Functional Materials and Metallurgy

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作者: Andrey Benin, Sergey Semenov, Ekaterina Bogdanova
摘要: The current experimental research is devoted to comparison of bond glass fiber reinforced plastic with concrete before and after long-term (quarter year, half year and one year) exposure in the concrete on the air and in the water. The comparative analysis of experimental results was performed.
作者: Tian Yu Xi, Jian Hua Ding, Hong Jin
摘要: Aiming at offering reference for architects, urban planners and further research work in the sustainable building field, this work took the city of Guangzhou, China, as an example, by carrying out a 2-day constant field experiment in the campus of South China University of Technology, study on the influence of materials on the outdoor ground surface temperature, including concrete, pavement brick and grass. The result showed that, the grass surface temperature has the lowest temperature in both of daytime and night time, and it has no time delay compared with concrete and pavement brick ground, which should be due to the specific heat capacity of human built materials. The pavement brick has the highest surface temperature in daytime, but at late night time, it becomes lower than that of concrete ground, and this should be because that the specific heat capacity of pavement brick is lower compared with that of concrete. The surface temperature of concrete ground at night time is influenced by exposed time in daytime due to the influence of specific heat capacity, and in this experiment, the shaded concrete is lower than that of part-time exposed concrete ground at night time, and the part-time exposed concrete is lower than the concrete exposed all day, indicating that the ground material should be carefully designed in outdoor, taking both of thermal environment in daytime and night time into consideration.
作者: Fa Sheng Zhang, Yun Xing Shi, Jing Bin Shi, Kun Ni, Yan Gang Zhang, Xiao Jie Li
摘要: In order to study the flexural behavior of steel fiber reinforced concrete (SFRC) shield tunnel segment, two full scale shield tunnel segments and twelve reduced scale shield tunnel segments were made and tested. Based on the experiment study, the effectiveness of reduced scale segment was analyzed. Meanwhile, based on the fail mode, load-deflection curves and crack width, the part substitution of steel reinforcement by steel fibers was studied. Test results showed that the reduced scale model can reflect the flexural behavior of full scales tunnel segment and 45kg/m3 steel fibers of 3D type can replace 17% longitudinal reinforcement and 70% stirrups.
作者: Thomas Vincent, Togay Ozbakkaloglu
摘要: This paper reports the findings from an analytical study into the influence of fiber reinforced polymer (FRP)-to-concrete interface gap and prestressed FRP tubes on strain reduction factor (kε) for concrete-filled FRP tube (CFFT) columns. A database that consists of a total of 45 aramid FRP- (AFRP) confined normal-and high-strength concrete (NSC and HSC) specimens with circular cross-sections is presented. All specimens were cylinders with a 152 mm diameter and 305 mm height, and their unconfined concrete strengths ranged from approximately 45 to 110 MPa. Analyses of the experimental databases that consisted of 22 specimens manufactured with FRP-to-concrete interface gap and a further 23 specimens prepared with lateral prestress is presented and discussed. Based on close examination of the hoop strain development on the FRP confining shell, expressions to predict strain reduction factors (kε) are proposed. The comparison of the proposed model predictions with the experimental test results of specimens prepared with an interface gap or prestressed FRP tubes shows good agreement.
作者: Refilwe Lediga, Deon Kruger
摘要: This paper presents an overview of an investigation into the application of additive manufacturing commonly known as 3D printing specifically within the construction industry. 3D concrete printing is a new and innovative way of construction and can be used for the manufacturing of micro to macro high precision construction components. If correctly designed and used, this method has various advantages over traditional construction methods as it creates opportunities to reduce time and cost. A crucial component for success is an optimized concrete or mortar mix to ensure proper feed, placement and hardening during the 3D printing process. A 3D concrete printer uses a chemically altered concrete or mortar mix, which is pumped through a concrete extruder/nozzle that is carefully controlled in three dimensions. This extruder is controlled by a computerised gantry system, and prints components and structures layer by layer. The key components in such a system are therefore a concrete pump, an extruder, an optimized printable concrete mix and a computerised gantry system. The paper will present an investigation into the criteria for an optimum concrete mix design to be used in a 3D concrete printing machine.
作者: Jian Guo, Yong He, Qiang Qiang Xiao, Zheng Xiang Huang, Ya Ping Tan
摘要: In order to study influence of yield strength of liner on aperture diameter when liner material has high strength, the initial aperture and final aperture diameter were analyzed by considering yield strength of liner material. The relationship of aperture diameter with liner strength changing was obtained. The experiments using Ti alloy liner with different yield strength penetrated into concrete were performed. The results shown that, the average aperture diameter of Ti alloy liner which the yield strength is 785MPa is about 1.16 times bigger than that of copper liner which the yield strength is 870MPa. It has good agreement with theoretic analysis. With liner strength increasing, the aperture diameter decreased, and this increasing is more significant with jet velocity decreasing. With respecting to the high-density copper liner, the influence of yield strength on aperture diameter is more sensitive for low-density Ti alloy liner.
作者: Zhi Yuan Yu, Zhu Feng Yue, Wei Cao, Xin Mei Wang
摘要: Nickel-based single crystal superalloys have been widely used in modern aircraft, which is related to its high temperature mechanical strength and creep properties. And the initial cubic γ′ precipitates start to coarsen directionally during high temperature creep, which results in the degradation of the mechanical properties, especially the creep properties. Therefore, it is essential to figure out the mechanism of directional coarsening during the period of high temperature creep. In this article, a broad review of rafting mechanism of nickel-based single crystal superalloys is provided. The major work of this critical review is to introduce several experiments and numerical simulations which are used to analyze the evolution of rafting. For three different numerical simulations, their performance, advantage and disadvantage are discussed in detail. Through methods above, the effect on creep properties is summarized.
作者: Waraporn Piyawit, Panya Buahombura
摘要: CuAgZr alloy is a minor variation of CuAg alloy that is remarkably known for good combination of strength and electrical conductivity. Strengthening and conductivity enhancing of CuAgZr alloy is essentially proficient by the precipitation of Ag precipitates. The behavior of Ag precipitates at high temperature was investigated using in-situ transmission electron microscopy. These nanoscale Ag precipitates are formed in CuAgZr alloy during heating process with the average size of 5 nm. Growth of precipitates at higher temperature can be explained by the consumption of solute diffusing from smaller precipitates. Dislocation looping at high temperature would be the effects of a large lattice strain along matrix/precipitate interface that would retard the dislocation movement.
作者: Yong Ping Lou, Ming Chen, Jun Feng Li, Xiao Dong Hu
摘要: A real-time calculation model discretized by the cellular automata (CA) method was developed for the numerical simulation of AZ31 magnesium alloy microstructure evolution during recrystallization (RX). The RX processes under different strains were simulated, also, variations in morphologies of recrystallization grains are discussed. The results of numerical simulation were compared with those of experiment analysis, and the microstructure obtained by CA was found to well agree with the actual pattern obtained by EBSD (Electron Backscattered Diffraction) analysis. The numerical simulation technique provides a flexible way of predicting the recrystallization of deformation microstructure evolution.