bluuebunny/crossref_metadata_2025 huggingface dataset:
Life Assessment of Hot Reheat Steam Pipe
Authors: Jaske C. E.
Published: June 2008

A methodology for assessing the remaining life of hot reheat steam pipe with longitudinal flaws, such as those typically associated with the longitudinal seam welds, has been developed. The approach uses three levels of analysis. Level 1 employs handbook data, assumed flaw sizes, and design parameters. Level 2 employs handbook data, assumed flaw sizes, and actual operating parameters. Level 3 is tailored to a specific case and uses measured data, inspection results, and actual operating parameters. A computer code was developed to apply this approach to hot reheat steam pipe of 2-1/4Cr-1Mo and 1-1/4Cr-1/2Mo-Si steel. Using data from an EPRI survey (RP2596-7), the results of Level 1 analysis were found to predict the potential for creep damage and fracture and to correlate well with past experience, whereas the traditional lower-bound Larson-Miller approach was generally overly optimistic in predicting remaining service life. The approach predicts creep-crack-growth life and assesses the potential of rapid, unstable fracture occurring before a significant amount of leaking takes place. The usefulness of the methodology is illustrated by means of example analyses of a typical cases that might be expected in service. The parameters that were varied in these analyses include type of material (base metal or weld metal), pressure, temperature, pipe wall thickness, and initial flaw size. The approach provides a preliminary tool to help make inspection, operating, and replacement decisions; but additional work is required to validate it as a general tool.
Response Characteristics of Piping System Supported by Visco-Elastic and Elasto-Plastic Dampers
Authors: Chiba T. , Kobayashi H.
Published: June 2008

Improving the reliability of the piping systems can be achieved by eliminating the mechanical snubber and by reducing the response of the piping. In the seismic design of piping system, damping is one of the important parameters to reduce the seismic response. It is reported that the energy dissipation at piping supports contributes to increasing the damping ratio of piping system. Visco-elastic damper (VED) and elasto-plastic damper (EPD) were developed as more reliable, high-damping piping supports. The dynamic characteristics of these dampers were studied by the component test and the full-scale piping model test. Damping effect of VED is independent of the piping response and VED can be modeled as a complex spring in the dynamic analysis. On the other hand, damping ratio of piping system supported by EPD increases with the piping response level. So, these dampers are helpful to increase the damping ratio and to reduce the dynamic response of piping system.
Dynamic Response of Sandwich Shells of Revolution
Authors: Singh A. V. , Mirza S. , Gupgupoglu K.
Published: June 2008

Development of an annular finite element, for the linear elastic analysis of sandwich shells, is reported here. The derivation of stiffness and mass matrices is based on improved shell theory which takes into account the effects of rotary inertia and transverse shear deformation. Flexural rigidity of the faces is included in the formulation. The core of the sandwich shell is assumed to be incompressible in the radial direction. Numerical examples of spherical sandwich shells with two types of boundary conditions—(i) fixed and (ii) pinned along the outer periphery—have been presented. The results are generated for displacements and frequencies.
Effects of Soil on the Dynamic Response of Liquid-Tank
Systems
Authors: Hori N.
Published: June 2008

A procedure is presented for the subsystem approach of a liquid-tank-soil system subjected to horizontal and vertical earthquake excitations by the Rayleigh-Ritz method. The dynamic interaction forces between the tank and soil are represented by the impedance functions obtained from the boundary element method. The tank is modeled as an elastic shell and the base of the tank is considered as a surface rigid disk resting on an elastic half-space or a layered elastic medium. A shaking table test of a liquid-elastic tank on an elastic soil model was carried out to verify experimentally the dynamic interaction. The numerical results show that the elastic response of the tank decreases due to the effect of radiation damping in the foundation. Furthermore, the experimental results show that the response of the tank decreases due to stiffness of the soil.
Simplified Models for the Dynamic Response of Tall Unanchored Liquid
Containers
Authors: Natsiavas S.
Published: June 2008

Two simplified models are presented for determining the hydrodynamic loads developed during the seismic response of tall unanchored liquid storage tanks. In both models the general procedure starts by first solving the fluid response problem in closed form. This eliminates all but the sloshing unknowns associated with the hydrodynamic problem. In the first model, the geometrical discretization is performed by applying the assumed mode method. In the second model, the system parameters are identified by requiring the same base loads when the real system and the model are subjected to the same base motion. During the formulation process, special attention is paid to developing a simple but sufficiently accurate analytical modeling of the mechanism associated with the separation of the base plate of the tank from its foundation, which occurs during strong ground motion. Soil flexibility and liquid sloshing effects are also modeled. The accuracy of both models is verified by comparison with experimental data. In addition, this comparison shows the applicability of these models for determining the seismic loads in tall unanchored tanks.
Numerical Prediction of Welded Joint Performance—Relative Criticality
of Weld Defect and Remote Deformation
Authors: DeGiorgi V. Gensheimer , Matic P. , Jolles M. I.
Published: June 2008

Structural integrity problems which deal with welded sections are common in the pressure vessel and piping industry. The current work uses continuum fracture toughness concepts to determine the structural integrity of a butt-welded plate with a lack of penetration defect in the weld material. The difference in weld and base metal properties are explicitly included in the computational simulation. The analysis technique presented does not require the analyst to assume a failure location. The critical strain energy density associated with fracture of a material at the continuum scale is used as the failure criterion.
Basis and Development of Toughness Requirements for Class 2, Class 3,
Containment and Component Support Materials in Section III of the ASME
Code
Authors: Yukawa S. , Doty W. D. , Landerman E. I.
Published: June 2008

In 1972, Section III of the ASME Boiler and Pressure Vessel Code adopted new fracture toughness requirements for Class 1 components based on fracture mechanics concepts. In the ensuing several years, new toughness requirements were developed and adopted for the other Section III classes of components covered by Subsections NC, ND, NE, and NF. This paper describes the chronology of these developments and the bases of the rules and criteria. The formulation of specific rules is discussed and examples of data used to support the criteria are described. The rules and requirements as initially adopted, and subsequent revisions and modifications are discussed to show their evolution into the current version.
Remaining Life of High-Energy Piping Systems Using Equivalent
Stress
Authors: Cohn M. J.
Published: June 2008

Fossil power plant high-energy piping systems operated at high temperatures are subject to creep damage, which is a time-dependent phenomenon. Traditional guidelines, such as the American Society of Mechanical Engineers (ASME) B31.1 Power Piping Code, were developed for plants having design lives in the 25–30 yr regime. Since many of these systems are being operated beyond 200,000 hr, it is important to reconsider the methodology of creep damage analysis to assure reliable long-term operation. Seven high-energy piping systems were evaluated in this study. The analysis of a minimum piping system life due to creep considered two approaches. The first approach used the traditional ASME B31.1 flexibility analysis guidelines. The second approach considered more detailed multiaxial stress state types of evaluations. The various equivalent stress methods used all six load components from the flexibility analysis. In nearly every case, the equivalent stress methods predicted significantly higher stresses. Consequently, the equivalent stress methodology results in 14 to 97 percent lower time to rupture values as compared to the values predicted using ASME B31.1 stresses.
Modeling of Distortion in Girth-Welded Thin Pipes
Authors: Song H. , Moshaiov A.
Published: June 2008

The axisymmetric distortion in girth-welded pipes is studied in this paper. A model is developed based on the fact that only a small part of the pipe near the welding arc undergoes high temperature changes, and thus behaves thermo-elastic-plastically, while the rest of the structure is elastic in nature and may, at most, have some thermo-elastic effects. The model is shown to match Finite Element Method in predicting the overall approximated axisymmetric shrinkage in girth-welded pipes. A qualitative agreement with published analytical and experimental results is achieved as well.
An Experimental Study on the Influence of Structural Damping on
Internal Fluid Pressure During a Transient Flow
Authors: Budny D. D. , Hatfield F. J. , Wiggert D. C.
Published: June 2008

The traditional approach to designing a piping system subject to internal dynamic pressure is to restrain the piping as much as possible, and the approximation made in the analysis is to assume no contribution of structural energy dissipation. To determine the validity of this concept and approximation, an experimental study of a piping system was performed to measure the influence of structural damping. A pipe system was designed with a loop that could be turned so that its natural frequency would match that of the contained liquid. It was discovered that a properly sized damper on the piping loop greatly accelerates the decay of the fluid pressure transient. The damper absorbs some energy from the piping, reducing the resulting rebound fluid pressure. When the loop is subjected to forced steady-state vibration, there is a fluid pressure response. The amplitude of that pressure can be reduced by installing an external damper: the stiffer the damper the more effective it is in reducing dynamic pressure.
Dynamic Response of Buried Pipelines—An Elasticity
Solution
Authors: Mishra B. K. , Upadhyay P. C.
Published: June 2008

This paper presents a theory of elasticity solution of the axisymmetric steady-state dynamic response of a buried pipeline excited by a plane longitudinal wave (P-wave) traveling in the surrounding soil. Both the pipeline and the ground have been assumed to be linearly elastic, homogeneous and isotropic. Linear elasticity equations of motion have been solved simultaneously for the pipeline and the surrounding soil. A perfect bond between the pipeline and the ground has been assumed. The midplane deformations of the pipeline have been plotted against the nondimensional wave number of the incident wave, for different soil condition and angle of incidence of the wave. The results of the present work have been compared with those found by using a shell theory which includes the effect of shear deformation and rotary inertia. It has been found that excellent agreement exists between the results obtained by the two approaches. The present work concludes that the use of shell model, including effects of shear deformation and rotary inertia, is justified for the analysis of dynamic response of buried pipelines excited by seismic waves traveling in the ground.
Elastic-Plastic Analysis of a Spherical Shell Loaded Radially Through
a Flexible Cylindrical Nozzle
Authors: Leung C.-P. , Brooks G. N.
Published: June 2008

This study investigates the elastic-plastic behavior of a shallow spherical shell loaded radially through a flexible cylindrical nozzle. Both the sphere and the cylinder can yield and exhibit plastic deformation. The Tresca yield condition is employed to derive elastic-plastic moment-curvature relationship in a simple form which is implemented in an efficient solution scheme. Three geometric parameters represent the relative dimensions of the structure. Numerical results are obtained for a range of values of these parameters. Various situations involving the failure of the sphere and/or the cylinder are studied. The ultimate or failure loads of the structure are plotted as functions of the geometric parameters.
Stress Intensity Factors for Unequal Longitudinal-Radial Cracks in Thick-Walled Cylinders
Authors: Desjardins J. L. , Burns D. J. , Bell R. , Thompson J. C.
Published: June 2008

Finite elements and two-dimensional photoelasticity have been used to analyze thick-walled cylinders which contain arrays of straight-fronted, longitudinal-radial cracks of unequal depth. The stress intensity factor K1 has been computed for the dominant crack and for some of the surrounding cracks. Cylinders with 2, 4, 6, 8, 16, 36 and 40 cracks have been considered. Good agreement has been obtained between the experimental and the numerical results and, for cylinders with 2 or 4 cracks, with previously published predictions. The results for all of the foregoing cases are used to develop simple, approximate techniques for estimating K1 for the dominant crack, when the total number of cracks is different from those that have been considered herein. Estimates of K1 obtained by these techniques agree well with corresponding finite element results.
Creep Buckling Under Varying Loads
Authors: Miyazaki N. , Hagihara S. , Munakata T.
Published: June 2008

Creep buckling analyses under stepwise varying loads are performed on a circular cylindrical shell with initial imperfection subjected to axial compression and a partial spherical shell under uniform external pressure. The finite element method is applied to a creep deformation analysis to obtain the critical time when creep buckling occurs. The results show that a linear cumulative damage rule for creep buckling can be well applied to the creep buckling of the circular cylindrical shell, but cannot to that of the partial spherical shell.
A Rational Procedure for Analyzing Flanged and Flued Expansion Joints
Authors: Singh K. P. , Soler A. I.
Published: June 2008

This paper presents a procedure for computing the axial stiffness of “formed head” type of expansion joints. The method given herein is an extension of the plate and shell theory adaptation of the “Kopp and Sayre method” first published by the authors in the text, Singh and Soler (1984). Arcturus Publishers. The approach suggested in this paper has been adopted by the Seventh Edition of the TEMA Standards.
A Study on the Natural Frequencies of Coupled In-Line Towers
Authors: Qingde N. , Jiaqi C. , Mingxian Z. , Zenyan H.
Published: June 2008

The natural frequencies of the coupled in-line towers are the most important parameters for dynamic analysis when the designer takes steps to assure that damages due to wind loads, seismic loads, or wind-induced vibration would not occur. In this paper the authors present an analytical method for determining these parameters. The theoretical results are compared with the experimental data obtained from the industrial towers in the field, and are in good agreement.
Dynamic Response of Composite Pressure Vessels to Inertia Loads
Authors: Prucz J. C. , D’Acquisto J. , Smith J. E.
Published: June 2008

A new analytical model has been developed in order to investigate the potential benefits of using fiber-reinforced composites in pressure vessels that undergo rigid-body motions. The model consists of a quasi-static lamination analysis of a cylindrical, filament-wound, pressure vessel, combined with an elastodynamic analysis that accounts for the coupling effects between its rigid-body motion and its elastic deformations. The particular type of motion investigated in this paper is that of an oil-pressurized, tubular connecting rod in a slider-crank mechanism of an internal combustion engine. A comprehensive parametric study has been focused on the maximum wall stresses induced in such a rod by the combined effect of internal pressure and inertia loads associated with its motion. The numerical results illustrate potential ways to reduce these stresses by appropriate selection of material systems, lay-up configurations and geometric parameters.
Twenty Years of Fracture Mechanics and Flaw Evaluation Applications in the ASME Nuclear Code
Authors: Riccardella P. C. , Yukawa S.
Published: June 2008

The paper presents a retrospective on the development and applications of fracture mechanics-based toughness requirements and flaw evaluation methodology in Sections III and XI of the ASME Code. Section III developments range from the rules and requirements for thick section Class 1 pressure vessels to thinner section components in other Classes. Section XI applications include flaw acceptance standards and evaluation methodology for various components ranging from pressure vessels to thin section piping of carbon and austenitic steels. The experience gained in operating plant applications of these rules and procedures are also discussed.
Anisotropic Fracture Toughness Effects on Failure Modes of Piping
Authors: Wilkowski G. M.
Published: June 2008

This paper summarizes various cases where anisotropic fracture toughness properties caused the failure mode to change during ductile fracture experiments on piping. It is noted that in particular for carbon steel piping, the anisotropy can cause an initial circumferential crack to propagate in a helical or even axial direction, even though there are only applied bending loads. This has implications that under combined loading, such pipes may have lower longitudinal stresses at failure than may be calculated by a leak-before-break analysis that only considers the longitudinal stresses and the toughness in the circumferential crack growth plane.
A PC-Based Modeling Tool for Creep, Fatigue, and Creep-Fatigue Interactions Using a Viscoplasticity Theory
Authors: Fong J. T. , Bernstein B.
Published: June 2008

Computational results for modeling one-dimensional stress relaxation, creep, fatigue, and creep-fatigue interaction phenomena of metals at elevated temperatures using a unifying thermodynamic theory of viscoplasticity are presented. The theory incorporates in a nonequilibrium formulation the idea of a “concealed” parameter α, originally due to Bridgman (1950), where the constitutive equations are governed by 1) a thermodynamic potential such as the Helmholtz free energy function F with an explicit dependence on α, and 2) a prescription for α˙, the time rate of change of α, such that α˙ is proportional to −Fα, the negative of the partial derivative of F with respect to α. Significance of the results and a comparison with other modeling tools in the literature are discussed.
Assumed Process of Piping Failure in Nuclear Power Plants Under Destructive Earthquake Conditions
Authors: Shibata H.
Published: June 2008

This paper deals with an assumed process of piping failure in nuclear power plants which may cause a catastrophic accident during a destructive earthquake condition. The type of failure discussed is the so-called double-ended guillotine break, DEGB. As a safety problem, we are going to eliminate this type of failure by LBB, and we have assumed that this would then not occur by an earthquake. The author tries to clarify the possibility of failure during earthquakes. He reviews his related papers since 1973, and discusses zipping failure of snubbers and supporting devices. He shows a procedure to simulate the zipping failure of a piping system supported by snubbers.
Some Results on the Analytical Solution of Cylindrical Shells With Large Openings
Authors: Xue M.-D. , Deng Y. , Hwang K.-C.
Published: June 2008

An analytical solution for cylindrical shells with large openings has been developed by the asymptotic method. In comparison with previous analytical solutions obtained by Eringen, Van Dyke and Lekkerkerker, the following three areas have been improved by the present method: 1) The modified Morley’s equation, which is applicable to ro/RT≫1, is used instead of Donnell’s shallow shell equation. 2) The accurate expression of boundary curve of hole is expanded in terms of powers of ρo = ro/R, while the previous approximate geometric description corresponds to the first term of the expansion. 3) The accurate boundary conditions for generalized forces are expanded in terms of powers of ρo and truncated after the terms of ρo3; the previous approximate boundary conditions correspond to the terms of order up to ρo, in the asymptotic expansions. The present solutions are in good agreement with Van Dyke’s solutions for small openings. The analytical results show that the error caused by the previous approximate boundary conditions is significant and has the order O(ρo); the error caused by the previous approximate geometric description of hole boundary has the order O(ρo2); and finally, the error caused by using Donnell’s shallow shell equation is very small for ρo ≤ 0.7. For openings with ρo > 0.25, say, noticeable differences exist between the present and the previous results. The stress analysis of cylindrical shells connected with nozzles has been developed by using the present solution. For increasing the accuracy of stress analysis in the nozzle, the exact description of the edge of nozzle is given and the near-edge boundary layer stress state in the nozzle is considered. The results obtained are in good agreement with those by Eringen for small openings and with those by F.E.M. and experiments for large openings.
Fatigue Behavior of Tube-to-Tubesheet Expanded Joints
Authors: Sang Z. F. , Zhu Y. Z. , Widera G. E. O.
Published: June 2008

In order to study the fatigue behavior of expanded tube-to-tubesheet joints for steam generators and tubular heat exchangers under cyclical loading, both static and fatigue tests were performed. As a result of the sticking interface which is formed between the tube and tubesheet hole, it is shown that: 1) the expanded joint of tube-tubesheet interface is not sensitive to cyclic loads, 2) the fatigue strength of the expanded joint is higher than that of the tube materials, and 3) cyclic loads have no obvious effect on the static pull-out strength.
Use of On-Line Fatigue Monitoring of Nuclear Reactor Components as a Tool for Plant Life Extension
Authors: Stevens G. L. , Ranganath S.
Published: June 2008

The application of an on-line fatigue monitoring system for tracking fatigue usage in operating power plants is described. The system, like several others which have been developed, uses the influence function approach, operates on a microcomputer, and determines component stresses using temperature, pressure, and flow rate data that are typically available from plant computers. Using plant-unique influence functions developed specifically for each component location, the system calculates stresses as a function of time and computes the fatigue usage. Stress values are calculated at time intervals defined by the user and the fatigue values are saved on files for use at a later time. The application of the GE Fatigue Monitoring System (GEFMS) to calculate fatigue usage in the feedwater nozzle of a GE Boiling Water Reactor is described in this paper. Stress predictions using GEFMS for a sample temperature transient show excellent agreement with results from finite element thermal and stress analysis performed on a mainframe computer. Fatigue usage calculations for a simulated 24-hr temperature record confirm that the system provides accurate results at a cost that is significantly lower than similar analysis done on mainframe computer systems. The system, which has been installed in a boiling water reactor plant, provides the technical basis to evaluate actual reactor conditions and justify plant life extension.
Full-Thickness Crack Arrest Fracture Toughness of 9-Percent Ni (ASTM 553, Type 1) Steels
Authors: Ripling E. J. , Crosley P. B.
Published: June 2008

Measurements were made of the full-thickness crack arrest fracture toughness (FTCAT) of three 9-percent Ni steels having the range of thicknesses and Charpy V-notch toughnesses of plates now in LNG storage tank service. Unlike the plates used in large pressure vessels, these thinner plates do not crack under a condition of plane strain, so that test method ASTM E1221 “Standard Test Method for Determining Plane-Strain Crack-Arrest Fracture Toughness, Kla, of Ferritic Steels,” was modified for these tests. The toughness of all three steels was measured at liquid nitrogen temperature (−196C), but two of the three were too tough to be measured at LNG storage temperature (−162C). Even the least tough plate had a high enough toughness to arrest long cracks in LNG storage service.
The Crack Arrest Capability of 9-Percent Ni Steels (ASTM 553, Type 1) LNG Storage Tanks
Authors: Crosley P. B. , Ripling E. J.
Published: June 2008

Safety of structures can be assured, even if cracks initiate in localized regions of abnormally low toughness, and/or abnormally high stress (LT/HS), if the materials from which they are fabricated have a high enough crack arrest fracture toughness. When this requirement is met, fast-running cracks that initiate in LT/HS regions arrest when their tip encounters material having normal toughness and stresses. The work described in this paper was carried out to determine the crack arrest capability of LNG storage tanks by determining the longest LT/HS region in which a crack could initiate and still arrest when it leaves this region. The determination consisted of relating a fracture analysis with the measured full-thickness crack arrest fracture toughness of three 9-percent Ni plates which were reported in reference [1]. The calculations used a residual stress pattern, produced by welding, superimposed on a typical membrane stress. The residual stress was selected as an example of a localized high stress region. It was found that tanks built from the poorest of the three tested plates could arrest cracks about 3/4 m long, while tanks built from the two tougher plates could arrest cracks almost 2 m long.
Rate Sensitivity and Short-Term Relaxation Behavior of AISI Type 304 Stainless Steel at Room Temperature and at 650°C; Influence of Prior Aging
Authors: Ruggles M. B. , Krempl E.
Published: June 2008

The strain rate sensitivity and short-term relaxation behavior of Type 304 stainless steel were investigated in the uniaxial strain rate jump tests with intermittent periods of relaxation at room temperature and at 650°C. At room temperature material exhibited conventional strain rate sensitivity and no strain rate history effect. The high-temperature experimental results revealed a complex and dramatically different material behavior. At 650°C the pattern of strain rate sensitivity was not set as soon as the plastic flow was fully established, but continued to evolve with the further straining in the plastic range. Test results indicate that at 650°C the material may exhibit a strain rate history effect. Both at room temperature and at 650° C the relaxation behavior was independent of the stress and/or strain level at the beginning of the relaxation, but depended nonlinearly on the strain rate preceding the relaxation test. Prior aging had no significant influence on the rate-dependent material response. The irregular material behavior at 650° C is attributed to dynamic strain aging as indicated by serrated stress-strain curves (the Portevin-LeChatelier effect).
Two-Dimensional Crack Inclusion Interaction Effects: Analysis and Experiments
Authors: Santare M. H. , O’Toole B. J. , Patton E. M.
Published: June 2008

The plane interaction between a crack and a rigid elliptical inclusion is investigated. In particular, the effects of the orientation and aspect ratio of the inclusion are considered. Analytically, the solution for the interaction of a dislocation with an inclusion is used as Green’s function for the problem. The crack problem is then cast in the form of a set of integral equations with Cauchy singularities. These are solved numerically by the use of piecewise quadratic polynomials to approximate the unknown dislocation density along the crack. From this density the stress intensity at the crack tip can be determined. To model the situation experimentally photoelastic specimens with various elliptical inclusions are tested in uniaxial tension. The stress intensity factors are evaluated from the isochromatic fringe patterns and compared to those predicted numerically.
On the Dynamics and Stability of Cylindrical Shells Conveying Inviscid or Viscous Fluid in Internal or Annular Flow
Authors: Chebair A. El , Misra A. K.
Published: June 2008

This paper investigates theoretically for the first time the dynamical behavior and stability of a simply supported shell located coaxially in a rigid cylindrical conduit. The fluid flow is incompressible and the fluid forces consist of two parts: (i) steady viscous forces which represent the effects of upstream pressurization of the flow; (ii) unsteady forces which could be inviscid or viscous. The inviscid forces were derived by linearized potential flow theory, while the viscous ones were derived by means of the Navier-Stokes equations. Shell motion is described by the modified Flu¨gge’s shell equations. The Fourier transform technique is employed to formulate the problem. First, the system is subjected only to the unsteady inviscid forces. It is found that increasing either the internal or the annular flow velocity induces buckling, followed by coupled mode flutter. When both steady viscous and unsteady inviscid forces are applied, for internal flow, the system becomes stabilized; while for annular flow, the system loses stability at much lower velocities. Second, the system is only subjected to the unsteady viscous forces. Calculations are only performed for the internal flow case. The results are compared to those of inviscid theory. It is found that the effects of unsteady viscous forces on the stability of the system are very close to those of unsteady inviscid forces.
Influence of Shell Geometry on Buckling Optimization of Fiber-Composite Laminate Shells
Authors: Hu H.-T.
Published: June 2008

The buckling strength of fiber-composite laminate shells with given loading condition and material system is maximized with respect to fiber orientations by using a sequential linear programming method together with a simple move-limit strategy. Significant influence of shell thickness and shell length on the optimal fiber angles, the critical buckling loads and the critical buckling modes of fiber-composite laminate shells has been shown through this investigation.
Design Strength of Primary Structural Welds in Freestanding Structures
Authors: Singh K. P. , Soler A. I. , Bhattacharya S.
Published: June 2008

A rational analysis technique to evaluate structural integrity of primary welds in free-standing structures in accordance with the ASME Code is presented. This paper is intended to fill the void in the ASME Code rules for analyzing welds under “faulted” (level D) conditions in nonlinear free-standing structural components used in safety-related applications in nuclear power plants.
The ASME Code and 3D Stress Evaluation
Authors: Hechmer J. L. , Hollinger G. L.
Published: June 2008

The ASME Code [1] identifies the modes of failure that must be addressed to ensure acceptable pressure vessel designs. The failure modes addressed in this paper are precluded by limits on the primary and primary plus secondary stress. Both involve the transition from elasticity to plasticity. Their evaluation requires the computation of membrane and bending stresses (the linearized stresses). The original techniques for evaluating the limits were based on beam and shell theory. Since beam and shell theory were the basis of the then-current tools, the transition from analysis results to failure assessment was straightforward. With the advent of finite elements (FE), the transition from the stress distribution to the failure modes requires a different path. For three-dimensional finite element (3D FE), the path is obscure. Since the development of FE, the ASME Code has made no additions to clarify the correlations between FE stress distributions and the failure modes. The authors believe that the Code should provide guidance in this area.
Simplified Dynamic Analysis Methods for Metallic Bellows Expansion Joints
Authors: Morishita M. , Ikahata N. , Kitamura S.
Published: June 2008

An investigation into dynamic characteristics and seismic response of bellows expansion joints is described. For axial and lateral vibrations of the bellows, simplified methods are developed to evaluate their natural frequencies and seismic response, based on analogies with those of a uniform rod and a Timoshenko beam, respectively. For the lateral vibration modes, effect of fluid-structure interaction between the convolutions and flow-sleeve is taken into account. The validity and applicability of the simplified methods are shown, by comparing with the results of vibration experiments using a simple bellows model and a piping model with bellows, along with corresponding detailed FEM analyses’ results.
Impulsive Responses of a Circular Cylindrical Shell Subjected to Waterhammer Waves
Authors: Adachi T. , Ujihashi S. , Matsumoto H.
Published: June 2008

The impulsive responses of semi-finite and finite pipes filled with fluid are analyzed in order to clarify the validity of Joukowsky’s theory and the fluid-pipe coupling effect. In the analysis, Flu¨gge’s dynamic bending shell theory and the potential theory of compressible perfect fluid are used. The analytical solutions in Laplace transformed domain are obtained. The inversion of the solutions is performed numerically using the algorithm of FFT. When a pipe is fairly long, it is shown that the result of Joukowsky’s theory which has no pipe inertia effect approximately agrees with that of the coupled theory. When a pipe is short, Joukowsky’s theory shows rough approximation of the responses. The response of the uncoupled theory with the inertia of a pipe is different from that of the coupled theory for both long and short pipes.
Response Analysis of Secondary Systems With Nonlinear Supports
Authors: Igusa T. , Sinha R.
Published: June 2008

This paper introduces a simplified random vibrations analysis method of linear secondary systems with nonlinear supports. The method separates, as much as possible, the nonlinear analysis of the supports from the linear analysis of the remainder of the secondary system. Equivalent linearization is used to generate response-dependent linear properties of the supports directly from hysteresis loops. These properties are then combined with the properties of the secondary system, and a response analysis is performed using mode combination. The analysis procedure is simpler than standard random vibration methods, and for narrow-band responses, it accurately models nonlinear behavior. In addition, the procedure uses equivalent modal quantities, such as natural frequencies and damping ratios, which provide insight into the effects of the nonlinear supports on the secondary system.
An Analysis of High-Temperature Crack Growth in Type 308 Cb Stainless Steel and Its Weldment
Authors: Radhakrishnan V. M. , Kamaraj M.
Published: June 2008

Creep crack growth behavior of type 308 Cb austenitic stainless steel and its weldment has been studied in the temperature range of 875 to 1075 K under plane stress condition. The creep crack growth (CCG) rate has been correlated with parameters like stress intensity factor, K, net section stress and energy rate line integral C*. Among these parameters C* appears to describe well the CCG rate in both the cases of base metal and weldment. The rupture time tr of the cracked material has been found to be related to the energy rate line integral C*s in the steady-state condition, given by a relation of the type C*s · tr = constant.
Creep-Fatigue Strength of Long-Term Post-Service 2 · 1/4 Cr-1 · Mo Steel and Remaining Life Estimation
Authors: Okazaki M. , Hashimoto M. , Mochizuki T.
Published: June 2008

Creep-fatigue strength of post-service 2 · 1/4 Cr-1 · Mo steel used for about one hundred-thousand hours in a fossil fuel power plant was studied. The creep-fatigue strength of the post-service material was lower than that of the virgin material, whereas it was comparable to that of thermally aged material, which was artificially exposed at high temperature for a long time so that it had an equivalent value of the Larson-Miller parameter to the post-service material. The nondestructive detection of the long-term degradation damage due to long-term thermal aging, as well as due to creep-fatigue, was also investigated by applying an ultrasonic technique. It was found that the energy attenuation coefficient, α, which is defined by the ratio of input to output energies of a longitudinal ultrasonic wave, had a good correlation with creep-fatigue damage in the virgin, aged and post-service materials; and hence, α was a successful parameter to detect creep-fatigue damage. Based on the results thus obtained, a new remaining life estimation method for creep-fatigue of in-service high-temperature materials was proposed. The application of the method to the post-service material tested gave good predicted results.
Analytical Solutions of Refined Plate Theories of Cross-Ply Composite Laminates
Authors: Khdeir A. A. , Reddy J. N.
Published: June 2008

Exact solutions of rectangular laminated composite plates with different boundary conditions are studied. The Le´vy-type solutions of the classical, first-order and third-order shear deformation theories are developed using the state-space approach. The finite-element solutions for the three theories are also computed and compared with the exact solutions for various boundary conditions.
On Vibrations of Shells of Revolution Using Bezier Polynomials
Authors: Singh A. V.
Published: June 2008

A very computationally efficient numerical technique for the free vibration analysis of shells of revolution is presented in this study. The generic segment of the shell structure is given in the form of a circular arc which revolves around the vertical axis. Displacement fields in each segment are represented by quintic Bezier functions which are shown in this investigation to have very desired characteristics. Accurate values of the dimensionless frequency parameter were obtained using only two to four shell segments of spherical, cylindrical, and conical shells and compared favorably with the results from the open literature. Complicated-shaped rotationally symmetric shell structures described by a series of circular arc segments tangential to each other at the juncture, can be analyzed without any approximation in geometry.
Nonlinear Analysis of Transverse Shear Deformable Laminated Composite Cylindrical Shells—Part II: Buckling of Axially Compressed Cross-Ply Circular and Oval Cylinders
Authors: Soldatos K. P.
Published: June 2008

A linearized transverse shear deformable shell theory presented in a companion paper is confined to consideration with the buckling problem of axially compressed, cross-ply laminated noncircular cylindrical shells. Based on a solution of its governing differential equations, obtained for simply supported shells by means of Galerkin’s method, a study of the buckling problem of axially compressed circular and oval cylindrical shells, of a regular antisymmetric cross-ply laminated arrangement, is presented. Moreover, by comparing the numerical results obtained with corresponding results based on a classical Love-type shell theory, the combined influence of both the transverse shear deformation and the shell eccentricity on the buckling loads of such laminated composite shells is examined.
Reissner’s New Mixed Variational Principle Applied to Laminated Cylindrical Shells
Authors: Bhaskar K. , Varadan T. K.
Published: June 2008

Reissner’s new mixed variational theorem, which allows independent interpolation, through the thickness, of the three transverse stresses besides that of the three displacements, is applied here to derive a higher-order theory of laminated orthotropic cylindrical shells. The accuracy of the theory is verified by comparison with three-dimensional elasticity solutions. It is shown that Reissner’s principle does not directly lead to accurate transverse shear stress predictions, but requires the use of the equilibrium equations of three-dimensional elasticity as is common in the conventional displacement approach.
Basis of the Tubesheet Heat Exchanger Design Rules Used in the French Pressure Vessel Code
Authors: Osweiller F.
Published: June 2008

For about 40 years most tubesheet exchangers have been designed according to the standards of TEMA. Partly due to their simplicity, these rules do not assure a safe heat-exchanger design in all cases. This is the main reason why new tubesheet design rules were developed in 1981 in France for the French pressure vessel code CODAP. For fixed tubesheet heat exchangers, the new rules account for the “elastic rotational restraint” of the shell and channel at the outer edge of the tubesheet, as proposed in 1959 by Galletly. For floating-head and U-tube heat exchangers, the approach developed by Gardner in 1969 was selected with some modifications. In both cases, the tubesheet is replaced by an equivalent solid plate with adequate effective elastic constants, and the tube bundle is simulated by an elastic foundation. The elastic restraint at the edge of the tubesheet due the shell and channel is accounted for in different ways in the two types of heat exchangers. The purpose of the paper is to present the main basis of these rules and to compare them to TEMA rules.
Study of Integration Strategy for Thermal-Elastic-Plastic Models
Authors: Hong H.-K. , Lan H.-S. , Liou J.-K.
Published: June 2008

The accuracy of a new integration algorithm is examined for a von Mises-type model of thermal-elastic-plasticity with nonlinear, mixed isotropic-kinematic hardening. The algorithm is founded on the frame of an integral representation of the conventional rate constitutive equations in contrast to the conventional rate equations themselves. The thermal effect on the yield surface is built in this approach without any difficulty. Under a generalized assumption of a constant strain rate, the model can be reduced to two scalar first-order ordinary differential equations which make an error-controllable integration method possible. Furthermore, for a nonconstant strain rate, e.g., a linear strain rate, the same idea of derivation achieves a similar conclusion. Errors of single-step stress predictions for given total strain increments are discussed.
A Theory for Fluidelastic Instability of Tube-Support-Plate-Inactive Modes
Authors: Cai Y. , Chen S. S. , Chandra S.
Published: June 2008

Fluidelastic instability of loosely supported tubes, vibrating in a tube support plate (TSP)-inactive mode, is suspected to be one of the main causes of tube failure in some operating steam generators and heat exchangers. This paper presents a mathematical model for fluidelastic instability of loosely supported tubes exposed to nonuniform cross flow. The model incorporates all motion-dependent fluid forces based on the unsteady-flow theory. In the unstable region associated with a TSP-inactive mode, tube motion can be described by two linear models: TSP-inactive mode when tubes do not strike the TSP, and TSP-active mode when tubes do strike the TSP. The bilinear model (consisting of these linear models) presented here simulates the characteristics of fluidelastic instability of loosely supported tubes in stable and unstable regions associated with TSP-inactive modes. Analytical results obtained with the model are compared with published experimental data; they agree reasonably well. The prediction procedure presented for the fluidelastic instability response of loosely supported tubes is applicable to the stable and unstable regions of the TSP-inactive mode.
The Elastic-Plastic Analysis of Tubes—II: Variable Loading
Authors: Jiang W.
Published: June 2008

This paper is concerned with the elastic-plastic analysis of tubes subjected to variable loads. The yield condition for a material having residual stress and strain is first derived. Then by incremental method, the stresses and strains of the tube at any loading stage can be found. A closed-form solution is achieved as an example of tubes incurring ratchetting, and a general program is developed to make the theory applicable to complex loading situations.
The Elastic-Plastic Analysis of Tubes—IV: Thermal Ratchetting
Authors: Jiang W.
Published: June 2008

This paper continues the investigation of the shakedown behavior of tubes subjected to cyclic centrifugal force and temperature, and sustained internal and external pressures. It is found that when ratchetting occurs, the plastic strain builds up with each cycle, but finally reaches a steady state after a large number of cycles for kinematic hardening materials. The steady solutions for three kinds of ratchetting behavior are found and given in this paper.
Stresses of Thick Perforated Plates With Reinforcement of Tubes and Their Effective Elastic Constants
Authors: Hwang K. C. , Xue M. D. , Wen X. F. , Chen G.
Published: June 2008

Based on the concept of equivalent solid plate, this paper deals with thick perforated plates with triangular or square patterns of holes reinforced by tubes. The results obtained show that the tubes connected (by welding or expanding) to the perforated plates lead to a noticeable stiffening effect which is neglected or considerably underestimated by current design codes. The stresses of tubesheets calculated based on the effective elastic constants given by this method are in better agreement with the experimental results than those based on the effective elastic constants given by current codes.
Buckling Strength of Lining Shells of Pressure Vessels
Authors: Shimizu Y. , Moriwaki Y.
Published: June 2008

In this paper, the buckling strength of the lining shells inside the pressure vessel was investigated both theoretically and experimentally. First, the bifurcation buckling analysis of the lining shells was carried out with the aid of the newly developed computer program. In the analysis, the lining could be considered to be a shell subjected to external pressure and encased in a rigid cavity. The concepts of the matrix displacement approach to discrete element structural analysis were extended to predict the instability of shells of revolution encased in rigid cavity. The equilibrium solution for prebuckling was axisymmetric, but the perturbation-displacement field within each element was represented by Fourier circumferential components of the generalized displacements. Second, several experiments on the buckling of cylindrical shell under uniform external pressure were conducted. In the experiments, outward radial displacement of the shell specimen was constrained. The experimental results agreed with the analytical ones by the computer program. Furthermore, numerical calculations were conducted for several kinds of lining shells, whose results were compared with the analytical ones for unrestrained shells.