bluuebunny/crossref_metadata_2025 huggingface dataset:
Warping Analysis in Laminated Object Manufacturing Process
Authors: Lin Feng , Sun Wei
Published: July 2002

This study presents an analysis of warping that occurs in the laminated object manufacturing process. Based on the study of thermal-mechanical behavior of the adhesive and its effect on the laminated materials, the cause of warping, the relationship between temperature and adhesive viscosity, and the adhesive connecting intensity is investigated. A heat transfer mathematical model and finite difference solution algorithm was developed to calculate the intralaminar thermal force induced by the material addition in the processing of laminated object manufacturing. The results of the model prediction were compared to available experimental data. Simulation of intralaminar thermal force and case studies show that the processing parameters, such as roller temperature, speed, and contact pressure, the mechanical properties of laminated material and adhesive will all contribute to the formability and warping of the laminated prototype. An optimal combination of the processing parameters may reduce the undesired warping effect.
Effects of Alternate Leading Edge Cutback on Unsteady Cavitation in 4-Bladed Inducers
Authors: Yoshida Yoshiki , Tsujimoto Yoshinobu , Kataoka Dai , Horiguchi Hironori , Wahl Fabien
Published: July 2002

A set of 4-bladed inducers with various amounts of cutback was tested with the aim of suppressing the rotating cavitation by applying alternate leading edge cutback. Unsteady cavitation patterns were observed by means of inlet pressure measurements and high-speed video pictures. It was found that the region with the alternate blade cavitation and asymmetric cavitation were enlarged with the increase of the amount of the cutback. As a result, the region with the rotating cavitation was diminished. At low flow rate, two types of alternate blade cavitation were found as predicted theoretically on 4-bladed inducer with smaller uneven blade length. One of them is with longer cavities on longer blades, and the other is with longer cavities on shorter blades. Switch was observed in these alternate blade cavitation patterns depending whether the cavitation number was increased or decreased. For an inducer with larger amount of cutback, the rotating cavitation and cavitation surge were almost suppressed as expected for a wide range of flow rate and cavitation number, although the cavitation performance was deteriorated. However, we should note that an asymmetric cavitation pattern occurs more easily in inducers with alternate leading edge cutback, and that the unevenness due to the cutback causes uneven blade stress.
Discharge Coefficients of a Preswirl System in Secondary Air Systems
Authors: Dittmann M. , Geis T. , Schramm V. , Kim S. , Wittig S.
Published: July 2002

The discharge behavior of a “direct-transfer” preswirl system has been investigated experimentally. The influences of the pressure ratio and the swirl ratio as well as the influence of the receiver and stator geometry were investigated. The discharge coefficients of the preswirl nozzles are given in the absolute frame of reference. The definition of the discharge coefficient of the receiver holes is applied to the rotating system in order to consider the work done by the rotor. Numerical calculations carried out for a free expansion through the stationary preswirl nozzles show very good agreement with experimental data.
Iterative Fixture Layout and Clamping Force Optimization Using the Genetic Algorithm
Authors: Kulankara Krishnakumar , Satyanarayana Srinath , Melkote Shreyes N.
Published: July 2002

Fixture design is a critical step in machining. An important aspect of fixture design is the optimization of the fixture, the primary objective being the minimization of workpiece deflection by suitably varying the layout of fixture elements and the clamping forces. Previous methods for fixture design optimization have treated fixture layout and clamping force optimization independently and/or used nonlinear programming methods that yield sub-optimal solutions. This paper deals with application of the genetic algorithm (GA) for fixture layout and clamping force optimization for a compliant workpiece. An iterative algorithm that minimizes the workpiece elastic deformation for the entire cutting process by alternatively varying the fixture layout and clamping force is proposed. It is shown via an example of milling fixture design that this algorithm yields a design that is superior to the result obtained from either fixture layout or clamping force optimization alone.
Contact Stresses in Dovetail Attachments: Physical Modeling
Authors: Sinclair G. B. , Cormier N. G.
Published: July 2002

Simple physical models for the stresses in dovetail attachments are developed. These models address: to slip or not to slip, nominal stresses during loading up, peak contact and shear stresses during loading up, hoop stresses during loading up, peak contact and shear stresses during unloading, and hoop stresses during unloading. Comparisons are made with a previous paper on companion finite element modeling. Generally there is good agreement between the simple physical models and the finite element analysis. Together the two identify a pinching mechanism as leading to large fluctuations in hoop stresses at the edges of contact. These fluctuating hoop stresses can be expected to be a major contributor to the fatigue of dovetail attachments.
Review of inverse analysis for indirect measurement of impact
force
Authors: Inoue Hirotsugu , Harrigan John J , Reid Stephen R
Published: July 2002

When dealing with the mechanics of deformable bodies, the variation of the applied force is one of the most important factors to be considered. The mechanical force acting on a body cannot be measured directly. If a body is loaded quasi-statically and if the body deforms linear-elastically, the deformation at any point of the body is proportional to the applied force. Therefore, the variation of the force can be measured indirectly by measuring the variation of the deformation. However, this principle cannot be applied when a body is subjected to an impulsive force. In this case, the propagation of stress waves inside the body cannot be neglected so that the variation of the deformation at any point of the body is no longer the same as the variation of the applied force. Therefore, impact force is much more difficult to measure than quasi-static force. In order to overcome this difficulty, inverse analysis methods to estimate variations of impact force from measured responses of a body have been studied extensively during the last two decades. This article presents a review of methods of inverse analysis for the indirect measurement of impact force.
Vehicle Moving Along an Infinite Beam With Random Surface Irregularities on a Kelvin Foundation
Authors: Andersen L. , Nielsen S. R. K. , Iwankiewicz R.
Published: July 2002

The paper deals with the stochastic analysis of a single-degree-of-freedom vehicle moving at a constant velocity along an infinite Bernoulli-Euler beam with surface irregularities supported by a Kelvin foundation. Both the Bernoulli-Euler beam and the Kelvin foundation are assumed to be constant and deterministic. This also applies to the mass, spring stiffness, and damping coefficient of the vehicle. At first the equations of motion for the vehicle and beam are formulated in a coordinate system following the vehicle. The frequency response functions for the displacement of the vehicle and beam are determined for harmonically varying surface irregularities. Next, the surface irregularities are modeled as a random process. The variance response of the mass of the vehicle as well as the displacement variance of the beam under the oscillator are determined in terms of the autospectrum of the surface irregularities.
The Dynamic Behavior of a Rolling Element Auxiliary Bearing Following Rotor Impact
Authors: Cole M. O. T. , Keogh P. S. , Burrows C. R.
Published: July 2002

The dynamic behavior of a rolling element bearing under auxiliary operation in rotor/magnetic bearing systems is analyzed. When contact with the rotor occurs, the inner race experiences high impact forces and rapid angular acceleration. A finite element model is used to account for flexibility of the inner race in series with non-linear ball stiffnesses arising from the ball-race contact zones. The dynamic conditions during rotor/inner race contact, including ball/race creep, are deduced from a non-linear matrix equation. The influences of bearing parameters are considered together with implications for energy dissipation in the bearing.
Fault Diagnosis of Multistage Manufacturing Processes by Using State Space Approach
Authors: Ding Yu , Ceglarek Dariusz , Shi Jianjun
Published: July 2002

This paper presents a methodology for diagnostics of fixture failures in multistage manufacturing processes (MMP). The diagnostic methodology is based on the state-space model of the MMP process, which includes part fixturing layout geometry and sensor location. The state space model of the MMP characterizes the propagation of fixture fault variation along the production stream, and is used to generate a set of predetermined fault variation patterns. Fixture faults are then isolated by using mapping procedure that combines the Principal Component Analysis (PCA) with pattern recognition approach. The fault diagnosability conditions for three levels: (a) within single station, (b) between stations, and (c) for the overall process, are developed. The presented analysis integrates the state space model of the process and matrix perturbation theory to estimate the upper bound for isolationability of fault pattern vectors caused by correlated and uncorrelated noises. A case study illustrates the proposed method.
Mechanical Behavior of a Cu-Al-Be Shape Memory Alloy Under Multiaxial
Proportional and Nonproportional Loadings
Authors: Bouvet Christophe , Calloch Sylvain , Lexcellent Christian
Published: July 2002

This paper is concerned with the mechanical behavior of a Cu-Al-Be Shape Memory Alloy (SMA). A large experimental database, made of tension-internal pressure tests and biaxial compressive tests, is reported. Particular attention is paid to the behavior of the material under multiaxial proportional and nonproportional loadings. Moreover, these two types of complementary tests allow for the determination, on the one hand, of the shape of the initial surface of transformation onset and, on the other hand, of the initial direction of the transformation strain rate. A generalized macroscopic J2-J3 criterion to describe the transformation onset is proposed and identified.
A Model for Determining the Asperity Engagement Height in Relation to Web Traction Over Non-Vented Rollers
Authors: Rice Brian S. , Cole Kevin A. , Mu¨ftu¨ Sinan
Published: July 2002

The traction developed between a thin flexible web, wrapped around a non-vented, rotating cylindrical roller is studied experimentally and theoretically. A series of eight webs representing a wide range of surface roughness characteristics are traction-tested against the same roller over a wide speed range. A mathematical model that couples air film pressure, web deflection, and asperity deformations is used to model the web/roller interface. An optimization technique is used to estimate the asperity compliance function parameters based on the experimental results and the mathematical model. A new model for determining the asperity engagement height, for surfaces with non-Gaussian peak height distribution, is proposed when the roughness of both surfaces is taken into account. Results are presented that indicate the viability and utility of the new methods.
Vibration Instability in Rolling Mills: Modeling and Experimental Results
Authors: Meehan Paul A.
Published: July 2002

Models for the occurrence of the vibrational instability during rolling known as third octave chatter are presented and discussed. An analysis of rolling mill chatter was performed for the purpose of identifying characteristics of the vibrations and to determine any dependency on the rolling schedule. In particular, a stability criterion for the critical rolling speed is used to predict the maximum rolling speed without chatter instability on schedules from a 5 stand tandem mill rolling thin steel product. The results correlate well with measurements of critical speed occurring on the mill using a vibration monitor. This research provides significant insights into the chatter phenomena and has been used to investigate control methods for suppression of the instability.
Analytical Solutions to H∞ and H2 Optimization of Dynamic Vibration Absorbers Attached to Damped Linear Systems
Authors: Asami Toshihiko , Nishihara Osamu , Baz Amr M.
Published: July 2002

H ∞ and H2 optimization problems of the Voigt type dynamic vibration absorber (DVA) are classical optimization problems, which have been already solved for a special case when the primary system has no damping. However, for the general case including a damped primary system, no one has solved these problems by algebraic approaches. Only the numerical solutions have been proposed until now. This paper presents the analytical solutions for the H∞ and H2 optimization of the DVA attached to the damped primary systems. In the H∞ optimization the DVA is designed such that the maximum amplitude magnification factor of the primary system is minimized; whereas in the H2 optimization the DVA is designed such that the squared area under the response curve of the primary system is minimized. We found a series solution for the H∞ optimization and a closed-form algebraic solution for the H2 optimization. The series solution is then compared with the numerical solution in order to check the accuracy in connection with the truncation error of the series. The exact solution presented in this paper is too complicated to handle by a hand-held calculator, so we proposed an approximate solution for the practical object.
Numerical Simulation of the Dynamic Effects Due to Impeller-Volute Interaction in a Centrifugal Pump
Authors: Gonza´lez Jose´ , Ferna´ndez Joaquı´n , Blanco Eduardo , Santolaria Carlos
Published: July 2002

This paper shows the capability of a numerical simulation in capturing the dynamic and unsteady flow effects inside a centrifugal pump due to the impeller-volute interaction. The object of the study is a commercial centrifugal water pump with backward curved blades, which is built within a vaneless single tongue volute. For the numerical simulation, the viscous Navier-Stokes equations are handled with an unsteady calculation and the sliding mesh technique is applied to take into account the impeller-volute interaction. In keeping the unsteady terms of the equations active it is possible to correctly simulate the effects of the blade passage in front of the tongue and both the flow and pressure fluctuations induced. Time averaged numerical results are compared with the experimental performance curve and good agreement is found. The numerical flow analysis allows the study of different variables which are always difficult to measure experimentally. The dynamic variables obtained with the proposed numerical model are compared with the experimental data. In particular, the amplitude of the fluctuating pressure field at the blade passing frequency is successfully captured by the model for a wide range of operating flow rates. Therefore, the main achievement of the work is in providing the modeling possibilities for the prediction of the dynamic interaction between the flow at the impeller exit and the volute tongue. Such effects at the blade passing frequency appear to follow a clear flow rate dependent spatial pattern around the volute.
Toward Improved Prediction of Heat Transfer on Turbine Blades
Authors: Medic G. , Durbin P. A.
Published: July 2002

Reynolds averaged computations of turbulent flow in a transonic turbine passage are presented to illustrate a manner in which widely used turbulence models sometimes provide poor heat transfer predictions. It is shown that simple, physically and mathematically based constraints can substantially improve those predictions.
Static and Dynamic Tooth Loading in Spur and Helical Geared Systems-Experiments and Model Validation
Authors: Baud S. , Velex P.
Published: July 2002

The primary objective of this study is to validate a specific finite element code aimed at simulating dynamic tooth loading in geared rotor systems. Experiments have been conducted on a high-precision single stage spur and helical gear reducer with flexible shafts mounted on hydrostatic or hydrodynamic bearings. The numerical model is based on classical elements (shaft, lumped stiffnesses, …) and on a gear element which accounts for non-linear time-varying mesh stiffness, gear errors and tooth shape modifications. External and parametric excitations are derived from the instantaneous contact conditions between the mating flanks by using an iterative contact algorithm inserted in a time-step integration scheme. First, experimental and numerical results at low speeds are compared and confirmed that the proposed tooth mesh interface model is valid. Comparisons were then extended to dynamic fillet stresses on both spur and helical gears between 50–6000 rpm on pinion shaft. Despite a localized problem in the case of spur gears with one particular bearing arrangement, the broad agreement between the experimental and numerical response curves demonstrated that the model is representative of the dynamic behavior of geared systems.
Nano-Meter Film Rheology and Asperity Lubrication
Authors: Jacobson Bo
Published: July 2002

It is today possible to manufacture so smooth surfaces that they can elastically conform totally to each other over the whole Hertzian contact area. For pure rolling lubrication such surfaces only need an oil film of molecular dimensions to get total separation. When the rolling motion is combined with sliding, the pressure fluctuations inside the Hertzian contact redistribute the oil and make metal-to-metal contact possible. The redistribution velocity is a function of the slip rate S and the number of asperities N from the inlet to the outlet of the Hertzian contact area. The asperity top oil film thickness decreases with a factor of the order 2NS going from the inlet to the outlet of the Hertzian contact.
Introduction of a Product Family Penalty Function Using Physical Programming
Authors: Messac Achille , Martinez Michael P. , Simpson Timothy W.
Published: July 2002

In an effort to increase customization for today’s highly competitive global markets, many companies are looking to product families to increase product variety and shorten product lead-times while reducing costs. The key to a successful product family is the common product platform around which the product family is derived. Building on our previous work in product family design, we introduce a product family penalty function (PFPF) in this paper to aid in the selection of common and scaling parameters for families of products derived from scalable product platforms. The implementation of the PFPF utilizes the powerful physical programming paradigm to formulate the problem in terms of physically meaningful parameters. To demonstrate the proposed approach, a family of electric motors is developed and compared against previous results. We find that the PFPF enables us to properly balance commonality and performance within the product family through the judicious selection of the common parameters that constitute the product platform and the scaling parameters used to instantiate the product family.
The Tip Region of a Fluid-Driven Fracture in an Elastic Medium
Authors: Garagash D. , Detournay E.
Published: July 2002

The focus of this paper is on constructing the solution for a semi-infinite hydraulic crack for arbitrary toughness, which accounts for the presence of a lag of a priori unknown length between the fluid front and the crack tip. First, we formulate the governing equations for a semi-infinite fluid-driven fracture propagating steadily in an impermeable linear elastic medium. Then, since the pressure in the lag zone is known, we suggest a new inversion of the integral equation from elasticity theory to express the opening in terms of the pressure. We then calculate explicitly the contribution to the opening from the loading in the lag zone, and reformulate the problem over the fluid-filled portion of the crack. The asymptotic forms of the solution near and away from the tip are then discussed. It is shown that the solution is not only consistent with the square root singularity of linear elastic fracture mechanics, but that its asymptotic behavior at infinity is actually given by the singular solution of a semi-infinite hydraulic fracture constructed on the assumption that the fluid flows to the tip of the fracture and that the solid has zero toughness. Further, the asymptotic solution for large dimensionless toughness is derived, including the explicit dependence of the solution on the toughness. The intermediate part of the solution (in the region where the solution evolves from the near tip to the far from the tip asymptote) of the problem in the general case is obtained numerically and relevant results are discussed, including the universal relation between the fluid lag and the toughness. [S0021-8936(00)02401-6]
Anisotropic Nonlinear Kinematic Hardening Rule Parameters From Reversed Proportional Axial-Torsional Cycling
Authors: Moosbrugger J. C.
Published: July 2002

A procedure for determining parameters for anisotropic forms of nonlinear kinematic hardening rules for cyclic plasticity or viscoplasticity models is described. An earlier reported methodology for determining parameters for isotropic forms of uncoupled, superposed Armstrong-Frederick type kinematic hardening rules is extended. For this exercise, the anisotropy of the kinematic hardening rules is restricted to transverse isotropy or orthotropy. A limited number of parameters for such kinematic hardening rules can be determined using reversed proportional tension-torsion cycling of thin-walled tubular specimens. This is demonstrated using tests on type 304 stainless-steel specimens and results are compared to results based on the assumption of isotropic forms of the kinematic hardening rules. [S0094-4289(00)00301-7]
Hydraulic Hammer Drilling Technology: Developments and Capabilities
Authors: Melamed Yuri , Kiselev Andrei , Gelfgat Michael , Dreesen Don , Blacic James
Published: July 2002

Percussion drilling technology was considered many years ago as one of the best approaches for hard rock drilling. Unfortunately, the efficiency of most hydraulic hammer (HH) designs was very low (8 percent maximum), so they were successfully used in shallow boreholes only. Thirty years of research and field drilling experience with HH application in former Soviet Union (FSU) countries led to the development of a new generation of HH designs with a proven efficiency of 40 percent. That advance achieved good operational results in hard rock at depths up to 2000 m and more. The most recent research has shown that there are opportunities to increase HH efficiency up to 70 percent. This paper presents HH basic design principles and operational features. The advantages of HH technology for coiled-tubing drilling is shown on the basis of test results recently conducted in the USA. [S0195-0738(00)00101-1]
Quantitative Visualization of the Flow in a Centrifugal Pump With Diffuser Vanes—I: On Flow Structures and Turbulence
Authors: Sinha Manish , Katz Joseph
Published: July 2002

Particle image velocimetry measurements are used to identify the unsteady flow structures and turbulence in a transparent centrifugal pump with a vaned diffuser. The experiments are being performed in a special facility that enables simultaneous measurements of the flow between the impeller blades, the gap between the impeller and the diffuser, between the diffuser vanes and in the volute. A custom-made 2 K×2 K digital camera with a unique digital image-shifting feature is used to record the images. For the measurements made close to design conditions, phase averaged velocity and vorticity fields are presented along with the corresponding turbulent stresses at different impeller blade orientations (relative to diffuser vanes). The statistically converged results show that the entire flow field is dominated by wakes generated by impeller blades, diffuser vanes, and unsteady separation phenomena. The boundary layer structure in the diffuser and the associated turbulence are strongly affected by the unsteadiness generated by the impeller. The impact of the impeller blade orientation includes direct effects, jetting ahead and a trailing wake behind the blade, as well as indirect effects, such as two types of flow separation within the diffuser. The cyclic variations are higher (typically twice) than the turbulent fluctuations within the impeller and between the diffuser vanes, but decrease below the turbulence level with increasing distance downstream of the trailing edge of the diffuser vanes. [S0098-2202(00)00801-4]
Grinding Damage Prediction for Ceramics via CDM Model
Authors: Zhang Bi , Peng Xianghe
Published: July 2002

A continuum damage mechanics (CDM) model is proposed to predict grinding damage of ceramics. The model takes into account the inelastic behavior of ceramics, the effect of grinding induced hydrostatic pressure and the coupling effect between volumetric and deviatoric deformations on damage. A numerical algorithm is proposed and a three-dimensional finite element program is developed for the model. Damage is analyzed for silicon nitride ceramics subjected to single grit grinding conditions. The damage predicted by the model shows good agreement to the measurement results obtained by experiments. The model can also be used to predict grinding damage for other types of materials. [S1087-1357(00)70301-7]
A Mode-Based Elastohydrodynamic Lubrication Model With Elastic Journal and Sleeve
Authors: Boedo S. , Booker J. F.
Published: July 2002

A mass-conserving, mode-based elastohydrodynamic lubrication model, which includes combined effects of journal and sleeve elasticity, is described. Application to a sample cylindrical bearing system (geometrically similar to automotive main and connecting rod bearings) shows that relative displacement of an elastic journal and sleeve can be represented by a set of mode shapes which are qualitatively similar to those obtained with a rigid journal, while the corresponding mode eigenvalues are found to be dependent on journal elasticity. Performance evaluation under steady and pure squeeze loading shows that a sufficiently compliant hollow journal can reduce film pressure and improve film thickness when compared with its rigid counterpart. [S0742-4787(00)01301-1]
Analysis of Gas Lubricated Foil Thrust Bearings Using Coupled Finite Element and Finite Difference Methods
Authors: Heshmat Crystal A. , Xu David S. , Heshmat Hooshang
Published: July 2002

Load performance of gas lubricated, compliant surface foil thrust bearings has an interlocking relationship with the compliance of the bearing and hydrodynamics of convergent wedge surface. Compliance of the bearing consists of supporting spring elements (elastic foundation) and a smooth elastic top foil. In this paper, a class of gas lubricated foil thrust bearings has been investigated analytically utilizing a novel approach which combines Finite Difference (FD) and Finite Element (FE) methods. Solution of the governing hydrodynamic equations dealing with compressible fluid is coupled with the structural resiliency of the foil bearing surfaces. FD method is utilized for hydrodynamic analysis while FE is used to model structural resiliency. Influence coefficients were generated to address the elasticity effects of combined top foil and elastic foundation on the hydrodynamics of thrust bearing, and were used to expedite the numerical solution. Within 2 to 3 iterations the convergence criterion was reached. The overall program logic proved to be an efficient technique to deal with the complex structural compliance of various foil bearing. Case study has been conducted and sample solutions are provided. Unlike prior analytical investigations, the essential effect of the top foil on the performance of the bearing has been elucidated. [S0742-4787(00)02501-7]
Effect of Surface Finish on Gear Tooth Friction
Authors: Britton R. D. , Elcoate C. D. , Alanou M. P. , Evans H. P. , Snidle R. W.
Published: July 2002

A special four-gear rig has been used to determine gear tooth frictional losses at loads and speeds representative of engineering practice using a gas-turbine engine oil. The effect of surface finish has been investigated by comparing the frictional losses of conventionally ground teeth (with roughness average, Ra, of approximately 0.4 μm) with those of teeth which were superfinished to approximately 0.05 μm Ra. It was found that superfinishing resulted in a reduction of friction of typically 30 percent with correspondingly lower tooth surface temperatures under the same conditions of load and speed. Film generation and frictional traction in the experiments were simulated theoretically using a thin film non-Newtonian micro-elastohydrodynamic lubrication solver, and encouraging agreement between friction measurements and theoretical predictions was obtained. [S0742-4787(00)04701-9]
Elasto-Hydrodynamic Interaction in the Free Abrasive Wafer Slicing Using a Wiresaw: Modeling and Finite Element Analysis
Authors: Bhagavat M. , Prasad V. , Kao I.
Published: July 2002

Free abrasive machining (FAM) process associated with the wiresaw wafer slicing involves a three body abrasion environment. During the process, the cutting action is caused by fine abrasives freely dispersed in the slurry, which get trapped between an axially moving taut wire and the ingot being sliced. In this paper a model is proposed wherein the entry of abrasives into the cutting zone is governed by elasto-hydrodynamic (EHD) interaction between the slurry and the wire. An EHD film is formed by the abrasive carrying viscous slurry, squeezed between the wire and the ingot. This phenomenon is analyzed here using the finite element method. The analysis of such an interaction involves coupling of the basic Reynold’s equation of hydrodynamics with the elasticity equation of wire. Newton–Raphson algorithm is used to formulate and solve this basic coupling. The finite element discretization of the resulting nonlinear equation is carried out using Galerkin’s method of weighted residuals. Basic hydrodynamic interaction model and the incorporation of the entry level impact pressure into the inlet boundary conditions are the two novel features introduced in this work. The analysis yields film thickness profile and pressure distribution as a function of wire speed, slurry viscosity, and slicing conditions. A perusal of results suggests that the wiresawing occurs under “floating” machining condition. The minimum film thickness is greater than the average abrasive size. This is practically very important since the wiresaw is used to slice fragile semiconductor wafers with severe requirements on the surface finish. The possible mechanism by which a floating abrasive can cause material removal is also touched upon in this work. Material removal rate has been modeled based on energy considerations. [S0742-4787(00)00702-5]
A Comparison of Flow Fields Predicted by Various Turbulent Lubrication Models With Existing Measurements
Authors: Wang Xiaojing , Zhang Zhiming , Sun Meili
Published: July 2002

Flow field predictions of various turbulent lubrication models are compared with the existing experimental data of turbulent Couette flow and shear-induced countercurrent flow. [S0742-4787(00)00502-6]
A Detailed Analysis of Film Cooling Physics: Part III— Streamwise Injection With Shaped Holes
Authors: Hyams D. G. , Leylek J. H.
Published: July 2002

The physics of the film cooling process for shaped, streamwise-injected, inclined jets is studied for blowing ratio (M=1.25,1.88), density ratio (DR=1.6), and length-to-diameter ratio (L/D=4) parameters typical of gas turbine operations. A previously documented computational methodology is applied for the study of five distinct film cooling configurations: (1) cylindrical film hole (reference case); (2) forward-diffused film hole; (3) laterally diffused film hole; (4) inlet shaped film hole, and (5) cusp-shaped film hole. The effect of various film hole geometries on both flow and thermal field characteristics is isolated, and the dominant mechanisms responsible for differences in these characteristics are documented. Special consideration is given to explaining crucial flow mechanisms from a vorticity point of view. It is found that vorticity analysis of the flow exiting the film hole can aid substantially in explaining the flow behavior downstream of the film hole. Results indicate that changes in the film hole shape can significantly alter the distribution of the exit-plane variables, therefore strongly affecting the downstream behavior of the film. Computational solutions of the steady, Reynolds-averaged Navier–Stokes equations are obtained using an unstructured/adaptive, fully implicit, pressure-correction solver. Turbulence closure is obtained via the high-Reynolds-number k–ε model with generalized wall functions. Detailed field results as well as surface phenomena involving adiabatic film effectiveness (η) and heat transfer coefficient (h) are presented. When possible, computational results are validated against corresponding experimental cases from data found in the open literature. Detailed comparisons are made between surface and field results of the film hole shapes investigated in this work; design criteria for optimizing downstream heat transfer characteristics are then suggested. [S0889-504X(00)01401-X]
Modeling of Frequency-Dependent Viscoelastic Materials for Active-Passive Vibration Damping
Authors: Trindade M. A. , Benjeddou A. , Ohayon R.
Published: July 2002

This work intends to compare two viscoelastic models, namely ADF and GHM, which account for frequency dependence and allow frequency and time-domain analysis of hybrid active-passive damping treatments, made of viscoelastic layers constrained with piezoelectric actuators. A modal strain energy (MSE) based iterative model is also considered for comparison. As both ADF and GHM models increase the size of the system, through additional dissipative coordinates, and to enhance the control feasibility, a modal reduction technique is presented for the first time for the ADF model and then applied to GHM and MSE ones for comparison. The resulting reduced systems are then used to analyze the performance of a segmented hybrid damped cantilever beam under parameters variations, using a constrained input optimal control algorithm. The open loop modal damping factors for all models match well. However, due to differences between the modal basis used for each model, the closed loop ones were found to be different. [S0739-3717(00)01102-8]
High Resolution XPS Study of a Thin CoO(111) Film Grown on Co(0001)
Authors: Hassel M. , Freund H.-J.
Published: July 2002

Transition metal oxides are often used as the active components in heterogenous catalysis. Therefore the investigation of single crystal oxides as model systems is important to understand the reaction mechanisms on a microscopic level. The reactivity of a (111) surface of ionic rocksalt type structures seems to be rather high as has been established for NiO(111). The ideal (111) surface is polar, and thus unstable, which means that stabilization mechanisms must exist. Here, high resolution XPS measurements of a thin epitaxial CoO(111) film grown on CO(0001) by exposing the surface to ≈10000 L O2 are reported.
Platinum Black by XPS
Authors: Paál Zoltan , Muhler M. , Schlögl R.
Published: July 2002

XPS spectra of Pt black in the as received state showed O and C impurities along with Pt. An in situ treatment by O2 and H2 increased Pt intensity and removed a part of oxygen and carbon impurities. The quasihomogeneous model was used for quantitative evaluation applying atomic sensitivity factors published in the literature (Ref. 1). Decomposition of the O 1s region indicated the presence of adsorbed O, OH, and H2O as well as C—O and C=O species, whereas the C 1s region could be decomposed to give Pt-C, graphite, CxHy polymer, and oxidized C entities.
Design and Operation of an Intense Neutral Beam Source
Authors: Ehlers K. W. , Baker W. R. , Berkner K. H. , Cooper W. S. , Kunkel W. B. , Pyle R. V. , Stearns J. W.
Published: July 2002

We describe a neutral beam source capable of producing pulsed deuterium beams of up to 15 A equivalent current at 20 keV for heating and sustaining fusion plasmas. It consists of a large-area plasma source, multiple-aperture accel-decel extractor, and closely coupled charge-exchange cell. A larger source, to produce 80 A equivalent deuterium beams at 20 keV, is being constructed.
Growth, microstructure, and microhardness of W/Mo nanostructured multilayers
Authors: Geyang Li , Junhua Xu , Liuqiang Zhang , Liang Wu , Mingyuan Gu
Published: July 2002

Artificially modulated W/Mo multilayers on polished stainless-steel substrates with modulation wavelength Λ ranging from 4.0 to 60.0 nm and total film thickness of 2.0 μm were prepared by magnetron sputtering. X-ray diffraction (XRD) and cross-sectional transmission electron microscopy showed that though the polycrystalline films exhibited coherent interfaces, the interfaces have a wave-like appearance due to the different orientations of individual crystals. The interplanar spacings of the W and Mo layers determined by the XRD method in W/Mo multilayers varied with the modulation wavelength. The mechanical properties of these films were investigated by a low-load microhardness indentation technique. The maximum hardness enhancement is about 51% higher than the value calculated from the role of mixtures at wavelength Λ=10.0 nm. The Koehler’s modulus difference model and Cahn’s coherent stress model have been used to estimate the hardness enhancement of W/Mo multilayers. From the comparison of theoretical calculation results with experimental dates, it is obvious that the combination of the two models can explain the hardness enhancement in W/Mo multilayers.
Hard graphitic-like amorphous carbon films with high stress and local microscopic density
Authors: Lacerda R. G. , Hammer P. , Lepienski C. M. , Alvarez F. , Marques F. C.
Published: July 2002

In this work, we report unusual properties of amorphous carbon films prepared by ion beam-assisted deposition using different noble gases (neon, argon, and krypton). Independent of the noble gas ions used, the intrinsic compressive stress and plasmon energy increase sharply with the assisting ion beam energies up to 100 eV. Above this energy, the material properties depend on the mass of the ion. The highest values of stress (∼12 GPa) and plasmon energy associated with the C 1s core electron (29.5 eV) are of the same order of magnitude as those reported for highly tetrahedral amorphous carbon films. Structural results, however, indicate that the material is composed of a hard, highly stressed, and locally dense graphite-like network, i.e., a predominantly sp2-bonded material. It is suggested that the ion bombardment compacts the film structure by reducing the interplanar cluster distances, generating high compressive stress and high local density. The differences in the properties of the films introduced by Ne, Ar, and Kr bombarding ions are also discussed.
In situx-ray photoelectron spectroscopy for thin film synthesis monitoring
Authors: Kelly M. A. , Shek M. L. , Pianetta P. , Gür T. M. , Beasley M. R.
Published: July 2002

We describe an x-ray photoelectron spectroscopy spectrometer capable of determining the composition, thickness, and chemistry of thin film surfaces during growth. The instrument operates at pressures up to a few millitorr, an adequate range for many sputtering, low pressure chemical vapor deposition and thermal evaporation processes. Using a conventional x-ray source, spectra of individual elements can be rapidly accumulated in 10–30 s. To illustrate its capabilities, we present two examples of measurements made with the spectrometer. The low pressure chemical vapor deposition growth of a WO3 film on Si in a 1 mTorr O2 environment, and the thermal oxidation of Si in a 2×10−4 torr O2 environment. We believe these represent the first measurements of such processes in real time by electron spectroscopy. We also describe the spectrometer construction and capabilities in some detail, contemplated improvements in its performance, and anticipated applications.
Reduced brightness of the ZrO/W Schottky electron emitter
Authors: van Veen A. H. V. , Hagen C. W. , Barth J. E. , Kruit P.
Published: July 2002

The reduced brightness for a 〈100〉 ZrO/W Schottky electron emitter with a tip radius of 0.8 μm has been measured. The maximum reduced brightness measured was 2×108 A/(m2 sr V). The measurements of the reduced brightness are compared with the extended Schottky theory and the theory on stochastic Coulomb interactions. At high angular current densities the reduced brightness is limited by statistical Coulomb interactions in the gun lens region. The limits to the maximum reduced brightness in an ideal configuration are explored and found to be 2×109 A/(m2 sr V) for a 0.2 μm tip and a current limiting aperture in the extractor electrode.
A combined ESCA and Auger spectrometer
Authors: Palmberg P. W.
Published: July 2002

A system which accomplishes high−speed, electron−stimulated Auger electron spectroscopy (AES) and x−ray photoelectron spectroscopy with a double−pass cylindrical−mirror analyzer (CMA) is described. The CMA is well suited for AES because of its very high transmission, but has found very limited use in ESCA studies. In the present system the required source definition for use with a large−diameter x−ray beam is achieved with a two−stage CMA. The required energy resolution for ESCA is achieved with spherical retarding grids. A signal level of 16000 cps is attained on the Ag 3−d lines at 1.25−eV FWHM with a 400 W, Mg anode, x−ray source. Adequate luminosity is achieved primarily through high transmission, rather than a large imaged sample area. The small imaged area (less than 2−mm diam) is useful for selected area analysis and simplifies in−depth analysis when combined with inert−gas sputtering.
Electron backscattering from solids and double layers
Authors: Iafrate Gerald J. , McAfee Walter S. , Ballato A.
Published: July 2002

A theoretical study describing primary electron backscattering from solids and double layers is presented. The analysis involves a novel and illuminating extension of Everhart’s theory to obtain the dependence of backscattering coefficient on both retarding potential energy and double-layer target thickness. For solid targets, energy distribution spectra are calculated with the atomic number of the target material as a parameter and are compared with existing experiments to show good agreement. The backscattering analysis for double-layer targets is particularly interesting in that pronounced structure is predicted from the calculated energy distribution spectra due to the assumed discontinuous change in target atomic number across the interface. Comparison of calculated and experimentally obtained backscattering coefficients for double-layer targets and supported thin films also indicate reasonable agreement.
AES study of the adsorption of O2, CO, CO2, and H2O on indium
Authors: Rossnagel S. M. , Dylla H. F. , Cohen S. A.
Published: July 2002

The adsorption of various oxygen-containing gases on clean polycrystalline In has been studied. For the In–O2 system, the relationship between N (E) areas and dN (E)/dE peak heights for In MNN Auger transition was found to be linear. At saturation, an oxygen/indium ratio of 3/2 was measured, consistent with the formation of the stable oxide In2O3. Low-coverage sticking coefficients were found to be ∠0.014 for O2, ∠0.004 for H2O, ∠2×10−5 for CO, and ∠5×10−5 for CO2. In each case, chemical shifts and peaks distortions in the N (E) and dN (E)/dE spectra have been measured for the gas-saturated In, the largest being ∠3 eV for the MNN transition of O2-saturated surface.
Measurement of neutral and ion sputtering yields by matrix isolation spectroscopy
Authors: Steinbrüchel Ch. , Gruen D.M.
Published: July 2002

Matrix isolation spectroscopy is used to investigate the sputtering of several metal surfaces and of TiO2. The sputtered species are collected in a cryogenic noble gas matrix, and their identities and amounts are established from optical absorption spectroscopy. The technique is sensitive enough to allow the measurement of sputtering yields as low as 0.01. Furthermore, it provides for essentially simultaneous detection of neutrals and ions using the same sputtering and collection geometry. Thus, with known detection sensitivities for ions and neutrals, absolute values for sputtered ion fractions can be obtained. Data will be presented for Ti, Zr, Mo, V, and TiO2 bombarded by low energy (∠2 keV) Ar+, O2+, and N2+, and will be compared with various models for calculating sputtering yields.
Pressure measurements in magnetic fusion devices
Authors: Dylla H. F.
Published: July 2002

Accurate pressure measurements are important in magnetic fusion devices for: (1) plasma diagnostic measurements of particle balance and ion temperature; (2) discharge cleaning optimization; (3) vacuum system performance; and (4) tritium accountability. This paper reviews the application, required accuracy, and suitable instrumentation for these measurements. Demonstrated uses of ionization-type and capacitance–diaphragm gauges for various pressure and gas-flow measurements in tokamaks are presented, with specific reference to the effects of magnetic fields on gauge performance and the problems associated with gauge calibration.
Orientation dependence of oxygen adsorption on a cylindrical GaAs crystal
Authors: Ranke W. , Xing Y. R. , Shen G. D.
Published: July 2002

The orientation dependence of oxygen adsorption was studied by AES using a cylindrically shaped GaAs single crystal prepared by ion bombardment and annealing. The cylinder axis was [11̄0] so that the cylinder surface exposed all the main low index surfaces and all transitions between them. The adsorption behavior in the range (001)–(111)Ga–(110)–(111̄)As can basically be understood in terms of enhanced adsorption on edge adjacent sites. A thorough analysis in the range (111)Ga–(110) reveals a transition from steps one (110) layer high near (110) to steps two (110) layers high at (331) between the two low index faces.
Modifications in the phase transition properties of predeposited VO2 films
Authors: Case F. Cardillo
Published: July 2002

Thin films of the phase transition material vanadium dioxide (VO2) were deposited by thermal oxidation of e-beam evaporated vanadium on a variety of bulk materials. Substrate effects on transition temperature are confirmed as being due to a mismatch between film and substrate thermal expansion coefficients. Decreasing tensile stress results in a lowering of VO2 transition temperature. Effects of low-energy Ar+ bombardment on the electrical and optical properties of these predeposited VO2 films were investigated. Bombardment energies in the range 138–500 eV at 1.0–1.3 mA/cm2 for 120–180 s were provided by a Commonwealth Millatron. The higher Ar+ energies resulted in collapse of the VO2 optical transmittance hysteresis loop, while low-energy Ar+ ions caused both a downward shift in the transition temperature and a decrease in hysteresis loop width, suggesting a dependence of these quantities on intrinsic stress. In addition, large decreases in cold-state resistivity are reported and attributed to a reduction of the surface oxide by the low energy argon beam.