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Investigating the Possibility of Elimination of Nickel and Replacement of Copper and Silicon Instead of that in A336 Casting Alloy Used in Automotive Pistons
, M.Sc. Thesis Sharif University of Technology ; Varahram, Naser (Supervisor)
Abstract
In this research the effect of Si, Cu and Ni alloying elements on the structure and mechanical properties of the A336 alloy is investigated. Expriments were done in two situations, casting and heat treated and the results for all samples with different amount of alloying elements are compared and the effect of heat treating is also investigated. Results show that with increasing the amount of Si and Cu and decreasing the amount of Ni strength and hardness of the cast alloy are 134 MPa and 65 HB and they increase to 187 MPa and 89 HB in heat treated alloy. The elongation and coefficient of linear expansion are decreased from 2.3% and 21.94 μm/m.K to 1.1% and 21.62 μm/m.K. Also the T6 heat...
First Principles Studies of Mechanical, Physical, and Electronic Properties of a-Si - also, Diffusion of a Self-interstitial Atom in an Ultra-thin fcc Film Via Lattice Statics
, Ph.D. Dissertation Sharif University of Technology ; Mohammadi Shodja, Hossein (Supervisor)
Abstract
By employing first principles density functional theory-based (DFT) molecular dynamics (MD), the influences of dangling and floating bonds as well as distorted tetrahedral bonds are studied on the mechanical, physical, and electronic properties of amorphous Si (a-Si). For further examination of the effects of these geometrical defects, two distinct amorphous samples, namely as-quenched and annealed are generated and examined. To verify the validity of the representative cells, the obtained radial distribution function, pair correlation function, and cohesive energy are compared with those corresponding results presented in the literature. Moreover, the surface energy is calculated at final...
Investigation of Microstructure and Fracture Behavior of Similar and Dissimilar Dual Phase Steels and Martensitic Steel Spot Resistance Welding
, M.Sc. Thesis Sharif University of Technology ; Pouranvari, Majid (Supervisor) ; Movahhedi, Mojtaba (Supervisor)
Abstract
The new generation of advanced high-strength steels use in the automotive industry cause resistance spot welding study and their failure characteristics during static and dynamic loading are important. In this study, the relationship among microstructure, failure mode and mechanical properties are investigate during similar and dissimilar DP980 and MS1400 jointing advanced high-strength steels resistance spot welding. To search for micro and macro structural changes, the optical microscope, stereographic microscope and scanning electron microscope were used. Micro-hardness test, tensile shear test and Cross tension test to evaluate the mechanical properties were conducted. As well as...
Bonding Feasibility, Mechanical Properties and Formability of Three-layered St/AZ31/St Composites Fabricated by Roll Bonding
, M.Sc. Thesis Sharif University of Technology ; Akbarzadeh, Abbas (Supervisor)
Abstract
New materials as hybrid materials or laminate composites, due to combination of many properties, can be used in many industries. The aim of this research is bonding of three-layered St/AZ31/St composite by roll-bonding process. The roll-bonding process was performed at three preheating temperatures, 340, 400 and 450 ⁰C, with thickness reduction of 30 to 68% and different thicknesses of intermediate layer (AZ31). In order to improve the bonding strength, the as-rolled specimens were annealed at constant temperature of 375 ⁰C. For evaluation of bond strength and investigating the formation of a diffusion layer, the results of peel test and microscopic images were studied. Tensile specimens...
Performance Evaluation of Cold-Recycled Mixtures
, M.Sc. Thesis Sharif University of Technology ; Sabouri, Mohammad Reza (Supervisor)
Abstract
This study aims to investigate the mechanical properties and performance of cold recycled asphalt mixtures (CRM). So far, several methods have been proposed for designing CRMs, which are mostly based on the volumetric and mechanical properties of the mixtures. In the meantime, few researches have considered performance of those mixes. The main approach of current research is to evaluate and enhance performance characteristics of CRMs regarding common distresses including early-raveling, moisture damage, fatigue cracking by an appropriate additive.Raveling and Cantabro tests were employed to evaluate the resistance of CRM against abrasion and semicircular bending test (SCB) and crack tolerate...
Microstructure/Properties Relationship in Lead Free Solder Joint Reinforced with Graphene Nanosheets
, M.Sc. Thesis Sharif University of Technology ; Kokabi, Amir Hossein (Supervisor) ; Movahedi, Mojtaba (Supervisor)
Abstract
Development of electronic industries, compression of electronic equipment, and removing lead from electronic circuits for environmental reasons, a significant challenge was created in the design and development of tin-based lead-free solders with physical and mechanical properties close to old tin-lead alloys. In this regard, the set of Sn-Ag-Cu alloys with eutectic composition and related compounds have been proposed as alloys to replace Sn-Pb solders. As a lead-free solder alloy, low melting point (≈217℃), high reliability of joints, and compatibility with various fluxes are among the properties of this category of alloys. In order to improve the mechanical properties of the joint...
Investigation of membrane preparation condition effect on the PSD and porosity of the membranes using a novel image processing technique
, Article Journal of Applied Polymer Science ; Volume 131, Issue 4 , 15 February , 2014 ; ISSN: 00218995 ; Samimi, A ; Mousavi, S. A ; Bozarjamhari, R. B ; Sharif University of Technology
Abstract
A totally computerized image processing program package is developed to analyze the SEM images of membrane surface and cross-section. Pore size distribution and porosity of the fabricated membranes are determined using the proposed image processing procedure. Furthermore, effect of coagulation bath temperature on the morphology and mechanical properties (such as tensile strength, strain break, tensile energy absorbent, and tensile stiffness) of Polysulfone (PSf) membranes are investigated. The results reveal that the mechanical properties are higher when N-methyl-2-pyrrolidone (NMP) is used as solvent. Also, an increase in the coagulation bath temperature caused a monotonous increase in the...
On the failure behavior of highly cold worked low carbon steel resistance spot welds
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Vol. 45, issue. 3 , Oct , 2014 , p. 1376-1389 ; 10735623 ; Kazeminezhad, M ; Kokabi, A. H ; Sharif University of Technology
Abstract
Highly cold worked (HCW) low carbon steel sheets with cellular structure in the range of 200 to 300 nm are fabricated via constrained groove pressing process. Joining of the sheets is carried out by resistance spot welding process at different welding currents and times. Thereafter, failure behavior of these welded samples during tensile-shear test is investigated. Considered concepts include; failure load, fusion zone size, failure mode, ultimate shear stress, failure absorbed energy, and fracture surface. The results show that HCW low carbon steel spot welds have higher failure peak load with respect to the as-received one at different welding currents and times. Also, current limits for...
The effect of melt quality and filtering on the Weibull distributions of tensile properties in Al-7%Si-Mg alloy castings
, Article Materials Science and Engineering A ; Volume 579 , 2013 , Pages 64-70 ; 09215093 (ISSN) ; Davami, P ; Kim, S. K ; Tiryakioglu, M ; Sharif University of Technology
2013
Abstract
The effects of melt quality and the placement of a filter in the filling system on Weibull distributions of tensile strength and elongation of Al-7%Si-Mg alloy castings were investigated. Three different combinations of melt quality and filtering were used: (a) unstirred, with filter in the filling system, (b) stirred to produce and entrain surface oxide films with no filter in the filling system to emulate poor initial melt preparation and melt handling, and (c) stirred and with a filter placed in the filling system. The results showed that the highest elongation and tensile strength values were obtained from the unstirred, filtered condition and lowest values were from stirred and...
An enhanced continuum modeling of the ideal strength and the angle of twist in tensile behavior of single-walled carbon nanotubes
, Article Journal of Applied Physics ; Volume 114, Issue 5 , 2013 ; 00218979 (ISSN) ; Shodja, H. M ; Sharif University of Technology
2013
Abstract
By utilizing the fourth-, sixth-, eighth-, and tenth-order elastic moduli tensors of graphene a highly nonlinear constitutive model for it is proposed. Subsequently, an accurate analytical formulation, describing the entire tensile behavior of single-walled carbon nanotubes (SWCNTs) from their initial unloaded states through their ideal strengths, is made possible. The angle of twist which is a critical parameter that varies with the tensile loading is also calculated within the current framework. The estimated value of the theoretical strength of SWCNTs with different chiralities and radii as well as that of graphene ranges from 0.39 to 0.44 TPa. Some peculiarities associated with chirality...
Evaluation of dissimilar welds of 5083-H12 and 6061-T6 produced by friction stir welding
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 44, Issue 8 , 2013 , Pages 3697-3707 ; 10735623 (ISSN) ; Kolahgar, S ; Dariani, B. M ; Dehghani, K ; Sharif University of Technology
2013
Abstract
In the present study, the dissimilar aluminum alloys of 5083-H12 and 6061-T6 were joined by friction stir welding (FSW). Then, the design of experiments (DOE), the Box-Benken method, and the response surface methodology (RSM) were used to optimize the effective parameters of the FSW process. The optimized parameters that led to the maximum tensile strength in dissimilar friction stir welded sheets were determined. The predicted results were then compared with those measured experimentally. The results show that there is good agreement between the predicted and measured amounts. By applying the limit dome height (LDH) test, the formability of friction stir welded sheets was studied. During...
Elastic properties of actin assemblies in different states of nucleotide binding
, Article Cellular and Molecular Bioengineering ; Volume 5, Issue 1 , 2012 , Pages 1-13 ; 18655025 (ISSN) ; Kazemi, M. T ; Sharif University of Technology
Abstract
In this paper, the elastic properties of monomeric actin (G-actin) and the trimer nucleus (G-actin trimer) in different states of nucleotide binding are estimated using steered molecular dynamic (SMD) simulations. Three nucleotide binding states are considered: ADP- and ATP-bound actin and nucleotide-free actin assemblies. Our results show that nucleotide binding and the corresponding changes in structure have significant effects on the mechanical behaviors of actin assemblies. Simulations reveal that the deformation behavior of G-actin monomers is generally elastic up to engineering strains of 16 and 40% in the tension and shear tests, respectively. In addition, the G-actin trimers react...
Binary and ternary blends of high-density polyethylene with poly(ethylene terephthalate) and polystyrene based on recycled materials
, Article Polymers for Advanced Technologies ; Volume 22, Issue 5 , 2011 , Pages 690-702 ; 10427147 (ISSN) ; Shojaei, A ; Bagheri, R ; Sharif University of Technology
Abstract
Binary blends of recycled high-density polyethylene (R-HDPE) with poly(ethylene terephthalate) (R-PET) and recycled polystyrene (R-PS), as well as the ternary blends, i.e. R-HDPE/R-PET/R-PS, with varying amounts of the constituents were prepared by twin screw extruder. The mechanical, rheological, thermal, and scanning electron microscopy (SEM) analyses were utilized to characterize the samples. The results revealed that both R-HDPE/R-PET and R-HDPE/R-PS blends show phase inversion but at different compositions. The R-PET was found to have much higher influence on the properties enhancement of the R-HDPE compared to R-PS, but at the phase inverted situation, a significant loss in the tensile...
Effect of solidification mechanism on microstructure and mechanical properties of joint in TLP bonded Al2024-T6 alloy
, Article Science and Technology of Welding and Joining ; Volume 16, Issue 2 , Nov , 2011 , Pages 174-180 ; 13621718 (ISSN) ; Ekrami, A ; Kokabi, A. H ; Sharif University of Technology
2011
Abstract
Transient liquid phase (TLP) bonding of Al2024-T6 alloy, using gallium (Ga) interlayer, has been investigated. Bonding process was carried out at 470°C for 6 min, and homogenising temperature and time were 495°C and 2 h respectively. Conventional TLP bonding using Ga interlayer was not an appropriate method for joining of Al2024. In this method, the boundary between two Al2024 specimens was not fully eliminated during bonding because of solidification with planar front. In addition, bonding zone was depleted of copper, and as a result, tensile and shear strength of joint decreased to 200 and 110 MPa respectively. TLP bonding under temperature gradient offered very good results in bonding of...
Bond strength and mechanical properties of three-layered St/AZ31/St composite fabricated by roll bonding
, Article Materials and Design ; Volume 88 , 2015 , Pages 880-888 ; 02641275 (ISSN) ; Akbarzadeh, A ; Sharif University of Technology
2015
Abstract
The aim of this research is bonding of three-layered St/AZ31/St composite by roll-bonding process. The roll-bonding process was performed at three preheating temperatures, 340, 400 and 450°C, with thickness reduction of 30 to 68% and different thicknesses of intermediate layer (AZ31). In order to improve the bonding strength, the as-rolled specimens were annealed at constant temperature of 375°C. For evaluation of bond strength and investigating the formation of a diffusion layer, the results of peel test and microscopic images were studied. Tensile specimens were prepared along the rolling direction to measure the mechanical properties of the composite. The results showed that by increasing...
Contribution of ordered-inordered phenomenon within the interphase region toward increasing elastic modulus in CNT/polymer nanocomposites
, Article Materials Science and Technology Conference and Exhibition 2015, MS and T 2015, 4 October 2015 through 8 October 2015 ; Volume 1 , October , 2015 , Pages 595-602 ; 9781510813939 (ISBN) ; Goodarzi Hosseinabadi, H ; NACE International ; Sharif University of Technology
Association for Iron and Steel Technology, AISTECH
2015
Abstract
Exceptional mechanical properties of carbon nanotubes (CNTs) such as high elastic modulus, stiffness and tensile strength have made them as promising reinforcement in polymer nanocomposite systems. The characteristics of CNTs/polymer interphase region directly affect the efficiency of nanotubes for improving the nanocomposite mechanical properties. In this work, the influence of chains alignment within the interphase region on elastic response of the nanocomposite is assessed using a novel ordered-inordered approach. The applicability of the presented approach is examined by implementing the approach on a series of reported data available in the literature. The effects of CNT content,...
An investigation into microstructures and mechanical properties of AA7075-T6 during friction stir welding at relatively high rotational speeds
, Article Journal of Materials Engineering and Performance ; Volume 19, Issue 9 , December , 2010 , Pages 1256-1263 ; 10599495 (ISSN) ; Serajzadeh, S ; Sharif University of Technology
2010
Abstract
In this study, microstructural changes and mechanical properties during friction stir welding of AA7075-T6 have been investigated. Friction stir welding at relatively high rotational speeds ranging from 1000 to 1400 rpm and longitudinal speeds in the range of 40 to 80 mm/min have been performed and then microstructures and mechanical properties of the weldments have been studied. The results show that the rotational and longitudinal speeds have a significant effect on the microstructures as well as the mechanical behavior of the welded material while a fine grain structure is produced at higher ratio of rotational speed to longitudinal speed. On the other hand, for a given longitudinal...
Accumulative spin-bonding (ASB) as a novel SPD process for fabrication of nanostructured tubes
, Article Materials Science and Engineering A ; Volume 528, Issue 1 , November , 2010 , Pages 180-188 ; 09215093 (ISSN) ; Akbarzadeh, A ; Sharif University of Technology
2010
Abstract
A novel SPD process for manufacturing of high strength tubes and cylinders by accumulative spin-bonding (ASB) is proposed. It is demonstrated that due to incremental deformation in this process, high strain rate without considerable temperature rise is achieved. This is accompanied with a high value of Zener-Hollomon parameter as a characteristic of this SPD process. ASB was applied to a commercially pure aluminum up to four cycles and its effects on the microstructure and mechanical properties were examined by optical microscopy, TEM, EBSD, microhardness and tension tests. The results show that ultra-fine grains are developed during the process by formation of subgrains at early stages...
Upset resistance welding of carbon steel to austenitic stainless steel narrow rods
, Article Journal of Materials Engineering and Performance ; Volume 25, Issue 11 , 2016 , Pages 4902-4910 ; 10599495 (ISSN) ; Movahedi, M ; Mohammadkamal, H ; Sharif University of Technology
Springer New York LLC
Abstract
Effects of welding current (at the range of 2-4 kA) on the microstructure and mechanical properties of upset resistance welds of AISI-1035 carbon steel to AISI-304L austenitic stainless steel rods were investigated. The results showed that the joint strength first increased by raising the welding current up to 3 kA and then decreased beyond it. Increasing trend was related to more plastic deformation, accelerated diffusion, reduction of defects and formation of mechanical locks at the joint interface. For currents more than 3 kA, decrease in the joint strength was mainly caused by formation of hot spots. Using the optimum welding current of 3 kA, tensile strength of the joint reached to ~76%...
Experimental and numerical survey on tensile fracture of polycrystalline graphite using design of experiments
, Article Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications ; Volume 230, Issue 1 , 2016 , Pages 151-159 ; 14644207 (ISSN) ; Khodadad, A ; Rezaeibana, R ; Sharif University of Technology
SAGE Publications Ltd
Abstract
A new test specimen for a tensile test of industrial graphite is introduced using experiment and finite element results. The most influencing factors on the tensile strength of the test specimens are considered and the number of tests, which are necessary to optimize the tensile strengths are reduced based on the design of experiment using the Taguchi method and the effects of all factors on strength of test samples are studied. Comparison of the predicted strengths based on the Taguchi approach with the measured experimental results and finite element analysis shows a good correlation between them. In addition, results show that the new introduced specimen makes a 33% increase in the...