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thermal-gradients
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A critical state constitutive model for the isotropic thermal compression of structured sand–bentonite buffers
, Article Indian Geotechnical Journal ; Volume 49, Issue 4 , 2019 , Pages 398-408 ; 09719555 (ISSN) ; Karimi, A. H ; Hamidi, A ; Ahmadi, M. M ; Sharif University of Technology
Springer
2019
Abstract
The sand–bentonite mixture is used as the buffer layer in nuclear waste disposals. The buffer layer, as a non-permeable protective layer, is generally exposed to temperature gradients and the long-term subjection to temperature results in creep and more intact structure for the layer. In the present study, thermally induced structure and its effects on the isotropic compression behavior and volume change behavior of buffer layer are evaluated. Thermal consolidation tests were conducted using a modified triaxial cell capable of handling temperatures up to 90 °C. In order to investigate the effects of thermal gradients on the behavior of the mixture, saturated specimens were cured at constant...
Fatigue properties of temperature gradient transient liquid phase diffusion bonded Al7075-T6 alloy
, Article Transactions of Nonferrous Metals Society of China (English Edition) ; Volume 25, Issue 4 , April , 2015 , Pages 1073-1079 ; 10036326 (ISSN) ; Ekrami, A ; Farahany, S ; Jahangiri, A ; Sharif University of Technology
Nonferrous Metals Society of China
2015
Abstract
Abstract Fatigue properties of Al7075-T6 alloy joined by temperature gradient transient liquid phase (TGTLP) diffusion bonding using liquid gallium interlayer was investigated. The fatigue specimen was jointed at 460 °C under 10 MPa pressure for 10 min. The TLP bonded samples were homogenized at 465 °C for 2 h and then T6-heat treated. The fatigue life of Al7075-T6 alloy was determined as 107 cycles under 90 MPa while the fatigue life of TLP bonded sample under this stress amplitude was 1.2×106 cycles, which is about 10% of the total Al7075 alloy fatigue life. The fatigue fracture surfaces of Al7075 sample and TGTLP bonded sample were studied using scanning electron microscope to...
Computational simulation of marangoni convection under microgravity condition
, Article Scientia Iranica ; Volume 16, Issue 6 B , 2009 , Pages 513-524 ; 10263098 (ISSN) ; Taeibi Rahni, M ; Asadi, B ; Ahmadi, G ; Sharif University of Technology
2009
Abstract
In this work, the rising of a single bubble in a quiescent liquid under microgravity condition was simulated. In addition to general studies of microgravity effects, the initiation of hydrodynamic convection, solely due to the variations of interface curvature (surface tension force) and thus the generation of shearing forces at the interfaces, was also studied. Then, the variation of surface tension due to the temperature gradient (Marangoni convection), which can initiate the onset of convection even in the absence of buoyancy, was studied. The related unsteady incompressible full Navier-Stokes equations were solved using a finite difference method with a structured staggered grid. The...
Frequency characteristics of FG-GPLRC viscoelastic thick annular plate with the aid of GDQM
, Article Thin-Walled Structures ; Volume 150 , 2020 ; Ghabussi, A ; Ebrahimi, F ; Habibi, M ; Safarpour, H ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
This is the first research on the free vibration analysis of functionally graded graphene platelets reinforced composite (FG-GPLRC) viscoelastic annular plate resting on the visco-Pasternak foundation and subjected to the nonlinear temperature gradient and mechanical loading within the framework of higher-order shear deformation theory (HSDT). Hamilton's principle is employed to establish governing equations within the framework of HSDT. In this paper, viscoelastic properties are modeled according to Kelvin-Voigt viscoelasticity. The deflection as the function of time can be solved by the fourth-order Runge-Kutta numerical method. Generalized differential quadrature method (GDQM) is applied...
On the nonlinear dynamics of a multi-scale hybrid nanocomposite disk
, Article Engineering with Computers ; 2020 ; Ebrahimi, F ; Habibi, M ; Safarpour, H ; Sharif University of Technology
Springer
2020
Abstract
This is the first research on the nonlinear frequency analysis of a multi-scale hybrid nanocomposite (MHC) disk (MHCD) resting on an elastic foundation subjected to nonlinear temperature gradient and mechanical loading is investigated. The matrix material is reinforced with carbon nanotubes (CNTs) or carbon fibers (CF) at the nano- or macroscale, respectively. We present a modified Halpin–Tsai model to predict the effective properties of the MHCD. The displacement–strain of nonlinear vibration of multi-scale laminated disk via third-order shear deformation theory (TSDT) and using Von Karman nonlinear shell theory is obtained. Hamilton’s principle is employed to establish the governing...
On the nonlinear dynamics of a multi-scale hybrid nanocomposite disk
, Article Engineering with Computers ; Volume 37, Issue 3 , 2021 , Pages 2369-2388 ; 01770667 (ISSN) ; Ebrahimi, F ; Habibi, M ; Safarpour, H ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
This is the first research on the nonlinear frequency analysis of a multi-scale hybrid nanocomposite (MHC) disk (MHCD) resting on an elastic foundation subjected to nonlinear temperature gradient and mechanical loading is investigated. The matrix material is reinforced with carbon nanotubes (CNTs) or carbon fibers (CF) at the nano- or macroscale, respectively. We present a modified Halpin–Tsai model to predict the effective properties of the MHCD. The displacement–strain of nonlinear vibration of multi-scale laminated disk via third-order shear deformation theory (TSDT) and using Von Karman nonlinear shell theory is obtained. Hamilton’s principle is employed to establish the governing...
Coke formation possibility during production of reducing gas in large scale direct reduction plant
, Article Ironmaking and Steelmaking ; Volume 34, Issue 2 , 2007 , Pages 115-123 ; 03019233 (ISSN) ; Vakhshouri, K ; Hashemi, M. M. Y. M ; Sharif University of Technology
2007
Abstract
For the production of synthesis gas utilised in Midrex direct reduction plants, catalytic steam/CO2 hydrocarbon reforming in tubular reformer is the major process. Owing to the high heat input through the Midrex reformer tube wall, the endothermic nature of reforming reactions, low mass velocity of feed gas and large tube diameter, the catalyst bed is exposed to considerable axial and radial temperature gradients. These radial concentration and temperature gradients may create local areas with potential for carbon formation. To investigate this phenomenon, a rigorous two-dimensional model is developed for simulating the operation of a Midrex reformer which applies a dual catalyst loading...
The Effects of Various Parameters on Wellbore Stability During Drilling Through Shale Formations
, Article Petroleum Science and Technology ; Volume 33, Issue 12 , 2015 , Pages 1275-1285 ; 10916466 (ISSN) ; Ghotbi, C ; Pishvaie, M. R ; Sharif University of Technology
Taylor and Francis Inc
2015
Abstract
Field evidence indicates that the thermal and chemical regimes in wellbore considerably affect the wellbore stability. This study presents a general coupled model for transport of solute, solvent and heat including their combined effects on the wellbore stability. Optimization of drilling fluid parameters is crucial for wellbore stability analysis particularly in high pressure-high temperature environments. The coupled effects of chemical potential and temperature gradients on fluid flow significantly change the pore pressure and stress around a borehole. The effects of various parameters such as mud weight, solute concentration gradient, shale properties, and temperature gradient on...
Analysis of Al A359/SiCp functionally graded cylinder subjected to internal pressure and temperature gradient with elastic-plastic deformation
, Article Journal of Thermal Stresses ; Volume 34, Issue 10 , May , 2011 , Pages 1054-1070 ; 01495739 (ISSN) ; Naghdabadi, R ; Arghavani, J ; Sharif University of Technology
2011
Abstract
In this article, an analytical elastic-plastic solution for thick-walled cylinders made of Functionally Graded Materials (FGMs) subjected to internal pressure and thermal loading is presented. Based on the experimental results, a mathematical model to predict the yielding through the thickness of FG AlA359/SiCp cylinder is developed. It is shown that under the temperature gradient loading, there is a point in the cylinder where the circumferential stress changes from compressive to tensile. The position of this point depends on the geometry and material properties of the FG cylinder and is independent of the temperature gradient
Microstructure and mechanical properties of pure Cu interlayer TLP joints of 304 stainless steel to dual phase steel
, Article Journal of Materials Processing Technology ; Volume 275 , January , 2020 ; Ekrami, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Bonding was carried out at 1150 °C for holding times of 60 and 90 min followed by water quenching. At the bonding time of 60 min, Cu remained at the bond region resulting in an unstable liquid/solid interface with a sinusoidal microstructure. Isothermal solidification completed at the holding time of 90 min. Unidirectional solidification was observed from the stainless steel side toward the low carbon manganese steel and abnormal grain growth of stainless steel was seen at the bond region due to temperature gradient which originated from different electrical properties of the parent alloys. Joints made at the bonding time of 90 min were homogenized at 730 °C for 75 min and quenched in water...
Computational analysis of ground effects on the dynamical behavior of unconfined two-phase clouds in view of detonability studies
, Article Scientia Iranica ; Volume 12, Issue 4 , 2005 , Pages 414-425 ; 10263098 (ISSN) ; Doustdar, M. M ; Hosseinalipour, M ; Sharif University of Technology
Sharif University of Technology
2005
Abstract
A numerical analysis has been performed to investigate the ground effects on the main parameters of a two-phase unconfined cloud of fuel and air to study its detonability. Equivalence ratio, turbulence intensity, cloud shape and volume, uniformity, temperature gradient and delay time distribution are the most important factors that affect the detonability of a vapor cloud. The effects of the altitude of the dispersing device from the ground on these significant factors have been demonstrated. A modified KIVA-based program has been employed to carry out the computations. A finite volume method is used to solve the equations describing the gas phase. A discrete particle technique is applied to...
An efficient scanning algorithm for improving accuracy based on minimising part warping in selected laser sintering process
, Article Virtual and Physical Prototyping ; Volume 14, Issue 1 , 2019 , Pages 59-78 ; 17452759 (ISSN) ; Movahhedy, M. R ; Khodaygan, S ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
In the selective laser sintering (SLS) method, layers of powder are scanned by a laser beam and sintered. The thermal gradients created by laser heating and the subsequent cooling of the sintered sections results in thermal stresses and part warping in the final part. Thermal gradients are dependent on the scanning algorithm, in particular, the scan vector length. In this work, an efficient scanning algorithm for the SLS process is presented with the aim to minimise the part warping in the final part due to thermally induced residual stresses, while maintaining the production time at a minimum. The proposed algorithm is implemented in a finite element simulation and scanning parameters...
Directed motion of C60 on a graphene sheet subjected to a temperature gradient
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 83, Issue 4 , 2011 ; 15393755 (ISSN) ; Neek Amal, M ; Ejtehadi, M. R ; Sharif University of Technology
Abstract
Nonequilibrium molecular dynamics simulations are used to study the motion of a C60 molecule on a graphene sheet subjected to a temperature gradient. The C60 molecule is actuated and moves along the system while it just randomly dances along the perpendicular direction. Increasing the temperature gradient increases the directed velocity of C60. It is found that the free energy decreases as the C60 molecule moves toward the cold end. The driving mechanism based on the temperature gradient suggests the construction of nanoscale graphene-based motors
Conventional vs. temperature-gradient transient liquid phase bonding of stainless steel 304 using a multi-component (Fe–Ni–Mo–B) filler metal
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 53, Issue 11 , 2022 , Pages 4081-4100 ; 10735623 (ISSN) ; Ekrami, A ; Sharif University of Technology
Springer
2022
Abstract
The application of the multi-component Fe-based filler metals (FMs) for transient liquid phase (TLP) bonding of AISI 304 austenitic stainless steel has been overshadowed by dissimilar interlayers merely due to their shorter isothermal solidification time. However, the latter usually suffers from low efficiency in terms of mechanical properties even after homogenization of heat treatment. This study shows that by imposing a temperature gradient across the bond line during the TLP bonding process (TG-TLP), it is possible to reduce the isothermal solidification time significantly. This renews the interest in utilizing multi-component Fe-based FMs. In this regard, the TG-TLP bonding process was...
High gradient temperature thermo-buoyant flow in a square cavity with magnetoconvection using a novel non-boussinesq algorithm
, Article Numerical Heat Transfer; Part A: Applications ; Volume 64, Issue 3 , 2013 , Pages 255-272 ; 10407782 (ISSN) ; Hajibagheri, M ; Heidarnataj, M ; Darbandi, M ; Javaherdeh, K ; Sharif University of Technology
2013
Abstract
We study numerically the heat transfer of steady laminar flow in a square cavity filled with electrically conducting fluids, in the presence of an external uniform magnetic field. Imposing a large temperature gradient between two opposite vertical walls, there are substantial temperature and density variations in the domain. The fluid is treated as an ideal gas. Indeed, high temperature gradient thermo-buoyant cavity flows result in natural convection flow domains with high Rayleigh number. To implement the temperature variation effect, the fluid properties, including the conductivity and viscosity coefficients, are considered to vary with temperature in accordance to the Sutherland's law....
Experimental and simulation investigation on separation of binary hydrocarbon mixture by thermogravitational column
, Article Journal of Molecular Liquids ; Volume 268 , 2018 , Pages 791-806 ; 01677322 (ISSN) ; Karimi Sabet, J ; Motahari, K ; Mahruz Monfared, S ; Amini, Y ; Moosavian, M. A ; Sharif University of Technology
Elsevier B.V
2018
Abstract
In this article, experimental and numerical investigations are performed to study a thermogravitational column (TGC) for the separation of toluene/n-heptane mixture. This research has tried to determine the main significant parameters and their effects on the performance of the process. In experimental examinations, the influence of the main parameters such as feed flow rate, cut and temperature gradient on the performance of the TGC efficiency is studied. In addition, computational fluid dynamics is used to simulate the separation process in this review. The response surface methodology (RSM) was also applied to minimize the number of runs and investigate the optimum operating conditions....
Effect of solidification mechanism on microstructure and mechanical properties of joint in TLP bonded Al2024-T6 alloy
, Article Science and Technology of Welding and Joining ; Volume 16, Issue 2 , Nov , 2011 , Pages 174-180 ; 13621718 (ISSN) ; Ekrami, A ; Kokabi, A. H ; Sharif University of Technology
2011
Abstract
Transient liquid phase (TLP) bonding of Al2024-T6 alloy, using gallium (Ga) interlayer, has been investigated. Bonding process was carried out at 470°C for 6 min, and homogenising temperature and time were 495°C and 2 h respectively. Conventional TLP bonding using Ga interlayer was not an appropriate method for joining of Al2024. In this method, the boundary between two Al2024 specimens was not fully eliminated during bonding because of solidification with planar front. In addition, bonding zone was depleted of copper, and as a result, tensile and shear strength of joint decreased to 200 and 110 MPa respectively. TLP bonding under temperature gradient offered very good results in bonding of...
Boundary identification between LBLOCA and SBLOCA based on stratification and temperature gradient in two-phase PTS
, Article Annals of Nuclear Energy ; Volume 115 , May , 2018 , Pages 430-441 ; 03064549 (ISSN) ; Ghofrani, M. B ; D'Auria, F ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Temperature gradient on the thick Reactor Pressure Vessel (RPV), caused by sudden overcooling events, especially in the downcomer, would intensify the propagation of structural defects. This situation known as Pressurized Thermal Shock (PTS) could be created in case of Emergency Core Cooling System (ECCS) actuation which leads to injection of cold water into the cold leg of the primary loop in some accidents, e.g. Loss Of Coolant Accident (LOCA). Prediction of Plant response to LOCA and water temperature gradient in the downcomer are performed in thermal-hydraulic section of PTS analysis. Employment of system codes is one of the proposed procedures in literature to obtain plant response and...
Prediction of solidification behaviour of weld pool through modelling of heat transfer and fluid flow during gas tungsten arc welding of commercial pure aluminium
, Article Materials Science and Technology ; Volume 24, Issue 12 , 2008 , Pages 1427-1432 ; 02670836 (ISSN) ; Serajzadeh, S ; Kokabi, A. H ; Sharif University of Technology
2008
Abstract
A mathematical model is developed to assess the solidification behaviour of the weld pools. To do so, during gas tungsten arc welding of commercial pure aluminium, equations of conversation of mass, energy and momentum are numerically solved considering three-dimensional steady state heat transfer and fluid flow conditions. The weld pool geometry, weld thermal cycles and various solidification parameters are calculated using temperature and velocity fields acquiring from the utilised model. The solidification behaviour of the weld pool at the weld centreline and the fusion line is then studied using the solidification parameters including temperature gradient G, solidification rate R and the...
Design of spherical vessels under steady-state thermal loading using thermo-elasto-plastic concept
, Article International Journal of Pressure Vessels and Piping ; Volume 86, Issue 2-3 , 2009 , Pages 143-152 ; 03080161 (ISSN) ; Kargarnovin, M. H ; Naghdabadi, R ; Sharif University of Technology
2009
Abstract
Governing equilibrium equations of thick-walled spherical vessels made of material following linear strain hardening and subjected to a steady-state radial temperature gradient using elasto-plastic analysis are derived. By considering a maximum plastic radius and using the concept of thermal autofrettage for the strengthening mechanism, the optimum wall thickness of the vessel for a given temperature gradient across the wall thickness is obtained. Finally, in the case of thermal loading on a vessel, the effect of convective heat transfer on the optimum thickness is studied and a general formula for the optimum wall thickness and design graphs for several different cases are presented. © 2008...