Investigation of wear phenomena by microscopy

This paper discusses the various wear mechanisms involved in the loss of material from metallic and nonmetallic surfaces. The results presented indicate how various microscopy techniques used in conjunction with other analytical tools can assist in the elucidation of a wear mechanism. Microscopy is the single most important tool for the study of the wear of surfaces, to assess address inherent mechanisms of the material removal process.     

具有主、被动约束层阻尼的拉压型结构研究

粘弹性材料已广泛用于阻尼结构的弯曲振动。具有主动与被动相结合的约束层 阻尼技术研究目前也多集中于梁、板等结构的弯曲振动,而主、被动约束层阻尼拉压 型结构则很少研究。本文给出了一种主、被动约束层阻尼拉压型结构模型,推导了一 些数学表达式,给出了优化设计方法及分析结果。     

Momentum-resolved EELS and EMCD spectra from the atomic multiplet theory: Application to magnetite

While the energy loss near edge structures of metallic crystals can be calculated with a good accuracy using density functional theory based codes, core-level spectra of transition metal oxides show pronounced multiplet effects which are better described by atomic multiplet codes. We describe the formalism which allows to calculate momentum-resolved electron energy loss spectra in the electric dipole approximation from the atomic multiplet theory, and we apply this formalism to the calculation of energy loss magnetic chiral dichroic spectra of magnetic transition metal oxides. Explicit results are given for magnetite Fe₃O₄.     

Determination of the thermal conductivity of graphite and high-temperature alloys by the laser-flash method

Thermal conductivity measurements at very high temperatures (above 1000°C) are difficult, particularly because of the heat loss by radiation which is hard to avoid when using all the steady-state methods. But, in many cases, the experimental problems can be overcome by measuring the thermal diffusivity and calculating the conductivity data after additional determinations of specific heat and density have been made.

For some high-temperature materials (graphite and metallic alloys), this procedure was chosen to determine the thermal conductivities. Therefore an apparatus was designed based on the known method, but with some special adaptations. Standard materials were tested in this way to show its advantages. The laser-flash apparatus is described, and the results obtained are reported and discussed.     

A magnetron sputtering system for the preparation of patterned thin films and in situ thin film electrical resistance measurements

We describe a versatile three gun magnetron sputtering system with a custom made sample holder for in situ electrical resistance measurements, both during film growth and ambient changes on film electrical properties. The sample holder allows for the preparation of patterned thin film structures, using up to five different shadow masks without breaking vacuum. We show how the system is used to monitor the electrical resistance of thin metallic films during growth and to study the thermodynamics of hydrogen uptake in metallic thin films. Furthermore, we demonstrate the growth of thin film capacitors, where patterned films are created using shadow masks.     

Self-organized nanotemplating on misfit dislocation networks investigated by scanning tunneling microscopy

Self-ordering growth of nanoarrays on strained metallic interfaces is an attractive option for preparing highly ordered nanotemplates. The great potential of this natural templating approach is that symmetry, feature sizes, and density are predicted to depend on the interfacial stress in these strained layers, which can be adjusted by changing the substrate-thin film composition, temperature, and adlayer coverage. This bottom-up approach of growing nanostructured two-dimensional ordered arrays of clusters on the misfit dislocation networks of strained metallic thin films and surfaces requires a detailed understanding of the nucleation and film-adsorbate interaction processes. Here we show how high resolution, large scale, variable temperature scanning tunneling microscopy imaging can improve our understanding of these self-assembly processes.     

Using atom probe tomography to analyse MAX-phase materials

Ti₂AlC belongs to an interesting group of materials with both metallic and ceramic properties. This material is highly attractive as a candidate for corrosion resistant coatings. The process of fabrication of such coatings is in the investigation stage only and the detailed knowledge of the structure and chemistry of the produced coatings is important for optimisation of their properties. In this work the applicability of atom probe tomography for investigation of both Ti₂AlC bulk materials and coatings was tested. We show that for the first time, Ti₂AlC has successfully been analysed using laser pulsing mode in a local electrode atom probe and the results from analysis of both bulk Ti₂AlC and Ti₂AlC based spray deposited coatings are presented. It appears that, in this particular material system, it is difficult to obtain the accurate stoichiometry. This is due to the loss of detection because of unavoidable multiple events and due to the peak overlaps present. Methods of how to approach these problems are discussed.     

钣金自动展开及数控切割

阐述怎样利用AutoCAD二次开发技术开发软件钣金自动展开系统及怎样应用自动编程软件自动编程，实现数控下料。     

基于钛酸锶的可调太赫兹超材料吸波器设计

热敏钛酸锶(SrTiO3)作为铁电晶体,在微波和太赫兹波段有很强的可调性,具有潜在价值。利用热电磁的可调性实现智能操作,提出了一种基于SrTiO3晶体的具有太赫兹波段吸收的热可调超材料。吸收超材料(AM)由Floquet线性周期排列单元形成,该单元由金属接地平面和菱形金属贴片中嵌入的交叉SrTiO3材料组成,并由FR-4介电层隔开。该超材料吸波器通过改变温度来实现频率的可调。详细讨论了SrTiO3的介电常数,以说明如何产生与热转换的可重构性。数值结果表明,当温度从280 K增加到360 K时,吸收带的可调谐带宽达到90 GHz,相应的吸收率达到99%以上。随着温度的升高,共振频率将产生蓝移。本文提出的被动热可调谐超材料可作为传感、材料检测和频率选择性热发射器的潜在候选材料。     

Comparative study of dental enamel loss after debonding braces by analytical scanning electron microscopy (SEM)

Clinical procedures when shear forces are applied to brackets suggest adhesion forces between 2.8 and 10.0 MPa as appropriate. In this study dental enamel was evaluated by scanning electron microscopy (SEM) before and after removing the brackets. Thirty bicuspids (previous prophylaxis) with metallic brackets (Roth Inovation 0.022 GAC), Transbond Plus SEP 3M Unitek adhesive and Transbond XT 3M resin were used. The samples were preserved to 37°C during 24 hr and submited to tangential forces with the Instron Universal machine 1.0 mm/min speed load strength resistance debonding. Also the Adhesive Remanent Index (ARI) test was made, evaluating the bracket base and the bicuspid surface. All the bracket SEM images were processed with AutoCAD to determine the enamel detached area. The average value was 6.86 MPa (SD ± 3.2 MPa). ARI value 1= 63.3%, value 2= 20%, value 3= 13.3% and 33% presented value 0. All those samples with dental enamel loss, presented different situations as fractures, ledges, horizontal, and vertical loss in some cases, and some scratch lines. There is no association between the debonding resistance and enamel presence. Less than half of the remanent adhesive on the dental enamel was present in most of the samples when the ARI test was applied. When the resin area increases, the debonding resistance also increases, and when the enamel loss increases, the resin free metallic area of the bracket base decreases in the debonding.     

Performance and applications of electron energy loss spectroscopy in stem

When coupled in the image mode to a VG-HB501 microscope, the spectrometer designed by O. Krivanek and manufactured by Gatan Inc. is well suited for resolving analytical problems with a high spatial resolution. It actually records energy loss spectra from areas as small as 0.5 nm with a typical energy resolution of 1 eV over the energy loss range and with a good efficiency in collecting inelastic electrons. During the last few months, this high performance combination of microscope and spectrometer has been used to investigate (a) detection limits in EELS which are presently estimated of the order of ten atoms in a test situation such as metallic clusters deposited on a very thin carbon layer; (b) quantitative chemical analysis of representative nanovolumes of complex oxide specimens, emphasizing several aspects of elemental segregation in the neighborhood of grain boundaries and within vitreous areas; (c) changes of fine structures close to the K-oxygen threshold, due to different bonding states; and (d) efficient Z-contrast imaging modes on sections of embedded biological material without metallic staining.     

Application of Wavelet Analysis in Signal De-noising of Blast Shock Wave Overpressure

It's a problem to be solved how to de-noise the signal of blast shock wave overpressure.In the conventional methods,the high frequency of the signal is cut directly by some mathematics algorithms,such as Fourier Transform,but some of the useful signal will be cut together.We adopt a new method for the signal de-noising of shock wave overpressure by wavelet analysis.There are four steps in this method.Firstly,the original signal is de-cpmposed.Then the time-frequency features of the signal and noise are analyzed.Thirdly,the noise is separated from the signal by only cutting its frequency while the useful signal frequency is reserved as much as possible.Lastly,the useful signal with least loss of information is recovered by reconstruction process.To verify this method,a blast shock wave signal is de-noised with FFT to make a comparison.The results show that the signal de-noised by wavelet analysis approximates the ideal signal well.     

STUDY ON JOINING PROCESS FOR LAMINATED OBJECT MANUFACTURING USING METALAS MODELING MATERIALS

In order to solve some key problems associated with the rapid manufacturing of metallic functional part, a new technique using vacuum solid-state pressure diffusion welding process to join the metallic slice sheets is put forward. The following results can be drawn from the experiments: only 1% shrinkage happened in the stack direction and it came from the regular system error. The atoms diffuse between joint interfaces clearly and new grains formed meanwhile. The average shear strength of welding zone is more than 100 MPa and micro hardness of welding zone is almost the same as that of matrix. It is shown from above results that the vacuum solid-state pressure diffusion welding process is an available technique to join metal slice sheets for the rapid manufacturing of metallic functional parts.     

Excel2000及AutoCAD2004在高炉炉壳圆锥管段下料中的应用

本文阐述如何将Excel2000与普通的计算法相结合,如何将AutoCAD2004与普通的图解法相结合,快速、准确获取 高炉壳圆锥管段下料所需数据。     

Vit1块体金属玻璃微铣削表面粗糙度试验研究

为研究金属玻璃的微铣削表面粗糙度,采用直径为0.5 mm的双刃硬质合金微铣刀,在Vit1块体金属玻璃表面加工微尺度沟槽结构;以试件表面粗糙度Ra值为衡量指标,利用三因素五水平正交试验方法分析主轴转速、进给速度和铣削深度对微铣削表面质量的影响。试验结果表明:主轴转速对表面质量影响最为显著,而进给速度影响较小。对影响表面质量及形貌的原因进行了深入分析,其结果对研究Vit1块体金属玻璃的微铣削加工机理具有一定的借鉴意义。     

基于iFIX的软件报警技术在自动测量系统中的实现

文中就自动测量系统的iFIX工控软件的报警管理进行了分析介绍,详细阐述了如何运用报警过滤、报警计数器等一些iFIX报警技术解决错报、误报和重复报警等现象,以及如何尽快发现一些重大报警,从而避免对用户造成损失。     

Sliding wear of quasicrystalline coatings

The mass loss during sliding wear of several quasicrystalline (QC) coatings has been measured. QC coatings of the Al–Cu–Fe, Al–Cu–Fe–Cr and Al–Pd–Mn systems have been investigated and compared with a hardened tool steel and a WC–6% Co hardmetal. The wear rates of the coatings are in general comparable to conventional metallic materials. There is some variation in sliding wear behaviour of different QC coatings. This revised version was published online in August 2006 with corrections to the Cover Date.     

可重复使用运载器金属热防护系统的历史与发展动态分析

随着重复使用运载器的研制和发展,金属热防护系统的发展从简单到复杂;金属热防护系统的优点使得其在热防护系统中的地位日益提高。这里总结了金属热防护系统的历史发展历程,描述了其典型细节设计,提出了其存在的问题,展望了金属热防护系统的发展方向,为未来设计提供借鉴。     

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。