Hybrid finite‑discrete element simulator based on GPGPU‑parallelized computation for modelling crack initiation and coalescence in sandy mudstone with prefabricated cross-flaws under uniaxial compression

2021 ◽  
pp. 107658
Author(s):  
Dongxu Liang ◽  
Nong Zhang ◽  
Hongyuan Liu ◽  
Daisuke Fukuda ◽  
Haoyu Rong
Keyword(s):  
Crack Initiation ◽  
Uniaxial Compression ◽  
Discrete Element ◽  
Element Simulator ◽  
Sandy Mudstone

scholarly journals Experimental and Numerical Studies on Crack Initiation and Coalescence in Sandy Mudstone with Prefabricated Cross-Flaws Under Uniaxial Compression

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Dongxu Liang ◽  
Nong Zhang ◽  
Haoyu Rong ◽  
Zhe Xiang
Keyword(s):  
Numerical Simulation ◽  
Crack Initiation ◽  
Uniaxial Compression ◽  
Rock Bridge ◽  
Crack Initiation Stress ◽  
Dip Angle ◽  
Two Parameters ◽  
Initiation Stress ◽  
Main Flaw ◽  
Sandy Mudstone

The purpose of this paper is to study the crack initiation, propagation, and coalescence of the sandy mudstone sample with two sets of prefabricated cross-flaws under uniaxial compression. This study is different from previous studies on single or multiple parallel prefabricated flaws. The prefabricated cross-flaws are characterized by the dip of the rock bridge with the direction of the main flaw ( β ) and the angle between the direction of main and minor flaws ( γ ). The effects of these two parameters on crack initiation, propagation, coalescence, crack initiation stress, and coalescence stress are analyzed. Moreover, numerical simulation of the uniaxial compression experiments is performed using PFC2D with a flat-joint model, and the simulation results are in good agreement with those from the experiments. The results demonstrate that the dip angle of the rock bridge with the direction of the main flaw ( β ) has strong effects on the crack initiation and coalescence stresses. The larger the angle between the direction of main and minor flaws γ , the greater the crack initiation and coalescence stresses. The crack initiation stress is reduced for the case with cross-flaws compared with that with non-cross-flaws. Meanwhile, the connection type of main flaws and the width of the crack coalescence zone are difficult to observe through the experiments and are discovered from the numerical simulation.

Simulation of Uniaxial Compression for Flexible Fibers of Wheat Straw Using the Discrete Element Method

2021 ◽  
Vol 64 (6) ◽  
pp. 2025-2034
Author(s):  
Matthew W Schramm ◽  
Mehari Z. Tekeste ◽  
Brian L Steward
Keyword(s):  
Discrete Element Method ◽  
Wheat Straw ◽  
Young’S Modulus ◽  
Uniaxial Compression ◽  
Material Properties ◽  
Young's Modulus ◽  
Discrete Element ◽  
Flexible Fibers ◽  
Dem Model ◽  
Element Method

HighlightsSimulation of uniaxial compression was performed with flexible fibers modeled in DEM.Bond-specific DEM parameters were found to be sensitive in uniaxial compression.A calibration technique that is not plunger-dependent is shown and validated.Abstract. To accurately simulate a discrete element method (DEM) model, the material properties must be calibrated to reproduce bulk material behavior. In this study, a method was developed to calibrate DEM parameters for bulk fibrous materials using uniaxial compression. Wheat straw was cut to 100.2 mm lengths. A 227 mm diameter cylindrical container was loosely filled with the cut straw. The material was pre-compressed to 1 kPa. A plunger (50, 150, or 225 mm diameter) was then lowered onto the compressed straw at a rate of 15 mm s-1. This experimental procedure was simulated using a DEM model for different material properties to generate a simulated design of experiment (DOE). The simulated plunger had a travel rate of 40 mm s-1. The contact Young’s modulus, bond Young’s modulus, and particle-to-particle friction DEM parameters were found to be statistically significant in the prediction of normal forces on the plunger in the uniaxial compression test. The DEM calibration procedure was used to approximate the mean laboratory results of wheat straw compression with root mean square (RMS) percent errors of 3.77%, 3.02%, and 13.90% for the 50, 150, and 225 mm plungers, respectively. Keywords: Calibration, DEM, DOE, Flexible DEM particle, Uniaxial compression, Wheat straw.

Numerical investigation of micro-cracking behavior of brittle rock containing a pore-like flaw under uniaxial compression

2020 ◽  
Vol 29 (10) ◽  
pp. 1543-1568 ◽  
Author(s):  
Louis Ngai Yuen Wong ◽  
Jun Peng
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Numerical Model ◽  
Crack Initiation ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Early Stage ◽  
Brittle Rock ◽  
Cracking Behavior ◽  
Cracking Process

Pore-like flaws, which are commonly encountered in brittle rock, play an important role in the engineering performance of structures constructed in or on rock. Experimental and numerical investigations of micro-cracking mechanism of rock containing a pore-like flaw can enhance our knowledge of rock damage/failure from a microscopic view. In this study, the influences of a two-dimensional circular pore-like flaw with respect to its diameter and position on the strength and micro-cracking behavior of brittle rock under uniaxial compression are numerically investigated. The results reveal that the strength and elastic modulus are significantly affected by the diameter and position in the pore. The uniaxial compressive strength and elastic modulus of the numerical model with a pore diameter of 15.44 mm located in the center of the model are found to decrease by 58.6% and 56.4% respectively when compared with those of the intact model without a pore. As the pore position varies while the porosity remains unchanged, the simulated uniaxial compressive strength and elastic modulus are also found to be generally smaller than those of the intact model without a pore. When a pore-containing numerical model is loaded, the micro-cracks are found to mostly initiate at the top and bottom of the pore, due to the local tensile stress increase. The simulation results of the early-stage micro-cracking process and stress distribution are in a generally good agreement with the analytical solution obtained from the Kirsch equations. The grain-based model used in this study can not only study the crack initiation on the boundary of the pore but also provide a convenient means to analyze and visualize the temporal and spatial micro-cracking process after the crack initiation, which accounts for the variations in the simulated strength and modulus satisfactorily from a micro-cracking view.

Discrete element method simulations of fracture in concrete under uniaxial compression based on its real internal structure

2017 ◽  
Vol 27 (4) ◽  
pp. 578-607 ◽  
Author(s):  
Jan Suchorzewski ◽  
Jacek Tejchman ◽  
Michał Nitka
Keyword(s):  
Discrete Element Method ◽  
Uniaxial Compression ◽  
Three Dimensional ◽  
Discrete Element ◽  
Cement Matrix ◽  
Two Dimensional ◽  
Compression Tests ◽  
Digital Microscope ◽  
Complex Crack ◽  
Element Method

The paper describes experimental and numerical results of concrete fracture under quasi-static uniaxial compression. Experimental uniaxial compression tests were performed on concrete cubic specimens. Fracture in concrete was detected at the aggregate level by means of three non-destructive methods: three-dimensional X-ray microcomputed tomography, two-dimensional scanning electron microscope and manual two-dimensional digital microscope. The discrete element method was used to directly simulate experiments. Concrete was modelled as a random heterogeneous four-phase material composed of aggregate particles, cement matrix, interfacial transitional zones and macrovoids based on experimental images. Two- and three-dimensional analyses were carried out. In two-dimensional analyses, the real aggregate shape was created by means of clusters of spheres. In three-dimensional calculations, spheres were solely used. A satisfactory agreement between numerical and experimental results was achieved in two-dimensional analyses. The model was capable of accurately predicting complex crack paths and the corresponding stress–strain responses observed in experiments.

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