Showing papers in "World Journal of Engineering in 2012"

Ball milling of jute fibre wastes to prepare nanocellulose

Abstract: The objective of this work was to use the spinning waste in form of short fibres for the preparation of nano size fillers in nanocomposite applications. The present paper concerns with the jute fibres as the source to produce nanocellulose by high energy planetary ball milling process and its potential applications as fillers in biodegradable nanocomposite plastics used in automotives, packaging and agriculture applications. Influence of various milling conditions like nature of milling (i.e. dry or wet), milling time and ball size are studied on the particle size distribution and morphology of jute nanoparticles obtained. Wet milling in the deionised water resulted into particle size refinement below 500 nm with narrow size distribution after 3 hours of milling at the cost of small amount of contaminations introduced from milling media.

Experimental study of nano-modified lime-based grouts

Abstract: Grouts are fluid mixtures of binders with water, for the filling and strengthening of masonry or the consolidation and preservation of mortar stratification. In this paper, totally 15 compositions of lime-based grout mixtures containing admixtures and silica nano-particles were designed, manufactured and experimentally tested in order to evaluate their properties in fresh (fluidity, permeability, volume stability) and hardened state (shrinkage deformations, mechanical strength). Conclusive remarks were attained regarding the influence of silica nano-particles in grouts performance.

Physical properties and storage stability of asphalt binder modified with nanoclay and warm asphalt additives

Abstract: Nowadays, researchers are interested in using the material at nanoscales as one of asphalt binder modifier. In this paper, Malaysian asphalt binder was modified with nanoclay and warm asphalt additives (WAA) and tested to determine the physical properties and storage stability. The results of the investigation indicated that the modified asphalt binders were stable in term of storage and they also have potential to improve physical properties of asphalts such as increasing softening point and decreasing the penetration. In addition, there was a significant reduction of temperature for mixing and compaction of asphalt mixtures.

Defect characterization in commercial carbon-carbon composites

Abstract: A relatively inexpensive and easy to operate custom built infrared thermography (IRT) system was developed and utilized for the detection and characterization of defects in Carbon-Carbon (C/C) composite aircraft brake disks. This method uses an active infrared thermography (IRT) approach, i.e. Flash Heating method, for a non-destructive evaluation (NDE) of C/C brake disk materials. The experimental results obtained from the developed system were then compared with commercial IRT turn-key system. In addition, Finite Element Analysis (FEA) was also carried out to determine the detectible defect depth and diameter of the defects in C/C composites to validate the experimental results. The experimental results were compared to the FEA results and it was found that they were in good agreement with one another.

Mechanical and physical properties of particleboard made from two pulp and paper mill secondary sludges

Abstract: To investigate environmentally friendly alternatives for sludge disposal, three proportions of secondary sludge (SS) from two pulping processes (Kraft and TMP) were incorporated in the formulation of particleboard manufacturing. A 32 factorial design was used where the factors were Urea-formaldehyde (UF) content (5%, 7%, and 9% dry weight of resin per dry weight of particles) and secondary sludge percentage (75%, 100%, and 125% dry weight of SS per dry weight of resin). For each pulping process, 27 panels with SS and 3 control panels (without SS for each resin content) were made for a total of 63 panels. All panels were tested for thickness swell, linear expansion, internal bond strength (IB), flexural modulus of elasticity (MOE) and flexural modulus of rupture (MOR). Results indicated that particleboards made with SS from both pulping processes met the ANSI standards for linear expansion, IB, MOE and MOR. However, none of the tested panels met the standard for thickness swell and adding SS to the formula...

Effect of internal hydrophobation, silica fume and w/c on compressive strength of hardened cement pastes

Abstract: Internal hydrophobation by adding hydrophobic agents during the mixing process is a method for reducing water permeability of cement based materials. It can be used as an alternative to other methods such as reducing water cement ratio (w/c) or using silica fume (SF). However, it may affect other properties of cement based materials such as compressive strength. In this paper the results of an experimental study on compressive strength of different hcps with main variables w/c, SF and hydrophobic agents are presented. Rapeseed oil and alkyl alkoxysilane were selected as hydrophobic agents. Although, a low dosage of hydrophobic agents can be more effective than lowering w/c or adding SF in reducing water permeability, an obvious reduction was observed in compressive strength by this way of internal hydrophobation compared to the other above mentioned methods. Different reasons such as lower hydration degree, chemical reactions of hydrophobic agents and non-uniform distribution of hydrophobic materials in t...

Laser cladding of Cu0.5NiAlCoCrFeSi high entropy alloy on AZ91D magnesium substrates for improving wear and corrosion resistance

Abstract: To improve the wear and corrosion properties of AZ91D magnesium alloy, a Cu0.5NiAlCoCrFeSi high entropy alloy (HEA) was fabricated on AZ91D magnesium substrate specimens by laser cladding using elemental powders. The laser-clad coating consists of a fine dendritic structure of a simple BBC phase with nano-size precipitates. The hardness of the coating was some ten times higher than that of the AZ91D substrate and was even higher than that of the same HEA produced by arc melting. The laser-clad coating exhibited good wear resistance, with a wear rate five times lower than that of the substrate material in dry friction wear conditions. The main wear mechanisms of the substrate and the HEA coating were different, the former dominated by both abrasive wear and adhesive wear and the latter by oxidative abrasive wear. With regard to corrosion properties, the laser-clad coating exhibited a more positive corrosion potential and a lower corrosion current density than those of the uncoated substrate material.

Advance of mining technology for coals under buildings in China

Abstract: In China there are large amounts of coal located underneath buildings. In this article the severity of the problem is studied, and the characteristics of the mining technology used for the extraction of coals under buildings are described. Based on the comprehensive analyses of the abundant literature, separated bed grouting, backfill mining, Partial Mining and homonic mining technology, are the main mining technologies that exist for extraction of these coals. At the same time, the necessary measures for protecting the buildings are also considered. In particular, the authors have analysed the development of these mining technologies and concluded that the waste filling will be the focus of development, and that the main developing technologies of the filling mining method should be further perfecting the separated bed filling, strip mining and strenthening the anti-deformation of building.

Application of cohesive-zone models to delamination behaviour of composite material

Abstract: The parameters of cohesive elements have to be chosen correctly in the simulation of composite delamination by finite element method: such as interface strength, interface stiffness and shape of cohesive law. The purpose of this work is to investigate their influence on the accuracy of the results obtained. A three-dimensional cohesive-zone model has been established using Ls-dyna to simulate Double-Cantilever-Beam mode I (DCB) and Edge-Notched-Flexure mode II (ENF) tests. The influence of these parameters of cohesive element on the maximum load and the slope of load-displacement curve have been discussed by comparing experimental and numerical results. Four traction-separation laws: bilinear, linear-parabolic, exponential and trapezoidal were considered associated with a large variation of the interface strength and of the initial interface stiffness.

Thermal and efficiency analysis of a single phase induction motor with Peltier devices

Abstract: We present the results obtained from the thermal and efficiency analysis of a single phase induction motor with Peltier devices. A single phase induction motor is completely simulated in SolidWorks® and Matlab® Simulink®. The cooling of the induction motor is done by means of Peltier devices and the corresponding power consumption and stator temperature is recorded. From the SolidWorks® simulation results it can be seen that the temperature of the induction motor under normal operating conditions is cooled from 68°C to 35°C. From the Matlab® Simulink® simulation results show that the efficiency of the induction motor is increased by an average of 3.73% from the normal operating condition to the cooled operating condition with the inclusion of the Peltier devices onto the system.

Monte Carlo simulation of defects in hard-sphere crystal grown on a square pattern

Abstract: Monte Carlo simulations of hard-sphere (HS) crystal grown on a square patterned wall under gravity have been performed. While previous simulations were performed with step-wise controlled gravity, in the present simulations constant gravity has been applied from the first. In the case in which a flat wall is used as the bottom wall, if a large gravity is suddenly applied, the system does polycrystallize. On the other hand, in the present simulations, despite the sudden application of gravity, the system has not polycrystallize. Crystalline nucleation on the square pattern and successive crystal growth upward are suggested to overcome the homogeneous nucleation inside and result in. Defect disappearance, which has been essentially the same as that for the case with step-wise controlled gravity, has also observed for the present case. The characteristic of the square patterned bottom wall simulation with a large horizontal system size has been existence of triangular defects suggesting stacking tetrahedra.

Effect of web formation on properties of hydroentangled nonwoven fabrics

Abstract: The aim of this study was to determine the effects of two popular web-forming technologies, viz., the Rando air-laid technology and the traditional carding and cross-laying technology, on properties of the hydroentangled nonwoven fabrics made therewith. A mill-like fiber processing study was conducted in a commercial-grade pilot plant using a variety of short staple fibers and their blends. The fibers used in the study were greige cotton, bleached cotton, cotton derivatives, and cut-staple polyester. The hydroentangled fabrics produced with the two systems were mainly evaluated for their physical and mechanical properties, absorbency, absorbency capacity, and whiteness. The study has shown that, with the exception of greige cotton linters, the greige cotton lint, greige cotton gin motes, and even greige cotton comber noils, either alone or in blend with the other fibers mentioned, can be mechanically processed into hydroentangled nonwoven fabric structures without any insurmountable difficulties. The drop...

Morphological, electrical and optical properties of γ- copper (I) iodide thin films by mist atomization technique

Abstract: This research focuses on the effect of molar concentration of CuI thin film deposited by mist atomization technique. The result shows the CuI thin film properties strongly depends on its precursor concentration. Thickness between 0.35 x 104 nm - 1.60 x 104 nm was obtained as the concentration increases. The increment of thickness affects the electrical properties which is the resistivity and conductivity of CuI thin film. The resistivity of about 101ω cm to 103ω cm was observed in those CuI thin films. For optical properties, the absorption coefficient and optical band gap of CuI was determined by using Tauc's plot. The high absorption coefficient of 106 m-1 is observed in those CuI thin films with bandgap between 2.84 to and 2.95eV obtained in this experiment.

Compressibility characteristics of tropical peat using Rowe cell consolidation

Abstract: This paper presents the results of the physical and compressibility characteristics of tropical peat, from Matang, Malaysia. Different physical properties tests have been conducted on peat samples. Rowe cell consolidation and standard 1-D consolidation tests were performed on undisturbed peat samples to evaluate the compressibility characteristics. A specially designed and fabricated peat sampler has been used to collect the undisturbed peat sample for Rowe cell consolidation test. The laboratory test results revealed that peat has a large void ratio with high water content and undergone large consolidation settlements when applied load. The results of Rowe cell test can be used to simulate close to the the field geotechnical characteristics of peat for any design or numerical modelling where reliable data is most important.

Performance of eccentrically loaded GFRP reinforced concrete columns

Abstract: This paper explores the behavior of GFRP and steel reinforced concrete columns when subjected to eccentrically axial loads. Six columns of 150*150 mm cross section were tested. Four of them had GFRP reinforcement and two had steel reinforcement. The concrete strength of the GFRP reinforced columns was either 24.73 Mpa or 38.35 Mpa while for the steel reinforced columns it was 24.73 Mpa. The eccentricity was either 50 mm or 25 mm and the tie spacing was either 80 mm or 130 mm. Large longitudinal deformations were recorded for columns with GFRP reinforcement and for columns with large tie spacings. However, tie spacing had no notable effect on the maximum lateral deflection and ductility of GFRP columns of this research. The average maximum stress was about 60% of the concrete compressive strength for columns with initial eccentricity of 50 mm. GFRP bars recorded higher strains than steel bars and these strains were larger when the tie spacing was large. The increase in the strength of the concrete was asso...

Versatile low-pressure plasma-enhanced process for synthesis of iron and iron-based magnetic nanopowders

Abstract: Using microwave low-pressure discharge, we synthesised magnetic iron-oxide nanopowder from the iron pentacarbonyl precursor. We were able to vary the size and chemical composition (especially the ratio between various iron oxides) by careful control of the process parameters. The nanoparticulate product was analysed by X-ray diffraction (XRD) and Raman spectroscopy. However, the XRD cannot reliably distinguish between the size-broadened peaks of γ-Fe2O3 (maghemite) and Fe3O4 (magnetite) due to their nearly identical crystalline structure. Hence we used a chemical method to determine the presence of Fe(II) and Fe(III) ions in the nanopowder samples. The results agree with those from the Raman spectroscopy.

Poly(vinyl butyral)-zirconia hybrid films formed by sol-gel process

Abstract: A sol-gel process has been successfully utilized to form hybrid materials of poly(vinyl butyral) (PVB) and zirconium dioxide (zirconia). The gelation occurred due to the interaction between remaining hydroxyl group of PVB and zirconia. The hybrids showed good optical transparency and significant improvement in Young's modulus, dynamic mechanical property, abrasion resistance and impact resistance. The glass transition temperature of PVB shifted to higher temperatures by hybridization of PVB and zirconia.

Magnetism and electronic transport in (Ni, Cu)2 MnSn Heusler alloys under ambient and elevated pressures

Abstract: The electronic properties, exchange interactions, Curie temperatures and transport properties of random quaternary Heusler alloys (Ni, Cu)2MnSn are studied by means of density-functional calculations over the entire range of dopant concentration. Results agree qualitatively as well as quantitatively with the available experimental data. The residual resistivity is found to obey the Nordheim rule, indicating weak-scattering regime. The temperature-dependent spin-disorder resistivity is found to be described well via the disordered model of local moments. Effect of pressure on the Curie temperature and the resistivity is also explored.

Magnetism and half-metallicity of some Cr-based alloys and their potential for application in spintronic devices

Abstract: We present results of the exchange interactions and Curie temperatures in some Cr-based chalcogenides and pnictides. The calculations are performed mostly for Zinc Blende (ZB) structure with the lattice parameter varying between 5.45 and 6.6 A, appropriate for some typical II-VI and III-V semiconducting substrates. Electronic structure is calculated via the linear muffintin-orbitals method and disorder effects, when appropriate, are taken into account via the coherent potential approximation. Calculated exchange interactions are used to estimate the Curie temperature by employing the mean-field and the random phase approximations. For CrTe we compare the results of the ZB and Rock-Salt (RS) structures.

Compacted nanosilica-talc /calcium carbonate polyacrylate composites prepared using accelerated sedimentation

Abstract: The effectiveness of centrifugation as the compacting method in preparing high filler composites has been investigated. Different size and shape of fillers were used to ensure efficient filler space filling. In situ polymerization of bisphenol-A ethoxy diacrylate after centrifugating produced biomimetic composites with 74-86 % filler content. The filler space was efficiently filled by using a combination of nano and microsize fillers, especially in the nanosilica-CaCO3 composite. The morphology of the composites indicates that the fillers were well dispersed and embedded in the polymer matrix. The etched surface of the nanosilica-talc composite reveals that the combination of talc and nanosilica formed a biomimetic composite that displayed an ordered brick-and-mortar nacre-like structure. The wide-angle X-ray diffraction patterns indicate the crystal structure of CaCO3 and talc were maintained in the composite.

Multiwalled carbon nanotubes-magnetite reinforced thermoplastic polypropylene- natural rubber blends

Abstract: The effect of multiwalled carbon nanotubes (MWCNTs)-magnetite (Fe3O4) hybrid content on the magnetic and dynamic mechanical properties of thermoplastic polypropylene-natural rubber (TPNR) nanocomposites was evaluated. The effect of acid treatment of MWCNTs on the properties of nanocomposites has also been examined. TPNR/fillers nanocomposites were prepared via a Thermo Haake internal mixer using melt blending method with ball-milling technique as a pre-mixed process. The acid treatment successfully shortened the lengths and disentangled the crowds of MWCNTs. The improved dispersion of acid-treated MWCNTs-Fe3O4 in TPNR matrix and the enhanced interfacial adhesion between acid-treated MWCNTs-Fe3O4 and TPNR matrix increased the magnetic and dynamic mechanical properties. Acid-treated MWCNTs-Fe3O4 filled TPNR shows 10% improvement in storage modulus over neat TPNR due to the fine dispersion of MWCNTs in the TPNR matrix.

Improved Genetic Algorithm and its application in optimization of frame structures

Abstract: To overcome the problems of premature convergence and lower local search ability of the Genetic Algorithm (GA), an improved GA based on the Fish Algorithm was proposed. The new algorithm can speed up the optimal and the cluster behavior of the GA with the ability to overcome the local maximum. Then the improved algorithm was applied to the optimization of the reinforced concrete frame structure. The optimization model was established with the objective of minimizing the cost of beams and columns. The total cost of the structure obtained from the algorithm was compared with that obtained using the fuzzy algorithm and found to be lower. Thus the improved GA is proven to be practical and efficient when used for the optimization of frame structures.

Physical mechanical properties and microstructure analyses on effect of incorporating cigarette butts in fired clay bricks

Abstract: Several trillion cigarettes produced worldwide annually lead to many thousands of kilograms of toxic waste. Cigarette butts (CBs) accumulate in the environment due to the poor biodegradability of the cellulose acetate filters. This paper presents some of the results from a continuing study on recycling CBs into fired clay bricks. The results show that the density of fired bricks was reduced by up to 30%, depending on the percentage of CBs incorporated into the raw materials. Similarly, the compressive strength of bricks tested decreased according to the percentage of CBs included in the mix. Nevertheless, by increasing mixing times, better quality bricks can be produced, even with the inclusion of high percentages of CBs. Longer mixing times increased dry density and compressive strength, equivalent to about 53% and 11% respectively. Microstructure observation using ESEM confirm the result by showing the apparent size of pores is reduced drastically and the distribution of pores becomes more uniform as the mixing time increases from 5 to 15 minutes, hence decreasing the porosity in the clay body which subsequently leads to a denser product with higher strength.

Numerical modelling of castellated beams with hexagonal openings

Abstract: In this paper, a numerical model is developed to predict the behaviour of castellated beams with hexagonal. The numerical model takes into account both material and geometric non-linearity. To initiate buckling, an initial small out-of-plane geometric imperfection, obtained from an eigenvalues buckling analysis, was imposed to the model. Calibration with experimental data obtained from previous work shows that the model is able to predict, with relatively good accuracy, the ultimate load. A parametric study is then followed to determine the effect of web thickness, yielding stress and opening height on the ultimate load of the beams. Based on the parametric studies results, the accuracy of the cross-section classification for castellated beams proposed in the Annex N of Eurocode 3 is assessed.

Sign changes of seebeck coefficients due to extrinsic-to-intrinsic transition for PbTe nanocrystals

Abstract: Three types of PbTe samples, e.g. nanoparticles, nanowires and bulk ingots, have been prepared. The investigation of the Seebeck coefficient of PbTe nanoparticles and nanowires clearly shows the sign change in the temperature range of 575~650 K, which is not observed for bulk ingots. Unfortunately, this temperature range is within the proposed operation temperature range for thermoelectric devices using PbTe and hence, such a change will affect their proper performance. The observed sign change of Seebeck coefficient is not simply caused by the composition variation at high temperature. It is mainly attributed to the extrinsic-to-intrinsic-semiconductor transition for PbTe nanocrystals due to the competing factors between quantum size effect increasing band gap and self-purification process decreasing their charge carrier concentration, which shift the transition point of nanocrystals to lower range as compare to that of bulk samples. Thus, such phenomenon should be considered carefully in the design of thermoelectric devices using semiconductor nanocrystals, which have attracted much attention recently.

Estimate of CLD increase laminated plate and shell low-velocity impact strength

Abstract: FRP laminated structures enjoy the advantages of a low mass and high specific strength. However, the utilization of laminated forming methods causes these structures to become susceptible to phenomena such as delamination and fiber breakage, which lead to strength deficiencies, when they sustain low-velocity impact. In light of this, increasing the low-velocity impact strength of FRP laminated structures has been a major direction. This study utilizes Constrained Layered Damping (CLD) to enhance the low-velocity impact strength of FRP laminated structures, and assesses the efficiency of attaching CLD to laminated materials in increasing low-velocity impact strength. The results provide a reference for the design and construction of relevant structures in the future. Low-velocity impact failure in FRP laminated structures commonly includes fiber breakage and delamination. Delamination is particularly apparent when laminated curved shells bear external loading. We will attach CLD to the rear of FRP laminate...

Shape memory effect and thermomechanical properties of shape memory polymer fabric composite in tension mode

Abstract: Fibers and fabrics are often used to reinforce shape memory polymers (SMPs) to improve their mechanical strength and properties, and the composites have been widely used in engineering. However incorporation of fibers and fabrics in SMPs are often accompanied with the degradation of thermal mechanical properties and shape memory effect. The thermomechanical properties and degradation mechanisms of a shape-memory polymer composite (SMPC) were investigated. Up to 100% extension, the SMPCs showed good shape memory effect with excellent recovery ratio, recovery stress and mechanical properties; while beyond that the recovery ratio and stress of the composites deteriorate rapidly due to the significant delamination and debonding of fibers and fabrics from the SMP resin and accumulation of broken fibers.

Non-Markovian evolution approach to structural modeling of material fracture

Abstract: The new multiscale non-Markov evolution modeling approach for damage accumulation and fracture processes of polycrystalline and ultra fine grained materials is proven by experimental results at nanoscale. Microstructural parameters are estimated by an atomic-force scanning probe in situ during the deformation. The non-Marcov evolution in the approach means taking into account the history of each element on a certain structure. The ultimate state of the current level controls the transfer on the next level of the whole structure. The main difficulty of traditional multiscale modeling is the determination of the ultimate states due to the parameters. This new approach presumes it is possible to restrict the current state of a material to only one control factor of nanostructure order. The new approach of defect behavior modeling allows the simulation of materials under a wide range of external influence, including low and high temperature and other environmental factors, almost without any faults.

Influence of concrete shrinkage and creep on structural characteristics of precast and prestressed concrete shells

Abstract: The actual concern for structural engineers is the failure of the structural material to meet the design safety and the safe service life of large span and wide floor space buildings. The main idea in this present report reflects the combination of the economical use of construction materials with the long and durable safe service life to cover large floor spaces, using precast and prestreseed concrete shell structural members. This paper describes the present ongoing numerical and experimental analysis model used to determine the structural long duration flexural and nonlinear deformation characteristics of reinforced precast elliptical paraboloid concrete shell elements, prestressed in both directions. Horizontal precast and prestressed edge beams supported on prestressed columns are provided to support the longitudinal edges of the shells. This present study has been based on nonlinear differential equations of the concrete matrix creep theory which reflects the correlation between the matrix stress an...

Study of nanostructured polymeric composites used for organic light emitting diodes and organic solar cells

Abstract: Polymeric nanocomposite films from PEDOT and MEH-PPV embedded with surface modified TiO2 nanoparticles were prepared, respectively for the hole transport layer (HTL) and emission layer (EL) in Organic Light Emitting Diodes (OLED). The composite of MEH-PPV + nc-TiO2 was used for Organic Solar Cells (OCS). The results from the characterization of the properties of the nanocomposites and devices showed that electrical (I-V characteristics) and spectroscopic (photoluminescent) properties of the conjugate polymers were enhanced due to the incorporation of nc-TiO2 in the polymers. The OLEDs made from the nanocomposite films would exhibit a larger photonic efficiency and a longer lasting life. For the OSC made from MEH-PPV + nc-TiO2 composite, the fill factor (FF) reached a value as high as 0.34. Under illumination of light with a power density of 50 mW/cm2, the photoelectrical conversion efficiency (PEC) was found to be of 0.15% corresponding to an open circuit voltage VOC = 1.15 V and a short-cut circuit curre...