bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Global Approach of Thermal Effects Including Pad Deformations in
Tilting-Pad Journal Bearings Submitted to Unbalance Load
Authors: Fillon M. , Desbordes H. , Frêne J. , Chan Hew Wai C. 
Published: February 2008

Abstract
The purpose of this paper is to study the response of a tilting-pad journal bearing submitted to an unbalance load. A pseudo-time transient analysis has been developed taking into account the effective viscosity of the lubricant, the thermal expansion of bearing elements, and the elastic pad deformations. At each time interval, and for each pad, an effective temperature of the film is deduced from an energy balance. First, a comparison between theoretical results and experimental data is presented for a four-shoe tilting-pad journal bearing subjected to a static load. Second, the influence of the thermal and pad flexibility effects on the journal center orbit, on the minimum film thickness and on the maximum pressure is studied for various unbalance loads. Both the viscosity variation and the operating clearances due to elastic and thermal deformations of the bearing elements have a great influence on the behavior of the bearing.
Turbulent Flow, Flexure-Pivot Hybrid Bearings for Cryogenic
Applications
Authors: San Andres Luis 
Published: February 2008

Abstract
The thermal analysis of flexure-pivot tilting-pad hybrid (combination hydrostatic-hydrodynamic) bearings for cryogenic turbopumps is presented. The advantages of this type of bearing for high speed operation are discussed. Turbulent bulk-flow, variable properties, momentum and energy transport equations of motion govern the flow in the bearing pads. Zeroth-order equations for the flow field at a journal equilibrium position render the bearing flow rate, load capacity, drag torque, and temperature rise. First-order equations for perturbed flow fields due to small amplitude journal motions provide rotordynamic force coefficients. A method to determine the tilting-pad moment coefficients from the force displacement coefficients is outlined. Numerical predictions correlate well with experimental measurements for tilting-pad hydrodynamic bearings. The design of a liquid oxygen, flexure-pad hybrid bearing shows a reduced whirl frequency ratio and without loss in load capacity or reduction in direct stiffness and damping coefficients.
Thermohydrodynamic Analysis of Tilting-Pad Journal Bearings Operating
in Turbulent Flow Regime
Authors: Bouard L. , Fillon M. , Frêne J. 
Published: February 2008

Abstract
A thermohydrodynamic analysis of tilting-pad bearing in turbulent flow regime is presented. Two tilting-pad journal bearings are studied. A local analysis of thermal turbulent phenomena is shown. The theoretical prediction of the maximum temperature decreases when the flow regime becomes nonlaminar and the decrease corresponding to higher power losses is explained using the velocity component profiles and the local heat flux in the film.
The Oscillating Fluid Mechanics Method (OFMM) for Studying Oil Film
Oscillation and Dynamic Characteristics of Journal Bearings
Authors: Zuoyi Chen , Yongzhong Sun 
Published: February 2008

Abstract
A new method to study oil film oscillation and to determine the unstable rotational speed and rotordynamic coefficients of bearings is presented. Differences between the new method called the Oscillating Fluid Mechanics Method (OFMM) and the previous method (quasi-steady state method) are discussed. Insufficiencies of the previous method are analyzed. The theory and calculational procedure of OFMM are given. Calculated results show that this new method provides significantly improved predictions.
Ball Bearing Dynamic Analysis Using Computer Methods—Part I:
Analysis
Authors: Meeks Crawford R. , Tran Long 
Published: February 2008

Abstract
An analytical ball bearing dynamics model was developed that rigorously models all of the significant kinematic, structural, and dynamic effects. The model can analyze bearings of any material combination for the races, balls and ball cage. This model analyzes the stresses and deflections of the loaded elements due to (1) preload, (2) external axial, radial and moment loads, (3) centrifugal and gyroscopic ball loads. A rigorous six-degree-of-freedom model of ball cage motions was developed to analyze ball and cage dynamics. The ball cage equations of motion were written in a rotating coordinate system, which greatly simplifies the equations, resulting in a highly efficient, but rigorous, model of bearing dynamics. A computer program was developed, incorporating the algorithms, to solve the multiple simultaneous quasi-static ball-to-race load equations using modified Newton-Raphson methods. The Lawrence Livermore Ode package (LSODA) is employed for numerical integration of the dynamic equations of motion. This method assures convergence, while controlling the accuracy of the calculations as a function of computer run time and automatically selects the appropriate integration method for stiff and non-stiff system of ODE. The program analyzes ball and cage motions in time domain, wear life, fatigue life, lubricant film effects, ball-to-cage forces, torque noise and many other bearing parameters.
The Effects of Surface Texture on EHL Point Contacts
Authors: Ai Xiaolan , Cheng Herbert S. 
Published: February 2008

Abstract
The effect of surface texture on EHL point contact is studied numerically by using the multigrid method. Numerical simulations have been performed for waviness and random roughness with three different orientations, transverse, oblique and longitudinal. Results reveal a strong domination of unidirectional Couette flow in the EHL conjunction. The geometrical variations at inlet of the contact are transported downstream throughout the EHL conjunction. As a consequence, the oblique surface roughness striations are largely distorted, forming nearly longitudinal wavy passages. Results show that the oblique roughness induces local three dimensional EHL pressure fluctuations. The maximum pressure is higher than that of the transverse roughness. For sinusoidal waviness, oblique orientation gives the smallest minimum film thickness as compared with those of longitudinal and transverse waviness.
The Characteristics of Elastically Contacting Ideal Rough
Surfaces
Authors: Yongsheng Leng , Guiping Yang , Yan Huang , Linqing Zheng 
Published: February 2008

Abstract
The analysis of the elastic contact of ideal rough surfaces is presented in this paper. The rough asperities are assumed to be spherical with the same vertical height and spatial distance. The mutual influence of asperities is considered. Numerical results show that for the same load, the contact area is less than the Hertzian prediction, while the pressure distribution is still of a Hertzian type, but is increased to some extent. We find that the asperity interaction is associated with a parameter, called the “loading level,” which combines the surface texture, mechanical properties, and the nominal mean pressure. Of significant importance is the discovery of the variation of the reference plane position with the contact load. In the classical theory of rough contact (Greenwood and Williamson, 1966), the reference plane was in fact assumed to be in the mean line position. We prove that the location of the reference plane is determined by the number of contacting asperities and the loading level, thus making the analysis of the contact of rough surfaces somewhat complex.
Side-Pull and Stiffness of Magnetic Bearing Radial Flux Return
Paths
Authors: Knospe C. R. , Stephens L. S. 
Published: February 2008

Abstract
Certain magnetic bearing designs, both radial and axial, contain a cylindrical radial flux return path. The magnetic flux in this path produces a radial negative stiffness and, if the journal is displaced, a side-pull force. In this paper, closed-form solutions are found for both of these properties by determining the magnetomotive force in the eccentric gap. This is achieved by solving the Dirichlet boundary value problem in the eccentric annulus. A conformal transformation to bipolar coordinates is utilized which results in a much simpler boundary value problem than if the physical coordinates are used. An example problem is presented which indicates the significance of these two properties.
Life Assessment of 1 1/4 Cr-1/2 Mo Steel Catalytic Reformer Furnace
Tubes Using the MPC Omega Method
Authors: Ibarra S. , Konet R. R. 
Published: February 2008

Abstract
Remaining life assessments were conducted on in-service catalytic reformer furnace tubes that had been operating 21 yr. These assessments were made with both API RP 530 (Appendix E) and the new Project Omega method. Small sections from the furnaces were removed and creep rupture tests conducted using the Omega methodology, and the remaining life was determined. These tests showed that the furnace tubes had negligible damage.
A Procedure to Predict Solid Particle Erosion in Elbows and
Tees
Authors: Shirazi S. A. , Shadley J. R. , McLaury B. S. , Rybicki E. F. 
Published: February 2008

Abstract
A semi-empirical procedure has been developed for predicting erosion rates in pipe geometries, such as elbows and tees. The procedure can be used to estimate safe operating conditions and velocities in oil and gas production where sand is present. In the proposed procedure, a concept is introduced that allows determination of erosion rate for different pipe geometries. In the procedure, based on empirical observations, the erosion rate is related to the impact velocity of sand particles on a pipe fitting wall. A simplified particle tracking model is developed and is used to estimate the impact velocity of sand particles moving in a stagnation region near the pipe wall. A new concept of equivalent stagnation length allows the simplified procedure to be applicable to actual pipe geometries. The “equivalent stagnation regions” of an elbow and a tee geometry of different sizes are obtained from experimental data for small pipe diameters, and a computational model is used to extend the procedure to larger pipe diameters. Currently, the prediction method applies to mild steel and accounts for the effects of sand size, shape, and density; fluid density, viscosity, and flow speed; and pipe size and shape. The proposed method has been verified for gas and liquid flows through several comparisons with experimental data reported in the literature. The results of the model accurately predict the effects of sand size and fluid viscosity observed in the experiments. Furthermore, predicted erosion rates showed good agreement with experimental data for gas, liquid, and gas-liquid flows in several 50.8-mm (2-in.) elbows and tees.
A Constitutive Model for High Damping Rubber Bearings
Authors: Sano` T. , Di Pasquale G. 
Published: February 2008

Abstract
Some simplified 1-degree-of-freedom (1-dof) constitutive models suitable for the simulation of high damping rubber bearings are analyzed. The well-known equivalent elastic and bilinear models are compared with a version of the Davidenkov-Martin law modified by the authors. The seismic behavior of an isolated structure is analyzed using the different models and the results are compared. The predictions obtained by means of the proposed law are also compared with experimental snap-back test results.
Yield-Before-Break Fracture Mechanics Analysis of High-Strength Steel Pressure Vessels
Authors: Underwood J. H. , Farrara R. A. , Audino M. J. 
Published: February 2008

AbstractCase study examples of fracture mechanics testing and analysis of Ni-Cr-Mo high strength steel cannon tubes are presented. The testing and analysis include the situation of significant plastic deformation accompanying fracture, which often occurs when high pressure is applied to high-toughness steel pressure vessels. analysis is based on a comparison of the size of the Irwin crack-tip plastic zone the remaining ligament of the tube in the area of the critical fatigue crack which causes final failure. The results of the study show that the type of final failure can be predicted—as either a relatively safe, yield-before-break failure or a less safe running-crack type of failure—for a variety of material, configuration, and loading conditions.
ASME Code Safety Valve Rules—A Review and Discussion
Authors: Bernstein M. D. , Friend R. G. 
Published: February 2008

Abstract
Safety valve rules, i.e., rules for overpressure protection by the use of various pressure-relieving devices, vary somewhat among the five book sections of the ASME Boiler & Pressure Vessel Code which require such protection. This paper reviews those rules by discussing the following topics: Pressure relief device terminology and function. The problem of overpressure protection. Code rules for overpressure protection: rules for determining required relieving capacity; for allowable overpressure; for set pressure and set pressure tolerance; for blowdown. The various pressure relief devices permitted by the Code. Design of pressure relief valves. How relieving capacities are established and certified. The qualification of pressure relief device manufacturers. Installation guidelines. Concluding remarks.
Robust Approximate Methods for Estimating Inelastic Fracture Parameters
Authors: Seshadri R. , Kizhatil R. K. 
Published: February 2008

AbstractRobust approximate methods to estimate the inelastic energy release rate J, and the creep crack-growth parameter, C*, for cracked components are described in this paper. These methods use linear elastic finite element analysis in conjunction with the concepts of the generalized local stress strain (GLOSS) analysis and redistribution nodes (r-nodes), and are readily applicable to complex geometries and loadings. J-estimates obtained by the use of robust methods are found to be in good agreement with the results of elastic-plastic finite element analysis.
Effect of Reinforcement on the Strength of Junctions Between
Cylindrical and Conical Shells
Authors: Kalnins A. , Updike D. P. 
Published: February 2008

Abstract
Two failure modes are addressed for cylinder-cone junctions under internal or external pressure: axisymmetric yielding and low-cycle fatigue. If the junction fails to meet the failure criterion of any one of the two modes, then it must be strengthened by reinforcement. It is shown in the paper that the degree to which a junction is strengthened depends on the distribution of the reinforcement. A placement of reinforcement on the cylinder alone, leaving the actual connection between the cylinder and cone unreinforced, adds strength with regard to axisymmetric yielding, but may not strengthen the junction sufficiently with regard to low-cycle fatigue. This means that the junction may appear reinforced, but is not strengthened. It is pointed out that the design rules of Section VIII, Div. 1 of the ASME B & PV Code (1992) set the need for reinforcement according to the failure criterion of low-cycle fatigue, while the distribution of the reinforcement is guided by the criterion of axisymmetric yielding. There is no assurance that the reinforced junction will meet the failure criterion of low-cycle fatigue. This means that the safety margin on the number of allowed cycles is less than that which is expected and that the junction may be unfit for cyclic service. It is also shown in the paper that a reinforcement distribution that requires minimum thicknesses for sections of both the cylinder and cone near the junction can satisfy criteria for both failure modes. This approach is already used in Code Case 2150 of Section VIII, Div. 1, for half-apex cone angles from 30 to 60 deg, and required in Div. 2 for cone angles from 0 to 30 deg. Its extension to angles from 0 to 60 deg for both internal and external pressure is recommended.
The Prediction of Wear in Fluidized Beds
Authors: Rogers W. A. 
Published: February 2008

Abstract
A procedure is formulated to model impact and abrasion wear of surfaces exposed to a fluidized bed. A methodology adapting a single-particle wear model and the kinetic theory of gases to granular flows is used to develop a model accounting for impact wear from all possible particle collisions. Abrasive wear is modeled using a single-particle abrasion model adapted to describe the effects of many abrading particles. Parameters describing granular flow are necessary for evaluation of the resulting wear expressions. They are determined by numerical solution of the conservation equations describing fluidized-bed hydrodynamics. Additional parameters appear in the wear expressions which describe the contact between individual fluidized particles and the wearing surface. These are determined by an optimization procedure which minimizes error between predicted and measured wear rates. The modeling procedure was used to analyze several bubbling and turbulent fluidized bed experiments with single-tube and tube bundle configurations. Quantitative agreement between the measured and predicted wear rates was found, with some exceptions for local wear predictions. This work demonstrates a methodology for wear predication in fluidized beds.
Response and Damping of Fabricated Branch Pipe Junctions Subjected to
Internal Pressure and Simulated Seismic Bending
Authors: Yahiaoui K. , Moreton D. N. , Moffat D. G. 
Published: February 2008

Abstract
This paper presents some of the results obtained from fifteen tests performed to investigate the ratcheting behavior of fabricated piping branch junctions subjected to steady internal pressure and dynamic resonant run pipe in-plane bending imposed to simulate seismic events. The experimental evidence confirms that the dynamic stresses are self-limiting, and thus secondary in nature. The logarithmic decrement method is used to estimate the percentage damping ratios from the steadily decaying free vibration data at the end of a forcing event. It is demonstrated that the percentage damping, measured after the component had experienced cyclic strain ranges as high as 1 percent, is rather low (1–2 percent of critical). These results are contrasted with those from the general literature, and ASME III recommended values from which it is shown that the use of higher damping ratios for similar components and loadings may underestimate the actual dynamic responses.
One-Way Buckling of Circular Rings Confined Within a Rigid
Boundary
Authors: Sun C. , Shaw W. J. D. , Vinogradov A. M. 
Published: February 2008

Abstract
The stability of a ring confined by a rigid boundary, subjected to circumferential end loads, is investigated both theoretically and experimentally. The effect of initial geometric imperfections on the buckling load is determined by assuming an initial deflection configuration as a simple sine form and the critical condition was derived from equilibrium analysis. An experimental approach was designed to verify the analytical results. Comparison with other theoretical results are also made.
Alternate Design Charts for Fixed Tubesheet Design Procedure Included
in ASME Boiler and Pressure Vessel Code, Section VIII, Division
1
Authors: Kuppan T. 
Published: February 2008

Abstract
Design formulas and calculation procedure for the design of fixed tubesheets of shell and tube heat exchangers are included in Appendix AA—Nonmandatory of ASME Boiler and Pressure Vessel Code, Section VIII, Division 1. To minimize the number of calculations, charts are provided as part of the design procedure. This article provides alternate charts for certain parameters and the original version of the charts are extended for larger values of tubesheet design parameter. Numerical values are given in tabular form for certain functions used in plotting the design charts. This will help to do design calculations without referring to the charts.
Development of the MPC Omega Method for Life Assessment in the Creep Range
Authors: Prager M. 
Published: February 2008

AbstractA methodology for characterizing and assessing the behavior of materials after service in the creep range has been developed and used on a broad range of materials and components. It incorporates the results of relatively short-term tests and improved databases on materials properties. The essence of the method is the definition of a material performance characteristic which the author refers to by the symbol Ωp. This coefficient effectively describes the rate at which a material’s ability to resist stress is degraded by strain. While Ωp is a function of stress, temperature, and mode of loading, it is amenable to parametric representation and is, therefore, useful in predicting life and strain accumulation. Time to failure and total accumulated strain are shown to be consequences of a characterizing strain rate, as defined herein, and an appropriate Ωp for the operating conditions and geometry of interest. Accumulated strain, future strain, current creep rate, remaining life, total damage, and damage rate are among the quantities which are easily calculated. The development of the method employs and extends the concepts of Larson-Miller, Monkman-Grant, Robinson, Theta Projection, Kachanov, and Norton.
Stress-Intensity Factors for an Internal Semi-Elliptical Surface Crack in Cylindrical Pressure Vessels
Authors: Chen D.-H. , Nisitani H. , Mori K. 
Published: February 2008

AbstractIn this paper, the surface crack problem in a cylinder subjected to internal pressure is solved. The analysis is based on the body force method, but it is different from the conventional body force method in the following point. That is, the body forces to be distributed continuously on the assumed boundaries in an infinite body are approximated by some discrete point forces acting on the outside of the assumed boundaries. By using this method combined with the resultant force boundary conditions, solutions with high accuracy are obtained.
Failure Investigation of a Low Chrome Long-Seam Weld in a
High-Temperature Refinery Piping System
Authors: Buchheim G. M. , Osage D. A. , Brown R. G. , Dobis J. D. 
Published: February 2008

Abstract
The results of an investigation of a long-seam welded low chrome pipe that failed in a high-temperature refinery piping system are presented in this paper. Based upon the results of a metallurgical investigation, which included a creep testing program and a detailed finite element stress analysis, the cause of the failure has been attributed to creep damage at the weld seam. The metallurgical investigation and creep testing program indicated that the 1-1/4 Cr-1/2 Mo pipe material was normalized and exhibited greater than average creep strength and creep ductility. The results of a piping stress analysis indicated that all pressure, weight, and thermal stresses were in compliance with the ASME B31.3 Piping Code (ASME, 1993a). Nonetheless, the pipe failed after only 100,000 h at a nominal hoop stress of 6 ksi (41.4 MPa) with an operating temperature range of 970°F (521°C) to 1000°F (538°C). Results from subsequent detailed finite element stress analyses of the failed pipe indicated that very high localized bending stresses were present in the pipe due to peaking at the long-seam weld. These stresses partially relax by creep, but after 100,000 h they were still approximately 38 percent higher than the nominal hoop stress. The creep strains resulting from stress relaxation and those associated with the long-term value of the sustained stresses cause severe creep damage at the weld seam. As a result of this damage, cracks initiated at the inside of the pipe and primarily grew through the HAZ/fusion line until an 18-in. through-wall crack developed. The pipe was produced to ASTM A691, Grade 1-1/4 Cr, Class 41 (ASTM, 1989), and the peaked geometry was found to satisfy the fabrication tolerances of this standard. The need for the development of an acceptable tolerance for peaking in addition to the outside diameter and out-of-roundness fabrication tolerances currently included in this standard is highlighted for long-seam welded pipe that is to operate in the creep range.