空心球金属泡沫的研究进展

空心球金属泡沫兼具开孔和闭孔泡沫的特征,是一种结构可控、性能可靠的高性能金属泡沫,在汽车、航空、航天等领域具有广阔的应用前景。系统地综述了当前空心球金属泡沫的制备工艺、力学与声学性能的研究进展,并对今后的研究方向和发展前景进行了分析。     

单个薄壁多孔金属空心球体力学行为研究

金属空心球多胞材料结构是一种新型的多孔金属材料,它是由多个金属空心球组合而成,对于单个金属空心球的力学行为研究是整体材料力学性能的基础。通过对外径2 mm～3 mm,且壁厚不等厚(壁厚10μm～40μm)的单个超薄壁多孔空心球体进行纳米压痕试验、准静态单轴压缩试验以及纯弹性阶段的压缩试验,进而得到该金属空心球体材料和整个球体的弹性模量等相关力学参数,以及金属空心球体压缩变形过程和特征,并对金属空心球体弹性阶段采用有限元软件Abaqus进行模拟,分析孔隙率对于球体弹性模量的影响,结果表明,随着球壁孔隙率的增大,球体的弹性模量减小,且呈非线性分布,并可以描述成与球壁孔隙率与球壁材料的力学性能关系相同的幂函数形式。     

机载电子设备泡沫金属换热器研究

机载电子设备朝着小型化、高集成度的方向发展,元器件散热问题日趋紧迫。泡沫金属是一种新型的功能材料,可增强电子设备换热器空气侧传热。对泡沫金属的结构、性能特点、换热机理进行了介绍,针对机载电子设备设计了一种泡沫铝换热器,与传统金属翅片换热器进行了实验对比,结果表明,泡沫铝换热器的散热效果明显优于传统金属翅片换热器。     

开孔泡沫金属的结构特性及流体透过性能的研究

依据渗流铸造法制得的开孔泡沫铝合金制品，用灌注石蜡的办法，测试分析了开孔泡沫金属的结构特性，分别计算了各被测试样的孔隙率和通孔率；用自行设计的试验装置，测试研究了泡沫金属的流体透过性能。结果表明：开孔泡沫铝合金具有较高的孔隙率、通孔率和流体透过性能。因此，适合应用在工业中的许多领域。     

规则孔型泡沫金属的设计制造研究

研究规则孔型泡沫金属的结构设计与制造方法，利用三维造型软件Unigraphics，对泡沫金属的结构进行预设计，并利用快速成型与电沉积技术制造出了具有规则孔型结构的泡沫金属。设计了4种不同的泡沫结构，并详细说明了金刚石型泡沫结构的设计及制造方法，分析了其结构参数。本研究设计制造的规则孔型结构的泡沫金属，各项结构参数可调可控，可以最大限度地发挥其使用潜能，获得理想的性能。     

航空发动机通风器金属泡沫性能仿真研究

为研究航空发动机轴心通风器中的核心部件—开孔金属泡沫的阻力性能与油滴穿透率性能,采用X光断层扫描技术获取金属泡沫的扫描模型.通过对模型的样本截取,分析不同样本的压降性能;对其中一个样本采用DPM模型进行油气混合物的穿透率分析.结果表明:泡沫样本截面积与样本厚度对泡沫单位压降性能有一定的影响,但当截面积和厚度大于某一个值...     

泡沫金属材料的特种加工工艺

泡沫金属材料是一种新型功能材料,其结构件具有许多独特性能.为更好地利用泡沫金属,对泡沫金属材料的特种加工工艺和应用展开论述,特别就泡沫金属的数控电火花线切割、水射流加工及激光加工等特种加工工艺展开实验和分析,以便得出较佳的工艺参数和相应的实验结论.     

泡沫金属磁流液阻尼器的优化设计与实验研究

为提高磁流变泡沫金属阻尼器的阻尼力,基于ANSYS有限元仿真软件,以间隙中磁感应强度为优化目标,以活塞工作长度、直径及缸筒壁厚为优化参数,对泡沫金属磁流变阻尼器的各项参数进行优化。组建泡沫金属磁流变阻尼器剪切力测试系统,实验测试阻尼器优化前后的性能。结果表明,施加相同电流及同等剪切速率时,优化后的泡沫金属磁流变液阻尼器输出的阻尼力提高了1.46倍,优化效果明显。     

氧化铝空心球的制备及隔热性能的研究

采用水热法制备了胶体碳球,以碳球为模板,加入氨水或尿素作为沉淀剂制备了氧化铝空心球,将氧化铝空心球用于隔热涂层的制备,并对所制备的氧化铝空心球的微观形貌和涂层的隔热性能进行了表征与测试。结果表明,以尿素为沉淀剂时制备的氧化铝空心球形状规则、壁厚均匀,将制得的氧化铝空心球用在涂层的制备中能起到良好的隔热效果,且当涂层中空心球含量为5%时较经济实用。     

两种消声器的消声性能测定及分析

研究了多孔金属功能材料－－－泡沫铝制成的两种结构的消声器，进行了消声性能对比测试，结果表明，泡沫在消除空气动力噪声方面具有优越的性能。     

Global Approach of Tribomechanical Development of Hybrid Aluminium Matrix Syntactic Foams

Hybrid syntactic foams with AlSi12 aluminium matrix were produced by pressure infiltration. The volume ratio of iron to ceramic hollow sphere reinforcement (in the same size range) was varied, and hybrid syntactic foams were also produced with bimodal size ceramic reinforcement. Previously, a very detailed analysis of the mechanical properties of the composites was made with quasi-static compression tests, and their tribological properties were investigated by pin-on-disc method in dry and lubricated conditions. The present article establishes and clarifies the correlations between mechanical and tribological properties. The coefficient of friction, height loss of the specimens and specific wear showed good correlation with different mechanical parameters, e.g. density, structural stiffness and yield strength. The established trends and correlations between mechanical and tribological behaviour enable a better understanding of materials design and selection for further applications of mechanically loaded sliding machine parts.     

An experimental study on the behaviour under impact loading of metallic cellular materials

This paper presents an experimental study on the impact response of metallic cellular materials, i.e. aluminium honeycombs of various cell sizes and wall thicknesses, aluminium foams made from two different manufacturing processes (IFAM and Cymat), as well as hollow sphere agglomerates (nickel and iron). A 60 mm diameter nylon Hopkinson pressure bar is used to improve the signal/noise ratio and to host larger samples containing a sufficient number of cells. Quasi-static and classical Split Hopkinson Pressure Bar (SHPB) tests as well as direct impact Hopkinson bar tests (higher speeds up to 50 m/s) are performed. Significant rate sensitivities are observed for most of the cellular materials studied. Analyses of the potential causes of this macroscopic rate sensitivity show that the microinertia effect in the successive folding process could be an important factor.     

Size effects in ductile cellular solids. Part I: modeling

In the mechanical testing of metallic foams, an important issue is the effect of the specimen size, relative to the cell size, on the measured properties. Here we analyze size effects for the modulus and strength of regular, hexagonal honeycombs under uniaxial and shear loadings. Size effects for indentation of a honeycomb are evaluated using finite element analysis. Finally, the results for honeycombs are extrapolated to foams. The results are compared with data for metallic foams in the following, companion paper.     

闭孔泡沫铝力学特性及其在汽车碰撞吸能中的应用研究进展

汽车低能耗、安全和轻量化已经成为汽车领域研究的热点问题,闭孔泡沫铝作为一种轻质吸能金属材料,在低密度下具有良好的比刚度和比强度,同时具有良好的抗冲击性和能量吸收性,已逐渐引起汽车产业界地重视。简述泡沫铝单轴压缩试验中弹性模量、抗压强度、屈服强度、平台应力、致密化应变等参数的定义和试验标准;综述闭孔泡沫铝的本构方程的研究现状,重点讨论屈服面模型;总结泡沫铝的微观结构有限元建模方法,比较商业软件中集成的宏观材料模型。归纳吸能材料的特点,分析闭孔泡沫铝的吸能能力和抗冲击能力;综述应变率和冲击速度对泡沫铝吸能特性有无影响的研究进展,并对可能存在的影响进行解释。总结闭孔泡沫铝在汽车轻量化和碰撞安全性领域的应用,具体分析典型的案例。指出当前闭孔泡沫铝的力学特性及其在汽车结构中应用存在的问题与难点,总结并提出本研究领域可以借鉴的研究方向。     

A transient thermal problem: A hollow sphere of strain-hardening material with temperature-dependent properties

This paper is concerned with a polar symmetric transient thermal problem for a hollow sphere of strain-hardening material, the inner boundary of the sphere being subjected to a sudden temperature rise. Thermal and material properties of the medium are dependent on temperature. An illustrative example, involving linear variation of conductivity, thermal expansion, yield stress and quadratic variation of elastic modulus with temperature, has been solved numerically. Stress and plastic strain distributions on loading and residual stress distributions on unloading have been presented.     

基于多孔泡沫金属材料的简易磁流变阻尼器可行性研究

针对磁流变液阻尼器价格昂贵及不易密封且易失效的问题,提出以多孔泡沫金属材料为载体,解决上述应用的瓶颈问题的新理念。介绍基于多孔泡沫金属材料的简易磁流变液阻尼器的概念设计,并对其可行性进行初步研究,初步研究结果表明多孔泡沫金属可以储存磁流变液,同时磁流变液在磁场作用下可以从泡沫金属溢出并实现阻尼功能。     

多孔泡沫铝制备工艺及其应用

泡沫铝具有优良的物理性能,应用前景广阔。本文概述了几种常见的泡沫铝制备工艺,并介绍了泡沫铝的在不同领域的应用。最后指出了泡沫铝技术的研究和工业化规模生产技术的发展方向。     

Frabrication of Au Nanoparticles in Various Shapes and Their Application in Surface-enhanced Raman Scattering

Anisotropic metallic Nanoparticles (NPs) have unique optical properties, such as Surface Enhanced Raman Scattering (SERS)spectroscopy. In this paper, star-shaped and sphere gold NPs were prepared by seed-mediated growth and Frence methods respectively. The reaction process and the effect of reagent in seed-mediated growth of gold nanostar particles were systematically described. After fabricating NPs the authors test their Raman enhancement using Crystal Violet (CV) molecules apart. The experimental results indicated that star-shaped Au NPs had stronger Raman enhancement spectrum than that of sphere Au NPs.     

Analytical solution of wave propagation in a non-homogeneous orthotropic rotating elastic media

In this paper, the natural frequencies of the radial vibrations of a hollow cylinder and hollow sphere with different boundary conditions under influences of rotation and non-homogeneity have been studied. The radial vibrations of orthotropic material as affected by the angular velocity are investigated on the basis of the linear theory of elasticity. The of elastodynamic equations have been solved in analytical form. Numerical results are given and illustrated graphically for each case. Comparisons are made with previous results which given in the absence of rotation and non-homogeneity. The results indicate that the effect of rotation and non-homogeneity is very pronounced.