bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Limit Distribution for the Analysis of Randomly Mistuned Bladed Disks1
Authors: Mignolet M. P. , Lin C.-C. , LaBorde B. H.
Published: July 2002

A recently introduced perturbation technique is employed to derive a novel closed form model for the probability density function of the resonant and near-resonant, steady state amplitude of blade response in randomly mistuned disks. In its most general form, this model is shown to involve six parameters but, in the important practical case of a pure stiffness (or frequency) mistuning, only three parameters are usually sufficient to completely specify this distribution. A series of numerical examples are presented that demonstrate the reliability of this three-parameter model in accurately predicting the entire probability density function of the amplitude of response, and in particular the large amplitude tail of this distribution, which is the most critical effect of mistuning.
A Piezoelectric Valve-Less Pump-Dynamic Model
Authors: Ullmann Amos , Fono Ilan , Taitel Yehuda
Published: July 2002

A complete dynamic model for the simulation of the valve-less piezoelectric pump performance is presented. In this model the piezoelectric action is considered as a periodic force acting on a pumping membrane. The natural frequency of the pump is calculated as well as its performance as a function of the driving frequency. The effect of the deviation of the driving frequency from the natural frequency on the pump performances is clearly shown. Also, it is demonstrated that the effect of the liquid mass in the pump nozzles on the natural frequency of the system is very high owing to the high acceleration of the fluid in the nozzles. Comparison with experiments shows a very good agreement with a minimal number of adjusting parameters.
Aerodynamic Loss Characteristics of a Turbine Blade With Trailing Edge Coolant Ejection: Part 1—Effect of Cut-Back Length, Spanwise Rib Spacing, Free-Stream Reynolds Number, and Chordwise Rib Length on Discharge Coefficients
Authors: Uzol Oguz , Camci Cengiz , Glezer Boris
Published: July 2002

The internal fluid mechanics losses generated between the blade plenum chamber and a reference point located just downstream of the trailing edge are investigated for a turbine blade trailing edge cooling system. The discharge coefficient Cd is presented as a function of the free-stream Reynolds number, cut-back length, spanwise rib spacing, and chordwise rib length. The results are presented in a wide range of coolant to free-stream mass flow rate ratios. The losses from the cooling system show strong free-stream Reynolds number dependency, especially at low ejection rates, when they are correlated against the coolant to free-stream pressure ratio. However, when Cd is correlated against a coolant to free-stream mass flow rate ratio, the Reynolds number dependency is eliminated. The current data clearly show that internal viscous losses due to varying rib lengths do not differ significantly. The interaction of the external wall jet in the cutback region with the free-stream fluid is also a strong contributor to the losses. Since the discharge coefficients do not have Reynolds number dependency at high ejection rates, Cd experiments can be performed at a low free-stream Reynolds number. Running a discharge coefficient experiment at low Reynolds number (or even in still air) will sufficiently define the high blowing rate portion of the curve. This approach is extremely time efficient and economical in finding the worst possible Cd value for a given trailing edge coolant system.
CyberCut: An Internet-based CAD/CAM System
Authors: Ahn Sung H. , Sundararajan V. , Smith Charles , Kannan Balaji , D’Souza Roshan , Sun Ganping , Mohole Ashish , Wright Paul K. , Kim JaeHo , McMains Sara , Smith Jordan , Se´quin Carlo H.
Published: July 2002

“CyberCut™” is a testbed for an Internet-based CAD/CAM system. It was specifically designed to be a networked, automated system, with a seamless communication flow from a client-side designer to a server-side machining service. The creation of CyberCut required several new software modules. These include: a) a Web-based design tool in which Design-for-Manufacturing information and machining rules constrain the designer to manufacturable parts; b) a geometric representation called SIF-DSG, for unambiguous communication between the client-side designer and the server-side process planner; c) an automated process planning system with several sub-modules that convert an incoming design to a set of tool-paths for execution on a 3-axis CNC milling machine. Using this software-pipeline, a CyberCut service, modeled on the MOSIS service for VLSI chips, has been now been launched for limited student-use at a group of cooperating universities.
High-Resolution Three-Dimensional-pQCT Images Can Be an Adequate Basis for In-Vivo μFE Analysis of Bone
Authors: Pistoia W. , van Rietbergen B. , Laib A. , Ru¨egsegger P.
Published: July 2002

Micro-finite element (μFE) models based on high-resolution images have enabled the calculation of elastic properties of trabecular bone in vitro. Recently, techniques have been developed to image trabecular bone structure in vivo, albeit at a lesser resolution. The present work studies the usefulness of such in-vivo images for μFE analyses, by comparing their μFE results to those of models based on high-resolution micro-CT (μCT) images. Fifteen specimens obtained from human femoral heads were imaged first with a 3D-pQCT scanner at 165 μm resolution and a second time with a μCT scanner at 56 μm resolution. A third set of images with a resolution of 165 μm was created by downscaling the μCT measurements. The μFE models were created directly from these images. Orthotropic elastic properties and the average tissue von Mises stress of the specimens were calculated from six FE-analyses per specimen. The results of the 165 μm models were compared to those of the 56 μm model, which was taken as the reference model. The results calculated from the pQCT-based models, correlated excellent with those calculated from the reference model for both moduli R2>0.95 and for the average tissue von Mises stress R2>0.83. Results calculated from the downscaled micro-CT models correlated even better with those of the reference models (R2>0.99 for the moduli and R2>0.96 for the average von Mises stress). In the case of the 3D-pQCT based models, however, the slopes of the regression lines were less than one and had to be corrected. The prediction of the Poisson’s ratios was less accurate (R2>0.45 and R2>0.67) for the models based on 3D-pQCT and downscaled μCT images respectively). The fact that the results from the downscaled and original μCT images were nearly identical indicates that the need for a correction in the case of the 3D-pQCT measurements was not due to the voxel size of the images but due to a higher noise level and a lower contrast in these images, in combination with the application of a filtering procedure at 165 micron images. In summary: the results of μFE models based on in-vivo images of the 3D-pQCT can closely resemble those obtained from μFE models based on higher resolution μCT system.
Modeling Dynamic Electrical Resistance During Resistance Spot Welding
Authors: Wang S. C. , Wei P. S.
Published: July 2002

Dynamic electrical resistance during resistance spot welding has been quantitatively modeled and analyzed in this work. A determination of dynamic resistance is necessary for predicting the transport processes and monitoring the weld quality during resistance spot welding. In this study, dynamic resistance is obtained by taking the sum of temperature-dependent bulk resistance of the workpieces and contact resistances at the faying surface and electrode-workpiece interface within an effective area corresponding to the electrode tip where welding current primarily flows. A contact resistance is composed of constriction and film resistances, which are functions of hardness, temperature, electrode force, and surface conditions. The temperature is determined from the previous study in predicting unsteady, axisymmetric mass, momentum, heat, species transport, and magnetic field intensity with a mushy-zone phase change in workpieces, and temperature and magnetic fields in the electrodes of different geometries. The predicted nugget thickness and dynamic resistance versus time show quite good agreement with available experimental data. Excluding expulsion, the dynamic resistance curve can be divided into four stages. A rapid decrease of dynamic resistance in stage 1 is attributed to decreases in contact resistances at the faying surface and electrode-workpiece interface. In stage 2, the increase in dynamic resistance results from the primary increase of bulk resistance in the workpieces and an increase of the sum of contact resistances at the faying surface and electrode-workpiece interface. Dynamic resistance in stage 3 decreases, because increasing rate of bulk resistance in the workpieces and contact resistances decrease. In stage 4 the decrease of dynamic resistance is mainly due to the formation of the molten nugget at the faying surface. The molten nugget is found to occur in stage 4 rather than stage 2 or 3 as qualitatively proposed in the literature. The effects of different parameters on the dynamic resistance curve are also presented.
Impact Responses of the Flexed Human Knee Using a Deformable Impact Interface
Authors: Atkinson Patrick J. , Haut Roger C.
Published: July 2002

Blunt impact trauma to the patellofemoral joint during car accidents, sporting activities, and falls can produce a range of injuries to the knee joint, including gross bone fracture, soft tissue injury, and/or microinjuries to bone and soft tissue. Currently, the only well-established knee injury criterion applies to knee impacts suffered during car accidents. This criterion is based solely on the peak impact load delivered to seated cadavers having a single knee flexion angle. More recent studies, however, suggest that the injury potential, its location, and the characteristics of the damage are also a function of knee flexion angle and the stiffness of the impacting structure. For example, at low flexion angles, fractures of the distal patella are common with a rigid impact interface, while at high flexion angles splitting of the femoral condyles is more evident. Low stiffness impact surfaces have been previously shown to distribute impact loads over the anterior surface of the patella to help mitigate gross and microscopic injuries in the 90 deg flexed knee. The objective of the current study was to determine if a deformable impact interface would just as effectively mitigate gross and microscopic injuries to the knee at various flexion angles. Paired experiments were conducted on contralateral knees of 18 human cadavers at three flexion angles (60, 90, 120 deg). One knee was subjected to a fracture level impact experiment with a rigid impactor, and the opposite knee was impacted with a deformable interface (3.3 MPa crush strength honeycomb material) to the same load. This (deformable) impact interface was effective at mitigating gross bone fractures at approximately 5 kN at all flexion angles, but the frequency of split fracture of the femoral condyles may not have been significantly reduced at 120 deg flexion. On the other hand, this deformable interface was not effective in mitigating microscopic injuries observed for all knee flexion angles. These new data, in concert with the existing literature, suggest the chosen impact interface was not optimal for knee injury protection in that fracture and other minor injuries were still produced. For example, in 18 cadavers a total of 20 gross fractures and 20 subfracture injuries were produced with a rigid interface and 5 gross fractures and 21 subfracture injuries with the deformable interface selected for the current study. Additional studies will be needed to optimize the knee impact interface for protection against gross and microscopic injuries to the knee.
Successive Deposition of Metals in Solid Freeform Fabrication Processes, Part 1: Thermomechanical Models of Layers and Droplet Columns
Authors: Chin R. K. , Beuth J. L. , Amon C. H.
Published: July 2002

Solid Freeform Fabrication (SFF) processes allow the automated building of three-dimensional shapes by successively depositing material in layers. Residual stress-induced tolerance losses are principal concerns in using these processes to create functional parts. Thermomechanical models of temperatures and stresses are presented, which are relevant to controlling residual stress effects in SFF processes. Models are applied to a particular SFF process; however, insights and conclusions are applicable to a large number of related processes. The temporal evolution of temperatures and stresses is investigated at two levels of detail. The successive deposition of layers of material is investigated first using one-dimensional simulations, approximating the build-up of residual stress in a multi-layered part. The successive deposition of a column of molten metal droplets (a technique used to create thick layers) is then modeled using two-dimensional axisymmetric simulations. Insights are given into process changes that can minimize residual stress-related effects in manufactured parts, including part constraint and localized preheating near the point of deposition. Results for thermomechanical interactions between droplets deposited in a column provide the foundation for studying interactions between adjacently deposited droplets, which is addressed in Part 2.
Numerical Investigation of Swirling Flow in Annular Diffusers With a Rotating Hub Installed at the Exit of Hydraulic Machines
Authors: Kochevsky A. N.
Published: July 2002

A single sweep method for the solution of Navier-Stokes equations is used for numerical investigation of flow in annular diffusers formed by a cylindrical casing and a converging conical hub, with the presence of inlet swirl and/or hub rotation. It is shown that counter-swirlwise hub rotation prevents reverse flow from appearing. The paper discusses the efficiency characteristics of diffusers installed at the exit of hydraulic machines. It is shown that the energy losses in a diffuser and in a channel behind the diffuser become minimal in the presence of small inlet swirl in the opposite direction to hub rotation.
Relationship Between the External Force and the Specific Work of Fracture R for Steady-State Tearing and Peeling of Elastoplastic Materials
Authors: Liu J. H. , Atkins A. G. , Jeronimidis G.
Published: July 2002

A simple relationship is obtained between the external force F and the fracture toughness R for thin sheets in steady state elastoplastic combined tearing and peeling along self-similar paths. The relationship depends only on the material properties (E, σy, and α for an elastoplastic material with linear hardening) and strip cross section (B and H). An earlier analysis (which incorporates transient tearing and peeling) requires lengthy computations over the whole length of the strip. The present analysis avoids that complication. Experiments in steady-state agree with the theory.
Real-Time Observation of the Evolution of Contact Area Under Boundary Lubrication in Sliding Contact
Authors: Lo Sy-Wei , Tsai Sheng-Da
Published: July 2002

To study the evolution of asperity contact in the sliding contact, a new in situ observation system of sheet metal surface is built up. The workpiece is stationary so that the continuous deformation of a specific group of asperities can be traced. In the case of no strain rate in the substrate of workpiece, the experiments for various materials, roughness patterns, sliding velocities, and normal loads all show that the fractional contact area will increase from its initial state of pure flattening without shear stress, to a saturated value with sliding distance in different rates. The sliding velocity has minor influence on the variation of contact area for same sliding distance. The maximum increasing rate of the contact area is found in the case of medium load. In most cases, the increase in contact area takes place with simultaneously decreasing shear stress and pressure on the flattened asperity peak. The development of adhesive wear can be clearly observed in the case of high normal load and long sliding distance.
Friction Measurements of Ultra-Thin Carbon Overcoats in Air
Authors: McGuiggan P. M. , Hsu S. M. , Fong W. , Bogy D. , Bhatia C. S.
Published: July 2002

The friction force as a function of humidity was measured between thin carbon films coated onto mica surfaces. The friction force was found to be proportional to the area of contact. The shear stress at 0 percent, 33 percent, and 100 percent relative humidity was measured to be 26 MPa±5 MPa,12 MPa±2 MPa, and 5 MPa±0.5 MPa, respectively, and was independent of the applied pressure for pressures less than 20 MPa. Water acts as a lubricant decreasing the friction between the carbon surfaces. The shear stress at 0 percent relative humidity corresponds to the shear stress of a solid paraffin film, and suggests that the shear may be dominated by a thin organic film adsorbed from air, at least at the pressures less than 20 MPa and a velocity of 1 μm/s. At 100 percent relative humidity, the shear stress for carbon coated surfaces was about double that for mica surfaces, indicating a stronger influence of the water for the more hydrophilic mica surface than the more hydrophobic carbon surface. The friction between one uncoated mica and one carbon coated mica surface resulted in immediate damage and generation of wear debris.
Flow Boiling Heat Transfer From Plain and Microporous Coated Surfaces in Subcooled FC-72
Authors: Rainey K. N. , Li G. , You S. M.
Published: July 2002

The present research is an experimental study of subcooled flow boiling behavior using flat, microporous-enhanced square heater surfaces in pure FC-72. Two 1-cm2 copper surfaces, one highly polished (plain) and one microporous coated, were flush-mounted into a 12.7 mm square, horizontal flow channel. Testing was performed for fluid velocities ranging from 0.5 to 4 m/s (Reynolds numbers from 18,700 to 174,500) and pure subcooling levels from 4 to 20 K. Results showed both surfaces’ nucleate flow boiling curves collapsed to one line showing insensitivity to fluid velocity and subcooling. The log-log slope of the microporous surface nucleate boiling curves was lower than the plain surface due to the conductive thermal resistance of the microporous coating layer. Both, increased fluid velocity and subcooling, increase the CHF values for both surfaces, however, the already enhanced boiling characteristics of the microporous coating appear dominant and require higher fluid velocities to provide additional enhancement of CHF to the microporous surface.
Film Cooling Discharge Coefficient Measurements in a Turbulated Passage With Internal Crossflow
Authors: Bunker Ronald S. , Bailey Jeremy C.
Published: July 2002

Gas turbine blades utilize internal geometry such as turbulator ribs for improved cooling. In some designs it may be desirable to benefit from the internal cooling enhancement of ribs as well as external film cooling. An experimental study has been performed to investigate the effect of turbulator rib placement on film hole discharge coefficient. In the study, a square passage having a hydraulic diameter of 1.27 cm is used to feed a single angled film jet. The film hole angle to the surface is 30 deg and the hole length-to-diameter ratio is 4. Turbulators were placed in one of three positions: upstream of film hole inlet, downstream of film hole inlet, and with the film hole inlet centered between turbulators. For each case 90 deg turbulators with a passage blockage of 15 percent and a pitch to height ratio of 10 were used. Tests were run varying film hole-to-crossflow orientation as 30, 90, and 180 deg, pressure ratio from 1.02 to 1.8, and channel crossflow velocity from Mach 0 to 0.3. Film hole flow is captured in a static plenum with no external crossflow. Experimental results of film discharge coefficients for the turbulated cases and for a baseline smooth passage are presented. Alignment of the film hole entry with respect to the turbulator is shown to have a substantial effect on the resulting discharge coefficients. Depending on the relative alignment and flow direction discharge coefficients can be increased or decreased 5–20 percent from the nonturbulated case, and in the worst instance experience a decrease of as much as 50 percent.
Distortion in Thermal Field Around Inserted Thermocouples in Experimental Interfacial Studies, Part 4: End Effect
Authors: Attia M. H. , Cameron A. , Kops L.
Published: July 2002

The main objective of this investigation is to develop a model for predicting the systematic temperature measurement error due to the thermal disturbance in the region surrounding the thermocouple hot junction. A parametric finite element analysis has been conducted to model the general case of a three-dimensional thermocouple installation inserted in a blind hole. The variables considered in this study are the level of the heat flux in the measurement zone, as well as the thermal characteristics of the thermocouple wires, the filler material (cement), and the solid material in which the installation is placed. Analysis of the results showed that the pattern of the disturbed temperature field around the thermocouple sensing element is critically dependent on the ratio between the thermal conductivities of the filler material and the solid material. The results also showed that a reduction in the temperature gradient in the undisturbed field results in a considerable increase in the partial heat flow into the thermocouple wires, and consequently a significant systematic temperature measurement error. The effect of the eccentric positioning of the thermocouple on the uncertainty limits of the measurement error was found to be quite significant. A generalized model is presented to estimate the measurement error for any combination of the thermocouple installation attributes. Experimental verification of some aspects of this analysis has been carried out using a well-controlled experiment in which the thermocouple hole is scale-modelled. Comparison of the test results with the finite element predictions confirmed the accuracy and validity of the numerical modelling and results.
Dynamic Segmentation and Incremental Editing of Boundary Representations in a Collaborative Design Environment
Authors: Wu Di , Sarma Radha
Published: July 2002

Currently boundary representations (b-reps) are a convenient means to exchange solid models between applications (e.g., design, manufacturing, inspection) in a distributed/collaborative design environment. There are two widely used approaches that help maintain the consistency of b-reps between applications, e.g., when a b-rep is modified in one application and needs to be updated in the other. One approach involves using a common database of b-reps where consistency is automatically guaranteed. The other approach involves using a repeated transfer of the entire b-rep using ftp-like protocols. The former results in a system that is not truly distributed and the latter results in consuming large amounts of network bandwidth and unacceptable latencies. This paper seeks to alleviate the abovementioned disadvantages by introducing a scheme for the incremental exchange of b-reps (i.e., for incrementally updating a pre-edit model to be consistent with the post-edit model) between applications in a collaborative design environment. The significance of this work is that only parts of b-reps (not the complete b-rep), which have been edited, need be transferred to update b-reps at distributed locations thereby reducing network bottlenecks during collaborative design activities.
Experimental Investigation of Polymeric Material Removal by Low Diffraction Laser Beam
Authors: Lu Xuanhui , Yao Y. Lawrence , Chen Kai
Published: July 2002

Effects of improved beam quality of a low diffraction laser beam on laser material removal processes are experimentally investigated in a polymeric material. The experimental results are in agreement with theoretical predictions. The results show that the low diffraction beam has marked advantages over the Gaussian beam in ablation-dominated material removal processes in terms of larger depth and smaller taper at the same average power level.
Interfacial Versus Cohesive Failure on Polymer-Metal Interfaces in Electronic Packaging—Effects of Interface Roughness
Authors: Yao Qizhou , Qu Jianmin
Published: July 2002

Debonding of polymer-metal interfaces often involves both interfacial and cohesive failure. Since the cohesive strength of polymers is usually much greater than the polymer-metal interfacial strength, cohesive failure near the interface is usually desired for enhancing the interfacial adhesion. Roughened surfaces generally produce more cohesive failure; therefore, they are used commonly in practice to obtain better adhesion. This paper develops a fracture mechanics model that can be used to quantitatively predict the amount of cohesive failure once the surface roughness data are given. An epoxy/Al interface was investigated using this fracture mechanics model. The predicted amount of cohesive failure as a function of surface roughness compares very well with the experimentally measured values. It is believed that this model can be extended to other polymer–metal interfaces. Contributed by the Electronic and Photonic Packaging Division for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received by the EPPD.
Design and Validation of a Machine for Reproducible Precision Insertion of Femoral Hip Prostheses for Preclinical Testing
Authors: Maher, S. A. , Prendergast, P. J. , Reid, and A. J. , Waide D. V. , Toni A.
Published: July 2002

Preclinical testing of orthopaedic implants is becoming increasingly important to eliminate inferior designs before animal experiments or clinical trials are begun. Preclinical tests can include both laboratory bench tests and computational modeling. One problem with bench tests is that variability in prosthesis insertion can significantly influence the failure rate; this makes comparison of prostheses more difficult. To solve this problem an insertion method is required that is both accurate and reproducible. In this work, a general approach to the insertion of hip prostheses into femoral bones is proposed based on physically replicating an insertion path determined using computer animation. As a first step, the seated prosthesis position is determined from templates and femur radiographs. Three-dimensional images of the prosthesis and bone are then imported into computer animation software and an insertion path in the coronal plane is determined. The insertion path is used to determine the profile of a cam. By attaching the prosthesis to a carriage, which is pneumatically moved along this cam, the required insertion motion of the prosthesis in the coronal plane can be achieved. This paper describes the design and validation of the insertion machine. For the validation study, a nonsymmetric hip prosthesis design (Lubinus SPII, Waldemar Link, Germany) is used. It is shown that the insertion machine has sufficient accuracy and reproducibility for preclinical mechanical testing. [S0148-0731(00)00602-6]
Hybrid Particle-Element Bond Graphs for Impact Dynamics Simulation
Authors: Fahrenthold E. P. , Koo J. C.
Published: July 2002

Particle methods offer an efficient modeling approach to number of impact dynamics problems not well suited to conventional Eulerian finite difference or Lagrangian finite element methods. Unfortunately, the most popular of these particle methods (smooth particle hydrodynamics) exhibits important deficiencies, in part related to its treatment of boundaries and interparticle tension, and suffers from a rather ad hoc model formulation approach. A hybrid particle-element kinematic scheme and an energy-based, bond graph modeling approach have been combined to produce a new impact dynamics simulation method, free of many problems which have hindered the effective application of various particle and continuum methods. [S0022-0434(00)00602-X]
Transport Coordinate (TC) Method for the Dynamics of Multiple Materials
Authors: Jia Wei
Published: July 2002

In this paper, we propose a new idea of tracking material interface. Since the regions filled with different materials at the initial time are merely transported by the velocity field, the material type at present is determined by its original location. We introduce the advection equation of the base coordinates to specify the material type, and solve this equation in the Euler framework. Thanks to the initial linear distribution, this method is free of numerical diffusion for the problems with a constant or a rigid body rotation velocity field and can produce accurate results for the general case. Moreover, it is applicable to the advection function of arbitrary distribution, for example, problems with more than two types of fluids. The new method is incorporated into a newly developed flow solver employing the semi-Lagrangian model to successfully solve the flow problems with multiple types of fluids. [S0098-2202(00)02001-0]
Initial Estimates in the Design of Rack-and-Pinion Steering Linkages
Authors: Simionescu P. A. , Smith M. R.
Published: July 2002

Based on recent results concerning the occurrence of function cognates in Watt II linkages, it is shown that only 3 geometric parameters are sufficient for defining the kinematic function of simplified planar rack-and-pinion steering linkages. The steering performances of the mechanisms are analytically expressed in terms of these parameters and, by employing an optimization-based synthesis method involving increasing the degree of freedom of the mechanism, the optimum domains are determined. The parameter sets corresponding to these minimum steering error domains are displayed in design charts. These charts aid the automotive engineer in the early stages of conceiving a new steering linkage by providing initial estimates of the basic geometry of the mechanism. They also provide information on two other characteristics of concern, i.e. the minimum pressure angle occurring in the joints and the rack stroke required for maximum turn of the wheels. [S1050-0472(00)00402-5]
Laser Array/EMAT Ultrasonic Measurement of the Penetration Depth in a Liquid Weld Pool
Authors: Graham G. M. , Ume I. Charles , Hopko S. N.
Published: July 2002

Ultrasonics has become widespread as a nondestructive testing technique. The most commonly used device for generation and reception of ultrasound are contacting piezo-electric transducers. Because these devices require physical coupling with the sample, test specimens must be stationary, and surfaces both cool and nonabrasive. Obviously, traditional contacting transducers cannot be used for real-time evaluation of certain manufacturing operations, such as weld quality control, where the test specimen could be in motion, and hot as well. This paper presents an evaluation of a noncontacting ultrasonic testing system consisting of a laser and fiber optic probe for generating ultrasound and an electromagnetic acoustic transducer for receiving the signals. This system has been applied to simulated liquid welds to demonstrate the feasibility of using similar equipment for real-time weld quality control. Weld penetration depth is investigated. [S1087-1357(00)70701-5]
Analysis of a Hydrodynamic Herringbone Grooved Journal Bearing Considering Cavitation
Authors: Jang G. H. , Chang D. I.
Published: July 2002

The Reynolds equation, incorporating Elrod’s cavitaton algorithm, is discretized on a rectangular grid in computational space through coordinate mapping in order to accurately analyze a herringbone grooved journal bearing of a spindle motor in a computer hard disk drive. The pressure distribution and cavitation area are determined by using the finite volume method. Predicted results are compared to experimental data of previous researchers. It was found that positive pressure is developed within the converging section of the bearing and that a cavity occurs in the diverging section. Cavitation has been neglected in the previous analyses of the herringbone grooved bearing. Load capacity and bearing torque are increased due to the increase of eccentricity and L/D and the decrease of the groove width ratio. The maximum load capacity was found to occur at a groove angle of 30 degrees while bearing torque remains constant due to the variation of the groove angle. The cavitation region is significantly decreased with the inclusion of herringbone grooves. However, the region increases with the increase of the eccentricity, L/D, groove angle and the rotational speed and the decrease of the groove width ratio. [S0742-4787(00)01401-6]
Dynamic Force Coefficients of a Multiple-Blade, Multiple-Pocket Gas Damper Seal: Test Results and Predictions
Authors: Li Jiming , Aguilar Ramon , Andre´s Luis San , Vance John M.
Published: July 2002

Experimental rotordynamic force coefficients and leakage for a four-blade, two-four pocket gas damper seal are presented and compared to predictions based on a one control volume bulk-flow model. The test rig comprises a vertical shaft and a test seal housing and flexible structure suspended from a rigid centering frame. The experiments were conducted at increasing rotor speeds to 6000 rpm and inlet/exit pressure ratios from 1.0 to 3.0. The seal force coefficients are obtained from impact response measurements of the seal and flexible structure using a frequency domain parameter identification technique. Both measurements and predictions show the seal direct stiffness and damping coefficients are proportional to the inlet/exit pressure ratio and insensitive to rotor speed. The agreement between experimental results and analytical predictions is acceptable. Predicted cross-coupled stiffness coefficients are of small amplitude. However, the test results evidence cross-coupled stiffnesses without journal rotation due to a structural asymmetry induced by the external pressurization into the seal. [S0742-4787(00)04201-6]
Performance Improvement Under Boundary Lubrication Conditions Using Slider Bearings With Silicon Nitride/Steel in High Torque Hydraulic Motors
Authors: Isaksson O. , Larker R.
Published: July 2002

The influence of materials and surface topography on static and dynamic coefficients of friction was experimentally investigated in a test apparatus under boundary and mixed lubrication conditions. Specimen materials were gray iron and silicon nitride Si3N4 of different surface topographies, sliding against chromium steel at a maximum Hertzian line contact pressure of 50 MPa. The lubricant was a standard mineral-based hydraulic fluid (ISO VG 68) held at +40°C or −28°C. The static and dynamic coefficients of friction under boundary lubrication conditions were both significantly reduced by the change from grey iron to silicon nitride as sliding material against Cr-steel, while the lowest static friction with Si3N4 was found for an intermediate surface roughness. [S0742-4787(00)04601-4]
Containment Inservice Inspection, Repair, Replacement, and Testing
Authors: Sammataro Robert F.
Published: July 2002

Section XI, Subsections IWE and IWL, of the ASME Boiler and Pressure Vessel Code provide requirements to assure that the critical areas of steel and concrete primary containment structures are inspected to detect degradation that could compromise structural and leak-tight integrity. They also specify requirements for preservice examination, acceptance standards, repairs, replacements, and pressure testing. Each nuclear utility in the United States is required to develop and implement a containment inservice inspection program by September 9, 2001, 5 yr after the initial approval in Title 10, Part 50, of the U.S. Code of Federal Regulations. This paper discusses the Code requirements and also provides an insight into the development process and philosophy for containment inservice inspection. [S0094-9930(00)01903-X]
Highly Oriented Pyrolytic Graphite by Core Level and Valence Band XPS
Authors: Xie Yaoming , Sherwood Peter M. A.
Published: July 2002

Both core level and valence band XPS spectra were obtained from a Union Carbide highly oriented pyrolytic graphite (HOPG) monochromator sample. Compared to Du Pont and Amoco pitch-based carbon fibers with different modulus and some PAN-based carbon fibers, the HOPG had much less oxygen components on the surface than the carbon fibers, except Du Pont E-120 high modulus pitch-based carbon fiber. [See Y. Xie and P. M. A. Sherwood, Appl. Spectrosc. 43, 1153 (1989); Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Spectrosc. 44, 797 (1990); Chem. Mater. 3, 164 (1991); Appl. Spectrosc. 44, 1621 (1990); 45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. A. Sherwood, ibid. 46, 645 (1992).] No nitrogen was found on the HOPG surface, nor on any of the pitch-based carbon fibers measured in our laboratory, but nitrogen was shown in all the PAN-based carbon fibers. Our previously reported work [Y. Xie and P. M. A. Sherwood, Chem. Mater. 1, 427 (1989); 2, 293 (1990); Appl. Spectrosc. 44, 797 (1990); Chem. Mater. 3, 164 (1991); Appl. Spectrosc. 44, 1621 (1990); 45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. A. Sherwood, ibid. 46, 645 (1992)] showed that XPS valence band spectra were more sensitive to chemical environment on the carbon fiber surface than core level spectra and could be well interpreted by X–α calculations with model compounds. Although both HOPG and E-120 samples had little oxygen on their surfaces (with E-120 even less), the valence band spectra of these two samples showed that the oxygen species in the HOPG surface and E-120 fiber surface were different because the separations between the O 2s peak and the C 2s peak in the two spectra are different.
Ni0.44Cu0.55 Alloy by XPS
Authors: Jansson Christian , Tougaard Sven
Published: July 2002

The results of x-ray photoelectron spectroscopy analysis of a CuNi alloy after a 2 keV Ar+ ion bombardment are presented. The spectra, covering the range of 200–1270 eV, include both the data as collected, and after correction for the analyzer response function. Quantification is given after application of the Tougaard background correction both with and without use of reference spectra. The alloy is found to be Cu depleted in the surface region which is consistent with previous works [T. Koshikawa, K. Goto, N. Saeki, R. Shimizu, and E. Sugata, Surf. Sci. 79, 461 (1979)].
The Semiconducting Tetragonal Phase of YBa2Cu3O6+x by XPS
Authors: Vasquez Richard P. , Foote Marc C. , Hunt Brian D.
Published: July 2002

X-ray photoemission spectra from an epitaxial thin film of the tetragonal semiconducting phase of YBa2Cu3O6+x which has been chemically etched in Br2/ethanol are presented. These data are useful for comparison to the orthorhombic superconducting phase.
Sputter-etched Silicon Carbide by AES
Authors: Epp June M.
Published: July 2002

The Auger electron spectra for sputter-etched silicon carbide are presented. The first derivative C KLL Auger electron spectrum of a crystalline carbide exhibits a peak shape different from that of adventitious hydrocarbon. The peak shape of the C KLL spectrum for a carbide such as TaC contains three components present at the approximate kinetic energies of 250, 260, and 270 eV, with the peak at 270 eV having a greater intensity in the positive direction than the C KLL spectrum for adventitious hydrocarbon. The shape of the differentiated C KLL Auger peak for sputtered SiC exhibits its own unique shape and is characteristically different from adventitious hydrocarbon, graphite, and the other metal carbides.
High Resolution Spectra of Hexatriacontane and Polyethylene
Authors: Thomas Elizabeth , Lawson Catherine S. , Tielsch Brian J. , Fulghum Julia E.
Published: July 2002

The C 1s photoelectron spectra are compared for the aliphatic hydrocarbons, hexatriacontane and polyethylene. An asymmetric C 1s envelope is observed regardless of sample form.
Second Row Transition Metals by AES
Authors: Hirsch Edward A. , Ray M. A. , Duarte Jorge
Published: July 2002

AES spectra were obtained from elements of the second row of the transition metals using a Perkin Elmer PHI 660 Scanning Auger Microprobe. Auger spectra were taken from Ag, Cd, In, Mo, Nb, Pd, Rh, Sb, Sn, Y, Zr, and Ru samples under identical conditions. Each elemental spectrum was obtained with electron beam energies of 3, 5, 10, and 20 keV using a 1 μA beam current. These parameters yield spectra which could easily be obtained under normal operating conditions (for comparison). These conditions are easily obtained by other instruments. The Cu sample was also used to obtain data used in calculating the signal-to-noise ratio. The ratio was obtained using the primary Cu KLL peak located at 919 eV. The instrumental energy resolution used for all of these measurements was 0.61% ± 0.008% measured with a 3 keV backscattered peak.
Analysis of Poly(methyl methacrylate) (PMMA) by XPS
Authors: Girardeaux Christophe , Pireaux Jean-Jacques
Published: July 2002

We report x-ray photoemission spectra of poly(methyl methacrylate) (PMMA). XPS spectra were measured with the SSI, SSX-100 model, using monochromated Al Kα x-rays. We present the survey spectrum (binding energy range of 0–1100 eV) and narrow spectra of C 1s and O 1s. The polymer is used as a reference to study the influence of PMMA surface modification by rf plasma for biochemical applications.
Potassium Chromate by XPS
Authors: Epling William S. , Hoflund Gar B. , Minahan David M.
Published: July 2002

XPS data were collected from a pressed potassium chromate powder. The spectra obtained from the as-received powder indicate that single states of K, Cr, and O are present due to K2CrO4. A small amount of C contamination is present in hydrocarbon and carbide forms. Therefore these data can be considered to be characteristic of K2CrO4.
Characterization of Perfluorinated Polyether (PFPE) Disk Drive Lubricants
Authors: Augustine B. H. , Bryson C. E. , Vasilyev L. A.
Published: July 2002

We report the XPS characterization of perfluorinated polyether (PFPE) samples used as lubricants for magnetic disk drive heads. Survey and high resolution C, O, and F spectra were obtained for eight different polyether formulations using a monochromatic AlKα source. Sample charging was evident in the samples, and was minimized throughout by the use of thin films of the samples and data collection under a metallic screen.
Analysis of a 30% Glass-filled Poly(butylene terephthalate) Polymer by XPS
Authors: Lannon John M. , Meng Qingru
Published: July 2002

We report x-ray photoemission spectra for a 30% glass-filled poly(butylene terephthalate) (PBT) polymer. XPS spectra were acquired with a SSI model SSX-100 instrument using monochromated Al Kα x-rays. We present the survey spectrum (binding energy 0–1000 eV) and a narrow spectrum of the C 1s and O 1s photoelectron peaks.
Analysis of a 15% Glass-filled Acrylonitrile Butadiene Styrene Polymer by XPS
Authors: Lannon John M. , Meng Qingru
Published: July 2002

We report x-ray photoemission spectra for a 15% glass-filled acrylonitrile butadiene styrene (ABS) polymer. XPS spectra were acquired with a SSI model SSX-100 instrument, using monochromated Al Kα x-rays. We present the survey spectrum (binding energy 0–1000 eV) and a narrow spectrum of the C 1s, O 1s, and N 1s photoelectron peaks.
Soft X-ray Photoemission From Heusler Alloys
Authors: Crapper M. D. , Brown D.
Published: July 2002

Synchrotron radiation based measurements of the soft x-ray photoemission spectrum of the valence band of Pd2MnSn, Co2MnSn, and Cu2MnAl are presented. The focus is on the Cooper minimum effect in Pd2MnSn and on the Mn 3p-3d resonance in all three. Heusler alloys are magnetic alloys with localized moments on the Mn atoms.
Electron Spectroscopic Data of La1−
x
Sr
x
MnO3 and La1−
x
Sr
x
CoO3
Authors: Sarma D. D. , Topwal Dinesh , Chainani A.
Published: July 2002

We report various high-energy electron spectroscopic data on sintered polycrystalline La1−xSrxMnO3 and La1−xSrxCoO3 with x=0.0, 0.1, 0.2, 0.3, and 0.4. The data presented consist of x-ray photoelectron transition metal 2p core level and valence band spectra, x-ray initiated transition metal L3VV spectra, Bremsstrahlung isochromat spectra, and soft x-ray absorption spectra at the oxygen K-edge. Substitution of trivalent La with divalent Sr introduces holes into the system, driving an insulator-to-metal transition along with magnetic transitions. The spectral changes with progressive hole doping reflect the evolution of electronic structure across the phase transition.
Strontium-doped Lanthanum Cobalt Oxides Studied by XPS
Authors: Saitoh T. , Mizokawa T. , Fujimori A. , Takeda Y. , Takano M.
Published: July 2002

La1−xSrxCoO3 is a perovskite-type magnetic material. LaCoO3 is a nonmagnetic semiconductor at low temperatures but it undergoes a gradual transition from the nonmagnetic ground state to a paramagnetic state above ∼90 K and then to a metal above ∼500 K. It has remained controversial whether the 90 K transition is a low spin-to-high spin transition or not. One aim of this research was to elucidate the origin of the magnetic transition and our conclusion was that it is not a low spin-to-high spin transition, but low spin-to-intermediate spin transition. By replacing La with Sr, the system changes from the nonmagnetic semiconductor to a ferromagnetic metal with increasing Sr concentration. This is similar to the colossal magnetoresistance (CMR) system La1−xSrxMnO3, and the system shows fairly large MR, in fact. However, in contrast to the manganese system, the present system shows only about a half of the full moment of the high spin Co ion. The other aim of this research was to understand the magnetic state of this system using photoemission spectroscopy. The samples were polycrystalline and were prepared by solid-state reaction. XPS measurements were carried out using Mg Kα source at liquid nitrogen temperature (∼80 K). In order to obtain a fresh clean surface, the samples were scraped with a diamond file in situ, and surface aging was monitored by observing the intensity of a tail at the higher binding-energy side of the O 1s peak. The surface typically lasted for 1–2 h.
Sensitivity studies of silicon etching in chlorine/argon plasmas
Authors: Kleditzsch S. , Riedel U.
Published: July 2002

In this article a well-stirred reactor model is utilized to model the etching of silicon in low-pressure chlorine/argon plasmas. Well-stirred reactor models are increasingly common in the literature due to their low requirements of computer resources for detailed chemical kinetics calculations. The model predicts the spatially averaged species composition and etch rate in a plasma etch reactor by solving conservation equations for species, mass, and the electron energy distribution function (EEDF). The reactor is characterized by a chamber volume, surface area, surface area fraction of the wafer, mass flow, pressure, power deposition, and composition of the feed gas. In such plasma etch models, assumptions on the EEDF which are needed to determine reaction rate coefficients for electron-impact reactions, are crucial for a prediction of steady state conditions. The model presented in a recent article [P. Ahlrichs, U. Riedel, and J. Warnatz, J. Vac. Sci. Technol. A 16, 1560 (1998)] is extended to describe the etching of the wafer with a special set of reactions occurring on a certain area fraction of the total reactor surface. A modified numerical procedure to solve the species conservation equations and the EEDF is presented, which needs considerably less computation time than the approach previously taken. Systematic sensitivity studies are presented to identify the connection between input parameters, outflow composition, and etch rate of the process. Such numerical studies are an important step towards fault detection and model based process control of plasma reactors.