Site-specific fracture plane determination using the FIB/TEM

A new method for the determination of the crystallographic indices of planar fracture surfaces is described. The key innovation is the use of a focused ion beam instrument to extract two transmission electron microscopy (TEM) foils from the fracture surface. Selected area diffraction of these foils in the TEM allows the determination of the fracture plane from the cross product of two crystallographic line directions contained within the plane. This allows the indices to be determined from relatively small fracture surfaces, affording fracture plane determinations from facets on polycrystalline samples. The validation of this method using cleavage fracture in pure zinc is described.     

Experimental and CFD study on the mass flow-rate characteristic of gas through orifice-type restrictor in aerostatic bearings

This paper describes the experimental and CFD study on the mass flow-rate characteristic through an orifice-type restrictor in aerostatic bearings. In the conventional design of gas-lubricated aerostatic bearings, the mass flow-rate of gas through an orifice-type restrictor is generally derived from a well-known mathematical model, which is originally developed to describe the mass flow-rate property through an ideal nozzle. It is reasonable to doubt if there is any difference between the property of mass flow-rate through an orifice and that through a nozzle. In this paper, therefore, a series of simulations and experiments are carried out and the results show that the mass flow-rate characteristic through an orifice is different from that through a nozzle. Consequently, the conventional model to determine the mass flow-rate through an orifice-type restrictor in aerostatic bearings may have to be updated to the proposed new model for more precise design and modelling of the gas-lubricated aerostatic bearings.     

Fundamental study on electron beam weld sections and strengths using AA6061-T6 aluminum alloy plate

This study was carried out to establish an electron beam welding process for a nuclear fuel plate assembly fabrication. A preliminary investigation for plate fuel fabrication was conducted with a consideration of weld performance using AA6061-T6 aluminum alloy made by the electron beam welding process. The optimum welding parameters for the fuel plate assembly were obtained in terms of the accelerating voltage, beam current and welding time. The soundness of the weld region between the side plate and the end fitting for the fuel plate assembly was proven by the intact of the weld metal on the fractured surfaces. The integrity of the welds by the electron beam welding process was also confirmed by the results of the tensile test, an examination of the cross sections and the fracture surfaces of the welded specimens.     

In-flight calibration of mesospheric rocket plasma probes

Many effects and factors can influence the efficiency of a rocket plasma probe. These include payload charging, solar illumination, rocket payload orientation and rotation, and dust impact induced secondary charge production. As a consequence, considerable uncertainties can arise in the determination of the effective cross sections of plasma probes and measured electron and ion densities. We present a new method for calibrating mesospheric rocket plasma probes and obtaining reliable measurements of plasma densities. This method can be used if a payload also carries a probe for measuring the dust charge density. It is based on that a dust probe's effective cross section for measuring the charged component of dust normally is nearly equal to its geometric cross section, and it involves the comparison of variations in the dust charge density measured with the dust detector to the corresponding current variations measured with the electron and/or ion probes. In cases in which the dust charge density is significantly smaller than the electron density, the relation between plasma and dust charge density variations can be simplified and used to infer the effective cross sections of the plasma probes. We illustrate the utility of the method by analysing the data from a specific rocket flight of a payload containing both dust and electron probes.     

A hybrid approach to smooth surface reconstruction from 2-D cross sections

This article presents a hybrid approach to smooth surface reconstruction from serial cross sections, where the number of contours varies from section to section. In a triangular surface-based approach taken in most reconstruction methods, a triangular surface is constructed by stitching triangular patches over a triangular net generated from the compiled contours. In the proposed approach, the resulting surface is a G¹ composite surface consisting of three kinds of surfaces: skinned, branched, and capped surfaces. Each skinned surface is first represented by a B-spline surface approximating the serial contours of the skinned region and then is transformed into a mesh of rectangular Bezier patches. On branched and capped regions, triangular G¹ surfaces are constructed such that the connections between the triangular surfaces and their neighbouring surfaces are G¹ continuous. Because each skinned region is represented by an approximated rectangular C² surface instead of an interpolated triangular G¹ surface, the proposed approach can provide more visually pleasing surfaces and realize more efficient data reduction than the triangular surface-based approach. Some experimental results demonstrate its usefulness and quality.     

计算离心泵面积比和蜗壳面积的方法

依据离心泵的面积比原理,推导得出了计算离心泵面积比的计算公式,公式体现了面积比值和叶轮、蜗壳的水力参数关系。提出建立在面积比原理基础上、低比转速离心泵在加大流量设计后的面积比、蜗壳第八断面面积的计算方法及公式,面积比及蜗壳的第八断面面积和泵的流量加大系数、比转速加大系数得到了联系,也和叶轮、蜗壳的水力参数有关。解决泵行业一直依据经验统计值确定面积比而不能使低比转速离心泵在设计点效率最高这一问题。实例表明:提出的计算方法能够提高低比转速离心泵的效率,充实低比转速离心泵的设计理论。     

Flow measurement system model with distributed resources

The paper describes a general flow measurement system model with distributed resources based on Distributed Component Object Model (DCOM). Complex flow-rate calculation procedures are decomposed and distributed throughout the measurement system. The paper explains to what extent a flow measurement process can be partitioned into the services that can be realized as separate objects shareable across the network. Certain measurement system components perform local measurements and/or calculations and communicate with a remote measurement system resource via intranet/internet. The measurement system comprises direct measurements of the primary measurement quantities, the calculation of the flow-rate and the calculation of the physical properties for various gases, gas mixtures, water and steam. Using DCOM the measurement system automatically activates the remote client/server components that carry out flow-rate calculations in real time. The measurement system covers different measurement procedures and a variety of primary elements. The performances of the measurement system model have been verified by realizing a measurement system with two measuring sections.     

Adsorption-desorption characteristics of explosive vapors investigated with microcantilevers

Understanding the kinetics of adsorption and desorption of explosive vapors such as TNT from surfaces is important in the design of sensors. We report for the first time, the adsorption-desorption characteristics of TNT from a Si-microcantilever exposed to vapors of TNT. It was observed that TNT readily sticks to the exposed Si surface with the adsorption kinetics showing an initial exponential behavior followed by roughly linear kinetics. It was also observed that for cantilever temperatures close to room temperature, TNT desorbs spontaneously from the surface with decaying exponential kinetics. Based on the known equilibrium partial vapor pressures of TNT, the "effective" sticking coefficient for the silicon oxide surface at room temperature under the experimental conditions was calculated to be about 0.02. This information can be very useful in the design of sensors and that of vapor-delivery systems.     

Computer-based determination of size and shape in living cells

Measurement of cell volume in living epithelial cells has become an important technique in studies of membrane transport processes that function in cell volume regulation. Planimetry of video images of optical sections enables the measurement of the cross sectional area of each section. Cell volume is calculated from the measured area of each section and the known focus displacements. In the past the measurement of cross section area has been done by manual positioning of a cursor superimposed on the video image. Each experiment generates approximately 200 images in which two or more cells may be analysed. We have developed a computer-based method that uses one image as a template, and allows automated area determination of successive images by template matching and digital image processing. This new method is comparable to the older method in speed and accuracy, but requires much less effort from the experimenter.     

基于临界曲面的改进Paris定律球轴承疲劳寿命预测方法

通过场发射扫描电镜对球轴承疲劳故障点微观结构进行观察,发现裂纹总是沿着某个曲面进行萌生和扩展,扩展到一定程度后发生断裂形成近似椭圆形状的剥落点,随着球轴承的运转,不仅断裂后的裂纹发生二次剥落,而且剥落点将在新的曲面上发生多次剥落,形成断层形貌。基于此种现象,提出球轴承临界曲面的概念,假定裂纹的萌生和扩展均在此临界曲面上,将三维裂纹扩展问题转化为二维裂纹扩展问题进行分析。在临界曲面概念的基础上,提出改进的Paris疲劳寿命预测模型,将疲劳寿命分为裂纹扩展和剥落点增大两部分,分段采用改进的Paris定律预测球轴承的疲劳寿命。通过多套SKF 6205深沟球轴承疲劳寿命试验数据进行验证,与传统的SKF L-P公式预测结果相比,提出的方法能够较好地预测球轴承的疲劳寿命。     

The mechanism of material removal in fretting

The fretting of annealed 4130 steel in air at room temperature was studied to determine the mechanisms of material removal and debris formation in fretting. On the basis of information developed by examination of the fretted surfaces, cross sections of the fretted surfaces and the fretting debris it was found that metallic debris was generated by the break up of the fretted surfaces into metal particles with a flake-like morphology. The abrasion or adhesive metal transfer mechanisms proposed to explain metal removal in fretting do not account for the morphology and surface features of the metallic debris, while the delamination theory of wear proposed by Suh accounts for both. It is concluded that a delamination mechanism is the most suitable model for the metal removal process in fretting under the conditions studied.     

Determination of the principal directions of composite helicopter rotor blades with arbitrary cross sections

Modern helicopter rotor blades with non-homogeneous cross sections, composed of anisotropic material, require highly sophisticated structural analysis because of various cross sectional geometry and material properties. They may be subjected by the combined axial, bending, and torsional loading, and the dynamic and static behaviors of rotor blades are seriously influenced by the structural coupling under rotating condition. To simplify the analysis procedure using one dimensional beam model, it is necessary to determine the principal coordinate of the rotor blade. In this study, a method for the determination of the principal coordinate including elastic and shear centers is presented, based upon continuum mechanics. The scheme is verified by comparing the results with confirmed experimental results.     

Low-energy electron/atom elastic scattering cross sections from 0.1–30 keV

Empirical forms for electron/atom scattering cross sections predict backscattering factors that compare well with those calculated using tabulated Mott data from 0.1 to 30 keV. The form of the empirical total cross section is similar to the screened Rutherford cross section. The fit to the tabulated differential Mott cross sections is decomposed into two parts, one part being of the same mathematical form as the screened Rutherford cross section (σ_R), and the second part being an isotropic distribution (σ_I). The ratio of the total cross sections (σ_R/σ_I) between the screened Rutherford part of the differential scattering cross section and the isotropic part of the distribution is fitted to give the same ratio of forward to backscattered currents as the tabulated Mott differential cross sections. The three equations, one for the total elastic cross section and two describing the differential cross section—one for the Rutherford screening parameter and one for the ratio σ_R/σ_I—give backscattering results covering all the major trends with energy and atomic number compared with the backscattering coefficients calculated using tabulated Mott cross sections. However, agreement with experiment is poor for some well-researched examples such as Au. Monte Carlo calculations using the empirical cross sections show that surface effects may be critical in interpreting experimental results.     

气动元件等温流动近似流量公式的探讨

本文考虑了可压缩气体的特点,对伯努利方程作了修正,在此基础上推导出了可压缩气体等温流动下的近似流量公式。在近似情况下,所推导出的公式与常用的简易流量公式是一致的。本文在理论上证明了流量特性曲线在亚声速区近似一椭圆曲线。推导出了可压缩气体直接排入大气中的近似流量公式,它与雍塞流公式一致。本文还推导出了不可压缩气体近似流量公式,研究表明,在亚声速区,流量与压力比近于一个抛物线关系。     

Recurrent Neural Network based Soft Sensor for flow estimation in Liquid Rocket Engine Injector calibration

Injector is the critical element in the Liquid Rocket Engine (LRE), to ensure proper mixing of propellants (fuel and oxidizer) in the thrust chamber for achieving the optimum thrust. LRE injector is calibrated in order to deliver required flow rates of propellants by sizing the orifices through simple injector water calibration (IWC) techniques. In LRE-IWC process, a huge 6” turbine flow meter (TFM) is employed for the flow-rate measurement. In order to achieve and maintain the required accuracy and precision in the LRE-IWC process, periodical calibration of TFM is mandatory. It involves tremendous time, cost and human effort. Soft sensors can provide an economical and effective alternative solution for TFM flow-rate measurement. The objective of the proposed work is to develop and implement a recurrent neural network based soft sensor (RNN-SS) for TFM flow-rate measurement. In the LRE-IWC process, experimental flow trials were carried out for different flow patterns, and the necessary measurement data were generated for the soft sensor design. The designed RNN-SS was trained by tuning various hyper parameters to replace the TFM, using three related measurement parameters acquired during the experimental trials. The precise TFM flow-rate estimation was achieved by the designed RNN-SS, with a worst-case mean absolute percentage error (MAPE) of 1.91% for the experimental flow patterns considered, with good repeat-ability. The proposed RNN-SS model for TFM flow-rate estimation gives a MAPE of 0.58%, for the required flow-pattern which is well suited for practical use.     

Dry Sliding Friction and Wear Behaviour of an Electron Beam Melted Hypereutectic Al–Si Alloy

The economic and environmental benefits of using light-weighting technology in automotive applications continue to attract attention for feasible commercial solutions. This study investigates the use of pulsed electron beam melting of a hypereutectic Al–Si alloy as a possible modification procedure for cylinder crankcase bore facing surfaces. Machined surfaces of an A390 alloy were subjected to five pulsed electron doses with an applied cathode potential between 16.5 and 36 kV. It was found that increasing beam accelerating voltages led to an initial decrease (1.4 μm R _a) but subsequent increase (4.0 μm R _a) in average surface roughness values associated with surface crater formation due to sub-surface melting and eruption. Surfaces were tested under dry sliding tribological conditions against 52100 bearing steel in a reciprocating geometry. Average dynamic friction coefficients were higher (0.9) compared to the untreated alloy surface (0.6) as a result of a greater degree of adhesion to the counterface. However, FIB cross sections of worn surfaces indicated that this activated an oxidative type wear process which ultimately led to the formation of a beneficial surface tribo-film on the EBM-treated surfaces, improving the specific wear rates by up to 66%.     

Imaging analysis of the interface between osteoblasts and microrough surfaces of laser‐sintered titanium alloy constructs

Previous work using focused ion beam (FIB) analysis of osteoblasts on smooth and microrough Ti surfaces showed that the average cell aspect ratio and distance from the surface are greater on the rough surface. In order to better interrogate the relationship between individual cells and their substrate using multiple imaging modalities, we developed a method that tracks the same cell across confocal laser scanning microscopy (CLSM) to correlate surface microroughness with cell morphology and cytoskeleton; scanning electron microscopy (SEM) to provide higher resolution for observation of nanoroughness as well as chemical mapping via energy dispersive X‐ray spectroscopy; and transmission electron microscopy (TEM) for high‐resolution imaging. FIB was used to prepare thin sections of the cell‐material interface for TEM, or for three‐dimensional electron tomography. Cells were cultured on laser‐sintered Ti‐6Al‐4V substrates with polished or etched surfaces. Direct cell to surface attachments were observed across surfaces, though bridging across macroscale surface features occurred on rough substrates. Our results show that surface roughness, cell cytoskeleton and gross morphology can be correlated with the cell‐material cross‐sectional interface at the single cell level across multiple high‐resolution imaging modalities. This work provides a platform method for further investigating mechanisms of the cell‐material interface.     

Cross-talk effect in electrostatic based capillary array nozzles

Electrohydrodynamic printing is a promising technique for printed electronics application. Most researchers working in this field are using a single nozzle configuration. However, for large area printing a multi-nozzle setup will be required for time and cost effective process. In this paper the influence of electric field and flow-rate on jetting angle on multi-nozzle array has been investigated experimentally. A three nozzle setup has been used in a linear array by using glass capillary as a nozzle with independent voltage applied on each nozzle and independent ink supply. The experiments are performed by changing the nozzle to nozzle gap and the effect on the jetting angle has been investigated. It has been observed that by increasing the applied voltage the jetting angle also increases at fixed flow-rate. In case of increasing the flow-rate, the jetting angle first increases with increase in flow-rate, but as the flow-rate increases at certain level the jetting angle decreases; moreover, at a high flow-rate the cone-jet length starts increasing. Numerical simulation has been performed to have a better understanding of the electric-field with respect to jetting angles. The influence of one nozzle on another nozzle is also investigated by operating the nozzle independently by using different operating cases. The cross-talk effect is also minimized by reducing the nozzle diameter. At 250 μm nozzle diameter the cross-talk effect was negligible for 5 mm nozzle-to-nozzle gap. This study will help in better understanding of the interaction between different nozzles in multi-nozzle cases and better design of the multi-nozzle system by minimizing the effects of adjacent nozzles for multi-nozzle electrohydrodynamic printing system.     

Developing of N‐(4‐methylpyrimidine‐2‐yl)methacrylamide Langmuir–Blodgett thin film chemical sensor via quartz crystal microbalance technique

In the present work, the characterization and gas sensing properties of newly synthesized N‐(4‐methylpyrimidine‐2‐yl)methacrylamide ( N‐MPMA ) monomer Langmuir–Blodgett (LB) thin films were investigated. The UV–visible spectroscopy, quartz crystal microbalance (QCM), and atomic force microscopy were utilized to characterize N‐MPMA LB thin films. The surface behavior of N‐MPMA monolayer was stable and allowed an effective transfer at a surface pressure of 14 mN/m. The mass change/unit area value of the N‐MPMA LB thin film deposited quartz crystal surfaces was investigated. The amount of N‐MPMA LB thin film deposited on the substrate for bilayer was calculated as 228.72 ng (86.31 ng/mm²) and 12.5 Hz frequency shift was observed for each layer of the N‐MPMA film. The kinetic responses of N‐MPMA LB film against chloroform, dichloromethane, benzene, and toluene were measured via QCM system at room temperature. N‐MPMA QCM sensor results displayed that chloroform has the largest frequency shifts compared with the other vapors used in the present work and these results can be illuminating in terms of physical properties of organic vapors.     

Mott factors of P,V, Fe,Ga, As,Pd, In,Ta, and W for 500–3000 eV electrons

Mott scattering factors are needed for the quantitative interpretation of elastic scattering phenomena in electron spectroscopy and microscopy. The inelastic mean free path of electrons has been deduced from the elastic peak intensity. The theoretical approach is based on the effective elastic cross section derived from the differential elastic cross sections. In the present work they are calculated using the partial wave expansion method, supplying as well the Mott scattering factors. Tabulated data are presented for a number of elements and 500–3000 eV electrons in steps of 2° or 5° of the scattering angle θ. The effective and total elastic scattering cross sections are also presented.