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A combination of severe plastic deformation and ageing phenomena in Al-Mg-Si Alloys
Vaseghi, M.,Kim, H.S. Scientific and Technical Press ; Elsevier Science 2012 MATERIALS AND DESIGN Vol.36 No.-
In this paper static and dynamic strain ageing behavior in Al-Mg-Si alloys related to equal channel angular pressing (ECAP) was investigated. In order to examine the combined plastic deformation, solution treatment and ageing effects on strengthening characteristics, experimental results of ageing without ECAP, pre-ECAP ageing, post-ECAP ageing and dynamic ageing inside of ECAP die were compared. In particular, the effects of ageing temperature, ageing time, strain rate in ECAP, and sequence of heat treatment and ECAP on Vickers hardness were discussed. To achieve a higher hardness, an optimum ageing cycle combined with ECAP process is presented based on the results of current study. By employing the proposed schedule the hardness value was increased from 86 HV (as-solution treatment) to 138 HV (peak hardness of the current schedule).
Dynamic ageing and the mechanical response of Al–Mg–Si alloy through equal channel angular pressing
Vaseghi, Majid,Taheri, Ali Karimi,Hong, Sun Ig,Kim, Hyoung Seop Elsevier 2010 MATERIALS AND DESIGN Vol.31 No.9
<P><B>Abstract</B></P><P>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 ∼160nm 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 dynamic ageing with ECAP. These advantages consist of the ability to attain better grain refinement, increased hardness and the potential for saving time and energy.</P>
Evaluation of performance of eccentric braced frame with friction damper
Vaseghi Amiri, J.,Navayinia, B.,Navaei, S. Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.39 No.5
Nonlinear dynamic analysis and evaluation of eccentric braced steel frames (EBF) equipped with friction damper (FD) is studied in this research. Previous studies about assessment of seismic performance of steel braced frame with FD have been generally limited to installing this device in confluence of cross in concentrically braced frame such chevron and x-bracing. Investigation is carried out with three types of steel frames namely 5, 10 and 15 storeys, representing the short, medium and high structures respectively in series of nonlinear dynamic analysis and 10 slip force values subjected to three different earthquake records. The proper place of FD, rather than providing them at all level is also studied in 15 storey frame. Four dimensionless indices namely roof displacement, base shear, dissipated energy and relative performance index (RPI) are determined in about 100 nonlinear dynamic analyses. Then average values of maximum roof displacement, base shear, energy dissipated and storey drift under three records for both EBF and EBF equipped with friction damper are obtained. The result indicates that FD reduces the response compared to EBF and is more efficient than EBF for taller storey frames.
M. Vaseghi,S. Baghshahi,M. Mashhadi,A. Nemati 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.5
Gel-casting is an appropriate method for manufacturing porous parts with complicated forms, which has also been used in shaping Si3N4 bodies. In the present study, porous bulk Si3N4 samples were fabricated using gel-casting. To this aim Si3N4 slurries were prepared with solid loading of 35 vol%. To the slurry was added 1 and 3 wt% rod-like BN to enhance the mechanical properties. BN was selected to further reduce the dielectric constant and loss of the prepared porous Si3N4 samples. The findings suggested that employing rod-like BN increased the porosity from 38 % to 41 %, reducing the flexural strength from 77 MPa in the part without BN to 56 MPa in the part containing 3 wt% BN. On the other hand, dielectric properties reduced in the parts with BN compared with the part without BN.
M. Vaseghi,S. Baghshahi,M. Mashhadi,A. Nemati 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.2
The gel casting method was used for the production of Si3N4 porous ceramics with 25 vol% solid loading, and the effect ofadding 1 and 3 wt.% of BN whisker-like (synthesized in the laboratory) on the flexural strength of the composites wasinvestigated. The gel-cast samples were prepared using an AM-MBAM monomer system and deionized water solvent. The gelcast bodies were dried at ambient temperature and humidity for 48hrs. The burnout process was carried out at 600 oC for14hrs in the air. The samples were then subjected to heat treatment at 1650 oC for 2 hrs in a bed of 50% Si3N4-50% BN. Resultsshowed that BN whisker-like were agglomerated in deionized water. To solve this problem and to properly disperse thewhisker-like in the slurry, active surface agent groups were employed. Adding BN whisker-like to ceramic bodies, increasedthe porosity from 33% in samples without BN to 46% in samples containing 3 wt% BN whisker-like, resulting in a decreasein the density from 1.8 g/cm3 to about1.61 g/cm3. Since the Si3N4 ceramics require aids for the sintering, SiO2 and Y2O3additives were used with a ratio of 1 to 2, respectively, which led to the formation of Si2N2O phase. Si2N2O is similar to theSi3N4 phase in terms of the thermal expansion coefficient and chemical properties. Because of its rod shaped morphology, ithas a similar function to β-Si3N4 phase in improving the mechanical properties of the ceramic. Although porosity in theceramics containing 3 wt.% BN whisker-like was higher than those containing 1 wt.%, the porosity created vacant spaces forfurther growth of Si2N2O-rod shaped grains and in spite of higher porosity, better flexural strength was achieved for bodieswith 3 wt.% BN whisker-like. Also, in bodies without BN whisker-like, the flexural strength was 88 MPa, due to the lowporosity and the presence of stretched Si2N2O grains.
Super pregnancy in a BALB/c mouse superovulated with PMSG
Hanieh Vaseghi,Asghar Mogheiseh,Masood Sepehrimanesh,Mojtaba Kafi,Mohammad Hossein Nooranizadeh 한국실험동물학회 2017 Laboratory Animal Research Vol.33 No.3
This paper reports a case of super pregnancy in a BALB/c mouse pregnant with 30 pups following induction of superovulation using a PMSG-hCG protocol. Superovulation was induced in 10 mice by injecting 5 IU PMSG followed by 5 IU hCG 48 hours later. Immediately after injection of hCG, animals were placed with males at a ratio of 1 to 1 for 24 hours. On day 14 after mating, animals were killed by cervical dislocation and the uterus was examined for pregnancy and the number of fetuses. The mean (±SEM) number of fetuses observed in ten mice was 5.4±3.18 with an unexpectedly super pregnant mouse bearing 30 fetuses on day 14 of pregnancy.
Evaluation of performance of eccentric braced frame with friction damper
J. Vaseghi Amiri,B. Navayinia,S. Navaei 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.39 No.5
Nonlinear dynamic analysis and evaluation of eccentric braced steel frames (EBF) equipped with friction damper (FD) is studied in this research. Previous studies about assessment of seismic performance of steel braced frame with FD have been generally limited to installing this device in confluence of cross in concentrically braced frame such chevron and x-bracing. Investigation is carried out with three types of steel frames namely 5, 10 and 15 storeys, representing the short, medium and high structures respectively in series of nonlinear dynamic analysis and 10 slip force values subjected to three different earthquake records. The proper place of FD, rather than providing them at all level is also studied in 15 storey frame. Four dimensionless indices namely roof displacement, base shear, dissipated energy and relative performance index (RPI) are determined in about 100 nonlinear dynamic analyses. Then average values of maximum roof displacement, base shear, energy dissipated and storey drift under three records for both EBF and EBF equipped with friction damper are obtained. The result indicates that FD reduces the response compared to EBF and is more efficient than EBF for taller storey frames.
Zahra Vaseghi,Omid Tavakoli,ALI NEMATOLLAHZADEH 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.3
Novel nanoclusters (NCs) of Cu/Cr/Ni/O were produced by a green synthesis approach using leaf extracts of E. campestre and F. subpinnata at room temperature and pH 7. Characterization of the produced NCs using EDS, XRD, and FESEM revealed that E. campestre results in CuO-Cr2O3-NiO nanocomposites with average crystallite size of 29.2 nm, while binary and ternary Cu-Cr-Ni-O nanoalloys of averaged 9.8 nm crystallite size are produced using F. subpinnata leaf extract. In addition, bioreduction mechanism of the metal ions was investigated for both plant extracts by evaluating total phenolics/total flavonoids, HPLC chromatograms of the leaf extracts, and FTIR spectra of the extracts before and after the bioreduction reaction. It was found that phenolic acids are the main responsibility for the bioreduction of the metal ions. In particular, chlorogenic acid, rosmarinic acid, and syringic acids for the nanoalloys produced by reducing potential of F. subpinnata, and rosmarinic acid for the nanocomposites synthesized using E. campestre were identified as the main reducing agents. FTIR studies revealed that in CuO-Cr2O3-NiO nanocomposites, aliphatic and aldehyde amine groups and in Cu-Cr-Ni-O nanoalloys, aliphatic and aldehyde amine, and nitrile groups act as both capping and stabilizing ligands