Search for: thermal-cycling
Total 26 records
Energy analysis of part flow and full flow Humid Air Turbine Cycle (HAT), Article 2006 ASME 51st Turbo Expo, Barcelona, 6 May 2006 through 11 May 2006 ; Volume 4 , 2006 , Pages 319-327 ; 0791842398 (ISBN); 9780791842393 (ISBN) ; Khaledi, H ; Bakhtiari, B ; Ghofrani, M. B ; Sharif University of Technology
Current researches on the development of gas turbine related power plants such as HAT cycle and Combined Cycle are aimed to increase the plant efficiency and output power, while reducing the cost of power generation and emission. Humid air turbine cycle (HAT) is one of innovative cycles, which are able to provide a substantial power boost of the system and an efficiency rise of several percentage points. In order to perform energy analysis of Full Flow HAT cycle and Part Flow HAT cycle an advanced thermodynamic model is developed, which is enabling evaluation of behavior of Full Flow and Part Flow Humid Air Turbines and predicting the influence of operational parameters in the performance of...
Numerical study of Geostationary Orbit thermal cycle effects of a tubular adhesive joint: Dynamic behavior, Article Journal of Adhesion ; Volume 96, Issue 16 , 2020 , Pages 1431-1448 ; Mokhtari, M ; Sharif University of Technology
Bellwether Publishing, Ltd 2020
Space environments have a significant influence on advanced composite structures and adhesive joints. Degradation in the mechanical properties of aerospace materials changes the dynamic behavior of the structures and adhesive joints. In this paper, a typical tubular adhesive joint with material degradation due to geostationary orbit (GEO) thermal cycles has been studied numerically with Python scripts. Adhesive joint geometry and boundary conditions are the main parametric study parameters. The results show that the first non–zero natural frequencies of the clamped-free tubular adhesive joint decreased due to mechanical property degradation. A dynamic behavior comparison of the degradation...
The influence of welding polarity on mechanical properties, microstructure and residual stresses of gas tungsten arc welded AA5052, Article International Journal of Advanced Manufacturing Technology ; Volume 105, Issue 7-8 , 2019 , Pages 3397-3409 ; 02683768 (ISSN) ; Serajzadeh, S ; Sharif University of Technology
The effect of welding current and polarity, i.e. AC and DCEN, on imposed thermal cycles, mechanical properties, microstructural events and residual stresses was investigated in GTA welding of AA5052. A three-dimensional thermo-mechanical model was utilized to evaluate thermal responses and residual stresses distribution in the weldments. Tensile testing and hardness measurements were also conducted to study the effect of welding polarity on the mechanical properties of components. Microstructural observations utilizing optical microscopy were carried out to assess the microstructural evolutions. The results show that wide varieties of microstructures are produced in DCEN sample from cells at...
Effect of thermal cycles on mechanical response of pultruded glass fiber reinforced polymer profiles of different geometries, Article Composite Structures ; Volume 223 , 2019 ; 02638223 (ISSN) ; Ashrafi, H ; Bazli, M ; Ozbakkaloglu, T ; Sharif University of Technology
Elsevier Ltd 2019
This study investigates the effect of Thermal cycles on the mechanical properties of GFRP pultruded profiles with different geometries. Bending specimens consisted of I-shaped and U-channel profiles that were tested in three-point bending along their both principal weak and strong axes, whereas box profiles and laminates were used in compression and tension tests, respectively. Each specimen was exposed to a range of thermal cycles, between −20 °C and 20 °C. The failure modes of the profiles were closely investigated at both major and minor scales. Results were analyzed using ANOVA to determine the influence of each factor and a model was developed to predict the strength retention of...
Using Aerodynamic Obstacles to Increase the Thermal Performance of Power Plant Cooling Systems Consisting of Air Cooled Condenser, M.Sc. Thesis Sharif University of Technology ; Darbandi, Massoud
According to the recent researches it has been found that wind can reduce the efficiency of Air Cooled Condensers (ACC) which use for cooling purposes in power plants. Wind affects the natural suction of the cooling air and makes local low pressure area in fan’s inlet results to disrupt its normal performance. Using aerodynamic obstacles inside and around the condensers can compensate this lack of performance when there is strong wind. In this thesis with the aid of computational fluid dynamics, condenser’s behavior with various weather situations is studied. Simulation in no wind situation and different wind speeds is considered and accomplished with Gambit Fluent software. This simulation...
The Effects of Stress-Assisted Heat Treatment on the Microstructure and Phase Transformation Behavior of Ni-Rich Ni-Ti Shape Memory Alloy, M.Sc. Thesis Sharif University of Technology ; Asgari, Sirous
Ni-Ti shape memory alloys have attracted most of the research in the field of shape memory alloys both because of their complicated and diverse phase transformation characteristics and their optimum properties for various applications which span such a properties as shape memory effect, pseudoelasticity, excellent mechanical properties and biocompatibility. The key properties of these alloys is generated through a thermoelastic martensitic transformation the occurrence of which is extremely sensitive to the metallurgical conditions of the alloy e.g. composition and microstructure. This has led to the development of various procedures implemented in either fabrication, processing or heat...
Study of Microstructure and Mechanical Properties of Heat Affected Zone with Gleeble Simulator for Tandem Submerged Arc Welding of X80 HSLA Steel, Ph.D. Dissertation Sharif University of Technology ; Kokabi, Amir Hossein ; Madaah Hosseini, Hamid Reza
The X80 high-strength low-alloy microalloyed steel was procured as a hot rolled plate with accelerated cooling. The four-wire tandem submerged arc welding process, with different heat input, was used to generate a welded microstructure. The effects of real and Gleeble simulated double pass thermal cycles on the properties of the heated and reheated coarse grained heat affected zones (CGHAZ) in X80 microalloyed pipeline steel has been investigated. The thermal simulated process for heated region involved heating the X80 steel specimens to the peak temperature of 1400 °C, with different cooling rates. The influence of the second peak temperature during real and simulated welding hass been...
Design, Simulation and Construction of a Rapid Gene Amplification Microfluidic Device Using Polymerase Chain Reaction (PCR) Method, M.Sc. Thesis Sharif University of Technology ; Shamloo, Amir
Polymerase chain reaction method is a conventional method for obtaining multiple copies of a specified segment in the DNA molecule and to amplify the DNA molecule itself. Therefore, this method has been of paramount importance in different fields of research and has been applied for different applications. PCR requires thermal cycling, or repeated temperature changes between two or three discrete temperatures to amplify specific nucleic acid target sequences. To achieve such thermal cycling, conventional bench-top thermal cyclers generally use a metal heating block powered by Peltier elements or benefit from forced convection heat transfer. Although efforts have been made in order to reduce...
Study, Optimization and Construction of a Microfluidic Gene Amplification Device by Using Thin Film Layer Method, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Manouchehr ; Alemzadeh, Iran ; Shamloo, Amir
Polymerase Chain Reaction (PCR) is a process in which a special piece of a gene is amplified millions of times over a short period. This method has been of paramount importance in different fields of research and has been applied for different applications. PCR requires thermal cycling, or repeated temperature changes between two or three discrete temperatures to amplify specific nucleic acid target sequences. To achieve such thermal cycling, conventional bench-top thermal cyclers generally use a metal heating block powered by Peltier elements or benefit from forced convection heat transfer. Due to the fact that these methods are time consuming, it seems that design and fabrication of a fast...
Investigation of thermo-mechanical response of a geothermal pile through a small-scale physical modelling, Article 2nd International Conference on Energy Geotechnics, ICEGT 2020, 20 September 2020 through 23 September 2020 ; Volume 205 , 2020 ; Ghasemi Fare, O ; Yazdani Cherati, D ; Jafarzadeh, F ; Sharif University of Technology
EDP Sciences 2020
Energy piles have been used around the world to harvest geothermal energy to heat and cool residential and commercial buildings. In order to design energy geo-structures, thermo-mechanical response of the geothermal pile must be carefully understood. In this paper, a small scale physical model is designed and a series of heating thermal cycles with various vertical mechanical loads are performed. The instrumented pile is installed inside a dry sand bed. Changes in pile head displacement, shaft strains and pile and sand temperatures are monitored using an LVDT, strain gauges and thermocouples, respectively. Prolonged heating cycles, which would continue until boundary temperature changes,...
Influence of mechanical treatments on the mechanical properties of AA5083 aluminum alloy welded joints, Article 17th International Metallurgical and Materials Conference, METAL 2008, 13 May 2008 through 15 May 2008 ; 2008 ; 9788025419878 (ISBN) ; Abachi, P ; Taheri, N ; Sharif University of Technology
TANGER spol. s r.o 2008
Aluminum alloy series 5xxx lose their strength, especially in the heat affected zone (HAZ) of welds, due to thermal cycle during welding process. Because of this thermal cycle, re-crystallization and grain coarsening in HAZ occur, which result in decreasing of mechanical properties. In this paper the influence of "overloading" and "shot peening" as methods of post weld treatment on mechanical properties of AA5083 aluminum alloy welded joints is investigated. The results show that both overloading and shot peening treatments increase the hardness and tensile strength of welded joints. It is observed that the influence of overloading is stronger than shot peening on increasing hardness of the...
Effect of tandem submerged arc welding process and parameters of Gleeble simulator thermal cycles on properties of the intercritically reheated heat affected zone, Article Materials and Design ; Volume 32, Issue 2 , February , 2011 , Pages 869-876 ; 02641275 (ISSN) ; Kokabi, A. H ; Hosseini, H. R. M ; Sharif University of Technology
The effects of real and Gleeble simulated double pass thermal cycles on the properties of the intercritically reheated coarse grained heat affected zones in X80 microalloyed pipeline steel has been investigated. The Gleeble simulated process involved heating the X80 steel specimens to the first peak temperature of 1400°C and then reheating to the second peak temperature of 800°C, with different cooling rates. The size and area fraction of martensite/austenite (M/A) constituents were obtained by a combination of field emission scanning electron microscopes and image analysis software. In addition, misorientation was characterized by electron back-scatter diffraction analysis. It is clear that...
Role of tandem submerged arc welding thermal cycles on properties of the heat affected zone in X80 microalloyed pipe line steel, Article Journal of Materials Processing Technology ; Volume 211, Issue 3 , 2011 , Pages 368-375 ; 09240136 (ISSN) ; Kokabi, A. H ; Hosseini, H. R. M ; Sharif University of Technology
The influence of thermal cycles on the properties of the coarse grained heat affected zone in X80 microalloyed steel has been investigated. The thermal simulated involved heating the X80 steel specimens to the peak temperature of 1400 °C, with different cooling rates. The four-wire tandem submerged arc welding process, with different heat input values, was used to generate a welded microstructure. The martensite/austenite constituent appeared in the microstructure of the heat affected zone region for all the specimens along the prior-austenite grain boundaries and between the bainitic ferrite laths. The blocky-like and stringer martensite/austenite morphology were observed in the heat...
Influence of peak temperature during simulation and real thermal cycles on microstructure and fracture properties of the reheated zones, Article Materials and Design ; Volume 31, Issue 6 , June , 2010 , Pages 2948-2955 ; 02641275 (ISSN) ; Kokabi, A. H ; Madaah Hosseini, H. R ; Sharif University of Technology
The objective of this paper is to study the influence of the second peak temperature during real and simulated welding on properties of the subcritically (S), intercritically (IC) and supercritically (SC) reheated coarse grained heat affected (CGHAZ) zones. The X80 high strength pipeline microalloyed steel was subject to processing in a double-pass tandem submerged arc welding process with total heat input of 6.98 kJ/mm and thermal cycles to simulate microstructure of reheated CGHAZ zones. This involved heating to a first peak temperature (TP1) of 1400 °C, then reheating to different second peak temperatures (TP2) of 700, 800 and 900 °C with a constant cooling rate of 3.75 °C/s. Toughness of...
Microstructure and phase transformation behavior of a stress-assisted heat-treated Ti-Rich NiTi shape memory alloy, Article Journal of Materials Engineering and Performance ; Volume 21, Issue 8 , August , 2012 , Pages 1806-1812 ; 10599495 (ISSN) ; Rezaei, E ; Sharif University of Technology
In this study, the effects of stress-assisted heat treatment on the microstructure and phase transformation of a Ti-rich (Ti-49.52 at.% Ni) shape memory alloy were investigated. For this purpose, the alloy was heat treated at temperature of 500 °C for 10 h under applied stresses of 100 and 200 MPa. XRD, TEM, and repeated thermal cycling were employed to study the microstructure and transformation behavior of the heat-treated materials. Room temperature XRD diffractogram of the stress-free heat-treated material showed a weak reflection of austenite (B2), while that for the stress-assisted heat-treated materials had a high intensity implying the presence of residual austenite in the...
A fem study of the overlapping ratio effect on superplastic formation of metal matrix composites, Article 27th Congress of the International Council of the Aeronautical Sciences 2010, ICAS 2010, 19 September 2010 through 24 September 2010, Nice ; Volume 3 , 2010 , Pages 1836-1843 ; 9781617820496 (ISBN) ; Abedian, A ; Sharif University of Technology
In aerospace applications structures weight is considered as a major performance parameter. One of the most effective manufacturing methods for weight reduction is superplastic forming. By this technique, not only the weight, but also the stress concentration, the cost, and the manufacturing time are noticeably reduced. Additionally, the components with complicated shapes could be formed in a single manufacturing step. Due to the wide demand for whiskers reinforced metal matrix composites (MMCs) in aerospace industries, many research works have been designed to extend the borders of superplastic forming to MMCs materials. In the present study, a 3-D symmetric micromechanical finite element...
Investigation of weld pool in aluminum alloys: geometry and solidification microstructure, Article International Journal of Thermal Sciences ; Volume 49, Issue 5 , 2010 , Pages 809-819 ; 12900729 (ISSN) ; Serajzadeh, S ; Kokabi, A. H ; Sharif University of Technology
In the present research, weld pool geometry, thermal cycle, temperature and velocity fields during gas tungsten arc welding of aluminum alloys were predicted by solving three-dimensional equations of conservation of mass, energy and momentum under steady-state conditions. Welding experiments were then conducted on several samples with different thicknesses and chemical compositions. The geometries of the weld pools as well as the thermal cycles were measured. It is found that the calculated geometry of the weld fusion zone and the weld thermal cycles are in good agreement with the corresponding experimental results. In addition, the magnitude of the maximum velocities under different...
Numerical simulation of mixing and heat transfer in an integrated centrifugal microfluidic system for nested-PCR amplification and gene detection, Article Sensors and Actuators, B: Chemical ; Volume 283 , 2019 , Pages 831-841 ; 09254005 (ISSN) ; Ghazimirsaeed, E ; Shamloo, A ; Sharif University of Technology
Elsevier B.V 2019
Nucleic acid amplification via polymerase chain reaction (PCR) is one of the essential and powerful methods used in a myriad of bio-assays in clinical laboratories. Application of microfluidic devices in biologically-related processes like PCR can result in the usage of less volume of reactant samples and reduce the processing time. By implementing PCR systems on centrifugal microfluidic platforms, automation and portability can be easily achieved. Although several methods have been developed, most of them are still dealing with challenges of the required high processing time. This study presents the numerical simulation of a fully automated PCR system with the goal of enhancing the mixing...
Improving the performance of a photonic PCR system using TiO2 nanoparticles, Article Journal of Industrial and Engineering Chemistry ; 2020 ; Ghazimirsaeed, E ; Shamloo, A ; Dizani, M ; Sharif University of Technology
Korean Society of Industrial Engineering Chemistry 2020
Nucleic acid amplification using polymerase chain reaction (PCR) method has been widely used in different fields such as agricultural science, medicine, pathogen identification, and forensics to name a few. Today, it seems inevitable to have a robust, simple PCR system for diagnostics at the point-of-care (POC) level. Many photonic PCR systems have been proposed in the literature that benefit from plasmonic photothermal heating to achieve the common PCR thermal cycling. However, non-homogeneous temperature distribution is a challenge in some of them. In the present work, to achieve more efficient gene amplification, the effect of adding TiO2 nanoparticles has been investigated in a photonic...
Numerical analysis of vibration effect on friction stir welding by smoothed particle hydrodynamics (SPH), Article International Journal of Advanced Manufacturing Technology ; Volume 110, Issue 1-2 , 2020 , Pages 209-228 ; Abdollahzadeh, A ; Abbasi, M ; Kokabi, A. H ; Sharif University of Technology
A numerical analysis is improved to study the effect of vibration on temperature history, heat generation, and mechanical properties during the friction stir welding process with different welding speeds. In this investigation, smoothed particle hydrodynamics (SPH) was applied to improve the 3D numerical analysis for simulation of the friction stir welding (FSW) process and friction stir vibration welding (FSVW) under different welding speeds. According to the experimental analysis, the grain size of the FSVW-ed sample is finer compared with that of the FSW-ed sample. The analysis was validated through a comparison of the simulated thermal cycles with the experimental results. There was a...