scholarly journals Modeling acoustic emissions in heterogeneous rocks during tensile fracture with the Discrete Element Method

2020 ◽  
Vol 2 ◽  
pp. 1-None
Author(s):  
Robert A. Caulk
Keyword(s):  
Discrete Element Method ◽  
Acoustic Emissions ◽  
Discrete Element ◽  
Tensile Fracture ◽  
Heterogeneous Rocks ◽  
Element Method

scholarly journals Micromechanical modeling of snow failure

2019 ◽  
Author(s):  
Grégoire Bobillier ◽  
Bastian Bergfeld ◽  
Achille Capelli ◽  
Jürg Dual ◽  
Johan Gaume ◽  
...  
Keyword(s):  
Discrete Element Method ◽  
Crack Propagation ◽  
Computational Cost ◽  
Discrete Element ◽  
Micromechanical Modeling ◽  
Tensile Fracture ◽  
Macroscopic Behavior ◽  
Weak Layer ◽  
Snow Model ◽  
Element Method

Abstract. Dry-snow slab avalanches start with the formation of a local failure in a highly porous weak layer underlying a cohesive snow slab. If followed by rapid crack propagation within the weak layer and finally a tensile fracture through the slab appears, a slab avalanche releases. While the basic concepts of avalanche release are relatively well understood, performing fracture experiments in the lab or in the field can be difficult due to the fragile nature of weak snow layers. Numerical simulations are a valuable tool for the study of micromechanical processes that lead to failure in snow. We used a three-dimensional discrete element method (3D-DEM) to simulate and analyze failure processes in snow. Cohesive and cohesionless ballistic deposition allowed us to reproduce porous weak layers and dense cohesive snow slabs, respectively. To analyze the micromechanical behavior at the scale of the snowpack (~ 1 m), the particle size was chosen as a compromise between a low computational cost and a detailed representation of important micromechanical processes. The 3D-DEM snow model allowed reproducing the macroscopic behavior observed during compression and mixed-modes loading of dry snow slab and weak snow layer. To be able to reproduce the range of snow behavior (elastic modulus, strength), relations between DEM particle/contact parameters and macroscopic behavior were established. Numerical load-controlled failure experiments were performed on small samples and compared to results from load-controlled laboratory tests. Overall, our results show that the discrete element method allows to realistically simulate snow failure processes. Furthermore, the presented snow model seems appropriate for comprehensively studying how the mechanical properties of slab and weak layer influence crack propagation preceding avalanche release.

scholarly journals Music of grain crushing with the Discrete Element Method

2021 ◽  
Vol 249 ◽  
pp. 07009
Author(s):  
Li Zeng ◽  
Andres Alfonso Peña Olarte ◽  
Roberto Cudmani
Keyword(s):  
Discrete Element Method ◽  
3D Visualization ◽  
Acoustic Emissions ◽  
Discrete Element ◽  
Compression Tests ◽  
Compression Process ◽  
Practical Applications ◽  
Grain Crushing ◽  
The Impact ◽  
Element Method

A series of compression tests on agglomerates of microspheres representing a single grain are conducted to investigate the impact of heterogeneity on the acoustic emissions (AE) generation. The grain heterogeneity is realized by using a Weibull shape parameter-augmented traditional discrete element method (DEM). During the compression process the development of the micro-cracks, and the magnitude and location of the AE events are tracked and recorded. Through a 3D visualization of the AE events, their location and the clustered broken bonds are identified. The current study demonstrates the potential of AE measurements to track changes in the fabric and structure of granular materials. The results of this DEM study will contribute to clarify the mechanism of particle breakage and its consideration in practical applications.

Influence of mesh orientation in discrete element method simulations of fracture processes

2018 ◽  
Vol 53 (6) ◽  
pp. 400-407 ◽  
Author(s):  
Gabriel Birck ◽  
Ignacio Iturrioz ◽  
Jorge D Riera ◽  
Letícia FF Miguel
Keyword(s):  
Discrete Element Method ◽  
Failure Modes ◽  
Discrete Element ◽  
Tensile Fracture ◽  
Unconfined Compression ◽  
Numerical Predictions ◽  
Homogeneous Stress ◽  
Cylindrical Samples ◽  
Fracture Processes ◽  
Element Method

The lattice discrete element method was employed by the authors in numerical determinations of the pre and post peak-failure response of quasi-brittle systems in which tensile fracture typically controls the dominant failure modes. In previous publications, the approach has also been applied to structures that fail by shear or unconfined compression. It was also verified that discrete element method models predict the strength of cubic and cylindrical samples subjected to confining lateral pressures up to about 20% of the vertical stress, although overestimating the effect of confinement. One of the factors responsible for this overestimation may be associated to the restraints on the fracture paths introduced by numerical methods such as discrete element method or finite element method . In order to determine a bound on model error in discrete element method numerical predictions, in this article, the influence of the mesh orientation on simulations of fracture propagation in quasi-brittle materials is examined in case of a plate subjected to a nominally homogeneous stress state.

scholarly journals Micromechanical modeling of snow failure

2020 ◽  
Vol 14 (1) ◽  
pp. 39-49 ◽  
Author(s):  
Grégoire Bobillier ◽  
Bastian Bergfeld ◽  
Achille Capelli ◽  
Jürg Dual ◽  
Johan Gaume ◽  
...  
Keyword(s):  
Discrete Element Method ◽  
Crack Propagation ◽  
Discrete Element ◽  
Micromechanical Modeling ◽  
Tensile Fracture ◽  
Snow Layer ◽  
Macroscopic Behavior ◽  
Weak Layer ◽  
Snow Model ◽  
Element Method

Abstract. Dry-snow slab avalanches start with the formation of a local failure in a highly porous weak layer underlying a cohesive snow slab. If followed by rapid crack propagation within the weak layer and finally a tensile fracture through the slab, a slab avalanche releases. While the basic concepts of avalanche release are relatively well understood, performing fracture experiments in the laboratory or in the field can be difficult due to the fragile nature of weak snow layers. Numerical simulations are a valuable tool for the study of micromechanical processes that lead to failure in snow. We used a three-dimensional discrete element method (3-D DEM) to simulate and analyze failure processes in snow. Cohesive and cohesionless ballistic deposition allowed us to reproduce porous weak layers and dense cohesive snow slabs, respectively. To analyze the micromechanical behavior at the scale of the snowpack (∼1 m), the particle size was chosen as a compromise between low computational costs and detailed representation of important micromechanical processes. The 3-D-DEM snow model allowed reproduction of the macroscopic behavior observed during compression and mixed-mode loading of dry-snow slab and the weak snow layer. To be able to reproduce the range of snow behavior (elastic modulus, strength), relations between DEM particle and contact parameters and macroscopic behavior were established. Numerical load-controlled failure experiments were performed on small samples and compared to results from load-controlled laboratory tests. Overall, our results show that the discrete element method allows us to realistically simulate snow failure processes. Furthermore, the presented snow model seems appropriate for comprehensively studying how the mechanical properties of the slab and weak layer influence crack propagation preceding avalanche release.

Simulation on heterogeneous rocks with a flaw using grain-based discrete-element method

2021 ◽  
Vol 11 (1) ◽  
pp. 1-10
Author(s):  
L. Liu ◽  
H. Li ◽  
X. Li ◽  
C. Zhou ◽  
G. Zhang
Keyword(s):  
Discrete Element Method ◽  
Discrete Element ◽  
Heterogeneous Rocks ◽  
Element Method

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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