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    Numerical Analysis of Stresses and Steady State Creep Strain Rates Fields of a Short Fibre Composite

    , M.Sc. Thesis Sharif University of Technology Ghavami, Ali (Author) ; Abedian, Ali (Supervisor)
    Abstract
    A finite difference technique is developed to predict the second stage creep displacement rates and stress analysis of a short fiber metal matrix composite subjecting to a constant axial load. The exponential law is adopted to describe the matrix creep behavior. Also, a method for prediction of interfacial debonding at fiber/matrix interface is developed using a stress based method. The obtained results could greatly help to better understand the flow pattern of matrix material and the load transfer mechanism between fiber and matrix. The stress components and strain rates are also validated by the available FEM and experimental results  

    Flexural Strengthening of Reinforced Concrete Beams by FRP Composites to Reduce Creep Deflection

    , M.Sc. Thesis Sharif University of Technology Zarringol, Mohammad Reza (Author) ; Kazemi, Mohammad Taqhi (Supervisor)
    Abstract
    The strengthening of reinforced concrete structures with externally bonded fibre reinforced polymer (FRP) laminates has shown excellent performance, so this technology is rapidly replacing externally bonded steel plates, steel or concrete jackets, and many traditional techniques available. In this study strengthening of reinforced concrete beams by GFRP to reduce creep deflection is investigated by mathematical method using available relations. Five RC beams with different dimensions, with and without strengthening with GFRP laminate, were investigated for their creep deflection. The creep coefficient of beams selected from experimental result that were mentioned in RILEM DATA BANK. In this... 

    Modeling & Analysis of CAES Considering Reliability

    , M.Sc. Thesis Sharif University of Technology Motaei، Sajad (Author) ; Rajabi Qahnuyeh, Abbas (Supervisor)
    Abstract
    All over the world availability of electrical power is an important matter. Electrical power is a basic requirement in each country so with increasing the demand, supply system should be adjusted.Compressed Air Energy System (CAES) stores the excessive produced energy as compressed air and will inject it to gas turbine to produce energy in peak load hours.This project aim is modeling and analyzing of CAES considering reliability. In this project some of failure mechanisms have been identified and modeled and then the performance effect on system failure have been surveyed. This project innovation is incorporating operational models with reliability to determine the best performance for... 

    Developing a New Method to Evaluate and Quality Control of Chip Seal

    , M.Sc. Thesis Sharif University of Technology Jahi, Hamed (Author) ; Motamed, Arash (Supervisor)
    Abstract
    Chip seal is one of the most economical pavement maintenance practice that extends pavement life. To ensure chip seal good performance several quality control methods have been developed. However, most of these methods are qualitative and only measure the stone loss under a certain number on loading. This research developed a new method for quality control of chip seal, based on the assumption that characteristics of the bond between chips and pavement surface play a key role in chip seal performance. To validate this test method, the authors used a wheel track loading test. The results from this research clearly showed that the characteristics of the bond between chips and pavement surface... 

    Characterisation of Mechanical Fracture Properties of an Alloy Steel Using Small-punch-test

    , M.Sc. Thesis Sharif University of Technology Fallah Yakhdani, Alireza (Author) ; Farai, Gholamhossein (Supervisor)
    Abstract
    Small punch test is an efficient technique to determine mechanical properties of large as well as small industrial parts. In this method a steel ball puncher with small radius, penetrate to the workpiece under certain displacement. Properties of the sample are detemined by measuing of force and obtaine the load-displacement diagram. In this study, small punch test was used to determine mechanical and fracture properties of 1.4841 steel. For these purpose small punch test was simulated by using finite element method, and exprimental small punch test was also done for mention steel which was under hydrogen embritment and creep due to working conditions. Afterward, exprimental results were... 

    The Evaluation of Microstructure and Mechanical Properties of a HSHR Stainless Steel Strengthen by Nano-Precipitates

    , Ph.D. Dissertation Sharif University of Technology Attarian, Mitra (Author) ; Karimi Taheri, Ali (Supervisor) ; Davami, Parviz (Co-Advisor)
    Abstract
    In this research, a computational method based on thermodynamic and physical metallurgy coupled by the d-electron approach was used to design the composition of a high strength and heat resistant (HSHR) stainless steel. Then, three series of the heat resistant 25Cr-35Ni-Nb (HP-Nb) stainless steels with tungsten, nitrogen, and micro alloying elements additions were cast. In these alloys a Nb/(C+ 6/7 N) ratio of ≈ 2.4 to 3.7 was chosen and they were directionally solidified under two cooling rates of 23 Ks-1 and 6 Ks-1. The effects of the alloy chemical composition and solidification cooling rate on the macrostructure, microstructure, microsegregation, and inclusions in the alloys were... 

    Investigating the Effect of Various Additives on the Curing Time of Chip Seal and Chip Seal Treatments in Different Climate Conditions.

    , M.Sc. Thesis Sharif University of Technology Sadeghi, Amir (Author) ; Motamed, Arash (Supervisor)
    Abstract
    Recently, a new method to investigate chip seal performance has developed by a research team at Sharif University of Technology. This study investigates the effect of various additives such as CRM, SBR Latex, Hydrated Lime and Ordinary Portland Cement (OPC), on the curing time of chip seal by this method. In addition, the chip seal treatments were investigated in different climate conditions like Wet and Wet-Freeze zones. The overall performance of mixture specimens evaluated using creep loading test. In fact, the bonding properties between aggregates and surface of Hot Mix Asphalt measured. The test results were analyzed by using of the work and time parameters. These parameters were... 

    High Temperature Deformation and Creep-Aging Behavior of an Aluminum Alloy 5083

    , M.Sc. Thesis Sharif University of Technology Khodamoradi, Zahra (Author) ; Serajzadeh, Siamak (Supervisor)
    Abstract
    Mechanical behavior of aluminum-magnesium alloy, AA5083, was studied at high temperatures using hot tensile testing together with uniaxial creep experiments. In the first place, the as-received AA5083 sheet was subjected to annealing heat treatment to remove the effect previous plastic straining. Then, creep experiments were conducted at temperatures in the range of 190°C to 300 ° C under constant the stress varied between 30 MPa to 100 MPa. The hot tensile testing was also carried out from room temperatures up to 400 °C under nominal constant strain rates of 0.0005, 0.005, 0.01 and, 0.05 (1/s). In addition to the mechanical testing, optical metallography and scanning electron microcopy were... 

    A Multi-Scale Method for Modeling and Analysis of the Creep Behavior in Composite plates

    , M.Sc. Thesis Sharif University of Technology Barzegar, Mohsen (Author) ; Hosseini Kordkheili, Ali (Supervisor)
    Abstract
    Polymer matrix composites, which are composed of a wide variety of short or long fibers bound together by organic polymer matrix, have been widely utilized in many engineering aeras, particularly in aerospace engineering. Recently, studying and analyzing the mechanical behavior of composites was one of the major reaserch interests. Regarding the vast variety of data drived from experimental tests, a requirement of tools that could facilitate estimating creep properties of materials is an important concern for researchers. The present work at first, introduces some major creep models and then proposes a 3D creep Burgers model for implementing in abaqus which could be used in macro phase. This... 

    A Study on the Effect of Initial Microstructures on Deformation Behavior of an Aluminum-Copper Alloy at Elevated Temperatures

    , M.Sc. Thesis Sharif University of Technology Molaei, Soheil (Author) ; Serajzadeh, Siamak (Supervisor)
    Abstract
    In this research, hot deformation and creep behavior of aluminum alloy i.e.AA2017 were taken into account while the impact of the initial microstructure of the examined alloy was also studied. In order to investigate the behavior of the alloy, tensile tests were conducted at temperatures ranging from 120°C to 400°C under the nominal strain rates of 0.0005 s-1, 0.005 s-1, 0.05 s-1. In these experiments, two different initial microstructures were employed including solution treated samples as well as artificially aged specimens. The results show that in the temperature range of 180°C to 250°C, the strain rate sensitivity parameter is negative in the solution treated samples which indicates... 

    An Investigation of Alloying Elements Effect on Creep Behavior of Ni-Based Super Alloys Using Molecular Dynamics

    , M.Sc. Thesis Sharif University of Technology Youzi, Mehrdad (Author) ; Khoei, Amir Reza (Supervisor)
    Abstract
    The aim of this study is to investigate the role of the temperature, stress, strain rate, and rhenium (Re) on the γ\/γ^' interfacial misfit dislocation network and mechanical response of Ni-based single crystal superalloys. The interfacial network plays an important role in the superior creep behavior of Ni-based superalloys. Therefore, a comprehensive understanding of this topic would help us to go through the impact of various factors on the mechanical and creep properties at high temperatures to achieve an optimal design. Due to the mismatch between the two phases, a dislocation network forms after aging at high temperatures to alleviate the stress field. The (100), (110), and (111)...