Alejandro Zuleta; Andrés Valencia-Escobar; Carlos Rodríguez
Abstract
The high requirements of Bicycle Motocross (BMX) race conditions demands on the bicycle frame complex dynamic and static loads states by which it is expected that frames to experience high levels of stress and strain. To build efficient bike frames in terms of performance, weight and quality, it is necessary ...
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The high requirements of Bicycle Motocross (BMX) race conditions demands on the bicycle frame complex dynamic and static loads states by which it is expected that frames to experience high levels of stress and strain. To build efficient bike frames in terms of performance, weight and quality, it is necessary to analyse systematically its response against different loads. The aim of this work is to perform the design of a BMX frame for the national team of Colombia, including the microstructural and mechanical characterization of the initial bicycle frame as complement for the macrostructural characterization of the frame in static conditions. The components of the bike frame were exanimated using optical emission spectrometry, metallographic examinations, microhardness measurements and mechanical tests. It was found that significant differences of the grain sizes of the samples were reflected in the deformation values measured in the frame showing a high structural anisotropy. Despite this, the microhardness and mechanical resistance values the results show coherence between them. In Addition, safety coefficient of the four of the components of the bicycle frame was calculated finding that coefficient values was the calculated safe factor was 4.27. Copyright © 2018 VBRI Press
Mrinmoy Garai; Basudeb Karmakar
Abstract
This study exemplifies the effects of 5 wt.% Pb2+ addition replacing the same Zn2+ content on crystallization and microstructure of 10B2O3-16Al2O3-39SiO2-12MgO-12MgF2-4K2O-1Li2O-1AlPO4 (wt.%) glass-ceramic composite. Increase of linear thermal-expansion (6.93 to 7.18×10-6/K at 50-600°C) in ...
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This study exemplifies the effects of 5 wt.% Pb2+ addition replacing the same Zn2+ content on crystallization and microstructure of 10B2O3-16Al2O3-39SiO2-12MgO-12MgF2-4K2O-1Li2O-1AlPO4 (wt.%) glass-ceramic composite. Increase of linear thermal-expansion (6.93 to 7.18×10-6/K at 50-600°C) in substituting Zn2+ by Pb2+ is attributed to the field-strength of cations. Opaque crystalline glass-ceramics are derived from the transparent glasses (synthesized by single-step melt-quenching at 1500OC) by controlled heat-treatment at 1050°C and the predominant crystalline-phase was identified as fluorophlogopite mica, KMg3AlSi3O10F2. FFESEM of the ZnO containing glass-ceramics revealed that 100-200 µm sized plate-like crystals are in ‘well-packed interlocked arrangement’; which changed to ‘nanocrystalline microstructure’ combined of ‘spherical droplet like’ nanocrystals (crystal size = 10-50 nm) in attendance of PbO. Decrease in linear thermal-expansion (11.03 to 7.93 × 10-6/K at 50-700°C) due to the substitution of ZnO is ascribed to the crystallization inhibiting tendency of PbO towards boroaluminosilicate system. Thermal-expansion of ZnO containing glass-ceramic is large (> 11 × 10-6/K at 50-700 and 50-800°C) which can exhibit their enough thermal shock resistivity to be suitable for high-temperature sealing application. Copyright © 2017 VBRI Press.
Giuseppe Napoli; Sabrina Mengaroni; Marco Rallini; Luigi Torre; Andrea Di Schino
Abstract
The present study is focused on analyzing the effect of the interrupted quenching followed by a partitioning process in a high carbon steel 0.50C-1.50Mn-0.40Si-2.00 Cr without significant contribution of Al. Thermal treatments were performed at laboratory scale in a quenching dilatometer Linseis R.I.T.A ...
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The present study is focused on analyzing the effect of the interrupted quenching followed by a partitioning process in a high carbon steel 0.50C-1.50Mn-0.40Si-2.00 Cr without significant contribution of Al. Thermal treatments were performed at laboratory scale in a quenching dilatometer Linseis R.I.T.A RL78. The fractions of retained austenite were evaluated by scanning electron microscope. The temperature for the interrupted quenching phase was evaluated based on the Koistenen and Marburger equation (adapted to the 0.50C steel) and the result highlights a correlation between the chosen different temperature of quenching and the fraction of retained austenite formed during the quenching step of the process. Copyright © 2017 VBRI Press.
Andrea Di Schino
Abstract
The effect of low-alloy additions on hardenability of high strength low-C steels is reported. Various as-quenched materials with microstructures consisting of low-C (granular) bainitic, mixed bainitic/martensitic and fully martensitic microstructures were produced. Results show that for a given cooling ...
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The effect of low-alloy additions on hardenability of high strength low-C steels is reported. Various as-quenched materials with microstructures consisting of low-C (granular) bainitic, mixed bainitic/martensitic and fully martensitic microstructures were produced. Results show that for a given cooling rate, an increase of austenite grain size (AGS) and of Mo and Cr contents decreases the transformation temperatures and promotes martensite formation. Copyright © 2017 VBRI Press.
S. M. Sathiya; G. S. Okram; M. A. Jothi Rajan
Abstract
Microwave assisted co-precipitation method is used to synthesize copper oxide nanoparticles from various concentrations of CuCl2.2H2O (0.1 M - 0.5 M) precursors. Both CuO and Cu2O phases are observed from X-ray diffraction (XRD) pattern and further confirmed from Energy Dispersive X-ray Analysis (EDX) ...
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Microwave assisted co-precipitation method is used to synthesize copper oxide nanoparticles from various concentrations of CuCl2.2H2O (0.1 M - 0.5 M) precursors. Both CuO and Cu2O phases are observed from X-ray diffraction (XRD) pattern and further confirmed from Energy Dispersive X-ray Analysis (EDX) and selected area electron diffraction (SAED) data. The particle size of 43 to 27 nm determined from XRD data using Scherrer formula is in good relation with Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) images. The existence of reasonably uniform size and shape is clear from SEM. The band gaps determined from the UV-Visible absorption peaks and vibrational modes observed from Micro-Raman Scattering (MRS) analysis further confirm the presence of CuO and Cu2O phases. These results are also related to electrical conductivity at low temperatures which illustrate different types of conduction mechanisms. The samples show semiconducting behavior with improved electrical conductivity. Finally, the material is proposed to have applications in designing gas sensors and also in regulating electrical conductivity in drug delivery systems. Copyright © 2017 VBRI Press.
Lincy Varghese; VVL. Kanta Rao; Lakshmy Parameswaran
Abstract
The microstructure and time dependent properties of nanosilica (nS) added high performance concrete (nS-HPC) were investigated, and a comparison of these properties with those of microsilica (mS) added high performance (mS-HPC) concrete and a reference concrete (RefCon) are presented. 3% colloidal nS ...
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The microstructure and time dependent properties of nanosilica (nS) added high performance concrete (nS-HPC) were investigated, and a comparison of these properties with those of microsilica (mS) added high performance (mS-HPC) concrete and a reference concrete (RefCon) are presented. 3% colloidal nS and 7.5% powder mS were used to make nS-HPC and mS-HPC, respectively. The scanning electron microscopic image of the 90 days’ nS-HPC revealed that the quantity of Ca(OH)2 present was almost negligible and the concrete attained a finer and compact microstructure with finer C-S-H as compared to that of other two concretes. The creep and drying shrinkage of the nS-HPC were found to be higher than those of RefCon and mS-HPC. However, the observed drying shrinkage of all the concrete mixes was found to be conforming with the estimates made from Indian Road Congress (IRC):112-2011 model, while on the other hand, the creep coefficients of mS-HPC and nS-HPC was found to be higher than the corresponding estimated creep coefficients, and the same were found to be higher by 13.3% and 18.2%, respectively, at 100 days. The increase in drying shrinkage and creep of both the high-performance concretes (HPC) than that of RefCon may be attributed to higher amounts of gel water present in the finer C-S-H produced due to pozzolanic action. The results from the study indicates suitability of nS-HPC for construction of bridge structures. Copyright © 2017 VBRI Press.
P. Rosaiah; G. Lakshmi Sandhya; S. Suresh; Jinghui Zhu; Yejun Qiu; O. M. Hussain
Abstract
Vanadium pentoxide (V2O5) thin films have been prepared onto ITO coated flexible Kapton substrates by electron beam evaporation technique. The influence of substrate temperature on the structural, morphological, optical and electrical properties has been investigated. The XRD results reveals that the ...
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Vanadium pentoxide (V2O5) thin films have been prepared onto ITO coated flexible Kapton substrates by electron beam evaporation technique. The influence of substrate temperature on the structural, morphological, optical and electrical properties has been investigated. The XRD results reveals that the films prepared at lower temperatures are amorphous in nature and the films prepared at 300 oC is exhibited predominant (001) orientation with an orthorhombic crystal structure. AFM study showed that the grain size varies from 80 nm to 150 nm. The optical studies revealed that the transmittance decreased with increasing substrate temperature. The optical absorption coefficient ‘a’ determined from the experimentally measured transmittance and reflectance data for V2O5 films was found to give a better fit for the exponent n = 3/2 suggesting the direct forbidden transitions with an estimated optical band gap of 2.31 eV for the films prepared at 300 oC. The electrical conductivity has been observed to be increased from 2 x 10-6 S/cm to 3 x 10-2 S/cm by varying temperature from 30 oC to 300 oC. The electrochemical experiments exhibited the discharge capacity of about 60 μAh/(cm2-μm) for the films deposited at 300 oC.
