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ductility
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Effects of number of layers and adhesive ductility on impact behavior of laminates
, Article Materials Letters ; Volume 58, Issue 22-23 , 2004 , Pages 2721-2724 ; 0167577X (ISSN) ; Bagheri, R ; Mahmudi, R ; Sharif University of Technology
2004
Abstract
Laminated composites are made using different routes, including adhesive bonding. In this investigation, Aluminum layers are bonded together using epoxy adhesive (neat, rubber-modified and filled-epoxy). In phase one of this investigation, the influence of number of layers and adhesive ductility have been studied on dynamic behavior of composites. The results of impact behavior of laminates indicate that the impact energy increases with the number of layers. Also, it can be concluded that there is much more sensitivity of the impact energy of the composite to the number of the layers than that to the adhesive composition. © 2004 Elsevier B.V. All rights reserved
The Investigation of Effective Parameters on Mechanical Properties of MADI
, M.Sc. Thesis Sharif University of Technology ; Davami, Parviz (Supervisor) ; Varahram, Naser (Supervisor)
Abstract
The Machinable Austempered Ductile Iron (MADI), a new group of Austempered Ductile Iron (ADI), has been developed to remove the problems (hardness and cost) of ADI cast iron. MADI is a special kind of ductile iron which has proper machinabilty properties. This kind of ductile iron can be produced using a specific chemical composition and defined heat treatment process. By providing these conditions, the hardness of the cast iron will be in the range of as-cast cast iron. On the other hand, because of the especial production process, the cost of the final shape casting will be lower than ADI cast iron. In the present work, firstly the effect of heat treatment parameters, including the time...
Investigation into microstructure and mechanical properties of heavy section nickel alloyed austempered ductile iron in accordance with austempering parameters
, Article Material Design and Processing Communications ; Volume 3, Issue 4 , 2021 ; 25776576 (ISSN) ; Varahram, N ; Perseh, Y ; Sharif University of Technology
John Wiley and Sons Inc
2021
Abstract
Austempered ductile iron (ADI) is one of the most widely used types of ductile iron produced by austempering heat treatment. ADI heavy section parts are employed in different industries owing to their unique mechanical properties. Cooling rate in thick parts is significantly low, so heavy section ductile iron parts should have an adequate austemperability for preventing pearlite formation in the middle of the casting. In order to achieve the proper austemperability and fully ausferritic structure, alloying elements like nickel are added to the melt. The objective of this work is to study the role of austempering parameters on nickel alloyed ADI specimens fabricated from 75-mm-thick Y-block....
Effect of Mold Hardness on Microstructure and Contraction Porosity in Ductile Cast Iron
, Article Journal of Iron and Steel Research International ; Volume 18, Issue 4 , 2011 , Pages 44-47+67 ; 1006706X (ISSN) ; Amin Ahmadi, B ; Sharif University of Technology
2011
Abstract
The effect of mold hardness on the microstructure of ductile iron and the contraction porosity was investigated. Molds with different hardnesses (0.41, 0.48, 0.55, 0.62 MPa) and a sand mold prepared by Co2 method were used. The influence of silicon content on the induced expansion pressure owing to the formation of graphite was also investigated. The contraction during solidification can be compensated by an induced expansion owing to the graphite relief when the hardness of mold increases; therefore, the possibility of achieving a sound product without using any riser increases
Tensile behaviour and ductility of 10 vol.-% Saffil short fibre reinforced aluminium
, Article Materials Science and Technology ; Volume 20, Issue 12 , 2004 , Pages 1645-1648 ; 02670836 (ISSN) ; Nategh, S ; Weber, L ; Sharif University of Technology
2004
Abstract
The tensile behaviour of Saffil short fibre reinforced aluminium composites has been investigated in terms of Young's modulus, yield strength, ultimate tensile strength, and strain to failure. A rationale is given for the unusually high strain to failure found in this material by applying a failure criterion based on damage accumulation, recently developed for particulate reinforced MMCs
The effect of controlled cooling after hot rolling on the mechanical properties of a commercial high carbon steel wire rod
, Article Materials and Design ; Volume 24, Issue 6 , 2003 , Pages 415-421 ; 02641275 (ISSN) ; Karimi Taheri, A ; Sharif University of Technology
Elsevier Ltd
2003
Abstract
In this research, the effects of different cooling conditions after hot rolling in Stelmor conveyor line on the mechanical properties of a commercial high carbon steel wire rod are investigated. By opening and closing the lids, turning on and off the fans in Stelmor system, an air patenting process is performed on a commercial high carbon steel to improve its mechanical properties and ductility. The wire rods produced in different cooling conditions are investigated by tensile test, metallography and image analyzing. The optimum cooling condition required for high strength and ductility are evaluated. Moreover, the relationships between yield stress, UTS and fracture stress, and...
Ductility evaluation of confined high-strength concrete flexural members
, Article Iranian Journal of Science and Technology, Transaction B: Technology ; Volume 25, Issue 1 , 2001 , Pages 129-131 ; 03601307 (ISSN) ; Tariverdilu Asl, S ; Sharif University of Technology
2001
Abstract
The influence of concrete strength on the ductility of RC flexural members is investigated. Tests were carried out on beams with three ranges of concrete strengths, and moment-curvature and deflection curves obtained. It is concluded that when the concrete is laterally confined by closed steel ties beams with various levels of concrete strength and very high tensile strength steel exhibit high ductility
Influence of confining hoop flexural stiffness on behavior of high-strength lightweight concrete columns
, Article ACI Structural Journal ; Volume 98, Issue 5 , 2001 , Pages 657-664 ; 08893241 (ISSN) ; Bozorgzadeh, A ; Sharif University of Technology
2001
Abstract
This paper presents the behavior of high-strength lightweight concrete columns confined with small size diameter hoop reinforcement. The concrete had a strength of up to 87.2 MPa (12,500 psi). The experimental program consisted of axial load tests on eight column specimens. The cross-sectional shape of the column specimens was elliptical, with dimensions of 152 × 229 mm (6 × 9 in.) and height of 762 mm (30 in.). The only longitudinal reinforcements used were four 4.52 mm (0.178 in.) diameter wires that were tack-welded to the lateral reinforcement to maintain the desired configuration of the lateral reinforcement. The influencing parameters included concrete strength and amount and spacing...
Study on the Kinetics of Enzymatic Biodiesel Production Using Castor Oil
, M.Sc. Thesis Sharif University of Technology ; Varahram, Nasser (Supervisor) ; Ashuri, Hossein (Supervisor)
Abstract
Increasing emissions of greenhouse gases from one hand and decline in the fossile resources of energy on the other hand has raised the motivation of searching for renewable sources. Biodiesel, because of having perfect feature for replacing with petroleum diesel, has been considered as candidate for this purpose. Using enzymatic reaction is one of the methods for biodiesel production. Understanding the kinetics of this reaction is important to achieve higher production rates. In present work, the kinetic of transesterification of castor oil with use of Novozyme 435 (as enzyme) was investigated. Enzymatic biodiesel production is a bi-substrate (oil and alcohol) reaction. Genetic algorithm was...
Effect of austempering parameters on microstructure and mechanical properties of heavy section Machinable Austempered Ductile Cast Iron (MADI)
, Article Materials Research Express ; Volume 6, Issue 6 , 2019 ; 20531591 (ISSN) ; Varahram, N ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
The first important limitation of ADI usage in industries is the machinability of the parts. Machinable Austempered Ductile Cast Iron (MADI) is a novel kind of ADI with improved properties such as better machinability compared to ADI and similar to as cast ductile iron. Furthermore, MADI has a higher strength than ductile iron at the same hardness value. The present work aimed to investigate into the impact of the austempering time and temperature on microstructure and mechanical properties of ductile iron samples prepared from Y-block with 75 mm thickness. In order to achieve the microstructure of the continuous matrix of equiaxed ferrite with islands of austenite, samples were partially...
The Effect of Cu and Sn on Fatigue Properties of Pearlitic Ductile Iron
, M.Sc. Thesis Sharif University of Technology ; Varahram, Naser (Supervisor) ; Davami, Parviz (Supervisor)
Abstract
Pearlitic Ductile Iron are being used variously for producing different kinds of components in industry. For producing of Pearlitic structure in some kind of components such as crankshaft, copper and tin are being used. In many cases according to conditions and facilities of the replacement, these two elements normally have been used.Despite the fact that mostly components are influenced by the fatigue, the influence of these two elements on the fatigue properties of the components hasn’t been studied comprehensively.In this research, the influence of the copper and tin alloying elements on the fatigue limit of the Pearlitic Ductile Iron has been studied.The samples of ductile iron with...
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...
Effect of heat treatment cycle on the mechanical properties of machinable austempered ductile iron
, Article 16th International Metallurgical and Materials Conference, METAL 2007, 22 May 2007 through 24 May 2007 ; 2007 ; Baghersaee, N ; Varahram, N ; Hanumantha Rao, M ; Rao, G. V.S. N ; Sharif University of Technology
TANGER spol. s r.o
2007
Abstract
ADI have been used for a wide variety of application in automotive,rail,and heavy engineering industry because of its excellent mechanical properties such as high strength with good ductility,good wear resistance,and good fatigue properties. The properties of austempered ductile iron are dependent on both chemistry and heat treatment, which has lead to invention of MADI (machinable austempered ductile iron). MADI is a new class of ductile iron with superior mechanical property than regular ductile iron with the same machinability characteristic. In this study Different cycles of austempering process (austenitization and austempering cycle) applied Due to the effect of heat treatment cycle on...
Ductility of saffil™ short fibre reinforced metals
, Article Scripta Materialia ; Volume 53, Issue 1 , 2005 , Pages 17-21 ; 13596462 (ISSN) ; Tavangar, R ; Mortensen, A ; Sharif University of Technology
2005
Abstract
A critical combination of matrix strain hardening exponent and fiber volume exceeded to confer tensile ductility to short-fiber reinforced metal. The bimodal distribution of tensile ductilities observed in such materials can be attributed to a transition in damage mode, from fiber fragmentation to matrix voiding. Building on results for model composites of this class and making a few specification, a simple criterion can be proposed to predict whether such composites display a low or a high tensile elongation. The results show that, composites of this class are ductile if their matrix strain hardening exponent exceeds by more than around three per cent of unity the fiber volume fraction
Fundamentals of optimum performance-based design for dynamic excitations
, Article Scientia Iranica ; Volume 12, Issue 4 , 2005 , Pages 368-378 ; 10263098 (ISSN) ; Hajirasouliha, I ; Sharif University of Technology
Sharif University of Technology
2005
Abstract
This paper presents a new method for optimization of the dynamic response of structures subjected to seismic excitation. This method is based on the concept of uniform distribution of deformation. In order to obtain the optimum distribution of structural properties, an iterative optimization procedure has been adopted. In this approach, the structural properties are modified so that inefficient material is gradually shifted from strong to weak areas of a structure, This process is continued until a state of uniform deformation is achieved. It is shown that, in general, for a MDOF structure, there exists a specific pattern for distribution of structural properties that results in an optimum...
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...
Numerical simulation of ductile crack growth under cyclic and dynamic loading with a damage-viscoplasticity model
, Article Engineering Fracture Mechanics ; Volume 99 , 2013 , Pages 169-190 ; 00137944 (ISSN) ; Eghbalian, M ; Azadi, H ; Saffar, H ; Sharif University of Technology
2013
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...
Influence of Mold Preheating and Silicon Content on Microstructure and Casting Properties of Ductile Iron in Permanent Mold
, Article Journal of Iron and Steel Research International ; Volume 18, Issue 3 , 2011 , Pages 34-39 ; 1006706X (ISSN) ; Behnam, A. A ; Sharif University of Technology
2011
Abstract
The effects of the mold preheating and the silicon content of ductile iron on the percentage of carbides, graphite nodule counts and shrinkage volume were investigated. The results showed that the percentage of carbides and the shrinkage volume decreased when the mold preheating increased. The ductile iron with the carbon equivalent of 4.45% and the silicon content of 2.5% without any porosity defects was achieved when the mold preheating was 450 °C. Increasing the silicon content in the range of 2.1%-3.3% led to the increase in graphite nodule count and graphite size and the decrease in percentage of carbides. It is due to the increase in induced expansion pressure during the graphite...
Hot tensile properties and microstructural evolution of as cast NiTi and NiTiCu shape memory alloys
, Article Materials and Design ; Volume 32, Issue 1 , January , 2011 , Pages 406-413 ; 02641275 (ISSN) ; Aboutalebi, M ; Kheirandish, S ; Taheri, A. K ; Abbasi, S. M ; Sharif University of Technology
2011
Abstract
Hot tensile properties of as cast NiTi and NiTiCu shape memory alloys were investigated by hot tensile test at temperature range of 700-1100°C using the strain rate of 0.1s-1. The NiTi alloy exhibited a maximum hot ductility at temperature range of 750-1000°C, while the NiTiCu alloy showed it at temperature range of 800-1000°C. It was found that at temperatures less than 750°C, diffusion-assisted deformation mechanism was inactive leading to semi-brittle type of failure and limited ductility in both alloys. Also it was found that at temperature range of 800-1000°C, dynamic recrystallization is dominant leading to high ductility. Likewise, the fracture surface of the specimens presenting the...
Thermally induced failure mechanism transition and its correlation with short-range order evolution in metallic glasses
, Article Extreme Mechanics Letters ; Volume 9 , 2016 , Pages 215-225 ; 23524316 (ISSN) ; Tavakoli, R ; Srolovitz, D. J ; Zhang, Y. W ; Sharif University of Technology
Elsevier Ltd
Abstract
The effect of temperature on the short-range order (SRO) structures, deformation mechanisms and failure modes of metallic glasses (MGs) is of fundamental importance for their practical applications. However, due to lack of direct structural information at the atomistic level from experiments and the absence of previous molecular dynamics (MD) simulations to reproduce experimental observations over a wide range of temperature, this issue has not been well understood. Here, by carefully constructing the atomistic models of Cu64Zr36 and Fe80W20 MGs, we are able to reproduce the major deformation modes observed experimentally, i.e. single shear banding (SB) at low temperatures, multiple...