Applied Mechanics and Materials Vols. 182-183

Abstract: Electrical conductive carbon-modified cement-based composites are important multi-functional structural material. Double compounding carbon fiber and carbon black into cement-based material can improve the electrical conductive property of cement-based composites. In this paper, the influences of carbon fiber ratio and total volume fraction of carbon components on the resistivity of cement-based composites are investigated. The results show that both carbon fiber ratio and total volume fraction have great effect on the conductive behavior of carbon-modified cement-based material. At a fixed carbon fiber ratio, with the increase of total volume fraction, the resistivity of cement-based composites drops down dramatically and shows obvious percolation phenomenon. The reason is that with more and more conductive particles and fibers added into the cement material, the conductive components connect with each other gradually and at certain point reach the percolation threshold. At a fixed total volume fraction, the resistivity drops down with the increase of carbon fiber ratio. This is because that the carbon fiber has larger aspect ratio than carbon black, so carbon fiber could get lower resistivity with the same dosage according to the percolation theory. Finally, the results show that with 0.5 carbon fiber ratio and 2% total volume fraction the carbon-modified cement-based composites have relatively low resistivity, high workability and high compressive strength.

Abstract: The uniaxial tensile properties of three-dimensional angle-interlock woven composites (3DAWCs) under quasi-static loading were investigated in this paper. The samples were manufactured into dog-bone shape and tested on Material Test System 810.23. The strain-stress curves in warp direction indicating the Young’s moduli, maximum stress and maximum strain are achieved from the uniaxial tensile test. The effects of microstructure and damage morphology of 3DAWC under quasi-static tension are discussed. Furthermore, we will focus on the energy absorption mechanism from the view of tensile failure mode. The material parameters of 3DAWC in warp direction can be evaluated for developing quantitative approach to design polymer matrix composite structures.

Abstract: In this study, the Kevlar fabric composites were prepared by shear thickening compound to get the high impact resistance. The characterizations of the produced polyborondimethylsioxane (PBDMS) have been obtained by Differential Scanning Caborimetry(DSC), Thermal Gravimetric Analysis(TGA), etc. The controlled stress rheometer was used to characterize the rheological property. Meanwhile the ballistic and stab tests of this Kevlar composite were investigated and found to exhibit significant improvement. The mechanism of energy absorbing was tentatively discussed. It showed that these novel energy absorbing materials could be potentially used to fabricate flexible body armors and high-grade sports accessories with good perspective.

Abstract: The present work reported the preparation of V(C,N)-reinforced iron matrix composite via in situ synthesis. The phases and morphologies of the sintered composite were investigated using X-ray diffraction (XRD) and scanning electron microscopy(SEM). Dry sliding wear test had been carried out to study the wear behavior of V(C,N)-reinforced iron matrix composite. The results show that a uniform distribution of the V(C,N) reinforcing phase throughout the iron matrix is successfully obtained. Compared with hardened 45 steel, the wear resistance of the V(C,N)-reinforced composite is better

Abstract: In this paper, Al-12.6%Si/Al₆₃Cu₂₅Fe₁₂ composites were fabricated by method of casting. The microstructure and chemical composition of Al₆₃Cu₂₅Fe₁₂ quasicrystal alloy and Al-12.6%Si alloy reinforced by the quasicrystal were studied, and the mechanical properties of Al-12.6%Si composite were also measured. The results show that almost single quasicrystalline phases exist in the samples which are cast with the 1300°C melt. Quickly enough cooling rate and appropriate melt temperature are necessary for the formation of the quasicrystalline phase. In addition, Al-12.6%Si composite has optimal mechanical properties when the amount of Al₆₃Cu₂₅Fe₁₂ quasicrystal is 3 wt%.

Abstract: This paper studies iron-rich phase transformation law and mechanism of Al-20Si-10Fe alloy under the effect of plate magnetic field. with optical microscopy(OM)，scanning electron microscopy(SEM),energy dispersive spectrum(EDS)and transmission electron microscopy(TEM). The results show that plate magnetic field is directly involved in the phase transformation of iron-rich phase, making iron-rich phase change from lath-shaped β-Al₅FeSi to herringbone-shapedα-Al₈SiFe₂. The enforcement of plate magnetic field during the phase-transforming process of β-Al₅FeSi→α-Al₈Si Fe₂ makes block α-Al_1.3Si_7.8Fe_2.1 phase yield out. And precipitation of α-Al_1.3Si_7.8Fe_2.1 phase is affected by the transforming process ofβ-Al₅SiFe phase→α-Al₈Si Fe₂phase.

Abstract: FH36-TM high strong steel is used in 350t deck crane base of ship hull in our company. This material is seldom used in shipping industry, owing to high demanding of degree and Thickness welding technology. Minimum degree of welding materials is 5Y degree in using welding wire, in accordance with demanding of degree and thick steel of GL specifications of quality. Preheat temperature is established on base of the influence of temperature of the surroundings, original material degree, thickness, carbon equivalent of original material and content of hydrogen in weld metals. Welding Procedure Parameters of FH36-TM High Strong and 60mm Steel were studied by adopting single wire SAW. The results indicate that jointing properties are equal to original materials. Jointing properties and results of hardness conform to requirements of GL specifications. Drawbacks were not founded in checking jointing, and owners of ship accepted products.

Abstract: TiC/Ti₅Si₃ composite materials on Ti-5Al-2.5Sn were in-situ synthesized by argon tungsten-arc welding (GTAW) deposition from powder compacts with the molar ratio of Ti:Si:C=3:1:2. X-ray diffraction (XRD) techniques and scanning electron microscope (SEM) were employed to characterize the microstructure of the composites. The effects of depositing times on the surface microstructure of the tracks deposited were studied. From the products synthesized in this work, the content of TiC/Ti₅Si₃ in-situ composites on the surface of the tracks differed from each other by depositing one, two, three, and four times, respectively. The minimum impurities were obtained and the distribution of TiC/Ti₅Si₃. In-situ composites were most homogeneous in the track surface by depositing three times.

Abstract: Methanobactin (mb) is a small, copper binding bioactive peptides produced by methanotrophs. The transition between two forms of methane monooxygenase (MMO) expressed by methanotrophs depends on the amount of copper available in the surrounding. In this paper, the bioavailability of copper(Ⅱ) in the presence of different chelating agents to a representative methanotroph, Methylosinus trichosporium 3011 is studied systematically according to the naphthalene oxidation assay. The result shows that purple naphthol diazo complex may be measured at A530, and along with the increase of the concentration of the copper(Ⅱ), eight kinds of chelating agents have effect on the activity of sMMO. The copper bioavailability has been assessed after the changes in sMMO activity is monitored, it means that copper(Ⅱ) can repress the expression of sMMO as well as reduce its activity. The affinity of mb excreted during growth was also measured and the chelate constants of the chelating agents to copper(Ⅱ) are compared. Based on these studies, strongly binding chelating agents (Log K > 16) added into the medium at a concentration of 20uM were able to reduce copper bioavailability.

Abstract: In this paper, the high temperature tensile properties of the LAZ532-2RE alloy prepared by hot extruded processing after vacuum casting was investaged. The tensile properties of the extruded LAZ532-2RE alloy specimens were tested at different temperature with different strain rate. The microstructures near the fractured surfaces were observed using microscope in order to investigate the dominant deformation mechanism. The activation energy was calculated to explain the high temperature deformation mechanism. The result indicated that the strength of LAZ532-2RE alloy was high at the temperature range from 398K to 423K. Meanwhile, the fracture elongation of the alloy reaches 121% at 523K under strain rate 1×10^-3s^-1.