Microbeam Characterization of Corning Archeological Reference Glasses: New Additions to the Smithsonian Microbeam Standard Collection

An initial study of the minor element, trace element, and impurities in Corning archeological references glasses have been performed using three microbeam techniques: electron probe microanalysis (EPMA), laser ablation ICP-mass spectrometry (LA ICP-MS), and secondary ion mass spectrometry (SIMS). The EPMA results suggest a significant level of heterogeneity for a number of metals. Conversely, higher precision and a larger sampling volume analysis by LA ICP-MS indicates a high degree of chemical uniformity within all glasses, typically <2 % relative (1 σ). SIMS data reveal that small but measurable quantities of volatile impurities are present in the glasses, including H at roughly the 0.0001 mass fraction level. These glasses show promise for use as secondary standards for minor and trace element analyses of insulating materials such as synthetic ceramics, minerals, and silicate glasses.     

An overview of air-sea interface process studies

Recent progress in the study of air-sea interface processes for momentum, heat, moisture and mass transfer are reviewed in the present article. Except for turbulent structure, we have analysed the other physical mechanisms occurring in the wave boundary layer, such as the roles of the sea surface state, droplets and bubbles due to wave breaking, which at least partly account for the existing discrepancies between theory and observations. The experiments, both over the ocean and in the laboratory, are described briefly. In conclusion, a few perspective trends in this area are suggested for further investigation. The project is financially supported by the Chinese National Science Foundation.     

Quantitative analysis of the bone-hydroxyapatite coating interface

The bone implant interface in stainless steel pins coated with hydroxyapatite, used in a monoaxial fracture external fixation system was examined. The pins were transversally inserted into sheep tibial diaphyses where a defect was created, and they were loaded for 6 weeks. Uncoated pins were implanted as control. The microscopic relation between bone and implant was quantified through image analysis: the residual thickness of the hydroxyapatite coating, pin-bone contact surface and bone ingrowth value in between the threads were measured. The bone tissue at the interface appeared regularly mineralized and viable both in the implants of coated pins and in the control uncoated ones. The ceramic coating showed a slight and not statistically significant increase in thickness. The ceramic coated pins presented contact with bone higher than the uncoated pins (75.6±20.0 versus 47.5±19.4); they also induced a higher bone ingrowth (86.6±22.4 versus 78.7±13.5). Both differences are not statistically significant, but suggestive of a trend. The authors concluded that the hydroxyapatite coating of the pins might improve the performance of external fixators, by favouring bone apposition and reducing rate of loosening.     

An opportunistic analysis of the interface crack

When the loading of an interface crack involves also some shear, one of the contact zones is much larger than the other. Moreover, the small contact zone is extremely short in comparison to the length of the crack. It is possible to take advantage of this fact by neglecting the small contact zone altogether, because the resulting integral equation that pertains to the large contact zone and the conditions at the corresponding crack tip can then be solved in closed form. The paper derives the solution and shows that the results achieved are extremely accurate, provided the large contact zone is long in comparison to the small contact zone, and that it is not necessary for the large contact zone to be of the order of the crack length.

---

Résumé Lorsque la mise en charge d'une fissure d'interface comporte également du cisaillement, l'une des zones de contact aux extrémités de cette fissure se trouve être beaucoup plus grande que l'autre. En outre, la petite zone de contact est comparativement très courte par rapport à la longueur de la fissure. On peut tirer profit de cette constatations en négligeant la petite zone de contact, puisque l'intégrale correspondant à la grande zone et les conditions relatives à la fissure en cet endroit peuvent être résolues sous une forme fermée. On procède à une telle résolution et on montre que les résultats obtenus sont extrèmement précis, pour autant que la grande zone de contact soit comparativement longue par rapport à la petite zone, et qu'il ne soil pas nécessaire qu'elle ait une longueur de l'ordre de celle de la fissure.

     

Fiber and interface strength distribution studies with the single-fiber composite test

Application of the single-fiber composite (sfc) tension test for fiber and interface strength determination is discussed. Fiber breaking and fiber/matrix debond propagation are modelled by Poisson processes. Fiber fragment length distribution as well as debond length dependency upon the applied stress are derived and their interrelation revealed.

Acoustic emission monitoring of the sfc during a test is utilized to obtain the dependency of mean fragment length upon stress and consequently on the Weibull distribution shape and scale parameters. Excellent agreement with data obtained by notoriously complicated conventional fiber tests is observed.     

Gray微束定位辐射准确性的研究

对Gray微束装置的定位辐射准确度进行了全面的实验研究。微束定位辐射的能力表现在辐射点的准确度高低和离子分布区域的大小二个方面。辐射点的准确度取决于样品架的回访精度和图像处理系统的样品识别准确度 ;离子的分布取决于瞄准器的结构。通过对 3 5MeV的3 He2 离子辐射后CR39样品上留下束斑的大小和中心位置的分析 ,得到了有关Gray微束定位辐射能力的数据。在辐射点准确度方面 ,仅由样品架参与工作时 ,真实辐射点落在以预定辐射点为中心 ,以 1 5和 1 2 5 μm为半径的圆内的概率分别为 99 1%和 97 9% ;如果样品架和图像处理系统共同作用 ,那么真实辐射点落在相应区域内的概率分别为 98 4 %和 96 4 %。在离子的分布上 ,大于 99 5 %的离子分布在以真实辐射点为中心、以 7 5 μm为直径的圆内 ,其中的 99 1%又集中在直径为 5 μm的同心圆内     

Plasma-enhanced chemical vapour deposited silicon-nitride films for interface studies

Silicon nitride (SiN _x ) films of varying stoichiometry (x=1.04, 1.39 and 1.63) were deposited on silicon substrates at 250 C by plasma-enhanced chemical vapour deposition (PECVD). The N/Si ratios were determined by electron spectroscopy for chemical analysis (ESCA) and Rutherford backscattering (RBS) measurements. Optical, electrical and interface characterization were carried out for the films. It was observed that nitrogen-rich films (x=1.63) gave the best electrical properties and the lowest interface state density, which was 1.1 × 10¹¹ eV^–1 cm^–2. The resistivity and breakdown field of these films were 5.1 × 10¹³ cm and 1.5 × 10⁶ V cm^–1, respectively.     

主轴系统结合面对主轴系统动力学特性的影响分析

数控机床主轴系统存在着主轴-轴承、主轴-刀柄、刀柄-刀具结合面,这些结合面的特性对主轴系统动力学有着显著的影响,而获得该影响规律对于主轴系统动态设计及动力学修改有着重要意义。本文以某立式加工中心主轴系统为对象,采用有限元法对其进行了动力学建模,在此基础上,对比分析了结合面特性对该主轴系统固有特性和刀尖点频响函数的影响规律。具体可以描述为：主轴-轴承结合面特性影响主轴系统的刚体模态和刀尖点低频段的频响函数;而主轴-刀柄结合面、刀柄-刀具结合面特性直接影响主轴系统的弹性模态和刀尖点高频段频响函数。此外,本文研究也可为主轴系统动力学特性及稳定性预估提供参考。     

Durability studies and characterization of the matrix and fibre-cement interface of asbestos-free fibre-cement products

Organic fibres, both natural and synthetic, have been used as asbestos replacements in cement-based products. The microstructures of these products have been characterized in the fresh state, both normally cured and autoclaved, as well as after natural weathering in Switzerland and the Republic of South Africa. Characterization techniques include electron microscopy, used in both scanning and transmission modes, analytical electron microscopy, and pore structure analysis by mercury intrusion. Differences between cure regimes and exposure conditions are described. The change in the microstructure for both composites were intricate because of the non-isotropic nature of the products. Characterization of typical ageing development phases of the matrix was found to be very complex, although these extensive microstructural changes do not necessarily indicate that the performance of the material is adversely affected.     

Some numerical studies of interface advection properties of level set method

In this paper, we discuss the results of a series of tests carried out to assess the level set methodology for capturing interfaces between two immiscible fluids. The tests are designed to investigate the accuracy of convection process, the preservation of interface shape, and the mass conservation properties of individual fluids. These test cases involve the advection of interfaces of different shapes exposed to translation, rotation, deformation, and shear flow. Prescribed solenoidal velocity fields are used and no attempt is made to couple the advection of the level set function with the momentum equations. For the solution of level set equation we have employed first-order upwind scheme, MacCormack method, second-order ENO scheme, and fifth-order WENO scheme. Our studies show that the level set method perform well when higher-order schemes are used for the solution of advection equation. However, for certain type of shearing and vortical velocity fields mass conservation is an issue on coarser meshes even with higher order schemes. Finer mesh must be used in such situations to reduce numerical diffusion.     

Surface-enhanced Raman spectroscopy studies of surfactant adsorption to a hydrophobic interface

Surface-enhanced Raman spectroscopy is used to investigate the kinetics of adsorption of the cationic surfactant cetylpyridinium chloride (CPC) to hydrophobic surfaces from water. A hydrophobic surface, with stable and reproducible SERS activity, is produced by binding gold colloids to an amine-terminated glass slide and then modifying this surface with octadecyltrimethoxysilane. In situ SERS-detected adsorption of CPC from aqueous solution is found to follow a Frumkin isotherm. Interactions between the charged head groups could be detected in frequency shifts in the symmetric ring breathing mode, consistent with an interfacial surfactant environment similar to a CPC micelle. Rates of surfactant adsorption were determined by time-resolved SERS measurements and were found to be much slower than the diffusion-controlled limit, indicating a significant kinetic barrier to adsorption. Desorption kinetics were heterogeneous, consistent with the spectroscopic results. Alkylsilane-modified gold colloids were shown to be useful substrates for investigating amphiphile adsorption from aqueous solutions to hydrophobic surfaces, where the adsorption kinetics could also be used to determine analyte concentrations in solution.     

An analysis of decohesion along an imperfect interface

A cohesive zone type interface model, taking full account of finite geometry changes, is used to study the decohesion of a viscoplastic block from a rigid substrate. The specific boundary value problem analyzed is a plane strain one with the imposed loading corresponding to overall uniaxial straining. The imperfection takes the form of a non-bonded portion of the interface. Dimensional considerations introduce a characteristic length into the formulation and the decohesion mode shifts from more or less uniform separation along the bond line to crack-like propagation as the ratio of block size to characteristic length increases. Field distributions prior to and accompanying propagation are displayed.     

Three-dimensional analysis of interface cracks in rubber materials

Three-dimensional and plane stress finite element analyses were carried out to investigate the stress fields and fracture parameters of interface cracks in rubber materials. The tearing energy computations for any arbitrarily shaped 3D crack front in dissimilar materials were obtained using the virtual crack extension method. The finite element results obtained are validated against existing alternate solutions and experimental data for cracks in homogeneous as well as bimaterial cases. The effects of different rubber material models, tearing energy distributions, crack extension angles, and three-dimensional regions at the crack tip for interface cracks are presented and discussed. It is shown that nonlinear materials have larger three-dimensional effects near the interface crack front, and that this effect increases as the material mismatch increases.     

A hybrid finite element analysis of interface cracks

A versatile hybrid finite element scheme consisting of special crack-tip elements and crack face contact elements is developed to analyse a partially closed interface crack between two dissimilar anisotropic elastic materials. The crack-tip element incorporates higher-order asymptotic solutions for an interfacial crack tip. These solutions are obtained from complex variable methods in Stroh formalism. For a closed interfacial crack tip, a generalized contact model in which the crack-tip oscillation is eliminated is adopted in the calculation. The hybrid finite element modelling allows the stress singularity at an open and closed crack tip to be accurately treated. The accuracy and convergence of the developed scheme are tested with respect to the known interface crack solutions. Utilizing this numerical scheme, the stress intensity factors and contact zone are calculated for a finite interface crack between a laminated composite material.     

A finite elastostatic analysis of bimaterial interface cracks

A numerical method is developed to study the bimaterial interface problem in Neo-Hookean materials under plane stress conditions. Comparison is made with the analytical predictions for the asymptotic field of the problem. The range of dominance of the asymptotic solution at different load levels is established and the amplitudes of the crack-tip asymptotic field are related to the far field loading. The numerical model is extended to analyze the experiments conducted on specimens with an edge crack at the interface between two dissimilar Solithane plates that are characterized by Mooney-Rivlin material behavior.

---

Résumé On met au point une méthode numérique pour l'étude d'un problème d'interfaces entre deux matériaux néo-Hookiens sollicités en état plan de tension. On compare les résultats avec les prédictions analytiques étabiies pour un champ asymptotique. On établit la gamme dans laquelle la solution asymptotique est dominante, à différents niveaux de charge, et on met en relation l'ampleur du champ asymptotique à l'extrémité de la fissure avec celle du champ de contraintes à une certaine distance. Le modèle numérique est étendu à l'analyse d'essais sur éprouvettes comportant une fissure de bord à l'interface de deux tôles de Solithane caractérisée par un comportement de matériau de Mooney-Rivlin.

     

FIB and TEM studies of interface structure in diamond–SiC composites

The microstructure of diamond–SiC interfaces was studied by transmission electron microscopy (TEM). Specimens were prepared by focused ion beam (FIB) etching from a diamond–SiC composite bulk material. The diamond–SiC interfaces were easily located by high contrast in FIB images of the bulk surface, and site-specific specimen preparation was possible. The possible origin of this high contrast in FIB images compared to SEM images is discussed. TEM images and electron diffraction patterns showed that the diamond and SiC crystals away from the interface region are relatively defect-free, but numerous defects are present at the diamond–SiC interface over a dimension of 600 nm, much larger than the physical interface.     

高速摩擦制动界面振动信号时频法分析技术研究

利用MM-1000型摩擦制动试验机进行了高速摩擦制动试验,使用加速度传感器采集了摩擦制动过程中界面轴向与径向振动信号。利用Morlet小波变换对不同制动压力、干湿工况下的振动信号进行分析,结合摩擦制动过程中瞬时摩擦系数变化对高速摩擦制动界面振动行为时频法分析技术进行了研究。结果表明:重采样能够大幅减小计算量且对低频段振动时频分析无明显影响;Morlet小波时频分析比短时傅里叶变换和HHT边际谱具有更好的分辨率,对制动界面振动信号处理效果更好;时频图中的斜率与制动过程中的转速变化相对应,表明高速摩擦制动过程中转速基本呈线性降低;结合时频图与瞬时摩擦系数曲线可以评估高速摩擦制动过程中界面状况变化过程;振动能量主要集中在基频、二倍频和三倍频,超过三倍频部分能量较少。