Advances in Materials Science and Engineering The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. The Impact of Traffic-Induced Bridge Vibration on Rapid Repairing High-Performance Concrete for Bridge Deck Pavement Repairs Wed, 19 Nov 2014 09:29:04 +0000 Based on forced vibration tests for high-performance concrete (HPC), the influence of bridge vibration induced by traveling vehicle on compressive strength and durability of HPC has been studied. It is concluded that 1 d and 2 d compressive strength of HPC decreased significantly, and the maximum reduction rate is 9.1%, while 28 d compressive strength of HPC had a slight lower with a 3% maximal drop under the action of two simple harmonic vibrations with 2 Hz, 3 mm amplitude, and 4 Hz, 3 mm amplitude. Moreover, the vibration had a slight effect on the compressive strength of HPC when the simple harmonic vibration had 4 Hz and 1 mm amplitude; it is indicated that the amplitude exerts a more prominent influence on the earlier compressive strength with the comparison of the frequency. In addition, the impact of simple harmonic vibration on durability of HPC can be ignored; this shows the self-healing function of concrete resulting from later hydration reaction. Thus, the research achievements mentioned above can contribute to learning the laws by which bridge vibration affects the properties of concrete and provide technical support for the design and construction of the bridge deck pavement maintenance. Wei Wang, Shuo Liu, Qizhi Wang, Wei Yuan, Mingzhang Chen, Xiaotian Hao, Shuai Ma, and Xuanyu Liang Copyright © 2014 Wei Wang et al. All rights reserved. Correlation between Electrochemical Impedance Spectroscopy and Structural Properties of Amorphous Tunisian Metanacrite Synthetic Material Mon, 17 Nov 2014 12:27:57 +0000 In the present work, we report the structural and electrochemical properties of metanacrite. Metanacrite is a synthetic material originated by heating (550°C) of a clay mineral (Tunisian nacrite) belonging to the kaolin group. The structure of the amorphous synthetic product was corroborated by X-ray diffraction (disappearing of nacrite peaks) and infrared spectroscopy (disappearing of Al–OH and water bands). The decomposition of the silicate framework was confirmed by transmission electron microscope (TEM). The obtained metanacrite synthetic material was also examined by electrochemical impedance spectroscopy (EIS). Accordingly, the electronic conduction is followed by the correlated barrier hopping (C.B.H.) model. Therefore, by combining ac and dc electrical conductivity, a semiconductor behavior is evidenced. The dependence of the dielectric constant () and dielectric loss () on both temperature and frequency is also discussed. Nouha Jaafar, Hafsia Ben Rhaiem, and Abdessalem Ben Haj Amara Copyright © 2014 Nouha Jaafar et al. All rights reserved. A Novel Sintered Stainless Steel Fiber Felt with Rough Surface Morphologies Thu, 13 Nov 2014 11:23:53 +0000 A novel sintered stainless steel fiber felt (SSSFF) with rough surface morphologies and high strength as well as high porosity is fabricated by solid-state sintering of stainless steel fibers produced by cutting method. The rough surface morphologies are characterized by laminar and jagged structures formed on the surface of stainless steel fibers. The SSSFF with 85% porosity sintered at 1200°C for 60 min exhibits tensile strength of 19 MPa and yield stress of 10.5 MPa. The influence of sintering parameters on surface morphologies and tensile strength is investigated. The experimental results show that the rough surface structures will disappear gradually when sintering temperature is 1300°C or sintering time is excessive, that is, 240 min when sintering temperature is 1200°C. The SSSFF with high porosity presents high tensile strength when sintering temperature ranges from 1100°C to 1200°C and sintering time is from 60 min to 120 min. In addition, the fracture mechanism of the SSSFF is investigated when subjected to uniaxial tensile load. Chaobin Fang, Zhenping Wan, Bin Liu, and Longsheng Lu Copyright © 2014 Chaobin Fang et al. All rights reserved. Review of Mechanics and Applications of Auxetic Structures Thu, 13 Nov 2014 00:00:00 +0000 One of the important mechanical properties of materials is Poisson’s ratio, which is positive for most of the materials. However, certain materials exhibit “auxetic” properties; that is, they have a negative Poisson’s ratio. Thus auxetic and non-auxetic materials exhibit different deformation mechanisms. A specific microscopic structure in the auxetic materials is important for maintaining a negative Poisson’s ratio. Based on their distinct nature auxetic materials execute certain unique properties in contrast to other materials, which are reviewed in this paper. Thus auxetic materials have important applications in the biomedical field which are also a part of this review article. Many auxetic materials have been discovered, fabricated, and synthesized which differ on the basis of structure, scale and deformation mechanism. The different types of auxetic materials such as auxetic cellular solids, microscopic auxetic polymers, molecular auxetic materials, and auxetic composites have been reviewed comprehensively in this paper. Modeling of auxetic structures is of considerable importance and needs appropriate stress strain configurations; thus different aspects of auxetic modeling have also been reviewed. Packing parameters and relative densities are of prime importance in this regard. This review would thus help the researchers in determining and deciding the various aspects of auxetic nature for their products. Mariam Mir, Murtaza Najabat Ali, Javaria Sami, and Umar Ansari Copyright © 2014 Mariam Mir et al. All rights reserved. Macroscopic and Microscopic Mechanisms of Cement-Stabilized Soft Clay Mixed with Seawater by Adding Ultrafine Silica Fume Thu, 13 Nov 2014 00:00:00 +0000 The strength of the cement-stabilized soil can be improved by the use of seawater. Compressive strength test results show that the strength of cement-stabilized soil mixed with seawater is 50% greater than that mixed with freshwater at the 90th day. However, the application is limited because the expansion of the cement-stabilized soil mixed with seawater increases significantly. A kind of ultrafine silica fume was added into the cement-stabilized soil to inhibit swelling of the cement-stabilized soil with seawater. The expansion of cement-stabilized soil mixed with seawater by adding ultrafine silica fume is close to that of cement-stabilized soil mixed with freshwater. With the addition of ultrafine silica fume, the unconfined compressive strength increases by close to 6.5% compared with seawater alone at the 90th day. The mechanisms of adding ultrafine silica fume into the cement-stabilized soil mixed with seawater are revealed by several physical and chemical characterization parameters, such as specific gravity, unbound water content, surface morphology seen with SEM, and crystal products by X-ray diffraction tests. The results show that the crystal growth is an important factor, affecting the strength and expansion of cement-stabilized soil mixed with seawater. Qiang Li, Jie Chen, Qian Shi, and Shihao Zhao Copyright © 2014 Qiang Li et al. All rights reserved. A Study on Load Carrying Capacity of Fly Ash Based Polymer Concrete Columns Strengthened Using Double Layer GFRP Wrapping Wed, 12 Nov 2014 00:00:00 +0000 This paper investigates the suitability of glass fiber reinforced polymer (GFRP) sheets in strengthening of fly ash based polymer members under compression. Experimental results revealed that load carrying capacity of the confined columns increases with GFRP sheets wrapping. Altogether 18 specimens of M30 and G30 grade short columns were fabricated. The G30 specimens were prepared separately in 8 molarity and 12 molarity of sodium hydroxide concentration. Twelve specimens for low calcium fly ash based reinforced polymer concrete and six specimens of ordinary Portland cement reinforced concrete were cast. Three specimens from each molarity fly ash based reinforced polymer concrete and ordinary Portland cement reinforced concrete were wrapped with double layer of GFRP sheets. The load carrying capacity of fly ash based polymer concrete was tested and compared with control specimens. The results show increase in load carrying capacity and ductility index for all strengthened elements. The maximum increase in load carrying capacity was 68.53% and is observed in strengthened G30 specimens. S. Nagan and S. Karthiyaini Copyright © 2014 S. Nagan and S. Karthiyaini. All rights reserved. An Experimental Study on Strength and Durability for Utilization of Fly Ash in Concrete Mix Tue, 11 Nov 2014 12:07:00 +0000 The intention of this study is to discuss the variation of concrete exposed to high sulfate environment of a specific region with respect to strength and durability. Secondly, it is aimed to discuss the possibility of reducing the cement amount in construction of concrete structures. For this purpose, laboratory tests were conducted to investigate compressive strength and sulfate resisting capacity of concrete by using 20% fly ash as mineral additives, waste materials, instead of cement. As a case study the soil samples, received from Siirt Province areas which contain high sulfate rate, have been compared with respect to sulfate standard parameters of TS 12457-4. In such regions contact of underground water seep into hardened concrete substructures poses a risk of concrete deterioration. In order to determine the variation of strength and durability for concrete exposed to such aggressive environment, the samples were rested in a solution of Na2SO4 (150 g/lt) in accordance with ASTM C 1012 for the tests. As a result of this experimental study, it is noted that the use of 20% fly ash, replacement material instead of cement, has no significant effect on compressive strength of concrete over time. Abdulhalim Karaşin and Murat Doğruyol Copyright © 2014 Abdulhalim Karaşin and Murat Doğruyol. All rights reserved. Compressive Strength of Compacted Clay-Sand Mixes Thu, 06 Nov 2014 07:28:05 +0000 The use of sand to improve the strength of natural clays provides a viable alternative for civil infrastructure construction involving earthwork. The main objective of this note was to investigate the compressive strength of compacted clay-sand mixes. A natural clay of high plasticity was mixed with 20% and 40% sand (SP) and their compaction and strength properties were determined. Results indicated that the investigated materials exhibited a brittle behaviour on the dry side of optimum and a ductile behaviour on the wet side of optimum. For each material, the compressive strength increased with an increase in density following a power law function. Conversely, the compressive strength increased with decreasing water content of the material following a similar function. Finally, the compressive strength decreased with an increase in sand content because of increased material heterogeneity and loss of sand grains from the sides during shearing. Faseel Suleman Khan, Shahid Azam, Mavinakere Eshwaraiah Raghunandan, and Ryan Clark Copyright © 2014 Faseel Suleman Khan et al. All rights reserved. Sintering of Hydroxyapatite/Yttria Stabilized Zirconia Nanocomposites under Nitrogen Gas for Dental Materials Wed, 05 Nov 2014 11:48:16 +0000 This study aims to determine the effect of adding 3 mol% yttria stabilized zirconia (3YSZ) in hydroxyapatite (HA) and sintering HA/3YSZ nanocomposites under nitrogen gas on HA decomposition. This paper presents the relationship between microstructure and mechanical properties of HA/3YSZ nanocomposites. Gas pressure and conventional sintering were performed on HA/3YSZ nanocomposites containing different amounts of 3YSZ (i.e., 0, 0.5, 1, and 7 wt%) at 1250°C. The phase stability, morphology, relative density, and microhardness of the HA/3YSZ nanocomposites were investigated. The phase stability of the HA/3YSZ nanocomposites was affected by adding different amounts of 3YSZ. Overall, gas pressure sintering leads to the formation of greater grain size compared with the conventional sintering method. The severe HA decomposition and the presence of the porosity in HA/7 wt% 3YSZ have led to deterioration in relative density and microhardness. In this study, HA/0.5 wt% 3YSZ with gas pressure sintering exhibited the optimum microstructure with the highest relative density (97%) and microhardness (3.93 GPa). C. H. Leong, A. Muchtar, C. Y. Tan, M. Razali, and Noor Faeizah Amat Copyright © 2014 C. H. Leong et al. All rights reserved. Influence of Heat Treatment on Residual Stress in Cold-Forged Parts Thu, 30 Oct 2014 07:25:00 +0000 Residual stresses are those stresses that remain in a body when there is no external load applied. Numerous factors can induce residual stresses in the material, including cold forming. Thermal treatments of steel are widely used because they can improve the mechanical properties of the steel, such as toughness, tenacity, and resistance; however, thermal treatments can also produce residual stresses. This study aims to analyze the residual stresses present in a cold-forged part after heat treatments. Half-cylinder samples of AISI 1045 steel were cold-forged, and a wedge tool was pressed into their surface, causing a strain gradient. The samples were then heat-treated by annealing, normalizing, quenching, or quenching and tempering. A numerical simulation was also performed to aid in choosing the measurement points in the samples. The results show that residual stresses are dependent on the heat treatment and on the intensity and nature of previous residual stresses in the body. Frederico Ozanan Neves, Thiago Luis Lara Oliviera, Durval Uchoas Braga, and Alex Sander Chaves da Silva Copyright © 2014 Frederico Ozanan Neves et al. All rights reserved. Prediction of Three-Dimensional Milling Forces Based on Finite Element Tue, 28 Oct 2014 00:00:00 +0000 The model of milling force is mainly proposed to predict and analyze the cutting process based on finite element method in this paper. Firstly, milling finite element model is given based on orthogonal cutting principle, and then the influence laws of cutting parameters on chip formation are analyzed by using different simulation parameters. In addition, the three-dimensional milling forces are obtained from finite element models. Finally, the values of milling force by the milling experiment are also compared and analyzed with the simulation values to verify the feasibility and reasonability. It can be shown that milling forces match well between simulation and experiment results, which can provide many good basic data and analysis methods to optimize the machining parameters, reduce tool wear, and improve the workpiece surface roughness and adapt to the programming strategy of high speed machining. Lida Zhu, Chunxia Zhu, Jiaying Pei, Xuebing Li, and Wei Wang Copyright © 2014 Lida Zhu et al. All rights reserved. Biochar Preparation, Characterization, and Adsorptive Capacity and Its Effect on Bioavailability of Contaminants: An Overview Mon, 27 Oct 2014 08:36:51 +0000 This paper provides an updated review on the subjects, the available alternative to produce biochar from biomass, quantification and characterization of biochar, the adsorptive capacity for the adsorption of contaminants, and the effect of biochar addition to agricultural soils on contaminant bioavailability. The property of biochar produced is much dependent upon the composition and type of biomass and the conditions at which biomass is carbonized. The physical and chemical characterizations are necessary to identify the basic structure and property of biochar and to predict its potential in various environmental application. Biochar is a promising alternative to remedy the soils contaminated with heavy metals and organic compounds through adsorption and immobilization due to its large surface area, charged surface, and functional groups. Overall, the bioavailability of heavy metals and organic compounds decreases when biochar is amended into soils. Obemah D. Nartey and Baowei Zhao Copyright © 2014 Obemah D. Nartey and Baowei Zhao. All rights reserved. Mechanical Behavior of Interface between Composite Geomembrane and Permeable Cushion Material Wed, 22 Oct 2014 12:54:11 +0000 An accurate description of composite geomembrane-cushion interface behavior is of great importance for stress-deformation analysis and stability assessment of geomembrane surface barrier of rock-fill dam. A series of direct shear tests were conducted to investigate the friction behaviors of interfaces between composite geomembrane and two different permeable cushion materials (crushed stones and polyurethane mixed crushed stones). The shear stress-displacement relationships of the two interfaces show different characteristics and were described by the nonlinear-elastic model and nonlinear-elastic perfectly plastic model, respectively. Then the two models were implemented into the Fast Lagrangian Analysis of Continua in Three Dimensions () procedure correctly. By verification of a numerical example, numerical calculation results showed a good agreement with the theoretical solutions and test results. Haimin Wu, Yiming Shu, Linjun Dai, and Zhaoming Teng Copyright © 2014 Haimin Wu et al. All rights reserved. The Influence of Aggregate Size and Binder Material on the Properties of Pervious Concrete Tue, 21 Oct 2014 07:50:47 +0000 Specimens were prepared by altering parameters such as aggregate sizes, binder materials, and the amounts of binder used and were subsequently tested by using permeability, porosity, mechanical strength, and soundness tests. The results indicated that the water permeability coefficient and connected porosity decreased as the amount of binder used increased and increased with increasing aggregate size. In the mechanical strength test, the compressive, splitting tensile, and flexural strengths increased as the amount of binder used increased and decreased with the increase of aggregate size. Highly viscous binder enhanced compressive strength, water permeability, and the resistance to sulfate attacks. In the mechanics and sulfate soundness tests, the mix proportion of alkali-activated slag paste used in this study exhibited a superior performance than the Portland cement pervious concrete (the control) did, but the difference in water permeability between the two types of concrete was insignificant. The mix proportions of cement paste containing 20% and 30% silica fume exhibited less mechanical strength than the control did. Moreover, compared with the control, the cement paste containing silica fume demonstrated poor resistance to sulfate attacks, and the difference in the water permeability between such specimen and the control was not noticeable. Tun Chi Fu, Weichung Yeih, Jiang Jhy Chang, and Ran Huang Copyright © 2014 Tun Chi Fu et al. All rights reserved. Fiber Bragg Grating-Based Performance Monitoring of Piles Fiber in a Geotechnical Centrifugal Model Test Tue, 21 Oct 2014 00:00:00 +0000 In centrifugal tests, conventional sensors can hardly capture the performance of reinforcement in small-scale models. However, recent advances in fiber optic sensing technologies enable the accurate and reliable monitoring of strain and temperature in laboratory geotechnical tests. This paper outlines a centrifugal model test, performed using a 60 g ton geocentrifuge, to investigate the performance of pipe piles used to reinforce the loess foundation below a widened embankment. Prior to the test, quasidistributed fiber Bragg grating (FBG) strain sensors were attached to the surface of the pipe piles to measure the lateral friction resistance in real time. Via the centrifuge actuator, the driving of pipe piles was simulated. During testing, the variations of skin friction distribution along the pipe piles were measured automatically using an optical fiber interrogator. This paper represents the presentation and detailed analysis of monitoring results. Herein, we verify the reliability of the fiber optic sensors in monitoring the model piles without affecting the integrity of the centrifugal model. This paper, furthermore, shows that lateral friction resistance developed in stages with the pipe piles being pressed in and that this sometimes may become negative. Xiaolin Weng, Jianxun Chen, and Jun Wang Copyright © 2014 Xiaolin Weng et al. All rights reserved. Microstructural Characterization and Wear Properties of Fe-Based Amorphous-Crystalline Coating Deposited by Twin Wire Arc Spraying Mon, 20 Oct 2014 08:54:56 +0000 Twin wire arc spraying (TWAS) was used to produce an amorphous crystalline Fe-based coating on AISI 1018 steel substrate using a commercial powder (140MXC) in order to improve microhardness and wear properties. The microstructures of coating were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) as well as the powder precursor. Analysis in the coating showed the formation of an amorphous matrix with boron and tungsten carbides randomly dispersed. At high amplifications were identified boron carbides at interface boron carbide/amorphous matrix by TEM. This kind of carbides growth can be attributed to partial crystallization by heterogeneous nucleation. These interfaces have not been reported in the literature by thermal spraying process. The measurements of average microhardness on amorphous matrix and boron carbides were 9.1 and 23.85 GPa, respectively. By contrast, the microhardness values of unmelted boron carbide in the amorphous phase were higher than in the substrate, approaching 2.14 GPa. The relative wear resistance of coating was 5.6 times that of substrate. These results indicate that the twin wire arc spraying is a promising technique to prepare amorphous crystalline coatings. Ana Arizmendi-Morquecho, Araceli Campa-Castilla, C. Leyva-Porras, Josué Almicar Aguilar Martinez, Gregorio Vargas Gutiérrez, Karla Judith Moreno Bello, and L. López López Copyright © 2014 Ana Arizmendi-Morquecho et al. All rights reserved. Dynamic Recrystallization Behavior of TA15 Titanium Alloy under Isothermal Compression during Hot Deformation Sun, 19 Oct 2014 13:21:39 +0000 In order to improve the understanding of the dynamic recrystallization (DRX) behaviors of TA15 titanium alloy (Ti-6Al-2Zr-1Mo-1V), a series of experiments were conducted on a TMTS thermal simulator at temperatures of 1173 K, 1203 K, 1223 K, and 1273 K with the strain rates of 0.005 s−1, 0.05 s−1, 0.5 s−1, and 1 s−1. By the regression analysis for conventional hyperbolic sine equation, the activation energy of DRX in two-phase region is and in region is , and a dimensionless parameter controlling the stored energy was determined as in two-phase region and as in region. The DRX behaviors of TA15 titanium alloy were proposed on the strength of the experiment results. Finally, the theoretical prediction results of DRX volume fraction were shown to be in agreement with experimental observations. Yuanxin Luo, Yuqing Heng, Yongqin Wang, and Xingchun Yan Copyright © 2014 Yuanxin Luo et al. All rights reserved. Performance of BFRP Retrofitted RCC Piles Subjected to Axial Loads Sun, 19 Oct 2014 13:05:45 +0000 This paper deals with the behaviour of basalt fibre reinforced polymer (BFRP) composites retrofitted RCC piles subjected to axial compression loads. Currently the awareness of using FRP increases rapidly in engineering fields and also among public. Retrofitting becomes vital for aged and damaged concrete structures, piles, and so forth, to improve its load carrying capacity and to extend the service life. The load carrying capacity of piles retrofitted with basalt unidirectional fabric was studied experimentally. 15 nos. of RCC end bearing pile elements were cast with same reinforcement for axial compression experiment. Three piles were used as conventional elements, another 3 piles were used as double BFRP wrapped pile elements, and remaining 9 piles were used as retrofitted piles with BFRP double wrapping after preloaded to 30%, 60%, and 90% of ultimate load of conventional element. The effects of retrofitting of RCC pile elements were observed and a mathematical prediction was developed for calculation of retrofitting strength. The stress vs. strain relationship curve, load vs. deformation curve, preloaded elements strength losses are tabulated and plotted. Besides, crack patterns of conventional elements and tearing BFRP wrapped elements were also observed. The BFRP wrapped elements and retrofitted elements withstand more axial compressive load than the conventional elements. Anandakumar Ramaswamy, Selvamony Chachithanantham, and Seeni Arumugam Copyright © 2014 Anandakumar Ramaswamy et al. All rights reserved. Experimental Study of Ultralight (<300 kg/m3) Foamed Concrete Wed, 15 Oct 2014 11:26:15 +0000 A type of ultralight (<300 kg/m3) foamed concrete (FC), which can be used as a new energy-conservation and environmental-protection building material and is particularly suitable for the thermal-insulation engineering of building external walls, was produced. The influences of different mixing amounts of fly ash, fly ash activator, WC (WC) ratio, and foaming agent (FA) on the compressive strength of FC were reported. The experimental study indicated that (1) the addition of fly ash reduced the strength of the FC and that the appropriate mixing amount of fly ash in this ultralight FC system should not exceed 45%; (2) with the increasing of fly ash activator, the strength of the FC sample is notably enhanced and the appropriate mixing amount of fly ash activator is 2.5%; (3) the optimized proportion of WC ratio is 0.45, and the FC that was produced according to this proportion has relatively high compressive strength; (4) by increasing the mixing amount of FA, the compressive strength of the FC notably decreases, and the optimal mixing amount of FA in this experiment is 3.5%. Xianjun Tan, Weizhong Chen, Yingge Hao, and Xu Wang Copyright © 2014 Xianjun Tan et al. All rights reserved. Preparation of Flame Retardant Modified with Titanate for Asphalt Binder Wed, 15 Oct 2014 09:55:52 +0000 Improving the compatibility between flame retardant and asphalt is a difficult task due to the complex nature of the materials. This study explores a low dosage compound flame retardant and seeks to improve the compatibility between flame retardants and asphalt. An orthogonal experiment was designed taking magnesium hydroxide, ammonium polyphosphate, and melamine as factors. The oil absorption and activation index were tested to determine the effect of titanate on the flame retardant additive. The pavement performance test was conducted to evaluate the effect of the flame retardant additive. Oxygen index test was conducted to confirm the effect of flame retardant on flame ability of asphalt binder. The results of this study showed that the new composite flame retardant is more effective in improving the compatibility between flame retardant and asphalt and reducing the limiting oxygen index of asphalt binder tested in this study. Bo Li, Jianxun Liu, Feng Han, Xiaoling Li, Liangying Li, Yanbo Li, and Xiaofeng Duan Copyright © 2014 Bo Li et al. All rights reserved. Effect of Aerogel Particle Concentration on Mechanical Behavior of Impregnated RTV 655 Compound Material for Aerospace Applications Wed, 15 Oct 2014 00:00:00 +0000 Aerogels are a unique class of materials with superior thermal and mechanical properties particularly suitable for insulating and cryogenic storage applications. It is possible to overcome geometrical restrictions imposed by the rigidity of monolithic polyurea cross-linked silica aerogels by encapsulating micrometer-sized particles in a chemically resistant thermally insulating elastomeric “sleeve.” The ultimate limiting factor for the compound material’s performance is the effect of aerogel particles on the mechanical behavior of the compound material which needs to be fully characterized. The effect of size and concentration of aerogel microparticles on the tensile behavior of aerogel impregnated RTV655 samples was explored both at room temperature and at 77 K. Aerogel microparticles were created using a step-pulse pulverizing technique resulting in particle diameters between 425 μm and 90 μm and subsequently embedded in an RTV 655 elastomeric matrix. Aerogel particle concentrations of 25, 50, and 75 wt% were subjected to tensile tests and behavior of the compound material was investigated. Room temperature and cryogenic temperature studies revealed a compound material with rupture load values dependent on (1) microparticle size and (2) microparticle concentration. Results presented show how the stress elongation behavior depends on each parameter. Firouzeh Sabri, Jeffrey G. Marchetta, K. M. Rifat Faysal, Andrew Brock, and Esra Roan Copyright © 2014 Firouzeh Sabri et al. All rights reserved. Finite Element Modeling of Crack Generation in Laser Shock Peening Processed Airfoils Mon, 13 Oct 2014 12:22:57 +0000 Laser shock peening (LSP) is a surface treatment process for airfoils that is achieved by the induction of compressive stress. While LSP is a mature and reliable surface treatment process, slight anomalies during the process, or variations in material ductility and geometries, may cause unintended formation of small subsurface cracks in the resultant LSP processed material. In this study, we developed a 3D FEM model to simulate the formation and predict the sizes of cracks generated by inappropriate LSP processing in airfoil specimens in order to avoid producing such subsurface cracks. The Johnson-Cook plastic material model along with the consideration of effects of high strain rate was used to describe the plasticity of Ti alloys. The constants in this plastic model have been optimized with experimental data. The FEM model also includes both damage initiation and evolution criteria to simulate cracks generated by LSP process in the specimens. The simulated crack sizes and locations in the specimens have been validated by the experimental results. Fang Li, Xue Qi, and Dan Xiang Copyright © 2014 Fang Li et al. All rights reserved. Structural Modification of Sol-Gel Synthesized V2O5 and TiO2 Thin Films with/without Erbium Doping Mon, 13 Oct 2014 11:59:06 +0000 Comparative work of with/without erbium- (Er-) doped vanadium pentoxide (V2O5) and titanium dioxide (TiO2) thin films were carried out via sol-gel technique by dissolving erbium (III) nitrate pentahydrate (Er(NO3)3·5H2O) in vanadium (V) oxoisopropoxide (OV[OCH(CH3)2]3) and titanium (IV) isopropoxide (Ti[OCH(CH3)2]4). Effect of Er doping was traced by Fourier transform IR (FTIR), thermogravimetric/differential thermal (TG/DTA), and photoluminescence measurements. UV-Vis transmission/absorption measurement indicated a blue shift upon Er doping in V2O5 film due to the softening of V=O bond while appearance of typical absorption peaks in Er-doped TiO2 film. Granule size of the films increased (reduced) upon Er substitution on host material compared to undoped V2O5 and TiO2 films, respectively. Fatma Pınar Gökdemir, Ayşe Evrim Saatci, Orhan Özdemir, and Kubilay Kutlu Copyright © 2014 Fatma Pınar Gökdemir et al. All rights reserved. Effect of Chopped Basalt Fibers on the Mechanical Properties and Microstructure of High Performance Fiber Reinforced Concrete Mon, 13 Oct 2014 09:07:09 +0000 This paper presents the mechanical properties and the microstructure of the high performance fiber reinforced concrete (HPFRC) containing up to 3% volume fraction of chopped Basalt fibers. Three types of the concrete were prepared, out of which, the first type was prepared by utilizing 100% cement content. The other two types of the concrete were prepared by replacing 10% cement content with silica fume and the locally produced metakaolin. Using each concrete type, four mixes were prepared in which Basalt fibers were added in the range of 0–3%; that is, total twelve mixes of the HPFRC concrete were prepared. From each of the twelve concrete mixes, total twelve specimens were cast to determine the mechanical properties of the HPFRC including compressive strength (cube and cylinder), splitting tensile strength, and the flexural strength. In this way, a total of 108 specimens were cast and tested in this study. Test results showed that the addition of the Basalt fibers significantly increased the tensile splitting strength and the flexural strength of the HPFRC, while there was slight improvement in the compressive strength with the addition of Basalt fibers. The microstructure of HPFRC was examined to determine the interfacial transition zone (ITZ) between the aggregates and the paste by using field emission scanning electron microscope (FESEM), which showed the improvement of the ITZ due to the addition of the Basalt fibers. Tehmina Ayub, Nasir Shafiq, and M. Fadhil Nuruddin Copyright © 2014 Tehmina Ayub et al. All rights reserved. Compressive Behaviour of RC Column with Fibre Reinforced Concrete Confined by CFRP Strips Mon, 13 Oct 2014 09:01:44 +0000 The structural application of synthetic fibre reinforced concrete (FRC) has become widespread in the construction industry in order to satisfy the requirement of the earthquake resistant structures. Research conducted so far are focused on the structural behaviour of RC column externally confined with FRP composites, while studies are needed to address the behaviour of FRP strengthened RC column fabricated using fibre reinforced concrete. With the intention that the experimental investigation was carried out to evaluate the feasibility use of CFRP composite strips in strengthening of RC column made with fibre reinforced concrete. Circular synthetic Polypropylene fibre was used in the rate of 0.50% in the volume of concrete. CFRP strips having a width of 50 mm were used to confine the column and the experimental parameters were effective spacing between the CFRP strips (20 mm and 30 mm) and the number of CFRP layers (one, two and three). The externally bonded CFRP strips counteract the lateral expansion of the concrete significantly by providing restraining effect and thus effect enhanced the stiffness of the column. The column strengthened with CFRP strips showed a maximum of 198.87% and 91.75% enhancement in axial deformation control and ultimate strength, respectively, compared to that of reference column. From the test results obtained, it is suggested that CFRP strips with the spacing of 20 mm and 30 mm can be used in strengthening of RC column made with FRC; however the column confined with 30 mm spacing provides an economical advantage compared to that of 20 mm spacing. A. M. Vasumathi, K. Rajkumar, and G. Ganesh Prabhu Copyright © 2014 A. M. Vasumathi et al. All rights reserved. Material Characterization of Strontium Ferrite Powders for Producing Sintered Magnets by Ceramic Injection Molding (MagnetPIM) Mon, 13 Oct 2014 08:06:29 +0000 For this study, different strontium ferrite powders were mixed with a filling ratio of about 60 vol% in a binder system and formed into green compacts. During the process of injection molding, a magnetic field was generated in the tool via a magnetic coil, which enables magnetization and orientation of the ceramic particles. All powders were successfully processed by MagnetPIM. The investigations identified that it is impossible to extrapolate from the magnetic properties of a green compact to the magnetic properties of a sintered part. It became obvious, though, that, when producing very strong magnetic parts by MagnetPIM, the best results can be obtained by using powders with small particle sizes. Dietmar Drummer and Susanne Messingschlager Copyright © 2014 Dietmar Drummer and Susanne Messingschlager. All rights reserved. Development of Pd Alloy Hydrogen Separation Membranes with Dense/Porous Hybrid Structure for High Hydrogen Perm-Selectivity Mon, 13 Oct 2014 07:29:51 +0000 For the commercial applications of hydrogen separation membranes, both high hydrogen selectivity and permeability (i.e., perm-selectivity) are required. However, it has been difficult to fabricate thin, dense Pd alloy composite membranes on porous metal support that have a pore-free surface and an open structure at the interface between the Pd alloy films and the metal support in order to obtain the required properties simultaneously. In this study, we fabricated Pd alloy hydrogen separation membranes with dense/porous hybrid structure for high hydrogen perm-selectivity. The hydrogen selectivity of this membrane increased owing to the dense and pore-free microstructure of the membrane surface. The hydrogen permeation flux also was remarkably improved by the formation of an open microstructure with numerous open voids at the interface and by an effective reduction in the membrane thickness as a result of the porous structure formed within the Pd alloy films. Jae-Yun Han, Chang-Hyun Kim, Sang-Ho Kim, and Dong-Won Kim Copyright © 2014 Jae-Yun Han et al. All rights reserved. Cyclic Load Responses of GFRP-Strengthened Hollow Rectangular Bridge Piers Mon, 13 Oct 2014 07:06:45 +0000 This study investigated the seismic behavior of glass fiber reinforced polymer (GFRP) strengthened hollow rectangular bridge piers. Cyclic testing of reinforced concrete (RC) piers retrofitted with GFRP was carried out under constant axial loading and lateral bending. The failure characteristics, flexural ductility, dissipated energy, and hysteretic behaviors, were analyzed based on experimental results. A simplified GFRP-confined concrete model is developed by considering effective strength coefficient and area distribution ratio of GFRP sheets. The results indicate that the failure modes and damage region would be changed and the ductility and dissipated energy of the GFRP-strengthened hollow rectangular bridge piers were improved greatly but not much improvement for the lateral load capacity. The analytical results of the force-displacement hysteretic loops based on the GFRP-confined concrete model developed in this paper agreed well with the experimental data. Junfeng Jia, Qiang Han, Zigang Xu, and Dongjie Zhang Copyright © 2014 Junfeng Jia et al. All rights reserved. Research on Static Triaxial Mechanical Properties of New CementSoil Reinforced with Polypropylene Fiber Sun, 12 Oct 2014 09:46:20 +0000 Through the laboratory test, the mechanical properties of cementsoil with adding desulfurization gypsum, fly ash, and polypropylene fiber were studied. Three different percentages (0%, 0.5%, and 1.0%) of polypropylene fiber were mixed into new cementsoil for which the cement content is 15% of the dry soil weight, the desulfurization gypsum content is 2% of the dry soil weight, and the fly ash content is 1.0% of the dry soil weight. The new cementsoil strength reinforced with polypropylene fiber was studied by triaxial test under different polypropylene fiber mixing ratio, different age, and different confining pressure. The experimental results show that, compared with ordinary soil, the deviatoric stress and the peak shear strength reinforced with polypropylene fiber have different amplitude increase. At the same time, the internal friction angle of new cementsoil with polypropylene fiber increases slightly with the growth of the age. The stress-strain curve of the polypropylene fiber cementsoil has the typical work hardening characteristic and has the characteristics of bulge fracture. Qiang Wang, Rui Tang, Qun Cheng, Xiankun Wang, and Fang-ling Liu Copyright © 2014 Qiang Wang et al. All rights reserved. Current Development in Lead-Free -Based Piezoelectric Materials Sun, 21 Sep 2014 11:37:52 +0000 The lead-free piezoelectric ceramics display good piezoelectric properties which are comparable with Pb(Zr,Ti)O3 (PZT) and these materials overcome the hazard to the environment and human health. The Bi0.5(Na,K)0.5TiO3 (BNKT) is rapidly developed because of good piezoelectric, ferroelectric, and dielectric properties compared to PZT. The origin of giant strain of BNKT piezoelectric materials was found at morphotropic phase boundary due to crystal change from tetragonal to orthorhombic and/or precipitation of cubic phases, in addition to domain switching mechanism. The dopants or secondary phases with ABO3 structure as solid solution are expected to change the crystal structure and create the vacancies which results in enhancement of the piezoelectric properties. In this work, we reviewed the current development of BNKT by dopants and secondary phase as solid solution. Our discussion will focus on role of dopants and secondary phase to piezoelectric properties of BNKT. This result will open the direction to control the properties of lead-free piezoelectric materials. Ngo Duc Quan, Luong Huu Bac, Duong Van Thiet, Vu Ngoc Hung, and Dang Duc Dung Copyright © 2014 Ngo Duc Quan et al. All rights reserved.