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creep-behavior
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Numerical study on the creep behavior of the metal matrix short fiber composites with application in optoelectronic and photonic devices
, Article Optoelectronics and Advanced Materials, Rapid Communications ; Volume 9, Issue 9-10 , 2015 , Pages 1088-1092 ; 18426573 (ISSN) ; Daneshmand, S ; Fazaeli, D ; Sharif University of Technology
Abstract
FEM study is carried out for predicting the behavior of the short fiber composites in the steady state creep with application in optoelectronic and photonic devices. The study on the creep behavior is necessary in order for failure, fracture, fatigue, and creep resistance of the short fiber composites. In this article, the creep behavior of the short fiber composite is predicted under tensile axial loading by the numerical method. One of the significant applications of the work is in the short fiber composite designing and optimizing. Also, the available experimental results [10] are used for the FEM simulation
Analysis of Creep Behavior and Stability of Underground Fuel Storage in Rock Salt
, M.Sc. Thesis Sharif University of Technology ; Sadaghiani, Mohammadhosein (Supervisor)
Abstract
The purpose of this study is to analyze the stability and creeping behavior of rock salt in underground gas and oil reservoirs. Preparation of natural salt caverns and operating them can manipulate the initial state of previously existed stress and to produce deviatoric stresses around the cavern. New state of stress and with creeping behavior of rock salt, causes a significant decrease in cavern’s volume and damages the surrounding area. Reduction of internal minimum pressure of cavern, increases the intensity of mentioned problems. Geometrical characteristics of cavern can also be significantly effective in the magnitude of damages around the reservoir. For instance, Deflection of cavern...
Discrete Element Simulation of Creep Behavior in Asphalt Mixtures
,
M.Sc. Thesis
Sharif University of Technology
;
Tabatabaei, Nader
(Supervisor)
Abstract
Composite nature of asphalt mixtures necessitates a micromechanical scheme which depends on distinctive characteristics of various constitutive phases. In this regard, discrete element method was utilized to predict the creep behavior of asphalt mixtures and strain response in primary, secondary and tertiary stages. In this research, a modified mixture modeling procedure was considered to better simulate permanent deformation response of asphalt mixtures under creep loading. A random distribution of mastic and aggregate particles with respect to a typical dense gradation was implemented to reconstruct cylindrical specimens. A bonding model represented the cohesion effect in mastic...
Nanoindentation creep behavior of nanocomposite Sn-Ag-Cu solders
, Article Journal of Electronic Materials ; Volume 41, Issue 8 , 2012 , Pages 2057-2064 ; 03615235 (ISSN) ; Kokabi, A. H ; Miyashita, Y ; Mutoh, Y ; Ihara, I ; Guan Fatt, R. G ; Madaah Hosseini, H. R ; Sharif University of Technology
Abstract
High-density, ultrasmall-pitch electronic applications require miniaturized solder bumps with improved thermomechanical performance. In addition, novel techniques which are able to precisely characterize these solder bumps are needed. One approach to meeting both of these requirements is to make use of recently developed nanocomposite solders with enhanced creep resistance, and to characterize these solders using a nanoindentation technique. In the present study, the creep behavior of ceria-reinforced nanocomposite solder foils fabricated by the accumulative roll-bonding process was characterized using a depth-sensing nanoindentation technique. It was found that the creep resistance of the...
Effect of reduced graphene oxide reinforcement on creep behavior of adhesively bonded joints
, Article Mechanika ; Volume 23, Issue 5 , 2017 , Pages 646-652 ; 13921207 (ISSN) ; Nazari, S. A ; Faghidian, S. A ; Vakili Tahami, F ; Sharif University of Technology
Kauno Technologijos Universitetas
2017
Abstract
The creep behaviour of adhesively bonded joints is one of the major concerns in modern industry due to their application at relatively high temperature. In this re-search, the effect of added RGO on the creep behaviour of the Araldite 2011 adhesive is investigated. Uni-axial creep tests have been carried out on neat Araldite 2011 and RGO added adhesive at different stress and temperature levels. It has been shown that adhesive with RGO particles demonstrate higher creep resistance. Also, general time hardening models are developed for both materials and their constitutive coefficients have been determined using creep test data. Based on these models, the creep behavior of single lap joints...
Deformation and creep characteristics of AA7075-T76 at elevated temperatures
, Article Journal of Materials Engineering and Performance ; Volume 31, Issue 9 , 2022 , Pages 7586-7595 ; 10599495 (ISSN) ; Serajzadeh, S ; Sharif University of Technology
Springer
2022
Abstract
In this work, deformation behavior as well as creep and cavitation of AA7075-T76 were studied. The as-received plate was first stabilized utilizing solution treatment followed by two-stage artificial aging at 120 and 180 °C. Then, tensile tests were carried out on the aged-alloy in the temperature range between 120 and 250 °C under strain rates of 0.0005 and 0.005 s−1. Furthermore, stress-controlled creep tests were performed at temperatures varying between 120 and 210 °C at stresses ranging from 130 to 250 MPa. Microstructural evolution was then conducted to assess the microstructural changes and growth of cavities during creep employing optical metallography and scanning electron...
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 ; 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...
Casing failure in salt rock: numerical investigation of its causes
, Article Rock Mechanics and Rock Engineering ; Volume 53, Issue 9 , 2020 , Pages 3903-3918 ; Pak, A ; Sharif University of Technology
Springer
2020
Abstract
Numerous cases of casing failure have been reported worldwide. Depletion-induced compaction is one of the main factors that may cause casing failure. Stress perturbation in salt layers may accommodate rock flow which endangers the stability of cased wells. Besides, poor cementing jobs are recognized as one of the wellbore instability causes. These factors need to be considered to determine the mechanism behind the casing failure. In this study, the creep behavior of the caprock salt layer in the southwest Iranian oil fields is experimentally studied through a number of creep tests under conditions of elevated temperature and pressure. Then, a three-dimensional finite element analysis is...
An Investigation into Creep Behavior and Cavitation in a 7000-Series Aluminum Alloy
, M.Sc. Thesis Sharif University of Technology ; Serajzadeh, Siamak (Supervisor)
Abstract
In this study, creep behavior and cavitation as well as high temperature deformation of Al-Zn-Mg aluminum alloy were investigated by means of uni-axial creep and tensile tests. The as-received material i.e. AA7075 plate, was first stabilized utilizing over-aging heat treatment and then stress-controlled creep tests were performed in the temperatures ranging between 120℃ to 210℃ under the applied stresses varying 130MPa to 250MPa. Accordingly, the stress exponent and creep activation energy were determined as 5.7 and 149kJ/mol.K to 189kJ/mol.K, respectively. Considering these parameters, it was found that the governing creep mechanism, in the mentioned temperature range, would be dislocation...
The Effect of Heat Treatment on Microsructure, Hot Tensile Properties and Creep Bihavior of Nickel-based Superalloy CM88Y
, M.Sc. Thesis Sharif University of Technology ; Asgari, Sirous (Supervisor)
Abstract
The Ni-base superalloy CM88Y has good hot corrosion resistance, high stability and strength at elevated temperature; accordingly, the alloy is used in manufacturing of gas turbine hot components. In most applications, heat treatment is required in order to achieve the desired mechanical properties and corrosion resistance of the working conditions; often three stages of heat treatment is designed for precipitation hardening nickel-base superalloy. In general, the effective parameters of heat treatment cycles includes temperature, time, heating rate and the cooling rate. In this study, the effect of cooling rate from partial solution temperature (second stage of heat treatment) on the...
A new analytical shear-lag based model for prediction of the steady state creep deformations of some short fiber composites
, Article Materials and Design ; Volume 30, Issue 4 , 2009 , Pages 1075-1084 ; 02641275 (ISSN) ; Abedian, A ; Ghavami, A ; Sharif University of Technology
2009
Abstract
A new analytical model based on the shear-lag theory is developed for stress analysis and prediction of the steady state creep deformation of short fiber composites subjected to an applied axial load. A perfect fiber/matrix interface is assumed and the steady state creep behavior of the matrix is described by an exponential law. The results obtained from the proposed analytical solution satisfy the equilibrium and constitutive creep equations. These analytical results are then validated by the FEM modeling. Interestingly, good agreements are found between the analytical and numerical predictions for all the stress and displacement rate components. © 2008 Elsevier Ltd. All rights reserved
An investigation on microstructure and creep behavior of an over-aged Al2024-10vol%SiC composite prepared by hot powder extrusion
, Article European Powder Metallurgy Congress and Exhibition, Euro PM 2007, Toulouse, 15 October 2007 through 17 October 2007 ; Volume 2 , 2007 , Pages 345-352 ; 9781899072293 (ISBN) ; Seyed Reihani, S. M ; Aryanpour, A ; Sharif University of Technology
European Powder Metallurgy Association (EPMA)
2007
Abstract
In this study, the aging effect on microstructure and creep behavior of Al2024-10%SiC composite fabricated by powder metallurgy was studied. P/M bars were manufactured by hot powder extrusion method at 450°C with a ratio of 16 to1. Creep specimens were over-aged at 187°C for 43 h. It was found that almost full density composite with relatively homogenous distribution of the reinforcement particles throughout the aluminum alloy matrix can be attained by the direct powder extrusion process. Creep tests were conducted at temperatures of 275 to 325°C under stresses of 25 to 60 MPa. The creep tests revealed that the aged composites demonstrate a weaker creep behavior compared with non-aged...
Multiscale Modeling of Creep Behavior of Nickel-Based Superalloys
, Ph.D. Dissertation Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
Nowadays, single-crystal nickel-based superalloys are widely used in the manufacture of gas turbine blades in the aerospace industry due to their high resistance to creep, fatigue and corrosion at high temperatures. The superior behavior of these materials at elevated temperatures is a result of their two-phase microstructure, which includes the matrix phase (γ) of nickel and the precipitate phase (γ') of Ni3Al intermetallic compounds with a high volume fraction. The aim of this thesis is to develop computational modeling tools to study the creep deformation of single-crystal Ni-based superalloys. At high temperatures, the creep deformation of Ni-based superalloys is determined by the atomic...
Finite difference solution of steady state creep deformations in a short fiber composite in presence of fiber/matrix debonding
, Article Materials and Design ; Volume 31, Issue 5 , 2010 , Pages 2616-2624 ; 02641275 (ISSN) ; Abedian, A ; Mondali, M ; Sharif University of Technology
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 through a micromechanical approach. The technique is capable to take into account the presence of interfacial debonding as one of the main factors affecting the creep performance of short fiber composites. The exponential law is adopted to describe the matrix creep behavior. Also, a model 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...
Effect of rare earth elements addition and T6 heat treatment on creep properties of Mg-Al-Zn alloy
, Article Magnesium Technology 2009, San Francisco, CA, 15 February 2009 through 19 February 2009 ; 2009 , Pages 483-488 ; 15454150 (ISSN); 9780873397308 (ISBN) ; Khomamizadeh, F ; Magnesium Committee of the Light Metals Division; Minerals, Metals and Materials Society, TMS ; Sharif University of Technology
2009
Abstract
This paper focuses on creep properties of AZ91-RE and heat treated AZ91 magnesium alloy. Influence of heat treatment and rare earths addition on microstructure and mechanical properties were investigated. Creep behavior is dependent on the stability of the near grain boundary microstructure and is improved by rare earth addition. The results show that sliding of grain boundaries has an important part in the deformation mechanism in AZ91 alloy at elevated temperatures which is greatly suppressed by the rare earths addition
Mechanical properties and γ/γ' interfacial misfit network evolution: A study towards the creep behavior of Ni-based single crystal superalloys
, Article Mechanics of Materials ; Volume 171 , 2022 ; 01676636 (ISSN) ; Youzi, M ; Tolooei Eshlaghi, G ; Sharif University of Technology
Elsevier B.V
2022
Abstract
The aim of this study is to investigate the role of the temperature, stress, and rhenium (Re) on the γ/γ' interfacial misfit dislocation network and mechanical response of Ni-based single crystal superalloys. After aging at elevated temperatures, mismatch between the two phases results in an interfacial dislocation network to relieve the coherency stress. Molecular dynamics (MD) simulations have been performed to study the properties of the (100), (110), and (111) phase interface crystallographic directions. Increasing temperature disperses the atomic potential energy at the interface diminishing the strength and stability of the networks. In the case of loading, when a constant strain rate...
Creep behavior of hot extruded Al-Al2O3 nanocomposite powder
, Article Materials Science and Engineering A ; Volume 527, Issue 10-11 , 2010 , Pages 2567-2571 ; 09215093 (ISSN) ; Simchi, A ; Seyed Reihani, S. M ; Sharif University of Technology
2010
Abstract
A commercial gas-atomized aluminum powder was mechanically milled in a planetary ball mill under an argon atmosphere for 12 h to produce alumina dispersion strengthened aluminum powder. Transmission electron microscopy (TEM) revealed that about 2 vol.% alumina particles with an average size of 100 nm were distributed in the aluminum matrix. The nanocomposite powder was canned in an aluminum container, vacuum de-gassed, and hot extruded at 723 K at an extrusion ratio of 16:1. The creep behavior of the extruded billet in the direction of extrusion was examined at a constant applied load ranging from 10 to 40 MPa at temperatures of 648, 673 and 723 K. A threshold creep-stress was noticed which...
Effect of deep cryogenic treatment on microstructure, creep and wear behaviors of AZ91 magnesium alloy
, Article Materials Science and Engineering A ; Volume 523, Issue 1-2 , 2009 , Pages 27-31 ; 09215093 (ISSN) ; Tari, A ; Khomamizadeh, F ; Sharif University of Technology
2009
Abstract
This paper focuses on the effect of deep cryogenic treatment (-196 °C) on microstructure and mechanical properties of AZ91 magnesium alloy. The execution of deep cryogenic treatment on samples changed the distribution of β precipitates. The tiny laminar β particles almost dissolved in the microstructure and the coarse divorced eutectic β phase penetrated into the matrix. This microstructural modification resulted in a significant improvement on mechanical properties of the alloy. The steady state creep rates were measured and it was found that the creep behavior of the alloy, which is dependent on the stability of the near grain boundary microstructure, was improved by the deep cryogenic...
The effect of different rare earth elements content on microstructure, mechanical and wear behavior of Mg-Al-Zn alloy
, Article Materials Science and Engineering A ; Volume 527, Issue 7-8 , 2010 , Pages 2027-2035 ; 09215093 (ISSN) ; Masoudi, A ; Khomamizadeh, F ; Sharif University of Technology
2010
Abstract
The effect of Rare earths addition to AZ91 magnesium alloy and its influence on the microstructure and mechanical properties was investigated in this study. Addition of cerium rich misch metal to AZ91 alloy resulted in formation of needle shape particles, which had a very high thermal stability, providing superior mechanical properties compared to AZ91 magnesium alloy. As a result, the grain boundaries were less susceptible for grain boundary sliding at high temperatures. The steady state creep rates were specified and for the AZ91 alloy and the results indicate a mixed mode of creep behavior, with some grain boundary effects contributing to the overall behavior. However for the RE added...
The effect of different content of Al, RE and Si element on the microstructure, mechanical and creep properties of Mg-Al alloys
, Article Materials Science and Engineering A ; Volume 523, Issue 1-2 , 2009 , Pages 1-6 ; 09215093 (ISSN) ; Tari, A ; Khomamizadeh, F ; Sharif University of Technology
2009
Abstract
The effect of Al content and Si addition on the microstructural and creep properties of Mg-Al-RE alloys was investigated in this study. The steady state creep rates were specified and it was found that the creep behavior of the alloy, which is dependent on the stability of the near grain boundary microstructure, was improved by the RE and Si addition. For the AZ91 alloy, the results indicate a mixed mode of creep behavior, with some grain boundary effects contributing to the overall behavior. However for the RE and Si added samples, sliding of grain boundaries was greatly suppressed and the dislocation climb controlled creep was the dominant deformation mechanism. Analysis of creep rates...