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    The effect of aging on the fracture characteristics and ductility of self-compacting concrete

    , Article Materials and Design ; Volume 55 , March 2014 , Pages 937-948 Beygi, M. H. A ; Kazemi, M. T ; Nikbin, I. M ; Vaseghi Amiri, J ; Sharif University of Technology
    Abstract
    Good knowledge of fracture parameters and cracking behavior of self-compacting concrete (SCC) from early ages until the SCC becomes mature plays an important role in design of SCC structure and also in evaluation of durability and consequently prevention of damage. In this paper, variation of fracture parameters and corresponding ductility behavior of SCC at different ages (e.g. 3days, 7days, 28days and 90days) for SCC mixes with w/c ratios of 0.45 and 0.65 have been experimentally studied. To do so, three-point bending tests were carried out on 120 notched beams. Then, size effect method (SEM) and work of fracture method (WFM) were applied to interpret the results. The results of analyses... 

    Effect of fracture spacing on VAPEX performance in heavy oil fracture systems

    , Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 27, Issue 1 , 2008 , Pages 35-45 ; 10219986 (ISSN) Azin, R ; Kharrat, R ; Ghotbi, C ; Vossoughi, S ; Sharif University of Technology
    2008
    Abstract
    The vapor extraction (VAPEX) process; a solvent-based enhanced oil recovery process has been found promising for some heavy oil reservoirs. In this work, the VAPEX process is studied using a compositional simulator on a number of single-block and multiple block fractured systems. PVT data of one of an Iranian heavy oil reservoir are used to tune the equation of state. Effects of fracture spacing on the performance of process were studied. It was found that the fracture network enhances the VAPEX process in low-permeability systems by increasing the contact area between solvent and oil contained in the matrix blocks. Also, the fracture network reduced the instabilities in the system pressure... 

    Immiscible Displacement of a Wetting Fluid by a Non-wetting One at High Capillary Number in a Micro-model Containing a Single Fracture

    , Article Transport in Porous Media ; Volume 94, Issue 1 , 2012 , Pages 289-301 ; 01693913 (ISSN) Kamari, E ; Rashtchian, D ; Shadizadeh, S. R ; Sharif University of Technology
    Abstract
    Most reservoirs in Iran are heterogeneous fractured carbonate reservoirs. Heterogeneity causes an earlier breakthrough and an unstable front which leads to a lower recovery. A series of experiments were conducted whereby the distilled water displaced n-Decane in strongly oil-wet glass micro-models containing a single fracture. Experimental data from image analysis of immiscible displacement processes are used to modify the Buckley-Leverett and fractional flow equations by a heterogeneity factor. It is shown that the heterogeneity factor in the modified equations can be expressed as a function of fracture length and orientation  

    Descriptive epidemiology of traumatic injuries in 18890 adults: A 5-year-study in a tertiary trauma center in Iran

    , Article Asian Journal of Sports Medicine ; Volume 6, Issue 1 , 2015 ; 2008000X (ISSN) Mehrpour, S. R ; Nabian, M. H ; Oryadi Zanjani, L ; Foroughmand Araabi, M. H ; Shahryar Kamrani, R ; Sharif University of Technology
    Abstract
    Background: Basic epidemiological data can provide estimates when discussing disease burden and in the planning and provision of healthcare strategies. There is little quantitative information in the literature regarding prevalence of traumatic injuries from developing countries. Objectives: The aim of the current preliminary study was to reveal the prevalence and age and gender distribution of various traumatic injuries in a tertiary referral orthopedic hospital in Iran. Patients and Methods: In a prospective descriptive study, all traumatic injured patients attending the Orthopedic Trauma Unit of our center in a five year period were included. Demographic details, the cause of injury,... 

    Hybrid PP-EPR-GF composites. Part II: Fracture mechanisms

    , Article Plastics, Rubber and Composites ; Volume 32, Issue 10 , 2003 , Pages 439-444 ; 14658011 (ISSN) Zebarjad, S. M ; Bagheri, R ; Lazzeri, A ; Sharif University of Technology
    2003
    Abstract
    The fracture mechanism of hybrid iPP-EPR-GF composites has been studied by notched Charpy, three- and four-point bending fracture tests. The results of impact tests illustrate that increasing both temperature and EPR/GF ratio increases the impact energy of iPP-EPR-GF. Indeed, with increasing temperature, a brittle, ductile, transition temperature (BDTT) occurs. The results of a three-point bending test show that fracture toughness (KIC) can be improved by addition of both GF and EPR. Since the trend in the fracture toughness values is close to what would be expected by the rule of blends, it can be concluded that the use of both GF and EPR has no significant synergistic effect on toughening.... 

    Fracture behaviour of isotactic polypropylene under static loading condition

    , Article Materials and Design ; Volume 24, Issue 2 , 2003 , Pages 105-109 ; 02641275 (ISSN) Zebarjad, S. M ; Bagheri, R ; Lazzeri, A ; Serajzadeh, S ; Sharif University of Technology
    Elsevier Ltd  2003
    Abstract
    The fracture mechanism of isotactic polypropylene has been studied by three- and four-point bending tests. The result of three-point bending test shows that a wide spread damage zone is present in front of the notch. Looking in more detail via cross-polarised light shows the evidence of birefringence in the stress-whitened zone. Increasing the applied load causes it to spread out the stress-whitened zone. Then the craze-like features are nucleated inside the stress-whitened region. The result of four-point bending test shows that craze-like damage appears in front of pre-crack and its propagation is dictated by spherulite microstructure. © 2003 Elsevier Science Ltd. All rights reserved  

    The role of microstructure in mechanical behaviors of low-alloy sintered steels

    , Article Scientia Iranica ; Volume 7, Issue 1 , 2000 , Pages 41-49 ; 10263098 (ISSN) Yoozbashizadeh, H ; Simchi, A ; Moradkhani, D ; Ashtari, M ; Khorsand, H ; Davami, P ; Sharif University of Technology
    Sharif University of Technology  2000
    Abstract
    In this study, microstructural aspects that control fracture and deformation resistance of P/M materials are evaluated. Several low-alloy steels were produced under both experimental and commercial conditions for achieving different matrix phases and porosity levels with varying shape factors. A 'porosity map' was constructed and used for a quantified study of the dominant mechanism controlling mechanical behaviors. The role of inclusion gathering and secondary pores, as well as sintering mechanism and alloying method is considered and discussed. The mechanism assessment was performed by using microstructure examination through optical and scanning electron microscopy. The results... 

    Improvement of fractional flow model for miscible displacement process: An experimental investigation in single fractured porous medium

    , Article Journal of Porous Media ; Volume 16, Issue 3 , 2013 , Pages 255-266 ; 1091028X (ISSN) Kamari, E ; Shadizadeh, S. R ; Rashtchian, D ; Sharif University of Technology
    2013
    Abstract
    Most of the reservoirs in Iran are heterogeneous fractured carbonate reservoirs. Heterogeneity causes an earlier breakthrough and an unstable front, which leads to a lower recovery. In this study, a series of experiments was conducted whereby the n-Heptane displaced n-Decane in glass micromodels having different fracture geometries. Experimental data from image analysis of miscible displacement processes are used to modify the fractional flow equations by a heterogeneity factor. It is shown that the heterogeneity factor in the modified equations can be expressed as a function of fracture length and orientation  

    Modeling of cohesive crack growth in partially saturated porous media; A study on the permeability of cohesive fracture

    , Article International Journal of Fracture ; Volume 167, Issue 1 , Jan , 2011 , Pages 15-31 ; 03769429 (ISSN) Barani, O. R ; Khoei, A. R ; Mofid, M ; Sharif University of Technology
    Abstract
    Modeling the water flow in cohesive fracture is a fundamental issue in the crack growth simulation of cracked concrete gravity dams and hydraulic fracture problems. In this paper, a mathematical model is presented for the analysis of fracture propagation in the semi-saturated porous media. The solid behavior incorporates a discrete cohesive fracture model, coupled with the flow in porous media through the fracture network. The double-nodded zero-thickness cohesive interface element is employed for the mixed mode fracture behavior in tension and contact behavior in compression. The modified crack permeability is applied in fracture propagation based on the data obtained from experimental... 

    3D modeling of cohesive crack growth in partially saturated porous media: A parametric study

    , Article Engineering Fracture Mechanics ; Vol. 124-125, issue , 2014 , pp. 272-286 ; ISSN: 00137944 Barani, O. R ; Khoei, A. R ; Sharif University of Technology
    Abstract
    In this paper, the 3D cohesive crack propagation is presented in partially saturated porous media. The double-nodded zero-thickness cohesive interface elements are employed to capture the mixed mode fracture behavior. In order to describe the behavior of fractured media, two balance equations are applied similar to those employed for the mixture of solid-fluid phase in semi-saturated media, including: the momentum balance of fractured media, and the balance of fluid mass within the fracture. Crack permeability is modified based on the data obtained from experimental results to consider the roughness of fracture walls effect  

    Determination of the fracture parameters of concrete with improved wedge-splitting testing

    , Article Engineering Fracture Mechanics ; Volume 276 , 2022 ; 00137944 (ISSN) Sun, L ; Du, C ; Ghaemian, M ; Zhao, W ; Sharif University of Technology
    Elsevier Ltd  2022
    Abstract
    Considering the quasi-brittle mechanical properties of concrete, wedge-splitting tests are employed and improved in this paper to study the fracture behaviour of concrete. A novel wedge-splitting device is designed by fixing ten springs on the force transmission component. The adaptive spring force can be imposed on top of a concrete specimen to retard the brittle fracture process. With the proposed wedge-splitting test design for notched cuboid specimens, the complete load–strain/CMOD curves of concrete can be generated directly. The fracture toughness and the fracture energy can be calculated easily without numerical fitting using the double-K fracture model. The descending branch of the... 

    Effect of coarse aggregate volume on fracture behavior of self compacting concrete

    , Article Construction and Building Materials ; Volume 52 , 15 February , 2014 , Pages 137-145 ; ISSN: 09500618 Nikbin, I. M ; Beygi, M. H. A ; Kazemi, M. T ; Vaseghi Amiri, J ; Rahmani, E ; Rabbanifar, S ; Eslami, M ; Sharif University of Technology
    Abstract
    This paper presents the effect of volume of coarse aggregate on fracture characteristics of self- compacting concrete (SCC). Based on an experimental programme, a series of three point bending tests were carried out on 58 notched beams. SCC was prepared with coarse aggregate in varying percentages of 30%, 40%, 50% and 60% (as the percentage of the total aggregate volume). For all mixes, the fracture parameters were analyzed by the work-of- fracture method (WFM) and by the size effect method (SEM) to obtain a suitable correlation between these methods which is used to calibrate fracture numerical models. The results showed that with decrease of volume of coarse aggregate from 60% to 30% in... 

    The effect of water to cement ratio on fracture parameters and brittleness of self-compacting concrete

    , Article Materials and Design ; Volume 50 , 2013 , Pages 267-276 ; 02613069 (ISSN) Beygi, M. H. A ; Kazemi, M. T ; Nikbin, I. M ; Amiri, J. V ; Sharif University of Technology
    Elsevier Ltd  2013
    Abstract
    The paper describes an experimental research on fracture characteristics of self-compacting concrete (SCC). Three point bending tests conducted on 154 notched beams with different water to cement (w/c) ratios. The specimens were made from mixes with various w/c ratios from 0.7 to 0.35. For all mixes, common fracture parameters were determined using two different methods, the work-of-fracture method (WFM) and the size effect method (SEM). Test results showed that with decrease of w/c ratio from 0.7 to 0.35 in SCC: (a) the fracture toughness increases linearly: (b) the brittleness number is approximately doubled: (c) the effective size of the process zone cf in SEM and the characteristic... 

    Effect of environmental conditions on fracture behavior of solder joints

    , Article Theoretical and Applied Fracture Mechanics ; Volume 112 , 2021 ; 01678442 (ISSN) Honarvar, S ; Nourani, A ; Karimi, M ; Sharif University of Technology
    Elsevier B.V  2021
    Abstract
    Double cantilever beam (DCB) specimens were prepared according to standard surface mount technology (SMT). The samples were stored inside an environmental chamber at two different relative humidity values (i.e. 40 or 100%) for either 2 or 4 h. Then they were aged at 25 °C, 75 °C or 125℃ for the same time. Finally, after being cooled to room temperature, fracture tests were performed under mode-I loading conditions at a strain rate of 0.03 s−1 at room temperature. Storage time did not have a significant effect on the fracture behavior. The fracture load and energy of the solder joints decreased significantly when the temperature was increased from 25 to 75℃. By further increase in the... 

    Characterization of fracture dynamic parameters to simulate naturally fractured reservoirs

    , Article International Petroleum Technology Conference, IPTC 2008, Kuala Lumpur, 3 December 2008 through 5 December 2008 ; Volume 1 , 2008 , Pages 473-485 ; 9781605609546 (ISBN) Bahrami, H ; Siavoshi, J ; Parvizi, H ; Esmaili, S ; Karimi, M. H ; Nasiri, A ; Sharif University of Technology
    2008
    Abstract
    Fractures identification is essential during exploration, drilling and well completion of naturally fractured reservoirs since they have a significant impact on flow contribution. There are different methods to characterize these systems based on formation properties and fluid flow behaviour such as logging and testing. Pressure-transient testing has long been recognized as a reservoir characterization tool. Although welltest analysis is a recommended technique for fracture evaluation, but its use is still not well understood. Analysis of pressure transient data provides dynamic reservoir properties such as average permeability, fracture storativity and fracture conductivity.An infusion of... 

    Monitoring and characterizing the finger patterns developed by miscible displacement in fractured heavy oil systems

    , Article Industrial and Engineering Chemistry Research ; Volume 52, Issue 31 , July , 2013 , Pages 10853-10863 ; 08885885 (ISSN) Shokrollahi, A ; Majidi, S. M. J ; Ghazanfari, M. H ; Sharif University of Technology
    2013
    Abstract
    This work concerns experimentally quantifying finger behavior during miscible displacements in fractured porous media. A series of miscible tests were performed on five-spot fractured micromodels which were initially saturated with heavy crude oil, and the developed finger patterns were quantified using an image analysis technique. The results revealed that the numbers of macro fingers formed is well correlated with the square root of dimensionless time, while the rate of finger initiation is independent of fracture characteristics. The level of bypassed oil linearly decreases with dimensionless distance traveled by front precisely. The transient fractal dimension behavior experiences a... 

    Application of the recovery curve method for evaluation of matrix-fracture interactions

    , Article Journal of Natural Gas Science and Engineering ; Volume 22 , January , 2015 , Pages 447-458 ; 18755100 (ISSN) Ghaedi, M ; Masihi, M ; Heinemann, Z. E ; Ghazanfari, M. H ; Sharif University of Technology
    Elsevier  2015
    Abstract
    The Discrete Fracture Network and Dual Continuum concept are two common methods to model naturally fractured reservoirs. Each has specific limitations. The newly introduced recovery curve method is believed to be a compromise between these two current methods. In the recovery curve method, two recovery curves for water and gas displacements are used to more realistically calculate matrix-fracture mass exchanges. This paper presents a new approach to determine appropriate recovery curves by using the recovery curve method and production data. In particular, two recovery curves were determined for a column model by matching phase contact positions throughout the production data. Hybrid genetic... 

    Simulation analysis of the effects of fractures' geometrical properties on the performance of vapour extraction process

    , Article Journal of Canadian Petroleum Technology ; Volume 49, Issue 7 , 2010 , Pages 47-59 ; 00219487 (ISSN) Fatemi, S. M ; Bahonar, M ; Sharif University of Technology
    2010
    Abstract
    Vapour extraction (VAPEX), a newly developed heavy oil recoveiy (HOR) method, has been extensively studied, both theoretically and experimentally, in conventional sandstone models. However, the applicability of this process to naturally fractured reservoirs has not yet been addressed. The objective of this work is to evaluate the effects of fractures' geometrical properties, such as orientation, length of extension, discontinuity in both the upper well region (UWR) and the far well region (FWR) and vertical fracture location on VAPEX performance. Additionally, the effects of horizontal and vertical fracture dispersion in various density, dispersion scheme and networking on the performance of... 

    Modeling of capillary pressure in horizontal rough-walled fractures in the presence of liquid bridges

    , Article Journal of Petroleum Science and Engineering ; Volume 185 , 2020 Harimi, B ; Ghazanfari, M. H ; Masihi, M ; Sharif University of Technology
    Elsevier B.V  2020
    Abstract
    Capillary continuity between adjacent matrix blocks through formation of liquid bridge controls the recovery factor of gravity drainage process in fractured reservoirs. However, stability of liquid bridges as well as related capillary pressure in horizontal rough fractures is not well discussed in the available literature. In this work, new models of rough-walled fracture are developed and the role of roughness size and frequency on formation of liquid bridge and fracture capillary pressure are investigated. The Young-Laplace equation is numerically solved to characterize the liquid bridge formed in the proposed models of rough fractures. Critical fracture aperture for a range of liquid... 

    Mechanical and thermal properties of montmorillonite-epoxy nanocomposite

    , Article International Journal of Modern Physics B ; Volume 22, Issue 18-19 , 2008 , Pages 3247-3253 ; 02179792 (ISSN) Marouf, B. T ; Bagheri, R ; Pearson, R. A ; Sharif University of Technology
    World Scientific Publishing Co. Pte Ltd  2008
    Abstract
    In this investigation, the mechanical and thermal properties of the montmorillonite-epoxy nanocomposites were studied. The epoxy compounds were prepared by in situ polymerization and the intercalation dispersion were obtained as evidenced using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results reveal remarkable stiffening effect and slight toughening effect of the MMT in the epoxy resin and an insight about the crack tip and notch tip toughening mechanism. According to the DMA, the glass transition temperature increases as increasing the MMT content. © 2008 World Scientific Publishing Company