Ali Fakhimi
Tarbiat Modares University
Ultimate tensile strengthDigital image correlationPileGeologyEngineeringBrittlenessComposite materialDiscrete element methodGeotechnical engineeringMaterials scienceSofteningDirect shear testFracture (geology)Numerical analysisComputer simulationMechanicsFracture mechanicsCohesion (geology)SpallStructural engineeringThree point flexural testShear (geology)Rock mechanics
70Publications
18H-index
1,057Citations
Publications 47
Newest
#1Mohammad Reza Majedi (TMU: Tarbiat Modares University)H-Index: 1
#2Mohammad Afrazi (TMU: Tarbiat Modares University)H-Index: 3
Last. Ali Fakhimi (TMU: Tarbiat Modares University)H-Index: 18
view all 3 authors...
Quasi-brittle materials such as rock are rate sensitive materials and their behaviour under dynamic loading is not identical with that under static loading. In this study, numerical Brazilian tensile tests are conducted using a Split Hopkinson Pressure Bar system in an attempt to reproduce the dynamic increase factors (DIF) of the experimental tests. The rock is modelled by a bonded particle system made of spherical particles which interact at the contact points. The numerical results indicate t...
4 CitationsSource
#1Fatemeh Molaei (New Mexico Institute of Mining and Technology)
#1Fatemeh Molaei (New Mexico Institute of Mining and Technology)H-Index: 4
Last. Ali Fakhimi (New Mexico Institute of Mining and Technology)H-Index: 18
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#1Qing Lin (China University of Petroleum)H-Index: 11
#2Bin Wan (China University of Petroleum)H-Index: 3
Last. Ali Fakhimi (TMU: Tarbiat Modares University)H-Index: 18
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Abstract Crack initiation and propagation in rock involve the development of a nonlinear zone around the crack tip called fracture process zone. The existence of fracture process zone influences the fracture behavior and therefore it must be carefully investigated. This zone is normally idealized as a cohesive zone whose mechanical properties are difficult to measure. In this study, a relatively simple approach is proposed to identify the properties of the cohesive zone and the length of the coh...
8 CitationsSource
#1Ali Fakhimi (TMU: Tarbiat Modares University)H-Index: 18
#2Siavash Norouzi (New Mexico Institute of Mining and Technology)H-Index: 4
A model that allows micromechanical parameters to soften as a measure of plastic deformation is discussed. In particular, a microdilation angle is involved to help for calibration of macroscopic volumetric deformation. Through biaxial and shear tests numerical simulations, it is shown that macrodilation angle of bonded particle system can be controlled only when small particles are used. The genesis pressure that causes small overlap of particles has an impact on dilation angle as well and can b...
Source
#1Ali Fakhimi (New Mexico Institute of Mining and Technology)H-Index: 18
#2P. Azhdari (New Mexico Institute of Mining and Technology)H-Index: 1
Last. J. Kimberley (New Mexico Institute of Mining and Technology)H-Index: 1
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Abstract Split Hopkinson Pressure Bar (SHPB) testing was used to evaluate the strength characteristics of sandstone under uniaxial compressive loading. The physical results suggest that rock strength increases under dynamic loading. A hybrid bonded particle-finite element model was used for numerical simulation of SHPB tests. A parameter called rock strength enhancement coefficient was introduced which is multiplied by the relative velocity of particles at the contact points to increase the bond...
12 CitationsSource
#1Mohammad Hajiazizi (Razi University)H-Index: 6
#2Moslem Bavali (Razi University)H-Index: 1
Last. Ali Fakhimi (New Mexico Institute of Mining and Technology)H-Index: 18
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The stability of a soil slope, reinforced by a concrete pile, is studied both experimentally and numerically in this work. Our study suggests that when the concrete pile is located in the middle of the slope (at x/r = 0.5), the soil structure collapses under a pressure of 10.9 kPa that is the highest overburden pressure to cause instability of the tested reinforced sandy slope. However, when the pile is located in the upslope (at x/r = 0.75) or downslope (at x/r = 0.25), the slope failure occurs...
10 CitationsSource
#1Ali Fakhimi (TMU: Tarbiat Modares University)H-Index: 18
#2Qing Lin (China University of Petroleum)H-Index: 11
Last. Joseph F. Labuz (UMN: University of Minnesota)H-Index: 32
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Abstract Rock fracture and the induced displacement field are investigated through physical and numerical experiments. A Berea sandstone specimen with a central notch was tested in three-point bending. Digital image correlation (DIC) was used to obtain the displacement patterns as the fracture initiated and propagated. The DIC results clearly show the development of a damage zone and displacement discontinuity along the center line of the beam at peak load. It is suggested that a traction-free o...
20 CitationsSource
#1Siavash Norouzi (New Mexico Institute of Mining and Technology)H-Index: 4
#2Ali Fakhimi (New Mexico Institute of Mining and Technology)H-Index: 18
#1Ali Fakhimi (New Mexico Institute of Mining and Technology)H-Index: 18
#2Ali Tarokh (UMN: University of Minnesota)H-Index: 8
Last. Joseph F. LabuzH-Index: 32
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Abstract A three point bending fracture test was performed on a typical quasi-brittle material (Berea sandstone). The loading was continued into the post-peak region where crack growth was visible along the center line of the beam. Subsequent inspection of a portion of the specimen showed that part of the fracture offered no resistance to loading – a cohesionless crack existed. Digital image correlation was used to study the nature of the displacement discontinuity associated with the cohesionle...
13 CitationsSource
#1Ali Tarokh (UMN: University of Minnesota)H-Index: 8
#2Roman Y. Makhnenko (UIUC: University of Illinois at Urbana–Champaign)H-Index: 12
Last. Joseph F. Labuz (UMN: University of Minnesota)H-Index: 32
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The zone of microcracks surrounding a notch tip—the process zone—is a phenomenon observed in fracture of quasi-brittle materials, and the characterization of the process zone is the topic of the paper. Specimens of different sizes with a center notch fabricated from a granite of large grain (Rockville granite, average grain size of 10 mm), were tested in three-point bending. Acoustic emissions were recorded and locations of microcracks were determined up to peak load. The results show that both ...
19 CitationsSource