bluuebunny/crossref_metadata_2025 huggingface dataset:
The Separation Between Turbulence and Mean Flow in ICE LDV Data: The Complementary Point-of-View of Different Investigation Tools
Authors: Amelio Mario , Bova Sergio , De Bartolo Carmine
Published: July 2002

LDV measurements have been taken in a disc chamber four-stroke reciprocating engine under motoring conditions. Two non-simultaneous velocity components have been recorded at three different locations on the mid-plane of the TDC clearance during the intake and compression strokes for three different speeds (600, 800, 1000 rpm). The locations are characterized by different flow conditions (near the intake valves; on the cylinder axis; near the exhaust valves). The combination of different engine speeds and different chamber locations enables one to look both at the global behavior of the flow and at the details of the turbulence time-evolution. The aim of the research is to identify the frequency which can be considered a separation between “true” turbulence and cycle-by-cycle variation of the mean flow and to analyze the variation of such a frequency with the measuring location and with the engine speed. The analysis has been carried out by using different tools: the non-stationary velocity autocorrelation function, the power spectrum and the cycle-resolved analysis based on the frequency filter. The various approaches offer complementary perspectives of the same phenomenon, which give a clear perception of the physical meaning of the most frequently used investigation tools. The results show that the cut-off frequency increases as the engine speed increases and as the measuring point moves away from the ordered jet coming out of the intake valves. [S0742-4795(00)01204-7]
Linear Dynamics of an Elastic Beam Under Moving Loads
Authors: Visweswara Rao G.
Published: July 2002

The dynamic response of an Euler-Bernoulli beam under moving loads is studied by mode superposition. The inertial effects of the moving load are included in the analysis. The time-dependent equations of motion in modal space are solved by the method of multiple scales. Instability regions of parametric resonance are identified and the moving mass effect is shown to significantly affect the transient response of the beam. Importance of modal interaction arising out of the possible internal resonance is highlighted. While the external resonance is due to the gravity effects of the moving load, the parametric and internal resonance solely depends on the load mass parameter—ratio of the moving load mass to the beam mass. Numerical results show the influence of the load inertia terms on the beam response under either a single moving load or a series of moving loads. [S0739-3717(00)01703-7]
Vibration Characteristics of Conical Shell Panels With Three-Dimensional Flexibility
Authors: Liew K. M. , Feng Z. C.
Published: July 2002

A first known investigation on the three-dimensional vibration characteristics of conical shell panels is reported. A linear frequency equation is derived based on an exact three-dimensional, small-strain, linearly elastic theory. Sets of one and two-dimensional polynomial series are employed to approximate the spatial displacements of the conical shell panels in three dimension. The perturbation of frequency responses due to the variations of relative thickness L/h, slanted length L/S, vertex angle γv, and subtended angle γo is investigated. First known frequency parameters and three-dimensional deformed mode shapes of the conical shell panels are presented in vivid graphical forms. The new results may serve as benchmark references for validating the new refined shell theories and new computational techniques. [S0021-8936(00)02302-3]
On the Dynamics of the Dynabee
Authors: Gulick D. W. , O’Reilly O. M.
Published: July 2002

The Dynabee is a gyroscopic device that is marketed as a wrist exerciser. In this paper, a model for the dynamics of this device is presented. With some additional work, we find that the dynamics are governed by a single ordinary differential equation. The solution of this equation also provides the moment required to operate the device. Specifically, we find that this moment is proportional to the square of the rotor’s spin rate. We also show why it is necessary to give the device a large initial spin rate for its successful operation. [S0021-8936(00)02602-7]
A Normal Force-Displacement Model for Contacting Spheres Accounting for Plastic Deformation: Force-Driven Formulation
Authors: Vu-Quoc L. , Zhang X. , Lesburg L.
Published: July 2002

In this paper, we present a simple and accurate model for the normal force-displacement (NFD) relation for contacting spherical particles, accounting for the effects of plastic deformation. This NFD model, based on the formalism of the continuum theory of elastoplasticity, is to be used in granular flow simulations involving thousands of particles; the efficiency of the model is thus a crucial property. The accuracy of the model allows for an accurate prediction of the contact force level in the plastic regime. In addition to being more accurate than previously proposed NFD models, the proposed NFD model also leads to more accurate coefficient of restitution that is a function of the approaching velocity of two particles in collision. The novelty of the present NFD model is the additive decomposition of the contact-area radius, and the correction of the curvature of the particles at the contact point due to plastic flow. The accuracy of the proposed model is validated against nonlinear finite element results involving plastic flow in both loading and unloading conditions. [S0021-8936(00)03102-0]
Thermal Asperities Sensitivity to Particles: Methodology and Test Results
Authors: Wang Larry Y. , Sullivan Mike , Chao Jim
Published: July 2002

Thermal asperities (TA’s) are tribological events that cause repercussions for giant magnetoresistance (GMR) and MR heads in the hard disk drive industry. A TA is a read signal spike caused by sensor temperature rise due to contact with disk asperities or contaminant particles. TA events may cause GMR and MR heads to temporarily lose their reading capability, and may potentially damage the transducer. It is difficult to completely avoid particle contamination in hard drive applications. Hence it is necessary to design heads/media with a minimum TA sensitivity to particles. A test method for TA sensitivity to particles is needed. This work developed a test method for TA sensitivities to particles. The test system includes a CSS tester with TA detection capability, a chamber to contain the head/disk interface, a particle atomizer, and a particle counter. Aluminum silicate particles used in the test have sizes ranging from 0.2 to 1.0 μm. Particles are injected into the chamber during head scan for TA’s from ID to OD with adjustable air-borne concentrations in the chamber from 10×106 to 30×106particles/m3. TA counts of 30 scans are averaged to obtain reliable TA sensitivity data. Media with different lubricant thickness, different carbon overcoats, and different lubricant types are tested with this method. The results indicated that this methodology can effectively differentiate TA sensitivity to particles for the media studied.
Fitting Creep-Rupture Life Distribution Using Accelerated Life Testing Data
Authors: Zuo M. , Chiovelli S. , Nonaka Y.
Published: July 2002

This paper comments on using the Larson-Miller parameter to fit the creep-rupture life distribution as a function of temperature and stress. The commonly used least-squares linear regression method assumes that the creep-rupture life follows the lognormal distribution. Most engineering literature does not discuss the validity of this assumption. In this paper, we outline the procedure for validating two critical assumptions when the least-squares method is used. The maximum likelihood method is suggested as an alternative and more powerful method for fitting creep-rupture life distributions. Examples are given to demonstrate the use of these two methods using Microsoft Excel and the LIFEREG procedure in SAS. [S0094-9930(00)00504-7]
Multiaxial Constitutive Behavior of Ferroelectric Materials
Authors: Chen Wei , Lynch Christopher S.
Published: July 2002

Multiaxial ferroelectric/ferroelastic constitutive laws governing the behavior of ceramic lead zirconate titanate (PZT) are needed for numerical calculations of stress and electric field in the vicinity of field concentrators such as cracks, inhomogeneities, and partial electrodes. Multiaxial constitutive behavior was measured using tubular specimens, both poled and unpoled. The specimens were subjected to simultaneous axial load, internal pressure, and external pressure. Deformation was measured using strain gages. The results were used to map out a “yield” (ferroelastic polarization reorientation threshold or switching) surface. The composition used, 8/65/35 PLZT, was found to obey a Tresca criterion when in the unpoled state. The switching surface was found to be a function of the polarization state. Kinematic and isotropic hardening appear to be good candidates for describing subsequent switching surfaces.
Eccentric Crack in a Piezoelectric Strip Under Electromechanical Loading
Authors: Shin Jeong Woo , Kwon Soon Man , Lee Kang Yong
Published: July 2002

[S00021-8936(01)00301-4]
Numerical Study of Three-Dimensional Oscillatory Natural Convection at Low Prandtl Number in Rectangular Enclosures
Authors: Wakitani Shunichi
Published: July 2002

Numerical investigations are presented for three-dimensional natural convection at low Prandtl numbers (Pr) from 0 to 0.027 in rectangular enclosures with differentially heated vertical walls. Computations are carried out for the enclosures with aspect ratios (length/height) 2 and 4, and width ratios (width/height) ranging from 0.5 to 4.2. Dependence of the onset of oscillation on the Prandtl number, the aspect ratio, and the width ratio is investigated. Furthermore, oscillatory, three-dimensional flow structure is clarified. The structure is characterized by some longitudinal vortices (rolls) as well as cellular pattern.
Inverse Static Analysis of a Planar System With Flexural Pivots
Authors: Carricato Marco , Parenti-Castelli Vincenzo , Duffy Joseph
Published: July 2002

This article presents the inverse static analysis of a two degrees of freedom planar mechanism with flexural pivots. Such analysis aims to detect the entire set of equilibrium configurations of the system once the external load is assigned. The presence of flexural pivots represents a novelty, although it remarkably complicates the problem since it causes the two state variables to appear in the solving equations as arguments of both trigonometric and linear functions. The proposed procedure eliminates one variable and leads to two equations in one unknown only. The union of the root sets of such equations constitutes the global set of solutions of the problem. Particular attention is paid to the analysis of the reliability of the final equations: critical situations, in which the solving equations may hide solutions or yield false ones, are studied. Finally, a numerical example is provided and, in the Appendix, a special design that offers computational advantages is proposed.
Using the Simulation Model for Identification of the Fatigue Parameters of Hydraulically Driven Log Crane
Authors: Mikkola A.
Published: July 2002

The present paper introduces a method based on dynamic simulation for determining the fatigue parameters in a hydraulically driven log crane. The parameters that describe the nature of fatigue loads can be applied in order to facilitate designer work in fatigue life prediction. The detailed simulation model was built up in the ADAMS mechanical analysis software environment in which the flexible mechanism model and the equations describing the hydraulic system were combined. The complete simulation model was verified by comparing measurements to numerical results. This comparison shows that there is a clear correspondence between the simulated and measured results. The model was employed in the study of the fatigue parameters, which are formed when the crane is being loaded.
Plastic Coupling and Stress Relaxation During Nonproportional Axial-Shear Strain-Controlled Loading
Authors: Lissenden Cliff J. , Arnold Steven M. , Saleeb Atef F.
Published: July 2002

A nonproportional strain-controlled load path consisting of two segments was applied to the cobalt-based alloy Haynes 188 at 650°C. The first segment was purely axial; the axial strain was then held constant while the shear strain was increased during the second segment. The alloy exhibited about a 95-percent reduction in axial stress (298 to 15 MPa) during shear straining. This reduction was due primarily to plastic coupling, but time-dependent stress relaxation also occurred. A rate-independent plasticity model approximated the stress reduction due to plastic coupling reasonably well, but as expected was unable to account for time-dependent stress relaxation. A viscoplasticity model capable of predicting the interaction between stress relaxation and plastic coupling also predicted the plastic coupling reasonably well. The accuracy of the viscoplastic model is shown to depend greatly upon the set of nonunique material parameters, which must be characterized from a sufficiently large range of load histories.
Solar Production of Aluminum by Direct Reduction: Preliminary Results for Two Processes
Authors: Murray Jean P.
Published: July 2002

The production of aluminum or silicon by reduction of their oxides with carbon is a technical challenge. The temperature required, in the range 2100–2300°C, is too high for practical process heat addition from a combustion source alone. When an electrothermal process is used, only about a third of the energy contained in the fuel used to generate electricity enters the process. Thus, for materials produced electrolytically or in an electric furnace, the energy cost dominates the cost of the final product. By contrast, highly-concentrated solar energy is capable of supplying large amounts of process heat at very high temperatures, and may have real advantages for metals reduction processes. An arc introduces too much energy to the reaction zone. In the case of aluminum, the metal floats and it short circuits the arc. Ideally, the heat would enter at the bottom or side of a reactor, which could be achieved with solar process heat. Among industries, the primary aluminum industry is a major consumer of electricity. It uses about 10 percent of the electricity generated globally for industrial purposes, and about half comes from coal-fired generation stations. This represents about 5 percent of the electricity generated for all sectors. A solar-thermal process would drastically reduce the emission of climate-altering gases, reduce the reliance on electricity, and might be a critical factor in making a direct thermal route from the ore to metal possible. Two industrially-developed processes appear to be attractive candidates for a solar process. Preliminary tests have been performed using a black-body cavity receiver placed at the focus of the Paul Scherrer Institute’s 70 kW tracking parabolic concentrator, and though the experiment had to be ended earlier than planned, a small amount of 61/37 weight percent Al/Si alloy was formed, and the partially reacted pellets showed conversion to Al4C3 and SiC. Further qualitative tests have been performed using the facilities at Odeillo in a 2 kW solar furnace, where the onset of production of both aluminum by direct carbothermal reduction, and Al-Si alloy via carbothermal reduction of a mixture of alumina, silica and carbon could be directly observed.
Mesh Sensitivity and FEA for Multi-Layered Electronic Packaging
Authors: Basaran Cemal , Zhao Ying
Published: July 2002

Multi-layered stacks are commonly used in microelectronic packaging. Traditionally, these systems are designed using linear-elastic analysis either with analytical solutions or finite element method. Linear-elastic analysis for layered structures yields very conservative results due to stress singularity at the free edge. In this paper, it is shown that a damage mechanics based nonlinear analysis not just leads to a more realistic analysis but also provides more accurate stress distribution. In this paper these two approaches are compared. Moreover, mesh sensitivity of the finite element analysis in stack problems is studied. It is shown that the closed form and elastic finite element analyses can only be used for preliminary studies and elastic finite element method is highly mesh sensitive for this problem. In elastic analysis the stress singularity at the free edge makes mesh selection very difficult. Even when asymptotic analysis is used at the free edge, the results are very conservative compared to an inelastic analysis. Rate sensitive inelastic analysis does not suffer from the stress singularity and mesh sensitivity problems encountered in elastic analysis.
Adjusted Least Squares Approach for Diagnosis of Ill-Conditioned Compliant Assemblies
Authors: Rong Q. , Shi J. , Ceglarek D.
Published: July 2002

Least squares (LS) estimation has been extensively used for parameter identification and model-based diagnosis. However, if ill-conditioning is present, the LS estimation approach tends to generate imprecise results and thus impacts the diagnostic performance. In this paper, an adjusted least squares approach is proposed to deal with the ill-conditioning problem in the diagnosis of compliant sheet metal assembly process. The adjusted LS approach is able to overcome the ill-conditioning and give precise results for certain linear combinations of the faults. Simulations and industrial case study are conducted to compare the diagnostic performance of the adjusted and regular LS approach. In addition, a two-stage assembly model is developed for further fault isolation with inclusion of additional measurement information.
Effects of Crank Length on the Dynamics Behavior of a Flexible Connecting Rod
Authors: Chen Jen-San , Chian Chu-Hsian
Published: July 2002

Global dynamics behavior of a damped flexible connecting rod is considered in this paper with emphasis on the effects of the rigid crank length. Nonlinear equations of motion in terms of axial and transverse deflections are derived based on Lagrangian strain formulation. When the crank length is small compared to the connecting rod, it is found that only one periodic solution exists in the speed range up to 1.5 times the first bending natural frequency of the connecting rod. As the crank length increases, however, multiple solutions may exist and the associated domains of attraction can be identified by cell-to-cell mapping technique. Moreover, the steady state response may become chaotic, which renders precise prediction of the dynamics response meaningless. The onset rotation speed of chaotic vibration decreases when the crank length increases. This result shows that previous research utilizing simplified or linearized models can predict the dynamics response of the flexible connecting rod only when both the crank length and the rotation speed are small.
Material Properties of Aluminum Alloy for Accurate Draw-Bend Simulation
Authors: Zhao K. M. , Lee J. K.
Published: July 2002

The main objective of this paper is to simulate springback using a combined kinematic/isotropic hardening model. Material parameters in the hardening model are identified by an inverse method. A three-point bending test is conducted on 6022-T4 aluminum sheet. Punch stroke, punch load, bending strain, and bending angle are measured directly during the tests. Bending moments are then computed from these measured data. Bending moments are also calculated based on a constitutive model. Material parameters are identified by minimizing the normalized error between two bending moments. A micro genetic algorithm is used in the optimization procedure. Stress-strain curves are generated with the material parameters found in this way, which can be used with other plasticity models. ABAQUS/Standard, which has the combined isotropic/kinematic hardening model, is used to simulate draw-bend of 6022-T4 aluminum sheet. Absolute springback angles are predicted very accurately.
Numerical Study of Spray Injection Effects on the Heat Transfer and Product Yields of FCC Riser Reactors
Authors: Chang S. L. , Lottes S. A. , Zhou C. Q. , Bowman B. J. , Petrick M.
Published: July 2002

A three-phase reacting flow computational fluid dynamics (CFD) computer code was used to study the major effects of spray injection parameters on mixing, heat transfer, vaporization, and reaction product yields in fluidized catalytic cracking (FCC) riser reactors. The CFD code was validated using experimental or field data. A number of computations were performed with varied injection parameters, including injection velocity, injection angle, and droplet size. Local optimum operating windows for spray injection parameters were identified, and the sensitivity of local optima to variation in spray parameters was also investigated.
Oxidation Rate of Advanced Heat-Resistant Steels for Ultra-Supercritical Boilers in Pressurized Superheated Steam
Authors: Yi Yong-Sun , Watanabe Yutaka , Kondo Tatsuo , Kimura Hiroshi , Sato Minoru
Published: July 2002

Oxidation kinetics of recently developed ferritic heat-resistant steels, HCM12A, NF616, and HCM2S, were investigated in a superheated steam to evaluate the effects of chemical composition of the steels, testing temperature (560–700°C), steam pressure (1–10 MPa), and degrees of microstructural evolution by aging on oxidation. The contribution of alloyed Cr to oxidation resistance was pronounced above 600°C, while no material dependency was found at 600°C or lower. The apparent activation energy of the oxidation rate clearly changed at around 600°C for NF616 and HCM12A. In contrast, HCM2S showed single activation energy over the range of temperatures. Although temperature and chemical composition were the major factors, steam pressure also showed a clear negative effect on the oxidation rate in the lower temperature range, 570–600°C.
A Note on Wavelet-Based Method for Damage Detection
Authors: Zhang L. , Quek S. T. , Wang Q.
Published: July 2002

The applicability of Gabor wavelet transform of time history data in detecting a thin damage in beam is examined. For the case where the damage position is completely unknown, the use of two load positions is suggested. Cases considered are the position of the sensors relative to the damage and load positions, the height of the damage, the severity of the damage, and the effect of boundary conditions. The results show that the method is suitable for detecting localized damage and relatively robust in terms of sensor position, damage height, and degree of damage.
Visualizing Diffusion Flame Formation in the Wake of Partially Premixed Combustion
Authors: Lyons K. M. , Watson K. A.
Published: July 2002

Results are presented on the formation of a diffusion flame in a methane nonpremixed jet following the propagation of partially premixed combustion. An initially nonreacting turbulent methane jet (Re=2700) in quiescent air is ignited at a downstream location x/d=70. High-speed video images (125 and 250 Hz) were obtained that chart the evolution of the combustion process. Partially premixed flame propagation is witnessed as the combustion front moves upstream (downward) toward the nozzle exit. As the front propagates, the blue (premixed) character of the flame is diminished, the combustion region narrows, and the transition to diffusion-limited combustion along the stratified methane/air layer takes place. Before reaching the nozzle exit, axial wisps of blue flame emission are witnessed along the jet-edge near the fuel/air interface (i.e., at larger radii than the eventual diffusion flame boundary). Luminosity from soot is first apparent just upstream of an axisymmetric flame bulge as the diffusion flame forms, and within 100 ms, soot attains levels present in the steady-state turbulent diffusion flame. Images are presented portraying the phenomenon, and three regimes are proposed to characterize the propagation of combustion.
An Inverse Approach to the Validation of Pressure Predictions in Rough Elastohydrodynamic Contacts
Authors: Hooke C. J. , Li K. Y.
Published: July 2002

A simple experimental technique is developed that allows the pressures and stresses predicted by EHL analyses to be checked. A soft, rough steel disc is run, under controlled conditions, against a harder, smooth counterface. The pressures generated cause the soft disc to plastically deform. Once deformation ceases the residual profile may be measured and used as input to an EHL solver. The calculated pressures are then used to determine the stress distributions as the rough surface passes through the conjunction. After allowing for the build up of residual stress the maximum von Mises’ stress should be equal to the yield strength of the disc. This provides an accurate, quantitative check on the theoretical values.
In-situ Pressure Measurements Using Raman Microspectroscopy in a Rolling Elastohydrodynamic Contact
Authors: Jubault I. , Mansot J. L. , Vergne P. , Mazuyer D.
Published: July 2002

The physical conditions (pressure, shear stress, temperature) generated in an elastohydrodynamic (EHD) contact are the main parameters governing the evolution of the physico-chemical properties of the lubricant within the contact. This paper presents in-situ measurements of pressure in an EHD point contact using Raman microspectroscopy. Two model lubricants are studied: a pure polyphenyl ether (5P4E) oil and a mixture of this oil with a liquid crystal. The influence of load and speed on the pressure distributions is investigated. The Petrusevich pressure spike is measured and its evolution with the operating parameters is in good agreement with the theoretical predictions. The addition of the liquid crystal to the base oil leads to an important diminution of the mixture viscosity, and consequently of the film thickness in the contact. The different rheological properties of the lubricants induce significant variations of the pressure profiles.
Thermoplastic Finite Element Analysis of Unfilled Plated-Through Holes During Wave Soldering
Authors: Fu Chia-Yu , McDowell David L. , Ume I. Charles
Published: July 2002

Previous related research has not developed a consensus on the issue of how stress analyses of plated-through hole (PTH)/printed wiring board (PWB) structure subject to uniform temperature change can approximate the fully transient case. In this study, these two types of analyses are conducted using McDowell’s thermoplastic model with previously developed numerical implementation by applying a finite element package and an associated user-defined material subroutine. The same wave soldering temperature profile is used. The detailed stress/strain responses of the copper layer, along the heating and cooling of the wave soldering process, are compared at both the PTH corner and barrel portions. The temperature distributions and corresponding deformations of the model are also reported for the fully transient thermal and one-way coupled mechanical analysis. It is concluded that despite the transient thermal loading, the residual stress and strain distributions within the PTH/PWB structure after cooling can be adequately approximated using the more simple analysis which prescribes a uniform temperature and temperature change at each stage of the process.
Large Deflection Analysis of a Biomimetic Lobster Robot Antenna due to Contact and Flow
Authors: Barnes T. G. , Truong T. Q. , Adams G. G. , McGruer N. E.
Published: July 2002

Lobsters use their antennae to navigate among obstacles along the ocean floor. Effective ambulation requires that the lobster, or a biomimetic lobster robot whose behavior is patterned after a real lobster, must distinguish between antenna bending due to contact and bending due to flow. The analysis presented here shows that the key feature appears to be the taper of the antennae. The curvature of a tapered antenna due to an end-load is nearly constant whereas the curvature distribution due to flow is nearly a quadratic function of the arc-length measured from the tip of the antenna.
Effect of Transverse Moduli on Through-Thickness Hygrothermal Expansion Coefficients of Composite Laminates
Authors: Yeh H.-L. , Yeh H.-Y.
Published: July 2002

In practical analysis, under a plane stress condition, a unidirectional lamina can be assumed with E2=E3 from geometrical symmetry consideration. However, from an academic point of view, it is interesting to study the case of a lamina with E2≠E3. In this paper the preliminary results of the physical phenomenon about the effect of different transverse moduli E2 and E3 on the through-thickness thermal expansion coefficients αz of quasi-isotropic composite laminates is presented.
Multiple Stability and Unpredictable Outcomes in the Chaotic Vibrations of Euler Beams
Authors: Ng T. Y. , Daolin Xu
Published: July 2002

Nonlinear phenomena in the vibration of a slender, Euler-Bernoulli beam in compression and under periodic transverse loading is investigated. A feature of this system is the coexistence of distinct bifurcation branches which provide a rich resource for numerous solution states. An indepth study based on an energy approach is done to illustrate the presence of multiple stability resulting from the multiplicity of resonant solutions. Although the behaviors may exhibit a variety of different motions, the ultimate state is very sensitively dependent upon the initial conditions. The structures of boundary basins for the coexisting attractors are illustrated and the unpredictability of outcome is discussed in detail.
The Interface Crack Problem of Bonded Piezoelectric and Elastic Half-Space Under Transient Electromechanical Loads
Authors: Meguid S. A. , Zhao X.
Published: July 2002

The interface crack problem of bonded piezoelectric and elastic half-space under transient electromechanical loads is considered. Both the permeable and impermeable boundary conditions are examined and discussed. Based on the use of integral transform techniques, the problem is reduced either to a singular integral equation for the permeable boundary condition or to two coupled singular integral equations for the impermeable boundary condition, which can be solved using Chebyshev polynomial expansions. Numerical results are provided to show the effect of the applied electric fields, the electric boundary conditions along the crack faces and a free surface on the resulting dynamic stress intensity factor and electric displacement intensity factor.
Uniaxial Ratchetting of 316FR Steel at Room Temperature— Part I: Experiments
Authors: Mizuno M. , Mima Y. , Abdel-Karim M. , Ohno N.
Published: July 2002

Uniaxial ratchetting characteristics of 316FR steel at room temperature are studied experimentally. Cyclic tension tests, in which maximum strain increases every cycle by prescribed amounts, are conducted systematically in addition to conventional monotonic, cyclic, and ratchetting tests. Thus hysteresis loop closure, cyclic hardening and viscoplasticity are discussed in the context of constitutive modeling for ratchetting. The cyclic tension tests reveal that very slight opening of hysteresis loops occurs, and that neither accumulated plastic strain nor maximum plastic strain induces significant isotropic hardening if strain range is relatively small. These findings are used to discuss the ratchetting tests. It is thus shown that uniaxial ratchetting of the material at room temperature is brought about by slight opening of hysteresis loops as well as by viscoplasticity, and that kinematic hardening governs almost all strain hardening in uniaxial ratchetting if stress range is not large. [S0094-4289(00)00401-1]
Cold Compaction of Composite Powders
Authors: Kim K. T. , Cho J. H. , Kim J. S.
Published: July 2002

Densification behavior of composite powders was investigated under cold compaction. Experimental data were obtained for mixed copper and tungsten powders with various volume fractions of tungsten powder under cold isostatic pressing and die compaction. A model was also proposed for densification of mixed—soft and hard—metal powders under cold compaction. Theoretical predictions from the proposed model and models in the literature were compared with experimental data. The agreements between experimental data and theoretical predictions from the proposed model are very good for composite powders at initial stage under cold isostatic pressing. Theoretical predictions, however, underestimate experimental data under cold die compaction. [S0094-4289(00)01901-0]
Predicted Fundamental Vibration Frequency of a Heavy Electronic Component Mounted on a Printed Circuit Board
Authors: Suhir Ephraim
Published: July 2002

External electric leads, soldered into plated through-holes (PTHs) of printed circuit boards (PCBs), provide, in addition to electrical interconnection, mechanical support for heavy electronic components (such as, say, power ones) mounted on the boards. The leads can possibly break (most likely by fatigue), if the PCB support contour is subjected to excessive oscillations. Such oscillations typically occur at the lowest resonant frequency (fundamental frequency). The ability to predict this frequency and possibly avoid resonance conditions is of obvious practical importance. Accordingly, in this analysis, we develop a simple formula for the evaluation of the fundamental vibration frequency of a heavy electronic component mounted on a PCB. The formula is obtained for the case, when the component has only one row of leads, and the vibrations occur in the direction of the least flexural rigidity of this row. [S1043-7398(00)00601-0]
Industrial Trent Combustor—Combustion Noise Characteristics
Authors: Scarinci Thomas , Halpin John L.
Published: July 2002

Thermoacoustic resonance is a difficult technical problem that is experienced by almost all lean-premixed combustors. The Industrial Trent combustor is a novel dry-low-emissions (DLE) combustor design, which incorporates three stages of lean premixed fuel injection in series. The three stages in series allow independent control of two stages—the third stage receives the balance of fuel to maintain the desired power level—at all power conditions. Thus, primary zone and secondary zone temperatures can be independently controlled. This paper examines how the flexibility offered by a 3-stage lean premixed combustion system permits the implementation of a successful combustion noise avoidance strategy at all power conditions and at all ambient conditions. This is because at a given engine condition (power level and day temperature) a characteristic “noise map” can be generated on the engine, independently of the engine running condition. The variable distribution of heat release along the length of the combustor provides an effective mechanism to control the amplitude of longitudinal resonance modes of the combustor. This approach has allowed the Industrial Trent combustion engineers to thoroughly “map out” all longitudinal combustor acoustic modes and design a fuel schedule that can navigate around regions of combustor thermoacoustic resonance. Noise mapping results are presented in detail, together with the development of noise prediction methods (frequency and amplitude) that have allowed the noise characteristics of the engine to be established over the entire operating envelope of the engine. [S0742-4795(00)00802-4]
Effect of Tube Inclination on Pool Boiling Heat
Transfer
Authors: Kang M.-G.
Published: July 2002

An experimental parametric study of a tubular heat exchanger has been carried out under pool boiling conditions to determine effects of the tube inclination angle on pool boiling heat transfer. Through the study, it can be concluded that (1) tube inclination gives much change on pool boiling heat transfer and the effect of the inclination angle is more strongly observed in the smooth tube and (2) if a tube is properly inclined, enhanced heat transfer is expected due to the decrease in bubble slug formation on the tube surface and easy liquid access to the surface. [S0022-1481(00)01201-9]
Alternative Equation of Meshing for Worm-Gear Drives and Its Application to Determining Undercutting and Reverse Engineering
Authors: Su Xiaogen , Houser Donald R.
Published: July 2002

An alternative equation of meshing for worm-gear drives is proposed. This equation has advantage over the commonly used equation of meshing when it is used to study the undercutting phenomenon, to perform reverse engineering and to find the meshing area of worm-gear drives. From the new alternative equation, the equations of the boundaries of the three-dimensional meshing area and the limiting line on the worm surface that distinguishes the non-undercut area and the undercut area are derived. [S1050-0472(00)01302-7]
A Genetic Algorithm for Topological Characteristics of Kinematic Chains
Authors: Rao A. C.
Published: July 2002

A genetic algorithm for testing isomorphism among kinematic chains and to select the best frame and input links is presented. The computational effort involved is minimum and the method is unique as it satisfies both the necessary and sufficient requirements. Fitness of a binary string corresponding to a link is indicative of its design parameters. Consequently the fitness of a chain indicates the number of design parameters active in motion generation. Chains are compared for function generation on the basis of the ‘fitness’ of first generation and second generation ‘fitness,’ etc., in that order. [S1050-0472(00)00801-1]
A Three-Dimensional Inverse Problem of Estimating the Surface Thermal Behavior of the Working Roll in Rolling Process
Authors: Hsu Pao-Tung , Yang Yue-Tzu , Chen Cha’o-Kuang
Published: July 2002

A three-dimensional inverse analysis utilizes a different perspective to estimate the surface thermal behavior of the working roll in rolling process. The inverse analysis is based on the temperature reading taken inside the roll at several different locations. At the beginning of the study, finite-difference methods are employed to discretize the problem domain and then a linear inverse model is constructed to identify the boundary conditions. The present approach is to rearrange the matrix forms of the differential governing equations and estimate the surface unknown conditions of the working roll. Then, the linear least-squares method is adopted to find the solution. The advantages of this proposed inverse analysis method are that no prior information is needed regarding the functional form of the unknown quantities, no initial guess need be used and the numbers of iterations for calculation process is limited to one. The results show that only few measuring points are sufficient to estimate the boundary conditions when measurement errors are neglected. When measurement errors are considered, more measuring points are needed in order to increase the congruence of the estimated results to exact solutions. [S1087-1357(00)70201-2]
Mechanics of a Porous Web Moving Over a Cylindrical Guide
Authors: Mu¨ftu¨ Sinan , Cengiz Altan M.
Published: July 2002

A model for analyzing the interfacial conditions of a porous web moving over a cylindrical rigid guide is presented. This problem is different from the classical foil bearing problem due to the fact that the air can diffuse through the porous web itself. A micromechanics model is used to express the web porosity as a function of the fiber volume fraction of the web. Darcy’s law is used to account for the air flow and pressure drop across the web thickness, and a new modified Reynolds equation is derived to model the airflow in the web-guide interface. The porous web is modeled as a moving cylindrically curved beam, and the solid-body contact between the web and the guide is modeled using an asperity compliance function. The governing equations are nondimensionalized and important nondimensional parameters are identified. The coupled nonlinear steady-state system is solved using a modified Newton-Raphson algorithm. The traction characteristics of the web are presented for different porosity levels, asperity height, and compliance. [S0742-4787(99)00102-8]
Joint and Cross Acceptances for Cross-Flow-Induced Vibration—Part I: Theoretical and Finite Element Formulations
Authors: Au-Yang M. K.
Published: July 2002

The theoretical development of the acceptance integral method to estimate the random vibration of structures subject to turbulent flow is critically reviewed and put onto a firm mathematical basis. Closed-form solutions for the joint acceptances for cross-flow-induced vibration of one-dimensional structures are derived for two special cases of spring-supported and simply supported beams. These are used to check results from a finite element formulation of the acceptance integrals for one-dimensional structures with arbitrary boundary conditions, and for arbitrary correlation lengths. Agreements between the finite element and closed-form solutions are excellent. [S0094-9930(00)02303-9]
Linear Time-Varying Dynamic Systems Optimization via Higher-Order Method: A Sub-Domain Approach
Authors: Xu Xiaochun , Agrawal Sunil K.
Published: July 2002

A new procedure for optimization of linear time-varying dynamic systems has been proposed that uses transformations to embed the dynamic equations explicitly into the cost functional. This leads to elimination of Lagrange multipliers and characterization of the optimality equations by high-order differential equations in the same number of variables as number of control inputs. This procedure requires that the transformation matrix be nonsingular at all time within the domain. This paper extends this procedure to problems where a single nonsingular transformation matrix does not exist over the entire domain. In this paper, the time domain is partitioned into intervals such that a nonsingular transformation exists over each interval. The transformations are used to embed the dynamic equations into the cost functional. Variational analysis of the unconstrained cost functionals results in the optimality equations, which are solved efficiently by weighted residual methods. [S0739-3717(00)00601-2]
InSb(110) by XPS
Authors: Poirier D. M. , Weaver J. H.
Published: July 2002

XPS spectra of the InSb(110) surface of a single crystal cleaved in situ were recorded (Accession #00105). For comparison, spectra were acquired for the same surface exposed to air for 60 min (Accession #00106). The electronic record includes the 4d, 3d, and MNN regions for In and Sb, as well as the valence band region.
Nordstrandite (Al(OH)3) by XPS
Authors: Rotole John A. , Sherwood Peter M. A.
Published: July 2002

The XPS spectra of Nordstrandite were collected with a VSW HA150 using monochromatic Al Kα x-radiation. Monochromatic radiation provides a distinct clarity to the peak structure in the valence band of Nordstrandite due to the absence of interfering x-ray satellites from the intense O 2s region. Variations in the intensities and peak separation of the two-peak structure in the valence bands of the oxides, hydroxides, and oxyhydroxides of aluminum allow one to distinguish between these compounds. The valence band, survey, and the Al 2s, Al 2p, O 1s, and C 1s core levels are reported.
Preparation and characterization of clean, single-crystalline YHx films (0⩽x⩽2.9) on W(110)
Authors: Hayoz J. , Pillo Th. , Bovet M. , Züttel A. , Guthrie St. , Pastore G. , Schlapbach L. , Aebi P.
Published: July 2002

Yttrium can be loaded with hydrogen up to high concentrations causing dramatic structural and electronic changes of the host lattice. We report on the preparation of clean, single-crystalline YHx films (0⩽x⩽2.9). The films have been characterized in situ combining angle-resolved photoelectron spectroscopy (ARPES) and low energy electron diffraction. Direct Y dihydride growth, i.e., Y evaporation under a H2 partial pressures of ≈5×10−6 mbar at 500 K on W(110), is the most convenient starting point for the preparation of clean single-crystalline Y hydride films covering H concentrations from the “clean metal” (x≈0) up to the lower boundary of the pure trihydride phase (x≈2.9). Upon annealing Y dihydride films the desired H concentration can be adjusted within the α-phase or the (α+β) two-phase regime. On the other hand, the extension of our photoelectron spectrometer with an homemade ultrahigh vacuum (UHV) compatible hydrogenation system allows to induce the transition from Y dihydride to Y trihydride within a few minutes. The hydrogenation system combines a high-pressure reaction cell with hydrogen permeation through a Pd–24%Ag tube. The overall design is such that the sample never gets in contact with non-UHV compartments. For direct Y dihydride growth on W(110) two equally populated face-centered- cubic(111) domains rotated by 180° with respect to each other are observed. In the α- and γ-phase the Y atoms form a hexagonal-close-packed(0001) oriented lattice. Furthermore, the previously established model for in situ H concentration estimation in Y [J. Hayoz et al., Phys. Rev. B 58, R4270 (1998)] is extended successfully from the α to β to the β to γ-phase transition. Ultraviolet photoemission spectroscopy data unequivocally reveal the opening of a gap extending as far as 1 eV below EF for normal electron emission upon the phase-transformation from Y dihydride to Y trihydride. It also appears that the H absorption rate strongly depends on the H2 purity. Our experimental results demonstrate the capability of this setup for in situ preparation and investigations on the geometrical and electronic structure of Y hydride films and, more generally, rare-earth hydride films using ARPES.
Pulse-time-modulated inductively coupled plasma etching for high-performance polysilicon patterning on thin gate oxides
Authors: Ohtake Hiroto , Noguchi Ko , Samukawa Seiji , Iida Hidekazu , Sato Arthur , Qian Xue-yu
Published: July 2002

Pulse-time-modulated inductively coupled plasma with HBr gas can provide highly selective, high etching rate, charge-free poly-Si metal–oxide–semiconductor field effect transistor etching. We observed that, when the HBr plasma is cycled ON and OFF at a rate of a few tens of microseconds, the etching and deposition on the substrate surface can be controlled precisely. The use of pulsed plasma can also reduce charge buildup because the electron temperature decreases significantly during the pulse-OFF time. As a result, poly-Si can be etched with extremely high selectivity (relative to the resist and gate oxide), and neither trenching of the gate oxide nor topography-dependent charging occurs.
Detailed Calculations of the Number of Distinct Sites Visited in Random Walk on Several Two-Dimensional Substrate Lattices
Authors: Pocker D. J. , Hruska S. J.
Published: July 2002

Calculations of the number of distinct sites visited in random walk on six physically different substrate lattices are carried out with exact, Monte Carlo and approximate analytical techniques. The fraction, λ, of the total possible sites, m, which are distinct is tabulated and plotted for all useful m for four lattice geometries and for 10≤m≤1000 for two more. The validity of this single valued characterization is examined and found to be very good, especially for larger m. Plots of parameters for functional application of the results are given.
Investigation of Gas–Solid Reactions by Modulated Molecular Beam Mass Spectrometry
Authors: Jones R. H. , Olander D. R. , Siekhaus W. J. , Schwarz J. A.
Published: July 2002

An apparatus for the study of gas-solid reactions which produce gaseous reaction products is described. The reactant gas contacts the solid as a molecular beam travelling in vacuum. Gaseous reaction products are monitored by a mass spectrometer as they are emitted from the surface. The technique relies heavily upon modulation of the molecular beam to improve the signal-to-noise ratio. In addition, chopping of the reactant beam induces modulation at the same frequency in the reaction products and the phase differences between these two signals contains important kinetic information. Methods of comparing theoretical models of the surface processes with the phase and amplitude information provided by the experiment are presented.