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931.
932.
This paper evaluates the effects of microbiologically influenced corrosion (MIC) on fatigue-crack growth of candidate materials useful in expanding bio-ethanol usage, including a storage-tank steel (ASTM A36) and two pipeline steels (API 5L X52 and X70). The microbiological species sampled and cultivated from an ethanol fuel production stream are responsible for both acetic acid and hydrogen sulfide production that lead to significant increases in fatigue-crack growth rate across a wide range of stress-intensity-factor amplitudes (ΔK). The mechanism for increased fatigue damage is hydrogen uptake through adsorption into the steel, which embrittles material ahead of the growing fatigue crack. 相似文献
933.
《Intermetallics》2014
The electronic structure and chemical bonding properties of four families of Ce2T2X (T = nd element; X = Mg, Cd, Pb or Sn) intermetallics crystallizing in an ordered U3Si2 type structure are shown from density functional theory (DFT) calculations to present electronic and magnetic structure properties arising from their peculiar valence electron count (VEC). Trends of the magnetism are discussed in terms of the characteristics of the Ce(4f) states as well as the energetic position of the transition metal element d states. 相似文献
934.
《Intermetallics》2014
A series of Ni50−xCoxMn32Al18 (x = 3, 4, 5, 6, 7, and 8) alloys were prepared by the arc melting method. The martensitic transformation (MT) shifts to a lower temperature with increasing Co concentration and can be tuned to occur from a ferromagnetic austenite to a weak-magnetic martensite in the range of 6 ≤ x ≤ 8. The field-induced metamagnetic behavior was realized in Ni42Co8Mn32Al18 sample in which a large magnetic entropy change of 7.7 J/kg K and an effective refrigerant capacity value of 112 J/kg were obtained under the field of 60 kOe. The large magnetocaloric effect and adjustable MT temperature suggest that Ni–Co–Mn–Al alloys should have promising potential as magnetic refrigerants. 相似文献
935.
Environmental barrier coatings (EBCs) are proposed as an option to reduce the high temperature water vapour corrosion in gas turbines ceramic components made of Si3N4 or SiC/SiCf, which are projected to achieve further energy efficient gas turbines. These coating are commonly designed as multilayer systems firmly attached to the ceramic substrate with the aim of retarding or avoiding its degradation after exposure to environmental conditions close to those in gas turbines. Therefore, to fulfil this function crack formation/propagation in the coatings must be controlled. In present work, three types of environmental barrier coatings fabricated by air plasma spray and containing a Si layer attached to SiC substrate plus 2 to 5 layers of different mullite/Y2O3 stabilized–ZrO2 mixtures are examined. To determine the level of residual stresses in the as-sprayed coating/substrate systems a three dimensional finite element model is developed and also tested for same coatings but aged under, high temperature and rich water vapour atmosphere. The model calculates the zones of maximum tensile stresses in the coatings which agree with experimental observation identifying the type, number and location of cracks. This model could be extended to similar EBC systems, and more importantly, could be use as a powerful designing tool for these complex structures. 相似文献
936.
In recent years, several equations have been proposed to calculate deflections and stresses in laminated-glass beams and plates under static loading using the concept of effective thickness, which consists of calculating the thickness of a monolithic element with equivalent bending properties to a laminated element. Recently, an effective thickness for the dynamic behavior of laminated-glass beams has been proposed to enable the modal parameters (natural frequencies, loss factors and mode shapes) to be determined using an equivalent monolithic model. In the present paper, the technique has been extended to the two-dimensional case of rectangular laminated-glass plates and the steps needed to estimate the modal parameters of laminated-glass elements using this methodology are presented. The dynamic effective thickness concept has been validated by experimental tests made on a laminated-glass beam and a laminated-glass plate. The results show that good accuracy is achieved in the natural frequencies and mode shapes but high scatter is encountered in the loss factors. 相似文献
937.
《Intermetallics》2014
Based on the density functional theory (DFT), the plane-wave pseudopotential method was used to calculate structural stabilities, electronic structures, and ferromagnetism of Fe3Si, Fe11NiSi4, Fe11CoSi4 and Fe11CrSi4 intermetallic compound. This study showed that the Fe11NiSi4 and Fe11CrSi4 phase are more stable than Fe3Si phase, especially Fe11NiSi4, but decreased with Fe11CoSi4 phase. Calculating the density of states and the Mulliken electronic populations showed that Fe11NiSi4 had the highest structural stability because of its Fermi level, which was close to the bottom of the pseudo-gap. Fe11NiSi4 also had the largest Mulliken population, which increased the metallic bonding of the alloying system. The total magnetic moments of Fe11NiSi4, Fe11CoSi4 and Fe11CrSi4 were 20.04μB, 19.98μB, and 18.81μB, respectively. These magnetic moments mainly originated from the 3d spin polarization of Fe and those of additional atoms. 相似文献
938.
Graphene nanopowder (GNP) and multi-walled carbon nanotube (MWCNT)-filled epoxy thin-film composites were fabricated using ultrasonication and the spin coating technique. The effect of sonication time (10, 20 and 30 min) and GNP loading (0.05–1 vol%) on the tensile and electrical properties of GNP/epoxy thin-film composites was investigated. The addition of GNP decreased the material’s tensile strength and modulus. However, among the tested samples, the GNP/epoxy composites produced using 20 min of sonication time had a slightly higher tensile strength and modulus, with a lower electrical percolation threshold volume fraction. The effect of sonication time was supported by morphological analysis, which showed an improvement in GNP dispersion with increased sonication time. However, GNP deformation was observed after a long sonication time. The GNP/epoxy composites at different filler loadings showed higher electrical properties but slightly lower tensile properties compared with the MWCNT/epoxy composites fabricated using 20 min of sonication time. 相似文献
939.
For investigating the effect of fiber content on the material and interfacial bond properties of ultra high performance fiber reinforced concrete (UHPFRC), four different volume ratios of micro steel fibers (Vf = 1%, 2%, 3%, and 4%) were used within an identical mortar matrix. Test results showed that 3% steel fiber by volume yielded the best performance in terms of compressive strength, elastic modulus, shrinkage behavior, and interfacial bond strength. These parameters improved as the fiber content was increased up to 3 vol.%. Flexural behaviors such as flexural strength, deflection, and crack mouth opening displacement at peak load had pseudo-linear relationships with the fiber content. Through inverse analysis, it was shown that fracture parameters including cohesive stress and fracture energy are significantly influenced by the fiber content: higher cohesive stress and fracture energy were achieved with higher fiber content. The analytical models for the ascending branch of bond stress-slip response suggested in the literature were considered for UHPFRC, and appropriate parameters were derived from the present test data. 相似文献
940.
Laminates, composed of different papers and polypropylene (PP), were fabricated by a manual stacking and hot pressing. The laminates were characterized by mechanical testing and the results were compared to glass fiber reinforced PP. Furthermore, a detailed evaluation of the interfacial properties and the paper structures was carried out by means of data modeling via rule of mixtures (ROM), as well as electron microscope (SEM) analysis. For investigating the influence of the laminate’s composition on the water adsorption behavior, water diffusion coefficients were determined. As a result, laminates with a tensile modulus up to 6 GPa and a tensile strength of 80 MPa were obtained. The property changes of the papers upon processing were successfully modeled, revealing a significant increase of the paper’s mechanical properties after fiber embedding. In general, the obtained results indicate a high potential of paper as a suitable reinforcement material for low to middle strained applications. 相似文献