Key Engineering Materials Vol. 872

Abstract: This study is an experimental study aims to examine the effect of utilization of straight, and low cost steel fibers on the impact resistance of concrete. The impact resistance of steel fiber reinforced concrete (SFRC) was assessed using drop weight test as per ACI committee 544. The steel fibers were randomly dispersed in concrete during mixing. Five mixes made with steel fibers dosages of 0% (control mix), 0.5%, 1%, 1.25% and 1.5% by volume of concrete were examined in the study. The results show that mixes containing steel fibers show better impact resistance than plain concrete (control Mix). The results also indicate that increasing the dosage of fiber increases the impact resistance of concrete but up to a certain content of fibers. The maximum increase was recorded at steel fiber dosage of 1.25% by volume of concrete. Also the patterns of failure of the concrete specimens show that fibers are very effective in increasing the concrete toughness which enhance the ductility of concrete and delays the crack initiation.

Abstract: Aspects of the development of local corrosion on the metal surface under the influence of aggressive media containing chloride ions are presented. The main mechanisms leading to the formation and development of local damage of the surface of metals are described. The process of electrochemical corrosion of steel under the influence of chloride-containing medium is experimentally investigated. By constructing corrosion diagrams, the main indicators of steel corrosion in a 10% sodium chloride solution were determined, which allows one to judge the rate of development of corrosion processes with local damage to the protective coating and the degree of steel resistance depending on the aggressiveness of the medium. It is shown that protective coatings, such as modified phosphate and oxide-phosphate films, prevent the penetration of an aggressive medium to the surface of the protected metal and, accordingly, the anodic dissolution of the metal.

Abstract: In this article, analysis of heat transfer in a stockpile of reactive materials modelled in a rectangular slab is carried out. A two-step exothermic chemical reaction is assumed and the heat loss to the surrounding environment is by radiation. The ordinary differential equation (ODE) governing the problem is tackled numerically by Runge-Kutta Fehlberg (RKF45) method coupled with Shooting technique. The heat transfer analysis is simplified by investigation some kinetic parameters’ effects on the temperature of the combusting system. It was found out that some kinetic parameters raise the levels of the temperature by encouraging the exothermic chemical reaction, whereas some, reduce the levels of the temperature to slow down the heat transfer rate. The results are depicted graphically and discussed accordingly.

Abstract: Creep may affect structural behavior by violating service limit states, redistributing stress or losing prestress forces. For that, knowing the significance of factors that influence creep is a must to accurately predict it. This paper uses the Northwestern university (NU) database to investigate the factors that most affect long-term creep of concrete. Factorial ANOVA was applied to identify the significance of factors affecting creep of concrete at 3000 days using R software. The factorial ANOVA results showed that the sustained load and the relative humidity have the major effect on the value of concrete creep at 3000 days.

Abstract: Vanadium oxide thin films were deposited on glass substrates by O₂ reactive-RF magnetron sputtering from a vanadium (V) target without substrate-heating. The percentages of O₂ gas were 10%, 7.5%, 6.0%, 5.0% and 2.5%. The total gas flow rate (O₂/Ar) was kept at 25 sccm. As-deposited films were experienced post-annealing process at different temperatures and times. The crystallinity and chemical bonding states of films were examined by X-ray diffraction and Raman spectroscopy. The condition in annealing to active crystallinity depended on an earlier composition of the films. As O₂-gas percentages were 10% and 7.5%, after annealing, the as-deposited V_xO_y films were transformed into crystalline V₂O₅ films. With decreasing in O₂ percentage to 5.0% and 2.5%, the films were transformed into V₂O₃ and VO films, respectively. The films deposited with 6.0% O₂ were crystallized to VO₂ with phase B after annealing with 500 °C 15 h. By applying a longer time to 30 h at the high temperature 500 °C in annealing, VO₂ films revealed only phase M formation.

Abstract: Protein is a substantial nutrition that essentially required by human. Spirulina platensis (Spp), well known as protein source could be a significant source to be used for many industrial applications. This study was investigated the effectiveness of ultrasound assisted extraction (UAE) method for protein extraction from Spp at various composition of solvent mixture and extraction time. Ethanol and mixture of methanol-ethanol were used as solvent. Extraction was conducted by varying ratios of solvent to biomass at 10:1, 12.5:1, and 15:1 (v/w), and extraction time (20, 35, and 50 min). Optimum protein recovery from dry Spp was 42.55 ± 0.43% obtained by using 20 ml of the mixture of methanol and ethanol at 50 min of extraction time. This study also conducted that mixture of methanol and ethanol was a better solvent on improving the ultrasound assisted extraction, as indicated by high protein recovery with less amount of solvent volume used.

Abstract: This study focuses on the multi-objective optimization of the welding joint of AISI 1045 steel shafts with AISI 1070 filler wire 1.8 mm in diameter by electric resistance welding method. During the welding process, welding parameters input are important because it determines the quality of the welding joint. Therefore, in this study, Taguchi method was used in combination with grey relational analysis to select the welding parameters suitable for this welding process. The experiments were performed according to the orthogonal array L9 designed by the Taguchi method. The input welding mode parameters used in this study include welding current (I_h), force (F), welding speed (V_h). The output characteristics for the selected weld quality target are minimum tensile strength and micro hardness. Grey analyzes were conducted to optimize for the input parameters, the analysis results show that the set of input parameters suitable for the output quality are I_h = 7.5 KA; F = 1.7 KN; V_h = 1.5 cm/s. This is followed by the process of assessing the significance of the factors to all qualities of the welded joint using the ANOVA analysis process.

Abstract: The development of green composites to obtain scientific, technological and industrial application benefits, and evaluate different mechanical properties of those materials; as well as the great growth and the global market demand being considered as lightly and low manufacture cost materials, that has mechanical and physical properties equal or higher that will replace the materials that are traditionally seen in industry. Applying an analysis based in the experiments design (DOE) plus experimental essays, a mechanical characterization of composite material latex reinforced with short cabuya fiber was performed with random orientation and volumetric fractions of 20% latex - 80% cabuya fiber, 30% latex-70% cabuya fiber, 45% latex – 55% cabuya fiber; for the different combinations. Of the essays that were performed it was determined the test tubes that show better results in its mechanical properties through the UNE Norm (Tensil UNE - ISO 37, Compression UNE - ISO 7743, Strength UNE - ISO 48). With the analysis developed by the statistical methodology based on the complete general factorial design and the desirability function it was able to determine the best mechanical characteristics of the composite material that will be used, was the composite formed by fiber with 1 centimeter of length and a volumetric fraction of 20% Latex – 80% Cabuya.

Abstract: The conditions for the synthesis of aluminum tungstate Al₂(WO₄)₃ and aluminum niobate AlNbO₄ were clarified using hydrothermal treatment and post-heating. Single-phase Al₂(WO₄)₃ can be synthesized through the hydrothermal treatment of the starting materials at a mixing ratio of Al:W = 5:5 at 250 °C for 5 h and post-heating at 840 °C for 6 h. The AlNbO₄ was synthesized using the same method, under a hydrothermal treatment of Al:Nb = 2:8 and post-heating. As a result of investigating the products under various mixing conditions based on the synthesis of pure Al₂(WO₄)₃ and AlNbO₄, Nb could not be doped into Al₂(WO₄)₃, but W-doped AlNbO₄ was synthesized. The electric conductivity was measured for several samples of sintered W-doped AlNbO₄, and the results showed that the electrical conductivity was improved within a higher temperature region by doping with W.