bluuebunny/crossref_metadata_2025 huggingface dataset:
A Computational Model of a Power Plant Steam Condenser
Authors: Roy R. P. , Ratisher M. , Gokhale V. K.
Published: July 2002

A computational model of a power plant steam condenser which incorporates the effects of air in-leakage and removal on the performance of the condenser is reported. The condenser interior space is modeled as a porous medium. A quasi-three-dimensional approach is taken in which the steady-state steady-flow conservation equations for the steam-air mixture mass, momentum, thermal energy, and air mass fraction are solved for a series of two-dimensional grids perpendicular to the circulating water flow direction. The air removal system is explicitly modeled. The computational model is used to calculate the performance of the steam condenser of a 750-MWe unit at 100 percent load. Some of the calculated variables are compared with measurements obtained in the condenser. The effects of changing various operating parameters on the condenser performance at 100 percent load are also studied.
Tribology in Metal Cutting—Some Thermal Issues
Authors: Komanduri R. , Hou Z. B.
Published: July 2002

This paper addresses two fundamental thermal issues of tribology in orthogonal machining with a sharp tool, namely, the nature of the apparent heat partition in the shear plane and the variable heat partition at the chip-tool interface. A new model for the shear plane heat source was developed which does not require any assumption regarding the heat partition fraction a priori. Instead, this information is obtained as part of the solution. Similarly, a functional analysis approach was developed to determine the variable heat partition and the temperature distribution at the chip-tool interface due to the frictional heat source. The distribution of temperature in the chip, the tool, and the work material was determined analytically considering the combined effect of these two heat sources in orthogonal machining. The new analytical model was verified for a wide range of Peclet numbers, NPe (0.5–40) using the available experimental data from the literature.
Engineering Information Management to Support Enterprise Business Processes
Authors: Rangan Ravi M. , Chadha Bipin
Published: July 2002

Product definition information drives many business processes, yet its management at a coarse level (documents and files) precludes efficient automation and decision support. Information management at finer levels of granularity realizes the full potential of computable representations. This paper presents an industry oriented perspective of engineering information management (EIM) technologies and implementations and offers classifications of information systems as it relates to EIM systems and business processes. The concept of structured business objects that encapsulate the information and business-process definition at appropriate levels of granularity to support enterprise process dynamics is introduced. This provides a key construct to model the unique, and sometimes opposing, process perspectives within the enterprise. The paper then discusses key EIM and integration issues and future directions.
On the Exact Representation of the Boundary Surfaces of the Swept Volume of a Cylinder Undergoing Rational Be´zier and B-Spline Motions
Authors: Xia J. , Ge Q. J.
Published: July 2002

This paper develops methods for the exact analysis and representation of the swept volume of a circular cylinder undergoing rational Be´zier and B-spline motions. Instead of following the traditional approach of analyzing the point trajectory of an object motion for swept volume analysis, this paper develops a new method for swept volume analysis by studying the plane trajectory of a rational motion. It brings together recent work in swept volume analysis, plane representation of developable surfaces, as well as computer aided synthesis of freeform rational motions. The results have applications in design and approximation of freeform surfaces as well as tool path planning for 5-axis machining of freeform surfaces.
Robust Design of Families of Products With Production Modeling and Evaluation
Authors: Hernandez Gabriel , Allen Janet K. , Woodruff G. W. , Simpson Timothy W. , Bascaran Eduardo , Avila Luis F. , Salinas Fabian
Published: July 2002

The effectiveness of manufacturing enterprises that compete with product families can be leveraged through an appropriate standardization of components. In this paper we examine how a robust standardization of components can be implemented in the early stages of design with an explicit evaluation of the production system. The approach is based on (1) a mathematical formulation of design decisions using the Compromise Decision Support Problem (DSP), which includes robustness considerations, and (2) modeling production systems as networks of response surfaces. This modeling method facilitates evaluation of the impact of product design changes on the performance of the production system, thus enabling concurrent product-process design exploration. We demonstrate the approach with a case study, namely, the design of an absorber-evaporator module for a family of absorption chillers.
Fatigue of Chip Scale Package Interconnects Due to Cyclic Bending
Authors: Shetty S. , Lehtinen V. , Dasgupta A. , Halkola V. , Reinikainen T.
Published: July 2002

This study investigates the effect of quasi-static bending loads (strain rate=0.05/s) on the durability of 0.5 mm pitch Chip Scale Package (CSP) interconnects when assembled on FR4 substrates. The substrates have rows of CSPs and are subjected to three-point bending loads. Overstress curvature limits are experimentally determined and used to identify limits for zero-to-max cyclic bending loads. The test configuration is simulated using finite element modeling (FEM) and the total strain accumulated in the solder joints is estimated. Using the FEM model, a calibration curve is constructed to relate the cyclic curvature range in the substrate to the cyclic strain range in the critical solder joint. Bending moments along the substrate are estimated from the forces applied at the center of the board during the fatigue test. Strains measured on the substrate surface and the bending displacements measured at the center are used to estimate curvatures at different locations along the substrate. Using the calibration curve, the total strains in the solder joint are obtained for the applied loading. A strain-range fatigue damage model proposed by Coffin and Manson, is used to predict the cycles to failure for the applied loading. Predicted durability is compared to experimental measurements. Concave substrate curvature is found to be more damaging than convex curvature, for interconnect fatigue. Finite element simulations are repeated for life-cycle loading to predict acceleration factors. Using the acceleration factors, the product durability is estimated for life-cycle environments.
Entropies of Statistical Mechanics and Disorder Versus the Entropy of Thermodynamics and Order
Authors: Gyftopoulos Elias P.
Published: July 2002

The prevailing beliefs in the scientific and engineering literature are that: (i) thermodynamics is explained and justified by statistical mechanics; (ii) entropy is a statistical measure of disorder; and (iii) for given values of energy, volume, and amounts of constituents, the largest value of entropy corresponds to both a thermodynamic equilibrium state and the ultimate disorder. In this paper, we provide: (i) a summary of the beliefs as stated by some eminent scientists; (ii) experimental evidence that casts serious doubt about the validity of the beliefs; (iii) an outline of a nonstatistical unified quantum theory of mechanics and thermodynamics; (iv) an outline of a nonquantal, nonstatistical exposition of thermodynamics, valid for all systems (both macroscopic and microscopic), and for all states (both thermodynamic equilibrium and not thermodynamic equilibrium); (v) the definition and analytical expression of the entropy of thermodynamics; (vi) the interpretation of entropy as both a measure of the quantum-theoretic spatial shape of a molecule, and an indicator of order; and (vii) nonstatistical answers to the questions that motivated the introduction of statistical mechanics.
Adaptive Compensation of Sensor Runout for Magnetic Bearings With Uncertain Parameters: Theory and Experiments
Authors: Setiawan Joga D. , Mukherjee Ranjan , Maslen Eric H.
Published: July 2002

The problem of sensor runout in magnetic bearing systems has been largely overlooked due to similarities with mass unbalance in creating periodic disturbances. While the effect of mass unbalance can be significantly reduced, if not eliminated, through rotor balancing, sensor runout disturbance is unavoidable since it originates from physical nonconcentricity between rotor and stator. Sensor runout is also caused by nonuniform electrical and magnetic properties around the sensing surface. To improve performance of magnetic bearings, we present an adaptive algorithm for sensor runout compensation. It guarantees asymptotic stability of the rotor geometric center and on-line feedforward cancellation of runout disturbances using persistent excitation. Some of the advantages of our algorithm include simplicity of design and implementation, stability, and robustness to plant parameter uncertainties. The stability and robustness properties are derived from passivity of the closed-loop system. Numerical simulations are presented to demonstrate efficacy of the algorithm and experimental results confirm stability and robustness for large variation in plant parameters.
Linear and Nonlinear PSE for Stability Analysis of the Blasius Boundary Layer Using Compact Scheme
Authors: Esfahanian V. , Hejranfar K. , Sabetghadam F.
Published: July 2002

A highly accurate finite-difference PSE code has been developed to investigate the stability analysis of incompressible boundary layers over a flat plate. The PSE equations are derived in terms of primitive variables and are solved numerically by using compact method. In these formulations, both nonparallel as well as nonlinear effects are accounted for. The validity of present numerical scheme is demonstrated using spatial simulations of two cases; two-dimensional (linear and nonlinear) Tollmien-Schlichting wave propagation and three-dimensional subharmonic instability breakdown. The PSE solutions have been compared with previous numerical investigations and experimental results and show good agreement.
Sliding Control of Magnetic Bearing Systems
Authors: Yeh T.-J. , Chung Ying-Jer , Wu Wei-Chung
Published: July 2002

This paper proposes a sliding control scheme to deal with the nonlinear, uncertain dynamics of magnetic bearing systems. The controller is designed based on the Thevenin equivalent of a network model that characterizes both the main electromechanical interaction and the secondary electromagnetic effects such as flux leakage, fringing fluxes, and finite core permeance. The controller consists of two parts: the nominal control part that linearizes the nonlinear dynamics, and the robust control part that provides robust performance against the uncertainties. Because the unidirectionality of magnetic forces may render the control law ill-defined in some scenarios, a lemma is proved and can be used to select proper control parameters to guarantee the performance. Moreover, a control modification is also suggested in order to reduce the intensive control pulsation in the absence of gravity. The proposed control scheme is applied to the thrust bearing of a magnetically levitated rotor. Simulations and experiments indicate that the control system is capable of maintaining stability and consistent performance.
A Linear Viscoelastic Biphasic Model for Soft Tissues Based on the Theory of Porous Media
Authors: Ehlers Wolfgang , Markert Bernd
Published: July 2002

Based on the Theory of Porous Media (mixture theories extended by the concept of volume fractions), a model describing the mechanical behavior of hydrated soft tissues such as articular cartilage is presented. As usual, the tissue will be modeled as a materially incompressible binary medium of one linear viscoelastic porous solid skeleton saturated by a single viscous pore-fluid. The contribution of this paper is to combine a descriptive representation of the linear viscoelasticity law for the organic solid matrix with an efficient numerical treatment of the strongly coupled solid-fluid problem. Furthermore, deformation-dependent permeability effects are considered. Within the finite element method (FEM), the weak forms of the governing model equations are set up in a system of differential algebraic equations (DAE) in time. Thus, appropriate embedded error-controlled time integration methods can be applied that allow for a reliable and efficient numerical treatment of complex initial boundary-value problems. The applicability and the efficiency of the presented model are demonstrated within canonical, numerical examples, which reveal the influence of the intrinsic dissipation on the general behavior of hydrated soft tissues, exemplarily on articular cartilage.
Fast Transient Analysis for Locally Nonlinear Structures by Recursive Block Convolution
Authors: Gordis Joshua H. , Neta Beny
Published: July 2002

The transient analysis of large structural systems with localized nonlinearities is a computationally demanding process, inhibiting dynamic redesign and optimization. A previously developed integral equation formulation for transient structural synthesis has demonstrated the ability to solve large locally nonlinear transient problems in a fraction of the time required by traditional direct integration methods, with equivalent or better accuracy. A recursive block-by-block convolution algorithm is developed for the solution of the governing integral equation that further reduces the solution time required. A computing time comparison of single-block versus multiple-block solutions is provided.
Studying Contact Stress Fields Caused by Surface Tractions With a Discrete Convolution and Fast Fourier Transform Algorithm
Authors: Liu Shuangbiao , Wang Qian
Published: July 2002

The knowledge of contact stresses is critical to the design of a tribological element. It is necessary to keep improving contact models and develop efficient numerical methods for contact studies, particularly for the analysis involving coated bodies with rough surfaces. The fast Fourier Transform technique is likely to play an important role in contact analyses. It has been shown that the accuracy in an algorithm with the fast Fourier Transform is closely related to the convolution theorem employed. The algorithm of the discrete convolution and fast Fourier Transform, named the DC-FFT algorithm includes two routes of problem solving: DC-FFT/Influence coefficients/Green’s function for the cases with known Green’s functions and DC-FFT/Influence coefficient/conversion, if frequency response functions are known. This paper explores the method for the accurate conversion for influence coefficients from frequency response functions, further improves the DC-FFT algorithm, and applies this algorithm to analyze the contact stresses in an elastic body under pressure and shear tractions for high efficiency and accuracy. A set of general formulas of the frequency response function for the elastic field is derived and verified. Application examples are presented and discussed.
On Perturbation Solutions for Nearly Circular Inclusion Problems in Plane Thermoelasticity
Authors: Wang C.-H. , Chao C.-K.
Published: July 2002

An approximate analytical solution to the nearly circular inclusion problems of arbitrary shape in plane thermoelasticity is provided. The shape of the inclusion boundary considered in the present study is assumed to have the form r=a0[1+Aθ], where a0 is the radius of the unperturbed circle and Aθ is the radius perturbation magnitude that is represented by a Fourier series expansion. The proposed method in this study is based on the complex variable theory, analytical continuation theorem, and the boundary perturbation technique. Originating from the principle of superposition, the solution of the present problem is composed of the reference and the perturbation terms that the reference term is the known exact solution pertaining to the case with circular inclusion. First-order perturbation solutions of both temperature and stress fields are obtained explicitly for elastic inclusions of arbitrary shape. To demonstrate the derived general solutions, two typical examples including elliptical and smooth polygonal inclusions are discussed in detail. Compared to other existing approaches for elastic inclusion problems, our methodology presented here is remarked by its efficiency and applicability to inclusions of arbitrary shape in a plane under thermal load.
Application of a Fast-Stabilizing Frequency Domain Parameter Estimation Method
Authors: Van der Auweraer H. , Guillaume P. , Verboven P. , Vanlanduit S.
Published: July 2002

A new noniterative frequency domain parameter estimation technique is proposed. It is based on a weighted total least squares approach, starting from multiple input multiple output frequency response functions. One of the specific advantages of the technique lies in the very stable identification of the system poles as a function of the specified system order, leading to easy-to-interpret stabilization diagrams. This implies a potential for automating the method and to apply it to “difficult” estimation cases. Several real-life case studies are discussed, one related to holographic modal analysis in the medium frequency range, one to the modal testing of a fully trimmed vehicle.
Intersonic Crack Propagation—Part II: Suddenly Stopping Crack
Authors: Huang Y. , Gao H.
Published: July 2002

In Part I of this series, we have obtained the fundamental solution for a mode II intersonic crack which involves a crack moving uniformly at a velocity between the shear and longitudinal wave speeds while subjected to a pair of concentrated forces suddenly appearing at the crack tip and subsequently acting on the crack faces. The fundamental solution can be used to generate solutions for intersonic crack propagation under arbitrary initial equilibrium fields. In this paper, Part II of this series, we study a mode II crack suddenly stopping after propagating intersonically for a short time. The solution is obtained by superposing the fundamental solution and the auxiliary problem of a static crack emitting dynamic dislocations such that the relative crack face displacement in the fundamental solution is negated ahead of where the crack tip has stopped. We find that, after the crack stops moving, the stress intensity factor rapidly rises to a finite value and then starts to change gradually toward the equilibrium value for a static crack. A most interesting feature is that the static value of stress intensity is reached neither instantaneously like a suddenly stopping subsonic crack nor asymptotically like a suddenly stopping edge dislocation. Rather, the dynamic stress intensity factor changes continuously as the shear and Rayleigh waves catch up with the stopped crack tip from behind, approaches negative infinity when the Rayleigh wave arrives, and then suddenly assumes the equilibrium static value when all the waves have passed by. This study is an important step toward the study of intersonic crack propagation with arbitrary, nonuniform velocities.
Solution Structure and Stability of Viscous Flow in Curved Square Ducts
Authors: Yang Tianliang , Wang Liqiu
Published: July 2002

The bifurcation structure of viscous flow in curved square ducts is studied numerically and the stability of solutions on various solution branches is examined extensively. The solution structure of the flow is determined using the Euler-Newton continuation, the arc-length continuation, and the local parameterization continuation scheme. Test function and branch switch technique are used to monitor the bifurcation points in each continuation step and to switch branches. Up to 6 solution branches are found for the case of a flow in the curved square channel within the parameter range under consideration. Among them, three are new. The flow patterns on various bifurcation branches are also examined. A direct transient calculation is made to determine the stability of various solution branches. The results indicate that, within the scope of the present work, at given set of parameter values, the arbitrary initial disturbances lead all solutions to the same state. In addition to stable steady two-vortex solutions and temporally periodic solutions, intermittent and chaotic oscillations are discovered within a certain region of the parameter space. Temporal intermittency that is periodic for certain time intervals manifests itself by bursts of aperiodic oscillations of finite duration. After the burst, a new periodic phase starts, and so on. The intermittency serves as one of the routes for the onset of chaos. The results show that the chaotic flow in the curved channel develops through the intermittency. The chaotic oscillations appear when the number of bursts becomes large. The calculations also show that transient solutions on various bifurcation branches oscillate chaotically about the common equilibrium states at a high value of the dynamic parameter.
Fundamental Analysis on Rotor-Stator Interaction in a Diffuser Pump by Vortex Method
Authors: Wang H. , Tsukamoto H.
Published: July 2002

A two-dimensional unsteady flow was calculated within a whole stage of a diffuser pump to investigate pressure fluctuations due to the interaction between impeller and diffuser vanes by using the vortex method, in which vortices shedding from solid boundary were determined by the basic governing equation. The Petrov-Galerkin Method was applied to yield the solutions that satisfy the boundary conditions in an integral sense, and it improved the stability and accuracy of the numerical solutions greatly. A new scheme was also proposed to improve the unsteady pressure evaluation by a boundary integration method in the rotor-stator interaction problem. Moreover, for a more realistic prediction of the pressure fluctuations, the inlet flow was supposed to change with time so that pumping system may balance. The calculated time-varying flow rate, total hydraulic head rise and pressure fluctuations in the vaned diffuser passage, were compared with the measured and calculated ones by other methods. Calculated unsteady pressure fluctuations in the vaned diffuser passage showed good agreement with the experimental data and the CFD calculated ones.
Varying the Stiffness of a Beam-Like Neutralizer Under Fuzzy Logic Control
Authors: Kidner M. R. F. , Brennan M. J.
Published: July 2002

Vibration neutralizers are effective vibration control devices at a single frequency. If they can compensate for drift in the excitation frequency by adjusting their stiffness the performance can be improved, and the range of problems to which they can be applied is broadened. This paper considers a beam-like adaptive vibration neutralizer, and it is shown that the stiffness of the device and hence its natural frequency can be significantly altered by varying the beam cross-section. Several different beam configurations are investigated and the rate of change of stiffness as a function of beam separation is calculated for each configuration. The results are validated by some simple experiments. Real-time stiffness control of a beam-like tuneable neutralizer is also demonstrated both by computer simulation and experiment. The neutralizer is subjected to swept sine excitation over a six-second period and the tuned condition is maintained throughout the excitation period. The efficacy of using a nonlinear fuzzy logic controller is compared with the use of a simple proportional controller.
Dynamic Loading of Synchronous Belts
Authors: Johannesson Tomas , Distner Martin
Published: July 2002

In automotive timing belt drives friction history effects must be taken into concern due to rapidly changing loads. Here a spring based model capable of handling dynamic load conditions is presented. The model also covers partial meshing effects and utilizes Coulomb friction. The model shows good agreement with experimental data found in literature. It is proven that when simulating synchronous belt drives during rapidly changing load conditions, using models for quasi-static load conditions stepwise are not sufficient.
Robust Optimal Influence-Coefficient Control of Multiple-Plane Active Rotor Balancing Systems
Authors: Dyer Stephen W. , Shi Jianjun , Ni Jun , Shin Kwang-Keun
Published: July 2002

Rotating mass imbalance causes harmful vibration of high-speed machine tools, turbomachinery, etc. Constant speed, steady-state influence coefficient control allows active balancing systems to suppress this vibration if the influence matrix is estimated accurately. An optimal strategy for multiple-plane active balancing control is presented here that improves control robustness to modeling and estimation errors. The vibration controller objectively trades off residual vibration, control effort, and control rate of change. Penalizing control effort and rate of change is shown to enhance control stability margin, with certain performance trade-offs. Experimental results illustrate the improvement in control robustness compared with traditional weighted least squares optimal control.
Plasma Absorption of Femtosecond Laser Pulses in Dielectrics
Authors: Fan C. H. , Sun J. , Longtin J. P.
Published: July 2002

Dielectric (high bandgap) materials represent an important and diverse class of materials in micro and nanotechnology, including MEMS devices, biomedical and bioengineering systems, multilayer thin film coatings, fiber optics, etc. Micromachining dielectrics using ultrafast lasers is an exciting and promising new research area with many significant advantages, including precision material removal, negligible heating of the workpiece, micron and sub-micron-size feature fabrication, and high aspect ratio features. During ultrafast laser processing of dielectrics, the intense laser pulse ionizes the irradiated material and produces an optical breakdown region, or plasma, that is characterized by a high density of free electrons. These high-density electrons can efficiently absorb a large fraction of the laser irradiance energy, part of which will then be coupled into the bulk material, resulting in material removal through direct vaporization. The energy deposited into the material depends on the time and space-dependent breakdown region, the plasma rise time, and the plasma absorption coefficient. Higher coupling efficiency results in higher material removal rate; thus energy deposition is one of the most important issues for ultrafast laser materials processing, particularly for micron and sub-micron-scale laser materials processing. In the present work, a femtosecond breakdown model is developed to investigate energy deposition during ultrafast laser material interactions. One substantial contribution of the current work is that pulse propagation effects have been taken into account, which have been shown to become significant for pulse durations less than 10 ps. By accounting for the pulse propagation, the time and space-resolved plasma evolution can be characterized and used to determine the energy deposition through plasma absorption. With knowledge of the plasma absorption, changes in the pulse profile as it propagates in the focal region can be determined as well. Absorption of the laser pulse by plasma in water is compared with experimental data to validate the model, as water is a well characterized dielectric. The model, however, is also applicable to other transparent or moderately absorbing solid and liquid dielectric media during ultrafast laser-materials interactions.
Experimental and Numerical Investigation on the Influence of Process Speed on the Blanking Process
Authors: Goijaerts A. M. , Govaert L. E. , Baaijens F. P. T.
Published: July 2002

In a previous work a numerical tool was presented which accurately predicted both process force and fracture initiation for blanking of a ferritic stainless steel in various blanking geometries. This approach was based on the finite element method, employing a rate-independent elasto-plastic constitutive model combined with a fracture criterion which accounts for the complete loading history. In the present investigation this work is extended with respect to rate-dependence by employing an elasto-viscoplastic constitutive model in combination with the previously postulated fracture criterion for ferritic stainless steel. Numerical predictions are compared to experimental data over a large range of process speeds. The rate-dependence of the process force is significant and accurately captured by the numerical simulations at speeds ranging from 0.001 to 10 mm/s. Both experiments and numerical simulations show no influence of punch velocity on fracture initiation.
A Combined 3D Linear and Circular Interpolation Technique for Multi-Axis CNC Machining
Authors: Liang H. , Hong H. , Svoboda J.
Published: July 2002

In multi-axis CNC machining of sculptured surfaces, a linear interpolation technique has been used to generate the command signals for positions along the straight line segments that connect each consecutive data point. Due to the rotational movements superimposed on the translational movements in multi-axis CNC machining, the actual cutter contact (CC) point moves along a space curve path, while the linear interpolation technique generates positions along the straight line path. The nonlinear curve segments deviate from the linearly interpolated line segments resulting in nonlinearity errors, which in turn, commonly cause difficulties to ensure high precision machining. An interpolator design technique for solving the nonlinearity errors problem in multi-axis CNC machining is presented. A combined 3D linear and circular interpolation principle is developed on the basis of the 3D linear and circular interpolation principles. The new designed interpolator is capable of driving the rotation movement pivot along a predesigned 3D curve path, so that the CC point motion trajectory is via a straight line connecting machining data points. Therefore, the proposed interpolator design technique on-line eliminates nonlinearity errors, and provides a solution to the nonlinearity errors problem for multi-axis CNC machining.
Statistical Classification of Spectral Data for Laser Weld Quality Monitoring
Authors: Ali Afsar , Farson Dave
Published: July 2002

Signals from several sensors were employed for real-time laser weld quality monitoring. Sheet-metal butt-joint laser welds of three quality classes (full penetration, partial penetration, gapped) were produced in experimental trials. Optical, air-born acoustic and plasma charge signals acquired during welding were subsequently Fourier-transformed and the spectra were analyzed individually to determine relationships to laser weld quality. The frequency bands most highly correlated to weld quality were identified by stepwise linear discriminant analysis (LDA) of the spectra. Testing of the quality discriminators formulated by LDA of the spectral data showed that the acoustic signal was most reliably correlated with weld quality. Fusing the data from all three sensors prior to LDA analysis produced a discriminator that had about the same reliability as one based on acoustic data alone.
Seismic Proving Test of Equipment and Structures in Thermal Conventional Power Plant
Authors: Tazuke Hideyuki , Yamaguchi Satoru , Ishida Kazuo , Sakurai Tomoki , Akiyama Hiroshi , Chiba Toshio
Published: July 2002

The importance of ensuring uninterrupted electric power supply was reaffirmed on the occasion of the Hyogoken-Nanbu Earthquake in 1995, when the district was affected by extended power failure. The notice has been attached to the resistance of power generation facilities to severe earthquake. The seismic proving test of equipment and structures in thermal conventional power plant was conducted. Tests were performed to demonstrate the earthquake resistant property of the LNG tank and to verify the validity of the FEM analysis. It was adopted for analyzing lateral slipping and EFB. With the comprehensive evaluation of tests and analysis, the seismic capability of LNG tank was assessed.
Dynamic Compression Testing of Soft Materials
Authors: Chen W. , Lu F. , Frew D. J. , Forrestal M. J.
Published: July 2002

Low-strength and low-impedance materials pose significant challenges in the design of experiments to determine dynamic stress-strain responses. When these materials are tested with a conventional split Hopkinson pressure bar, the specimen will not deform homogeneously and the tests are not valid. To obtain valid data, the shape of the incident pulse and the specimen thickness must be designed such that the specimens are in dynamic equilibrium and deform homogeneously at constant strain rates. In addition, a sensitive transmission bar is required to detect the weak transmitted pulses. Experimental results show that homogeneous deformations at nearly constant strain rates can be achieved in materials with very low impedances, such as a silicone rubber and a polyurethane foam, with the experimental modifications presented in this study.
Advances in Parabolic Trough Solar Power Technology
Authors: Price Hank , Lu¨pfert Eckhard , Kearney David , Zarza Eduardo , Cohen Gilbert , Gee Randy , Mahoney Rod
Published: July 2002

Parabolic trough solar technology is the most proven and lowest cost large-scale solar power technology available today, primarily because of the nine large commercial-scale solar power plants that are operating in the California Mojave Desert. These plants, developed by Luz International Limited and referred to as Solar Electric Generating Systems (SEGS), range in size from 14–80 MW and represent 354 MW of installed electric generating capacity. More than 2,000,000m2 of parabolic trough collector technology has been operating daily for up to 18 years, and as the year 2001 ended, these plants had accumulated 127 years of operational experience. The Luz collector technology has demonstrated its ability to operate in a commercial power plant environment like no other solar technology in the world. Although no new plants have been built since 1990, significant advancements in collector and plant design have been made possible by the efforts of the SEGS plants operators, the parabolic trough industry, and solar research laboratories around the world. This paper reviews the current state of the art of parabolic trough solar power technology and describes the R&D efforts that are in progress to enhance this technology. The paper also shows how the economics of future parabolic trough solar power plants are expected to improve.
A Simple Model for Stable Cyclic Stress-Strain Relationship of Type 304 Stainless Steel Under Nonproportional Loading
Authors: Itoh Takamoto , Chen Xu , Nakagawa Toshimitsu , Sakane Masao
Published: July 2002

This paper proposes a simple two-surface model for cyclic incremental plasticity based on combined Mroz and Ziegler kinematic hardening rules under nonproportional loading. The model has only seven material constants and a nonproportional factor which describes the degree of additional hardening. Cyclic loading experiments with fourteen strain paths were conducted using Type 304 stainless steel. The simulation has shown that the model was precise enough to calculate the stable cyclic stress-strain relationship under nonproportional loadings. [S0094-4289(00)00101-8]
High Pressure Annular Two-Phase Flow in a Narrow Duct: Part II—Three-Field Modeling
Authors: Kumar Ranganathan , Trabold Thomas A.
Published: July 2002

This paper outlines the development of a three-field modeling approach in annular flow and the predictive capability of an analysis code. Models have been developed here or adapted from the literature for the thin film near the wall as well as the droplets in the vapor core, and have been locally applied in a fully developed, two-phase adiabatic boiling annular flow in a duct heated at the inlet at high pressure. Numerical results have been obtained using these models that are required for the closure of the continuity and momentum equations. The two-dimensional predictions are compared with local void fraction and droplet velocity (using a hot film anemometer), and average void fraction (using gamma densitometry) for a refrigerant fluid flowing in a narrow vertical duct with a cross-section aspect ratio of 22.5. Predicted results match the experimental data well for high void fraction annular flows, validating the overall modeling approach. [S0098-2202(00)01002-6]
Metallurgical Assessment of the Softened HAZ Region During Multipass Welding
Authors: Wojnowski D. , Oh Y. K. , Indacochea J. E.
Published: July 2002

CrMoV steels are used in high temperature and high stress sections of power plant members; their good creep resistance is impaired by welding done during fabrication of assemblies and weld repair of service damaged rotors. Occurrence of a “softening” (“tempered”) region in the grain refined heat-affected zone/intercritical heat-affected zone, has become the limiting factor in the life extension of weld repaired high pressure/intermediate pressure steam turbine rotors. This study focuses on the effect that multiple thermal cycles have on the development of this softened region. Work was conducted on real weldments and with simulated heat-affected zones produced with the Gleeble thermomechanical simulator and by isothermal furnace heat treatments. The thermal cycle at the softening region in the actual weldment was measured and reproduced during simulation; it was estimated that the peak temperature at this location was just above the intercritical A1 temperature. Softening occurred before any changes in microstructure could be detected with the light microscope. Carbide coarsening, shown by limited TEM analysis, and the likely dissolution of some of the carbides, most probable, contributed to reduce the microhardness values. [S1087-1357(00)70202-4]
Fast Methods for Solving Rough Contact Problems: A Comparative Study
Authors: Polonsky I. A. , Keer L. M.
Published: July 2002

A realistic description of rough surfaces will generally involve very large arrays of surface height data, which makes the application of conventional numerical methods of contact mechanics to rough contact analyses impractical. Recently, two fast numerical techniques have been applied to rough contact problems: the multi-level multi-summation (MLMS) and the fast Fourier transform (FFT). In this work, the computational efficiency of the two methods is compared by applying them to an example concentrated contact problem. It is shown that to achieve a numerical accuracy comparable to that of MLMS, the grid on which FFT is performed needs to be extended far beyond the contact area, which results in a dramatic increase in the computation time. When such a high accuracy is unnecessary. FFT can be applied on a smaller grid. However, the computational speed of MLMS can also be increased in this case by modifying certain algorithm parameters. Numerical results demonstrate that MLMS is more advantageous than FFT for solving three-dimensional concentrated contact problems, both when the maximum possible accuracy is desired and when a moderate accuracy goal is specified. [S0742-4787(00)00601-9]
An Asperity Microcontact Model Incorporating the Transition From Elastic Deformation to Fully Plastic Flow
Authors: Zhao Yongwu , Maietta David M. , Chang L.
Published: July 2002

This paper presents an elastic-plastic asperity microcontact model for contact between two nominally flat surfaces. The transition from elastic deformation to fully plastic flow of the contacting asperity is modeled based on contact-mechanics theories in conjunction with the continuity and smoothness of variables across different modes of deformation. The relations of the mean contact pressure and contact area of the asperity to its contact interference in the elastoplastic regime of deformation are respectively modeled by logarithmic and fourth-order polynomial functions. These asperity-scale equations are then used to develop the elastic-plastic contact model between two rough surfaces, allowing the mean surface separation and the real area of contact to be calculated as functions of the contact load and surface plasticity index. Results are presented for a wide range of contact load and plasticity index, showing the importance of accurately modeling the deformation in the elastoplastic transitional regime of the asperity contacts. The results are also compared with those calculated by the GW and CEB models, showing that the present model is more complete in describing the contact of rough surfaces. [S0742-4787(00)01201-7]
A Transient Thermoelastohydrodynamic Study of Steadily Loaded Plain Journal Bearings Using Finite Element Method Analysis
Authors: Kucinschi Bogdan-Radu , Fillon Michel , Fre^ne Jean , Pascovici Mircea D.
Published: July 2002

The present paper proposes an advanced bidimensional model necessary to calculate the temperature field in a journal bearing submitted to both rapid and slow start-ups. The model takes into account realistic thermal boundary conditions at fluid film-solid interfaces. The thermoelastic deformations of both the journal and of the bush are also considered and a special attention is paid to the ruptured zone of the film. The Finite Element Method (with upwind techniques whenever necessary) is employed to solve the equations implied by the model. Finally, the theoretical predictions were validated by comparison with experimental data. [S0742-4787(00)02701-6]
An Infrared Technique for Evaluating Turbine Airfoil Cooling Designs
Authors: Sweeney P. C. , Rhodes J. F.
Published: July 2002

An experimental approach is used to evaluate turbine airfoil cooling designs for advanced gas turbine engine applications by incorporating double-wall film-cooled design features into large-scale flat plate specimens. An infrared (IR) imaging system is used to make detailed, two-dimensional steady-state measurements of flat plate surface temperature with spatial resolution on the order of 0.4 mm. The technique employs a cooled zinc selenide window transparent to infrared radiation and calibrates the IR temperature readings to reference thermocouples embedded in each specimen, yielding a surface temperature measurement accuracy of ±4°C. With minimal thermocouple installation required, the flat plate/IR approach is cost effective, essentially nonintrusive, and produces abundant results quickly. Design concepts can proceed from art to part to data in a manner consistent with aggressive development schedules. The infrared technique is demonstrated here by considering the effect of film hole injection angle for a staggered array of film cooling holes integrated with a highly effective internal cooling pattern. Heated free stream air and room temperature cooling air are used to produce a nominal temperature ratio of 2 over a range of blowing ratios from 0.7 to 1.5. Results were obtained at hole angles of 90 and 30 deg for two different hole spacings and are presented in terms of overall cooling effectiveness. [S0889-504X(00)01901-2]
Calculation of Stress Relaxation Properties for Type 422 Stainless Steel
Authors: Ellis F. V. , Tordonato Sebastian
Published: July 2002

Analytical life prediction methods are being developed for high-temperature turbine and valve studs/bolts. In order to validate the approach, the calculated results are compared to the results of uniaxial stress relaxation testing, bolt model testing, and service experience. Long time creep, creep-rupture, and stress relaxation tests were performed by the National Research Institute for Metals of Japan (NRIM) for 12 Cr-1 Mo-1 W-1/4V, Type 422 stainless steel bolting material, at 500, 550, and 600°C. Based on these results and limited tests for a service-exposed bolt, the creep behavior can be described using a two-parameter material model: ε/εr=1−1−t/trm+1δ where εr is the rupture strain, tr is the rupture time, and m and δ are material constants. For comparison with the measured uniaxial stress relaxation properties, the stress relaxation was calculated using the two-parameter creep equation and a strain-hardening flow rule. The rupture time data was correlated using time-temperature parameter methods. A power law was used for the rupture strain versus rupture time relationship at each temperature. The calculated stress versus time curves were in good agreement with the measured at all temperatures and for initial strain levels of 0.10, 0.15, 0.20, and 0.25 percent. [S0094-9930(00)01701-7]
Polycrystalline Diamond Film on Si(100) by XPS
Authors: Schmieg Steven J. , Belton David N.
Published: July 2002

Filament-assisted chemical vapor deposition (CVD) diamond film growth on Si(100) was studied using x-ray photoelectron spectroscopy (XPS) in a system that couples a growth chamber to an ultrahigh vacuum analytical chamber. Diamond nucleates and grows on a SiC layer formed on the Si(100) substrate [D. N. Belton and S. J. Schmieg, Appl. Phys. Lett. 54, 416 (1989)]. After about 17 h growth XPS showed no Si signal from the substrate, no detectable contaminants, and only carbon present in survey scans. Electron energy loss spectroscopy (EELS) spectra obtained by x-ray excitation of the C 1s level can be used as a fingerprint for distinguishing diamond from graphite or carbides [D. N. Belton and S. J. Schmieg, J. Vac. Sci. Technol. A 8, 2353 (1990)]. The identification of a continuous diamond film was confirmed with Raman spectroscopy and scanning electron microscopy (SEM).
Ge(111) 2×1 by XPS
Authors: Poirier D. M. , Weaver J. H.
Published: July 2002

XPS spectra were recorded for the Ge(111) 2×1 cleavage surface of a single crystal. For comparison, spectra were taken for samples cleaved in air (Accession #00113) and in situ (Accession #00112). The 2p, 3d, LMM, and valence band regions were measured.
Nickel Monochromated Al K
α XPS Spectra from the Physical Electronics Model 5400 Spectrometer
Authors: Mansour A. N.
Published: July 2002

Nickel spectra were measured with the Physical Electronics Model 5400 x-ray photoelectron spectrometer (XPS) using monochromatic Al Kα at five pass energy settings corresponding to analyzer resolutions of 1.34, 0.54, 0.27, 0.13, and 0.067 eV. The specimen is a high purity 4 μm thick nickel foil (99.95%) obtained from the Goodfellow Corporation and was sputter-cleaned by 3 keV Ar ions for 5 min. We present the survey spectrum (binding energy range of 0–1100 eV) measured at an analyzer energy resolution of 1.34 eV. Multiplexes of the Ni 2p (845–895 eV), Ni 3p (58–88 eV), Ni 3s (100–130 eV), Ni 2s (995–1025 eV), valence band region (−5–20 eV), and Ni LVV Auger lines (611–661 eV) were measured at analyzer energy resolutions of 0.54, 0.27, and 0.13 eV. Those of the Ni 2p (847–885 eV), Ni 3p (59–84 eV), valence band region (−3–15 eV), and Ni LVV Auger lines (612–655 eV) were also measured at analyzer energy resolution of 0.067 eV.
Characterization of β-Ni(OH)2 by XPS
Authors: Mansour A. N.
Published: July 2002

We report x-ray photoemission spectra (XPS) of beta-nickel hydroxide (β-Ni(OH)2). XPS spectra were measured with the Physical Electronics Model 5400 x-ray photoelectron spectrometer using unmonochromated Mg Kα x rays at two pass energy settings corresponding to analyzer energy resolutions of 1.34 and 0.54 eV. We present the survey spectrum (binding energy range of 0–1100 eV) measured at an analyzer energy resolution of 1.34 eV. Multiplexes of the C, O, and Ni photoemission lines, valence band region as well as the Ni LVV Auger lines were measured at an analyzer energy resolution of 0.54 eV. The research grade high purity β-Ni(OH)2 sample was obtained commercially from Chemical Company, Inc.