bluuebunny/crossref_metadata_2025 huggingface dataset:
Elastic-Plastic Analyses of Surface Flaws in a Reactor Vessel
Authors: Wilkening W. W. , deLorenzi H. G. , Barishpolsky M.
Published: November 2009

Elastic-plastic analyses have been performed for the ASME Maximum Postulated Flaw and for three other semielliptical surface flaws in the beltline region of a nuclear reactor pressure vessel, with internal radius to thickness ratio, R/t, equal to 10, using nonlinear 3-D finite element methods based upon the deformation theory of plasticity. Three of the flaws had a maximum depth, a, equal to t/4, with aspect ratios, 2c/a, equal to 6 (the ASME Maximum Postulated Flaw), 4 and 3, respectively, where 2c is the surface length of the flaw. These flaws were analyzed for internal pressure varying from one to three times the design pressure, which is well into the fully plastic regime for the uncracked vessel. The fourth flaw had an aspect ratio, 2c/a, equal to 6, and its maximum depth, a, was equal to 3t/4. This deep flaw was analyzed for internal pressure varying from 60 percent of design pressure to twice the design pressure. The crack driving force was calculated as the energy release rate, J, using the virtual crack extension method. The results illustrate that, at the design pressure, plasticity near the crack front is so limited for the three flaws with a/t = 1/4 that an elastic analysis is adequate. At higher pressures, however, the elastic analyses become increasingly nonconservative and would grossly underestimate the severity of the flaws. The variation of both J and crack opening displacement, COD, along the crack front were studied. Generally, the values at the maximum depth location, denoted J* and COD*, respectively, were the maximum values, with minimum values occurring at the free surface. A simple normalization scheme was found which collapsed the J* versus pressure results for the four semielliptical flaws into a single curve. A similar normalization also collapsed the COD* versus pressure results for the four flaws into a single curve. In addition, a unique linear relationship between J* and COD* was found to apply for the results from all four sets of analyses for internal pressure levels up to at least 2.5 times the design pressure. The analyses therefore demonstrate that J and COD are equivalent measures of the crack driving force, and further demonstrate that a realistic 3-D elastic-plastic analysis is needed to properly assess the severity of surface flaws.
Fatigue Crack Growth in Large Specimens With Various Stress Ratios
Authors: Ellyin F. , Li H.-P.
Published: November 2009

An experimental investigation has been carried out on large plates made of pressure vessel steel A516 Gr.70, to determine the fatigue crack growth rate. The specimen size was 914.4 × 304.8 × 12.7 mm (36 × 12 × 0.5 in.) with an initial central through crack of about 92 mm (3.6 in.). The stress ratio, R, applied to the specimens varied from zero to 0.4. This ratio was maintained constant during a test, but the stress amplitude, Δσ, at times was increased in order to obtain data under a large range of stress intensity factor, ΔK. The crack growth rate, da/dN, is expressed in terms of stress intensities, ΔK and Kmax, through a power-law-type equation. The variation of material constants with the applied stress ratio is discussed. From the data analysis, a general equation for the crack propagation rate is suggested in the form of da/dN = C (Kmax)n where C and n are functions of ΔK, Kmax and material parameters. The results are also compared with the recommended ASME Code formula and are found to be in fairly good agreement.
Consistent Hydrodynamic Mass for Parallel Prismatic Beams in a Fluid-Filled Container
Authors: Loeber J. F.
Published: November 2009

In this paper, representation of the effects of incompressible fluid on the dynamic response of parallel beams in fluid-filled containers is developed using the concept of hydrodynamic mass. Using a two-step process, first the hydrodynamic mass matrix per unit (beam) length is derived using finite element methods with a thermal analogy. Second, this mass matrix is distributed in a consistent mass fashion along the beam lengths in a manner that accommodates three-dimensional beam bending plus torsion. The technique is illustrated by application to analysis of an experiment involving vibration of an array of four tubes in a fluid-filled cylinder.
Cyclic Plastic Deformation of a Circular Plate With Work Hardening
Authors: Winter R.
Published: November 2009

An experimental and theoretical study was performed of the nonlinear behavior of a simply supported flat circular aluminum plate under reversed cyclic central load. The application is for the analysis of cyclic stress and strain of structural components in the plastic range for predicting low-cycle fatigue life. The main purpose was to determine the relative accuracy of an elastic-plastic large deformation finite element analysis when the material properties input data are derived from monotonic (noncyclic) stress-strain curves versus that derived from cyclic stress-strain curves. The results showed that large errors could be induced in the theoretical prediction of cyclic strain range when using the monotonic stress-strain curve, which could lead to large errors in predicting low-cycle fatigue life. The use of cyclic stress-strain curves, according to the model developed by Morrow, et al., proved to be accurate and convenient.
An Exact Modal Analysis of the Static Deformation of Long Cylinders and Rings
Authors: Fisher H. D.
Published: November 2009

This paper presents a static, modal solution of Flugge’s thin shell equations for the cases of a ring or a long cylinder in a state of plane strain. The solution derived here enables the design analyst to compute the deflection resulting from concentrated loads applied in the plane of the cross section at an arbitrary angle to the circumference of the shell and to eliminate the error which results, in certain cases, from employing a previously derived inextensional analysis. A general solution is given for the case of any number of concentrated radial, tangential, and moment loads. The method of analysis for loadings that are a continuous function of the angular variable is also illustrated via a specific example. Numerical results compare solutions obtained with the present theory with those computed by invoking the assumption of inextensional deformation.
Some Considerations on Estimation of Energy Release Rates for Circumferentially Cracked Pipes
Authors: Pan J.
Published: November 2009

The estimation of energy release rates under multiple loading conditions is discussed from the viewpoint of variation of the potential energy of the nonlinear elastic cracked body. Applications of this concept to pipes with a circumferential through-wall crack under combined bending and constant tension conditions are reviewed. For a part-through-wall crack, a simple perturbation analysis of a pipe with an internal circumferential surface crack under combined bending and constant tension gives the variation of the energy release rate J along the circumferential surface crack front. The results suggest that the common assumption of uniform crack growth in the radial direction for a circumferential surface crack with a uniform crack depth [5] is not generally valid.
Stresses and Displacements in Vessels due to Loads Imposed by Single and Multiple Piping Attachments
Authors: Wong F. M. G. , Craft W. J. , East G. H.
Published: November 2009

The Fourier solution for thin shell equations models pressure vessels as continuous simply connected surfaces with local loads. The technique allows placement of tractions with combinations of radial, shear, and axial components. Unlike Bijlaard, the solution in this paper includes loads placed at any position along the cylinder. Stiffness and the enhanced load-carrying capacity that internal pressure gives to thin vessels can be simulated. Numerical convergence problems are reduced by an improved displacement-load algorithm, and by use of load sites that allow the circular functions to be compactly grouped. A variety of loading distributions may be analyzed including large and small nozzles near and away from centerlines. Both rectangular and circular attachments are simulated. Through superposition, multiple attachments with their own loads may be examined. The attachments to the vessel may be either rigid or soft. A comparison to analytical results from Bijlaard shows excellent agreement. Comparisons with experimental tests on an API-650 nozzle on a storage tank are in good agreement. Variations between experimental and calculated results are primarily caused by assuming a simply supported base in the calculation, whereas in the experimental test, the base is more nearly fixed.
Elastic Analysis of Beam-Support Impact
Authors: Salmon M. A. , Verma V. K. , Youtsos T. G.
Published: November 2009

The effect of gaps present in the seismic supports of nuclear piping systems has been studied with the use of such large general-purpose analysis codes as ANSYS. Exact analytical solutions to two simple beam-impact problems are obtained to serve as benchmarks for the evaluation of the ability of such codes to model impact between beam elements and their supports. Bernoulli-Euler beam theory and modal analysis are used to obtain analytical solutions for the motion of simply supported and fixed-end beams after impact with a spring support at midspan. The solutions are valid up to the time the beam loses contact with the spring support. Numerical results are obtained which show that convergence for both contact force and bending moment at the point of impact is slower as spring stiffness is increased. Finite element solutions obtained with ANSYS are compared to analytical results and good agreement is obtained.
Weight and Cost Optimization of Hydrostatically Loaded Stiffened Flat Plates
Authors: McGrattan R. J.
Published: November 2009

Plates with longitudinal or orthogonal tee-stiffeners subjected to differential pressure are used in many structures. Equations to achieve minimum weight and cost are presented. Energy methods and plate gridwork theory are used. The accuracy of the technique is verified for typical designs by excellent comparison with stresses calculated by finite-element analysis. Minimum weight and cost studies using an optimization program are presented. Numerous small stiffeners minimize weight, whereas fewer, large stiffeners minimize cost. Fifteen independent structural variables are used for orthogonally stiffened plates. Stress, deflection, stability, and minimum thickness constraints are applied. Rapid optimum designs are achieved economically.
Asymmetric Modes and Associated Eigenvalues for Spherical Shells
Authors: Singh A. V. , Mirza S.
Published: November 2009

Free asymmetric vibration of spherical shells with clamped and hinged boundary conditions are analyzed using the finite element method. Element stiffness and consistent mass matrices are derived using the improved shell theory, which takes into account the effects of shear deformation and rotary inertia. Natural frequencies for a wide spectrum of shell geometry ranging from shallow cap to hemispherical shell have been computed and are found to be in close agreement with the available data in the literature.
Plastic Buckling of Short Vertical Cylindrical Shells Subjected to Horizontal Edge Shear Loads
Authors: Galletly G. D. , BŁachut J.
Published: November 2009

Vertical liquid-filled cylindrical shells which are subjected to horizontal seismic loads can fail by buckling in shear. One example where this might arise in the nuclear industry is with the primary vessel in a fast breeder reactor (LMFBR) and design criteria are, therefore, needed to prevent its occurrence. In the present paper, the static analogue of the foregoing problem is considered and experimental results on the plastic buckling of short, steel cantilevered cylindrical shells subjected to transverse edge shearing loads are presented. In addition, a simple quadratic equation is suggested for predicting the plastic shear buckling loads. The agreement between the experimental shear loads at the inception of buckling and the predictions of the proposed design equation is excellent for the limited range of geometries investigated.
Seismic Response Analysis of Cylindrical Tanks With Initial Irregularities on Side Walls
Authors: Zui H. , Shinke T.
Published: November 2009

The objective of this paper is to report the findings of the study on the effects of initial irregularities on the seismic response of cylindrical tanks. The initial irregularities induce circumferential hydrodynamic pressure components of high-order modes, which are neglected in current design assumptions. Seismic response formulas for cylindrical tanks with arbitrary initial irregularities have been derived from Lagrange’s kinematic equation taking into account natural frequencies, vibrational modes and the hydrodynamic pressure. The hydrodynamic pressure in an irregular tank is evaluated by using velocity potential function. Natural frequency analysis is done by means of the transfer matrix method taking into consideration the initial hoop stress. The effect of aspect ratio H/D (H: liquid height and D: tank diameter) and the shape of initial irregularities are further examined by numerical calculations.
A Simplified Finite Element for Added Mass and Inertial Coupling in Arrays of Cylinders
Authors: Harris R. E. , Dokainish M. A. , Weaver D. S.
Published: November 2009

A simplified finite element has been developed for modeling the added mass and inertial coupling arising when clusters of cylinders vibrate in a quiescent fluid. The element, which is based on two-dimensional potential flow theory, directly couples two adjacent beam elements representing portions of the adjacent cylindrical structures. The primary advantage of this approach over existing methods is that it does not require the discretization of the surrounding fluid and, therefore, is computationally much more efficient. The fundamental frequencies of tube bundles of various pitch ratios have been predicted using this method and compared with experimental data. Generally, the agreement is good, especially for the bandwidth of fluid coupled natural frequencies. The transient response of tube bundles is also examined using time integration of the finite element model. The beating phenomenon and time decay characteristics exhibited by the experimental bundles under single-tube excitation are well predicted and valuable insights are gained into the measurement of damping in tube bundles.
A Simplified Analysis Method for Complex Piping Systems in Elastic-Plastic-Creep Range
Authors: Watanabe O. , Ohtsubo H.
Published: November 2009

The present paper describes a simplified finite element method for analysis of behavior of complex piping systems under elevated temperature. Elastic-plastic-creep deformations of a piping system under a combined moment loading can be analyzed by the present method. The system is idealized by straight and curved beams, and derivation of the finite element equation is based on the force method. The unified constitutive relations are used for creep and plastic behavior, where plastic deformation is treated as a limiting case of creep. The numerical results are compared with previous experimental ones, which verifies the validity of the proposed method. Elastic follow-up problem of a piping system of actually complex configuration is also solved by the present method.
A Procedure to Incorporate Effects of Seismic Events in a Quasi-Static Piping System Inelastic Analysis
Authors: Rotoloni D. F. , Dhalla A. K.
Published: November 2009

Inelastic analysis of a prototypic liquid metal fast breeder reactor (LMFBR) piping system is generally performed without explicit consideration of time-dependent seismic loading. This paper presents an approximate procedure to simulate dynamic seismic loading as an equivalent static load for inelastic analysis. This procedure utilizes the results of the available linear seismic response spectrum analysis to calculate external (statically equivalent) loads. These statically equivalent loads are selected such that they produce internal forces and moments comparable to those predicted by the linear response spectrum analysis.
Determination of Residual Stresses due to Girth-Butt Welds in Pipes
Authors: Chandra U.
Published: November 2009

A state-of-the-art review of analytical and experimental determination of residual stresses due to girth-butt welds in pipes is presented. In the analytical category, closed-form as well as numerical (finite element) solutions are discussed in considerable detail. The results of the experimental studies, with primary focus on the X-ray diffraction (XRD) technique, are highlighted. The effects of process and geometric parameters and of various thermal processes in controlling the tensile residual stress on the pipe inner surface are also reviewed.
X-Ray Diffraction Measurement of Residual Stresses in Thick, Multi-Pass Steel Weldments
Authors: Ruud C. O. , Pangborn R. N. , DiMascio P. S. , Snoha D. J.
Published: November 2009

A unique X-ray diffraction instrument for residual stress measurement has been developed that provides for speed, ease of measurement, accuracy, and economy of surface stress measurement. Application of this instrument with a material removal technique, e.g., electropolishing, has facilitated detailed, high resolution studies of three-dimensional stress fields. This paper describes the instrumentation and techniques applied to conduct the residual stress measurement and presents maps of the residual stress data obtained for the surfaces of a heavy 2 1/4 Cr 1 Mo steel plate weldment.
Application of the Failure Assessment Diagram to the Evaluation of Pressure-Temperature Limits for a Pressurized Water Reactor
Authors: Yoon K. K. , Bloom J. M. , Pavinich W. A. , Slager H. W.
Published: November 2009

The failure assessment diagram approach, an elastic-plastic fracture mechanics procedure based on the J-integral concept, was used in the evaluation of pressure-temperature (P-T) limits for the beltline region of the vessel of a pressurized water reactor. The main objective of this paper is to illustrate the application of an alternate fracture mechanics method for the evaluation of pressure-temperature limits, as allowed by the Code of the Federal Regulation 10 CFR 50, Appendix G. The evaluation of P-T limits for the beltline region of a pressurized water reactor was based on the following assumptions: • ASME Pressure Vessel and Piping Code, Section III, Appendix G reference flaw • End-of-life fluence level in the beltline region • Longitudinal flaw in the beltline weld • J-resistance material toughness curves obtained from the U.S. Nuclear Regulatory Commission’s heavy section steel technology (HSST) program • Other material properties obtained from the Babcock & Wilcox Integrated Reactor Vessel Material Surveillance Program The maximum allowable pressure levels were calculated at 33 time points along the given reactor bulk coolant temperature history representing the normal operation of a pressurized water reactor. The results of the calculations showed that adequate margins of safety on operating pressure for the critical weld in the beltline of the pressurized water reactor vessel are assured.
Dissimilar Metal Weld and Boiler Creep Damage Evaluation for Plant Life Extension
Authors: Viswanathan R.
Published: November 2009

The basic causes of dissimilar metal weld (DMW) failures in boilers are now well understood. Guidelines have emerged for achieving significantly improved DMW life, in terms of operational parameters, weld filler metals, and weld designs. Analytical, as well as experimental, nondestructive techniques have been developed that enable assessment of the condition of DMWs in service so that intelligent run-replace decisions can be made. Techniques for assessing the remaining life of superheater/reheater (SH/RH) tubes are under development. The techniques utilize information on steamside oxide scale growth and dimensional changes on the fireside due to corrosion to compile the temperature–stress profile of operation in the tubes. This information is then combined with standard creep data to estimate the remaining life of the tubes more accurately than was possible heretofore. The potential of a replication technique that allows nondestructive monitoring of creep damage in heavy section pipes has been successfully demonstrated at several utility sites. It has been possible to detect early stages of incipient creep damage and to recommend specific courses of action to affected utilities. Laboratory and field studies currently in progress are expected to result in metallographic and miniature test specimen techniques that would further augment the capabilities of the replication technique, and render it into a more quantitative tool for life assessment of heavy section components.
Monitoring the Service-Induced Damage in Utility Boiler Pressure Vessels and Piping Systems
Authors: Harth G. H. , Sherlock T. P.
Published: November 2009

Electric utilities are becoming more concerned about extending the life of older fossil-fueled power plants. Of particular interest are methods for estimating the remaining useful life of steam headers and main steam piping. This paper discusses different methodologies for determining exhausted and remaining life of these components. An example of a header which was found to have exhausted its useful life is also presented.
The Fatigue-Crack Growth and Ductile Fracture Toughness Behavior of ASTM A387 Grade 91 Steel
Authors: James L. A. , Carlson K. W.
Published: November 2009

Fatigue-crack growth tests were conducted on three heats of wrought material plus one heat of weldment at temperatures of 24, 316, 427, 538, and 593° C. The effects of heat-to-heat variations, crack orientation, and thermal aging were studied. In addition, stress ratio effects were characterized at 427° C. The J-integral technique was used to determine the ductile fracture toughness at room temperature. Both the multiple specimen and unloading compliance techniques were used, and differences between the two methods are discussed.
A Mechanistic Approach to Remanent Creep Life Assessment of Low Alloy Ferritic Components Based on Hardness Measurements
Authors: Cane B. J. , Aplin P. F. , Brear J. M.
Published: November 2009

Creep damage leading to failure in low alloy ferritic steels at service operating conditions results from: (i) structural coarsening leading to a continuous reduction in creep strength during exposure, and (ii) intergranular creep cavitation. A mechanistic model is presented for describing tertiary creep which accounts for both of these factors. By assuming a limiting creep ductility corresponding to a maximum cavitation potential a lower bound life predictive approach is given. The significant structural parameters are then the background solid solution strength, the interparticle spacing (λ) and the rate of increase of λ, although the long-term, creep-rupture strength is shown to be dictated largely by the latter. Consideration is given to the determination of these kinetics by means of hardness change measurements: good correlations are found with experimental data. A methodology for characterizing the remanent creep life of component material using hardness measurements and post-exposure aging is developed on this basis.
A Practical Strategy for Life Evaluation and Extension of Fossil-Fuel-Fired Boilers
Authors: Gupta G. D. , Ahluwalia K. S. , Rao M. S. , Blough J. L. , Cocubinsky J.
Published: November 2009

Facing escalating costs for new generating facilities and regulatory and economic uncertainties, electric utilities are increasingly postponing construction of new power plants and are instead exploring ways to extend the life of the older plants well beyond their intended design life. Much work has been performed on a worldwide basis in recent years to develop analytical and experimental methods to determine the remaining life of boiler components. The diversity of the methods developed and their relative merits leaves practicing engineers with an unclear definition of a practical approach to life evaluation, especially for high-temperature components. This paper presents a practical strategy for boiler life evaluation and extension using proven techniques. While not losing sight of recent developments, the emphasis is on using methods that are inexpensive, fast, and proven. The approach is currently in use on a commercial basis and is continually being updated to reflect new information as it becomes available.
Vibration of Piping Systems Containing a Moving Medium
Authors: To C. W. S. , Kaladi V.
Published: November 2009

The subject of vibration of piping components containing a moving medium has been studied extensively in the past three decades. Special attention has been paid on the instability of uniform and tapered tubes with various boundary conditions. On the other hand, very limited information is available for complex piping systems carrying a moving medium. This paper proposes a transfer matrix method for the vibration analysis of complicated piping networks involving bends, piping components of various diameters, and lumped masses such as valves with a moving medium. Closed-form transfer matrix for various piping elements incorporating the Coriolis effects are presented and discussion is made. The proposed approach is much more economical to use than the versatile finite element method. Moreover, it can be easily implemented in a microcomputer.
Transient Hydroelastic Vibration of Piping With Local Nonlinearities
Authors: Keskinen R. P.
Published: November 2009

A mode superposition algorithm is presented to solve fluid and structural dynamics problems in piping systems with a local cross-sectional material nonlinearity, such as cavitation of fluid or circumferential cracking of the pipe material. Two families of eigenmodes are used to decompose the total response into so-called compatibility-controlling and resistance-controlling responses which satisfy the governing partial differential equations. The responses are simultaneously solved in time by means of convolution integral techniques. Either response is always predicting for the other an additional excitation—load or displacement—at the nonlinear cross section in such a manner that the resulting boundary conditions fully simulate the inelastic material behavior. The algorithm is applied to a test problem of waterhammer-induced coupled acoustic and mechanical piping vibrations with cavitating fluid. The coupling is shown to reduce the dynamical loading of the pipe and to eliminate unrealistic beating of closely spaced acoustic and mechanical eigenmodes appearing in uncoupled analysis.
Pipe Whip—Bounding the Required Restraint Capacity
Authors: Peek R.
Published: November 2009

Energy balance methods commonly in use for the design of pipe whip restraints are based on the solution for the motion of a rigid-plastic pipe before impact against the restraint, with the assumption that after impact, the whipping portion of the pipe continues to rotate about the plastic hinge location determined for conditions before impact. Such energy balance methods are not necessarily conservative because: 1) the plastic hinge which forms in the pipe moves after impact on the restraint; and 2) elastic pipe deformations are not considered. Here, upper and lower bounds to the required restraint capacity are derived. In contrast to finite element methods, which are very time-consuming, the upper and lower bounds can be evaluated by simple hand calculations. Another advantage is that the required restraint capacity is calculated directly. No trial and error design is required. A numerical example shows that for a typical pipe and restraint, the upper and lower bounds differ by as little as 20 percent.
An Assessment of Frequency-Dependent Damping Using the Nuclear Piping System Damping Data Base
Authors: Ware A. G.
Published: November 2009

The existing nuclear piping damping data base is examined to assess the relation between frequency and damping in the seismic range (0 to 33 Hz). A conclusion is reached that the published data supports such a correlation for individual systems, and that this relation offers suitable advantages for use in establishing allowable damping values for seismic analyses. The data base for higher frequency systems subjected to flow-induced loads is presently very meager, and thus a corresponding assessment cannot be made.
Comparison and Evaluation of Analytical Structural Solutions With EPRI Safety Valve Test Results
Authors: Smith L. C. , Adams T. M.
Published: November 2009

All operating plant licensees and applicants are required to verify the acceptability of plant specific pressurizer safety valve piping systems for valve operation transients by testing per NUREG-0737 (issued November, 1980) and all subsequent U.S. NRC generic follow-up letters. Of particular concern was the operability of the safety valves and the acceptability of the downstream piping when subjected to the dynamic thermal hydraulic loadings associated with these transients. To aid in this verification process the Electric Power Research Institute (EPRI) conducted an extensive program testing different safety valves subjected to varying operating conditions. Downstream piping loads associated with the various loading cases were also measured. This paper presents and compares analytically determined solutions for the structural response of the test configuration to actual test results. A brief description of the methods used to generate the thermal hydraulic loads is presented but the major emphasis is on the piping dynamic response. Discussed are the piping and support modeling techniques, the dynamic solution methods and the load application methods employed. Analytically calculated piping stresses, support loads, displacements, and valve nozzle loads are compared to the test results.
Design for Buckle-Free Shapes in Pressure Vessels
Authors: Szyszkowski W. , Glockner P. G.
Published: November 2009

There are many applications of thin-walled axisymmetric structures as pressure vessels in which buckle-free in-service behavior can only be guaranteed by reinforcements, such as stringers and girths, which not only raise the weight of the structure but also increase its cost. Buckle-free behavior, however, can also be assured by “correcting” the shape of the pressure vessel by a small amount in the area of impending instability. This paper proposes the use of the theory of inflatable membranes to obtain the shape of a pressure vessel subjected to tension only stress state, whereby the possibility of buckling is excluded. Such a shape will be referred to as the “buckle-free” shape. A set of nonlinear differential equations are derived which are valid for any axisymmetric pressure vessel subjected to axisymmetric loadings. The shape obtained from the solution of the equations is an “extremum” to possible stable shapes under the given loading conditions; i.e., there are other stable shapes, for which the circumferential compressive stiffness of the structure has to be relied upon. A closed-form solution for the set of equations was obtained for the constant pressure loading case. For hydrostatic pressure a numerical procedure is applied. Results on “buckle-free” shapes for typical pressure vessel strucures for these two loading conditions are presented. It is established that the deviation of such shapes from the shapes obtained by present design methods and code specifications is small so that this proposed method and the resulting “corrections’ leading to “buckle-free” inservice behavior should not present an aesthetic problem in design.
Improvement of Residual Stresses of Circumferential Joint of Pipe by Heat-Sink Welding
Authors: Ueda Y. , Nakacho K. , Shimizu T.
Published: November 2009

Intergranular stress corrosion cracking may occur in some specific conditions on the inner surface of the welded joints of stainless steel pipes which are furnished in nuclear plants. One of the remedies for this cracking is to convert welding residual stress on this surface into compression. In this research, in order to improve welding residual stress, the authors investigated the effectiveness of the heat-sink welding (water cooling) by conducting theoretical analyses and experiments on SUS 304 pipes of different sizes in comparison with the conventional welding. The mechanisms of production of residual stresses by both methods are clarified and conditions for effective application of the heat-sink welding such as limitation of heat input, procedure of welding are indicated.
Decoupling of Secondary Systems for Seismic Analysis
Authors: Hadjian A. H. , Ellison B.
Published: November 2009

Interest in the decoupling of such secondary systems as floor-mounted equipment centers on two decoupled models, the “cascading” model and the “lumped” model. A set of decoupling criteria is derived which addresses both models. The solution is based on the two-degree-of-freedom system. Error in predicted frequency given by each decoupled model is presented. Similar results for response error are derived based on broad-band input to the supporting system. The broad-band input would be applicable to subsystems supported by primary structures. Recommendations are made for extension of the problem to arbitrary multiple-degree-of-freedom systems. The findings of this study will provide the analyst with the information necessary to choose the best decoupled model and will indicate whether decoupling should be attempted.
Analysis on Fatigue Crack Growth Rates Under a Wide Range of Stress Ratios
Authors: Kurihara M. , Katoh A. , Kawahara M.
Published: November 2009

In the present study, a series of fatigue crack growth tests were carried out in order to examine the effects of stress ratio R upon crack growth rates, together with the crack closure behaviors. Fatigue tests were conducted with center-notched specimens of two kinds of pressure vessel steels (500 MPa class and 800 MPa class) under cyclic axial loading in various stress ratios R ranging from −5 to +0.8. Crack opening stress levels were determined by the unloading elastic compliance method. An expression of fatigue crack growth rates under a wide range of stress ratios was proposed, taking into account the relationship between stress ratio R and crack opening stress ratio U. The crack growth behaviors near the threshold conditions were also discussed.
An Evaluation of Several Constitutive Model Structures for Transient
Nonproportional Cyclic Plasticity
Authors: Sotolongo W. , McDowell D. L.
Published: November 2009

Four constitutive models for cyclic plasticity of different essential structure are evaluated under conditions of nonproportional, multiaxial loading. Drucker’s one-surface theory, McDowell’s two-surface theory, Krieg’s one-surface theory with Radial-Return Integration Algorithm, and Abrahamson’s Unified Creep-Plasticity theory are the constitutive models under consideration. Their transient hardening and stable loop responses are compared to experimental data for two nonproportional axial-torsional loading histories. Their computational efficiency is also analyzed.
Results From Dynamic Tests and Analyses of a Medium Diameter LMFBR
Piping System
Authors: Schott G. A. , Hulbert G. M. , Heberling C. F.
Published: November 2009

This paper presents results and observations from dynamic tests and analyses performed on an 8-in. (0.20-m) diameter, thin-walled piping system. The piping system is a scaled representation of a Liquid Metal Fast Breeder Reactor (LMFBR) large diameter piping loop. Prototypic piping restraints were employed, including mechanical snubbers, rigid struts, pipe hangers and nonintegral pipe clamps. Snap-back, sine-sweep and seismic tests were performed for various restraint configurations and piping conditions. The test results are compared to analytical predictions for verification of the methods and models used in the seismic design of LMFBR piping systems. Test program conclusions and general recommendations for piping seismic analyses are presented along with a discussion of test and analysis results.
Predicting Bellows Response by Numerical and Theoretical
Methods
Authors: Becht C.
Published: November 2009

This paper provides a history of the development of bellows analysis methods from early work in the 1940s to the present. The state of the art is assessed, and directions requiring further development are discussed.
Emergency Response Guidance for Reactor Vessel Pressurized Thermal
Shock Events
Authors: Kaiser W. T. , Monty B. S.
Published: November 2009

The operational concern of pressurized thermal shock (PTS) can be minimized by proper operator guidance. This paper presents a method for calculating a pressure temperature limit curve for reactor vessel integrity which can be used to identify an ongoing potential PTS event. This method has been developed for use and is applicable to all pressurized water reactors. The curve is used in emergency operating procedures developed to prioritize various plant safety concerns including PTS and core cooling to ensure proper operator action during accident conditions. This paper emphasizes the development of the pressure-temperature limit and how it is used within the emergency operating procedures.
The Dynamics of Heat Exchanger U-Bend Tubes With Flat Bar
Supports
Authors: Yetisir M. , Weaver D. S.
Published: November 2009

A theoretical study has been conducted to investigate the effect of flat bar supports on the dynamic response of a heat exchanger U-tube. The tube was modeled using 3-D, six degrees of freedom per node beam finite elements and excited at its lowest three natural frequencies. The equations of motion were integrated and the time response was analysed using a Fast Fourier Transform Algorithm. The modal frequency and dissipation contributions were determined and the effects of support friction and clearance and excitation magnitude were investigated.
Heat Conduction Through a Layered Pressure Vessel
Wall
Authors: Ueda M. , Kinugawa M. , Hara Y. , Yamazato K.
Published: November 2009

Heat conduction tests of a layered pressure vessel wall were performed using full-scale model pressure vessel courses. Thermal conductance between layers was estimated from the test results. A simplified method, developed for the thermal analysis of layered-wall pressure vessels during postweld heat treatment and actual operation, includes thermal contact conductance at the layer interfaces which depends upon the contact pressure and gap height. Temperature changes calculated using the simplified method agreed well with the experiments.
Numerical Estimate of Elastic Follow-Up in Piping: Inelastic
Evaluation
Authors: Dhalla A. K.
Published: November 2009

Large-diameter thin-walled piping such as that used in the Liquid Metal Fast Breeder Reactor (LMFBR) plant is characterized by relatively stiff straight pipes welded to flexible elbows. According to Robinson [1], such a piping system configuration may experience elastic follow-up during elevated temperature operation. Therefore, ASME Code Case N-47 requires that the secondary thermal expansion stress “. . . with large amounts of elastic follow-up . . .” be considered a load-controlled primary stress. A procedure to calculate the extent of potential elastic follow-up and thereby classify the thermal expansion stress as either primary or secondary is presented here. The elastic follow-up effect is investigated in detail by evaluating spatial and temporal redistribution of loads and inelastic strains computed for a typical LMFBR piping system.
Verification of an Elastic Procedure to Estimate Elastic
Follow-Up
Authors: Dhalla A. K.
Published: November 2009

This paper presents a simplified elastic procedure to estimate the amount of elastic follow-up due to thermal expansion stress experienced by a large diameter (greater than 200 mm) thin-walled (d/t greater than 30) piping system. The simplified method utilizes the concept of reduced elastic modulus which was successfully applied to classify clamp-induced pipe stresses into primary and secondary categories. The conservatism of the simplified method in quantifying elastic follow-up is illustrated in this paper by comparing the numerical estimate of elastic follow-up with that obtained from a detailed creep analysis of a Liquid Metal Fast Breeder Reactor piping system.
Recertification of Pressure Vessels and Pressure
Systems
Authors: Selz A.
Published: November 2009

There are strong economic and safety incentives to recertify pressure vessels, pressure components, and piping for continued service after their nominal original design life has been exhausted. No specific rules, and certainly no national consensus standards exist for doing this. Therefore, methods have been developed to rank vessels as to urgency for recertification, and a five-step recertification process has been devised. The five steps are: 1) gathering design and operating information, 2) performing basic analysis to establish maximum allowable working pressure (MAWP) and to identify high-stress areas, 3) performing visual and nondestructive examination, concentrating NDT in high stress areas, 4) performing detailed stress analysis to confirm MAWP, and 5) performing flaw-growth analysis to establish the interval between inspections. Experience has shown that recertification costs are between 10 and 15 percent of replacement costs and that recertification adds greatly to confidence in the safety and availability of equipment.
A Simple Design Equation for Preventing Buckling in Fabricated
Torispherical Shells Under Internal Pressure
Authors: Galletly G. D.
Published: November 2009

A simple equation is proposed which will enable a designer to estimate the onset of buckling in internally pressurized steel torispherical end closures. The equation applies to both crown and segment ends and spun ones. Apart from a factor which accounts for strain hardening, the same equation applies to both carbon steel and austenitic stainless steel torispheres. The proposed equation for the allowable internal pressure was checked against all known experimental buckling results and a minimum factor of safety of 1.5 was found. The equation was also checked against a number of full-scale vessels, some of which had failed in service. Once again, the equation was found to be satisfactory.
RMS Fatigue Curves for Random Vibrations
Authors: Brenneman B. , Talley J. Q.
Published: November 2009

Fatigue usage factors for deterministic or constant amplitude vibration stresses may be calculated with well-known procedures and fatigue curves given in the ASME Boiler and Pressure Vessel Code. However, some phenomena produce nondeterministic cyclic stresses which can only be described and analyzed with statistical concepts and methods. Such stresses may be caused by turbulent fluid flow over a structure. Previous methods for solving this statistical fatigue problem are often difficut to use and may yield inaccurate results. Two such methods examined herein are Crandall’s method and the “3σ” method. The objective of this paper is to provide a method for creating “RMS” fatigue curves” which accurately incorporate the requisite statistical information. These curves are given in Appendix A and may be used by analysts with the same ease and in the same manner as the ASME fatigue curves.
Impacting of Pipes on Elastic Supports
Authors: Kumar R.
Published: November 2009

Piping systems are often provided with supports and restraints with gaps to reduce the thermal stresses and to limit the motion caused by other loads, e.g., due to pipe rupture or seismic effects. However, the presence of the gap causes the pipe to impact on the support under dynamic loading. In this paper the impacting effects have been studied using a simple model. The effect of support rigidity on the impact force, bending moment and deflection of the pipe has been evaluated. The bending moment at the impact loading is found to decrease up to a certain value of the support stiffness beyond which it increases. However, the impact force increases and the overall deflection at the impact location decreases continuously as the support stiffness is increased. The results are presented in nondimensional form as ratios of the appropriate quantities for the simply supported pipe with no elastic restraint. Thus, they provide useful information for design considering impact effects.
Virtual Crack Extension Method for Energy Release Rate Calculations in Flawed Thin Shell Structures
Authors: LeFort P. , deLorenzi H. G. , Kumar V. , German M. D.
Published: November 2009

The calculation of the energy release rate, G, by the virtual crack extension method has been used extensively in the literature over the last few years. A formulation and implementation of the energy release rate for use with 8 and 9-noded isoparametric thin shell elements is described in this paper. The representation used in the paper allows the calculation of G either as an integral part of a finite element analysis or separately in a postprocessing program using the stress and strain data from a finite element analysis as input. The results presented in the paper are compared with those published in the literature for several elastic as well as elastic-plastic crack problems.
Dynamic Photoelastic Study of Crack-Wave Interaction in Thick-Walled Rings
Authors: Shukla A. , Rossmanith H. P.
Published: November 2009

A series of photoelastic experiments were conducted to study crack-wave interaction in thick-walled rings. Particular attention was paid to the initiation, propagation and branching of small flaws at the outer or the inner boundary of the ring due to stress waves generated from explosion. The results indicate that the crack once initiated propagates until it reaches either one of the two boundaries. Momentary crack arrests are possible during the experiment.
Interactive Buckling Tests on Cylinders Subjected to External Pressure and Axial Compression
Authors: Galletly G. D. , James S. , Kruzelecki J. , Pemsing K.
Published: November 2009

The results of 40 buckling tests on unstiffened welded steel cylindrical shells subjected to combined axial compression and external lateral pressure are compared in the paper with the predictions of theory and various Codes (ASME III, DnV and ECCS). The radius/thickness ratios of the models tested were R/t ≈ 100 and 300 and the length/radius ratios covered the range 0.18 < L/R < 1.45. Three interaction equations were studied, viz. a linear, a quadratic and a linear/quadratic equation suggested recently by Odland. Best agreement with experiment was obtained using the quadratic equation in conjunction with the DnV or ASME III Codes. The ECCS predictions of buckling stress were safe but were more conservative than the other two Codes. Some interactive buckling tests on ring-stiffened cylinders (and conducted recently by other workers) were also compared with the predictions of the above three Codes. The agreement between predicted buckling stresses and test results was broadly similar to that found for the Liverpool models. For very short unstiffened and ring-stiffened cylindrical shells, the theoretical interaction curves were a little unusual. In addition, the test results for external lateral pressure alone on these shells, and obtained by different research groups, did not all agree.
An Extrapolation Procedure of Creep Data for St Determination: With Special Reference to Cr-Mo-V Steel
Authors: Maruyama K. , Oikawa H.
Published: November 2009

A predictive rule for long-term creep data, necessary to determine St of the ASME Code, was proposed with special reference to a Cr-Mo-V steel. This rule can predict long-term creep curves as well as rupture lives. A creep curve three hundred times longer than the longest test was estimated without unreasonable extrapolation.