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ductility
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Experimental Study of Circulating Tumor Cell (CTC) by Application of Microfluidic Systems and its Related Characterization Studies
, Ph.D. Dissertation Sharif University of Technology ; Khorasheh, Farhad (Supervisor) ; Vossoughi, Manouchehr (Supervisor) ; Alemzadeh, Iran (Supervisor)
Abstract
Isolation and characterization of circulating tumor cells (CTCs) found in blood samples of cancer patients have been considered as a reliable source for cancer prognosis and diagnosis. A new continuous microfluidic platform has been designed in this investigation for simultaneous capture and characterization of CTCs based on their deformability. The deformability-based chip (D-Chip) consists of two sections of separation and characterization where slanted weirs with a gap of 7 μm were considered. Although sometimes CTCs and leukocytes have the same size, the deformability differs in such a way that can be exploited for enrichment purposes. MCF7 and MDA-MB-231 cell lines were used for the...
Experimental and Numerical Studies on Trapezoid Ally Corrugated Steel Shear Walls with Opening under Cyclic Loading
, Ph.D. Dissertation Sharif University of Technology ; Mofid, Masood (Supervisor)
Abstract
Steel shear wall is a lateral load resistance system, which has been taken into consideration in recent decades for designing and reinforcing high-rise buildings. This system is comprised of steel filler panel surrounded by frame members including beams and columns. Steel shear walls are presently fabricated in two types, stiffened and unstiffened. According to numerous conducted research, it can be stated that the stiffened type has better seismic performance. The use of stiffeners with a great number of executive details is required to spend more time and costs on the construction sector. In order to solve these problems, some experimental and numerical studies have been conducted on...
Research on Influences of Coating on Low Cycle Fatigue Properties of Ni-Base Superalloy René 80
, Ph.D. Dissertation Sharif University of Technology ; Nategh, Saeed (Supervisor)
Abstract
In this thesis, based on the taking-off and landing of aircraft with GE 21-J85 turbine, the low cycle fatigue (LCF) test for superalloy used in first stage blades is considered. The LCF tests were performed on both coated and uncoated Rene 80 which are used in GE 21-J85 turbine at R = (min/max) = 0, strain rate of 2 10-3 s-1 and 760oC, 871oC and 982oC. To produce specimens, an investment casting method was used so that adequate amount of polycrystalline round bars could be obtained. The specimens were all homogenized and solution treated. After the inspection, some specimens were coated with pack cementation method in CODEP-B powder in H2 atmosphere. The coated and uncoated specimens all...
Investigating the Behaviour of A Type of Energy Absorbing Bracing System
, M.Sc. Thesis Sharif University of Technology ; Khonsari, Vahid (Supervisor)Microstructural Evolution During Post-Bond Heat Treatment of Brazed Nickel Base Super Alloys
, M.Sc. Thesis Sharif University of Technology ; Pouranvari, Majid (Supervisor) ; Kokabi, Amir Hossein (Co-Supervisor)
Abstract
The brazing process is the preferred method for bonding and repairing high temperature resistant superalloys. In this process, filler metals containing MPD elements such as B and Si are used. The presence of these elements causes the formation of brittle and eutectic phases such as borides and silicides in the joint area. These phases reduce the mechanical properties and re-melting temperature of the joint. By increasing the temperature and time of bonding and using the concept of isothermal solidification, the formation of boride and silicide phases can be prevented. In wide gap joints, the time to complete the isothermal solidification is very long, and applying such temperature and time...
An Investigation on The Effect of Intermediate Deformation Between The Retrogression and Re Aging Process of 7xxx Series of Aluminum Alloys on The Mechanical Properties and Formability of These Alloys
, M.Sc. Thesis Sharif University of Technology ; Karimi Taheri, Ali (Supervisor) ; Kazeminejad, Mohsen (Supervisor)
Abstract
In this research it has been attempted to suggest a modified retrogression and re- aging heat treatment on the sheet of AA7075 alloy with a thickness of 2 mm. The main aim of the research is to reduce the required duration of RRA process while maintaining the value of the conventional tensile strength achieving by the RRA process. This was performed by adding an intermediate warm rolling deformation during the RRA process. The rolling temperature was 180 °C and the rolling reductions were 30%, 40%, 50%. Moreover, the temperature of 170°C was selected as the re-aging temperature, for which the aging time of 0.5, 1, 1.5, 2, and 2.5 hours were examined. This temperature and times were chosen to...
A New Method Based on Crystal Plasticity Finite Element to Predict the Formability of Steel Sheets with Spheroidal Cementites
, Ph.D. Dissertation Sharif University of Technology ; Assempour, Ahmad (Supervisor)
Abstract
In this research, using the crystal plasticity finite element method, the effects of various microstructural features on behavior of spherical steel sheets have been investigated. The cementite phase ratio, the grain sizes of ferrite and cementite, and the percentage of residual pearlite in the steel structure due to incomplete annealing are the major microstructural parameters studied in this work. A grain generator software has been developed to generate ferrite grains as well as cementite particles distributed in the ferrite matrix. A hard coating with special properties as an intermediate layer around the cementite grains has been considered to simulate the contact between ferrite grains...
Numerical simulation of ductile crack growth under cyclic and dynamic loading with a damage–viscoplasticity model
, Article Engineering Fracture Mechanics ; Volume 99 , February , 2013 , PP. 169–190 ; Eghbalian, M ; Azadi, H ; Saffar, H ; Sharif University of Technology
Abstract
In this paper, the crack propagation in ductile materials is simulated under cyclic and dynamic loading. The adaptive finite element method is used to model the discontinuity due to crack propagation. The ductile fracture assumptions and continuum damage mechanics are utilized to model the material rupture behavior. Moreover both the rate-independent and rate-dependent constitutive equations are elaborated and the crack closure effect and combined hardening model are discussed in addition to some aspects of finite element implementation. Finally, a comparison is performed between the numerical simulation results and those of experiments to illustrate the robustness of proposed computational...
Inelastic displacement ratios for soil-structure systems allowed to uplift
, Article Earthquake Engineering and Structural Dynamics ; Vol. 43, issue. 9 , July , 2014 , p. 1401-1421 ; ISSN: 00988847 ; Jafarieh, A. H ; Sharif University of Technology
Abstract
The simultaneous effects of soil-structure interaction, foundation uplift and inelastic behavior of the superstructure on total displacement response of soil-structure systems are investigated. The superstructure is modeled as an equivalent single-degree-of-freedom system with bilinear behavior mounted on a rigid foundation resting on distributed tensionless Winkler springs and dampers. It is well known that the behavior of soil-structure systems can be well described using a limited number of nondimensional parameters. Here, by introducing two new parameters, the concept is extended to inelastic soil-structure systems in which the foundation is allowed to uplift. An extensive parametric...
Study on microstructure and mechanical characteristics of low-carbon steel and ferritic stainless steel joints
, Article Materials Science and Engineering A ; Vol. 608, issue , 2014 , pp. 35-45 ; ISSN: 09215093 ; Mostafaei, M. A ; Pouraliakbar, H ; Kokabi, A. H ; Sharif University of Technology
Abstract
In this work, examinations on the microstructure and mechanical properties of plain carbon steel and AISI 430 ferritic stainless steel dissimilar welds are carried out. Welding is conducted in both autogenous and using ER309L austenitic filler rod conditions through gas tungsten arc welding process. The results indicate that fully-ferritic and duplex ferritic-martensitic microstructures are formed for autogenous and filler-added welds, respectively. Carbide precipitation and formation of martensite at ferrite grain boundaries (intergranular martensite) as well as grain growth occur in the heat affected zone (HAZ) of AISI 430 steel. It is found that weld heat input can strongly affect grain...
Toughness enhancement in roll-bonded Al6061-15 vol.% SiC laminates via controlled interfacial delamination
, Article Journal of Materials Engineering and Performance ; Volume 22, Issue 11 , 2013 , Pages 3414-3420 ; 10599495 (ISSN) ; Bagheri, R ; Reihani, S. M. S ; Sharif University of Technology
2013
Abstract
Researchers have examined different approaches to improve damage tolerance of discontinuously reinforced aluminum (DRA). In this study, three-layer DRA laminates containing two exterior layers of Al6061-15 vol.% SiCp and an interlayer of Al1050 were fabricated by hot roll bonding. Interfacial adhesion between the layers was controlled by means of rolling stain. The results of shear test revealed that, the bonding strength of laminates was influenced by number of rolling passes. Considering this effect, the role of interfacial bonding on the toughness of laminates was studied under three-point bending in the crack divider orientation. The quasi-static toughness of the laminates was greater...
The extended finite element method for large deformation ductile fracture problems with a non-local damage-plasticity model
, Article Engineering Fracture Mechanics ; Volume 112-113 , 2013 , Pages 97-125 ; 00137944 (ISSN) ; Khoei, A. R ; Sharif University of Technology
2013
Abstract
An enriched-FEM technique is presented for the crack growth simulation in large deformation ductile fracture problems using a non-local damage-plasticity model in the framework of eXtended Finite Element Method (X-FEM). The Lemaitre damage-plasticity model is used to capture the material degradation effect, in which the non-locality is enforced by solving a Helmholtz type equation in combination with the governing equation of the system based on an operator-split technique. A convergence study is performed to investigate the performance of X-FEM technique in plasticity problems. The accuracy and effectiveness of proposed X-FEM damage-plasticity model are verified through several numerical...
Comparison of nonlinear behavior of steel moment frames accompanied with RC shear walls or steel bracings
, Article Structural Design of Tall and Special Buildings ; Volume 22, Issue 14 , 2013 , Pages 1062-1074 ; 15417794 (ISSN) ; Kheyroddin, A ; Kafi, M. A ; Nikbakht, H ; Sharif University of Technology
2013
Abstract
In this paper, the seismic behavior of dual structural systems in forms of steel moment-resisting frames accompanied with reinforced concrete shear walls and steel moment-resisting frames accompanied with concentrically braced frames, have been studied. The nonlinear behavior of the mentioned structural systems has been evaluated as, in earthquakes, structures usually enter into an inelastic behavior stage and, hence, the applied energy to the structures will be dissipated. As a result, some parameters such as ductility factor of structure (μ), over-strength factor (Rs) and response modification factor (R) for the mentioned structures have been under assessment. To achieve these objectives,...
The effect of Ti on mechanical properties of extruded in-situ Al-15 pct Mg2Si composite
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 44, Issue 9 , September , 2013 , Pages 4366-4373 ; 10735623 (ISSN) ; Bahrami, A ; Pech Canul, M. I ; Sharif University of Technology
2013
Abstract
This work was carried out to investigate the effect of different Ti concentrations as a modifying agent on the microstructure and tensile properties of an in-situ Al-15 pctMg2Si composite. Cast, modified, homogenized small ingots were extruded at 753 K (480°C) at the extrusion ratio of 18:1 and ram speed of 1 mm/s. Various techniques including metallography, tensile testing, scanning electron microscopy were used to characterize the mechanical behavior, microstructural observations, fracture mechanisms of this composite. The results showed that 0.5 pctTi addition and homogenizing treatment were highly effective in modifying Mg2Si particles. The results also exhibited that the addition of Ti...
Laser welding of NiTi shape memory alloy: Comparison of the similar and dissimilar joints to AISI 304 stainless steel
, Article Optics and Laser Technology ; Volume 54 , 2013 , Pages 151-158 ; 00303992 (ISSN) ; Saatchi, A ; Kermanpur, A ; Sadrnezhaad, S. K ; Sharif University of Technology
2013
Abstract
The unique properties of NiTi alloy, such as its shape memory effect, super-elasticity and biocompatibility, make it ideal material for various applications such as aerospace, micro-electronics and medical device. In order to meet the requirement of increasing applications, great attention has been given to joining of this material to itself and to other materials during past few years. Laser welding has been known as a suitable joining technique for NiTi shape memory alloy. Hence, in this work, a comparative study on laser welding of NiTi wire to itself and to AISI 304 austenitic stainless steel wire has been made. Microstructures, mechanical properties and fracture morphologies of the...
Failure analysis of a gas turbine compressor in a thermal power plant
, Article Journal of Failure Analysis and Prevention ; Volume 13, Issue 3 , 2013 , Pages 313-319 ; 15477029 (ISSN) ; Farrahi, G. H ; Masoumi Khalil Abad, M ; Zare, A. A ; Parsa, S ; Sharif University of Technology
2013
Abstract
This study presents the results of failure analysis of a 28 MW gas turbine at the Rei electrical power plant. The gas turbine failed during the shutdown period and near its second natural frequency at 4200 rpm. Initial inspections revealed that the compressor disk of stage 15 was fractured, and all of the stationary and rotary blades of stages 14-18 of the compressor had been detached or broken from the dovetail region of the disks. The fracture roots were investigated by performing finite element modeling and fractography analysis. It was shown that a crack was initiated from the disk edge on its interface with the rotor shaft and was propagated under cyclic loading. As a result of the...
Probabilistic evaluation of seismic design parameters of RC frames based on fragility curves
, Article Scientia Iranica ; Volume 20, Issue 2 , 2013 , Pages 231-241 ; 10263098 (ISSN) ; Asadi, P ; Sharif University of Technology
2013
Abstract
There are many parameters utilized to obtain a more reasonable performance for structures under earthquake excitations in seismic provisions. General considered parameters in seismic provisions are: PGA, importance factor (I) and typical inherent overstrength and global ductility capacity (R). It is well recognized that the main characteristic of the design of structures under seismic excitation is probabilistic rather than deterministic; therefore, it should be determined if whether the probability of structural damage decreases when such parameters change in the design of structures. In this paper, fragility curves are developed in order to evaluate these parameters. Fragility curves are...
Experimental study on cyclic behavior of trapezoidally corrugated steel shear walls
, Article Engineering Structures ; Volume 48 , March , 2013 , Pages 750-762 ; 01410296 (ISSN) ; Mofid, M ; Vafai, A ; Sharif University of Technology
2013
Abstract
This paper presents the research works on the cyclic behavior of trapezoidally corrugated as well as unstiffened steel shear walls. A series of experimental studies were carried out on the half-scale, one-story, single-bay steel shear walls with unstiffened and trapezoidally corrugated panels. This experimental study was conducted to compare the stiffness, strength, ductility ratio and energy dissipation capacity of three different steel shear walls: unstiffened, trapezoidally vertical corrugated and trapezoidally horizontal corrugated. Gravity loads were not applied at the top of the walls and horizontal load was applied at the top of each specimen. Loading sequence was applied as...
Producing Ti-6Al-4V/TiC composite with superior properties by adding boron and thermo-mechanical processing
, Article Materials Science and Engineering A ; Volume 564 , 2013 , Pages 473-477 ; 09215093 (ISSN) ; Abbasi, S. M ; Sharif University of Technology
2013
Abstract
In order to study the effect of boron addition on the microstructure and tensile properties of titanium matrix composites, two Ti-6Al-4V/10. Vol% TiC ingots with and without boron were fabricated by VIM furnace and hot rolling. The microstructures of composites were examined using optical microscopy (OM). The X-ray diffraction (XRD) was used to identify the phases present in the composites. Addition of boron resulted in the formation of needle shaped TiB in the matrix that was followed by the refinement of grain size. Compared with Ti-6Al-4V/TiC composite, the composite containing boron content exhibited a significantly higher ductility and lower strength. It was caused by the effects of...
On the characteristics and design of yielding elements used in steel-braced framed structures
, Article Structural Design of Tall and Special Buildings ; Volume 22, Issue 2 , 2013 , Pages 179-191 ; 15417794 (ISSN) ; Mofid, M ; Sharif University of Technology
2013
Abstract
In this paper, the behavior of a concentric braced frame structure equipped with yielding elements (YE), based on energy concepts, has been investigated extensively. When a severe earthquake occurs, energy will get absorbed through structural elements, which causes destruction. In order to reduce structural damage, input energy should be dissipated. YE will act as a fuse and absorb a great deal of earthquake input energy. Two one-story steel frames with different bay-to-height ratios (B/H < 1 and B/H > 1) are investigated. YE is located in the braces intersection. First, through studying the elastic behavior of the frame, the best location, angle and shape of YE is proposed. Subsequently, a...