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thermal-stresses
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Mechanical and thermal stresses in a functionally graded hollow cylinder due to radially symmetric loads
, Article International Journal of Pressure Vessels and Piping ; Volume 79, Issue 7 , 2002 , Pages 493-497 ; 03080161 (ISSN) ; Sohrabpour, S ; Eslami, M. R ; Sharif University of Technology
2002
Abstract
In this paper, a general analysis of one-dimensional steady-state thermal stresses in a hollow thick cylinder made of functionally graded material is developed. The temperature distribution is assumed to be a function of radius, with general thermal and mechanical boundary conditions along the inside and outside surfaces. The material properties, except Poisson's ratio, are assumed to depend on variable the r and they are expressed as power functions of r. The direct method is used to solve the heat conduction and Navier equations. © 2002 Elsevier Science Ltd. All rights reserved
Electrothermal simulation of barium titanate based PTCR thermistor
, Article Materials Science and Engineering B: Solid-State Materials for Advanced Technology ; Volume 133, Issue 1-3 , 2006 , Pages 157-166 ; 09215107 (ISSN) ; Nemati, Z. A ; Sharif University of Technology
2006
Abstract
PTCR thermistors are thermally sensitive resistors that show positive temperature coefficient of resistance and are good candidates for applications as self-regulating heating elements and thermal control switches. For these applications, the current-time behavior of thermistors is of primary importance. In this work, heat transfer models were developed to simulate the electrothermal behavior of BaTiO3 thermistors. Also, using simulated temperature profiles, thermal stress distributions of the specimen were calculated to predict crack formation at different conditions. At high voltages, the effects of thermal conductivity and heat transfer coefficient were negligible. At low voltages, the...
Thermal Fatigue Investigation of Different Geometrical Aspect of via in Integrated Circuits
, M.Sc. Thesis Sharif University of Technology ; Adib Nazari, Saeid (Supervisor)
Abstract
The reliability of integrated circuits (IC) is related to material imperfections such as holes, cavities, cracks and etc. which occur in the manufacturing process. The operational conditions of IC create thermal stresses. These thermal stresses increase the chance of failure by making the imperfections critical in IC’s components such as VIA that is used as connection between interconnects in the multilevel integrated circuits. As a result, thermal fatigue needs to be investigated in VIA thoroughly.
The thermal stresses in VIA increase the possibility of hole forming due to hydrostatic stresses during manufacturing process and the amplitude of applied stresses under the operational...
The thermal stresses in VIA increase the possibility of hole forming due to hydrostatic stresses during manufacturing process and the amplitude of applied stresses under the operational...
Offshore accidents and effects on their performances
, Article Ocean '04 - MTS/IEEE Techno-Ocean '04: Bridges across the Oceans - Conference Proceedings, Kobe, 9 November 2004 through 12 November 2004 ; Volume 1 , 2004 , Pages 212-217 ; 0780386698 (ISBN) ; Hemati, P ; Sharif University of Technology
2004
Abstract
Marine accidents are some of the risk sources on human life at sea and also make the founded budget to be sank to the deep. In order to prevent these damages and losses, it is necessary to do a proper understanding of these accidents. Offshore systems as of the main parts of ocean structures and their accidents are considered here in this paper. From 1975 some data showing offshore accidents are captured in the Worldwide Offshore Accident Databank (WOAD), which are the main data bank to be used in this study. These data are about offshore damages and collapses due to Fires, Blowout, Anchor failure, Capsize, Explosion, etc. The main scope of the study is on fixed offshores, named jackets...
Thermal stress analysis of concrete arch dams due to enviromental action
, Article 2004 ASME International Mechanical Engineering Congress and Exposition, IMECE, Anaheim, CA, 13 November 2004 through 19 November 2004 ; Volume 375, Issue 1 , 2004 , Pages 393-402 ; 02725673 (ISSN) ; Ghaemian, M ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2004
Abstract
A three-dimensional finite element analysis was carried out to determine the annual variation of temperature and thermal stresses of a concrete arch dam. Appropriate heat transfer boundary conditions in the dam body were used for air and reservoir temperature as well as solar radiation variations. Karaj arch dam in Iran was used as a case study. The rate of convergence of the numerical solution is examined. Results of the finite element analysis show that probable cracks occur in a very narrow region of the downstream face. Thermal loads have the most significant effects for causing downstream cracks in comparison with self-weigh and hydrostatic loads. The cracked areas of downstream face...
General solution for mechanical and thermal stresses in a functionally graded hollow cylinder due to nonaxisymmetric steady-state loads
, Article Journal of Applied Mechanics, Transactions ASME ; Volume 70, Issue 1 , 2003 , Pages 111-118 ; 00218936 (ISSN) ; Sohrabpour, S ; Eslami, M. R ; Sharif University of Technology
2003
Abstract
In this paper, the general theoretical analysis of two-dimensional steady-state thermal stresses for a hollow thick cylinder made of functionally graded material is developed. The temperature distribution is assumed to be a function of radial and circumferential directions with general thermal and mechanical boundary conditions on the inside and outside surfaces. The material properties, except Poisson's ratio, are assumed to depend on the variable r and they are expressed as power functions of r. The separation of variables and complex Fourier series are used to solve the heat conduction and Navier equations
White space regions
, Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 22 January 2011 through 28 January 2011, Novy Smokovec ; Volume 6543 LNCS , 2011 , Pages 226-237 ; 03029743 (ISSN) ; 9783642183805 (ISBN) ; Fazli, M ; Ghodsi, M ; Safari, M ; Saghafian, M ; Tavakkoli, M ; Sharif University of Technology
2011
Abstract
We study a classical problem in communication and wireless networks called Finding White Space Regions. In this problem, we are given a set of antennas (points) some of which are noisy (black) and the rest are working fine (white). The goal is to find a set of convex hulls with maximum total area that cover all white points and exclude all black points. In other words, these convex hulls make it safe for white antennas to communicate with each other without any interference with black antennas. We study the problem on three different settings (based on overlapping between different convex hulls) and find hardness results and good approximation algorithms
CFD Modeling of Temperature Fluctuation in Mixing of Hot and Cold Streams in a Mixing Tee
, M.Sc. Thesis Sharif University of Technology ; Farhadi, Fathollah (Supervisor)
Abstract
This thesis tries to suggest a simple solution to reduce the amplitude of occurred fluctuations in mixing tees. Temperature fluctuations can induce cyclical thermal stress and thermal fatigue. In order to estimate the lifetime of pipeline material and reduce the frequency and amplitude of these fluctuations, an accurate diagnosis of these fluctuations must be conducted. For this aim, a comparison between Reynolds Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) models was carried out to show the ability of LES model in prediction of temperature fluctuations. The effect of Peclet number on the amplitude was discussed. The effect of placing simple pipe segments and orifices to...
Thermal Analysis of Concrete arch Dams Using Real Reservoir Data and Comparing the Results with Stucky-derron Method
, M.Sc. Thesis Sharif University of Technology ; Ghaemian, Mohsen (Supervisor)
Abstract
Thermal analysis of concrete arch dams is always an important issue in designig these enormous concrete structures. The reason this issue mainly concerns arch dams and not gravity dams is because of little thickness of arch dams which makes them prone to cracking due to thermal loading. To solve any thermal problem we need boundary conditions. In arch dam case, these boundaries are the temperature of the upstream and downstream face of the dam which, depending on circumstances, can be in touch with water or air. Estimating air temperature is a fairly easy task when you have monthly mean temperatures. The challenging part is defining water temperature in any depth of the reservoir whenever we...
Transient conduction prediction in nozzle assembly of solid rocket motors
, Article 45th AIAA Aerospace Sciences Meeting 2007, Reno, NV, 8 January 2007 through 11 January 2007 ; Volume 4 , 2007 , Pages 2333-2337 ; 1563478900 (ISBN); 9781563478901 (ISBN) ; Tahsini, A. M ; Sharif University of Technology
2007
Abstract
Transient heat-up of a solid propellant rocket structure during motor burning time is studied, numerically. The solid phase energy equation coupled with unsteady compressible flow equations are used in this simulation. The flow-field equations are discretized and solved using upwind Roe's scheme. The results show that heat transfer from the gas phase boundaries has negligible effect on internal ballistics behavior. On the other hand, the results are suitable for a thermal stresses analysis in the chamber case and are consequently valuable from structural design viewpoints
FEM elasto-plastic analysis of a new manufacturing method for covering the free surface of unidirectional composites
, Article Computational Materials Science ; Volume 36, Issue 4 , 2006 , Pages 411-424 ; 09270256 (ISSN) ; Adibnazari, S ; Rashidi Moghadam, A ; Sharif University of Technology
2006
Abstract
Fiber/matrix debonding at the free surface of unidirectional composites deteriorates their performance and ultimately reduces the working life of these materials. Identifying the source, controlling the propagation and elimination of the damages has been the subject of many research attempts. The results show that the singular radial thermal residual stress at the fiber/matrix interface on the free surface of composites is the main reason for initiation of the debonding. Also, it has been experimentally and numerically proven that a thin layer of matrix-like cover on the free surface could highly help in elimination and/or reduction of the damage. However, the results were limited to the...
An FGM coated elastic solid under thermomechanical loading: A two dimensional linear elastic approach
, Article Surface and Coatings Technology ; Volume 200, Issue 12-13 , 2006 , Pages 4050-4064 ; 02578972 (ISSN) ; Ghahremaninejad, A ; Sharif University of Technology
2006
Abstract
A thin coating made of linear elastic functionally graded material (FGM) perfectly bonded to an elastic substrate is considered. This work which is of particular interest to tribological community is devoted to the determination of the thermal and mechanical stresses due to mixed normal and tangential Hertzian surface pressure. The thermomechanical properties of the FGM coating are assumed to vary exponentially through the thickness. Solutions for temperature rise and stresses are obtained by use of Fourier transform technique. The influences of coating thickness, Peclet number and friction coefficient on temperature rise and stresses in the FGM coating are investigated. Comparative studies...
Simulation of windscreen bending using viscoplastic formulation
, Article Journal of Materials Processing Technology ; Volume 170, Issue 1-2 , 2005 , Pages 298-303 ; 09240136 (ISSN) ; Rad, M ; Shahhosseini, M. R ; Shahhosseini, M. H ; Sharif University of Technology
2005
Abstract
Soda-lime glass material has been widely used for automobile windscreens. Two commercial finite element programs have been evaluated for simulation of the creep forming process using isotropic viscoplastic behavior assumption for soda-lime glass. This was done by selecting one of the programs and using it in connection with an optimization program for controlling the glass surface temperature, to examine the effect of considering thermal stresses and temperature variations along the surface of glass sheet for obtaining desired geometrical shape. The results show that the thermal stress effect must be considered for achieving more accurate simulation of glass creep forming process. Also...
Optimization of functionally graded materials in the slab symmetrically surface heated using transient analytical solution
, Article Journal of Thermal Stresses ; Vol. 37, issue. 2 , February , 2014 , pp. 137-159 ; ISSN: 01495739 ; Taati, E ; Tabrizi, H. B ; Sharif University of Technology
Abstract
Functionally graded materials (FGMs) have been introduced to significantly reduce the temperature and thermal stresses on structures at severe thermal loading. Design and development of FGMs as the heat treatable and energy-absorbing materials for high-temperature and thermal protection systems requires understanding of exact temperature and thermal stress distribution, in order to optimize their resistance to failure. In this study, transient temperature and associated thermal stresses in a functionally graded slab symmetrically heated on both sides are determined by separation of the variables scheme. This method is applied to the heat conduction equation in terms of heat flux for...
Prediction of thermal stresses and temperature field in work rolls during hot strip rolling process
, Article Materials Science and Technology ; Volume 26, Issue 3 , 2010 , Pages 343-351 ; 02670836 (ISSN) ; Serajzadeh, S ; Sharif University of Technology
2010
Abstract
In this work, a combined finite element analysis and upper bound technique is employed to assess temperature field and thermal stress distribution within the work rolls during continuous hot strip rolling process. Two-dimensional finite element analysis is utilised to simultaneously predict temperature fields within the rolling metal and the work roll as well as thermal stresses in the work rolls. In order to calculate the velocity field and the rate of heat of deformation, an upper bound solution is coupled with the employed finite element analysis. The utilised model makes it possible to estimate the effects of different parameters such as idling revolutions and initial temperature on...
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...
Failure analysis of gas turbine burner tips
, Article Engineering Failure Analysis ; Volume 99 , 2019 , Pages 7-17 ; 13506307 (ISSN) ; Attarian, M ; Kermajani, M ; Abdi, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
In this study, the causes of failure in gas turbine burner tips were investigated. For this purpose, two burner tips used in a petrochemical company with different failure evidence as well as service times were inspected. These parts showed signs of deterioration such as multiple cracks, corrosion, and wear following 4000 h and 8000 h operations. The examinations included chemical composition analysis using optical emission spectroscopy (OES), stereo-, optical-, and scanning electron microscopy studies, and macro/micro-hardness measurements. These investigations revealed high thermal stresses to be the main failure cause of the burner tips. Moreover, due to flame inclination, a local...
Thermo-elastic Development of Cylindrical and Spherical Superelements and Introduce a New Gigh Speed Angular Contact Bearing Superelement Model
, M.Sc. Thesis Sharif University of Technology ; Movahhedy, Mohammad Reza (Supervisor)
Abstract
Angular contact bearings are utilized in many industrial types of machinery, including machine tools’ spindle. Spindle is one of the most important parts of a machine tool, which has a substantial impact on dynamic properties and stability of machining processes. Spindles’ motion takes place under guidance of bearings, which are mainly angular contact type. Since bearings’ loading under forces that are resulted from angular velocity and temperature increment are intensified, it is required to control the applied forces in operating situation, in order to predict the hardness, accuracy, efficiency, and life time of spindle. Thus, determining the dynamic performance of machine tool’s spindle,...
Prediction of Cooling Rate and Thermal Stresses during Cooling on Run-Out Table in Hot Sheet Rolling Process
, M.Sc. Thesis Sharif University of Technology ; Serajzadeh, Siamak (Supervisor)
Abstract
Control of the product manufacturing and evaluating its behavior during deformation is one of the most important issues in hot deformation, especially hot rolling. One of the factors affecting on quality of hot rolled steel strips is the flatness after run-out table cooling.Distortion in a steel strip results from non-uniform temperature profile as the strip cools to room temperature. Increase in the rolling velocity and subsequently the cooling rate affect thermal stresses. In this study a mathematical model for prediction of austenite- ferrite phase transition kinetics and thermo-mechanical stresses on the run-out table after hot rolling was developed for low carbon ferrite steels....
Parametric Analysis of Thermomechanical Stresses in Functionally Graded Materials Under in-phase and out-of-phase Loading
, M.Sc. Thesis Sharif University of Technology ; Abedian, Ali (Supervisor)
Abstract
Using Functionally Graded Materials (FGMs) in hot sections of aged aircrafts is one of the most important ways for life extending of Thermal Barrier Coatings (TBCs). Sudden variation of thermal stresses in interface of bond coat and ceramic coat layers could be changed to gradual variation with use of FGMs. The stress in FGMs has been the subject of several researches. Both macro and micromechanical modeling approaches have been used in these studies. In the macro mechanical approach, FGM is modeled as a multi-layer composite in which mechanical properties of each layer is found by averaging the properties and volume fraction of FGM constituents through the thickness of the layer. In this...