paper, a coupled sea ice–wave model is developed and used to analyze the variability of wave-induced stress and breaking in sea ice. The sea ice module is a discrete-element bonded-particle model, in which ice is represented as cuboid "grains" floating on the water surface that can be connected to their neighbors by elastic "joints". The joints may break if instantaneous stresses acting on them exceed their strength. The wave part is based on an open-source version of the Non-Hydrostatic WAVE model (NHWAVE). The two parts are coupled with proper boundary conditions for pressure and velocity, exchanged at every time step. In the present version, the model operates in two dimensions (one vertical and one horizontal) and is suitable for simulating compact ice in which heave and pitch motion dominates over surge. In a series of simulations with varying sea ice properties and incoming wavelength it is shown that wave-induced stress reaches maximum values at a certain distance from the ice edge. The value of maximum stress depends on both ice properties and characteristics of incoming waves, but, crucially for ice breaking, the location at which the maximum occurs does not change with the incoming wavelength. Consequently, both regular and random (Jonswap spectrum) waves break the ice into floes with almost identical sizes. The width of the zone of broken ice depends on ice strength and wave attenuation rates in the ice.

A Discrete Element Method for the Analysis of Plane Elasto-Plastic Stress Problems

1966 ◽  
Vol 17 (1) ◽  
pp. 83-104 ◽  
Author(s):  
G. G. Pope
Keyword(s):  
Discrete Element Method ◽  
Plane Stress ◽  
Discrete Element ◽  
Stress Strain ◽  
Numerical Examples ◽  
Matrix Notation ◽  
The Matrix ◽  
Triangular Elements ◽  
Plastic Stress ◽  
Element Method

SummaryA procedure is developed for the analysis of plane stress problems when yielding occurs locally. The region is divided into triangular elements and the deformation is analysed on a step-by-step basis, using the matrix notation developed by Argyris. The simple expressions which are derived for the element properties are applicable with any stress-strain relations which are stable and time-independent. Simple numerical examples are given.

scholarly journals A discrete mesoscopic particle model of the mechanics of a multi-constituent arterial wall

2016 ◽  
Vol 13 (114) ◽  
pp. 20150964 ◽  
Author(s):  
Alexandra Witthoft ◽  
Alireza Yazdani ◽  
Zhangli Peng ◽  
Chiara Bellini ◽  
Jay D. Humphrey ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Arterial Wall ◽  
Dissipative Particle Dynamics ◽  
Mechanical Tests ◽  
Discrete Models ◽  
Particle Model ◽  
Fibre Reinforcement ◽  
Collagen Fibres ◽  
Seamless Integration ◽  
Basic Features

Blood vessels have unique properties that allow them to function together within a complex, self-regulating network. The contractile capacity of the wall combined with complex mechanical properties of the extracellular matrix enables vessels to adapt to changes in haemodynamic loading. Homogenized phenomenological and multi-constituent, structurally motivated continuum models have successfully captured these mechanical properties, but truly describing intricate microstructural details of the arterial wall may require a discrete framework. Such an approach would facilitate modelling interactions between or the separation of layers of the wall and would offer the advantage of seamless integration with discrete models of complex blood flow. We present a discrete particle model of a multi-constituent, nonlinearly elastic, anisotropic arterial wall, which we develop using the dissipative particle dynamics method. Mimicking basic features of the microstructure of the arterial wall, the model comprises an elastin matrix having isotropic nonlinear elastic properties plus anisotropic fibre reinforcement that represents the stiffer collagen fibres of the wall. These collagen fibres are distributed evenly and are oriented in four directions, symmetric to the vessel axis. Experimental results from biaxial mechanical tests of an artery are used for model validation, and a delamination test is simulated to demonstrate the new capabilities of the model.

Numerical Simulation of Granite on Pre-Stressed Machining by Discrete Element Method (DEM)

2013 ◽  
Vol 372 ◽  
pp. 646-649 ◽  
Author(s):  
Yong Ye ◽  
Liang Kang
Keyword(s):  
Discrete Element Method ◽  
Fracture Behavior ◽  
Discrete Element ◽  
Machining Process ◽  
Particle Model ◽  
Transgranular Fracture ◽  
Transverse Cracks ◽  
Bonded Particle Model ◽  
Radial Cracks ◽  
Element Method

The bonded particle model (BPM) of granite for pre-stressed machining is build by using the discrete element method (DEM). This model can not only descript the intergranular fracture behavior but also the transgranular fracture behavior of the granite. The processes of crack propagation under different pre-stressed machining conditions are studied by means of DEM simulation. Damages and cracks of surface/subsurface are also observed. The simulation results show that, while the magnitude of pre-stress is controlled in a certatin range, the number of radial cracks reduce as the increasing of pre-stress magnitude, contray to the transverse cracks. It could be seen that maching damage is decreased and surface quality is improved by applying the pre-stressed machining method, and the discrete element method is an effective way to simulate the machining process of granite.

scholarly journals Topology Optimization using the Discrete Element Method. Part 1: Methodology, Validation, and Geometric Nonlinearity

2021 ◽  
Author(s):  
Connor O'Shaughnessy ◽  
Enrico Masoero ◽  
Peter D. Gosling
Keyword(s):  
Topology Optimization ◽  
Discrete Element Method ◽  
Geometric Nonlinearity ◽  
Discrete Element ◽  
Optimization Method ◽  
Discrete Models ◽  
Structural Topology ◽  
Manufacturing Techniques ◽  
Strain Energy Minimization ◽  
Element Method

Structural Topology optimization is attracting increasing attention as a complement to additive manufacturing techniques. The optimization algorithms usually employ continuum-based Finite Element analyses, but some important materials and processes are better described by discrete models, for example granular materials, powder-based 3D printing, or structural collapse. To address these systems, we adapt the established framework of SIMP Topology optimization to address a system modelled with the Discrete Element Method. We consider a typical problem of strain energy minimization, for which we define objective function and related sensitivity for the Discrete Element framework. The method is validated for simply supported beams discretized as interacting particles, whose predicted optimum solutions match those from a classical continuum-based algorithm. A parametric study then highlights the effects of mesh dependence and filtering. An advantage of the Discrete Element Method is that geometric nonlinearity is captured without additional complexity; this is illustrated when changing the beam supports from rollers to hinges, which indeed generates different optimum structures. The proposed Discrete Element Topology Optimization method enables future incorporation of nonlinear interactions, as well discontinuous processes such as during fracture or collapse.

Computational Aspects in the Elasto/Viscoplastic Material Behavior of Solids

2012 ◽  
Vol 567 ◽  
pp. 192-199 ◽  
Author(s):  
Fabio de Angelis
Keyword(s):  
Constitutive Model ◽  
Material Behavior ◽  
Inelastic Behavior ◽  
Viscoplastic Material ◽  
Solid Materials ◽  
Numerical Examples ◽  
Computational Aspects ◽  
Computational Procedures ◽  
Consistent Tangent Operator ◽  
Algorithmic Procedure

In the present paper a computational algorithmic procedure is presented for modeling the elasto/viscoplastic behavior of solid materials. The effects of different loading programs on the inelastic behavior of rate-sensitive materials are analyzed with specific numerical examples. An appropriate solution scheme and a consistent tangent operator are applied which are capable to be adopted for general computational procedures. Numerical computations and results are reported which illustrate the rate-dependence of the constitutive model in use.

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