bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Analysis of Thermal Stresses During Welding Including Phase Transformation Effects
Authors: Papazoglou V. J. , Masubuchi K.
Published: November 2009

The problem of determining temperature distributions, transient thermal strains, and residual stresses during butt welding thick plates with the multipass GMAW process is solved using the finite element method. First, a nonlinear heat transfer analysis is performed taking into account the temperature dependence of the material properties, and convection and radiation surface heat losses. This is followed by a thermo-elastic-plastic stress analysis that incorporates phase transformation strains. Finally, the theoretical predictions are compared with experimentally obtained data showing good correlation.
The Effect of Time and Temperature on Residual Stresses in Austenitic Welds
Authors: Fidler R.
Published: November 2009

The influence of heat treatment, upon residual stresses in AISI 316-type welds, is studied by subjecting a number of highly restrained weldments to various heat treatment cycles. Measurements of residual stresses, made before and after heat treatment, are related to uniaxial data by means of the Larson-Miller parameter, and the mechanism of stress relaxation in austenitic welds is contrasted with that occurring in ferritic welds.
A Method for Determining Residual Stresses in Pipes
Authors: Popelar C. H. , Barber T. , Groom J.
Published: November 2009

A combined analytical and experimental method for inferring the residual stresses in a pipe formed by joining two sections with a girth butt weld is described. The relieved surface strains due to cutting the pipe in two are measured and fitted in a least-square sense to the strains predicted by an analysis of the sectioned pipes. This permits a prediction of the through-thickness distribution of the residual longitudinal normal and radial shear stresses at the site of the cut. The procedure is used to infer the residual stress distribution due to last-pass-heat-sink welding of two sections of 16-in- (400-mm-) dia pipe.
PAULA: A 3D Code for Analysis of Nonlinear Pipes
Authors: Lazzeri L. , Scala M. , Agrone M.
Published: November 2009

The three-dimensional nonlinear code PAULA is described; its finite element library makes it particularly useful for analysis of pipes. The problem of pipe whip is dealt with in some detail. Comparisons are given with a 2D code named FRUSTRA.
Computational Simulation of High-Speed Steady Homogeneous Two-Phase Flow in Complex Piping Systems
Authors: Bliss D. B. , Quackenbush T. R. , Teske M. E.
Published: November 2009

A study was undertaken to predict steady flow conditions in two-phase steam/water flows in safety/relief discharge piping systems. The homogeneous-equilibrium model was used for the two-phase flow along with the ASME Steam Tables in subroutine form as a state equation. The approach can also accommodate single-phase flows of superheated steam or subcooled liquid. Subroutines were developed to simulate flows through isentropic area changes, abrupt area changes, adiabatic constant area pipes with friction, valves, two-phase shock waves, and mass addition at pipe junctions. These subroutines were combined to predict conditions in arbitrary complex piping systems. Sample calculations which treat both single line and multiple-branch piping systems are included.
Elastic-Plastic Analysis of the Maximum Postulated Flaw in the Beltline Region of a Reactor Vessel
Authors: deLorenzi H. G.
Published: November 2009

A maximum postulated surface flaw in the beltline region of a PWR pressure vessel has been analyzed under elastic-plastic conditions. The analysis was performed using 3-D finite element methods, and the deformation theory of plasticity was used to describe the plastic flow of the material. The calculations were carried out for the internal pressure varying from the design pressure up to approximately twice the design pressure. The results show that at the design pressure the plastic flow of the material around the crack front is so small that an elastic analysis is adequate. However, the commonly used approach of treating the flaw in the vessel as a surface flaw in a flat plate under far field tension loading is nonconservative. At a pressure of approximately 50 percent over the design pressure the energy release rate derived from an elastic analysis starts to deviate from the value obtained from an elastic-plastic calculation. The elastic result now starts to be nonconservative and at twice the design pressure the elastic analysis will clearly underestimate the severity of the crack. A 2-D elastic-plastic plane strain approximation will on the other hand grossly overestimate the severity of the crack. A realistic 3-D elastic-plastic analysis is, therefore, needed to estimate the safety factors of surface flaws and to serve as benchmarks for the development of simpler design calculations.
Elastic-Plastic Line-Spring Finite Elements for Surface-Cracked Plates and Shells
Authors: Parks D. M. , White C. S.
Published: November 2009

The elastic line-spring finite element of Parks, et al. [1], which was incorporated into the ABAQUS© finite element program, is extended to include elastic-plastic response for approximate evaluation of the J-integral in surface-cracked plates or shells. J-analysis of a long axial crack in a pressurized cylinder is performed both with the virtual crack extension method and with a single elastic-plastic line-spring element attached to a 180-deg ring of shell elements constrained to (axial) plane strain. Agreement of the two models is generally good, both in the elastic range (as was noted earlier by Buchalet and Bamford) and in the plastic range. An axially cracked, internally pressurized cylinder containing a semi-elliptical flaw of aspect ratio a/c = 1/3, and of varying maximum relative depths a/t has also been analyzed.
Analysis of Surface Flaw in Pressure Vessels by a New 3-Dimensional Alternating Method
Authors: Nishioka T. , Atluri S. N.
Published: November 2009

An alternating method, in conjunction with the finite element method and a newly developed analytical solution for an elliptical crack in an infinite solid, is used to determine stress intensity factors for semi-elliptical surface flaws in cylindrical pressure vessels. The present finite element alternating method leads to a very inexpensive procedure for routine evaluation of accurate stress intensity factors for flawed pressure vessels. The problems considered in the present paper are: (i) an outer semi-elliptical surface crack in a thick cylinder, and (ii) inner semi-elliptical surface cracks in a thin cylinder which were recommended for analysis by the ASME Boiler and Pressure Vessel Code (Section III, App. G, 1977). For each crack geometry of an inner surface crack, seven independent loadings, such as internal pressure loading on the cylinder surface and polynomial pressure loadings from constant to fifth order on the crack surface, are considered. From the analyses of these loadings, the magnification factors for the internal pressure loading and the polynomial influence functions for the polynomial crack surface loadings are determined. By the method of superposition, the magnification factors for internally pressurized cylinders are rederived by using the polynomial influence functions to check the internal consistency of the present analysis. These values agree excellently with the magnification factors obtained directly. The present results are also compared with the results available in literature.
A Study of Shear Crack Propagation in Gas-Pressurized Pipelines
Authors: Sugie E. , Matsuoka M. , Akiyama T. , Mimura H. , Kawaguchi Y.
Published: November 2009

Full-scale burst tests were carried out five times on line pipes of 48 in. o.d. × 0.720 in. w.t., Grad. X-70 manufactured by the controlled rolling and the quenching and tempering processes. It was found that the critical notch ductility for arresting a shear crack depends on the pipe length within which the crack is to be arrested. This result is well explained by solving the equation which governs change of crack velocity. The behavior of shear crack propagation and arrest can be well analyzed regardless of the existence or nonexistence of separation by Charpy energy.
Background for Changes in the 1981 Edition of the ASME Nuclear Power Plant Components Code for Controlling Primary Loads in Piping Systems
Authors: Moore S. E. , Rodabaugh E. C.
Published: November 2009

Section III of the ASME Boiler and Pressure Vessel Code contains simplified design formulas for placing bounds on the plastic deformations in nuclear power plant piping systems. For Class 1 piping a simple equation is given in terms of primary load stress indices (B1 and B2) and nominal pressure and bending stresses. The B1 and B2 stress indices reflect the capacities of various piping products to carry load without gross plastic deformation. In this paper, the significance of the indices, nominal stresses, and limits given in the Code for Class 1 piping and corresponding requirements for Class 2 and Class 3 piping are discussed. Motivation behind recent (1978–1981) changes in the indices and in the associated stress limits is presented.
Design Parameters Affecting Bolt Load in Ring-Type Gasketed Joints
Authors: Singh K. P. , Soler A. I.
Published: November 2009

A simplified formula for predicting the change in bolt load from preload to operating condition in a ring-type bolted flange connection is presented. The results clearly demonstrate the important dimensionless parameters that affect the magnitude and direction of the bolt load change.
The Southwell Method for Predicting Plastic Buckling Loads for Elbows
Authors: Sobel L. H.
Published: November 2009

The Southwell method for the prediction of buckling loads is applied to results obtained from tests of two 16-in-dia Type 304 stainless steel elbows loaded by an in-plane closing bending moment M. The basis of the method is discussed, and it is shown that proper application of the method requires that the nonlinear component of the deformation, δnl, be used in the Southwell plot. Predicted buckling loads determined from four experimental M-δnl curves for each test are found to be consistent and accurate, with an average value that is only slightly above the experimental plastic buckling load. The major conclusion of this paper is that the Southwell method based on δnl is valid for elbows loaded by an in-plane closing bending moment, and for a certain broader class of elastic or plastic nonlinear buckling (geometric collapse) problems for imperfection-insensitive structures. Consequently, tests and analyses of such structures need not be carried out to buckling to determine buckling loads. Practical advantages of such nonbuckling tests and analyses are discussed.
Thermoviscoplastic Analysis of First Walls Subjected to Fusion Power Transients
Authors: Schreyer H. L. , Kennedy J. M. , Schoeberle D. F.
Published: November 2009

Abrupt thermal fluxes on the first walls of fusion reactors represent a loading environment that requires advanced analytical capabilities. Solutions are needed to a wide range of postulated conditions to provide guidance for safety features and design modifications. A brief outline is given of a computer code that provides an integrated procedure for handling thermal stresses and large deformations under dynamic conditions. The code includes a new thermoviscoplastic constitutive equation that incorporates thermal softening, failure and strain rate. Solutions to several verification and illustrative problems are given.
Damage and Failure at Elevated Temperature
Authors: Manjoine M. J.
Published: November 2009

Damage of a material is a process by which the strength and ductility are degraded. Failure of a component is the inability to perform a function within the design specifications and imposed limits. An index of failure is defined as a limit on a specific type of damage. This paper describes the flow and fracture characteristics of metals in a high temperature environment and relates these characteristics to the accumulation of damage.
The PVRC International Benchmark Project on Simplified Methods for Elevated Temperature Design and Analysis—An Update
Authors: Pai D. H.
Published: November 2009

The Pressure Vessel Research Committee (PVRC) Subcommittee on Elevated Temperature Design has been actively engaged in an International Benchmark on Simplified Methods for Elevated Temperature Design. At the Third International Seminar on Inelastic Analysis and Life Prediction in High Temperature Environment held in conjunction with the 6th International Conference on Structural Mechanics in Reactor Technology (SMiRT), August 1981, a progress report on the International Benchmark Project was first reported. This paper is an update of the results of that project. A brief description of the PVRC activities on Elevated Temperature Design is first given. The International Benchmark Problems I, II, and III will then be described. The comparisons between analyses and the recently released experimental results of the French Commissariat l’ Energie Atomique test on fluctuating sodium level in a pool reactor model is now included in this paper. Potential benchmark problems for future consideration by the Subcommittee are also mentioned.
Creep of Intersecting Equal Diameter Cylindrical Shells Under Internal Pressure
Authors: Updike D. P. , Kalnins A.
Published: November 2009

The creep behavior in the crotch region of two normally intersecting cylindrical shells of equal diameter and thickness is treated with the aid of an axisymmetric shell model. The edge and pressure loads on this model, which has already proved to be useful in the case of elastic and elastic-plastic analysis, are chosen to simulate the loading in the crotch region. The model is used to calculate the redistribution of stress from the elastic state to the stationary state. By taking into account the wall thinning, which occurs as creep takes place, the critical elapsed time to rupture of a ductile vessel is estimated.
An Analysis of Dynamic Crack Propagation and Arrest in a Nuclear Pressure Vessel Under Thermal Shock Conditions
Authors: Jung J. , Kanninen M. F.
Published: November 2009

The inner wall of a nuclear pressure vessel can become embrittled during service due to irradiation effects. As a result, a small flaw could become critical during the thermal shock that would accompany a loss-of-coolant-accident. To assess the consequences of this possibility, elastodynamic computations were performed on the subsequent rapid unstable crack run-arrest events. One difficulty is the lack of reliable dynamic fracture toughness data as a function of crack speed and temperature. However, using plausible estimates, computational results were obtained for comparison with conventional quasi-static analyses. These indicate that the neglect of the dynamic effects is mildly anticonservative for this application.
Stress Intensity Factors for Radial Cracks in a Pre-Stressed, Thick-Walled Cylinder of Strain-Hardening Materials
Authors: Pu S. L. , Chen P. C. T.
Published: November 2009

A simple method which combines the weight function technique and finite element results is used to obtain mode I stress intensity factor solutions for radially cracked cylinders subjected to a high internal pressure. The method is especially effective for cylinders having residual stresses due to a manufacturing pre-stress process to increase the maximum pressure the cylinder can contain and to improve the cylinder’s useful life against fatigue and fracture. The method is quite general for various assumptions involving the plastic stress-strain relations, the yield condition, the strain-hardening, and the compressibility of the cylinder material.
Elasto-Plastic Stress Analysis of the Standard Compact Specimen
Authors: Terada H.
Published: November 2009

Two-dimensional stress analysis for the standard compact specimen under plane stress and plane strain conditions were carried out by using the boundary collocation method. The Dugdale model concept was employed for elasto-plastic analysis. Plastic zone size and crack opening displacements at the typical locations, such as edge of plate, load line, and crack tip, were calculated for the practical range of applied load, and crack length-to-width ratio in the fracture toughness tests. In the process of elasto-plastic analysis, crack opening displacements and stress intensity factors corresponding to the elastic solution of the compact specimen were obtained. These results were shown to reasonably agree with those derived by Srawley and Gross, and by Newman.
On the Plastic and Viscoplastic Constitutive Equations—Part II: Application of Internal Variable Concepts to the 316 Stainless Steel
Authors: Chaboche J. L. , Rousselier G.
Published: November 2009

The constitutive equations developed in Part I with a combination of isotropic and nonlinear kinematic hardening rules can describe the usual monotonic and cyclic behavior of metals and alloys. Some materials, especially type 316 stainless steels, show interaction of many complex phenomena such as viscoplasticity, cyclic hardening, time softening and aging effects. . . On the basis of experimental results obtained in Electricite de France or taken from the literature the descriptive ability of the developed constitutive equations is discussed and a new methodology is proposed which treats instantaneous plasticity and creep by using a viscoplastic strain component alone.
Estimation of Creep Deformation in Components From Short-Term Proof Test Data
Authors: Marriott D. L.
Published: November 2009

The paper describes a technique for estimating creep deformation from the results of short-term proof tests. The method relies on the concept of a reference stress which is representative of the general stress level in the component. It is shown that the method provides an upper, and therefore safe, bound on creep deformation. Application to a complex piping component is used to illustrate the procedure and some of the practical problems of interpreting the experimental data. Finally, an attempt is made to relate the reference stress method to tentative design procedures in Code Case N.47 of the ASME III Code.
Lower-Bound Assessment of Creep Buckling Strength
Authors: Marriot D. L.
Published: November 2009

A method is developed for predicting the creep buckling behavior of complex pressurized components from the results of ambient, short-term buckling tests on geometrically similar components. The method has been tested against experimental data on boss-loaded spherical shells and shows reasonable accuracy of prediction of the buckling load after a given period of time. Application to the design analysis of a component for a boiler is described. An analysis of the approximations made in developing the method is included. It is shown that a lower bound on buckling strength at a given time is obtained.
Computational Method for the Analysis of Valve Transients
Authors: Siikonen T.
Published: November 2009

A computational method for valve dynamics is discussed. The method consists of a hydraulic part and the equations describing valve dynamics. These are coupled together using a boundary condition in the hydraulic model. Some important parameters for the boundary condition are determined experimentally. The hydraulic equations are solved using the method of characteristics. Some example calculations for a boiling water reactor are presented.
A Finite Element Analysis of Collapse of Perforated Casing
Authors: Smith M. B. , Pattillo P. D.
Published: November 2009

The purpose of this paper is to report the results of finite element analyses of the collapse of perforated casing. In the study, both inline (0-deg phasing) and staggered (90-deg phasing) patterns are considered. The primary intent of the study is to illustrate the severe loss of casing cross-sectional integrity accompanying extrusion of a ductile formation into the wellbore. It is shown that, for reasonable perforation densities, the primary effect of the perforation pattern is not strength reduction of the cross section, but definition of a nonuniform loading pattern resulting from formation production. In this regard, in the presence of large-scale formation failure in the near wellbore region, it is crucial to the integrity of the casing that a solids control technique be employed.
Life Prediction at Elevated Temperature
Authors: Tomkins B.
Published: November 2009

This short paper reviews some of the work in the United Kingdom concerned with the problem of life prediction at elevated temperature. It includes detailed examination of creep-fatigue failure, thermal shock failure and the development of cracks at elevated temperature.
Experimental Verification of Constitutive Equations for Creep and Plasticity Based on Overlay Models
Authors: Meijers P. , Roode F.
Published: November 2009

A general description of creep and plastic deformation based on overlay models is presented. This includes the description of time effects during plastic deformation at room temperature. A detailed procedure to obtain the model parameters is also discussed. The description has been evaluated for a large number of uniaxial and biaxial load histories on thin walled tubes. The materials involved are a 2 1/4 Cr-1 Mo steel stabilized with Niobium (WN 1.6770) and a 304 stainless steel (WN 1.4948). The theoretical predictions of the plastic deformations are found to be sufficiently accurate. The evaluation of the phenomenological description for creep shows a fairly good agreement with the real creep deformation process. Special attention requires the description of softening due to microstructural changes.
J-Integral Estimation Procedures
Authors: Derbalian G.
Published: November 2009

This paper presents efficient procedures for estimating the J-integral, a parameter for characterizing stable crack growth under inelastic conditions. Two different formulations are shown. The basis of the first approximate J-integral formula is the familiar extension of the elastic strain energy release rate computation for elastic-plastic loads. This extension is particularly suited for contained plasticity. With continued yielding, when the global load-deflection curve exhibits nonlinear behavior (i.e., net section yielding commences), this first J-approximation formula deviates from the actual J-integral. A second approximate formula derived here can be used at this point which is based on the definition that J-integral can be interpreted as the potential energy difference between two identically loaded specimens having crack sizes that differ infinitesimally. This latter formula is exact for linear loading and rigid-plastic material response, and is shown to predict J accurately in the elastic-plastic range of loading. Several standard cracked geometries for which documented J-integral solutions exist were applied to test the estimation procedures. This technique is very general and can be applied to virtually any structure or continuum. And no special assumption of material hardening, such as Ramberg Osgood, is necessary. These estimation techniques are significantly easier and more economical to use than a conventional finite element procedure, which models details of a cracked geometry.
Parametric Representation of the Yield Strength-Strain Rate Behavior of A533B Steel
Authors: Hoff R. , Johnson G. E. , Rubin C. A. , Hahn G. T.
Published: November 2009

A nonlinear programming technique to estimate the parameters for a temperature normalized version of the Malvern equation is presented. The general conjugate gradient algorithm is used to minimize a least-squares function formulated from data for A533B steel. A constrained solution (which provides preferential treatment for a particular data point) is also given. The results satisfactorily represent experimental data over a temperature range from −73C to 260C. The approach is well suited to design applications where data at a specific temperature of interest are limited or nonexistent.
Maximum Stresses and Flexibility Factors of Smooth Pipe Bends With Tangent Pipe Terminations Under In-Plane Bending
Authors: Thomson G. , Spence J.
Published: November 2009

A theoretical solution is presented for the in-plane bending, linear elastic behavior of smooth, circular cross-sectional constant thickness pipe bends with connected tangent pipes of similar section. The analytical method employs the theorem of minimum total potential energy with suitable kinematically admissible displacements. Integration and minimization is performed numerically. Results are given for bend flexibilities and peak stresses covering a wide range of practical geometries. These are compared with other theoretical predictions and finite element results as well as with some recent experimental data.
Hydraulically Expanded Tube-to-Tubesheet Joints
Authors: Scott D. A. , Wolgemuth G. A. , Aikin J. A.
Published: November 2009

To avoid stress corrosion cracking, a method of producing tube-to-tubesheet joints with low residual stresses was sought. Hydraulic expansion was found to be an acceptable method. In this paper, the experimental and theoretical work done to determine these stresses is presented. The area of interest is the transition region between the expanded and unexpanded sections of tubing. X-ray diffraction, stress corrosion cracking test and strain gaging were the prime measuring techniques used. Extensive use of finite element analysis was also made. In addition, the pull strength, length change, etc., of this type of joint were investigated.
Study on the Fluidelastic Vibration of Tube Arrays Using Modal Analysis Technique
Authors: Ohta K. , Kagawa K. , Tanaka H. , Takahara S.
Published: November 2009

This paper presents a method to calculate the critical flow velocity of fluidelastic vibration of tube arrays in heat exchangers. The method is based upon the modal analysis technique, which combines the fluid dynamic force caused by cross flow and the vibration characteristics of the complicated tube array to obtain its response. The analytical method enables us not only to take into account the vibration mode of tube array and nonuniformity of velocity and density distribution of cross flow, but also to estimate the effect of antivibration devices, such as spacer, connecting band, and so on. Numerical examples of constrained single-tube array, multi-tube array in reversed flow, and group of panels with spacers are described.
A Comparative Study of Combination Methods Used in Response Spectrum Analysis of Nuclear Piping Systems
Authors: Gupta S. , Jhaveri D. P. , Kustu O. , Blume J. A.
Published: November 2009

The different methods of combining responses for individual modes and directions for response spectrum analysis of nuclear piping systems are evaluated. For the purpose of the study, dynamic responses of 20 typical piping systems using nine different combination methods are systematically compared. The study established the relative conservatism in design achieved by each method and the probability that a particular combination method will produce a more conservative estimate of seismic response than obtained using one of the methods accepted by the U.S. Nuclear Regulatory Commission.
Elastic-Plastic Collapse of Axially Compressed Cylindrical Shells: A Brief Survey With Particular-Application to Ring-Stiffened Cylindrical Shells With Reinforced Openings (Survey Paper)
Authors: Bushnell D. , Meller E.
Published: November 2009

A brief survey of plastic buckling of axially compressed cylindrical shells is given. Results of nonlinear finite element analyses of several axially compressed, ring-stiffened, steel, cylindrical shells are presented, including comparisons with tests conducted at Chicago Bridge and Iron Co. and at the Los Alamos National Laboratory (LANL). Some of the LANL specimens with radius-to-thickness ratio of about 450 have reinforced circular openings that cut across various numbers of ring stiffeners. These cylindrical shells are loaded by enforced axial displacement applied to thick aluminum end plates halfway between the axis of revolution and the shell wall. Measured imperfections are included in the analysis of one ring-stiffened specimen without any cutout. Inclusion of the imperfection field reduces the predicted collapse load by only eight percent. Reinforced openings that cut one or two or three rings reduce the collapse load by 14, 21 and 22 percent, respectively. Agreement between test and theory for the nonuniformly compressed LANL specimens is within 14 percent, even with initial imperfections neglected in the analysis.
Stress Analysis of Mitred Bends by Ring Elements
Authors: Watanabe O. , Ohtsubo H.
Published: November 2009

This paper proposes a ring element for the stress analysis of mitred bends, which is an extension of ring elements for pipe bends proposed by the present authors. Since accurate treatments of continuity conditions on the connecting lines between straight pipe segments are employed and strain-displacement relations derived from the general thin shell theory with shear strains are considered, the present method can be applied to problems of mitred bends of complex configurations under general loading conditions. Shape functions are developed by trigonometric functions and Hermitian polynomials of second order in the circumferential and longitudinal directions, respectively. This finite element method requires fewer number of degrees of freedom for the same accuracy than the conventional shell elements.
The Effect of Infrequent Thermal Overloads on the Behavior of Plates Subjected to Cyclic Thermal Loading
Authors: Phillips J.
Published: November 2009

Many components in high-temperature plant experience steady mechanical loads combined with cyclic thermal loads due to routine shutdowns. Less frequent but more severe thermal loads due to unplanned shutdowns may interrupt this routine loading pattern. This paper presents the results of computer calculations on the effect of such thermal overloads on the behavior of a “Bree plate.” Particular attention is given to the creep and plastic ratchetting deformation properties of the system. It is shown that the plate material properties are an important factor in the problem. With an elastic-perfectly plastic plate material, behavior can be predicted from an appropriate linear combination of the results for each type of thermal cycle, multiplied by an enhancement factor in certain cases. With a bilinear kinematic hardening, material behavior is generally determined by the properties of the overload thermal cycle. These results are relevant to many high-temperature design problems.
Progress in Gasket Testing—Milestone Results
Authors: Bazergui A. , Payne J. R.
Published: November 2009

An extensive gasket test program, carried out under the auspices of the Pressure Vessel Research Committee and supported by over 30 sponsors from 6 countries, is nearing completion. The program was developed as part of the Long-Range Flanged-Joint Improvement Program of the PVRC at the request of the American Society of Mechanical Engineers and in response to the need for resolving complex gasket behavior questions. The test program was formulated in cooperation with cognizant ASME, API and ASTM Standards Committees. In these tests, complex load/pressure sequences are used to determine leakage performance and deformation response at room temperature of four types of commonly used gaskets. This paper presents an overview of the test program which investigates the effect of fluid pressure, type of fluid, flange facing surface finish, maximum gasket stress, gasket deformation and stress cycling. The results of the first two series of tests on spiral-wound asbestos-filled gaskets are presented to highlight some of the trends observed. Interpretation of the results is carried out with the aim of deriving meaningful design factors similar to the m and y factors of the ASME Pressure Vessel Code. It is shown, however, that such factors cannot have a unique value for a given gasket type. Instead, m and y are interrelated and their value depends on the level of specified tightness. They are also influenced by the various parameters aforementioned.
On Design Procedures for the Buckling of Cylinders Under Combined Axial Compression and External Pressure
Authors: Galletly G. D. , Pemsing K.
Published: November 2009

The test results on biaxially compressed metallic cylinders published before 1983, together with some early ones from a test program underway at Liverpool University, were plotted in terms of the stress ratios Sp(=p/pk) and Sx(=σθ/σK,θ). These results were then compared with the predictions of the linear interaction equation Sp + Sx = 1 and two nonlinear ones. The minimum predicted buckling quantities pk and σk,x were evaluated using the recommendations of ASME III N-284, DASt, DnV and ECCS. Based on this study, some possible design procedures for this interactive buckling problem are suggested.
The Technical Basis of the External Pressure Section of BS5500
Authors: Kendrick S.
Published: November 2009

The technical basis of the external pressure section of the British Pressure Vessel Code BS5500 is presented. Interstiffener collapse of cylinders, overall collapse, sideways tripping of stiffeners and dome collapse are all considered. Some comparisons are given with the equivalent American Code ASME Section VIII.
Simple Calculations for the Stability of Soft, Thin-Walled Mandrels During Filament Winding
Authors: Salamon N. J.
Published: November 2009

During filament winding of a laminated pressure vessel over a flexible, thin-walled mandrel, the winding tension produces an external pressure on the mandrel which tends to buckle it. A simple analysis which adequately describes the physical behavior of the vessel is given in a very convenient form. Using the analysis method, various internal pressurization schemes are discussed which not only prevent buckling, but also permit control over dimensional changes and relaxation or overtension in the fibers. The theory is illustrated by an example.
Bending and Twisting of Pipes With Strain Hardening
Authors: Lau J. H. , Lau T. T.
Published: November 2009

A closed-form solution is presented for the small deformation analysis of a straight thin-walled circular cylinder subjected to the simultaneous action of bending and twisting moments. Dimensionless interaction curves and charts which relate the variables, bending moment, curvature, maximum effective strain, twisting moment, and shear strain are also provided for engineering practice convenience. The average stress-strain diagram of the cylinder is described by two straight lines. The result presented herein is not only a good approximation of a wide class of piping materials, but also provides a standard tool for estimating the accuracy of different direct schemes such as numerical integration, finite-difference, and finite-element methods.
Simplified Pipe Whip Dynamics
Authors: Haydl H. M.
Published: November 2009

The pipe whip problem is examined by means of elementary dynamics theory. It is shown that available methods can readily be modified and applied in a first estimate of the pipe whip problem.
Structural Evaluation of a Butt-Welded Elbow End: A Simplified Procedure
Authors: Dhalla A. K.
Published: November 2009

Explicit piping design procedures are not provided in theASME Code for structural evaluation of ovalization and fabrication effects at the butt-welded end of an elbow. This paper presents a conservative semi-analytical procedure that can be used with elastic as well as inelastic analysis to evaluate an elbow cross section welded to a straight pipe. The concept of carry-over factors is used to obtained ovalization stresses or strains at the elbow end. The stresses introduced by material and geometric nonuniformities in the fabrication process are then added to the ovalization stresses to complete structural evaluation of the girth butt-welded elbow joint.
Stiffening Effects of Tubes in Heat Exchanger Tubesheet
Authors: Terakawa T. , Imai A. , Yagi K. , Fukada Y. , Okada K.
Published: November 2009

Strain-measuring tests were performed with strain gages on rectangular coupons taken from perforated plate with triangular pitch under both uniaxial tensile loads and pure bending loads. The effective Young’s modulus obtained from the tests have strong correlation with the values recommended by the ASME Code. Next, to evaluate the stiffening effects of tubes, similar strain-gage tests were performed for different types of perforated coupons. One type had the tubes strength welded into the penetration holes of the test coupons. Another type had the tubes both expanded and strength welded into the test coupons. Stiffening effects of tubes are clearly obtained from these tests. Judging from the effective Young’s modulus of triangular pitch obtained by the testing, the recommended minimum credit given to the tube wall is 50 percent under elastic load condition. In addition, for experimental tests on an actual large-sized shell-and-tube heat exchanger under hydraulic test condition, good correlation was obtained between calculated and measured stress when full credit was taken for the tube wall in the calculation.
Isentropic Expansion of Dry Saturated Vapor—Application to the Design of Safety Valves
Authors: Copigneaux P. , Tobaly P. , Godin M.
Published: November 2009

Accepted standards relative to the design of safety valves are based on calculations of the maximum (flow rate) during isentropic expansion through a converging nozzle. The theoretical value is then corrected with an empirical coefficient Kd for a better approach of reality. In this paper, after reviewing the calculation which is the basis for the various existing standards, we indicate the limits of their applications and present a more rigorous method in the case of saturated vapors as well as the first results of systematic computer calculations.
Efficient Computational Procedures for Long-Time Duration Fluid-Structure Interaction Problems
Authors: Liu W. K. , Chang H. G.
Published: November 2009

In this paper, two different classes of transient algorithms, implicit-explicit and implicit-implicit, are developed for the response calculations of long-time duration fluid structure interaction problems which arise during a seismic event. To avoid the stringent time step, the generalized structural and fluid displacements are integrated implicitly. If the fluid wave effect is important (e.g., dam-reservoirs and fluid-pipe systems), the second-order accuracy explicit Rational Runge-Kutta (RRK) operator is employed to integrate the fluid pressure. If the fluid is incompressible or the fluid inertia is much greater than that due to the structure (e.g., fluid-tank systems and nuclear reactor systems), the implicit generalized trapezoidal family of methods are employed to integrate the fluid pressure. With the implicit-explicit partition, the advantage of employing larger time step is achieved; whereas with the implicit-implicit partition, unconditional stability is sought. The resulting coupled matrix equations are “symmetric” and “profiled,” and there is only one structural response calculation per time step. The accuracy and stability of these two algorithms are studied via an elastic piston wave interaction problem. The economical advantages in both computations and computer storage are examined on the problem of a fluid-pipe system.
Implication of Elastic Stress Range at Structural Discontinuity
Authors: Karabin M. E. , Dhalla A. K.
Published: November 2009

This paper illustrates that in addition to the elastic stress intensity range it is necessary to evaluate the stress intensities (and corresponding material properties) at specific times during a postulated thermal transient to characterize inelastic response at a structural discontinuity. The specific case of an austenitic flued head operating in a temperature range of 600 to 1050°F (316 to 538°C) is used to calculate ratcheting strain accumulation due to cyclic primary and secondary loads. Detailed inelastic analyses were performed to evaluate two designs. Both designs have essentially the same stress intensity range; however, only the design with lower stress intensity during steady-state elevated temperature operation satisfied the ASME Code Case N-47 strain accumulation limits.
In-Plane Bending Behavior of Pipe Bends With End Constraints Under Steady-State Creep
Authors: Chan K. L. C. , Boyle J. T. , Spence J.
Published: November 2009

This paper presents an analysis for the in-plane bending behavior of smooth thin pipe bends connected to tangent pipes or rigid flanges under steady-state creep conditions. Creep flexibility factors obtained from this analysis are presented and compared with earlier results from existing theories with no end constraints. Applications to design are briefly discussed.
A Reassessment of PWR Pressure Vessel Integrity During Overcooling Accidents, Considering 3-D Flaws
Authors: Cheverton R. D. , Ball D. G.
Published: November 2009

A continuing analysis of the pressurized-thermal-shock problem associated with PWR postulated overcooling accidents indicates that the previously accepted degree of conservatism in the fracture-mechanics model needs to be more closely evaluated, and, if excessive, reduced. One feature that was believed to be conservative was the use of two-dimensional as opposed to finite-length (three-dimensional) flaws. The degree of conservatism could not be adequately investigated because of computational limitations and a lack of knowledge regarding flaw behavior; however, that situation has changed to the extent that some cases involving finite-length flaws can be studied. A flaw of particular interest is one that is located in an axial weld of a plate-type vessel. For those vessels that suffer relatively high-radiation damage in the welds, the length of the flaw will be no greater than the length of the weld, and recent calculations indicate that a deep flaw of that length (∼2 m) is not effectively infinitely long, contrary to previous thinking. The benefit to be derived from consideration of the 2-m flaw and also a semi-elliptical flaw with length-to-depth ratio of 6/1 was investigated by analyzing several postulated transients. In doing so the sensitivity of the benefit to a specified maximum crack-arrest toughness and to the duration of the transient was investigated. Results of the analysis indicate that for some conditions the benefit in using the 2-m flaw is substantial, but it decreases with increasing pressure, and above a certain pressure there may be no benefit, depending on the duration of the transient and the limit on crack-arrest toughness.
The Influence of Residual Stresses on Small Through-Clad Cracks in Pressure Vessels
Authors: deLorenzi H. G. , Schumacher B. I.
Published: November 2009

The influence of cladding residual stresses on the crack driving force for shallow cracks in the wall of a nuclear pressure vessel is investigated. Thermo-elastic-plastic analyses were carried out on long axial through-clad and sub-clad flaws on the inside of the vessel. The depth of the flaws were one and three times the cladding thickness, respectively. An analysis of a semielliptical axial through-clad flaw was also performed. It was assumed that the residual stresses arise due to the difference in the thermal expansion between the cladding and the base material during the cool down from stress relieving temperature to room temperature and due to the subsequent proof test before the vessel is put into service. The variation of the crack tip opening displacement during these loadings and during a subsequent thermal shock on the inside wall is described. The analyses for the long axial flaws suggest that the crack driving force is smaller for this type of flaw if the residual stresses in the cladding are taken into account than if one assumes that the cladding has no residual stresses. However, the analysis of the semielliptical flaw shows significantly different results. Here the crack driving force is higher than when the residual stresses are not taken into account and is maximum in the cladding at or near the clad/base material interface. This suggests that the crack would propagate along the clad/base material interface before it would penetrate deeper into the wall. The elastic-plastic behavior found in the analyses show that the cladding and the residual stresses in the cladding should be taken into acocunt when evaluating the severity of shallow surface cracks on the inside of a nuclear pressure vessel.
Bend and Adjacent Span Reduction Factors
Authors: Lee M. Z.
Published: November 2009

A semi-analytical and computer experimental procedure is described for developing the bend and adjacent span reduction factors for an alternate method of seismic restraint spacing, based on stress and frequency invariance considerations. The results, in terms of fundamental frequency, deflection, stress and support loads are shown to be in good agreement with, or more conservative than, those obtained from formal analysis of a quasi-system with bend using a piping structural analysis computer program. A simple curve is presented relating the bend and the adjacent span reduction factors obtained from the method.
Extensions of the Failure Assessment Diagram Approach Semi-Elliptical Flaw in Pressurized Cylinder
Authors: Bloom J. M.
Published: November 2009

A simple, viable engineering method for assessing the integrity of nuclear pressure vessels has been developed at Babcock & Wilcox. The method uses results given in a plastic fracture handbook developed by General Electric and which are in the format of the Central Electricity Generation Board of the United Kingdom R-6 failure assessment diagram. The method is currently limited to two-dimensional/axisymmetric structural models with continuous flaws. Failure assessment of nuclear pressure vessels with assumed continuous flaws result in the calculation of overly conservative safety margins. This paper presents the extension of the existing failure assessment approach to include semi-elliptical flaw models, as well as example problems which demonstrate increased safety margins over the continuous flaw assumptions. In particular, failure assessment diagram curves and the corresponding failure assessment point expressions for an axially cracked pressurized cylinder with an ASME Section III, Appendix G semi-elliptical flaw are presented. The results of the example problems considering the less conservative semi-elliptical flaw model versus the continuous flaw model dramatically illustrate increased safety margins of 50 percent when more realistic semi-elliptical flaws are postulated. The results given in this paper are particularly valuable in the safety assessment of PWR vessels which have low toughness welds in their beltline regions.
Effect of Internal Pressure on Flexibility Factors in Pipe Elbows With End Constraints
Authors: Natarajan R. , Mirza S.
Published: November 2009

Finite element method has been used in the present work to study the stress distribution in an elbow with end constraints subjected to in-plane moment and pressure. Elbows of short radius (R/r) with varying pipe factors and bend angles have been considered. Present numerical results show for all elbow angles that follower pipe factors (thin pipes) the internal pressure reduces the flexibility factor by a larger amount than for elbows having larger pipe factors. These results are in line with the conclusions published earlier.