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thermal-expansion
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Application of a Thermo-Plastic Constitutive Model for Coupled THM Analysis of Behavior of Saturated Soils
, M.Sc. Thesis Sharif University of Technology ; Pak, Ali (Supervisor)
Abstract
Effects of temperature on the behavior of soils and rocks have been studied widely in recent years. Following the need for understanding the effects of temperature on the behavior of clayey soils, several experimental and numerical studies on thermo-mechanical behavior of clayey soils have been carried out and a number of thermo-mechanical constitutive models have been developed for saturated and unsaturated clayey soils. In this research, a two-yield surface thermo-plastic constitutive model developed by Abuel-Naga et al. (2007, 2009), has been chosen for THM analysis of the behavior of saturated clayey soils. This constitutive model is based on Modified Cam-Clay (MCC) model. The MCC model...
Performance of Unbonded Post-Tensioned Concrete Slab Subjected to Temperature Variations
, M.Sc. Thesis Sharif University of Technology ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
Tests have shown that concrete post-tensioned slab under heat condition suffer a significant reduction in stiffness and strength. Design and implementation of post-tensioned concrete slabs with large spans of industrial structures exposed to extreme variation in temperature can be possible with detailed research on its behavior under heating condition. In this study numerical modelling of PT concrete slabs with unbonded tendons under heating condition was created based on available test results in the literature. A parametric study has been carried out and the results are presented for concrete coefficient thermal expansion, thermal contact conductance between the concrete and the cables,...
The Effect of Cobalt on Thermal Expansion and Metallurgical Properties of LM13 Alloy
, M.Sc. Thesis Sharif University of Technology ; Varahram, Naser (Supervisor)
Abstract
LM13 Aluminum alloys contain Silicon, Copper, magnesium and Nickel. This alloys have been widely used in automobile pistons. For this application thermal expansion coefficient is one important characteristics other than mechanical properties. In this project replacing Cobalt with Nickel to improve alloy thermal and mechanical properties in piston applications by different cobalt contents. Cobalt contents is 0, 0.15, 0.55 and 0.77 Wt%. Because of oxidation magnesium content decrease into 0.98, 0.74, 0.61 and 0.48 Wt%. Thermal expansion coefficient and UTS first increase and after 0.55 Cobalt Wt% show decrease But yield strength and hardness increase as cobalt content increase. Microscopic...
Soil-structure Interaction in Geothermal Foundations
, M.Sc. Thesis Sharif University of Technology ; Khosravi, Ali (Supervisor)
Abstract
Regarding the issue that significant amount of energy consumption in the world is dedicated to heating and cooling of the buildings, by using traditional methods of heating and cooling, the environment is facing serious problems like green house gases. There were various techniques for decreasing the amount of contaminants stem from this process. Heat-exchanger energy piles are one of the most common methods that will result in economic usage of energy resources. Assessing the long-term behavior of the energy piles requires comprehensive understanding of the complex interaction between soil and pile subjected to mechanical and thermal loadings. Several numerical and analytical methods have...
Using molecular dynamic simulation data of calcite in a wide pressure range to calculate some of its thermodynamic properties via some universal equations of state
, Article Molecular Physics ; Volume 106, Issue 21-23 , 2008 , Pages 2545-2556 ; 00268976 (ISSN) ; Shokouhi, M ; Parsafar, G. A ; Sharif University of Technology
2008
Abstract
Molecular dynamics, MD, simulation of calcite (CaCO3) is selected to compare the p-v-T behaviour of some universal equations of state, UEOS, for the temperature range 100 K ≤ T 800 ≤ K, and pressures up to 3000 kbar. The isothermal sets of p-v-T data generated by simulation were each fitted onto some three- and two-parameter EOSs including Parsafar and Mason (PM), Linear Isotherm Regularity (LIR), Birch-Murnaghan (BM), Shanker, Vinet, Baonza and Modified generalized Lennard-Jones (MGLJ) EOSs. It is found that the MD data satisfactorily fit these UEOS with reasonable precision. Some features for a good UEOS criteria such as temperature dependencies of coefficients, pressure deviation,...
Unsaturated thermal consolidation around a heat source
, Article Computers and Geotechnics ; Volume 134 , 2021 ; 0266352X (ISSN) ; Ghasemi Fare, O ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Thermal loadings in saturated (two-phase) clays induce excess pore water pressure due to the difference in the thermal expansion coefficient of the pore volume and the pore water. The gradual dissipation of the excess pore water pressure causes thermal volume reduction which is known as thermal consolidation. However, thermal consolidation in a three-phase soil system such as unsaturated soil is more sophisticated. In this paper, an analytical model for thermal consolidation around a heat source embedded in unsaturated clay or in calyey soils containing two immiscible fluids is developed based on the effective stress concept. Governing equations, including energy, mass, and momentum balance...
Thermo-mechanical modeling of high speed spindles
, Article Scientia Iranica ; Volume 19, Issue 2 , 2012 , Pages 282-293 ; 10263098 (ISSN) ; Movahhedy, M. R ; Sharif University of Technology
2012
Abstract
Prediction of the thermo-mechanical behavior of machine-tool spindles is essential in the reliable operation of high speed machine tools. In particular, the performance of these high speed spindles is dependent on their thermal behavior. The main source of heat generation in the spindle is the friction torque in angular contact ball bearings. This paper presents an effort to develop a comprehensive model of high speed spindles that includes viable models for the mechanical and thermal behavior of its major components, i.e., bearings, shaft and housing. Spindle housing and shaft are treated as six-degree-of-freedom Timoshenko beam elements. Bearings are modeled as two-node elements with five...
Thermo-hydro-mechanical modeling of fracturing porous media with two-phase fluid flow using X-FEM technique
, Article International Journal for Numerical and Analytical Methods in Geomechanics ; Volume 44, Issue 18 , October , 2020 , Pages 2430-2472 ; Mortazavi, S. M. S ; Sharif University of Technology
John Wiley and Sons Ltd
2020
Abstract
In this paper, a fully coupled thermo-hydro-mechanical model is presented for two-phase fluid flow and heat transfer in fractured/fracturing porous media using the extended finite element method. In the fractured porous medium, the traction, heat, and mass transfer between the fracture space and the surrounding media are coupled. The wetting and nonwetting fluid phases are water and gas, which are assumed to be immiscible, and no phase-change is considered. The system of coupled equations consists of the linear momentum balance of solid phase, wetting and nonwetting fluid continuities, and thermal energy conservation. The main variables used to solve the system of equations are solid phase...
Thermoelastic fields of a functionally graded coated lnhomogeneity with sliding/perfect interlaces
, Article Journal of Applied Mechanics, Transactions ASME ; Volume 74, Issue 3 , 2007 , Pages 389-398 ; 00218936 (ISSN) ; Shodja, H. M ; Sharif University of Technology
2007
Abstract
The determination of the thermo-mechanical stress field in and around a spherical/ cylindrical inhomogeneity surrounded by a functionally graded (FG) coating, which in turn is embedded in an infinite medium, is of interest. The present work, in the frame work of Boussinesq/Papkovich-Neuber displacement potentials method, discovers the potential functions by which not only the relevant boundary value problems (BVPs) in the literature, but also the more complex problem of the coated inhomogeneities with FG coating and sliding interfaces can be treated in a unified manner. The thermo-elastic fields pertinent to the inhomogeneities with multiple homogeneous coatings and various combinations of...
Thermal stresses and kinetics of phase transformation on the run-out table after hot strip rolling of low-carbon steels
, Article International Journal of Advanced Manufacturing Technology ; Volume 83, Issue 9-12 , 2016 , Pages 1725-1736 ; 02683768 (ISSN) ; Serajzadeh, S ; Sharif University of Technology
Abstract
A thermo-elastic analysis coupled with a phase change model is employed to evaluate thermal stresses as well as progress of austenite decomposition after hot strip rolling operations. The thermo-mechanical finite element analysis is utilized to assess the distributions of temperature and thermal stresses during cooling while at the same time, a model based on the additivity rule is used to determine the rate of austenite to ferrite decomposition. The proposed model is applicable to multi-pass rolling schedules while the effects of different process parameters including the rolling speed and cooling configuration of the run-out table can be taken into account. In order to verify the...
Thermal residual stresses in silicon thin film solar cells under operational cyclic thermal loading: A finite element analysis
, Article Solar Energy ; Volume 135 , 2016 , Pages 366-373 ; 0038092X (ISSN) ; Dehghany, M ; Sohrabpour, S ; Naghdabadi, R ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
In manufacturing amorphous silicon solar cells, thin films are deposited at high temperatures (200-400 °C) on a thick substrate using sputtering and plasma enhanced chemical vapor deposition (PECVD) methods. Since the thin films and substrate have different thermal expansion coefficients, cooling the system from deposition temperature to room temperature induces thermal residual stresses in both the films and substrate. In addition, these stresses, especially those having been induced in the amorphous silicon layer can change the carrier mobility and band gap energy of the silicon and consequently affect the solar cell efficiency. In this paper, a 2D finite element model is proposed to...
Thermal buckling responses of a graphene reinforced composite micropanel structure
, Article International Journal of Applied Mechanics ; Volume 12, Issue 1 , 2020 ; Aliakbarlou, H ; Jebeli, M ; Noormohammadiarani, O ; Habibi, M ; Safarpour, H ; Foong, L. K ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2020
Abstract
This is the first research on the thermal buckling analysis of graphene nanoplatelets reinforced composite (GPLRC) doubly curved open cylindrical micropanel in the framework of numerical-based two-dimensional generalized differential quadrature method (2D-GDQM). Additionally, the small-scale effects are analyzed based on nonlocal strain gradient theory (NSGT). The stresses and strains are obtained using the high-order shear deformable theory (HOSDT). The rule of mixture is employed to obtain varying thermal expansion, and Poisson's ratio, while module of elasticity is computed by modified Halpin-Tsai model. In addition, nonlinear temperature changes along the GPLRC micropanel's thickness...
Thermal buckling analysis of bridged single walled carbon nanotubes using molecular structural mechanics
, Article Journal of Applied Physics ; Volume 117, Issue 11 , 2015 ; 00218979 (ISSN) ; Badri Kouhi, E ; Sharif University of Technology
American Institute of Physics Inc
2015
Abstract
This paper is concerned with the stability analysis of bridged single walled carbon nanotubes (SWCNT) under temperature changes. A molecular structural mechanics model is utilized to investigate the free vibration frequencies and thermal buckling of SWCNT. In comparison with most of the previous studies, a temperature-variable thermal-expansion-coefficient is used that is negative under a certain temperature. Also thermal variation of Young's modulus of the CNTs is considered. Several studies are performed to investigate the critical temperature change due to heating and cooling of SWCNTs with different chiralities and slenderness ratios and the stability boundaries are determined
The effect of nano-TiO2 additions on the densification and mechanical properties of SiC-matrix composite
, Article Ceramics International ; Volume 46, Issue 5 , April , 2020 , Pages 6477-6483 ; Yaghobizadeh, O ; Baharvandi, H. R ; Alipour Shahraki, A ; Mohammadi, H ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
This research studied the effect of adding TiO2 nanoparticles along with Al2O3 and Y2O3 additives on the physical and mechanical properties of a SiC-matrix composite. The samples were fabricated through a pressureless process at 1900 °C. The results showed that the addition of TiO2 nanoparticles up to 4.5 wt% inhibited the excessive growth of SiC grains. According to the investigations, the microstructure and final properties of composites were affected by density, synthesized phases as well as their distribution in the matrix, and grain size. The highest density, Young's modulus, hardness, indentation fracture resistance, and flexural strength, alongside with the lowest brittleness index...
The critical voltage of a GPL-reinforced composite microdisk covered with piezoelectric layer
, Article Engineering with Computers ; 2020 ; Ebrahimi, F ; Elianddy Bin Supeni, E ; Habibi, M ; Safarpour, H ; Sharif University of Technology
Springer
2020
Abstract
In this research, electrically characteristics of a graphene nanoplatelet (GPL)-reinforced composite (GPLRC) microdisk are explored using generalized differential quadrature method. Also, the current microstructure is coupled with a piezoelectric actuator (PIAC). The extended form of Halpin–Tsai micromechanics is used to acquire the elasticity of the structure, whereas the variation of thermal expansion, Poisson’s ratio, and density through the thickness direction is determined by the rule of mixtures. Hamilton’s principle is implemented to establish governing equations and associated boundary conditions of the GPLRC microdisk joint with PIAC. The compatibility conditions are satisfied by...
The critical voltage of a GPL-reinforced composite microdisk covered with piezoelectric layer
, Article Engineering with Computers ; Volume 37, Issue 4 , 2021 , Pages 3489-3508 ; 01770667 (ISSN) ; Ebrahimi, F ; Elianddy Bin Supeni, E ; Habibi, M ; Safarpour, H ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
In this research, electrically characteristics of a graphene nanoplatelet (GPL)-reinforced composite (GPLRC) microdisk are explored using generalized differential quadrature method. Also, the current microstructure is coupled with a piezoelectric actuator (PIAC). The extended form of Halpin–Tsai micromechanics is used to acquire the elasticity of the structure, whereas the variation of thermal expansion, Poisson’s ratio, and density through the thickness direction is determined by the rule of mixtures. Hamilton’s principle is implemented to establish governing equations and associated boundary conditions of the GPLRC microdisk joint with PIAC. The compatibility conditions are satisfied by...
Temperature and thickness effects on thermal and mechanical stresses of rotating FG-disks
, Article Journal of Mechanical Science and Technology ; Volume 25, Issue 3 , 2011 , Pages 827-836 ; 1738494X (ISSN) ; Azadi, M ; Sharif University of Technology
Abstract
In the present paper, radial and hoop thermal and mechanical stress analysis of a rotating disk made of functionally graded material (FGM) with variable thickness is carried out by using finite element method (FEM). To model the disk by FEM, one-dimensional two-degree elements with three nodes are used. It is assumed that the material properties, such as elastic modulus, Poisson's ratio and thermal expansion coefficient, are considered to vary using a power law function in the radial direction. The geometrical and boundary conditions are in the shape of two models including thermal stress (model-A) and mechanical stress (model-B). In model-A there exists no pressure in both external and...
Stress analysis of multilayer thin walled pipes with circular cut-outs
, Article World Congress on Engineering 2016, WCE 2016, 29 June 2016 through 1 July 2016 ; Volume 2224 , 2016 , Pages 1146-1150 ; 20780958 (ISSN); 9789881404800 (ISBN) ; Bull, J.W ; Chizari, M ; Ao S.I ; Ao S.I ; Gelman L ; Ao S.I ; Gelman L ; Hukins D.W.L ; Hunter A ; Korsunsky A.M ; et al.; IAENG Society of Artificial Intelligence; IAENG Society of Bioinformatics; IAENG Society of Computer Science; IAENG Society of Data Mining; IAENG Society of Electrical Engineering ; Sharif University of Technology
Newswood Limited
2016
Abstract
A finite element analysis of a double layered shell with a circular hole is carried out with the computer aided engineering software Abaqus (Dassault Systèmes, FR). The model proposed has been used to perform a stress analysis on three pipes with different sized hole. Moreover, thermal expansion has been implemented in the testing. For the purpose of the research, the elastic properties of the materials have been considered and the results compared with the ones previously published in literature. The outcome of the investigation will benefit towards the design of optimal and sustainable pipes with circular cut outs
Relief of edge effects in bi-adhesive composite joints
, Article Composites Part B: Engineering ; Volume 108 , 2017 , Pages 153-163 ; 13598368 (ISSN) ; Tahani, M ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
Three-dimensional thermo-mechanical stress analysis of composite joints with bi-adhesive bonding is presented using the full layerwise theory. Based on three-dimensional elasticity theory, sets of fully coupled governing differential equations are derived using the principle of minimum total potential energy and are simultaneously solved using the state space approach. Results show that bi-adhesive bonding substantially relieves the edge effects. Moreover, series of parametric studies reveal the nonlinear effects of bonding length ratio and the relative stiffness and coefficient of thermal expansion of the mid- and side-adhesives. It is also concluded that the optimum design of a bi-adhesive...
Pressureless sintering of 3Y-TZP/stainless-steel composite layers
, Article Journal of the American Ceramic Society ; Volume 91, Issue 11 , 2008 , Pages 3493-3503 ; 00027820 (ISSN) ; Simchi, A ; Tamjid Shabestary, E ; Hartwig, T ; Sharif University of Technology
2008
Abstract
A pressureless sintering method was utilized to fabricate metal/ceramic joints out of yttria-stabilized zirconia (3Y-TZP) and stainless steels (SS). Ultrafine (150 nm) and nanoscale (75 nm) 3Y-TZP particles and micrometric 17-4PH, 316L, and 420 SS (<31 μm) powders were tested. Isothermal and nonisothermal sintering behaviors of the powders and composite layers in hydrogen, argon, and vacuum atmospheres were examined. It was found that the mismatch strain between the zirconia ceramic and SS during cosintering is significant, which leads to bond cracking and joint failure. Nevertheless, interlayer diffusion of Zr, Fe, and Cr and the formation of a reaction zone, particularly during vacuum...