bluuebunny/crossref_metadata_2025 huggingface dataset:
A Study of the Lubrication Behavior of Solid Lubricants in the Upsetting Process
Authors: Nakamura Tamotsu , Tanaka Shigekazu , Hayakawa Kunio , Fukai Yoshiaki
Published: July 2002

Four kinds of solid lubricants were tested in order to examine the frictional characteristics and the yield shear stress by the friction testing apparatus developed by the authors. The frictional shear stresses τf increased approximate linearly with the punch pressure p in every solid lubricant, and the friction coefficients μ were approximately constant. The yield shear stress k was also increased with the punch pressure p. In order to investigate lubrication behaviors of solid lubricants in upsetting processes, FEM simulations for upsetting of circular plates have been carried out. Some experimental upsetting tests of circular plate were tried using some kinds of solid lubricants. It has been confirmed that the solid lubricants can lubricate successfully without metal-to-metal contact when μD at the interface between tool and solid lubricant is relatively low and μM at the interface between work piece and solid lubricant is relatively high. On the other hand, metal-to-metal contact occurs easily at the peripheral regions of the work piece, when μD is relatively high and μM is relatively low. [S0742-4787(00)00804-3]
Design of a Robust H∞ PID Control for Industrial Manipulators
Authors: Park Jonghoon , Chung Wankyun
Published: July 2002

Industrial manipulators are under various limitations against high quality motion control; for example, both frictional and dynamic disturbances should be dealt with a simple PID control structure. A robust linear PID motion controller, called the reference error feedback (REF), is proposed, which solves the nonlinear L2-gain attenuation control problem for robotic manipulators. The stability, robustness, and performance tuning of the proposed controller are analyzed. Making use of the fact that the single parameter of the induced L2-gain γ controls the performance with stability attained, we propose a simple and stable method of performance tuning called “the square law.” The analytical results are verified through experiments of a six-degrees-of-freedom industrial manipulator. [S0022-0434(00)00104-0]
Effects of In-plane Load on Flutter of Homogeneous Laminated Beam Plates with Delamination
Authors: Shiau Le-Chung , Chen Yuan-Shih
Published: July 2002

The effects of in-plane load on flutter characteristics of delaminated two-dimensional homogeneous beam plates at high supersonic Mach number are investigated theoretically. Linear plate theory and quasi-steady supersonic aerodynamic theory are employed. A simple beam-plate model is developed to predict the effects of in-plane load on flutter boundaries for the delaminated beam plates with simply supported ends. Results reveal that the presence of an in-plane compressive load degrades the stiffness and natural frequencies of the plate and thereby decreases the flutter boundary for the plate. However, for certain geometry, the flutter boundaries were raised due to flutter coalescence modes of the plate altered by the presence of the in-plane load on the plate.
Effects of NO Models on the Prediction of NO Formation in a Regenerative Furnace
Authors: Ishii T. , Zhang, C. , Sugiyama S.
Published: July 2002

A study of the effects of nitric oxide (NO) models on the prediction of NO formation in a gas-fired regenerative furnace with highly preheated air was undertaken. Three chemical kinetic processes for NO formation/depletion, i.e., thermal NO, prompt NO, and NO reburning, are included. In the thermal NO model, the sensitivity encountered when using two different approaches, namely the equilibrium approach and the partial equilibrium approach, for determining the O radical concentration was studied. The effects of the third reaction in the thermal NO mechanism, NO reduction (reburning) mechanism, and different types of probability density functions (PDFs) on the NO predictions have also been tested. The sensitivity of the excess air ratio on the NO generation rate in the furnace has been investigated. Finally, the impact of the temperature on the NO formation rate in the regenerative furnace was discussed. [S0195-0738(00)00304-6]
Extrinsic Cell Infiltration and Revascularization Accelerate Mechanical Deterioration of the Patellar Tendon After Fibroblast Necrosis
Authors: Tohyama Harukazu , Yasuda Kazunori
Published: July 2002

This study was performed to determine the contribution of extrinsic cell infiltration and revascularization into the patellar tendon in alteration of the mechanical properties of the patellar tendon after intrinsic fibroblast necrosis using 77 rabbits. In Group I, after the patellar tendon underwent the in situ freeze-thaw treatment, a wrapping treatment was performed to inhibit any extrinsic cell infiltration into the tendon. In Group II, the patellar tendon underwent the freeze-thaw treatment without any of the wrapping treatment. In Group III, the patellar tendon underwent the same wrapping treatment but without any freeze-thaw treatment. The cell culture study demonstrated that the in situ freeze-thaw treatment killed from 97 to 100 percent of the cells in the patellar tendon. Histologically, no cells were found in the midsubstance of the patellar tendon in Group I at 1, 3, and 6 weeks. In Group II, a number of cells and some vessels were found scattered in the tendon at 3 and 6 weeks. Mechanically, the elastic modulus and the tensile strength of the patellar tendon of Group II were significantly lower than those of Groups I and III at 3 and 6 weeks. These facts suggest that extrinsic cell infiltration and revascularization from the surrounding tissues accelerate the deterioration of the mechanical properties of the patellar tendon matrix after intrinsic fibroblast necrosis. [S0148-0731(00)00506-9]
Development of One-Dimensional Models for Elastic Waves in Heterogeneous Beams
Authors: Murakami H. , Yamakawa J.
Published: July 2002

In order to develop an accurate one-dimensional model for wave propagation in heterogeneous beams with uniform cross sections, a Hamilton-type principle is developed by incorporating Reissner’s semi-complimentary energy function. Trial displacement and transverse stress fields are constructed from the solutions of micro-boundary value problems (MBVP’s) defined over the cross section. The MBVP’s are developed from asymptotic expansions that assume a small diameter cross section compared to the axial length and a typical signal wavelength. Saint Venant’s semi-inverse torsion and flexure problems are included in the system of MBVP’s. By utilizing the displacement and transverse stress fields constructed from the numerical solutions of the MBVP’s, the constitutive relations are developed. The model generalizes the Mindlin-Hermann rod model and the Timoshenko beam model for anisotropic heterogeneous beams. The accuracy of the model is assessed by comparing the predicted phase velocity spectra to those computed by using a semi-analytical finite element method. Numerical results are shown for reinforced concrete beams with exterior composite layers. [S0021-8936(01)00601-8]
Sagittal Profile of the Femoral Condyles and Its Application to Femorotibial Contact Analysis
Authors: Nun˜o N. , Ahmed A. M.
Published: July 2002

Measurements of the sagittal profiles of the articular surfaces of 24 femoral condyles were performed using a laser range finder. An algebraic algorithm was developed to reconstruct the measured sagittal profiles with simple geometry. In particular, it has been shown that a two-circular-arc model provides a very accurate reconstruction of the actual profiles in the femorotibial contact region. The average sagittal profile was used for a femorotibial contact analysis of TKA implants. The contact analysis was performed by using a rigid-body-spring model extended to the case of nonlinear force-deformation behavior of the tibial polyethylene component.
Analysis of Small Edge Cracks and Its Implications to Multiaxial Fatigue Theories
Authors: Wang Y. , Pan J.
Published: July 2002

The near-tip fields of small edge (Case B) cracks in power-law hardening materials are investigated under generalized plane strain, mixed mode, and general yielding conditions by finite element analyses. The results of the J integral from the finite element analyses are used to correlate to a fatigue crack growth criterion for Case B cracks. The trend of constant J contours on the Γ-plane is compared reasonably well with those of the experimental results of constant fatigue life and constant fatigue crack growth rate under multiaxial loading conditions.
Effect of Material and Geometry on the Sound and Vibration Transmission across a Sandwich Beam
Authors: Thamburaj Priya , Sun J. Q.
Published: July 2002

This paper studies sound and vibration transmission across a sandwich beam made of anisotropic materials. In our previous study, we have found that there is a significant increase in the transmission loss for the sandwich beam with anisotropic materials as compared with isotropic ones. This paper presents an extensive numerical study of the effects of damping, thickness of the laminae and density of the material on the sound transmission loss. This work may eventually lead to a new way of designing sandwich structures with high vibration and noise isolation performance.
Investigation on Turbulent Expansion-Corner Flow With Shock Impingement
Authors: Chung Kung-Ming
Published: July 2002

Experiments are performed to study the interaction of an impinging shock wave and an expansion fan in a Mach 1.280 flow. The expansion fan neutralizes the pressure rise induced by the impinging shock wave. The mean surface static pressure shows a linear combination of the effect of both perturbations. Surface pressure fluctuations, which are associated with the characteristics of the perturbed boundary layer, indicate a transitional behavior. This is related to a nonlinear phenomenon arising the simultaneous action of the impinging shock wave and the expansion fan. The level of downstream pressure fluctuation depends on the overall inviscid interaction strength.
Estimates of Crack-Driving Force in Surface-Cracked Elbows
Authors: Wilkowski Gery M. , Mohan Raj , Kilinski Thomas J.
Published: July 2002

The objective of this effort was to assess whether a simple relationship could be developed between the behavior of surface cracks in straight pipe and in elbows. If such a geometric relationship could be developed, then a simple multiplier could be applied to the current straight-pipe solutions that are already used in codes and standards such as the ASME or other codes. In order to accomplish this objective, solutions from elbow and straight-pipe elastic-plastic fracture mechanics (EPFM) analyses were used along with experimental data. The elbow EPFM solution came from a J-estimation scheme developed during the IPIRG-2 program. These solutions were for an elbow with a pressure at the design stress limits of Section III of the ASME Code for typical nuclear piping steels. Significant efforts were undertaken in that program to develop J-estimation schemes for axial (along the side of the elbow) and circumferential surface cracks (centered on the extrados) in elbows under constant pressure and in-plane bending. These analyses were developed using the GE/EPRI methodology of determining an elastic and plastic contribution to J, and developing the appropriate functions through a matrix of EPFM finite element analyses. Even with this large matrix of FEM analyses, only one circumferential crack length and one axial crack length were investigated. Hence, it was desirable to develop a method to extend the analysis capabilities to other crack geometry, as well as developing a simplified procedure. A comparison of the elbow to straight-pipe moment versus crack-driving force curves showed that there is a simple multiplier linearly related to the ASME B2 stress index for elbows of different R/t ratios. Hence, a simplified procedure was determined where the straight-pipe solution could be multiplied by a function of the elbow stress indices to give the maximum load prediction of the surface-cracked elbow. Comparisons were made to circumferential surface-cracked elbow data from the IPIRG-2 program, and an axial surface-cracked elbow test conducted by EDF. The comparisons showed the simplified methods to be quite promising.
Three-Dimensional Solutions of Smart Functionally Graded Plates
Authors: Reddy J. N. , Cheng Z.-Q.
Published: July 2002

A smart functionally graded plate consists of a plate made of a functionally gradient material and actuators made of an active material. The active material, a layer or set of patches, is bonded on the metal-rich surface of the functionally graded plate. When the ceramic-rich surface of the substrate is subjected to thermomechanical loadings, displacements, and stresses may be controlled, and vibration amplitudes may be suppressed by the actuators with supplied electric power. In the attempt towards a basic understanding of the new type of smart structural system, this study considers a benchmark problem, namely, the bending of a functionally graded rectangular plate with an attached piezoelectric actuator. The transfer matrix and asymptotic expansion techniques are employed to obtain a three-dimensional asymptotic solution. In numerical computations, the locally effective material properties of the functionally gradient material are estimated by the Mori-Tanaka scheme. The three-dimensional distributions of displacements and stresses for different volume fractions of the ceramic and metallic constituents could serve as benchmark results to assess approximate theories and numerical methods.
Solar Production of Zinc from the Zinc Silicate Ore Willemite
Authors: Weidenkaff Anke , Reller Armin , Steinfeld Aldo
Published: July 2002

The thermal extraction of zinc from its ore willemite, Zn2SiO4, is investigated using concentrated solar energy. Experiments conducted at above 1750 K in a high-flux solar furnace yielded the products Zn(g), O2, and SiO2l.
Explicit Equations of Motion for Mechanical Systems With Nonideal Constraints
Authors: Udwadia F. E. , Kalaba R. E.
Published: July 2002

Since its inception about 200 years ago, Lagrangian mechanics has been based upon the Principle of D’Alembert. There are, however, many physical situations where this confining principle is not suitable, and the constraint forces do work. To date, such situations are excluded from general Lagrangian formulations. This paper releases Lagrangian mechanics from this confinement, by generalizing D’Alembert’s principle, and presents the explicit equations of motion for constrained mechanical systems in which the constraints are nonideal. These equations lead to a simple and new fundamental view of Lagrangian mechanics. They provide a geometrical understanding of constrained motion, and they highlight the simplicity with which Nature seems to operate.
Experimental Study of 3D Unsteady Flow Around Oscillating Blade With Part-Span Separation
Authors: Queune O. J. R. , He L.
Published: July 2002

This paper documents an investigation conducted on the aerodynamic response of a turbine blade oscillating in a three-dimensional bending mode under massive tip separation. Flow separation near the tip of the blade was realized by use of a step placed upstream of the blade’s leading edge. Extensive blade surface steady and unsteady pressure measurements were obtained from a test facility with clearly defined boundary conditions for a range of reduced frequency. The experiment is designed to produce detailed and reliable 3D test cases for aeroelastic applications. A complete set of steady and unsteady blade surface pressure measurements is provided for five spanwise sections at 10, 30, 50, 70, and 90 percent of span. In addition, the issue of linearity is addressed. Experimental results demonstrate a predominant linear behavior of the unsteady pressure response.
Designing a Control and Containment Device for Cradle-Mounted, Transverse-Actuated Swash Plates
Authors: Manring Noah D.
Published: July 2002

Many axial-piston pumps utilize a swash plate for regulating discharge flow. In this research, the required control and containment forces are examined for a cradle-mounted, transverse-actuated swash plate. These forces are described in closed-form for providing the designer with information that is necessary for sizing these critical components within the pump. In this research, it is shown that improper design of the containment device will cause the swash plate to dislocate itself from the cradle. In general, it is noted that this failure mode is severe and that it may even cause catastrophic failure of the pump. In summary, a design criterion is presented which describes the limits of successful operation during both high and low-pressure conditions. Design and operational changes are suggested for improving the adequacy of the swash-plate containment design.
Prediction and Measurement of Thermoacoustic Improvements in Gas Turbines With Annular Combustion Systems
Authors: Kru¨ger U. , Hu¨ren J. , Hoffmann S. , Krebs W. , Flohr P. , Bohn D.
Published: July 2002

Environmental compatibility requires low emission burners for gas turbine power plants. In the past, significant progress has been made developing low NOx and CO burners by introducing lean premixed techniques in combination with annular combustion chambers. Unfortunately, these burners often have a more pronounced tendency to produce combustion-driven oscillations than conventional burner designs. The oscillations may be excited to such an extent that the risk of engine failure occurs. For this reason, the prediction of these thermoacoustic instabilities in the design phase of an engine becomes more and more important. A method based on linear acoustic four-pole elements has been developed to predict instabilities of the ring combustor of the 3A-series gas turbines. The complex network includes the whole combustion system starting from both compressor outlet and fuel supply system and ending at the turbine inlet. The flame frequency response was determined by a transient numerical simulation (step-function approach). Based on this method, possible improvements for the gas turbine are evaluated in this paper. First, the burner impedance is predicted theoretically and compared with results from measurements on a test rig for validation of the prediction approach. Next, the burner impedance in a gas turbine combustion system is analyzed and improved thermoacoustically. Stability analyses for the gas turbine combustion system show the positive impact of this improvement. Second, the interaction of the acoustic parts of the gas turbine system has been detuned systematically in circumferential direction of the annular combustion chamber in order to find a more stable configuration. Stability analyses show the positive effect of this measure as well. The results predicted are compared with measurements from engine operation. The comparisons of prediction and measurements show the applicability of the prediction method in order to evaluate the thermoacoustic stability of the combustor as well as to define possible countermeasures.
Cryosurgery of Normal and Tumor Tissue in the Dorsal Skin Flap Chamber: Part I—Thermal Response
Authors: Hoffmann Nathan E. , Bischof John C.
Published: July 2002

Current research in cryosurgery is concerned with finding a thermal history that will definitively destroy tissue. In this study, we measured and predicted the thermal history obtained during freezing and thawing in a cryosurgical model. This thermal history was then compared to the injury observed in the tissue of the same cryosurgical model (reported in companion paper (Hoffmann and Bischof, 2001)). The dorsal skin flap chamber, implanted in the Copenhagen rat, was chosen as the cryosurgical model. Cryosurgery was performed in the chamber on either normal skin or tumor tissue propagated from an AT-1 Dunning rat prostate tumor. The freezing was performed by placing a ∼1 mm diameter liquid-nitrogen-cooled cryoprobe in the center of the chamber and activating it for approximately 1 minute, followed by a passive thaw. This created a 4.2 mm radius iceball. Thermocouples were placed in the tissue around the probe at three locations (r=2, 3, and 3.8 mm from the center of the window) in order to monitor the thermal history produced in the tissue. The conduction error introduced by the presence of the thermocouples was investigated using an in vitro simulation of the in vivo case and found to be <10°C for all cases. The corrected temperature measurements were used to investigate the validity of two models of freezing behavior within the iceball. The first model used to approximate the freezing and thawing behavior within the DSFC was a two-dimensional transient axisymmetric numerical solution using an enthalpy method and incorporating heating due to blood flow. The second model was a one-dimensional radial steady state analytical solution without blood flow. The models used constant thermal properties for the unfrozen region, and temperature-dependent thermal properties for the frozen region. The two-dimensional transient model presented here is one of the first attempts to model both the freezing and thawing of cryosurgery. The ability of the model to calculate freezing appeared to be superior to the ability to calculate thawing. After demonstrating that the two-dimensional model sufficiently captured the freezing and thawing parameters recorded by the thermocouples, it was used to estimate the thermal history throughout the iceball. This model was used as a basis to compare thermal history to injury assessment (reported in companion paper (Hoffmann and Bischof, 2001)).
Stress, Strain, and Mechanotransduction in Cells
Authors: Humphrey J. D.
Published: July 2002

It is widely accepted that numerous cell types respond to mechanical stimuli, yet there is no general agreement as to whether particular cells respond directly to stress, strain, strain-rate, strain-energy, or other mechanical quantities. By recalling the definitions of the mathematical (not physical) concepts of stress and strain, it is suggested herein that cells cannot respond directly to these continuum metrics or to quantities derived from them — mechanistic models will need to be based on more fundamental quantities, as, for example, inter-atomic forces or conformational changes of the appropriate molecules. Nonetheless, the concepts of stress and strain should continue to play an important role in mechanobiology, both in the identification of empirical correlations and in the development of phenomenological constitutive models, each of which can contribute to our basic understanding as well as help in the design of future experiments and some clinical interventions. It is important to remember, therefore, that empirical correlations and most constitutive relations in continuum mechanics do not seek to model the actual physics — rather, their utility is in their predictive capability, which is often achieved via different relations in terms of different metrics for the same material under different conditions. Hence, with regard to quantifying cellular responses to mechanical stimuli, we must delineate between the identification of fundamental mechanisms and the formulation of phenomenological correlations, the latter of which only requires convenient metrics that need not be unique or physical.
Convection Induced by a Cusp-Shaped Magnetic Field for Air in a Cube Heated From Above and Cooled From Below
Authors: Kaneda Masayuki , Tagawa Toshio , Ozoe Hiroyuki
Published: July 2002

Magnetizing force, which acts in a magnetic field of steep gradient, was applied to air in a cube heated from above and cooled from below, and with the four vertical walls thermally insulated. A four-poles magnet was installed to apply the cusp-shaped magnetic field to air in the cubic enclosure. A simple model equation was derived for magnetizing force and numerically computed for the system. Without a magnetic field, the conduction was stable, but under the magnetizing force a strong downward flow occurred from the center of the top heated plate and the average Nusselt number attained Nu=1.17 at Ra=105 and γ=0.5, which is equivalent to a temperature difference of 4 [°C] between the top and bottom walls under a maximum magnetic induction of 0.9 [T] inside a cube of 0.0643 [m3] heated from above. The flow visualization experiment with hot incense smoke proved the downward flow from the top hot plate.
Numerical Simulations of Hydraulic Jumps in Water Sloshing and Water Impacting
Authors: Lee Tzung-hang , Zhou Zhengquan , Cao Yusong
Published: July 2002

A numerical investigation on Glimm’s method as applied to water sloshing and impacting is carried out. Emphasis is given to the handling and predicting hydraulic jumps. The effects of the spatial and temporal discretizations are examined. Three shallow water problems, 1) dam-breaking problem, 2) water sloshing in a rolling tank, and 3) impact of breaking of a water reservoir, are studied. It is shown numerically that Glimm’s method is stable and converged solutions can be obtained. The characteristics of the hydraulic jumps are well captured by the numerical calculations. The numerical results are in good agreement with either analytical solutions or experimental data.
Micro Scale Laser Shock Processing of Metallic Components
Authors: Zhang Wenwu , Yao Y. Lawrence
Published: July 2002

Laser shock processing of copper using focused laser beam size about ten microns is investigated for its feasibility and capability to impart desirable residual stress distributions into the target material in order to improve the fatigue life of the material. Shock pressure and strain/stress are properly modeled to reflect the micro scale involved, and the high strain rate and ultrahigh pressure involved. Numerical solutions of the model are experimentally validated in terms of the geometry of the shock-generated plastic deformation on target material surfaces as well as the average in-depth strains under various conditions. The residual stress distributions can be further influenced by shocking at different locations with certain spacing. The potential of applying the technique to micro components, such as micro gears fabricated using MEMS is demonstrated. The investigation also lays groundwork for possible combination of the micro scale laser shock processing with laser micromachining processes to offset the undesirable residual stress often induced by such machining processes.
An Experimental Study on the Seismic Response of Base-Isolated Secondary Systems
Authors: Khechfe Hany , Noori Mohammad , Hou Zhikun , Kelly James M. , Ahmadi Goodarz
Published: July 2002

The paper provides an experimental study on the feasibility of base isolation for seismic protection of nonstructural secondary system such as sensitive instrumentation, computer equipment, communication network, HVAC facilities, and power transmission systems housed in nonisolated primary structures. Damages to these secondary systems may result in significant social chaos and costly economic loss. A one-sixth-scaled three-story building model with a single-degree-of-freedom secondary system placed on its third floor is employed in this study. The secondary system is base-isolated by a laminated rubber bearing (LRB) base isolation system from the supporting floor. The ground motion input is simulated by a shaking table which generates three different types of signal including sweeping harmonic sinusoidal, the S00E component of the 1940 E1 Centro earthquake, and the simulated white noise. The experimental results demonstrate significant reduction in both displacement and acceleration responses of the secondary system by using the base isolation. Effects of parameters of the base isolation such as damping ratio and mass on its performance are also investigated. This study provides a valuable guideline for future work in this area and also verifies some previous analytical work by the authors (Hou et al., 2001). Secondary systems in a structure can be divided into two categories: structural and nonstructural. A thorough review of these types of systems and their response behavior under seismic loading has been presented by (Chen and Soong, 1988). In this paper, only nonstructural secondary systems are the subject of the study. These systems include sensitive instrumentation, computer equipment, communication network, HVAC facilities, and power transmission system that reside within a primary structure system. The huge investment made, the mission, and the critical role played by secondary systems in modern day warrant an effective protection strategy against earthquake-induced vibrations. Studies on employing base isolation techniques to protect primary structures have shown the ability of such techniques to limit dynamic response of structures in seismic disturbance (Kelley, 1986; and Ahmadi, 1988); this paper proposes the adoption of a base isolation mechanism for seismic protection of secondary systems and presents the experimental results achieved with this strategy in a scaled-down system designed without primary structural isolation. This study provides a valuable guideline for future work in this area and also verifies some previous analytical work by the authors (Ghantous, 1991; and Samaha, 1992).
Chisel Edge and Pilot Hole Effects in Drilling Composite Laminates
Authors: Won M. S. , Dharan C. K. H.
Published: July 2002

Previous studies have shown the severe limitations that have to be placed on machining forces when drilling composite laminates due to their propensity for delamination. Delamination, which consists of separation between the plys in a laminate, is due to the relatively poor strength of these materials in the thickness direction. In drilling, delamination is initiated when the drilling force exceeds a threshold value, particularly at the critical entry and exit locations of the drill bit. While abrasive machining results in damage-free holes in most composites, such processes are slow and expensive when compared to drilling with conventional twist drills. Here it is shown that the chisel edge in such drills is a major contributor to the thrust force that is the primary cause of delamination when drilling composite laminates. In this study, a series of drilling experiments were conducted on carbon fiber-reinforced composite laminates to determine quantitatively the effect of the chisel edge on the thrust force. In addition, tests were conducted to determine the effect of pre-drilling the laminate with a pilot hole. The results show a large reduction in the thrust force when a pilot hole is present which, in effect, removes the chisel edge contribution. An analytical model that incorporates the presence of a pilot hole is also described. The results from the thrust force-feed relationships show good agreement with experimentally determined values for the thrust force for a wide range of feeds for drilling tests conducted on laminates with and without pilot holes.
Modeling of Flexural Beams Subjected to Arbitrary End Loads
Authors: Kimball Chris , Tsai Lung-Wen
Published: July 2002

The analysis of compliant mechanisms is often complicated due to the geometric nonlinearities which become significant with large elastic deflections. Pseudo rigid body models (PRBM) may be used to accurately and efficiently model such large elastic deflections. Previously published models have only considered end forces with no end moment or end moment acting only in the same direction as the force. In this paper, we present a model for a cantilever beam with end moment acting in the opposite direction as the end force, which may or may not cause an inflection point. Two pivot points are used, thereby increasing the model’s accuracy when an inflection point exists. The Bernoulli-Euler beam equation is solved for large deflections with elliptic integrals, and the elliptic integral solutions are used to determine when an inflection point will exist. The beam tip deflections are then parameterized using a different parameterization from previous models, which renders the deflection paths easier to model with a single degree of freedom system. Optimization is used to find the pseudo rigid body model which best approximates the beam deflection and stiffness. This model, combined with those models developed for other loading conditions, may be used to efficiently analyze compliant mechansims subjected to any loading condition.
Spatial variation of seismic ground motions: An overview
Authors: Zerva Aspasia , Zervas Vassilios
Published: July 2002

This study addresses the topic of the spatial variation of seismic ground motions as evaluated from data recorded at dense instrument arrays. It concentrates on the stochastic description of the spatial variation, and focuses on spatial coherency. The estimation of coherency from recorded data and its interpretation are presented. Some empirical and semi-empirical coherency models are described, and their validity and limitations in terms of physical causes discussed. An alternative approach that views the spatial variation of seismic motions as deviations in amplitudes and phases of the recorded data around a coherent approximation of the seismic motions is described. Simulation techniques for the generation of artificial spatially variable seismic ground motions are also presented and compared. The effect of coherency on the seismic response of extended structures is highlighted. This review article includes 133 references.
A Finite Element Model of the Human Knee Joint for the Study of Tibio-Femoral Contact
Authors: Haut Donahue Tammy L. , Hull M. L. , Rashid Mark M. , Jacobs Christopher R.
Published: July 2002

As a step towards developing a finite element model of the knee that can be used to study how the variables associated with a meniscal replacement affect tibio-femoral contact, the goals of this study were 1) to develop a geometrically accurate three-dimensional solid model of the knee joint with special attention given to the menisci and articular cartilage, 2) to determine to what extent bony deformations affect contact behavior, and 3) to determine whether constraining rotations other than flexion/extension affects the contact behavior of the joint during compressive loading. The model included both the cortical and trabecular bone of the femur and tibia, articular cartilage of the femoral condyles and tibial plateau, both the medial and lateral menisci with their horn attachments, the transverse ligament, the anterior cruciate ligament, and the medial collateral ligament. The solid models for the menisci and articular cartilage were created from surface scans provided by a noncontacting, laser-based, three-dimensional coordinate digitizing system with an root mean squared error (RMSE) of less than 8 microns. Solid models of both the tibia and femur were created from CT images, except for the most proximal surface of the tibia and most distal surface of the femur which were created with the three-dimensional coordinate digitizing system. The constitutive relation of the menisci treated the tissue as transversely isotropic and linearly elastic. Under the application of an 800 N compressive load at 0 degrees of flexion, six contact variables in each compartment (i.e., medial and lateral) were computed including maximum pressure, mean pressure, contact area, total contact force, and coordinates of the center of pressure. Convergence of the finite element solution was studied using three mesh sizes ranging from an average element size of 5 mm by 5 mm to 1 mm by 1 mm. The solution was considered converged for an average element size of 2 mm by 2 mm. Using this mesh size, finite element solutions for rigid versus deformable bones indicated that none of the contact variables changed by more than 2% when the femur and tibia were treated as rigid. However, differences in contact variables as large as 19% occurred when rotations other than flexion/extension were constrained. The largest difference was in the maximum pressure. Among the principal conclusions of the study are that accurate finite element solutions of tibio-femoral contact behavior can be obtained by treating the bones as rigid. However, unrealistic constraints on rotations other than flexion/extension can result in relatively large errors in contact variables.
Numerical Turbulent Simulation of the Two-Phase Flow (Liquid/Gas) Through a Cascade of an Axial Pump
Authors: Tremante Andre´s , Moreno Nathaly , Rey Robert , Noguera Ricardo
Published: July 2002

The main goal of the present work is to establish the analysis of a numerical turbulent simulation of an axial pump cascade under two-phase flow presence of liquid and gas, coupled with the “κ-ε” turbulent model. This knowledge is very important for different applications, for example in the oil industry. Indeed, the transport of two-phase flow (oil and gas) that comes from the well implies the utilization of separation and treatment facilities before pumping. It means that a number of economical resources are involved in this kind of industrial operation. Therefore, depending on the function optimization of this type of two-phase pump, it would permit the substitution of the traditional expensive facilities, in addition to energy cost savings. In order to predict the fluid dynamics characteristics of an axial pump cascade under two-phase flow conditions with a view to improving its performance, the present research will describe a multifluid model in order to solve the momentum equations (Navier-Stokes) coupled with the continuity equation. Here, we will use a modified “κ-ε” turbulent model, taking into account the viscosity of the liquid phase and the compressibility of the gas phase, using the CFD simulator: CFX-4.0. As a consequence of this numerical simulation, we will be able to optimize the design of a cascade of an axial two-phase pump and therefore obtain its optimum point of operation.
Robust Speed Control of a Variable-Displacement Hydraulic Motor Considering Saturation Nonlinearity
Authors: Soo Kim Chul , Oh Lee Chung
Published: July 2002

This paper presents the speed control of a variable-displacement hydraulic motor on a constant pressure network, which is noted for its high system efficiency, fast dynamic response, and energy recovery capability. The speed control and response characteristics of the conventional cascade PI controller are considerably affected by load torque disturbances, variations in system parameters, and input magnitude. To obtain robust speed control under such conditions, the load torque is estimated by an observer and compensated for by a feedforward loop, and a windup compensator is used to prevent windup phenomena due to saturation of the regulating piston and integral controller. It is shown by experiment that improved speed control can be obtained with the proposed controller in spite of load torque disturbances, variations in system parameters, and input magnitude. [S0022-0434(00)00401-9]
Theoretical Analysis of Cavitation in Inducers With Unequal Blades With Alternate Leading Edge Cutback: Part I—Analytical Methods and the Results for Smaller Amount of Cutback
Authors: Horiguchi Hironori , Watanabe Satoshi , Tsujimoto Yoshinobu
Published: July 2002

With the idea of reducing the region of rotating cavitation by cutting back the leading edge of blade alternately and enhancing the stability of alternate blade cavitation, an analysis of steady cavitation and its stability were made for unequal blade cascade. The cavities on longer uncut blades are generally longer but they become shorter in a certain range of inlet cavitation number. This peculiar behavior is explained by an interaction effect of a local flow near cavity closure with the leading edge of the opposing blades. It is also shown that the region with stable cavities can be extended and the onset region of rotating cavitation can be diminished by cutting back the leading edge of blade alternately. In Part II, the effect of the amount of cutback is discussed. [S0098-2202(00)00402-8]
The Onset of Flow Instability in Uniformly Heated Horizontal
Microchannels
Authors: Kennedy J. E. , Roach G. M. , Dowling M. F. , Abdel-Khalik S. I. , Ghiaasiaan S. M. , Jeter S. M. , Quershi Z. H.
Published: July 2002

Onset of nucleate boiling and onset of flow instability in uniformly heated microchannels with subcooled water flow were experimentally investigated using 22-cm long tubular test sections, 1.17 mm and 1.45 mm in diameter, with a 16-cm long heated length. Important experimental parameter ranges were: 3.44 to 10.34 bar channel exit pressure; 800 to 4500 kg/m2s mass flux (1 to 5 m/s inlet velocity); 0 to 4.0 MW/m2 channel wall heat flux; and 7440–33,000 Peclet number at the onset of flow instability. Demand curves (pressure drop versus mass flow rate curves for fixed wall heat flux and channel exit pressure) were generated for the test sections, and were utilized for the specification of the onset of nucleate boiling and the onset of flow instability points. The obtained onset of nucleate boiling and onset of flow instability data are presented and compared with relevant widely used correlations. [S0022-1481(00)02101-0]
Fractional-Diffusion Solutions for Transient Local Temperature and Heat Flux
Authors: Kulish V. V. , Lage J. L.
Published: July 2002

Applying properties of the Laplace transform, the transient heat diffusion equation can be transformed into a fractional (extraordinary) differential equation. This equation can then be modified, using the Fourier Law, into a unique expression relating the local value of the time-varying temperature (or heat flux) and the corresponding transient heat flux (or temperature). We demonstrate that the transformation into a fractional equation requires the assumption of unidirectional heat transport through a semi-infinite domain. Even considering this limitation, the transformed equation leads to a very simple relation between local time-varying temperature and heat flux. When applied along the boundary of the domain, the analytical expression determines the local time-variation of surface temperature (or heat flux) without having to solve the diffusion equation within the entire domain. The simplicity of the solution procedure, together with some introductory concepts of fractional derivatives, is highlighted considering some transient heat transfer problems with known analytical solutions. [S0022-1481(00)01002-1]
Exploration of the Effectiveness of Physical Programming in Robust Design
Authors: Chen Wei , Sahai Atul , Messac Achille , Sundararaj Glynn J.
Published: July 2002

Computational optimization for design is effective only to the extent that the aggregate objective function adequately captures designer’s preference. Physical programming is an optimization method that captures the designer’s physical understanding of the desired design outcome in forming the aggregate objective function. Furthermore, to be useful, a resulting optimal design must be sufficiently robust/insensitive to known and unknown variations that to different degrees affect the design’s performance. This paper explores the effectiveness of the physical programming approach in explicitly addressing the issue of design robustness. Specifically, we synergistically integrate methods that had previously and independently been developed by the authors, thereby leading to optimal—robust—designs. We show how the physical programming method can be used to effectively exploit designer preference in making tradeoffs between the mean and variation of performance, by solving a bi-objective robust design problem. The work documented in this paper establishes the general superiority of physical programming over other conventional methods (e.g., weighted sum) in solving multiobjective optimization problems. It also illustrates that the physical programming method is among the most effective multicriteria mathematical programming techniques for the generation of Pareto solutions that belong to both convex and non-convex efficient frontiers. [S1050-0472(00)00902-8]
The Pressure Vessel Research Council of the Welding Research Council, Inc.
Authors: Karcher Guido G.
Published: July 2002

[S0094-9930(00)02101-6]
Self-Excited Sloshing due to the Fluid Discharge Over a Flexible Plate Weir
Authors: Nagakura Hiroshi , Kaneko Shigehiko
Published: July 2002

This paper presents an analytical model for the self-excited sloshing due to the fluid discharge over a flexible weir, as observed in the cooling circuit of the French fast breeder reactor, Super-Phenix-1. To clarify the instability mechanism, we analyzed the case in which a rectangular reservoir was divided into an upstream and a downstream plenum by a flexible plate weir. The kinematic and dynamic effects of the discharged fluid on downstream plenum sloshing are discussed in details. Calculations are presented for the rectangular fluid-structure model with successively increasing fluid level difference between the upstream and downstream plenums, and the instability mechanism is examined. [S0094-9930(00)00302-4]
Discussion
Authors: Fletcher Edward A.
Published: July 2002

[S0199-6231(00)00401-9]
Active Mode Localization in Distributed Parameter Systems with Consideration of Limited Actuator Placement, Part 1: Theory
Authors: Shelley Franz J. , Clark William W.
Published: July 2002

The purpose of this two-part work is to apply active mode localization to distributed parameter systems where the number of control sensors and actuators is a limiting factor. In this part, the theoretical development portion of the study, two approaches are presented that shape system eigenvectors using feedback control, generating localization to produce areas of isolation with relatively low vibration amplitudes compared to other parts of the structure. The first approach uniformly shapes all eigenvectors of a vibrating system, but can require many actuators to do so. The second more general approach uses singular value decomposition (SVD) to shape selected eigenvectors of a system, localizing the response of these modes to any disturbance, and requiring few actuators. [S0739-3717(00)70202-9]
A Study of Si3N4 by XPS
Authors: Chourasia A. R. , Chopra D. R.
Published: July 2002

The Si3N4 sample was grown by chemical vapor deposition on a Si substrate at 900 °C using a mixture of SiH4, NH3, and H2 gases. Prior to deposition the Si wafer was cleaned in HCl vapor at about 1050 °C. The formation of Si3N4 was checked by x-ray diffraction. This sample was analyzed by x-ray photoelectron spectroscopy. The XPS data in the Si 2s, Si 2p, N 1s, and N KVV Auger regions are presented. A wide range of binding energy values for these constituents has been reported in the literature [see C. D. Wagner, D. E. Passoja, H. F. Hillery, T. G. Kinisky, H. A. Six, W. T. Jansen, and J. A. Taylor, J. Vac. Sci. Technol. 21, 933 (1982); J. A. Taylor, Appl. Surf. Sci. 7, 168 (1981); and T. N. Wittberg, J. R. Hoenigman, W. E. Moddeman, C. R. Cothern, and M. R. Gulett, J. Vac. Sci. Technol. 15, 348 (1978)]. The present data will serve as a reference for CVD Si3N4 film which has wide applications in semiconductor technology.
Single Crystal 6H-SiC(0001) by XPS
Authors: Bozack Michael J.
Published: July 2002

X-ray photoemission spectra for the Si-terminated face of single crystal 6H-SiC(0001) are reported. The specimen was cut from a commercial (CREE Research) 1-in., n-doped wafer. SiC has recently attracted attention in semiconductor applications requiring high temperature, high frequency, and high power operation. A companion submission shows AES spectra.
Comparison of Ti 2p Core-Level Peaks from TiO2, Ti2O3, and Ti Metal, by XPS
Authors: Kurtz Richard L. , Henrich V. E.
Published: July 2002

These spectra compare the Ti 2p core-level XPS line shape for atomically clean, stoichiometric samples of Ti, Ti2O3, and TiO2; the latter two are UHV-cleaved or fractured single crystals. The Ti0 and Ti4+ peaks of Ti metal and TiO2, respectively, exhibit the simple shapes expected for such core levels. The Ti3+ peaks of Ti2O3, however, are more complex, although there are no other valence states of Ti in the sample.