scholarly journals Grain Size Effect on the Mechanical Behavior of Cohesionless Coarse-Grained Soils with the Discrete Element Method

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
Renjie Wen ◽  
Cai Tan ◽  
Yong Wu ◽  
Chen Wang
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Shear Strength ◽  
Size Effect ◽  
Discrete Element Method ◽  
Discrete Element ◽  
Force Chain ◽  
Coarse Grained ◽  
Biaxial Compression ◽  
Grain Sizes

Biaxial compression tests with the same specimen size and different maximum grain sizes were simulated for coarse-grained soils using the discrete element method to study the influence of grain size on the mechanical properties and force chain. The maximum grain sizes were 40, 20, 10, and 5 mm, respectively. The grading with self-similar fractal structure in mass is designed to ensure the same pore structure for soils. The shear strength increased with the increase in maximum grain size. Evident increase in shear strength and significant size effect were observed when the ratio of the specimen diameter to maximum grain size was less than five. The shear dilation of coarse-grained soils increases with the increase in maximum grain size. The contact force distribution was uniform when maximum grain size was small but tends to be uneven with the increase in maximum grain size, thereby causing the increase in shear strength by stable strong force chains. This finding demonstrates size effect on the mechanical properties and force chain of cohesionless coarse-grained soils under the biaxial compression condition.

Effects of Rolling Resistance on Shear Behavior and Anisotropy of Granular Matters

2013 ◽  
Vol 631-632 ◽  
pp. 198-204
Author(s):  
Yi Ming Liu ◽  
Hai Jun Mao ◽  
Chun He Yang
Keyword(s):  
Shear Strength ◽  
Discrete Element Method ◽  
Numerical Simulations ◽  
Rolling Resistance ◽  
Discrete Element ◽  
Shear Behavior ◽  
Contact Model ◽  
Biaxial Compression ◽  
Compression Tests ◽  
Dramatic Effect

Standard discrete element method does not take the effect of rolling resistance into account. To overcome this shortcoming, a contact model considering rolling resistance is developed and implemented into PFC2D. Using this contact model, a series of numerical biaxial compression tests are carried out. The results of these numerical simulations show that rolling resistance has remarkable effects on shear strength and shear dilatancy of granular matters, and these trends are agreed with previous studies, which proves that this model works well. Then the effect of rolling resistance on anisotropy of granular matters is studied in this paper. It can be seen that rolling resistance has dramatic effect on the anisotropy of granular matters. The anisotropy of granular matters increases with rolling resistance.

Effect of Grain Size on Mechanical Properties of Dual Phase Steels Composed of Ferrite and Martensite

MRS Advances ◽  
2016 ◽  
Vol 1 (12) ◽  
pp. 811-816 ◽  
Author(s):  
Myeong-heom Park ◽  
Akinobu Shibata ◽  
Nobuhiro Tsuji
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
Tensile Test ◽  
Coarse Grained ◽  
Dual Phase ◽  
Fine Grained ◽  
Grain Sizes ◽  
Dp Structure ◽  
Dp Steels

ABSTRACTIt is well-known that dual phase (DP) steels composed of ferrite and martensite have good ductility and plasticity as well as high strength. Due to their excellent mechanical properties, DP steels are widely used in the industrial field. The mechanical properties of DP steels strongly depend on several factors such as fraction, distribution and grain size of each phase. In this study, the grain size effect on mechanical properties of DP steels was investigated. In order to obtain DP structures with different grain sizes, intercritical heat treatment in ferrite + austenite two-phase region was carried out for ferrite-pearlite structures having coarse and fine ferrite grain sizes. These ferrite-pearlite structures with coarse and fine grains were fabricated by two types of heat treatments; austenitizing heat treatment and repetitive heat treatment. Ferrite grain sizes of the specimens heat-treated by austenitizing and repetitive heat treatment were 47.5 µm (coarse grain) and 4.5 µm (fine grain), respectively. The ferrite grain sizes in the final DP structures fabricated from the coarse-grained and fine-grained ferrite-pearlite structures were 58.3 µm and 4.1µm, respectively. The mechanical behavior of the DP structures with different grain sizes was evaluated by an uniaxial tensile test at room temperature. The local strain distribution in the specimens during tensile test was obtained by a digital image correlation (DIC) technique. Results of the tensile test showed that the fine-grained DP structure had higher strength and larger elongation than the coarse-grained DP structure. It was found by the DIC analysis that the fine-grained DP structure showed homogeneous deformation compared with the coarse-grained DP structure.

Grain Size Effect on the Type VT1-0 Alloy Modified by Aluminum Ion Implantation

2015 ◽  
Vol 670 ◽  
pp. 144-151
Author(s):  
Irina Kurzina ◽  
Alisa Nikonenko ◽  
Natalja Popova ◽  
Elena L. Nikonenko ◽  
Mark Kalashnikov
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Ion Implantation ◽  
Size Effect ◽  
Phase State ◽  
Grain Size Effect ◽  
Significant Modification ◽  
Aluminum Ion ◽  
Grain Sizes ◽  
Aluminum Ions

The paper presents results of investigations of α-Ti microhardness modified by aluminum ions having diverse grain sizes, namely: 0.3 μm, 1.5 μm, and 17 μm. These investigations show that the decrease of the grain size and the additional ion implantation result in the significant modification of the structural and phase state of the alloy and its mechanical properties.

scholarly journals The effects of grain size and different multi-stage shearing techniques on shear strength along rock discontinuities

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Alina Vattai ◽  
Nikoletta Rozgonyi-Boissinot
Keyword(s):  
Grain Size ◽  
Shear Strength ◽  
Normal Stress ◽  
Friction Angle ◽  
Coarse Grained ◽  
Roughness Coefficient ◽  
Peak Friction Angle ◽  
Grain Sizes ◽  
Multi Stage ◽  
Study Laboratory

AbstractThe effects of grain size and different multi-stage shearing techniques on shear strength along discontinuities were analyzed in this study. Laboratory direct shear tests were carried out on plaster mortar with maximum grain sizes of 0.5 mm and 1.0 mm. All specimen surfaces were essentially similar, copied from the same natural, Hungarian coarse-grained sandstone joint with a low joint roughness coefficient (JRC = 8). Tests within two different normal stress ranges (σn = 0.25–0.5 and 0.5–1.5 MPa) were performed simultaneously. Specimens tested using the technique involving modified shearing with repositioning were sheared three times while being subjected to the same degree of normal stress (shearing sequence n = 1, 2, 3) and those with multi-stage technique without repositioning were subjected to shearing once at three different degrees of normal stress. The changing values of the peak friction angle calculated from the resulting peak shear strength-normal stress data pairs (τp − σn) were examined. Failure curves were estimated using linear regression, according to the Mohr–Coulomb failure criterion. The differences between the various peak friction angles obtained from experiments in which different multi-stage shearing techniques were used tend to increase in significance with the increasing number of shearing sequences. Peak friction angle values vary according to grain size of the material, though further investigations using more grain sizes are required to establish the extent of the effect on shear strength along discontinuities.

Effect of Grain Size and Grain Boundary on Mechanical Yielding Behavior of Fully Stabilized Zirconia

2006 ◽  
Author(s):  
Jie Lian ◽  
Javier Garay ◽  
Junlan Wang
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Grain Boundary ◽  
Boundary Effect ◽  
Coarse Grained ◽  
Stabilized Zirconia ◽  
Fine Grained ◽  
Grain Sizes ◽  
Reduced Modulus ◽  
Grain Boundary Effect

Mechanical properties of fully yttria stabilized zirconia (F-YSZ) with different grain sizes were investigated using instrumented indentation. While the grain size effect on the yield strength was performed on both the coarse-grained and fine-grained F-YSZ, the grain boundary effect was studied on the coarse-grained F-YSZ by performing nanoindentation within the grains and on/near the grain boundaries. Little variations were observed on mechanical properties such as hardness and reduced modulus, interesting results were obtained on the grain boundary effect on the yielding load for the course-grained F-YSZ.

Study on Mechanical Properties and Size Effect of Si3N4 Using Discrete Element Method

2009 ◽  
Vol 76-78 ◽  
pp. 719-724 ◽  
Author(s):  
Yuan Qiang Tan ◽  
Sheng Qiang Jiang ◽  
Cai Li ◽  
Dong Min Yang ◽  
Gao Feng Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Compressive Strength ◽  
Size Effect ◽  
Discrete Element Method ◽  
Bending Strength ◽  
Discrete Element ◽  
Poisson's Ratio ◽  
Simulation Results ◽  
Element Method

The mechanical models formed by packed circular discrete elements were used to investigate the mechanical properties of Si3N4. In these models, the distribution of elements is random in the specified region, and the average radius of elements is 6m. The main mechanical properties investigated here are Young’s modulus, compressive strength, Poisson’s ratio, fracture toughness and bending strength. Some numerical simulation analysis of the size effect of the mechanical properties in these discrete element models were carried out. The simulation results suggest that there is no obvious size effect for Young’s modulus, compressive strength and Poisson’s ratio in these discrete element models. However, for bending strength, when the number of elements in model is less than about 9000, there exists obvious size effect, with the increasing of the number of the elements, the size effect will become less and less until disappeared. The value of fracture toughness decreases with the increasing of the number of the model elements. The classical continuum fracture mechanics model about material fracture under tensile stress is also established by discrete element method. The simulation results are just the same as the simulation results of single edge notched bending (SENB) and the experimental values reported in other literatures. The results provide a more reliable foundation for the application of DEM in simulating the mechanical behaviors of advance ceramics.

The Effects of Grain Size and Lubrication on Micro Curl Forming Process of Metallic Thin Sheet

2015 ◽  
Vol 661 ◽  
pp. 55-61
Author(s):  
Chang Cheng Chen ◽  
Huey Lin Ho
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Size Effect ◽  
Deformation Behavior ◽  
Thin Sheet ◽  
Grain Size Effect ◽  
Forming Process ◽  
Grain Sizes ◽  
Different Temperatures ◽  
Different Thickness

This article aims at the discussion of deformation behavior considering size effect on curl forming process of sheet metal. In this study, the test specimens were made by phosphor bronze sheets for curl forming test. The specimens with different thickness were firstly heated at different temperatures for obtaining the objective grain sizes. And the mechanical properties of specimen were acquired by using tensile test. Through the curl forming test with a curl forming machine, the curled angles, springback and curling load were measured and analyzed for investigating the grain size effect of the chamfer and carbon lubricant during the curl forming process.

scholarly journals Investigation of Damage Evolution in Heterogeneous Rock Based on the Grain-Based Finite-Discrete Element Model

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3969
Author(s):  
Shirui Zhang ◽  
Shili Qiu ◽  
Pengfei Kou ◽  
Shaojun Li ◽  
Ping Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Tensile Strength ◽  
Grain Orientation ◽  
Damage Evolution ◽  
Discrete Element ◽  
Uniaxial Tensile ◽  
Tensile Cracks ◽  
Rock Heterogeneity ◽  
Heterogeneous Rock

Granite exhibits obvious meso-geometric heterogeneity. To study the influence of grain size and preferred grain orientation on the damage evolution and mechanical properties of granite, as well as to reveal the inner link between grain size‚ preferred orientation, uniaxial tensile strength (UTS) and damage evolution, a series of Brazilian splitting tests were carried out based on the combined finite-discrete element method (FDEM), grain-based model (GBM) and inverse Monte Carlo (IMC) algorithm. The main conclusions are as follows: (1) Mineral grain significantly influences the crack propagation paths, and the GBM can capture the location of fracture section more accurately than the conventional model. (2) Shear cracks occur near the loading area, while tensile and tensile-shear mixed cracks occur far from the loading area. The applied stress must overcome the tensile strength of the grain interface contacts. (3) The UTS and the ratio of the number of intergrain tensile cracks to the number of intragrain tensile cracks are negatively related to the grain size. (4) With the increase of the preferred grain orientation, the UTS presents a “V-shaped” characteristic distribution. (5) During the whole process of splitting simulation, shear microcracks play the dominant role in energy release; particularly, they occur in later stage. This novel framework, which can reveal the control mechanism of brittle rock heterogeneity on continuous-discontinuous trans-scale fracture process and microscopic rock behaviour, provides an effective technology and numerical analysis method for characterizing rock meso-structure. Accordingly, the research results can provide a useful reference for the prediction of heterogeneous rock mechanical properties and the stability control of engineering rock masses.

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