Advances in Materials Science and Engineering The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Effect of Short-Term Aging Process on the Moisture Susceptibility of Asphalt Mixtures and Binders Containing Sasobit Warm Mix Additive Sun, 29 Nov 2015 13:51:05 +0000 Moisture susceptibility is one of the key issues of warm mix asphalt (WMA). In this research, the moisture susceptibility of asphalt mixtures and binders containing Sasobit warm mix additive was investigated in comparison to that of hot mixture asphalt (HMA) through laboratory aging experiments. The WMA asphalt mixtures were aged in the laboratory at three aging temperatures and times. The moisture susceptibility of the asphalt mixtures was measured through the laboratory immersed Marshall test and freeze-thaw splitting test. The surface free energy (SFE) of asphalt binders extracted from WMA asphalt mixtures was determined by the sessile drop method. The results show that the aging time and temperature have a significant effect on the improvement in moisture susceptibility in terms of both the freeze-thaw splitting strength ratios and the residual Marshall stability of asphalt mixtures containing Sasobit warm mix additive. The SFE of asphalt binders extracted from Sasobit warm mix increased with the aging time and temperature. The moisture susceptibility of the asphalt mixtures and binders containing Sasobit warm mixes was similar to or even greater than that of HMA aging under certain conditions. Bo Li, Jinyu Yang, Xiaohui Li, Xiang Liu, Feng Han, and Liangying Li Copyright © 2015 Bo Li et al. All rights reserved. Freeze-Thaw Performance and Moisture-Induced Damage Resistance of Base Course Stabilized with Slow Setting Bitumen Emulsion-Portland Cement Additives Sun, 29 Nov 2015 13:19:49 +0000 Freeze-thaw (FT) cycles and moisture susceptibility are important factors influencing the geotechnical characteristics of soil-aggregates. Given the lack of published information on the behavior of cement-bitumen emulsion-treated base (CBETB) under environmental conditions, especially freezing and thawing, this study investigated the effects of these additives on the CBETB performance. The primary goal was to evaluate the resistance of CBETB to moisture damage by performing FT, Marshall conditioning, and AASHTO T-283 tests and to evaluate the long-term stripping susceptibility of CBETB while also predicting the liquid antistripping additives to assess the mixture’s durability and workability. Specimens were stabilized with Portland cement (0%–6%), bitumen emulsion (0%–5%), and Portland cement-bitumen emulsion mixtures and cured for 7 days, and their short- and long-term performances were studied. Evaluation results of both the Marshall stability ratio and the tensile strength ratio show that the additions of additives increase the resistance of the mixtures to moisture damage. Results of durability tests performed for determining the resistance of compacted specimens to repeated FT cycles indicate that the specimen with the 4% cement-3% bitumen emulsion mixture significantly improves water absorption, volume changes, and weight losses. This indicates the effectiveness of this additive as a road base stabilizer with excellent engineering properties for cold regions. Mojtaba Shojaei Baghini and Amiruddin Ismail Copyright © 2015 Mojtaba Shojaei Baghini and Amiruddin Ismail. All rights reserved. Preparation and Characterization of Amorphous B Powders by Salt-Assisted SHS Technique Sun, 29 Nov 2015 12:29:15 +0000 To use the salt-assisted SHS technique to prepare B powders was proposed. Calculation results found that the adiabatic combustion temperature of the B2O3-Mg reaction system was 2604 K, higher than the 1800 K criterion of self-propagating temperature, which meant that the SHS application was feasible. When 0, 10%, 20%, 30%, 40%, 50%, and 60% NaCl content were added, the adiabatic combustion temperature of the reaction system decreased linearly. When 60% NaCl content was added, the adiabatic combustion temperature was 1799 K (lower than 1800 K), unsuitable for self-propagating reaction, which was consistent with the experimental results. Through scanning electron microscope (SEM), energy disperse spectroscopy (EDS), and particle size analysis, the influence of different addition of NaCl on the morphology, average particle size, and purity of prepared B powder was investigated. EDS and chemical analysis indicated that the purity of prepared B powder was over 96% and the average particle size was within the range of 0.4~0.8 μm when the content of NaCl was 50%. The analysis of X-ray diffraction (XRD) and selected area electron diffraction (SAED) proved that the prepared B powder was amorphous. Yujing Ou, Peiqing La, Dandan Zhu, and Yalong Zhu Copyright © 2015 Yujing Ou et al. All rights reserved. Influence of Bottom Ash Replacements as Fine Aggregate on the Property of Cellular Concrete with Various Foam Contents Sun, 29 Nov 2015 11:47:30 +0000 This research focuses on evaluating the feasibility of utilizing bottom ash from coal burning power plants as a fine aggregate in cellular concrete with various foam contents. Flows of all mixtures were controlled within 45 ± 5% and used foam content at 30%, 40%, 50%, 60%, and 70% by volume of mixture. Bottom ash from Mae Moh power plant in Thailand was used to replace river sand at the rates of 0%, 25%, 50%, 75%, and 100% by volume of sand. Compressive strength, water absorption, and density of cellular concretes were determined at the ages of 7, 14, and 28 days. Nonlinear regression technique was developed to construct the mathematical models for predicting the compressive strength, water absorption, and density of cellular concrete. The results revealed that the density of cellular concrete decreased while the water absorption increased with an increase in replacement level of bottom ash. From the experimental results, it can be concluded that bottom ash can be used as fine aggregate in the cellular concrete. In addition, the nonlinear regression models give very high degree of accuracy (). Patchara Onprom, Krit Chaimoon, and Raungrut Cheerarot Copyright © 2015 Patchara Onprom et al. All rights reserved. A Simple-to-Implement Simulator for the Reactive Extrusion of Poly(Lactic Acid) in a Corotating Uniform Twin-Screw Extruder Thu, 26 Nov 2015 14:25:07 +0000 The present paper deals with the poly(lactic acid) (PLA) reactive processing simulation in a uniform corotating twin-screw extruder that can be readily turned into practical applications in pilot and industrial equipment. The simulator provides a cause-effect guide that can be useful for starting an experimental setup in a reactive screw extruder for a biopolymer in a growing industry. The proposed model considers a free radical ring-opening mechanism involving the main characteristic flows inside the extruder and the non-Newtonian behavior of PLA. The characteristic behavior relating reaction rate, average molecular weights, and polydispersity against chamber number are described by S-shaped and monotonically decreasing curves, for the equipment. Numerical predictions show that this simple and easy to implement model accurately reproduces previously reported data and that the impurity concentration exhibits a marked effect over all the variables, except conversion. René O. Vargas, J. Esteban López-Aguilar, Lorenzo A. Martínez-Suástegui, and Francisco López-Serrano Copyright © 2015 René O. Vargas et al. All rights reserved. Durability Study on High Calcium Fly Ash Based Geopolymer Concrete Thu, 26 Nov 2015 12:21:58 +0000 This study presents an investigation into the durability of geopolymer concrete prepared using high calcium fly ash along with alkaline activators when exposed to 2% solution of sulfuric acid and 5% magnesium sulphate for up to 45 days. The durability was also assessed by measuring water absorption and sorptivity. Ordinary Portland cement concrete was also prepared as control concrete. The grades chosen for the investigation were M20, M40, and M60. The alkaline solution used for present study is the combination of sodium silicate and sodium hydroxide solution with the ratio of 2.50. The molarity of sodium hydroxide was fixed as 12. The test specimens were  mm cubes,  mm cylinders, and  mm discs cured at ambient temperature. Surface deterioration, density, and strength over a period of 14, 28, and 45 days were observed. The results of geopolymer and ordinary Portland cement concrete were compared and discussed. After 45 days of exposure to the magnesium sulfate solution, the reduction in strength was up to 12% for geopolymer concrete and up to 25% for ordinary Portland cement concrete. After the same period of exposure to the sulphuric acid solution, the compressive strength decrease was up to 20% for geopolymer concrete and up to 28% for ordinary Portland cement concrete. Ganesan Lavanya and Josephraj Jegan Copyright © 2015 Ganesan Lavanya and Josephraj Jegan. All rights reserved. Research and Correlation of Diagnostic Methods for Assessment of the State of Oil Filling in Cycloid Gearbox Thu, 26 Nov 2015 09:50:16 +0000 The paper describes the research in the area of the application of diagnostic methods for assessment of the state of oil filling in cycloid gearbox of robotic manipulator. The experiments were realized on request of the manufacturer of the cycloid gearbox. Primarily, the two different methods were compared: an induction, magnetic method with the use of measurement system Cosmos-Steel Dust Checker and an RTG method, XRF (X-ray fluorescent method, analyses with use of X-ray radiation). These analytical methods provide the identification and quantification of emerging Fe abrasion particles occurring in the oil filling of the redactor. The results of the experiment pointed to the unsuitability of the application of the induction magnetic method for the assessment of an actual technical state of the cycloid gearbox. The reason for this lies in specific construction of the cycloid gearbox, with characteristic high operation temperatures of the oil filling, small dimensions, high transferred power, and gear ratio. Petr Baron, Marek Kočiško, Jozef Dobránsky, Martin Pollák, and Tomáš Cmorej Copyright © 2015 Petr Baron et al. All rights reserved. Analysis of Compressive Toughness and Deformability of High Ductile Fiber Reinforced Concrete Wed, 25 Nov 2015 12:49:11 +0000 The compressive toughness evaluation index of HDC (high ductile fiber reinforced concrete) is studied through three groups of uniaxial compressive tests of HDC specimens with different fiber mixing amounts, and an equivalent analysis of their deformability is carried out, coming to the following conclusion: the peak strain of HDC under uniaxial compression can be up to 3.41~3.67 times as large as that of the mortar matrix; the equivalent compressive toughness index reflects the unit volume deformation energy of specimens under uniaxial compression and it can be used as the compressive toughness evaluation index of HDC; the fiber bridging effect of HDC increases the equivalent compressive toughness index and the compressive deformability up to 3 times of the mortar matrix; the relationship between the equivalent compressive toughness index and the fiber mixing amount is established according to the test results; and the fiber bridging effect of the matrix in HDC can be equaling as a large number of constraint stirrups installed in the specimens, which significantly enhances the compressive toughness and the compressive deformability of specimens. Mingke Deng, Jian Han, Haibo Liu, Meng Qin, and Xingwen Liang Copyright © 2015 Mingke Deng et al. All rights reserved. Influence of Antioxidant-Enhanced Polymers in Bitumen Rheology and Bituminous Concrete Mixtures Mechanical Performance Tue, 24 Nov 2015 11:57:38 +0000 This paper evaluates the effect of polymer enhancement with antioxidant in the rheological properties of bitumen and mechanical properties of bituminous concrete mixture (BCM). In this study, two antioxidant-enhanced polymers were utilized in mitigating bitumen hardening due to aging. The rheological testing consists of temperature sweep using Dynamic Shear Rheometer at various aging conditions. Critical stiffness temperature data from the sweep test suggested that enhanced polymer exhibits less long-term hardening and brittleness compared to standard polymer. The mechanical testing consists of dynamic modulus, indirect tensile, flow number, and beam fatigue tests on BCM exposed to short-term aging. Hamburg wheel tracking test was also performed to assess moisture-damage susceptibility. It is found that the enhanced-polymer BCM exhibited higher modulus, higher tensile strength ratio, improved rutting resistance, lower moisture-damage susceptibility, and slightly increased fatigue life as compared to standard-polymer BCM. Samer Dessouky, Mohammad Ilias, Dae-Wook Park, and In Tai Kim Copyright © 2015 Samer Dessouky et al. All rights reserved. Preparation and Characteristic of PC/PLA/TPU Blends by Reactive Extrusion Tue, 24 Nov 2015 11:28:24 +0000 To overcome the poor toughness of PC/PLA blends due to the intrinsic properties of materials and poor compatibility, thermoplastic urethane (TPU) was added to PC/PLA blends as a toughener; meantime, catalyst di-n-butyltin oxide (DBTO) was also added for catalyzing transesterification of components in order to modify the compatibility of blends. The mechanical, thermal, and rheological properties of blends were investigated systematically. The results showed that the addition of TPU improves the toughness of PC/PLA blends significantly, with the increase of TPU, the elongation at break increases considerably, and the impact strength increases firstly and then falls, while the tensile strength decreases significantly and the blends exhibit a typical plastic fracture behavior. Meantime, TPU is conducive to the crystallinity of PLA in blends which is inhibited seriously by PC and damages the thermal stability of blends slightly. Moreover, the increased TPU makes the apparent viscosity of blends melt decrease due to the well melt fluidity of TPU; the melt is closer to the pseudoplasticity melt. Remarkably, the transesterification between the components improves the compatibility of blends significantly, and more uniform structure results in a higher crystallinity and better mechanical properties. Yueyun Zhou, Lifa Luo, Wenyong Liu, Guangsheng Zeng, and Yi Chen Copyright © 2015 Yueyun Zhou et al. All rights reserved. Research Difference of Strain Distribution and Microstructure Evolution between Rolling Direction and Transverse Direction of AM50 Mg Alloy Plate by Digital Image Correlation Tue, 24 Nov 2015 08:02:38 +0000 The rolling direction (RD) and transverse direction (TD) of AM50 Mg alloy plate were drawn by tensile test while Digital Image Correlation (DIC) was applied to record local strain distribution and evolution. Then, the microstructure in the maximum strain position was observed so as to find the reason causing the difference between RD and TD specimen. Finally, the fracture surface morphology of the broken specimen was observed by scanning electron microscope (SEM) to determine the crack types. Through the analysis, it is found that the critical failure equivalent strains in the RD specimen and TD specimen are 0.1675 and 0.118, respectively, and the maximum equivalent strain position is the crack source; more twinning is generated in the RD specimen than that of the TD specimen, which indicates that twinning plays an important role in affecting its plasticity. The fracture surface morphology indicates that the RD specimen fracture is quasi-cleavage fracture while the TD specimen shows character of cleavage fracture. Qiang Li, Fuan Hua, Jianping Li, and Hao Wang Copyright © 2015 Qiang Li et al. All rights reserved. Study of Direct Bonding Ceramics with Metal Using Sn2La Solder Sun, 22 Nov 2015 06:21:08 +0000 The aim of this research was to study the direct bonding of ceramic materials, mainly Al2O3 and selected metals, with primary attention given to Cu substrate. Soldering was performed with Sn-based solder alloyed with 2% La. We found that the bond formation between Sn2La solder and Al2O3 occurs at the activation of lanthanum phases in solder by ultrasound. Lanthanum in the solder becomes oxidised in air during the soldering process. However, due to ultrasonic activation, the lanthanum particles are distributed to the boundary with ceramic material. A uniformly thin layer containing La, 1.5 µm in thickness, is formed on the boundary with Al2O3 material, ensuring both wetting and joint formation. The shear strength with Al2O3 ceramics is 7.5 MPa. Increased strength to 13.5 MPa was observed with SiC ceramics. Roman Koleňák and Igor Kostolný Copyright © 2015 Roman Koleňák and Igor Kostolný. All rights reserved. Thermogravimetry-Infrared Spectroscopy Analysis of the Pyrolysis of Willow Leaves, Stems, and Branches Thu, 19 Nov 2015 12:42:21 +0000 The pyrolysis of willow samples from various plant positions was analysed using thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR). The results indicate that pyrolysis can be divided into four stages. The first stage from 30 to 120°C involves free evaporation of moisture, with a mass loss of 5%. The second stage from 120 to 200°C involves the pyrolysis of hemicellulose and unstable cellulose, with a mass loss of 4%. The third stage is from 200 to 400°C, with a weight loss of 60%, in which the chemical components of wood thermally decompose and emit heat, carbon dioxide, and so on. In the final stage, which occurs above 400°C, the pyrolysis of lignin and charring of cellulose occur, with a mass loss of 10%. Moreover, in FTIR, the samples exhibit the highest absorbance during the main pyrolysis phase, from which wood vinegar ingredients mainly arise, including CO2, H2O, CO, and small amounts of hydrocarbons, alcohols, phenols, acids, esters, and aromatic compounds. Additionally, leaves are decomposed more thoroughly before the main pyrolysis phase, whereas decomposition of branches occurs fullest during this phase. Finally, we put forward some suggestions to support further research on conversion of willow into wood vinegar products. Zhen Liu, Na Qi, Yaning Luan, and Xiangyang Sun Copyright © 2015 Zhen Liu et al. All rights reserved. Performance Characteristic of Cold Recycled Mixture with Asphalt Emulsion and Chemical Additives Tue, 17 Nov 2015 13:54:34 +0000 Three types of chemical additives were used to modify asphalt emulsion recycled mixture. These chemical additives include composite Portland cement (CPC), hydrated lime (HL), and a combination of hydrated lime and ground-granulated blast-furnace slag (GGBF). The influence of different additives on the recycled mixture performance was investigated by volumetric and strength tests, moisture susceptibility test, rutting resistance test, and low temperature bending test. To better understand its performance characteristic, the microstructure images of the recycled mixture were observed by environmental scanning electron microscope (ESEM). Test results demonstrate that the performance improvement of the emulsion recycled mixture depends on the types and content of chemical additives. Several recommendations are presented for the selection of chemical materials. Based on ESEM image analysis, the interface bonding mechanism is proposed to explain the performance characteristic of the recycled mixture with asphalt emulsion and cementitious materials. Shaowen Du Copyright © 2015 Shaowen Du. All rights reserved. Effects of Concentrical Partial (Local) Compression on the Structural Behavior of Concrete Filled Steel Tubular Column Mon, 16 Nov 2015 08:58:40 +0000 The objective of this present paper is to investigate the structural behavior of square and circular Concrete Filled Steel Tubular (CFST) stub columns subjected to axial partial/local compression. The experimental parameters were local compression area and section type. Among the twelve specimens, six specimens were tested under full compression and the remaining six specimens were tested under local compression. The experimental observation indicated that the failure pattern of the CFST column with partial compression is fairly different from the CFST column subjected to full compression. The confinement provided by the circular section is quite different than the confinement provided by the square section, when the CFST column is subjected to axially local compression. It was found that the elastic modulus (stiffness) and the ultimate bearing capacity of the CFST column decreased with the increase in local compression ratio. The circular and square CFST columns subjected to partial/local compression achieved an ultimate strength of 4.45% and 14.15%, respectively, less than that of the columns subjected to full compression. From the above observation, it can be inferred that the structural performance of the CFST column is significantly influenced by the local area compression ratio and this effect should be taken into account in design models. S. Jayaganesh, J. Raja Murugadoss, G. Ganesh Prabhu, and J. Jegan Copyright © 2015 S. Jayaganesh et al. All rights reserved. Continuous Flow Controlled Synthesis of Gold Nanoparticles Using Pulsed Mixing Microfluidic System Mon, 16 Nov 2015 08:11:19 +0000 To prepare the gold nanoparticles (AuNPs) with uniform sizes, fine morphology, and good monodispersity, a pulsed mixing microfluidic system based on PZT actuation was presented. The system includes PZT micropump and Y type micromixer. By adjusting voltage (entrance flow rate), pulsed frequency, phase, and other parameters, a variety of mixing modes can be achieved, so as to realize the controllable synthesis of nanoparticles in a certain range. By numerical simulation and analysis, the channel section size, entrance angle, and pulse frequency were optimized. Based on the optimized structure and working parameters, the test prototype has been manufactured in lab, and the related synthesis tests of AuNPs were carried out. The test results indicate that AuNPs with uniform morphology and good monodispersity can be synthesized using the system with the section size (0.4 mm × 0.4 mm), the entrance channel angle (60°) under condition of the pulsed frequency (300 Hz), and the entrance flow rate (4 mL/min). The average diameter and its standard deviation of AuNPs synthesized were 21.6 nm, 4.83 nm, respectively. The research work above can be applied to the fields such as the controlled synthesis of noble metal nanoparticles, biomedicine, and microchemical system. Guojun Liu, Xuhao Yang, Yan Li, Zhigang Yang, Wen Hong, and JianFang Liu Copyright © 2015 Guojun Liu et al. All rights reserved. A Three-Phase Interleaved Floating Output Boost Converter Wed, 11 Nov 2015 09:48:39 +0000 High step-up dc-dc converter is an essential part in several renewable energy systems. In this paper, a new topology of step-up dc-dc converter based on interleaved structure is proposed. The proposed converter uses three energy storing capacitors to achieve a high voltage gain. Besides the high voltage gain feature, the proposed converter also reduces the voltage stress across the semiconductor switches. This helps in using low rating switching devices which can reduce the overall size and cost of the converter. The operating principle of the proposed converter is discussed in detail and its principle waveforms are analyzed. An experiment is carried out on a 20 V input, 130 V output, and 21 W power prototype of the proposed converter in the laboratory to verify the performance of the proposed converter. An efficiency of 91.3% is achieved at the rated load. Ajmal Farooq, Zeeshan Malik, Dongchang Qu, Zhaohui Sun, and Guozhu Chen Copyright © 2015 Ajmal Farooq et al. All rights reserved. Study on Repaired Earthquake-Damaged Bridge Piers under Seismic Load Tue, 10 Nov 2015 12:58:09 +0000 The concrete bridge pier damaged during earthquakes need be repaired to meet the design standards. Steel tube as a traditional material or FRP as a novel material has become popular to repair the damaged reinforced concrete (RC) bridge piers. In this paper, experimental and finite element (FE) studies are employed to analyze the confinement effectiveness of the different repair materials. The FE method was used to calculate the hysteretic behavior of three predamaged circle RC bridge piers repaired with steel tube, basalt fiber reinforced polymer (BFRP), and carbon fiber reinforced polymer (CFRP), respectively. Meanwhile, the repaired predamaged circle concrete bridge piers were tested by pseudo-static cyclic loading to study the seismic behavior and evaluate the confinement effectiveness of the different repair materials and techniques. The FE analysis and experimental results showed that the repaired piers had similar hysteretic curves with the original specimens and all the three repair techniques can restore the seismic performance of the earthquake-damaged piers. Steel tube jacketing can significantly improve the lateral stiffness and peak load of the damaged pier, while the BFRP and CFRP sheets cannot improve these properties due to their thin thickness. Jun Deng, Tonghua Liu, Weizhi Xie, and Wei Lu Copyright © 2015 Jun Deng et al. All rights reserved. Corrosion Inhibiting Mechanism of Nitrite Ion on the Passivation of Carbon Steel and Ductile Cast Iron for Nuclear Power Plants Mon, 09 Nov 2015 11:02:28 +0000 While NaNO2 addition can greatly inhibit the corrosion of carbon steel and ductile cast iron, in order to improve the similar corrosion resistance, ca. 100 times more NaNO2 addition is needed for ductile cast iron compared to carbon steel. A corrosion and inhibition mechanism is proposed whereby ion is added to oxidize. The ion can be reduced to nitrogen compounds and these compounds may be absorbed on the surface of graphite. Therefore, since nitrite ion needs to oxidize the surface of matrix and needs to passivate the galvanic corroded area and since it is absorbed on the surface of graphite, a greater amount of corrosion inhibitor needs to be added to ductile cast iron compared to carbon steel. The passive film of carbon steel and ductile cast iron, formed by NaNO2 addition showed N-type semiconductive properties and its resistance, is increased; the passive current density is thus decreased and the corrosion rate is then lowered. In addition, the film is mainly composed of iron oxide due to the oxidation by ion; however, regardless of the alloys, nitrogen compounds (not nitrite) were detected at the outermost surface but were not incorporated in the inner oxide. K. T. Kim, H. W. Kim, H. Y. Chang, B. T. Lim, H. B. Park, and Y. S. Kim Copyright © 2015 K. T. Kim et al. All rights reserved. Reactions of Al-PTFE under Impact and Quasi-Static Compression Sun, 08 Nov 2015 09:43:10 +0000 Conventionally, the Al-PTFE is thought to be inert under quasi-static or static loads. However, here we reported an initiation phenomenon of Al-PTFE under quasi-static compression. Quasi-static tests suggest that reacted Al-PTFE samples had much higher toughness than unreacted samples. Dynamic test showed that the energy level needed to initiate the material was similar for quasi-static compression (88–100 J) and dynamic impact (77–91 J). The difference in density indicates that unreacted Al-PTFE has a higher crystallinity, which leads to the lower toughness. SEM images show numerous PTFE fibrils in unreacted composites which made the sample harder to crack and initiate. Bin Feng, Xiang Fang, Yu-chun Li, Shuang-zhang Wu, Yi-ming Mao, and Huai-xi Wang Copyright © 2015 Bin Feng et al. All rights reserved. Manufacture of Locally Reinforced Composite Discs by Casting in the Alternating Electromagnetic Field Sun, 08 Nov 2015 07:00:09 +0000 The paper discusses a new method of obtaining local particle reinforcement in the composite discs. In this method, the liquid composite suspension is poured into a mould and then exposed to the alternating electromagnetic field. The Lorentz force acting on the liquid metal causes the reinforcement to move towards one or both surfaces of the manufactured disc. The paper presents the process theory, the methodology for the casting system design, and the results of an experimental manufacture of one-side and two-side reinforced composite discs made of aluminium alloy. Slawomir Golak Copyright © 2015 Slawomir Golak. All rights reserved. A Modified Comprehensive Model for Piezoelectric Stack Actuators and Corresponding Parameter Identification Method Thu, 05 Nov 2015 07:39:12 +0000 In order to accurately model the hysteresis and dynamic characteristics of piezoelectric stack actuators (PSAs), consider that a linear force and a hysteresis force will be generated by piezoelectric wafers under the voltage applied to a PSA, and the total force suffering from creep will result in the forced vibration of the two-degree-of-freedom mass-spring-damper system composed of the equivalent mass, stiffness, and damping of the piezoelectric wafers and the bonding layers. A modified comprehensive model for PSAs is put forward by using a linear function, an asymmetrical Bouc-Wen hysteresis operator, and a creep function to model the linear force, the hysteresis force, and the creep characteristics, respectively. In this way, the effect of the bonding layers on the hysteresis and dynamic characteristics of PSAs can be analyzed via the modified comprehensive model. The experimental results show that the modified comprehensive model for PSAs with the corresponding parameter identification method can accurately portray the hysteresis and dynamic characteristics of PSAs fabricated by different layering/stacking processes. Finally, the theoretical analyzing on utilizing the modified comprehensive model to linearize the hysteresis characteristics and design the dynamic characteristics of PSAs is given. Haigen Yang and Wei Zhu Copyright © 2015 Haigen Yang and Wei Zhu. All rights reserved. Biomimetic Coating of Modified Titanium Surfaces with Hydroxyapatite Using Simulated Body Fluid Thu, 05 Nov 2015 06:57:12 +0000 This study investigated the viability of coating commercially pure titanium (CPTi) surfaces, modified via sandblasting and acid etching, with hydroxyapatite (HA)/tricalcium phosphate coatings using a simulated body fluid (SBF) solution. The samples were immersed in SBF from 3 to 7 days. The morphology and the chemistry of the HA/tricalcium phosphate coating were then analysed. Prior to immersion in SBF, the samples were sandblasted and acid etched to mimic the morphology and roughness of commercially available dental implants. The SBF aided in the formation of crystalline HA/tricalcium phosphate coatings on all the samples. The coatings were uniform and had roughness values higher than the underlying substrate. The highest roughness values for the coatings on the surfaces were obtained at 7 days of immersion in SBF with average values of 2.9 ± 0.2 µm. The presence of HA/tricalcium phosphate on the surfaces was confirmed by the Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS), the X-Ray Diffraction (XRD), and the Fourier Transform Infrared Spectrometer (FTIR) analysis. This study shows that it is possible to obtain an adequate and uniform hydroxyapatite coating on pure titanium substrates in a shorter period of time with characteristics that favour the ultimate goal of implants therapy, that is, osseointegration. Mohsin Nazir, Ong Pei Ting, Tan See Yee, Saravanan Pushparajan, Dasan Swaminathan, and Muralithran G. Kutty Copyright © 2015 Mohsin Nazir et al. All rights reserved. Preparation and Characterization of Nickel Ferrite-SiO2/Ag Core/Shell Nanocomposites Tue, 03 Nov 2015 08:59:21 +0000 Magnetic composites with silver nanoparticles bonded to their surface were successfully prepared using a simple chemical method. By means of a sol-gel technique, nickel ferrite nanoparticles have been prepared and coated with silica to control and avoid their magnetic agglomeration. The structural and magnetic properties of the nanoparticles were studied in function of the annealing temperature. Then, silver nanoparticles were incorporated by hydrolysis-condensation of tetraethyl orthosilicate, which contains silver nitrate on the surface of the nickel ferrite-SiO2 core/shell. Samples were characterized using X-ray diffraction, IR spectroscopy, SEM, and magnetometry. Results show that the silica covered the nickel ferrite nanoparticles and the silver nanoparticles remain stable in the surface of the composite. I. G. Blanco-Esqueda, G. Ortega-Zarzosa, J. R. Martínez, and A. L. Guerrero Copyright © 2015 I. G. Blanco-Esqueda et al. All rights reserved. The Influence of Abutment Surface Treatment and the Type of Luting Cement on Shear Bond Strength between Titanium/Cement/Zirconia Wed, 28 Oct 2015 13:20:01 +0000 Objectives. The objectives of this study were to evaluate the shear bond strength of zirconia cylinders on a modified titanium surface using different luting cement types. Material and Methods. Eighty titanium disks were divided into two groups (), which were treated with either grinding or a combination of sandblasting and grinding. Then, each group was subdivided into 4 groups () and the disks were bonded to disks of sintered zirconia using one of four cement types (permanent: composite cement; temporary: polycarboxylate cement, zinc-oxide-eugenol cement, and resin cement). Shear bond strength (SBS) was measured in a universal testing machine. Fracture pattern and site characteristic were recorded. A fractographic analysis was performed with SEM. The chemical analysis of the composition of the fractures was performed using energy-dispersive X-ray spectroscopy (EDS). The results of the experiment were analyzed with two-way analysis of variance and Tukey post hoc test. Results. The highest mean values of SBS were achieved when grinding was combined with sandblasting and when composite cement was used (18.18 MPa). In the temporary cement group, the highest mean values of SBS were for polycarboxylate cement after grinding (3.57 MPa). Conclusion. The choice of cement has a crucial influence on the titanium-cement-zirconia interface quality. Beata Śmielak, Marcin Gołębiowski, and Leszek Klimek Copyright © 2015 Beata Śmielak et al. All rights reserved. Implementation of Virtual Crack Closure Technique for Damaged Composite Plates Using Higher-Order Layerwise Model Wed, 28 Oct 2015 11:12:35 +0000 A higher-order layerwise model is proposed to determine stress intensity factors using virtual crack closure technique for single-edge-crack aluminum plates with patch repairs. The present method is based on -convergent approach and adopts the concept of subparametric elements. In assumed displacement fields, strain-displacement relations and three-dimensional constitutive equations of layers are obtained by combination of two- and one-dimensional shape functions. Thus, it allows independent implementation of -refinement for in-plane and transversal displacements. In the proposed elements, the integrals of Legendre polynomials and Gauss-Lobatto technique are employed to interpolate displacement fields and to implement numerical quadrature, respectively. For verification of the present model, not only single-edge-crack plates but also V-notch aluminum plates are first analyzed. For patched aluminum plate with behavior of complexity, the accuracy and simplicity of the present model are shown with comparison of the results with previously published papers using the conventional three-dimensional finite elements based on -refinement. Kwang S. Woo and Jae S. Ahn Copyright © 2015 Kwang S. Woo and Jae S. Ahn. All rights reserved. An Experimental Study on Concrete Flat Slabs Prestressed with Carbon Fibre Reinforced Polymer Sheets Wed, 28 Oct 2015 07:25:54 +0000 Carbon fibre reinforced polymer (CFRP) is currently used to reinforce buildings in civil engineering in the common forms of sheets, while the utilization efficiency of a CFRP materials greatly decreased when the CFRP material is directly bonded to the structure because of the lack of the effect of the exertion of a prestress. A paper spool-inspired anchoring method is proposed to overcome the shearing problem in the anchoring system through the friction between layers. Anchoring and jack-up tensioning devices for CFRP sheets are also designed and produced. A prestress is successfully applied to single and multiple CFRP sheets (80% tensioning strength is achieved), thus verifying the tensioning effect of the prestress. Based on these results, prestressed concrete flat slabs were designed with pretensioned CFRP sheets. The corresponding mechanical properties of the concrete flat slabs are tested to verify the feasibility of using CFRP sheets to apply a prestress. The results show that the uniformity of the fibre stress during the tensioning of the CFRP sheet is the key to the success of the application of the prestress. Yin Shen, Shaohui Lu, and Fangyuan Li Copyright © 2015 Yin Shen et al. All rights reserved. Microstructural Characterization of Beryllium Treated Al-Si Alloys Tue, 27 Oct 2015 08:04:11 +0000 The present study was carried out on B356 and B357 alloys using the thermal analysis technique. Metallographic samples prepared from these castings were examined using optical microscopy and FESEM. Results revealed that beryllium causes partial modification of the eutectic Si, similar to that reported for magnesium additions. Addition of 0.8 wt.% Mg reduces the eutectic temperature by ~10°C. During solidification of alloys containing high levels of Fe and Mg, but no Sr, formation of a Be-Fe phase was detected at 611°C, close to that of α-Al. The Be-Fe phase precipitates in script-like form at or close to the β-Al5SiFe platelets. A new reaction, composed of fine particles of Si and π-Fe phase, was observed to occur near the end of solidification in high Mg-, high Fe-, and Be-containing alloys. The amount of this reaction decreased with the addition of Sr. Occasionally, Be-containing phase particles were observed as part of the reaction. Addition of Be has a noticeable effect on decreasing the β-Al5FeSi platelet length; this effect may be enhanced by addition of Sr. Beryllium addition also results in precipitation of the β-Al5FeSi phase in nodular form, which lowers its harmful effects on the alloy mechanical properties. M. F. Ibrahim, S. A. Alkahtani, Kh. A. Abuhasel, and F. H. Samuel Copyright © 2015 M. F. Ibrahim et al. All rights reserved. Prediction of the Service Life of a Reinforced Concrete Column under Chloride Environment Mon, 26 Oct 2015 11:34:38 +0000 In the present investigation, service life of a reinforced concrete column exposed to chloride environment has been predicted. This study has been based on numerical simulation of chloride ion diffusion in a concrete column during its anticipated life span. The simulation process has included the concrete cover replacement whenever chloride ion concentration has reached the critical threshold value at the reinforcement surface. Repair scheduling of the concrete column under consideration has been discussed. Effects of the concrete cover thickness and the water cement ratio on the service life of the concrete column at hand have been presented. A new approach for arranging locations of reinforcement steel bars has been introduced. This approach is intended to prolong the service life of the concrete column under consideration against chloride induced corrosion. Mohammad K. Alkam and Maha Alqam Copyright © 2015 Mohammad K. Alkam and Maha Alqam. All rights reserved. Bond Yield Characteristics of Undisturbed Completely Decomposed Granite Thu, 22 Oct 2015 12:02:12 +0000 To investigate the bond yield characteristics of undisturbed completely decomposed granite (CDG) which is widely distributed in Southern China, a series of conventional drained tests were conducted. From the test data, some insights are obtained as follows: for undisturbed CDG soils, the bond yield point during shearing could be identified on the curve of the normalized tangential stiffness versus axial strain on log-log scale. The consolidation pressure has a significant influence on the bond yield characteristics of undisturbed CDG during shearing, the bonds inside undisturbed CDG tend to be damaged relatively more seriously as is higher, accordingly the initial normalized stiffness will be smaller at the beginning of the shearing process, and the axial strain at the bond yield point will also be smaller. Once consolidation pressure excesses a critical value such as 475 kPa for this studied CDG, the bonds inside soil will be damaged totally at the consolidation compression stage. In this case, there will be no bond yield occurring during shearing and the curves will coincide with the ones of reconstituted CDG soil. For reconstituted soils, no bond yielding was observed during shearing; the curves are tightly consistent with no dependence of the value of . Pan Liu, Xiaowen Zhou, and Yongbin He Copyright © 2015 Pan Liu et al. All rights reserved.