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displacement
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Modelling of localized plastic deformation via the adaptive mesh refinement
, Article International Journal of Nonlinear Sciences and Numerical Simulation ; Volume 4, Issue 1 , 2003 , Pages 31-45 ; 15651339 (ISSN) ; Gharehbaghi, S. A ; Sharif University of Technology
2003
Abstract
The capturing of localized plastic deformation in a Finite-element analysis is difficult as discontinuities of displacement occur and these are generally precluded in a standard displacement analysis. In this paper, an adaptive mixed finite element model is presented in the modelling of strain localization due to material instability. An h-adaptive analysis using element elongation is applied to study the prediction of localization phenomenon and evaluate the ultimate capacity of material. A remeshing strategy is employed to compute the distribution of required element size using the estimated error distribution. Once the new element size and its alignment have been indicated, an automated...
Measuring small displacements by using a capacitive transducer system
, Article Scientia Iranica ; Volume 7, Issue 1 , 2000 , Pages 69-74 ; 10263098 (ISSN) ; Sharif University of Technology
Sharif University of Technology
2000
Abstract
In this paper, application of a capacitive sensor system in recording small displacements is discussed. Through using a simple transducer and a monitoring circuit, change in capacitance has been detected as a function of the capacitor air-gap distance. There is a linear relation between gap distance and output of a sensor for a wide gap range of 0.5 to 5 mm. The reported system provides means for measuring displacements up to 5 mm with a resolution better than 250 nm. By decreasing the dynamic range of the transducer to 250 μm, a small displacement of the order of 100 nm is detectable. With the present system, a minimum displacement of about 200 nm (200 ppm) for the gap distance of 1 mm is...
Investigation of the microscopic displacement mechanisms and macroscopic behavior of alkaline flooding at different wettability conditions in shaly glass micromodels
, Article Journal of Petroleum Science and Engineering ; Vol. 122, issue , August , 2014 , pp. 595-615 ; ISSN: 09204105 ; Ghazanfari, M. H ; Sharif University of Technology
Abstract
Among various chemical methods, alkaline flooding has a great potential for enhancing heavy oil recovery, especially for reservoirs which contain acidic crude oil. However, fundamental understanding about microscopic displacement mechanisms and macroscopic behavior during alkaline floods at different wettabilities is not well understood, especially in five-spot shaly models. In this work several alkaline floods are performed on a glass micromodel containing randomly distributed shale streaks at different wettability conditions. Various mechanisms responsible for enhancing heavy oil recovery during alkaline flooding are investigated at different wettability conditions. These mechanisms...
Invasion percolation in presence of gravity
, Article Iranian Journal of Chemistry and Chemical Engineering ; Vol. 29, issue. 1 , 2010 , p. 71-82 ; ISSN: 10219986 ; Masihi, M ; Sharif University of Technology
Abstract
Simultaneous capillary dominated displacement of the wetting and non-wetting phases are processes of interest in many disciplines including modeling of the penetration of polluting liquids in hydrology or the secondary migration in petroleum reservoir engineering. Percolation models and in particular invasion percolation is well suited to characterize the slow immiscible displacement of two fluids when both the gravity and viscous effects are negligible. In particular, the characteristic of the percolating cluster and the other important percolation properties at the breakthrough can be inferred. However, with the inclusion of the gravity forces, the behavior may change. For example, as the...
A pore-level investigation of surfactant-crude oil displacements behavior in fractured porous media using one-quarter five spot micromodels
, Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Vol. 36, issue. 7 , April , 2014 , pp. 727-737 ; ISSN: 15567036 ; Rashtchian, D ; Ghazanfari, M. H ; Kharrat, R ; Sharif University of Technology
Abstract
Despite numerous studies, there is a lack of fundamental understanding about the displacement behavior of surfactant-crude oil systems under the influence of different fractures' geometrical properties in five-spot systems. In this work, a series of flow visualization experiments were carried out on one-quarter five spot glass micromodels at various fractures' geometrical properties, such as fracture density and fracture continuity, under oil-wet condition. The influences of injection of Linear Alkyl Benzene Sulfonate and Sodium Dodecyl Sulfate surfactants as well as the effect of fracture geometrical parameters, on macroscopic and microscopic displacement behavior have been investigated....
The effect of foundation uplift on elastic response of soil-structure systems
, Article International Journal of Civil Engineering ; Vol. 12, issue. 2 A , 2014 , p. 244-256 ; Ghannad, M. A ; Sharif University of Technology
Abstract
It is well-known that the behavior of soil-structure systems can be well described using a limited number of nondimensional parameters. This is the outcome of researches based on the premise that the foundation is bonded to the ground. Here, it is shown the concept can be extended to systems with foundation uplift. A set of non-dimensional parameters are introduced which controls the main features of uplifting systems. The effect of foundation uplift on response of soil-structure systems are investigated parametrically through time history analysis for a wide range of systems subjected to ground motions recorded on different soil types. In particular, the effects of uplift on displacement...
Aspects of alkaline flooding: Oil recovery improvement and displacement mechanisms
, Article Middle East Journal of Scientific Research ; Volume 18, Issue 2 , 2013 , Pages 258-263 ; 19909233 (ISSN) ; Ahadi, A ; Kordnejad, M ; Borazjani, Z ; Sharif University of Technology
2013
Abstract
Alkaline flooding is one of the newest chemical enhanced oil recovery (EOR) methods. Alkaline generates in situ surfactants when in reacts with acid content of the oil. This economic surfactant generated in oil-water interface, reduces interfacial tension (IFT) significantly that leads to increase in oil recovery by extracting oil from tiny pores. In this study, three alkaline i.e. Na2CO3, NaOH and KOH in various concentrations were flooded in a glassy micromodel to detect displacement mechanisms and compare oil recovery. According to the results, increase in alkaline concentration leads to increase in recovery. However, in this case, alkaline type does not play a significant role. In...
Theoretical and experimental investigation of transformer winding fault detection using comparison of transfer function coefficients
, Article Transactions on Electrical Engineering, Electronics, and Communications ; Volume 10, Issue 1 , 2012 , Pages 10-16 ; 16859545 (ISSN) ; Vakilian, M ; Rahimpour, E ; Azizian, D ; Sharif University of Technology
2012
Abstract
In this work, a new model of transformer winding is developed. The components in the model are determined by the geometric and electric data of the winding (detailed model) and using experimental data based on genetic algorithm. Under different degrees of axial displacement and radial deformation in the winding, the circuit parameters of the model will change and thus the equivalent circuit characteristics will be influenced. After acquiring the model parameters in the intact and faulted cases, transfer function coefficients are derived in model using nodal analysis. Subsequently, introducing a new index based on these coefficients, the type and extent of penetration of the fault in the...
Arrangements of shear walls in control of lateral displacement of concrete frames
, Article World Applied Sciences Journal ; Volume 17, Issue 10 , 2012 , Pages 1324-1330 ; 18184952 (ISSN) ; Rahemi, L ; Rahmani, K ; Peroti, S ; Sharif University of Technology
2012
Abstract
One of the major shortcomings of conventional and rather high-rise structures is increasing lateral displacements arising from lateral forces which finally make the entire project un-economical. In this research, effort has been made to investigate the effect of shear walls arrangements on the lateral displacement of the structure. Two types of structures including 16 and 32-storeys frameswith different arrangements of shear panels were examined. The findings indicate that compared to other frames, the performance of frame no. 1 in both types of structures was poor in controlling the overall displacement of structure. Furthermore, more number of shear panels are not necessarily effective in...
Micro-model experimental study of fracture geometrical effect on breakthrough time in miscible displacement process
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 30, Issue 3 , 2011 , Pages 1-7 ; 10219986 (ISSN) ; Rashtchian, D ; Shadizadeh, S. R ; Sharif University of Technology
2011
Abstract
The miscible displacement process appears to be an increasingly feasible method for the extraction of oil from depleted reservoirs. However, there is a lack of fundamental understanding of how fracture geometrical characteristics impact the oil recovery efficiency in this type of enhanced oil recovery technique. In this work, a series of experimental tests were conducted whereby the n-Heptane as a solvent displaced n-Decane in the glass micro-models having different fracture geometries. It has been observed that the breakthrough time is decreased with increasing the fractures' length. In contrast, breakthrough time is increased when increasing the fractures orientation angle related to flow...
Invasion percolation in presence of gravity
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 29, Issue 1 , 2010 , Pages 71-82 ; 10219986 (ISSN) ; Masihi, M ; Sharif University of Technology
2010
Abstract
Simultaneous capillary dominated displacement of the wetting and non-wetting phases are processes of interest in many disciplines including modeling of the penetration of polluting liquids in hydrology or the secondary migration in petroleum reservoir engineering. Percolation models and in particular invasion percolation is well suited to characterize the slow immiscible displacement of two fluids when both the gravity and viscous effects are negligible. In particular, the characteristic of the percolating cluster and the other important percolation properties at the breakthrough can be inferred. However, with the inclusion of the gravity forces, the behavior may change. For example, as the...
The contribution of the medial retinaculum and quadriceps muscles to patellar lateral stability - An in-vitro study
, Article Knee ; Volume 11, Issue 2 , 2004 , Pages 89-94 ; 09680160 (ISSN) ; Tahmasbi, M. N ; Amis, A ; Sharif University of Technology
2004
Abstract
Patellofemoral joint stability is a result of the restraining effects of the quadriceps muscles, the retinacular structures, and engagement of the bones. The role and significance of these mechanisms in restraining patellar lateral displacement was investigated in this study by measuring the force needed to cause 5 mm lateral displacement (i.e. the mechanical stability, or 'stabilising force') of the patella. Six cadaver knees had 175 N quadriceps load distributed among three muscle groups. With a force ratio matching the muscles physiological cross sectional areas, no significant change occurred in the patellar stabilising force between 0 and 60°knee flexion, but a significant increase...
H-adaptive finite element analysis for localization phenomena with reference to metal powder forming
, Article Finite Elements in Analysis and Design ; Volume 38, Issue 6 , 2002 , Pages 503-519 ; 0168874X (ISSN) ; Lewis, R. W ; Sharif University of Technology
2002
Abstract
Standard finite element models, i.e. finite element methods that use standard constitutive models, suffer from excessive mesh dependence when strain-softening models are used in numerical analyses and cannot reproduce the size effect commonly observed in quasi-brittle failure. In this paper, an h-adaptive analysis for the mixed finite element solution of solid mechanics problems is presented with special reference to metal powder forming involving localization due to material instability. A remeshing strategy is employed to compute the distribution of required element size using the estimated error distribution. The numerical results are obtained for a Von-Mises yield criterion applied to a...
Formation of ZrC-WC-W Composites Ceramics by DCP Method and Investigation of Their Physical Properties, Phase Composition and Microstructure
, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali (Supervisor) ; Mirhabibi, Ali Reza (Supervisor)
Abstract
Refractory metals (W,Re,Ta,Mo,Nb) and their alloys can exhibit exceptional properties at elevated temperatures. However, refectory metals tend to be relatively heavy and, in some cases, can be relatively difficult to form in complex shapes at low cost. Light composites of refractory metals with high-melting ceramics, which can be fabricated into dense, near net shapes at low temperatures, would be particularly attractive for advanced aerospace applications. In this project, WC powders have been pressed and shaped to cylindrical preforms. Secondly, these performs have been sintered slightly(presintered) into porous, rigid ones with about 50% open porosity. Finally, in order to reach dense...
Providing Smooth Design Spectra for Iran by Modifying the Newmark Method
, M.Sc. Thesis Sharif University of Technology ; Alijani Moghaddam, Hassan (Supervisor)
Abstract
Many regulations around the world use the Newmark method, directly or indirectly, in the design spectrum. Research on the Newmark design spectrum shows that this spectrum sometimes significantly differs from the earthquakes response spectra that have occurred; therefore, it is necessary to develop and introduce new design spectra by modifying the Newmark method to be more compatible with reality. The developed design spectra in seismic regulations around the world are directly affected by the records involved in their development. Thus, the appropriate design spectrum should be prepared based on the seismic characteristics of the faults of each country. Evaluation of the Iranian Seismic...
Application of base-line correction methods to obtain permanent displacements of a near-source ground motion: The 2003 bam earthquake
, Article Journal of Earthquake Engineering ; Volume 13, Issue 3 , 2009 , Pages 313-327 ; 13632469 (ISSN) ; Khatam, H ; Farahi Jahromi, H ; Sharif University of Technology
2009
Abstract
In this article, two base-line correction methods for correcting the near-source strong motions were studied on the near-source recording of the 2003, Bam earthquake. To obtain permanent ground displacements at Bam station, two methods were applied with some modifications and without using any kind of filtering. Even though it is difficult to calculate true permanent displacements from data attained by present accelerograms, the results of this study show that the rational limit of permanent ground displacements can be successfully achieved by rational choosing of effective parameters. In addition, it is observed that some pre-processing steps suggested in literature have no considerable...
Rock joint modeling using a visco-plastic multilaminate model at constant normal load condition
, Article Geotechnical and Geological Engineering ; Volume 24, Issue 5 , 2006 , Pages 1449-1468 ; 09603182 (ISSN) ; Sadaghiani, M. H ; Pak, A ; Saleh, Y ; Sharif University of Technology
2006
Abstract
Rock joints play an important role in the behavior of rock masses under normal and shear loading conditions. Numerical simulation of the behavior of jointed rock masses is not an easy task due to complexities involved in the problem such as joint roughness, joint shear strength, hardening and softening phenomenon and mesh dependency. In this study for modeling purposes, a visco-plastic multilaminate model considering hardening and softening effects has been employed. For providing the necessary data for numerical simulation, a series of laboratory experiments have been carried out on regular tooth-shape asperities made by gypsum, under constant normal load conditions. Shear stress-shear...
Comparison of two triple-fiber sensor designs for small distance measurements
, Article Microwave and Optical Technology Letters ; Vol. 56, issue. 9 , JUN , 2014 , pp. 1997-2001 ; ISSN: 08952477 ; Sharif University of Technology
Abstract
Operation of two different optical fiber sensor designs for distance measurements with a good sensitivity, resolution, and wide dynamic range is reported. Design is based on the intensity modulation due to reflectance measurement from a target surface. Two reported designs are fabricated with a triple-fiber assembly, in which one uses a double-transmitter, while another one uses a double-receiver fiber design. Reflection signals from different targets are tested with these sensors and results for the mirror and A4 paper surfaces are described. The response curve for both experiments starts from a near zero level, shows a maximum at a certain distance and gradually drops to the background...
Assessing the shear behavior of oriented rock joints under constant normal loading conditions
, Article Geotechnical Special Publication ; February , 2014 , p. 553-562 ; Khosravi, M ; Sadaghiani, M. H ; Meehan, C. L ; Amini, E ; Sharif University of Technology
Abstract
This paper presents results from a series of constant normal load direct shear tests on artificially created rock joints, in an attempt to quantify the effects of different factors that contribute to the shear strength along "ideal" rock joints. Particular focus is given to the effect of asperity orientation with respect to the direction of shearing. In many historical rock joint shear strength criteria, the effect of a joint's roughness on the joint shear strength is described based on analysis of only a single profile in the direction of shearing. More recent studies have observed that the distribution of sheared area on a joint surface during shear is significantly affected by the...
Displacement and stress constrained topology optimization
, Article Proceedings of the ASME Design Engineering Technical Conference, Portland, OR ; Volume 2 A , August , 2013 ; 9780791855850 (ISBN) ; Suresh, K ; Sharif University of Technology
American Society of Mechanical Engineers
2013
Abstract
The objective of this paper is to demonstrate a topology optimization method subject to displacement and stress constraints. The method does not rely on pseudo-densities; instead it exploits the concept of topological level-set where 'partial' elements are avoided. Consequently: (1) the stresses are well-defined at all points within the evolving topology, and (2) the finite-element analysis is robust and efficient. Further, in the proposed method, a series of topologies of decreasing volume fractions are generated in a single optimization run. The method is illustrated through numerical experiments in 2D