Loading...
Search for:
toughness
0.007 seconds
Total 125 records
Microstructure Optimization of In-situ Al-Al3Ti Nanocomposite Fabricated by Mechanical Alloying & Hot Extrusion for Improving the Fracture Toughness
, Ph.D. Dissertation Sharif University of Technology ; Madaah Hosseini, Hamid Reza (Supervisor) ; Seyyed Reihani, Morteza (Supervisor)
Abstract
The aim of this research was to fabricate an in-situ Al-Al3Ti nanocomposite from pure microsized aluminum and titanium powders by mechanical alloying and hot extrusion without any usage of nanometric particles or applying secondary heat treatments. The focus of the present research was fabricating a nanocomposite material with high strength, modulus and hardness accompanied with high fracture toughness that could be comparable with aluminum alloys in terms of fracture toughness. Mechanical alloying and hot extrusion techniques were employed to produce in-situ fully dense Al-Ti composites. Platenary and high energy vibratiory mill was used to produce composites with different percent of...
Fabrication and Mechanical Properties of Alumina- Zirconia- CNT Nanocomposite Parts
, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali (Supervisor) ; Shakhesi, Saeeid (Supervisor)
Abstract
Alumina as an engineering ceramic has special characteristics such as hardness, high abrasive, fatigue and corrosion resistance but suffers from low toughness. One effective method in improving toughness is adding second phases such as tetragonal zirconia and carbon nanotubes.
In this research, alumina- zirconia nanopowders has been prepared by solution combustion method and carbon nanotubes was added to it by two different ways: 1) in situ synthesis of CNTs by CVD 2) dispersion of CNTs by heterocoagulation method. In the case of in situ synthesis of CNTs in AZ matrix, the synthesis temperature and flow ratio of N2/C2H2 gases was investigated and optimum conditions were 800̊C and 300/30,...
In this research, alumina- zirconia nanopowders has been prepared by solution combustion method and carbon nanotubes was added to it by two different ways: 1) in situ synthesis of CNTs by CVD 2) dispersion of CNTs by heterocoagulation method. In the case of in situ synthesis of CNTs in AZ matrix, the synthesis temperature and flow ratio of N2/C2H2 gases was investigated and optimum conditions were 800̊C and 300/30,...
Investigation of Hydraulic Fracturing Effect on Production of Natural Reservoir Fractures
, M.Sc. Thesis Sharif University of Technology ; Jamshidi, Saeeid (Supervisor) ; Pak, Ali (Co-Advisor)
Abstract
Hydraulic fracturing process as one of the most important ways to inhanse of production requires careful study and investigation and due to its importance has been studied for decades. The effect of this process on the production at oil and gas industry has many complexities and these complexities with the complex structure of natural gaps, would be multiplied. In this thesis effect of hydraulic fracturing operation on the production of natural fractures at naturaly fractured reservoirs from two aspects of hydraulic and geomechanics will be investigated. First we provide models for fractures network by using UDEC software after that investigate the effect of hydraulic farcture on the natural...
Fracture Toughness of Geopolymer Concrete Containing Blast Furnace Slag in Corrosive Environments
, M.Sc. Thesis Sharif University of Technology ; Toufigh, Vahab (Supervisor)
Abstract
Fracture Toughness of Geopolymer Concrete Containing Blast Furnace Slag in Corrosive Environments
An investigation on mechanical properties of Alumina-Zirconia-Magnesia spinel composite ceramics fabricated by gel-casting using solution combustion synthesized powder
, Article Materials Science and Engineering A ; Volume 587 , 2013 , Pages 336-343 ; 09215093 (ISSN) ; Faghihi Sani, M. A ; Sharif University of Technology
2013
Abstract
Addition of spinel (MgAl2O4) to Al2O3-ZrO2 composite inhibits alumina grain growth and produces phase boundaries that leads to formation of a ceramic matrix composite with special mechanical properties such as high temperature superplastic deformation. However, the room temperature mechanical properties of Alumina-zirconia-magnesia spinel composite (AZM) such as fracture toughness were rarely investigated by researchers. In this research the AZM nanocomposite powders were synthesized via the solution combustion method. The dense AZM composite samples were fabricated through gelcasting process. Phase analysis studies were performed on both powder and sintered samples and the effects of spinel...
Effect of Zirconia Content and Powder Processing on Mechanical Properties of Gelcasted ZTA Composite
, Article Transactions of the Indian Ceramic Society ; Volume 72, Issue 3 , May , 2013 , Pages 175-181 ; 0371750X (ISSN) ; Faghihi Sani, M. A ; Nojoomi, A ; Sharif University of Technology
2013
Abstract
Addition of fine zirconia particles in the alumina matrix in order to produce ZTA composite is a well-known method for improving the mechanical properties of alumina ceramics such as flexural strength and fracture toughness. Increasing homogeneity and reducing alumina grain size are two key factors for achieving proper mechanical properties in this ceramic matrix composite. In this work two batches of ZTA powder precursor were prepared through mixing of alumina and zirconia by ball milling and in situ synthesis of ZTA composite via solution combustion method. The bending strength testing samples were fabricated through gel-casting process. The effects of different powder processing methods...
The effect of water to cement ratio on fracture parameters and brittleness of self-compacting concrete
, Article Materials and Design ; Volume 50 , 2013 , Pages 267-276 ; 02613069 (ISSN) ; Kazemi, M. T ; Nikbin, I. M ; Amiri, J. V ; Sharif University of Technology
Elsevier Ltd
2013
Abstract
The paper describes an experimental research on fracture characteristics of self-compacting concrete (SCC). Three point bending tests conducted on 154 notched beams with different water to cement (w/c) ratios. The specimens were made from mixes with various w/c ratios from 0.7 to 0.35. For all mixes, common fracture parameters were determined using two different methods, the work-of-fracture method (WFM) and the size effect method (SEM). Test results showed that with decrease of w/c ratio from 0.7 to 0.35 in SCC: (a) the fracture toughness increases linearly: (b) the brittleness number is approximately doubled: (c) the effective size of the process zone cf in SEM and the characteristic...
Architecturally modified Al-DRA composites: The effect of size and shape of the DRA rods on fracture behavior
, Article Journal of Materials Science ; Volume 45, Issue 11 , June , 2010 , Pages 2852-2861 ; 00222461 (ISSN) ; Farokhzadeh, K ; Bagheri, R ; Seyed Reihani, S. M ; Sharif University of Technology
2010
Abstract
Architectural modification of aluminum matrix composites is considered as an efficient method to improve fracture toughness. Al-DRA (Al-Al/SiC/20 p) composites were fabricated via "powder extrusion-casting- ingot extrusion" route with structures similar to that of reinforced concrete, so that DRA rods were surrounded by unreinforced aluminum. The effects of variation in shape, size, and number of DRA rods on fracture behavior of Al-DRA composites were investigated. Composites containing DRA rods with hexagonal cross-section exhibited higher resistance to crack initiation and growth, in comparison to those containing circular rods. In the case of hexagonal rods, increasing the number of rods...
Loading rate-induced transition in toughening mechanism of rubber-modified epoxy
, Article Journal of Macromolecular Science, Part B: Physics ; Volume 49, Issue 3 , 2010 , Pages 602-614 ; 00222348 (ISSN) ; Khademi, V ; Bagheri, R ; Motamedi, P ; Kouchakzadeh, M. A ; Haddadpour, H ; Sharif University of Technology
Abstract
The effect of loading rate on toughening mechanisms of rubber-modified epoxy resin was investigated using amine-terminated butadiene acrylonitrile (ATBN) rubber. Rubber-modified samples were tested at various loading rates in the range of 1-1000 mm/min. At low loading rates, modified resin exhibited a high fracture toughness, which decreased by increasing the rate of loading. At higher loading rate a transition region was observed, where the fracture toughness did not change noticeably with increasing the loading rate. Beyond the transition region, the resin fracture toughness dropped dramatically to the level of unmodified epoxy. Fractography of the damage zone showed different toughening...
Toughening of epoxy nanocomposites: Nano and hybrid effects
, Article Polymer Reviews ; Volume 56, Issue 1 , 2016 , Pages 70-112 ; 15583724 (ISSN) ; Mai, Y. W ; Bagheri, R ; Pearson, R. A ; Sharif University of Technology
Taylor and Francis Inc
2016
Abstract
In this paper, we review recent progress made in the field of epoxy-based binary and ternary nanocomposites containing three-, two-, and one-dimensional (i.e., 3D-, 2D-, and 1D) nano-size fillers with a special focus on their fracture behaviors. Despite investigations conducted so far to evaluate the crack-resistance of epoxy nanocomposites and attempts made to clarify the controlling toughening mechanisms of these materials, some questions remain unsolved. It is shown that silica nanoparticles can be as effective as rubber particles in improving the fracture toughness/energy; but incorporation of carbon nanotubes (CNTs) or clay platelets in epoxy matrices delays crack growth only modestly....
Improvement of dry sliding tribological properties of polyamide 6 using diamond nanoparticles
, Article Tribology International ; Volume 115 , 2017 , Pages 370-377 ; 0301679X (ISSN) ; Shojaei, A ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
In the present study, it was revealed that incorporation of nanodiamond containing carboxylic group (ND-COOH) decreased considerably specific wear rate (∼30%) and COF (∼60%) of polyamide 6 (PA6) at 1 wt% loading. Compared with ND-COOH, amino functionalized ND enhanced further wear performance of PA6 which was associated with its finer dispersion as well as greater influence on the improvement of mechanical properties, toughness and crystallinity of PA6. Surface temperature increment caused by frictional heat was in close agreement with COF and wear characteristics of the samples. Optical microscopy images revealed that NDs promote the abrasive wear mechanism in PA6/ND composites. © 2017...
Preparation of mullite-TiB2-CNTs hybrid composite through spark plasma sintering
, Article Ceramics International ; Volume 45, Issue 13 , 2019 , Pages 16288-16296 ; 02728842 (ISSN) ; Ghasali, E ; Moradi, M ; Derakhshandeh, M. R ; Alizadeh, M ; Shahedi Asl, M ; Ebadzadeh, T ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
A near fully dense mullite-TiB2-CNTs hybrid composite was prepared successfully trough spark plasma sintering. 1 wt%CNT and 10 wt%TiB2 were mixed with nano-sized mullite powders using a high energy mixer mill. Spark plasma sintering was carried out at 1350 °C under the primary and final pressure of 10 MPa and 30 MPa, respectively. XRD results showed mullite and TiB2 as dominant crystalline phases accompanied by tiny peaks of alumina. The microstructure of prepared composites demonstrated uniform distribution of TiB2 reinforcements in mullite matrix without any pores and porosities as a result of near fully densified spark plasma sintered composite. The fracture surface of composite revealed...
Effect of rubber particle cavitation on the mechanical properties and deformation behavior of high-impact polystyrene
, Article Journal of Applied Polymer Science ; Volume 104, Issue 2 , 2007 , Pages 1110-1117 ; 00218995 (ISSN) ; Zokaei, S ; Bagheri, R ; Sharif University of Technology
2007
Abstract
Rubber particle cavitation has been the focus of many investigations because it dramatically affects the mechanical properties of polymeric blends. In this work, the effect of rubber particle cavitation on the mechanical behavior of high-impact polystyrene was studied. The extent of cavitation in rubber particles was varied via different thermal contraction/expansion cycles in the range of -100 to 23°C. Tensile, creep, and Charpy impact tests were conducted to evaluate the effects of the degree of cavitation on the general mechanical properties. The notch-tip damage zone and deformation micromechanisms were also investigated by a transmitted optical microscopy technique to reveal the effects...
Comparison of experimental and analytical fracture toughness values of SiCP/QE22 Mg-alloy composites
, Article Materials and Design ; Volume 27, Issue 6 , 2006 , Pages 520-525 ; 02641275 (ISSN) ; Purazrang, K ; Sharif University of Technology
2006
Abstract
In the present work, the fracture toughness data generated on the QE22 magnesium alloy as the matrix alloy and SiC particles reinforced composites using the short rod standard specimens. The short rod specimens of 18 mm diameter were prepared from the extruded rods in the extrusion direction. The fracture toughness values are primarily evaluated experimentally and then analytically by using mathematical methods. The suitability of these methods to predict this property was also discussed. Results showed that the incorporation of the SiC particles with three different shapes (i.e. sharp, blocky and round) decreases in general the fracture toughness of the QE22 Mg-alloy. This effect is...
Micro-scale evolution of mechanical properties of glass-ceramic sealant for solid oxide fuel/electrolysis cells
, Article Ceramics International ; Volume 47, Issue 3 , 2021 , Pages 3884-3891 ; 02728842 (ISSN) ; Malzbender, J ; Groß Barsnick, S. M ; Abdoli, H ; Kokabi, A. H ; Faghihi Sani, M. A ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The structural integrity of the sealant is critical for the reliability of solid oxide cells (SOCs) stacks. In this study, elastic modulus (E), hardness (H) and fracture toughness (KIC) of a rapid crystallizing glass of BaO–CaO–SiO2 system termed “sealant G” are reported as determined using an indentation test method at room temperature. A wide range of indentation loads (1 mN–10 N) was used to investigate the load-dependency of these mechanical properties. Values of 95 ± 12 GPa, 5.8 ± 0.2 GPa and 1.15 ± 0.07 MPa m0.5 were derived for E, H and KIC using the most suitable indentation loads. An application relevant annealing treatment of 500 h at 800 °C does not lead to a significant change of...
Post-consumer recycled high density polyethylene/polypropylene blend with improved overall performance through modification by impact polypropylene copolymer: morphology, properties and fracture resistance
, Article Polymer International ; Volume 70, Issue 12 , 2021 , Pages 1701-1716 ; 09598103 (ISSN) ; Sharifi, H ; Sharif University of Technology
John Wiley and Sons Ltd
2021
Abstract
The effect of an impact polypropylene copolymer (IPC) having excellent stiffness–toughness balance on the microstructure and properties of a blend comprising 80 wt% recycled high density polyethylene (rHDPE) and 20 wt% recycled isotactic polypropylene (rPP) was studied. Morphological observations revealed improved interfacial interactions, a finer dispersion state and a more homogeneous phase morphology upon IPC incorporation into the blend up to 20 wt%. Flexural modulus, flexural strength, tensile strength and tensile ductility were steadily increased with IPC loading, and exhibited 13%, 14%, 35% and 520% improvement at 20 wt% IPC. A monotonic rise in Izod impact energy, accompanied by a...
Investigation of interfacial and mechanical properties of alumina-coated steel fiber reinforced geopolymer composites
, Article Construction and Building Materials ; Volume 288 , 2021 ; 09500618 (ISSN) ; Nemati, A ; Khodabandeh, A. R ; Baghshahi, S ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
In this study, alumina coated steel reinforced geopolymer composites were successfully fabricated and their interfacial and mechanical properties were investigated. The fiber–matrix interface characteristics were assessed using single-fiber push-out and water contact angle experiments as well as SEM-EDS analysis. Finally, the role of alumina coating on the compressive, flexural and toughness of the geopolymer composites was investigated. The morphological studies revealed that alumina coating on steel can chemically bonded and microstructurally integrated with the surrounding matrix. The push-out test showed that the interfacial shear strength was increased approximately 150% in composites...
Effect of environmental conditions on fracture behavior of solder joints
, Article Theoretical and Applied Fracture Mechanics ; Volume 112 , 2021 ; 01678442 (ISSN) ; Nourani, A ; Karimi, M ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Double cantilever beam (DCB) specimens were prepared according to standard surface mount technology (SMT). The samples were stored inside an environmental chamber at two different relative humidity values (i.e. 40 or 100%) for either 2 or 4 h. Then they were aged at 25 °C, 75 °C or 125℃ for the same time. Finally, after being cooled to room temperature, fracture tests were performed under mode-I loading conditions at a strain rate of 0.03 s−1 at room temperature. Storage time did not have a significant effect on the fracture behavior. The fracture load and energy of the solder joints decreased significantly when the temperature was increased from 25 to 75℃. By further increase in the...
Determination of the fracture parameters of concrete with improved wedge-splitting testing
, Article Engineering Fracture Mechanics ; Volume 276 , 2022 ; 00137944 (ISSN) ; Du, C ; Ghaemian, M ; Zhao, W ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Considering the quasi-brittle mechanical properties of concrete, wedge-splitting tests are employed and improved in this paper to study the fracture behaviour of concrete. A novel wedge-splitting device is designed by fixing ten springs on the force transmission component. The adaptive spring force can be imposed on top of a concrete specimen to retard the brittle fracture process. With the proposed wedge-splitting test design for notched cuboid specimens, the complete load–strain/CMOD curves of concrete can be generated directly. The fracture toughness and the fracture energy can be calculated easily without numerical fitting using the double-K fracture model. The descending branch of the...
Atomistic simulations of mechanical properties and fracture of graphene: A review
, Article Computational Materials Science ; Volume 210 , 2022 ; 09270256 (ISSN) ; Kouchakzadeh, M. A ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Material properties and fracture characteristics are among the most prominent parameters that should be considered for a wide range of graphene applications. This article reviews recent advances in theoretical studies on the mechanical properties and fracture behaviors of graphene, focusing on the effect of various simulation models. Most studies investigated single-layer graphene sheets (SLGSs) under uniaxial tensile tests using different common interatomic potentials, particularly AIREBO. Although researchers have examined a similar problem, specifically for pristine graphene, the differences in the reported values are considerable. These discrepancies are most evident in fracture...