Advances in Materials Science and Engineering The latest articles from Hindawi © 2017 , Hindawi Limited . All rights reserved. Design of Laser Welding Parameters for Joining Ti Grade 2 and AW 5754 Aluminium Alloys Using Numerical Simulation Mon, 16 Oct 2017 08:20:43 +0000 Joining of dissimilar Al-Ti alloys is very interesting from the point of view of weight reduction of components and structures in automotive or aerospace industries. In the dependence on cooling rate and chemical composition, rapid solidification of Al-Ti alloys during laser welding can lead to the formation of metastable phases and brittle intermetallic compounds that generally reduce the quality of produced weld joints. The paper deals with design and testing of welding parameters for preparation of weld joints of two sheets with different thicknesses from titanium Grade 2 and AW 5754 aluminium alloy. Temperature fields developed during the formation of Al-Ti butt joints were investigated by numerical simulation in ANSYS software. The influence of laser welding parameters including the laser power and laser beam offset on the temperature distribution and weld joint formation was studied. The results of numerical simulation were verified by experimental temperature measurement during laser beam welding applying the TruDisk 4002 disk laser. The microstructure of produced weld joints was assessed by light microscopy and scanning electron microscopy. EDX analysis was applied to determine the change in chemical composition across weld joints. Mechanical properties of weld joints were evaluated using tensile tests and Vickers microhardness measurements. Mária Behúlová, Eva Babalová, and Miroslav Sahul Copyright © 2017 Mária Behúlová et al. All rights reserved. Structure of Hybrid Interpolymeric Complexes of Polyvinyl Alcohol and Halides of Second Group Elements Mon, 16 Oct 2017 08:10:02 +0000 Density functional theory was used to investigate structure and properties of polyvinyl alcohol complexes with halides of second group elements XHal2 (X = Be, Mg, Ca, Zn, Sr, Cd, Ba, and Hg; Hal = F, Cl, Br, and I). PVA can form hybrid interpolymeric complexes with some of them. These complexes show double spiral structure of two types. I. Yu. Prosanov and E. Benassi Copyright © 2017 I. Yu. Prosanov and E. Benassi. All rights reserved. A Novel Silica-Nylon Mesh Reinforcement for Dental Prostheses Mon, 16 Oct 2017 00:00:00 +0000 Statement of the Problem. Acrylic resin-based dentures can fracture; thus they can benefit from reinforcement. Purpose. To evaluate the effect of a novel reinforcement structure made of nylon fibers and silica particles on the flexural strength of acrylic resin after relining and aging. Materials and Methods. Bar-shaped specimens were fabricated and divided into the following experimental groups (): control (acrylic resin without reinforcement); acrylic resin nylon fiber-reinforced; acrylic nylon and silica fiber-reinforced; acrylic nylon fiber-reinforced-relined; acrylic nylon and silica fiber-reinforced-relined. Half of the specimens from each group were aged by thermomechanical cycling (10000 cycles between 5°C and 55°C) before flexural strength testing to failure using a universal testing machine. Data (MPa) were statistically analyzed using analysis of variance and Tukey tests (). Results. Adding nylon fibers or silica-containing nylon fibers significantly increased the flexural strength of all the groups tested. Within the similar groups processed in the same manner, the relining procedure reduced the flexural strength of the specimens, whereas aging process had no effect on the strength values. Conclusion. Incorporating a silica-containing nylon fiber mesh into acrylic resin yielded the greatest flexural strength for the evaluated structures. Tarcisio José de Arruda Paes-Junior, Humberto Lago de Castro, Alexandre Luiz Souto Borges, Alvaro Della Bona, and Fernanda de Cássia Papaiz Gonçalves Copyright © 2017 Tarcisio José de Arruda Paes-Junior et al. All rights reserved. Deterioration and Microstructural Evolution of the Fly Ash Geopolymer Concrete against MgSO4 Solution Mon, 16 Oct 2017 00:00:00 +0000 Fly ash geopolymer concrete (FAGC) and ordinary Portland cement concrete (OPCC) specimens were immersed in 5% MgSO4 solution undergoing 32 wetting-drying and heating-cooling cycles. Their compressive behavior was investigated after every 8 cycles. Several microstructure analysis techniques were applied on the samples to identify the materials formed due to magnesium sulfate attack, including XRD, FTIR, SEM, and EDS. Experimental results elucidated that the compressive strength loss ratio in the heating group of FAGC was 12.7%, while that of OPCC was 17.8%, which means that FAGC had better magnesium sulfate resistance than OPCC. The compressive strength loss of OPCC was due to the formation of gypsum under the magnesium sulfate attack exposed to wetting-drying and heating-cooling cycles. The deterioration mechanisms of FAGC against MgSO4 solution were discovered to be that sodium aluminum silicate hydrate (N-A-S-H) gels reacted with MgSO4, leading to the creation of low strength magnesium aluminum silicate hydrate (M-A-S-H) gels. Tao Long, Qingyuan Wang, Zhongwei Guan, Yu Chen, and Xiaoshuang Shi Copyright © 2017 Tao Long et al. All rights reserved. Magnetization Reversal in Ferromagnetic Nanorings of Fourfold Symmetries Mon, 16 Oct 2017 00:00:00 +0000 Magnetic nanoparticles offer a broad spectrum of magnetization reversal processes and respective magnetic states, such as onion, horseshoe, or vortex states as well as various states including domain walls. These states can be correlated with stable intermediate states at remanence, enabling new quaternary memory devices storing two bits in one particle. The stability of these intermediated states was tested with respect to shape modifications, variations in the anisotropy axes, and rotations and fluctuations of the external magnetic field. In our micromagnetic simulations, 6 different stable intermediate states were observed at vanishing magnetic field in addition to the remanence state. The angular region of approx. 5°–12° between nanoring and external magnetic field was identified as being most stable with respect to all modifications, with an onion state as technologically best accessible intermediate state to create quaternary memory devices. Andrea Ehrmann and Tomasz Blachowicz Copyright © 2017 Andrea Ehrmann and Tomasz Blachowicz. All rights reserved. Mineralization Process of Biocemented Sand and Impact of Bacteria and Calcium Ions Concentrations on Crystal Morphology Thu, 12 Oct 2017 06:23:05 +0000 Microbial-induced calcite precipitation (MICP) is a sustainable technique used to improve sandy soil. Analysis of the mineralization process, as well as different bacterial suspensions and calcium concentrations on the crystal morphology, revealed that the mineralization process included four stages: self-organised hydrolysis of microorganisms, molecular recognition and interface interaction, growth modulation, and epitaxial growth. By increasing bacterial suspensions and calcium concentrations, the crystal morphology changed from hexahedron to oblique polyhedron to ellipsoid; the best crystal structure occurs at OD600 = 1.0 and [Ca2+] = 0.75 mol/l. It should be noted that interfacial hydrogen bonding is the main force that binds the loose sand particles. These results will help in understanding the mechanism of MICP. Guobin Xu, Yang Tang, Jijian Lian, Yue Yan, and Dengfeng Fu Copyright © 2017 Guobin Xu et al. All rights reserved. Modeling the Influence of the Penetration Channel’s Shape on Plasma Parameters When Handling Highly Concentrated Energy Sources Thu, 12 Oct 2017 00:00:00 +0000 In our work to formulate a scientific justification for process control methods when processing materials using concentrated energy sources, we develop a model that can calculate plasma parameters and the magnitude of the secondary waveform of a current from a non-self-sustained discharge in plasma as a function of the geometry of the penetration channel, thermal fields, and the beam’s position within the penetration channel. We present the method and a numeric implementation whose first stage involves the use of a two-dimensional model to calculate the statistical probability of the secondary electrons’ passage through the penetration channel as a function of the interaction zone’s depth. Then, the discovered relationship is used to numerically calculate how the secondary current changes as a distributed beam moves along a three-dimensional penetration channel. We demonstrate that during oscillating electron beam welding the waveform has the greatest magnitude during interaction with the upper areas of the penetration channel and diminishes with increasing penetration channel depth in a way that depends on the penetration channel’s shape. When the surface of the penetration channel is approximated with a Gaussian function, the waveform decreases nearly exponentially. Dmitriy N. Trushnikov, Ekaterina S. Salomatova, Igor I. Bezukladnikov, Igor L. Sinani, and K. P. Karunakaran Copyright © 2017 Dmitriy N. Trushnikov et al. All rights reserved. Effects of Shrinkage Reducing Agent and Expansive Additive on Mortar Properties Thu, 12 Oct 2017 00:00:00 +0000 This research is to study the effect of mortar mixed with shrinkage reducing agent (polyoxyalkylene alkyl ether type), expansive additive (CaO type), and fly ash (hereinafter “SRA,” “EX,” and “FA,” resp.). Moreover, steam curing was studied to improve the properties of mortar. The plastic shrinkage test was conducted by using the strain gauge embedded at 0.5 cm from the surface according to the ASTM C1579-06 standard within early age followed by the total shrinkage test and compressive strength test. The test results showed that mixing both the EX and SRA increases the plastic enlargement of the mortar during the early age more than using either the EX or SRA solely. The steam curing helps to reduce the plastic shrinkage when the mortar is added with the FA and SRA while adding the EX increases the enlargement compared to the normal curing. When the EX, SRA, and FA are all added to the mortar mixing, great attention should be paid due to the increase of greater enlargement. For the compressive strength view, the steam curing increases the compressive strength in all types of mixture. The steam curing significantly helps increasing the compressive strength of mortar with combination of EX, SRA, and FA. Nevertheless, the XRD and SEM tests explain such enlargement accordingly. Sarapon Treesuwan and Komsan Maleesee Copyright © 2017 Sarapon Treesuwan and Komsan Maleesee. All rights reserved. Optimal Shape Control of Piezoelectric Intelligent Structure Based on Genetic Algorithm Wed, 11 Oct 2017 00:00:00 +0000 Shape variation induced by mismachining tolerance, humidity and temperature of the working environment, material wear and aging, and unknown external load disturbances have a relatively large influence on the dynamic shape of a mechanical structure. When integrating piezoelectric elements into the main mechanical structure, active control of the structural shape is realized by utilizing the inverse piezoelectric effect. This paper presents a mathematical model regarding piezoelectric intelligent structure shape control. We also applied a genetic algorithm, and given a piezoelectric intelligent cantilever plate with both ends affected by a certain load, optimal shape control results of piezoelectric materials were analyzed from different perspectives (precision reference or cost reference). The mathematical model and results indicate that, by optimizing a certain number of piezoelectric actuators, high-precision active shape control can be realized. Zhanxi Wang, Xiansheng Qin, Shunqi Zhang, Jing Bai, Jing Li, and Genjie Yu Copyright © 2017 Zhanxi Wang et al. All rights reserved. Effect of (0001) Strain on the Electronic and Magnetic Properties of the Half-Metallic Ferromagnet Fe2Si Wed, 11 Oct 2017 00:00:00 +0000 The electronic and magnetic properties of the half-metallic ferromagnet Fe2Si under (0001) strain have been evaluated by the first-principles density functional theory method. The spin-up band structure shows that bulk Fe2Si has metallic character, whereas the spin-down band structure shows that bulk Fe2Si is an S-L indirect band gap of 0.518 eV in the vicinity of Fermi surface. Indirect-to-direct band gaps and an unstable-to-stable transition are observed in bulk Fe2Si as strain is applied. In the range −11% to 11% (excluding zero strain), bulk Fe2Si has stable half-metallic ferromagnetism, the spin polarization at the Fermi surface is 100%, and the magnetic moment of the Fe2Si unit cell is 4.0 μB. The density distribution shows that the spin states of bulk Fe2Si mainly come from the Fe1-3d and Fe3-3d states, indicating that bulk Fe2Si has spin-polarized ferromagnetism. The half-metallic ferromagnetism of bulk Fe2Si is mainly caused by d–d exchange and p–d hybridization, which are not sensitive to strain. It is very important to investigate the effect of changes in the lattice constant on the half-metallic ferromagnetic properties of bulk Fe2Si. Wang Chen, Ruijie Li, and Yanhui Liu Copyright © 2017 Wang Chen et al. All rights reserved. Evaluation and Analysis of Variance of Storage Stability of Asphalt Binder Modified by Nanotitanium Dioxide Tue, 10 Oct 2017 00:00:00 +0000 To investigate the effects of nanoparticle content, storage time, and storage temperature on the storage stability of asphalt binders modified by nanoparticles, hot tube storage tests, softening point tests, and dynamic-shearing rheometer (DSR) tests were adopted to evaluate the properties of two kinds of nanotitanium dioxide (TiO2) modified asphalt binders. A statistical one-way analysis of variance (ANOVA) test was employed to analyze the effects of those variations on the storage stability of the nano-TiO2 modified asphalt binders. The results indicated that the softening point, the failure temperature, the dynamic-shear viscosity, and of the binders increased with nanoparticle content. The storage stability of the binders decreased with nanoparticle content. The impact of storage time on the storage stability of the binders was remarkable when the storage time was more than 48 h. Moreover, the storage stability of the binders at low temperatures was better than that at high temperatures. Based on the one-way ANOVA, the size of nanoparticle had little influence on the storage stability of the nano-TiO2 modified asphalt binders in this study. Reducing the nanoparticle size cannot effectively enhance the storage stability of the nanoparticle modified asphalt binder due to the agglomeration of nanoparticle. Xiaolong Zou, Aimin Sha, Biao Ding, Yuqiao Tan, and Xiaonan Huang Copyright © 2017 Xiaolong Zou et al. All rights reserved. Utilization of Foaming Technology in Cemented Paste Backfill of High-Mud Superfine Unclassified Tailings Tue, 10 Oct 2017 00:00:00 +0000 Due to high-mud content in superfine unclassified tailings (SUT), the viscosity of cemented paste backfill (CPB) is high and its pipeline transportation properties are poor. Foaming technology was introduced to prepare a new three-phase flow backfill (TFB) using a foaming machine. Then the rheological parameters of TFB with different bubble ratio were measured and their pipeline transportation properties were simulated by Fluent. Besides, the simulation results were further verified by a semi-industrial loop test. The results indicate that the optimum ratio of TFB is a cement-sand ratio of 1 : 8, mass concentration of 70%, and bubble ratio of 20%. Compared with CPB, the decrease of bleeding rate, viscosity, and resistance loss of TFB is 27%, 25%, and 30%, respectively. Therefore, foaming technology is an innovative and feasible solution for high-mud CPB in reducing viscosity, decreasing resistance loss, and improving pipeline transporting efficiency. Jian-wen Zhao, Xin-min Wang, Kang Peng, and Shuai Li Copyright © 2017 Jian-wen Zhao et al. All rights reserved. Analysis of the Relationship between Density and Mechanical Strength of Lightened Gypsums: Proposal for a Coefficient of Lightening Tue, 10 Oct 2017 00:00:00 +0000 This article develops a relationship between the reduction of density in lightened gypsum and the addition of expanded and/or extruded polystyrene waste from the construction sector and their mechanical behavior. The equations determined in this study allow us to know the flexural and compressive strengths of a lightened gypsum/plaster compound once its density is known. The results show that there is an exponential relationship between the density of the compound and its strength. The methodology followed included a compilation of the results obtained in previous research works on lightweight gypsums, analyzing the relationship between density and mechanical strength and comparing them with the equations developed in this research. The results obtained by previous researchers have a good adjustment with the proposed models, and only perlite compounds present greater deviations in the compressive strength analysis. Also, a dimensionless lightening coefficient is defined which can help to determine the best application for a lightweight gypsum compound, comparing it with an ideal lightweight gypsum. Jaime Santa Cruz Astorqui, Mercedes del Río Merino, Paola Villoria Sáez, and César Porras-Amores Copyright © 2017 Jaime Santa Cruz Astorqui et al. All rights reserved. Analysis of Startup Process and Its Optimization for a Two-Stand Reversible Cold Rolling Mill Tue, 10 Oct 2017 00:00:00 +0000 Dynamic characteristic analysis of a two-stand reversible cold rolling mill in the startup process was carried out. The delay algorithm of the interstand thickness was proposed. A new method combined with the accelerated secant and the tangent methods was established to solve the simultaneous equations. The thickness and interstand tension transition processes with different static tension establishing processes were analyzed. Both mills were operated under constant rolling force control mode in the above process. The results show that the strip thickness in the rolling gap reduces in the static mill screwdown process. The entry stand runs inversely to establish the static interstand tension. This area becomes an abnormal thickness reduction area of the incoming strip. It results in several abnormal interstand tension increases in the subsequent startup process. The tension increase leads to an impact force on the strip that is the main reason of the strip breakage in the startup process. So the static tension establishing process was optimized, and the interstand tension fluctuation and the strip breakage accidents both reduced significantly. The results are beneficial to the startup process of the two-stand reversible cold rolling mill. Guangming Liu, Yugui Li, Qingxue Huang, Xia Yang, and Aimin Liu Copyright © 2017 Guangming Liu et al. All rights reserved. Effects of Montmorillonite on the Mineralization and Cementing Properties of Microbiologically Induced Calcium Carbonate Mon, 09 Oct 2017 00:00:00 +0000 Carbonate mineralization microbe is a microorganism capable of decomposing the substrate in the metabolic process to produce the carbonate, which then forms calcium carbonate with calcium ions. By taking advantage of this process, contaminative uranium tailings can transform to solid cement, where calcium carbonate plays the role of a binder. In this paper, we have studied the morphology of mineralized crystals by controlling the mineralization time and adding different concentrations of montmorillonite (MMT). At the same time, we also studied the effect of carbonate mineralized cementation uranium tailings by controlling the amount of MMT. The results showed that MMT can regulate the crystal morphology of calcium carbonate. What is more, MMT can balance the acidity and ions in the uranium tailings; it also can reduce the toxicity of uranium ions on microorganisms. In addition, MMT filling in the gap between the uranium tailings made the cement body more stable. When the amount of MMT is 6%, the maximum strength of the cement body reached 2.18 MPa, which increased by 47.66% compared with that the sample without MMT. Therefore, it is reasonable and feasible to use the MMT to regulate the biocalcium carbonate cemented uranium tailings. Tao Chen, Jiwei Li, Peiheng Shi, Yi Li, Jia Lei, Jian Zhou, Zuowen Hu, Tao Duan, Yongjian Tang, and Wenkun Zhu Copyright © 2017 Tao Chen et al. All rights reserved. Influence Parameters on Nitriding Process of Ferromanganese Alloy Wed, 04 Oct 2017 00:00:00 +0000 A 24 factorial design technique was used to investigate the magnitude effect of temperature, time, carbon percent, and pressure of the nitriding process of gas solid reaction of ferromanganese. The design was based on experiments results obtained from nitriding of two grades of ferromanganese alloys containing 0.23% C and 7.1% C at temperatures 700°C and 950°C, during time of 2 hours and 6 hours and with nitrogen pressure of 1 and 8 bar. The required calculations were carried out by Matlab. It was found that the highest positive effect was temperature while the carbon content has the highest negative effect. Nitrogen pressure has more positive effect than time. The interaction combination between two parameters or more of temperature, nitrogen pressure, and time has positive influence with different extent. The interaction combination between carbon and one or more of parameters of time, temperature, or nitrogen pressure has negative effect on nitriding process. The driven models were found to be in good agreement with the experiments and published work of nitriding process of ferromanganese containing different carbon contents (0.23–7.1%) in temperature range 700°C–950°C, with nitrogen pressure up to 8 bar, and during time of 2–6 hours. S. Ghali, H. El-Faramawy, M. Eissa, and A. Ahmed Copyright © 2017 S. Ghali et al. All rights reserved. Comparative Study of Strength and Corrosion Resistant Properties of Plain and Blended Cement Concrete Types Wed, 04 Oct 2017 00:00:00 +0000 The relative performances of mechanical, permeability, and corrosion resistance properties of different concrete types were compared. Concrete types were made from ordinary Portland cement (OPC), Portland pozzolana cement (PPC), and Portland slag cement (PSC). Compressive strength test, effective porosity test, coefficient of water absorption, short-term accelerated impressed voltage test, and rapid chloride permeability test (RCPT) were conducted on M30 and M40 grades of concrete designed with OPC, PPC, and PSC cements for 28- and 90-day cured concrete types. Long-term studies such as microcell and electrochemical evaluation were carried out to understand the corrosion behaviour of rebar embedded in different concrete types. Better corrosion resistant properties were observed for PSC concrete by showing a minimum current flow, lowest free chloride contents, and lesser porosity. Besides, PSC concrete has shown less coefficient of water absorption, chloride diffusion coefficient (CDC), and lower corrosion rate and thereby the time taken for initiation of crack extended. Velu Saraswathy, Subbiah Karthick, Han Seung Lee, Seung-Jun Kwon, and Hyun-Min Yang Copyright © 2017 Velu Saraswathy et al. All rights reserved. Preparation of Palladium-Impregnated Ceria by Metal Complex Decomposition for Methane Steam Reforming Catalysis Tue, 03 Oct 2017 00:00:00 +0000 Palladium-impregnated ceria materials were successfully prepared via an integrated procedure between a metal complex decomposition method and a microwave-assisted wetness impregnation. Firstly, ceria (CeO2) powders were synthesized by thermal decomposition of cerium(III) complexes prepared by using cerium(III) nitrate or cerium(III) chloride as a metal source to form a metal complex precursor with triethanolamine or benzoxazine dimer as an organic ligand. Palladium(II) nitrate was consequently introduced to the preformed ceria materials using wetness impregnation while applying microwave irradiation to assist dispersion of the dopant. The palladium-impregnated ceria materials were obtained by calcination under reduced atmosphere of 10% H2 in He stream at 700°C for 2 h. Characterization of the palladium-impregnated ceria materials reveals the influences of the metal complex precursors on the properties of the obtained materials. Interestingly, the palladium-impregnated ceria prepared from the cerium(III)-benzoxazine dimer complex revealed significantly higher BET specific surface area and higher content of the more active Pdδ+ (δ > 2) species than the materials prepared from cerium(III)-triethanolamine complexes. Consequently, it exhibited the most efficient catalytic activity in the methane steam reforming reaction. By optimization of the metal complex precursors, characteristics of the obtained palladium-impregnated ceria catalysts can be modified and hence influence the catalytic activity. Worawat Wattanathana, Suttipong Wannapaiboon, Chatchai Veranitisagul, Navadol Laosiripojana, Nattamon Koonsaeng, and Apirat Laobuthee Copyright © 2017 Worawat Wattanathana et al. All rights reserved. Research on the Strength Variation of Root-Clay Systems under Freeze-Thaw Action Tue, 03 Oct 2017 00:00:00 +0000 The aim of this paper is to study the influence of an effective root system of rhizome plants on the reinforcement of slope soil under freeze-thaw conditions. This study focused on the mechanical properties between roots and clay in the root system of four plant species from different regions of China (northeast, northern, central, and southern areas): Setaria viridis, Eleusine indica, Zoysia japonica, and Carex leucochlora. Based on the interfacial friction effects between the plant roots and the soil, pull-out tests and unconfined compressive strength tests were conducted on the reinforced soil system for varying numbers of freeze-thaw cycles. Several stages of the pull-out process of the root system in clay are explicitly proposed based on the interfacial friction test results. The results showed that the friction effect between Zoysia japonica roots and the soil was the most significant and that these roots had the best reinforcement effect. In contrast, the friction and reinforcement effects between Setaria viridis roots and the soil were the worst, and the resulting unconfined compressive strength was the smallest. However, the freeze-thaw resistance ability of the Setaria viridis and soil system was stronger than that of the Zoysia japonica system. Lin Yang, Hengxing Wang, Chunpeng Han, Hong Guo, Yafeng Gong, and Yulong He Copyright © 2017 Lin Yang et al. All rights reserved. Size Effect of Concrete Specimens on the Acoustic Emission Characteristics under Uniaxial Compression Conditions Mon, 02 Oct 2017 06:30:46 +0000 Acoustic emission (AE) experiments under uniaxial compression and cyclic loading-unloading compression conditions were performed using different sizes of cubic concrete specimens. The influences of the loading methods and the concrete sizes on the mechanical parameters and the concrete AE activities were analyzed. The loading method was found to have great impact on the deformation, failure, and energy dissipation of concrete materials. With the increase of the material size, the uniaxial compressive strength of the concrete specimens gradually decreased, while the corresponding strain of peak strength increased first and then decreased. The elasticity modulus fluctuated irregularly. Under the uniaxial compression conditions, five AE patterns corresponding to the deformation and failure of the concrete materials were observed. A significant nonlinear relationship was found between the AE and the stress level. The cumulative AE rings at the peak stress showed nonlinear growth with the increase of the concrete size. Based on an established relationship between the cumulative AE rings and the stress level, the necessary conditions for the existence of the quiet AE period were given. Under the uniaxial cyclic loading-unloading compression conditions, the Felicity ratio decreased first and then increased as the stress increased. The research results have some guiding significance to AE-based monitoring of internal stress evolution of coal, rock, and concrete materials and thereby enable assessment of their stability. Jianbo Wu, Enyuan Wang, Xuekun Ren, and Mingwei Zhang Copyright © 2017 Jianbo Wu et al. All rights reserved. Simulation of Solidified Microstructure and Experimental Comparative Study of Twin-Roll Casting Aluminum Alloys Mon, 02 Oct 2017 00:00:00 +0000 A coupled macro-micro mathematical model of twin-roll casting was established in the study. The continuous solidification process of Al-10Mg aluminum alloys in front of the nip point was numerically simulated by the cellular automaton method and the solidification microstructure, dendritic grain radius, and secondary dendrite arm spacing were obtained through simulation to predict the mechanical property of wedge strips. In order to verify the reliability of the simulation results, the metallographic examination and tensile tests were performed with the as-cast specimens. The results showed that the gain size, the distribution characteristics of various grain regions, dendrite arm spacing, and the yield strengths obtained from simulation were consistent with experimental results. Teng Ma, Junting Zhang, Xiaochao Cui, and Xiaosi Sun Copyright © 2017 Teng Ma et al. All rights reserved. A Study on the Manufacturing Properties of Crack Self-Healing Capsules Using Cement Powder for Addition to Cement Composites Sun, 01 Oct 2017 09:37:59 +0000 We fabricated crack self-healing capsules using cement powder for mixing into cement composites and evaluated the properties of the capsule manufacturing process in this study. The manufacture of the self-healing capsules is divided into core production processing of granulating cement in powder form and a coating process for creating a wall on the surfaces of the granulated cement particles. The produced capsules contain unhardened cement and can be mixed directly with the cement composite materials because they are protected from moisture by the wall material. Therefore, the untreated cement is present in the form of a capsule within the cement composite, and hydration can be induced by moisture penetrating the crack surface in the event of cracking. In the process of granulating the cement, it is important to obtain a suitable consistency through the kneading agent and to maintain the moisture barrier performance of the wall material. We can utilize the results of this study as a basis for advanced self-healing capsule technology for cement composites. Yun-Wang Choi, Sung-Rok Oh, and Byung-Keol Choi Copyright © 2017 Yun-Wang Choi et al. All rights reserved. Effect of Indium Additions on the Formation of Interfacial Intermetallic Phases and the Wettability at Sn-Zn-In/Cu Interfaces Sun, 01 Oct 2017 00:00:00 +0000 The wettability of copper substrates by Sn-Zn eutectic solder alloy doped with 0, 0.5, 1, and 1.5 at.% of indium was studied using the sessile drop method, with flux, in air, at 250°C and reflow time of 3, 8, 15, 30, and 60 min. Wetting tests were performed at 230, 250, 280, 320, and 370°C for an alloy containing 1.5 at.% of indium, in order to determine activation energy of diffusion. Solidified solder/substrate couples were studied using scanning electron microscopy (SEM), the intermetallic phases from Cu-Zn system which formed at the solder/substrate interface were identified, and their growth kinetics was investigated. The ε-CuZn4 was formed first, as a product of the reaction between liquid solder and the Cu substrate, whereas γ-Cu5Zn8 was formed as a product of the reaction between ε-CuZn4 and the Cu substrate. With increasing wetting time, the thickness of ε-CuZn4 increases, while the thickness of ε-CuZn4 does not change over time for indium-doped solders and gradually disappears over time for Sn-Zn eutectic solder. Janusz Pstruś, Tomasz Gancarz, and Przemyslaw Fima Copyright © 2017 Janusz Pstruś et al. All rights reserved. Study of the Penetration and Diffusion Characteristics of Inorganic Solidified Foam in Rock Fractures Thu, 28 Sep 2017 10:04:36 +0000 To explore the penetration and diffusion law in coal and rock fractures when inorganic solidified foam (ISF) is used to prevent coal fire, the penetration experiment was conducted; the results showed that the penetration pressure fluctuates within a certain range and decreases with the diffusion distance. In the plane, the diffusion pattern presents an ellipsoid shape, and the diffusion area becomes increasingly large over time; in the plane, the foam fluid penetration changes from dense to loose in the direction and it does not undergo downward penetration and diffuses via its own weight in the direction; in the plane, it is loose on the left and dense on the right. The viscosity of ISF was tested and then the time-varying formula was fitted. The formula of the effective diffusion radius for foam fluid diffusing in the fracture channel was determined theoretically. The permeability coefficient and other related parameters were calculated in terms of the penetration pressure and diffusion time of two monitoring points. At last, the prediction formula of effective diffusion distance of foam fluid was verified with the remaining seven monitoring points and all the relative error of monitoring is within 10%. Yi Lu, Tao Wang, and Qing Ye Copyright © 2017 Yi Lu et al. All rights reserved. Two-Dimensional Modeling of Thermomechanical Responses of Rectangular GFRP Profiles Exposed to Fire Thu, 28 Sep 2017 08:54:39 +0000 In the past three decades, one-dimensional (1D) thermal model was usually used to estimate the thermal responses of glass fiber-reinforced polymer (GFRP) materials and structures. However, the temperature gradient and mechanical degradation of whole cross sections cannot be accurately evaluated. To address this issue, a two-dimensional (2D) thermomechanical model was developed to predict the thermal and mechanical responses of rectangular GFRP tubes subjected to one-side ISO-834 fire exposure in this paper. The 2D governing heat transfer equations with thermal boundary conditions, discretized by alternating direction implicit (ADI) method, were solved by Gauss-Seidel iterative approach. Then the temperature-dependent mechanical responses were obtained by considering the elastic modulus degradation from glass transition and decomposition of resin. The temperatures and midspan deflections of available experimental results can be reasonably predicted. The overestimation of deflections could be attributed to the underestimation of bending stiffness. This model can also be extended to simulate the thermomechanical responses of beams and columns subjected to multiside fire loading, which may occur in real fire scenarios. Lingfeng Zhang, Weiqing Liu, Guoqing Sun, Lu Wang, and Lingzhi Li Copyright © 2017 Lingfeng Zhang et al. All rights reserved. Investigation of Erosion of Cement-Bentonite via Piping Thu, 28 Sep 2017 00:00:00 +0000 Cement-bentonite is one of the main materials used in the seepage barriers to protect earth dams and levees from water erosion. However, the current understanding of the erodibility of the cementitious materials and the interactions between cracked seepage barriers and the water flow is inadequate. Based on the laboratory pinhole erosion test, we first investigated the impacts of cement-bentonite treatments by using the ground granulated blast-furnace slag (GGBS) as replacement on the erosion characteristics, compared with the original mixtures; the inclusion of GGBS highlighted a potential advantage against water erosion. In addition, we proposed to calculate the erosion percentage and establish the mathematical relationships between the erosion percentage and different regimes, that is, different curing period, erosion time, and sizes of initial holes. Results showed that enough curing period was critical to avoid the increases of hydraulic conductivity in the macrofabric of the barrier; meanwhile, the materials were eroded quickly at the beginning and slowed down with the erosion time, where the enlargement of the initial creaks would be stabilised at some point in time. Moreover, the sizes of initial holes may affect the erosion situation varying from the sample curing periods. Zijun Wang, Boming Zhao, and A. C. D. Royal Copyright © 2017 Zijun Wang et al. All rights reserved. Study on the Effect of Different Fe2O3/ZrO2 Ratio on the Properties of Silicate Glass Fibers Thu, 28 Sep 2017 00:00:00 +0000 A series of silicate glass fibers with different ratios of Fe2O3/ZrO2 were prepared, and their corrosion resistance, mass loss, and strength loss were characterized. The crystallization and melting properties of the fibers were analyzed by differential scanning calorimetry (DSC), high temperature viscometer, and high temperature microscope. The results show that the deformation temperature, sphere temperature, hemisphere temperature, and crystallization temperature of the fiber initially decrease and then increase with the increase of Fe2O3/ZrO2 ratio, while the molding temperature decreases with the increase of the ratio of Fe2O3/ZrO2. When the ratio is close to 1 : 1, its alkali resistance is almost same as that of AR-glass fiber, and the drawing process performance is better. However, with the increase of the ratio, its alkali resistance continues to decline and the poor wire drawing performance is not conducive to the drawing operation. Jianxun Liu, Jianping Yang, Haibin Huo, Liang Lei, Ying Cui, and Zhishen Wu Copyright © 2017 Jianxun Liu et al. All rights reserved. Assessment of Mechanical Properties and Damage of High Performance Concrete Subjected to Magnesium Sulfate Environment Thu, 28 Sep 2017 00:00:00 +0000 Sulfate attack is one of the most important problems affecting concrete structures, especially magnesium sulfate attack. This paper presents an investigation on the mechanical properties and damage evolution of high performance concrete (HPC) with different contents of fly ash exposure to magnesium sulfate environment. The microstructure, porosity, mass loss, dimensional variation, compressive strength, and splitting tensile strength of HPC were investigated at various erosion times up to 392 days. The ultrasonic pulse velocity (UPV) propagation in HPC at different erosion time was determined by using ultrasonic testing technique. A relationship between damage and UPV of HPC was derived according to damage mechanics, and a correlation between the damage of HPC and erosion time was obtained eventually. The results indicated that the average increasing amplitude of porosity for HPCs was 34.01% before and after exposure to magnesium sulfate solution; the damage evolution of HPCs under sulfate attack could be described by an exponential fitting; HPC containing 20% fly ash had the strongest resistance to magnesium sulfate attack. Sheng Cang, Xiaoli Ge, and Yanlin Bao Copyright © 2017 Sheng Cang et al. All rights reserved. Economic and Environmental Evaluation and Optimal Ratio of Natural and Recycled Aggregate Production Thu, 28 Sep 2017 00:00:00 +0000 Steady increase in overexploitation of stone quarries, generation of construction and demolition waste, and costs of preparing extra landfill space have become environmental and waste management challenges in metropolises. In this paper, aggregate production is studied in two scenarios: scenario 1 representing the production of natural aggregates (NA) and scenario 2 representing the production of recycled aggregates (RA). This study consists of two parts. In the first part, the objective is the environmental assessment (energy consumption and CO2 emission) and economic (cost) evaluation of these two scenarios, which is pursued by life-cycle assessment (LCA) method. In the second part, the results of the first part are used to estimate the optimal combination of production of NA and RA and thereby find an optimal solution (scenario) for a more eco-friendly aggregate production. The defined formulas and relationship are used to develop a model. The results of model validation show that the optimal ratio, in optimal scenario, is 50%. The results show that, compared to scenario 1, optimal scenario improves the energy consumption, CO2 emissions, and production cost by, respectively, 30%, 36%, and 31%, which demonstrate the effectiveness of this optimization. Milad Ghanbari, Armin Monir Abbasi, and Mehdi Ravanshadnia Copyright © 2017 Milad Ghanbari et al. All rights reserved. Optimal Heat Transfer Coefficient Distributions during the Controlled Cooling Process of an H-Shape Steel Beam Wed, 27 Sep 2017 00:00:00 +0000 Three-dimensional thermal-mechanical models for the prediction of heat transfer coefficient distributions with different size beams are investigated. H300 × 300, H250 × 250, and H200 × 200 H-shape steel beams are investigated in a controlled cooling process to obtain the design requirements for maximum uniform temperature distributions and minimal residual stress after controlled cooling. An algorithm developed with the conjugated-gradient method is used to optimize the heat transfer coefficient distribution. In a comparison with the three group results, the numerical results indicate that, with the same model and under the same initial temperature (°C) and final temperature (°C), the heat transfer coefficients obtained with the conjugated-gradient method can produce more uniform temperature distribution and smaller residual web stress, with objective functions of the final average temperature and maximum temperature difference to minimum . The maximum temperature difference is decreased by 57°C, 74°C, and 75°C for Case  1, Case  2, and Case  3, respectively, the surface maximum temperature difference is decreased by 60~80°C for three cases, and the residual stress at the web can be reduced by 20~40 MPa for three cases. Yu-Feng Gan and Jiin-Yuh Jang Copyright © 2017 Yu-Feng Gan and Jiin-Yuh Jang. All rights reserved.