scholarly journals An Adaptive Discrete Element Method for Physical Modeling of the Selective Laser Sintering Process

2017 ◽  
Vol 869 ◽  
pp. 69-84
Author(s):  
Arash Gobal ◽  
Bahram Ravani
Keyword(s):  
Discrete Element Method ◽  
Physical Modeling ◽  
Selective Laser Sintering ◽  
Dimensional Accuracy ◽  
Discrete Element ◽  
Laser Sintering ◽  
Simulation Accuracy ◽  
Element Size ◽  
Particle Level ◽  
Element Method

Selective Laser Sintering (SLS) has recently become one of the fastest growing additive manufacturing processes due to its capability of fabricating metal parts with high dimensional accuracy and surface quality. Physical modeling of this process plays an important role in properly controlling the process parameters of the process. In this paper, we present a 3 dimensional, adaptive discrete element method for simulation of the SLS process on personal computers. The presented method models the laser-powder interaction at particle level, achieving high simulation accuracy while adaptively increasing the discrete element size as local temperatures drop inside the powder bed for improved efficiency. Numerical shape functions are developed for calculating individual particle temperatures at any point during the simulation. Results show that this physical model improves the runtime significantly in virtual simulation of SLS process without loss of simulation accuracy.

A Surrogate Discrete Element Method for Terramechanics Simulation of Granular Locomotion

2015 ◽  
Author(s):  
William Smith ◽  
Huei Peng
Keyword(s):  
Discrete Element Method ◽  
Discrete Element ◽  
Vehicle Design ◽  
Simulation Accuracy ◽  
Semi Empirical ◽  
And Control ◽  
Drawbar Pull ◽  
Driving Torque ◽  
Dem Model ◽  
Element Method

Numerical modeling methods, such as the discrete element method (DEM), are an increasingly popular alternative to traditional semi-empirical terramechanics techniques. While DEM has many advantages, including the ability to model more complex running gear and terrain profiles, it has not reached widespread popularity due to its high computation costs. In this study a surrogate DEM model (S-DEM) was developed to maintain the simulation accuracy and capabilities of DEM with reduced computation costs. This marks one of the first surrogate models developed for DEM, and the first known model developed for terramechanics. By storing wheel-soil interaction forces and soil velocities extracted from constant-velocity DEM simulations, S-DEM can quickly perform new dynamic wheel locomotion simulations. Using both DEM and S-DEM, wheel locomotion simulations were performed on flat and rough terrain. S-DEM was found to reproduce drawbar pull and driving torque well in both cases, though wheel sinkage errors were significant at times. Computation costs were reduced by three orders of magnitude in comparison to DEM, bringing the benefits of DEM modeling to vehicle design and control. The techniques used to develop S-DEM may be applicable to other common DEM applications, such as soil drilling, excavating, and plowing.

Discrete Element Method for Modeling Penetration

2004 ◽  
Author(s):  
Federico A. Tavarez ◽  
Michael E. Plesha
Keyword(s):  
Discrete Element Method ◽  
Solid Phase ◽  
Bulk Material ◽  
Discrete Element ◽  
Test Problems ◽  
Careful Study ◽  
Specific Test ◽  
Element Size ◽  
Seamless Transition ◽  
Element Method

The Discrete Element Method (DEM) discretizes a material using rigid elements of simple shape. Each element interacts with neighboring elements through appropriate interaction laws. The number of elements is typically large and is limited by computer speed. The method has seen widespread applications to modeling particulate media and more recently to modeling solids such as concrete, ceramic, and metal. For problems with severe damage, DEM offers a number of attractive features over continuum based numerical methods, with the primary feature being a seamless transition from solid phase to particulate phase. This study illustrates the potential of DEM for modeling penetration and briefly points out its numerous advantages. A weakness of DEM is that its convergence properties are not understood. The crucial question is whether convergence is obtained as DEM element size vanishes in the limit of model refinement. The major focus of our investigation will be a careful study of convergence for modeling the degradation of a solid into fragments. Our results show that indeed convergence is obtained in several specific test problems. Moreover, elastic interelement stiffness and damping properties were proven to be particle size-independent. However, convergence in material failure due to crack growth is obtained only if the interparticle potentials are properly constructed as functions of DEM element size and bulk material properties such as elastic modulus and fracture toughness.

scholarly journals A surface mesh represented discrete element method (SMR-DEM) for particles of arbitrary shape

2021 ◽  
Author(s):  
Ling Zhan ◽  
Chong ◽  
Bingyin Zhang ◽  
Wei Wu
Keyword(s):  
Discrete Element Method ◽  
Discrete Element ◽  
System Level ◽  
Contact Method ◽  
Surface Mesh ◽  
Simple Formulation ◽  
Irregular Shapes ◽  
Particle Level ◽  
Particle Assemblies ◽  
Element Method

A surface mesh represented discrete element method (SMR-DEM) for granular systems with arbitrarily shaped particles is presented. The particle surfaces are approximated using contact nodes obtained from surface mesh. A hybrid contact method which combines the benefits of the sphere-to-sphere and shpere-to-surface approaches is proposed for contact detection and force computation. The simple formulation and implementation render SMR-DEM suitable for threedimensional simulations. Furthermore, GPU parallelization is employed to achieve higher efficiency. Several numerical examples are presented to show the performance of SMR-DEM. It is found that on the particle level the method is accurate and convergent, while on the system level SMR-DEM can effiectively model particle assemblies of various regular and complex irregular shapes.

scholarly journals Modeling of High-Density Compaction of Pharmaceutical Tablets Using Multi-Contact Discrete Element Method

Pharmaceutics ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2194
Author(s):  
Kostas Giannis ◽  
Carsten Schilde ◽  
Jan Henrik Finke ◽  
Arno Kwade
Keyword(s):  
Discrete Element Method ◽  
Discrete Element ◽  
Model Parameters ◽  
Pharmaceutical Tablets ◽  
Particle Level ◽  
Scale Calibration ◽  
Pharmaceutical Materials ◽  
Scale Particle ◽  
Uniaxial Compaction ◽  
Element Method

The purpose of this work is to simulate the powder compaction of pharmaceutical materials at the microscopic scale in order to better understand the interplay of mechanical forces between particles, and to predict their compression profiles by controlling the microstructure. For this task, the new framework of multi-contact discrete element method (MC-DEM) was applied. In contrast to the conventional discrete element method (DEM), MC-DEM interactions between multiple contacts on the same particle are now explicitly taken into account. A new adhesive elastic-plastic multi-contact model invoking neighboring contact interaction was introduced and implemented. The uniaxial compaction of two microcrystalline cellulose grades (Avicel® PH 200 (FMC BioPolymer, Philadelphia, PA, USA) and Pharmacel® 102 (DFE Pharma, Nörten-Hardenberg, Germany) subjected to high confining conditions was studied. The objectives of these simulations were: (1) to investigate the micromechanical behavior; (2) to predict the macroscopic behavior; and (3) to develop a methodology for the calibration of the model parameters needed for the MC-DEM simulations. A two-stage calibration strategy was followed: first, the model parameters were directly measured at the micro-scale (particle level) and second, a meso-scale calibration was established between MC-DEM parameters and compression profiles of the pharmaceutical powders. The new MC-DEM framework could capture the main compressibility characteristics of pharmaceutical materials and could successfully provide predictions on compression profiles at high relative densities.

Discrete element method to model cracking for two layer systems

TAPPI Journal ◽  
2019 ◽  
Vol 18 (2) ◽  
pp. 101-108
Author(s):  
Daniel Varney ◽  
Douglas Bousfield
Keyword(s):  
Discrete Element Method ◽  
Flexural Modulus ◽  
Single Layer ◽  
Discrete Element ◽  
Flexural Stress ◽  
Layer System ◽  
Three Point Bending ◽  
Moving Force ◽  
Coating Layers ◽  
Element Method

Cracking at the fold is a serious issue for many grades of coated paper and coated board. Some recent work has suggested methods to minimize this problem by using two or more coating layers of different properties. A discrete element method (DEM) has been used to model deformation events for single layer coating systems such as in-plain and out-of-plain tension, three-point bending, and a novel moving force picking simulation, but nothing has been reported related to multiple coating layers. In this paper, a DEM model has been expanded to predict the three-point bending response of a two-layer system. The main factors evaluated include the use of different binder systems in each layer and the ratio of the bottom and top layer weights. As in the past, the properties of the binder and the binder concentration are input parameters. The model can predict crack formation that is a function of these two sets of factors. In addition, the model can predict the flexural modulus, the maximum flexural stress, and the strain-at-failure. The predictions are qualitatively compared with experimental results reported in the literature.

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