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Dynamic strain aging of a commercial Al-Mg-Si-Cu alloy during equal channel angular extrusion process
, Article Journal of Alloys and Compounds ; Volume 502, Issue 1 , July , 2010 , Pages 59-62 ; 09258388 (ISSN) ; Karimi Taheri, A ; Vaseghi, M ; Sharif University of Technology
2010
Abstract
In this research, the occurrence of dynamic strain aging (DSA) phenomenon during equal channel angular extrusion (ECAE) of a commercial air cooled Al-Mg-Si-Cu alloy is investigated. In order to detect the negative strain rate sensitivity behaviour associated with DSA, samples were ECAE-ed at various temperatures and strain rates. Subsequently, the extruded billets were subjected to mechanical and physical tests and it was found that at a certain ECAE temperature range there is a critical strain rate above which DSA occurs. The implication of the results to strengthening of dilute solid solutions is discussed
The effect of aging on the fracture characteristics and ductility of self-compacting concrete
, Article Materials and Design ; Volume 55 , March 2014 , Pages 937-948 ; Kazemi, M. T ; Nikbin, I. M ; Vaseghi Amiri, J ; Sharif University of Technology
March 2014
Abstract
Good knowledge of fracture parameters and cracking behavior of self-compacting concrete (SCC) from early ages until the SCC becomes mature plays an important role in design of SCC structure and also in evaluation of durability and consequently prevention of damage. In this paper, variation of fracture parameters and corresponding ductility behavior of SCC at different ages (e.g. 3days, 7days, 28days and 90days) for SCC mixes with w/c ratios of 0.45 and 0.65 have been experimentally studied. To do so, three-point bending tests were carried out on 120 notched beams. Then, size effect method (SEM) and work of fracture method (WFM) were applied to interpret the results. The results of analyses...
Speech accent profiles: Modeling and synthesis
, Article IEEE Signal Processing Magazine ; Volume 26, Issue 3 , 2009 , Pages 69-74 ; 10535888 (ISSN) ; Yan, Q ; Ghorshi, A ; Sharif University of Technology
2009
Abstract
A discussion regarding speech accents will be given while describing a set of statistical signal processing methods for the modeling, analysis, synthesis, and morphing of English language accents. Accent morphing deals with the changing of the accent of a speech to a different accent. Accent itself is a distinctive pattern of pronunciation of speech within a community of people who belong to a national, geographic, or socioeconomic grouping. Then, the signal processing methodology for speech accent processing will be reviewed while the concept of an accent profile has been presented
Development of Nanostructural Al-Mg-Si Alloys using ECAE and Ageing Processes
, Ph.D. Dissertation Sharif University of Technology ; Karimi Taheri, Ali (Supervisor)
Abstract
The manufacture of ultra high strength materials has always been a target for aerospace and transportation industries. Currently, the limitation of energy resources even makes this goal more serious. Nowadays, more than 50% of total extrusion products are made from Al alloys and around 90% of them are the 6000 series alloys. Therefore, regarding to high strength, low weight, and hardening aluminum AA6000 alloys capabilities can play a major role in fulfilling this task. Over the last decade, a number of techniques collectively referred to as severe plastic deformation (SPD), have emerged as a promising approach for the production of bulk ultrafine-grained (UFG) nano-structured materials....
Evaluation of the effect of maximum aggregate size on fracture behavior of self compacting concrete
, Article Construction and Building Materials ; Vol. 55 , 2014 , pp. 202-211 ; ISSN: 09500618 ; Kazemi, M. T ; Vaseghi Amiri, J ; Nikbin, I. M ; Rabbanifar, S ; Rahmani, E ; Sharif University of Technology
2014
Abstract
This paper presents and discusses the effect of maximum size of coarse aggregate on fracture characteristics and brittleness of self-compacting concrete (SCC). Based on an experimental program, a series of three point bending tests were carried out on 86 notched beams, as recommended by RILEM. For all mixes, the parameters were analyzed by the work-of-fracture method (WFM) and by the size effect method (SEM) and consequently a correlation between these methods was obtained which is used to calibrate cracking numerical models. Test results showed that with increase of size of coarse aggregate, (a): fracture energies of GF in WFM and Gf in SEM increase which may be explained by the change in...
An electron back-scattered diffraction study on the microstructure evolution of severely deformed aluminum AI6061 alloy
, Article IOP Conference Series: Materials Science and Engineering ; Vol. 63, Issue. 1 , 30 June- 4 July , 2014 ; ISSN: 17578981 ; Taheri, A. K ; Kim, H. S ; Sharif University of Technology
2014
Abstract
In this paper dynamic strain ageing behavior in an Al-Mg-Si alloy related to equal channel angular pressing (ECAP) was investigated. In order to examine the combined plastic deformation and ageing effects on microstructure evolutions and strengthening characteristics, the Al6061 alloy were subjected to φ=90° ECAP die for up to 4 passes via route Bc at high temperatures. For investigating the effects of ageing temperature and strain rate in ECAP, Vickers hardness tests were performed. The combination of the ECAP process with dynamic ageing at higher temperatures resulted in a significant increase in hardness. The microstructural evolution of the samples was studied using electron...
Upper bound analysis of deformation and dynamic ageing behavior in elevated temperature equal channel angular pressing of Al-Mg-Si alloys
, Article Metals and Materials International ; Volume 16, Issue 3 , June , 2010 , Pages 363-369 ; 15989623 (ISSN) ; Karimi Taheri, A ; Seop Kim, H ; Sharif University of Technology
2010
Abstract
In the present study, the plastic deformation and dynamic strain ageing behavior of Al-6082 (Al-Mg-Si) alloy treated with elevated temperature equal channel angular pressing (ECAP) were investigated using upper bound analyses. Tensile tests were carried out over wide ranges of temperature and strain rate in order to evaluate the dynamic ageing conditions. ECAP processing was then experimentally performed at temperatures from room temperature up to 200 °C under various strain rates ranging between 10-4 s-1 and 10-1 s-1 . The upper bound analysis solutions and the experimental results are comparable. A theoretical dynamic ageing region was found to be in the temperature range of 90 °C to 260...
Evaluation of Soil Contribution to Seismic Response of Soil-Structure Systems Using Recorded Data During Small-scale Earthquakes
, M.Sc. Thesis Sharif University of Technology ; Ghannad, Mohammad Ali (Supervisor)
Abstract
Soil-Structure Interaction (SSI) has been widely studied theoretically and experimentally due to its importance effects on the responses of structures. In experimental studies, acceleration responses recorded during previous earthquakes are generally used in order to investigate the contribution of underlying soil to the response of soil-structure systems. Since acceleration responses are affected by higher modes of vibration, studying the effect of SSI on dynamic characteristics of higher modes are of great importance in these studies. However recent theoretical studies indicate that the influence of SSI on the higher vibrational modes is very much dependent on the behavioral model (bending...
A comprehensive investigation into the effect of aging and coarse aggregate size and volume on mechanical properties of self-compacting concrete
, Article Materials and Design ; Vol. 59, issue , 2014 , pp. 199-210 ; ISSN: 10263098 ; Beygi, M. H. A ; Kazemi, M. T ; Vaseghi Amiri, J ; Rahmani, E ; Rabbanifar, S ; Eslami, M ; Sharif University of Technology
2014
Abstract
The popularity of self-compacting concrete (SCC), as an innovative construction materials in concrete industry, has increased all over the world in recent decades. SCC offers a safer construction process and durable concrete structure due to its typical fresh concrete behavior which is achieved by SCC's significantly different mixture composition. This modification of mix composition may have significant effect on the hardened mechanical properties of SCC as compared to normal vibrated concrete (NVC). Therefore, it is necessary to know whether the use of all rules and relations that have been formulated for NVC in current design codes based on years of experience are also valid for SCC....
Effect of coarse aggregate volume on fracture behavior of self compacting concrete
, Article Construction and Building Materials ; Volume 52 , 15 February , 2014 , Pages 137-145 ; ISSN: 09500618 ; Beygi, M. H. A ; Kazemi, M. T ; Vaseghi Amiri, J ; Rahmani, E ; Rabbanifar, S ; Eslami, M ; Sharif University of Technology
2014
Abstract
This paper presents the effect of volume of coarse aggregate on fracture characteristics of self- compacting concrete (SCC). Based on an experimental programme, a series of three point bending tests were carried out on 58 notched beams. SCC was prepared with coarse aggregate in varying percentages of 30%, 40%, 50% and 60% (as the percentage of the total aggregate volume). For all mixes, the fracture parameters were analyzed by the work-of- fracture method (WFM) and by the size effect method (SEM) to obtain a suitable correlation between these methods which is used to calibrate fracture numerical models. The results showed that with decrease of volume of coarse aggregate from 60% to 30% in...
A comprehensive investigation into the effect of water to cement ratio and powder content on mechanical properties of self-compacting concrete
, Article Construction and Building Materials ; Vol. 57 , April , 2014 , pp. 69-80 ; ISSN: 09500618 ; Beygi, M. H. A ; Kazemi, M. T ; Vaseghi Amiri, J ; Rabbanifar, S ; Rahmani, E ; Rahimi, S ; Sharif University of Technology
2014
Abstract
Self compacting concrete (SCC), as an innovative construction material in concrete industry, offers a safer and more productive construction process due to favorable rheological performance which is caused by SCC's different mixture composition. This difference may have remarkable influence on the mechanical behavior of SCC as compared to normal vibrated concrete (NVC) in hardened state. Therefore, it is vital to know whether the use of all assumptions and relations that have been formulated for NVC in current design codes are also valid for SCC. Furthermore, this study presents an extensive evaluation and comparison between mechanical properties of SCC using current international codes and...
Deformation characteristics evaluation of modified equal channel angular pressing processes
, Article Materials Transactions ; Volume 51, Issue 1 , 2010 , Pages 46-50 ; 13459678 (ISSN) ; Nagasekhar, A. V ; Yoo, J. H ; El Aal, M. I. A ; Vaseghi, M ; Kim, H. S ; Sharif University of Technology
2010
Abstract
In current studies, equal channel angular pressing process (ECAP) and modified ECAP processes are simulated under ideal conditions to compare the deformation characteristics. The deformation behaviour is more complicated and the strain induced during the processes is highly non-uniform in the modified ECAP processes except in the equal channel multi-angular pressing (ECMAP) process with Route C. The strain homogeneity is more of a possibility with ECAP and ECMAP with Route C processes. The deformation stress state is widely distributed in nature in modified ECAP processes than in conventional ECAP. In addition, the load requirements are also higher in modified ECAP processes with that of the...
A new orthonormal polynomial series expansion method in vibration analysis of thin beams with non-uniform thickness
, Article Applied Mathematical Modelling ; Volume 37, Issue 18-19 , 2013 , Pages 8543-8556 ; 0307904X (ISSN) ; Nikkhoo, A ; Vaseghi Amiri, J ; Mehri, B ; Sharif University of Technology
2013
Abstract
In this article, OPSEM (Orthonormal Polynomial Series Expansion Method) is developed as a new computational approach for the evaluation of thin beams of variable thickness transverse vibration. Capability of the OPSEM in assessing the free vibration frequencies and mode shapes of an Euler-Bernoulli beam with varying thickness is discussed. Multispan continuous beams with various classical boundary conditions are included. Contribution of BOPs (Basic Orthonormal Polynomials) in capturing the beam vibrations is also illustrated in numerical examples to give a quantitative measure of convergence rate. Furthermore, OPSEM is adopted for the forced vibration of a thin beam caused by a moving mass....
Inhomogeneity through warm equal channel angular pressing
, Article Journal of Materials Engineering and Performance ; Volume 22, Issue 6 , 2013 , Pages 1666-1671 ; 10599495 (ISSN) ; Kim, H. S ; Karimi Taheri, A ; Momeni, A ; Sharif University of Technology
2013
Abstract
In this study, the hardness inhomogeneity of billets during multi-passes of equal channel angular pressing (ECAP) at elevated temperatures is investigated and the effect of large strain deformation during ECAP on the hardness inhomogeneity characteristics due to dynamic aging of aluminum 6061 under a variety of temperatures and ram speed was studied by TEM and hardness measurements. The hardness results showed that the hardness distribution is more homogenous after four passes using the pressing route Bc. However, when the deformation temperature was considered, performing ECAP at 100 C may provide the most homogeneous microstructure after multi-pressing as long as the total number of...
Dynamic ageing and the mechanical response of Al-Mg-Si alloy through equal channel angular pressing
, Article Materials and Design ; Volume 31, Issue 9 , October , 2010 , Pages 4076-4082 ; 02641275 (ISSN) ; Karimi Taheri, A ; Ig Hong, S ; Seop Kim, H ; Sharif University of Technology
2010
Abstract
In this paper, dynamic ageing characteristics associated with the application of equal channel angular pressing (ECAP) to Al6061 alloy at elevated temperatures was investigated. Followed by ECAP, Vickers microhardness measurement on the cross-sectional planes and microstructural observations were undertaken using transmission electron microscopy. The combination of the ECAP process with dynamic ageing at both 100°C and 150°C resulted in a significant increase in hardness. The grain size was measured as ∼160. nm after four passes. A comparison with the published data on the same alloy processed by ECAP at room temperature and statically aged, suggests several advantages in incorporating...
Risk-based Approach to Account for Soil-Structure Interaction in Seismic Design of Building Structures
,
Ph.D. Dissertation
Sharif University of Technology
;
Ghannad, Mohammad Ali
(Supervisor)
;
Mahsuli, Mojtaba
(Supervisor)
Abstract
This paper proposes a novel probabilistic approach to account for soil-structure interaction (SSI) in the seismic design of building structures. In this approach, an SSI response modification factor, RSSI, is introduced to capture SSI effects on the seismic performance of structures. The proposed procedure quantifies RSSI such that the probability distribution of the collapse capacity of the structure designed to account for SSI concurs with that of the structure designed using the default fixed-base provisions. The proposed approach is employed for special steel moment frame buildings with surface foundation. A surrogate single degree of freedom (SDOF) system is developed in this study and...
Adiabatic shear banding in an Al-Mg-Si alloy processed by equal channel angular pressing
, Article Materials Science Forum, 2 August 2010 through 6 August 2010, Cairns, QLD ; Volume 654-656 , 2010 , Pages 1014-1017 ; 02555476 (ISSN) ; 0878492550 (ISBN) ; Taheri, A. K ; Yoo, J. H ; Joo, S. H ; Kim, H. S ; Sharif University of Technology
2010
Abstract
Equal channel angular pressing is an outstanding method for imposing large plastic deformation to metallic materials without any decreasing in cross section area of as processed samples. In this paper, the effect of working temperature, ram speed and the number of passes on the formation of adiabatic shear bands in Al6061 during equal channel angular pressing was investigated. Billets of the alloy were processed up to four passes via route BC from room temperature to 200°C with two ram speeds using a die that imparts an effective strain of ∼1.1 per pass. The results have demonstrated that the onset of the adiabatic shear banding in this alloy strongly depends on the ram speed: more...
Smart micro/nanoparticles in stimulus-responsive drug/gene delivery systems
, Article Chemical Society Reviews ; Volume 45, Issue 5 , 2016 , Pages 1457-1501 ; 03060012 (ISSN) ; Ghasemi, A ; Sahandi Zangabad, P ; Rahighi, R ; Moosavi Basri, S. M ; Mirshekari, H ; Amiri, M ; Shafaei Pishabad, Z ; Aslani, A ; Bozorgomid, M ; Ghosh, D ; Beyzavi, A ; Vaseghi, A ; Aref, A. R ; Haghani, L ; Bahrami, S ; Hamblin, M. R ; Sharif University of Technology
Royal Society of Chemistry
2016
Abstract
New achievements in the realm of nanoscience and innovative techniques of nanomedicine have moved micro/nanoparticles (MNPs) to the point of becoming actually useful for practical applications in the near future. Various differences between the extracellular and intracellular environments of cancerous and normal cells and the particular characteristics of tumors such as physicochemical properties, neovasculature, elasticity, surface electrical charge, and pH have motivated the design and fabrication of inventive "smart" MNPs for stimulus-responsive controlled drug release. These novel MNPs can be tailored to be responsive to pH variations, redox potential, enzymatic activation, thermal...
Probability of missed detection as a criterion for receiver placement in MIMO PCL
, Article IEEE National Radar Conference - Proceedings, 7 May 2012 through 11 May 2012, Atlanta, GA ; 2012 , Pages 0924-0927 ; 10975659 (ISSN) ; 9781467306584 (ISBN) ; Chitgarha, M. M ; Radmard, M ; Nayebi, M. M ; Sharif University of Technology
IEEE
2012
Abstract
Using multiple antennas at the transmit and receive sides of a passive radar brings both the benefits of MIMO radar and passive radar. However one of the obstacles arisen in such configuration is the receive antennas placement in proper positions so that the radar performance is improved. Here we just consider the case of positioning one receiver among multiple illuminators of opportunity. Indeed it is a start for the solution of optimizing the geometry of the multiple receivers in a passive radar
An efficient method for the ring opening of epoxides with aromatic amines by Sb(III) chloride under microwave irradiation
, Article Journal of Chemical Research ; Issue 4 , 2008 , Pages 220-221 ; 03082342 (ISSN) ; Hashemi, M. M ; Mottaghi, M. M ; Foroughi, M. M ; Sharif University of Technology
2008
Abstract
SbCl3 supported on montmorillonite K-10 is an efficient catalyst for the ring opening of epoxides with aromatic amines under solvent-free conditions and microwave irradiation to give the corresponding b-amino alcohols in high yields with high regioselectivity