bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fracture Toughness of Freshwater Ice—Part II: Analysis and
Micrography
Authors: Weber L. J. , Nixon W. A. 
Published: February 2008

Abstract
Experiments have been performed to determine the effect of loading rate and temperature on the fracture toughness of freshwater ice. A first paper (Weber and Nixon, 1996) presents the experimental technique and results, while this paper focuses on discussion of the crack tip process zone and fracture surface micrography. A simple method to estimate the size of the process zone will be presented. Also, fracture surface micrography will be used to interpret the results of the temperature experiments by considering evidence of dislocation activity in preferentially oriented grains.
The Propagation of Wind Errors Through Ocean Wave
Hindcasts
Authors: Holthuijsen L. H. , Booij N. , Bertotti L. 
Published: February 2008

Abstract
To estimate uncertainties in wave forecast and hindcasts, computations have been carried out for a location in the Mediterranean Sea using three different analyses of one historic wind field. These computations involve a systematic sensitivity analysis and estimated wind field errors. This technique enables a wave modeler to estimate such uncertainties in other forecasts and hindcasts if only one wind analysis is available.
Spectral Fatigue Analysis of Shallow Water Jacket
Platforms
Authors: Bishop N. W. M. , Feng Q. , Schofield P. , Kirkwood M. G. , Turner T. 
Published: February 2008

Abstract
The spectral analysis approach is a very elegant and computationally efficient method of analyzing the fatigue life of offshore jacket platforms. The primary limitation of the approach is that it assumes linearity of both the structural system and the wave-loading mechanism. The approach is now widely used for the analysis of deepwater, dynamically responsive platforms where nonlinearities are usually not serious. There are also advantages associated with using the approach for shallow water platforms although nonlinearities then become significant, particularly the wave-loading mechanism. Various methods have been proposed to enable the spectral method to be used for some nonlinear situations, including a new approach which uses the Longuet-Higgins wave height-period joint probability density function in order to obtain a better linearization technique. This linearization process is associated with the particular wave heights chosen for producing the transfer functions. The new approach provides a better method for choosing the appropriate height of each so-called base wave case. In order to verify the new approach, a time series analysis, including wave-loading nonlinearities, has been adopted to obtain a reference fatigue life. The sea surface elevation spectrum has been decomposed into a set of equivalent harmonic components. The water particle velocities and accelerations were then individually evaluated and the appropriate (Morison’s) wave loading was computed for each time step in the sea surface time history. The structural stress response time history was then calculated, from which a fatigue life estimate was obtained. This paper presents the results obtained using this new approach, as well as comparative results obtained using the deterministic, spectral, and time domain approaches applied with a representative sea state. The results show that the deterministic-spectral method has a considerable amount of potential, especially for new design work where weight savings and/or increased confidence levels may be achieved.
Risk Acceptance Criteria for Temporary Phases
Authors: Vinnem J. E. 
Published: February 2008

Abstract
The full life cycle approach to risk acceptance is proposed as the basis for establishing of acceptance criteria for the temporary phases, i.e., onshore and offshore construction as well as installation. The background for such criteria is discussed, as well as evaluations that may be used to formulate risk acceptance criteria in the construction and installation phases. The criteria are focused on personnel safety. Environmental spill protection and protection of assets are also addressed, but less extensively. FAR or AIR values are used to express tolerable personnel safety, whereas the acceptability of exposure of the investment is expressed in terms of acceptable probabilities of accidents with significant effect on the project time schedule, i.e., the possibility to delay significantly the start-up of the production phase. The approach is based on an ALARP principle.
On Irregular, Nonlinear Waves in a Spread Sea
Authors: Jonathan P. , Taylor P. H. 
Published: February 2008

Abstract
Optimal design and reassessment of offshore structures requires a good understanding of the ocean environment. The motion of the sea surface can be viewed as a three-dimensional, nonlinear stochastic process in time. In order to characterize the wave environment adequately, we need to model its random, nonlinear, and spread nature. In this paper, we address: • the expected shape of a wave near a crest or trough, • the expected shape of the ocean surface at one point, given a crest at a different point, • an efficient method to incorporate nonlinear effects within linear wave simulations, • the magnitude of wave nonlinearity as a function of wave amplitude. Detailed comparison of theory and full-scale offshore measurements at the Shell Expro Tern platform show good agreement.
Fatigue Reliability of TLP Tether Systems
Authors: Hovde G. O. , Moan T. 
Published: February 2008

Abstract
The tension leg platform (TLP) concept is considered to be economically competitive with other offshore production concepts in deepwater locations. The critical part of this concept regarding structural failure is the tether system, in which fatigue is an important failure mode. The present paper presents a computational efficient and general probabilistic procedure for estimating the fatigue reliability of the TLP tether system. Two crack growth rate models of single crack sites are applied. Among uncertainties accounted are those in the long-term stochastic load process, the fatigue strength, and the initial crack sizes.
Non-Gaussian Extreme Waves in the Central North Sea
Authors: Skourup J. , Hansen N.-E. O. , Andreasen K. K. 
Published: February 2008

Abstract
The area of the Central North Sea is notorious for the occurrence of very high waves in certain wave trains. The short-term distribution of these wave trains includes waves which are far steeper than predicted by the Rayleigh distribution. Such waves are often termed “extreme waves” or “freak waves.” An analysis of the extreme statistical properties of these waves has been made. The analysis is based on more than 12 yr of wave records from the Mærsk Olie og Gas AS operated Gorm Field which is located in the Danish sector of the Central North Sea. From the wave recordings more than 400 freak wave candidates were found. The ratio between the extreme crest height and the significant wave height (20-min value) has been found to be about 1.8, and the ratio between extreme crest height and extreme wave height has been found to be 0.69. The latter ratio is clearly outside the range of Gaussian waves, and it is higher than the maximum value for steep nonlinear long-crested waves, thus indicating that freak waves are not of a permanent form, and probably of short-crested nature. The extreme statistical distribution is represented by a Weibull distribution with an upper bound, where the upper bound is the value for a depth-limited breaking wave. Based on the measured data, a procedure for determining the freak wave crest height with a given return period is proposed. A sensitivity analysis of the extreme value of the crest height is also made.
Dynamic Analysis for the Design of CALM System in Shallow and Deep
Waters
Authors: Hwang Y.-L. 
Published: February 2008

Abstract
This paper presents a time domain analysis approach to evaluate the dynamic behavior of the catenary anchor leg mooring (CALM) system under the maximum operational condition when a tanker is moored to the terminal, and in the survival condition when the terminal is not occupied by a tanker. An analytical model, integrating tanker, hawser, buoy, and mooring lines, is developed to dynamically predict the extreme mooring loads and buoy orbital motions, when responding to the effect of wind, current, wave frequency, and wave drift response. Numerical results describing the dynamic behaviors of the CALM system in both shallow and deepwater situations are presented and discussed. The importance of the line dynamics and hawser coupled buoy-tanker dynamics is demonstrated by comparing the present dynamic analysis with catenary calculation approach. Results of the analysis are compared with model test data to validate the mathematical model presented.
Use of Numerical Wind-Wave Models for Assessment of the Offshore Wave
Energy Resource
Authors: Pontes M. T. , Barstow S. , Bertotti L. , Cavaleri L. , Oliveira-Pires H. 
Published: February 2008

Abstract
In the last two decades the performance of numerical wind-wave models has improved considerably. Several models have been routinely producing good quality wave estimates globally since the mid-1980s. The verifications of wind-wave models have mainly focused on the evaluation of the error of the significant wave height Hs estimates. However, for wave energy purposes, the main parameters to be assessed are the wave power Pw and the mean (energy) period Te. Since Pw is proportional to Hs2 Tc, its expected error is much larger than for the single-wave parameters. This paper summarizes the intercomparison of two wind-wave models against buoy data in the North Atlantic and the Mediterranean Sea to select the most suitable one for the construction of an Atlas of the wave energy resource in European waters. A full verification in the two basins of the selected model—the WAM model implemented in the routine operation of the European Centre for Medium-Range Weather Forecasts—was then performed against buoy and satellite altimeter data. It was found that the WAM model accuracy is very good for offshore locations in the North Atlantic; but for the Mediterranean Sea the results are much less accurate, probably due to a lower quality of the input wind fields.
Friction, Temperature, and Wear Analysis for Ceramic Coated Brake
Disks
Authors: Watremez M. , Bricout J. P. , Marguet B. , Oudin J. 
Published: February 2008

Abstract
Coating adherence, friction coefficient, surface temperature, and wear mass loss are determined for a set of scale reduced steel brake disks on which NiCr cement based coatings and low conductivity subcoatings are plasma sprayed. The related pads are made of either sintered iron copper or sintered aluminum titanate. It is mainly shown that NiCr-Cr3C2 cermet coating on the disk, coupled with sintered aluminum titanate pad, leads to good damage resistance and stable friction coefficient in the simulation of high speed train braking. Low conductivity sublayers are also involved and it is found that temperatures in disc or pad may be also controlled.
Realistic Braking Operation Simulation of Ventilated Disk
Brakes
Authors: Floquet A. , Dubourg M.-C. 
Published: February 2008

Abstract
A three-dimensional numerical method for the prediction of transient temperatures reached during realistic braking operations in a ventilated disk brake assembly is presented in this paper. This Layered FFT-FEM numerical method (Fast Fourier Transform-Finite Element Method) takes advantage of the high Peclet number “skin effect” to decouple the moving boundary contact problem from the spatially periodic but non-axisymmetric cooling associated with the vents. The first problem is modeled according to the FFT-FEM method developed previously by the authors. This technique succeeded in using high Peclet numbers for axisymmetric moving solids submitted to general loading conditions. No numerical convergence problems are encountered and short computer time is required. The second problem is modeled according to traditional three-dimensional finite element techniques. The Layered FFT-FEM results are compared with analytical results. A braking operation is simulated for an industrial ventilated disk brake.
Experimental Study of Freely Alignable Journal Bearings—Part 1:
Static Characteristics
Authors: Tieu A. K. , Qiu Z. L. 
Published: February 2008

Abstract
The characteristics of two misaligned journal bearings were experimentally studied. A bearing test rig was developed. The experimental journal was freely alignable in two possibly misaligned journal bearings. In Part 1, the static characteristics, such as the distributions of oil film thickness and the pressure and temperature of two misaligned bearings, are measured; the relationships of eccentricity, attitude angle, and side flow to the Sommerfeld number are experimentally determined. In Part 2, the traditional harmonic excitation method is extended to estimate the sixteen dynamic force coefficients of two misaligned journal bearings. Sixteen force coefficients of two circular journal bearings, each with two axial grooves, are estimated and the threshold stable speeds are predicted. Various experimental errors and the uncertainty of the estimated coefficients are analyzed.
The Influence of Temperature on Failure Development in Steels Under
Transition to Seizure
Authors: Rapoport L. 
Published: February 2008

Abstract
Seizure phenomena in pin-on-disk tests have been studied for “soft” and “hard” steel specimens. Differences in competing and dominant wear mechanisms under steady state friction have been preserved for “soft” and “hard” specimens in the region of transition to seizure or galling. Severe wear was observed for “soft” specimens under all loads tested, while adhesion and splitting off of wear particle conglomerates (microseizure) were identified for “hard” specimens. The contact temperature, calculated in accordance with the temperature model of plastically deformed contact spots (Kuhlmann-Wilsdorf), has appeared to be low for “soft” specimens and not sufficient for adhesion interaction. The effect of oxide films on the friction of “hard” specimens has been estimated in accordance with the temperature model for a coated semi-infinite body (Tian and Kennedy). The insulated oxide films on the surface of “hard” specimens create the “skin effect” and lead, therefore, to raising the temperature up to the temperature of adhesion interaction. Temperature instability of hard surfaces has been demonstrated to result from the “skin effect” and from a disturbance in equilibrium of formation and failure of oxide films. It has been shown that for “soft” specimens the prime cause of transition to seizure was the mechanical interlocking between the wear particles and the soft disk surface combined with mechanical instability, while for “hard” specimens the cause was temperature instability. A more realistic temperature model of the contact has been considered, which takes into account some competing wear mechanisms (oxidational wear, ploughing, delamination) and the effect of wear particles.
Experimental Study of Thermal Effects in Tilting-Pad Journal Bearings
at High Operating Speeds
Authors: Bouchoule C. , Fillon M. , Nicolas D. , Barresi F. 
Published: February 2008

Abstract
In this work, a test machine, experimental results and the comparison between theoretical TEHD results and experimental data are presented. The tested bearings are located in two speed increasing and reduction gearboxes (back-to-back test bed). The shaft is driven by a 1 MW motor. The bearing diameter and the bearing length are equal to 160 mm. The rotational speed varies from 2700 rpm (22 m/s) to 11,880 rpm (100 m/s). The applied load is up to 88,000 N. Temperatures in the bearing (film/pad interface, oil, pad and housing), power losses and oil flow are measured. The influence of the bearing design and of the pivot position on the pad is analyzed.
Tribological Behavior of Amorphous Carbon Nitride Overcoats for
Magnetic Thin-Film Rigid Disks
Authors: Cutiongco Eric C. , Li Dong , Chung Yip-Wah , Bhatia C. Singh 
Published: February 2008

Abstract
Amorphous carbon nitride coatings of thickness of 5 and 30 nm were deposited onto 65 and 95 mm magnetic thin-film rigid disks surfaces using single-cathode and dual-cathode magnetron sputtering systems containing nitrogen-argon plasmas. Under optimum deposition conditions, amorphous carbon nitride coatings can be synthesized on ultrasmooth thin-film disks with no significant pinholes at thickness down to 5 nm, with hardness 22–28 GPa (compared to 7–12 GPa for amorphous carbon), and r.m.s. roughness as low as 0.25 nm. These amorphous carbon nitride coatings were shown to have better contact-start-stop performance and three-to-four times better pin-on-disk contact durability compared with amorphous carbon overcoats under identical testing conditions. Amorphous carbon nitride appears to be a promising candidate overcoat material for replacing amorphous carbon in the next-generation magnetic thin-film rigid disk systems.
On the Generalization of Thermohydrodynamic Analyses for Journal
Bearings
Authors: Khonsari M. M. , Jang J. Y. , Fillon M. 
Published: February 2008

Abstract
The results of extensive amount of thermohydrodynamic simulations are presented in the form of design charts for journal bearings. These charts enable one to evaluate the maximum temperature and an effective hearing temperature. Numerous examples are presented that show the applicability of these charts in predicting bearing performance parameters.
Generalized Boundary Interactions for Powder Lubricated Couette Flows
Authors: McKeague K. T. , Khonsari M. M. 
Published: February 2008

AbstractApplication of grain flow theories to powder lubrication of hydrodynamic bearings requires careful consideration of slip of the flow velocity at the boundaries together with appropriate formulation of the fluctuation (thermal) velocity conditions at the boundaries. Generalized boundary conditions that can be applied to a wide variety of surface and grain material characteristics are developed for a Couette flow configuration. The equations account for both the energy loss at the boundary due to inelastic grain-wall collisions and the energy supplied by the boundary due to collisional momentum supply. The predictions of the model are compared to a number of published results that are based on direct computer simulation of grain-grain collisions. The model’s flexibility is demonstrated by simulating the effects of unequal surface roughnesses.
An Analytical and Computational Investigation of High-Rate
Rheometry
Authors: Feng R. , Ramesh K. T. , Douglas A. S. 
Published: February 2008

Abstract
This paper examines a class of experimental techniques used to develop constitutive models for lubricants, by simulating the shearing of a thin lubricant layer while accounting for transient phenomena. The complete transient thermal problem with fully nonlinear constitutive relations is solved, and heat conduction is accounted for both in the lubricant layer and into the walls. Numerical simulations are used to examine the shear stress history, the velocity profile, and the temperature profile as functions of time. As a particular example, the high-rate torsional Kolsky bar rheometer (Feng and Ramesh, 1993) is simulated. The computations indicate that the Kolsky bar experiments, which are able to examine the time-histories of the stresses and of the motion, can he used to obtain material properties for lubricants at high shear rates. A full numerical analysis may be required to properly interpret some of the data available from the Kolsky bar experiments, since at longer times (greater than that associated with the peak shear stress) the thermal softening may dominate the response and the velocity field may become strongly inhomogeneous. The numerical simulations are performed using both rate-dependent and limiting stress constitutive laws, and the effects of the layer thickness and the rise time of the relative velocities are examined. The simulations show that the film thickness and the rise time of the relative velocities can have strong effects on the character of the solution when the transient phenomena are included in the analysis. The computations also demonstrate that highly inhomogeneous and even localized flows may occur within rheometers as a result of transient effects. The development of these flows depends on the layer thickness, the rise-time of the boundary velocity, the thermal boundary conditions, and the constitutive behavior of the lubricant.
Prediction of Equivalent Radial Loads for Tapered Roller
Bearings
Authors: Bailey Ted E. , Frayer Robert W. 
Published: February 2008

Abstract
Calculating the fatigue life of a tapered roller bearing has become a rather straightforward exercise thanks to the accumulation of rolling contact fatigue data and the subsequent development of formulation relating applied loading to bearing fatigue life. An integral part of the prediction process is to define an equivalent radial load (EQRL) by combining a bearing’s applied radial and thrust loading into a single entity. This paper reviews currently accepted formulation and offers a potentially more accurate alternative method for estimating the EQRL of a tapered roller bearing than does the current AFBMA standard.
Antiwear and Extreme-Pressure Action of Copper(II) Complex With Alkyl Phosphonic Acid Mono Alkyl Ester
Authors: Xiong Ren-Gen , Wang Hong , Zuo Jing-Lin , Liu Cai-Ming , You Xiao-Zeng , Dong Jun-Xiu , Zhang Pei 
Published: February 2008

AbstractThe copper(II) complex with alkylphosphonic acid monoalkyl ester (CuAMP) was synthesized, and its structure shown to be laminar on the basis of fast atom bombardment mass spectroscopy (FABMS). The extreme-pressure, antiwear and antiseizure performance of CuAMP was assessed using a four-ball machine. The results showed that CuAMP exhibits better extreme-pressure and antiwear properties than tricresyl phosphate. Based on the results of surface analysis, the antiwear action mechanism of CuAMP is discussed.
Squeeze Film Force Modeling for Large Amplitude Motion Using an
Elliptical Velocity Profile
Authors: Han Yingke , Rogers R. J. 
Published: February 2008

Abstract
With the aim of seeking a more reasonable solution for the squeeze film force for large amplitude motion with low viscosity fluids, an elliptical velocity profile and the corresponding squeeze film force equations are derived for a two dimensional rectangular plate model using three different approximation methods. Through comparisons with existing theoretical studies which use parabolic velocity profiles for moderate to large Reynolds numbers, it is shown that the squeeze film model using the elliptical profile may be closer to reality. The force level of the dominant temporal inertia component using the elliptical profile (with either the iterative or the energy methods) is between that obtained using the traditional parabolic profile with the momentum method and that obtained with either the iterative or the energy methods.
Friction Model of Thin Solid Film Lubrication
Authors: Zhang Xianhua , Kato Koji 
Published: February 2008

Abstract
Based upon previous results for thin solid film lubrication, a contact model has been proposed which can describe the physical essence of the steady-state friction condition. By using this contact model, a theoretical calculation method has been established. Good agreement between theoretical results and experimental results obtained for tribo-coatings shows that this theory can be used for practical application to obtain and maintain good solid lubrication.
Flow-Induced Vibration of Tubes in Cross-Flow
Authors: Chen S. S. , Cai Y. , Zhu S. 
Published: February 2008

Abstract
This paper presents an unsteady-flow theory for flow-induced vibration of tubes in cross-flow. It includes a general description of motion-dependent fluid forces, characteristics of fluid-force coefficients, and mathematical models. Detailed results are presented for the constrained mode in the lift direction for various tube arrangements.