bluuebunny/crossref_metadata_2025_split huggingface dataset:
ULSLEA: A Limit Equilibrium Procedure to Determine the Ultimate Limit State Loading Capacities of Template-Type Platforms
Authors: Bea R. G. , Mortazavi M. M. 
Published: February 2008

AbstractDuring the past three decades, an immense amount of effort has been devoted to development of sophisticated computer programs to enable the assessment of storm wind, wave, and current loadings and the ultimate limit state capacity characteristics of conventional, pile-supported, template-type offshore platforms (Billington et al, 1993; Frieze, 1993; Hellan et al., 1993, 1994). These programs require high degrees of expertise to operate properly, are expensive to purchase and maintain, and require large amounts of manpower and time to complete the analyses. Due to the sophistication of these programs, experience has shown that it is easy to make mistakes that are difficult to detect and that can have significant influences on the results. This paper summarizes the second phase of development and verification of simplified procedures to evaluate environmental loadings and ultimate limit state lateral loading capacities of template-type platforms. Reasonable simplifications and high degrees of user friendliness have been employed in development of the software to reduce the engineering effort, expertise, and costs associated with the analyses. The computer program that has been developed to perform the simplified analyses has been identified as ULSLEA (ultimate limit state limit equilibrium analyses) (Mortazavi and Bea, 1994).
Reliability of Welded Structures Containing Fatigue
Cracks
Authors: Lanning D. , Shen M.-H. H. 
Published: February 2008

Abstract
This study investigates the reliability of a cracked fillet welded T-joint typically found in offshore structures. A formulation for the aspect ratio (a/c) of a propagating semi-elliptical fatigue crack located at the toe of the weld is developed using Newman and Raju’s stress intensity factor for a cracked flat plate in conjunction with a weld magnification factor. The reliability in terms of fatigue lifetime is then calculated using the aspect ratio and Paris’s law of crack propagation with both fracture toughness and elastic-plastic failure criteria. The variation in crack aspect ratio in the T-joint is compared to that in a cracked flat plate, and examples are provided of reliability calculations for tension and bending loads.
An Atlas of the Wave-Energy Resource in Europe
Authors: Pontes M. T. , Athanassoulis G. A. , Barstow S. , Cavaleri L. , Holmes B. , Mollison D. , Oliveira-Pires H. 
Published: February 2008

Abstract
An atlas of the European offshore wave energy resource, being developed within the scope of a European R&D program, includes the characterization of the offshore resource for the Atlantic and Mediterranean coasts of Europe in addition to providing wave-energy and wave-climate statistics that are of interest to other users of the ocean. The wave data used for compiling the Atlas come from the numerical wind-wave model WAM, implemented in the routine operation of the European Centre for Medium Range Weather Forecasts (ECMWF), in addition to directional wave measurements from the Norwegian offshore waters.
The Additive Ep-Condition and the Critical Scuffing Limit for
Rolling-Sliding
Authors: Escobar-Jaramillo Enrique F. 
Published: February 2008

Abstract
This paper introduces a new model for the scuffing load capacity in heavily loaded contacts, concerned specifically with the effects of EP-additive oils. The scuffing limit for the additive condition will be closely related to the initial additive-free case, using the calculation method of Blok, solely on a referential level. The process thermodynamics involved at a friction contact will be related to a phenomenological integral relation, containing the necessary internal coordinate to describe the implicit dependence of the friction coefficient with time. The experimental response of the friction contact depends on a relaxant friction coefficient due to the additive effect. The simple calculation method requires only three input parameters for the prediction of the scuffing limit, and these can be obtained from a few experimental scuffing tests. All the tribology of the present scuffing model can be considered to be contained in a simple linear relationship, with the sliding speed as the dominant variable. The calculation criterion has shown to have predictive capability which agrees well with experiments.
Experimental Study of Long-Term Static Friction and Magnetic
Slider/Disk Interplanar Separation
Authors: Gerber C. T. , Bhushan B. , Gitis N. V. 
Published: February 2008

Abstract
Capacitance between a slider and disk was measured to relate slider/disk interplanar separation to static friction. The parallel plate capacitance formula was used to convert the capacitance into separation with a resolution of less than 1 nm. Separation and coefficient of static friction (stiction) were measured using assorted lubricant thicknesses with and without bonding on polished and textured disks. Separation was measured during contact start/stop (CSS) and long term slider dwell times, after which static friction was measured. Polished disks had high stiction events with smaller separations during and after the stiction event, unlike textured disks. Long-term dwell studies showed the coefficient of static friction and slider micro descent (decrease in interplanar separation) to be greatest with greater lubricant thickness and polished disks. Static friction and separation with bonded and unlubricated disks were time independent.
Internal Stresses in Contact of a Rough Body and a Viscoelastic Layered Semi-Infinite Plane
Authors: Goryacheva Irina , Sadeghi Farshid , Nickel David A. 
Published: February 2008

AbstractA model has been developed to investigate the effects of a rough elastic indenter in sliding contact with a viscoelastic layer bonded to an elastic semi-infinite plane. The viscoelastic layer is modeled as a one-dimensional Maxwell solid (small strain) while the substrate of the semi-infinite plane is modeled as a two-dimensional elastic half plane. The Fredholm integral equation of the second kind was obtained to determine the contact stresses. The results indicate that the viscoelastic properties of the layer and the velocity of the indenter significantly affect the contact pressure and internal stress distributions. The viscoelastic layer causes the pressure and internal stresses to become nonsymmetrical. High asperity densities reduce the amplitude of maximum shear stress at a fixed depth below the surface. Results are also presented for various coefficients of friction.
The Behavior of an Elastohydrodynamic Lubricant at Moderate Pressures
and High Shear Rates
Authors: Zhang Y. , Ramesh K. T. 
Published: February 2008

Abstract
Knowledge of the behavior of lubricants over a wide range of pressures and shear rates is fundamental to an understanding of elastohydrodynamic (EHD) lubrication. The mechanical properties of elastohydrodynamic lubricants have been measured by a number of researchers under the conditions of low pressures and low shear rates, as well as under high pressures and high shear rates. This paper presents experimental results for the synthetic lubricant 5P4E subjected to moderate pressures (60 MPa to 700 MPa) and high shear rates (105 s−1) using the technique of pressure-shear plate impact. Thin layers (25 μm thick) of the lubricant are confined between two hard elastic plates; the assembly is subjected to impact by a parallel plate in a manner designed to induce both compression and shear loading. For approximately 1 μs the compressed lubricant is subjected to a simple shearing motion; during that time, continuous records of the shear stress and shear rate are obtained using laser interferometry. Three test configurations were used in order to cover the pressure range, and special techniques were developed for preparing the specimen sandwich. The pressure range covered includes both the liquid and glassy states of the lubricant. The results show that a limiting shear stress model is an appropriate model for lubricant behavior under these conditions. The experimental results also show little change in the lubricant shearing behavior across the glass transition.
Roughness Influence on Turbulent Flow Through Annular Seals Including
Inertia Effects
Authors: Lucas Victor , Bonneau Olivier , Frêne Jean 
Published: February 2008

Abstract
An analysis is developed to calculate the static and dynamic characteristics for a rough seal that includes inertia effects. The method is detailed for a seal made up of a rough stator and a smooth rotor, a configuration which presents some peculiarities modifying the pattern of the model of turbulence where roughness effects and flow equations are included. A geometry with two identically roughened surfaces can be considered as a special case of the first one. In an earlier study, we developed a model of turbulence built from Prandtl's relation and Van Driest's mixing length method including roughness effects. This model is used to calculate the zeroth-order coefficients of turbulence kx, kz, the Couette velocity ucr for a roughened stator as well as the inertia coefficients. These coefficients derive from the numerical solution of the Generalized Couette Flow. The effects of inertia forces in the film are taken into account in an integrated way according to the film height and are expressed versus the mean velocity. Flow equations are derived from Navier-Stokes’ equations and from the continuity equation for incompressible flows. An analytical perturbation of the flow parameters leads to a set of zeroth-order and first-order equations. The integration of nonlinear zeroth-order equations leads to the steady state solution which permits the calculation of the seal leakage and static load. Dynamic stiffness, damping and added mass coefficients are obtained from the integration of the linear first-order equations. Comparisons are made with the results of the Bulk-flow theory applied to rough seals.
Ultra-Thin Gas Squeeze Film Characteristics for Finite Squeeze Numbers
Authors: Matsuda R. , Fukui S. 
Published: February 2008

AbstractUltra-thin gas squeeze film characteristics for finite squeeze numbers are examined by solving the molecular gas film lubrication (MGL) equation, which has a similar form to the conventional Reynolds-type lubrication equation but contains a flow rate coefficient and is valid for arbitrarily small spacings or for arbitrary Knudsen number. We quantitatively clarify by numerical computations that at thin film conditions below several micrometers, pressures generated by squeeze motions are lower than those of continuum flow case and therefore load-carrying capacities are smaller and depend upon film thickness because of the molecular gas effect. For example when the squeeze number is 10 and excursion ratio is 0.5, the load-carrying capacity at 0.1 μm is about one tenth of that at 1 μm.
The Rotor Dynamic Coefficients of Eccentric Mechanical Face
Seals
Authors: Wileman J. , Green I. 
Published: February 2008

Abstract
The Reynolds equation is extended to include the effects of radial deflection in a seal with two flexibly mounted rotors. The resulting pressures are used to obtain the forces and moments introduced in the axial and angular modes by the inclusion of eccentricity in the analysis. The rotor dynamic coefficients relating the forces and moments in these modes to the axial and angular deflection are shown to be the same as those presented in the literature for the concentric case. Additional coefficients are obtained to express the dependence of these forces and moments upon the radial deflections and velocities. The axial force is shown to be decoupled from both the angular and radial modes, but the angular and radial modes are coupled to one another by the dependence of the tilting moments upon the radial deflections. The shear stresses acting upon the element faces are derived and used to obtain the radial forces acting upon the rotors. These forces are used to obtain rotor dynamic coefficients for the two radial degrees of freedom of each rotor. The additional rotor dynamic coefficients can be used to obtain the additional equations of motion necessary to include the radial degrees of freedom in the dynamic analysis. These coefficients introduce additional coupling between the angular and radial degrees of freedom, but the axial degrees of freedom remain decoupled.
Friction and Wear of Metal Particle, Barium Ferrite and Metal
Evaporated Tapes in Rotary Head Recorders
Authors: Patton Steven T. , Bhushan Bharat 
Published: February 2008

Abstract
The friction and wear mechanisms of particulate (metal particle and barium ferrite) and metal evaporated (ME) magnetic tapes were investigated. We conducted tests on these tapes in contact with metal-in-gap (MIG) video heads, using a rotary head recorder in the still (pause) mode. We measured signal degradation and friction during the tests. We conducted chemical and surface analyses of the interface components after the tests. We found discernible differences between the tribological behavior of particulate tapes, and that of the ME tape. The particulate tapes exhibited a more stable friction and head output than the ME tape. We attributed this to a cleaner contact region, due to effective action of the head cleaning agents (HCAs) found in the particulate tapes. The particulate tapes exhibited wear lifetime longer by an order of magnitude, than that of the ME tape. Mild continuous adhesive wear occurred on particulate tapes followed by catastrophic failure. Tape fatigue possibly led to the catastrophic failure. On the ME tape surface, damage initiated at high points or bumps, which resulted in localized delaminations of the tape coating. This led to a catastrophic removal of the entire magnetic coating over the rubbing track. The major difference between the particulate and ME tapes was that signal dropouts concurrent with increases in friction, which resulted from debris accumulation on the video head, preceded the catastrophic failure in the case of ME tapes. We investigated the running-in process of the video head. We found that the durability of a tape and the initial head output increased, and the initial friction force on a tape decreased, as the head ran-in with the tape. We attributed this result to the tape forming a favorable contour on the head rubbing surface. Deposits on the head surface consisted of binder for the particulate tapes, and lubricant and the magnetic coating for ME tape. Tape materials transferred preferentially to the recessed metal core and the recessed glass of the MIG head.
Thermal Analysis of Noncircular Bearings
Authors: Hussain A. , Mistry K. , Biswas S. , Athre K. 
Published: February 2008

AbstractThe present work is on prediction of temperature distribution in noncircular journal bearings and the surrounding solids. Three forms are studied, viz. two-lobe, elliptical and orthogonally displaced bearings. For comparison purposes, a circular bearing with two different groove locations is analyzed. The investigation includes the effects of recirculation and oil mixing at the grooves. The cavitation zone has also been investigated. The work is based on a two-dimensional treatment following McCallion’s approach. The results are presented for various geometries of journal bearing configuration, including the conventional circular bearing.
A Numerical Three-Dimensional Model for the Contact of Rough Surfaces
by Variational Principle
Authors: Tian Xuefeng , Bhushan Bharat 
Published: February 2008

Abstract
A new numerical method for the analysis of elastic and elastic-plastic contacts of two rough surfaces has been developed. The method is based on a variational principle in which the real area of contact and contact pressure distribution are those which minimize the total complementary potential energy. The present variational approach guarantees the uniqueness of the solution of the contact problem and significantly reduces the computation time as compared with the conventional matrix inversion method, and thus, makes it feasible to solve 3-D contact problem with large number of contact points. The model is extended to elastic-perfectly plastic contacts. The model is used to predict contact statistics for computer generated surfaces.
A Generalized Non-Newtonian Fluid Model Incorporated Into
Elastohydrodynamic Lubrication
Authors: Wolff R. , Kubo A. 
Published: February 2008

Abstract
A generalized Reynolds equation for the non-Newtonian fluid, which can incorporate most of the published rheological models, is proposed. The solution of the isothermal EHL line contact lubricated by a non-Newtonian fluid is obtained by applying the Newton-Raphson method. The results of an isothermal non-Newtonian EHL line contact model with different rheological laws and the results of a thermal Newtonian EHL model are presented. Under low load and high rolling velocity conditions, the thermal effects caused by slip have a greater influence on the film shape and pressure distribution than the non-Newtonian effects. For low slip and under heavy load conditions the non-Newtonian behavior of fluid significantly influences the traction coefficient, while thermal effects have a great influence on the traction in case of high slip. The comparison between numerical and experimental results shows that the nonlinear viscous Eyring model overestimates the traction coefficient when high viscosity oil is subjected to a heavy load and low slip conditions. In this case, only the visco-plastic models can predict the traction value. The visco-elastic behavior of the fluid is important at very low slip conditions and it can slightly reduce the traction value.
Low Speed Mixed Lubrication of Bulk Metal Forming
Processes
Authors: Wilson W. R. D. , Chang Der-form 
Published: February 2008

Abstract
A simple analysis for the lubrication of saw-tooth surfaces with longitudinal lay under conditions of high fractional contact area is developed. This is then coupled with Wilson and Sheu’s asperity flattening model to treat the mixed lubrication of a bulk metal forming process (rolling). It is shown that, even under low speed conditions where the inlet zone does not generate significant hydrodynamic pressures, relatively high hydrodynamic pressures can be generated in the work zone. This explains the persistence of hydrodynamic effects noted in low speed experiments.
Life Prediction in High-Temperature Structural Materials
Authors: Jaske C. E. 
Published: February 2008

AbstractLife prediction methods are required to assess the performance and safety of the structural materials used in engineering systems and components that operate at high temperatures. At high temperatures, materials are subject to time-dependent creep environmental degradation, as well as cycle-dependent fatigue degradation. The life prediction methods must account for all of these degradation mechanisms and their possible interactions. The purpose of this paper is to review the methods that are used predict the creep and fatigue life of structural materials. Traditional methods that have been used to predict the life of structural materials are based on the initiation of a significant crack; whereas more recent methods employ fracture mechanics to predict life based on the growth of crack from some initial size to a critical size. Crack-growth-based life prediction methods are emphasized in this review.
Buckling of Unbalanced, Sandwich Panels With Titanium and GRP Skins
Authors: Kwon Y. W. , Murphy M. C. , Castelli V. 
Published: February 2008

AbstractAn unbalanced and asymmetric sandwich composite structure consisting of Titanium 6-4 and glass-reinforced plastic (GRP) skins with a phenolic honeycomb core is being considered for construction of a surface ship mast which will enclose critical shipboard equipment. Stability of the structure is one of the major concerns in the design process. This research focuses on analytical and experimental studies of an unbalanced composite sandwich beam subjected to a compressive axial load. The failure load (i.e., peak load) and failure mode of each skin material and the sandwich construction were measured at the laboratory. An analytical model was developed for predicting the failure load of the unbalanced and asymmetric sandwich composite configuration, including the transverse shear energy of the core material. The experimental data agreed very well with analytical prediction. Postbuckling failure, as well as residual strength after initial failure, were also studied.
Stress Analysis in Composite Hollow Cylinders due to an Asymmetric Temperature Distribution
Authors: Zibdeh H. S. , Al Farran J. M. 
Published: February 2008

AbstractA solution is presented for the stresses and displacements in an orthotropic, hollow, circular cylinder subjected to asymmetric temperature distribution at the outer surface and heat convection into a medium at zero reference temperature at the inner surface. Assuming temperature-independent material properties, the heat conduction equation in cylindrical coordinates is solved for a single and multilayer cylinders. Results of temperature analysis along with linear elasticity theory are used to obtain the required thermal stresses and displacements. Numerical results are given for a typical fiber-reinforced composite material where fibers in each layer are oriented axially or circumferentially. The results show that the response of the cylinder is sensitive to changes in thickness, orientation of fibers in each layer, number of layers, and stacking sequence.
J Estimation Method for a Semi-Elliptical Surface
Flaw in a Cylinder
Authors: Yoon K. K. , Killian D. E. 
Published: February 2008

Abstract
With the emergence of readily available simple J solutions for various types of structures through J estimation techniques, J-integral-based elastic-plastic fracture mechanics has become a common tool for analyzing ductile materials. This paper presents elastic-plastic solutions for semi-elliptical surface flaws of four different crack depths. Solutions are developed from a series of finite element analyses using the ABAQUS computer program with a deformation plasticity material constitutive law. Although the solutions are directly applicable to a single set of Ramberg-Osgood material parameters, they may be extended to include various amounts of strain hardening by a ratioing technique utilizing calibration functions from the EPRI handbook for continuous flaws. This paper addresses cylindrical structures loaded by internal pressure, and excludes any consideration of thermal loadings. Elasticplastic J solutions, determined for pressures up to 5000 psi (12700 Pa), or twice the design pressure, depart from plastic-zone-corrected linear elastic predictions at approximately 3000 psi (7620 Pa) pressure. The h1 plastic calibration functions derived in this paper are limited to the point of greatest crack depth in 6:1 aspect ratio semi-elliptical inside surface flaws in cylindrical pressure vessels.