This paper studies the optimization problem of composition distribution of functionally graded material (FGM) coating subjected to steady heat flux loading. The investigation object of the paper is an infinite plate s...
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ISBN:
(纸本)0878499709
This paper studies the optimization problem of composition distribution of functionally graded material (FGM) coating subjected to steady heat flux loading. The investigation object of the paper is an infinite plate substrate with FGM coating in the surface. The materials are heated at the ceramic surface (upside) with a steady high-intensity heat flux input, and cooled at the metal surface (underside) with flowing liquid nitrogen. The thermal stress distribution and the temperature distribution are obtained by formulation. For optimization, the design variables are the thickness of each interlayer and the volume fraction distribution of the coating. The objective function is the danger coefficient and the restricted condition is the total thickness of FGM plate and heat insulation coefficient. In the paper, three different optimization schemes are considered and compared. The μGA and related parameters are discussed in detail. Optimizing the thermal stress distribution and minimizing the danger coefficient are carried out by μGA. The optimization results of composition distribution are gained, and the results show the optimum composition distribution can distinctly reduce the danger coefficient.
A new approach to produce superfine WC-Co powder by direct reduction and carbonization is proposed. Water-soluble salts containing W and Co were used as raw materials. Tungsten and cobalt oxide powder （CoWO4/WO3） wa...
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A new approach to produce superfine WC-Co powder by direct reduction and carbonization is proposed. Water-soluble salts containing W and Co were used as raw materials. Tungsten and cobalt oxide powder （CoWO4/WO3） was first formed by a spray-pyrolysis technique, which was then mixed with carbon black and converted to WC-Co composite powder at 950℃ for 4 h in N2 atmosphere. The resulting powder has a particle size of 100-300 nm.
Ti/Al 2O 3 composite with improved mechanical properties was synthesized by th e spark plasma sintering. The effect of Nb on the microstructure of the composit e was analyzed by TEM, SEM and so on. The experimental ...
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Ti/Al 2O 3 composite with improved mechanical properties was synthesized by th e spark plasma sintering. The effect of Nb on the microstructure of the composit e was analyzed by TEM, SEM and so on. The experimental results indicate that the bending strength, fracture toughness, micro-hardness and relative density of t he composite are 897.29MPa, 17.38MPa·m 1/2, 17.13GPa and 99.24% respec tively when adding 1.5vol%Nb. The bending strength is improved by reason of form ing dislocation ring and transfering fracture mode from intergranular to mixture fracture of intergranular and transgranular. The crack propagating is mainly th e deflection bridging. It indicates a reduction of crack driving force and an in crease in crack growth resistance,which results in toughness enhanced.
The need for WC-Co with improved properties, particularly increased hardness and strength combined with increased ductility and toughness, has focused attention on the development of grades with finer and finer-graine...
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The need for WC-Co with improved properties, particularly increased hardness and strength combined with increased ductility and toughness, has focused attention on the development of grades with finer and finer-grained powders and cemented carbides. The aim of this study is to determine the sintering temperature of nanocomposite WC-6Co (wt.%) sample by using an optical microscope under high temperature and a DSC / TG apparatus. The WC-Co sample was prepared from nanocomposite powder by hot-press-sintering at the determined sintering temperature. The phase structure of the powder and sintered samples was investigated. The SEM imaging was performed on fracture surfaces of sintered samples. The density and the HRA of sintered samples were also measured.
The present paper investigates the creep phenomenon of the functionally graded materials under high temperature environment by the computational micromechanical method (CMM). Based on the real microstructure of the fu...
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ISBN:
(纸本)0878499709
The present paper investigates the creep phenomenon of the functionally graded materials under high temperature environment by the computational micromechanical method (CMM). Based on the real microstructure of the functionally graded interlayer with different component volume fractions, the emulation experiment is implemented for the creep test numerically and the creep parameters are obtained. A further series of simulation works are carried out to investigate the creep phenomenon of FGM interlayers in more detail. Numerical results show that the creep phenomenon is obvious not only for the metal-rich interlayers but also for the ceramic-rich interlayers. The creep property of ceramic/metal interlayer depends on the material's properties of the ceramic obviously. It is remarkable that the creep strain rate of the ceramic/metal interlayer is larger than the corresponding one of pure metal under the same load when the modulus of the ceramic component is lower than the one of the metal component.
The reflected coefficient of functionally graded layer to waves is very important as the design of impact-resistant FGMs. In the paper, the Optimization problem of propagation characteristic of elastic wave in FGM has...
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ISBN:
(纸本)0878499709
The reflected coefficient of functionally graded layer to waves is very important as the design of impact-resistant FGMs. In the paper, the Optimization problem of propagation characteristic of elastic wave in FGM has been investigated. The relation between the top layer's stress and displacement and the bottom layer's is deduced from elastic propagation equation as the incident wave is a plane and harmonic elastic stress wave, then the reflected coefficient of gradient layer is obtained, and the reflected coefficient is selected as object function of optimization. The thickness of each layer is selected as optimization design parameter. The conjugate gradient method is used to get the optimal results about gradient layers' thickness.
In the paper, firstly self-consistent model (SCM) is used for establishing the predicted formula which can predict the effective permittivity of the composite materials with core-shell type inclusions. Then the factor...
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ISBN:
(纸本)0878499709
In the paper, firstly self-consistent model (SCM) is used for establishing the predicted formula which can predict the effective permittivity of the composite materials with core-shell type inclusions. Then the factors on the effective permittivity of this kind of composite are investigated on the base of this predicted formula. The researching results indicate the effective permittivity of composite depends on not only the volume fraction of inclusions, but also the permittivity of matrix and inclusions (core and shell). According to our works, the optimal design of composite with core-shell type inclusion must be done if we want to make this composite get better effect of absorbing wave.
In the present study, Fe-Si sheets were formed by powder rolling of Fe-6.5wt%Si mixture powders, then were sintered in flowing Ar+5vol%H2 atmosphere. The changes in microstructure and density during the formation proc...
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In the present study, Fe-Si sheets were formed by powder rolling of Fe-6.5wt%Si mixture powders, then were sintered in flowing Ar+5vol%H2 atmosphere. The changes in microstructure and density during the formation process were mainly discussed. The results show that Fe-Si mixture powders can be rolled into comparatively compact sheets. During subsequent sintering and re-rolling, the density of the sheet gradually increased and Si diffused into Fe lattice step by step with the increasing of temperature.
In the paper, propagation of two-dimensional viscous-plastic waves in graded layer media is investigated by numerical method. Firstly, an infinite model is used to analysis wave's propagation in FGMs, this model h...
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ISBN:
(纸本)0878499709
In the paper, propagation of two-dimensional viscous-plastic waves in graded layer media is investigated by numerical method. Firstly, an infinite model is used to analysis wave's propagation in FGMs, this model has a finite gradient layer and non-reflecting boundary condition is used to simplify the model to be finite. Then the characteristic of viscous-plastic wave's propagation in graded media is investigated on the base of this model. The following contents is researched by this model: (1) The refracted effect of functionally gradient layers on incident wave;(2) the effect of incident angle on the bottom layer's stress;(3) the effect of gradient layer's thickness on the bottom layer's stress. Finally, some interesting, reasonable and important results are obtained by our researching work.
A new organic-inorganic hybrid compound （dienHs）2（P2Mo5O23） （1） [dien=NH（CH2CH2NH2）2] has been hydrothermally synthesized and characterized by elemental analyses, IR spectrum, thermogravimetric analysis, and t...
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A new organic-inorganic hybrid compound （dienHs）2（P2Mo5O23） （1） [dien=NH（CH2CH2NH2）2] has been hydrothermally synthesized and characterized by elemental analyses, IR spectrum, thermogravimetric analysis, and the single crystal X-ray diffraction technique. Compound 1 crystallizes in the triclinic system with space group P1 and a=0.9790（2） nm, b=0.9922（2） nm, c= 1.4644（3） nm, α=95.510（10）°, β=98.860（10）°, γ=95.700（10）°, V=1.3895（5） nm^3, Z=2, R=0.0465. The results show that the compound consists of dienH3^3＋＋ and P2Mo5O23^6-, and the heteropoly anion P2Mo5O23^6- is connected to a 1-D chain structure with the protonated dien by hydrogen bonds.
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