bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of Tubes in Fluid With Tube-Baffle Interaction
Authors: Chen S. S. , Jendrzejczyk J. A. , Wambsganss M. W.
Published: November 2009

Three series of tests are performed to evaluate the effects of tube to tube-support-plate (TSP) clearance on tube dynamic characteristics and instability phenomena for tube arrays in crossflow. Test results show that, for relatively large clearances, tubes may possess “TSP-inactive modes” in which the tubes rattle inside some of the tube-support-plate holes, and that the natural frequencies of TSP-inactive modes are lower than those of “TSP-active modes,” in which the support plates provide “knife-edge”-type support. Tube response characteristics associated with TSP-inactive modes are sensitive to tube-to-TSP clearance, TSP thickness, excitation amplitude, tube alignment, and the fluid inside the clearance. In addition, tube response is intrinsically nonlinear, with the dominance of TSP-inactive or TSP-active modes depending on the magnitudes of different system parameters. In general, such a system is difficult to model; only a full-scale test can provide all the necessary characteristics. A tube array supported by TSPs with relatively large clearances may be subjected to dynamic instability in some of the TSP-inactive modes; tube response characteristics and impact forces on TSPs for a tube row are studied in detail. Tube displacements associated with the instability of a TSP-inactive mode are small; however, impacts of the tube against TSPs may result in significant damage in a relatively short time.
An Automatic Procedure for the Generation of Accelerograms Enveloping Several Design Response Spectra
Authors: Preumont A.
Published: November 2009

During various steps in the design of a nuclear power plant, it is a common practice to generate accelerograms matching a design spectrum for one particular value of the damping ratio. Such accelerograms, however, may be found unconservative for other values of the damping ratio. The present note describes a simple iterative procedure for generating accelerograms which envelop several design response spectra.
A Finite Element Model for General Thick-Walled Shell Structures
Authors: Khaskia A. M. , Soler A. I.
Published: November 2009

A finite element for general thick-walled structures is presented. The general theory leading to this element is reviewed. A superparametric formulation is adapted. Legendre series expansions of all field variables through the structure thickness are key features in this formulation. “The General Higher Order Theory”—GENHOT element, as we call our element, presented here is capable of predicting the nonlinear distribution, through the thickness, of all stresses and displacements. Test problems with known closed form solution are modeled in order to assess the GENHOT performance. Also, a true thick-walled shell is modeled in order to demonstrate the power and capabilities of this element against a 3-D finite element.
The Bending of an Orthotropic Membrane Wall Supported at Arbitrary Points
Authors: Kwee H. K.
Published: November 2009

For large industrial boilers and boilers for Conventional Power Plants extra supporting of the rear wall (designated as “membrane wall”) of the furnace is necessary. By supporting the wall at scattered supporting points, one obtains, besides reduction of the stress level, also improvement of the dynamic behavior of the wall. A solution method is developed in this paper for laterally loaded membrane walls supported at arbitrary points inside the edges. This solution is based on the analytical solution for orthotropic plates.
Seismic Damping Factors of Small Bore Piping as Influenced by Insulation and Support Elements
Authors: Severud L. K. , Anderson M. J. , Barta D. A.
Published: November 2009

Seismic damping tests of a prototypical Liquid Metal Fast Breeder Reactor (LMFBR) small bore piping system is described, and measured transient responses to pulse excitations are reported. The test specimen was representative of a typical LMFBR insulated small bore piping system, and it was supported from a rigid test frame by prototypic dead weight supports, mechanical snubbers, and pipe clamps. Various support configurations were tested to assess the response sensitivity to insulation and other nonlinear support characteristics. Damping factors increased significantly due to the insulation and use of mechanical snubbers. Factors much higher than the magnitudes currently allowed in design by the USNRC Regulatory Guide 1.61, were found. This verified the design values, and it also pointed out the possibility of undue conservatism and costly overdesign resulting from use of the present design values.
Fundamental Frequencies of U-Tubes in Tube Bundles
Authors: Moretti P. M.
Published: November 2009

The natural frequencies of U-tubes on multiple supports have been studied as a complement to the author’s previous work on the vibration of straight heat-exchanger tubes (reference [1]). A rapid estimation procedure for fundamental frequencies of tubes on symmetrical support spacings has been developed by expressing the frequency in the form f1≥12π•a1•1Ls2•EIμ where the square root contains the tube properties of Young’s modulus, cross-sectional second moment, and linear density; Ls is a characteristic length of support spacing; and a1 is a dimensionless number which is a strong function of the support geometry (as expressed by the ratio of bend radius to span lengths) and weak function of Poisson’s ratio and of tube axial moment of inertia. a1 has been plotted as a function of the ratio of the bend radius to the straight-span length, for usual values of Poisson’s ratio and small axial moment of inertia. The underlying assumptions for the use of such plots are examined and the theoretical basis for the statement of a lower bound is given, in order to show where the use of this method is applicable.
Predicting the Residual Life of Plant Equipment—Why Worry?
Authors: Jaske C. E.
Published: November 2009

Predicting the residual life of plant equipment that has been in service for 20 to 30 years or more is a major concern of many industries. This paper reviews the reasons for increased concern for residual-life assessment and the general procedures used in performing such assessments. Some examples and case histories illustrating procedures for assessing remaining service life are discussed. Areas where developments are needed to improve the technology for remaining-life estimation are pointed out. Then, some of the critical issues involved in residual-life assessment are identified. Finally, the future role of residual-life prediction is addressed.
Monitoring for Life Extension
Authors: Davidson M. J. , Jones T. J. , Rosard D. D. , Scheibel J. R.
Published: November 2009

Combustion Engineering is under contract to EPRI to develop, construct and implement into a utility boiler a prototype on-line Boiler Stress and Condition Analyzer. The objective of the program is to develop and to demonstrate the analyzer’s potential to optimize the life of critical boiler components. The analyzer has been designed to assist the operator to warn of damaging transients, to optimize boiler start-up/shutdown rates and to accumulate unit operation data for the calculation of component life expenditure. The analyzer has been installed on the 1000-MW oil-fired Consolidated Edison Ravenswood No. 30 unit. This paper will outline the overall program and highlight significant results to date.
Findings on Creep-Fatigue Damage in Pressure Parts of Long-Term Service-Exposed Thermal Power Plants
Authors: Masuyama F. , Setoguchi K. , Haneda H. , Nanjo F.
Published: November 2009

The increase of long-term service exposure to thermal power plants, the tendency toward intermediate and cyclic operation to meet the change in electric power demand and supply situation, and the requirement to develop higher-temperature and higher-pressure plants have led to increasing attention towards the reliability improvement. This paper presents findings from field experiences of cracking or failure and two types of damage analyses—(1) creep-fatigue damage analysis based on the life fraction rule and (2) metallurgical damage analysis—of boiler pressure parts that have been exposed to long-term elevated temperature service. The field experiences are (1) cracking or failure of thick-walled Type 316 stainless steel pressure parts in the main steam line of an ultra-supercritical thermal power plant and (2) dissimilar metal weld joints for boiler tubing. The creep-fatigue damage analysis of these pressure parts showed a reasonable correspondence with the field experience. According to the creep-fatigue damage analysis and the metallurgical damage analysis, most of damage was restrained creep mode phenomenon without deformation. The creep damage was composed of metallurgical damage and mechanical damage such as microvoids and structural defects. One method of simulating field experienced creep damage was proposed and performed. As a result, the process of creep voids being generated and growing into cracks without deformation was successfully observed. Also a review of the current status of nondestructive detecting methods of creep damage suggests that detecting the creep voids metallurgically is more practical at the present time than doing so analyzing the changes in physical properties of the material. It is also suggested that, in the metallurgical approach, detecting the creep voids and cracks by replica method and anlayzing precipitates for evaluation of material deterioration by precipitate extraction method will make it possible to successfully address the problem of plant equipment creep damage evaluation and life prediction.
Prediction of Creep Deformation and Failure for 1/2 Cr-1/2 Mo-1/4 V and 2-1/4 Cr-1 Mo Steels
Authors: Parker J. D.
Published: November 2009

This paper reviews the development of an equation for the prediction of long-term creep strain and creep life. Originally, this relationship was successfully applied to 1/2 Cr-1/2 Mo-1/4 V ferritic steel, and present data suggest similar success with the 2-1/4 Cr-1 Mo material. The implications of this extrapolation technique are discussed and the consequences for plant-life assessment are considered.
Changes in Microstructure and Mechanical Properties of Cr-Mo Reactor Vessel Steels During Long-Term Service
Authors: Nishizaka Y. , Hara Y. , Hori A. , Tsukahara H. , Miyano K. , Wada T. , Cox T. B.
Published: November 2009

Changes in microstructure and mechanical properties of 1Cr-0.5Mo and 2.25Cr-1Mo steels during long-term service have been investigated. The study includes inspection of a 1Cr-0.5Mo steel reactor vessel which operated for 20 yr and tests on specimens that had been exposed to service environments. The reactor vessel, exposed at 490 to 530°C for 170,000 hr (about 20yr), showed appreciable decrease in the room temperature yield strength, impact toughness and creep rupture strength compared with the original properties. The service exposure caused changes in carbide morphology and species, forming M2C and M7C3 carbides and transferring significant amounts of Cr and Mo from the matrix to carbides; only 32 percent of the total Mo and 72 percent of the total Cr remained in the matrix. The microstructure of 2.25Cr-1Mo steel showed higher stability than that of 1Cr-0.5Mo steel, although a similar transfer of Mo and Cr from the matrix to carbides took place. The Mo and Cr contents remaining in the 2.25Cr-1Mo steel matrix after a 2-yr exposure were only 25 and 74 percent, respectively, of the total quantities in the steel. The partitioning of Mo and Cr to carbides could increase the stability of carbides and consequently reduce the carbon content in the matrix. The mechanical properties are influenced by both the change in the composition of the matrix and the change in carbide morphology. The metallographic examination provides useful information, although qualitative at this stage, on the degree of deterioration of materials.
Flow-Induced Vibration: Guidelines for Design, Diagnosis, and Troubleshooting of Common Power Plant Components
Authors: Au-Yang M. K.
Published: November 2009

The different techniques of assessing the flow-induced vibration problems of common power plant components are reviewed. The components are divided into categories of single cylinders, flat plates, pipes containing flowing fluid, cylindrical shells, and tube banks. The mechanisms considered include turbulent buffeting, instability, vortex shedding, acoustics, and leakage flow-induced vibration. Emphasis is placed on applications to industrial problems.
Postbuckling Behavior of Axially Compressed Graphite-Epoxy Cylindrical Panels With Circular Holes
Authors: Knight N. F. , Starnes J. H.
Published: November 2009

The results of an experimental and analytical study of the effects of circular holes on the postbuckling behavior of graphite-epoxy cylindrical panels loaded in axial compression are presented. The STAGSC-1 general shell analysis computer code developed by Bo 0. Almroth and Frank A. Brogan is used to determine the buckling and postbuckling response of the panels. The loaded, curved ends of the specimens were clamped by fixtures and the unloaded, straight edges were simply supported by knife-edge restraints. The panels are loaded by uniform end shortening to several times the end shortening at buckling. The unstable equilibrium path of the postbuckling response is obtained analytically by using a method based on controlling an equilibrium-path-arc-length parameter instead of the traditional load parameter. The effects of hole diameter, panel radius, and panel thickness on postbuckling response are considered in the study. Experimental results are compared with the analytical results and the failure characteristics of the graphite-epoxy panels are described.
Studies of the Line-Spring Model for Nonlinear Crack Problems
Authors: Kumar V. , German M. D.
Published: November 2009

This paper presents an investigation of the line-spring model (LSM) of Rice and Levy as applied to nonlinear crack problems. A J2 deformation theory of plasticity formulation of a LSM for obtaining the fully plastic crack solutions is first described in the framework of a shell finite element method. Results are obtained for 2-D axial and circumferential cracks in cylinders and are compared against those developed by detailed finite element crack tip analyses. Discrepancies are found in the case of axially cracked cylinders under internal pressure. To overcome this problem a modified approach, termed the continuum-LSM, is presented, and its finite element implementation is described in some detail. It is shown that in contrast to the shell-LSM, the results obtained by the continuum-LSM for internally pressurized axially cracked cylinders are in close agreement with detailed finite element crack-tip calculations. Lastly, a discussion on the fully plastic analysis of surface cracks by the LSM is also given.
The Bauschinger and Hardening Effect on Residual Stresses in an Autofrettaged Thick-Walled Cylinder
Authors: Chen P. C. T.
Published: November 2009

Most of the earlier solutions for residual stresses were based on the assumption of elastic unloading and only a few considered reverse yielding. In this paper a new theoretical model for a high strength steel is proposed and a closed-form solution of residual stresses in autofrettaged tubes has been obtained. The new results indicate that the influence of the combined Bauschinger and hardening effect on the residual stress distribution is significant.
Material Behavior Under Thermal Loading
Authors: Sehitoglu Huseyin
Published: November 2009

Material behavior under thermo-mechanical and isothermal loading cases is studied. The influence of constraint on thermo-mechanical deformation behavior is identified using a two-bar structure. Some of the possible microstructural mechanisms that may be operative under thermo-mechanical loading conditions are discussed. Isothermal tests are reported in the temperature range 20 to 600°C. Additional isothermal tests with step increases and decreases in temperature are performed to study the influence of temperature history on material behavior. During these tests, transient material behavior indicated temperature-strain history effects. Constitutive equations that capture essential features of material behavior under isothermal and thermo-mechanical loading cases are examined. Preliminary predictions of cyclic stress-strain loops are compared to experimental response. Further work is needed to incorporate temperature-strain history effects into constitutive equations.
Strain Distributions in a Type 316/16-8-2 Stainless Steel Weldment During Cyclic Loading
Authors: Korth G. E. , Harper M. D.
Published: November 2009

Test specimens were cut from a 25-mm-thick Type 316 stainless steel plate butt welded with 16-8-2 filler wire. The specimens were oriented transverse to the weld seam and contained base metal, heat-affected zone (HAZ), and weld metal in the gage section. Strain-controlled cyclic loading at room temperature was imposed across the heterogeneous weldment while local strains at various points within the gage section were continuously monitored. Results show that strains at the local points can vary markedly from the average strain of the composite section. Strain concentrations occurred in the softer base metal which led to failure much sooner than the composite strain would indicate. However, when the maximum strain range from a local area was compared to baseline data, the life correlation was very good.
Probabilistic Assessment of Pressure Vessel and Piping Reliability (Survey Paper)
Authors: Sundararajan C.
Published: November 2009

The paper presents a critical review of the state-of-the-art in probabilistic assessment of pressure vessel and piping reliability. First the differences in assessing the reliability directly from historical failure data and indirectly by a probabilistic analysis of the failure phenomenon are discussed and the advantages and disadvantages are pointed out. The rest of the paper deals with the latter approach of reliability assessment. Methods of probabilistic reliability assessment are described and major projects where these methods are applied for pressure vessel and piping problems are discussed. An extensive list of references is provided at the end of the paper.
Analysis of Interaction Behavior of Surface Flaws in Pressure Vessels
Authors: O’Donoghue P. E. , Nishioka T. , Atluri S. N.
Published: November 2009

The evaluation of stress intensity factors for surface flaw problems and, in particular, semi-elliptical surface cracks in cylindrical pressure vessels has been well developed using the finite element alternating method. Some of the examples presented here include the interaction effects due to multiple internal longitudinal surface cracks in cylinders as recommended for analysis in the ASME Boiler and Pressure Vessel Code (Section XI). For each crack geometry, several loading cases are considered including internal pressure and polynomial pressure loadings from constant to fourth order. By the method of superposition, the magnification factors for internally pressurized cylinders are rederived using the polynomial influence functions. These influence functions give useful information for design purposes such as in the analysis of a thermally shocked cylinder. The problem of a single circumferential crack in a cylinder is also investigated using the finite element alternating method, and a number of results for such problems are also presented here.
Opening Mode Stress Intensity Factors for Embedded Rectangular and Irregular Planar Defects
Authors: Khattab M. A. A. , Burns D. J. , Pick R. J. , Thompson J. C.
Published: November 2009

An integral technique has been used to estimate opening mode stress intensity factors, K1, for embedded rectangular and irregular planar defects subjected to uniform tension. These estimates have been confirmed by stress freezing photoelastic techniques. Also K1 estimates for rectangular defects are shown to compare well with theoretical solutions obtained by others.
Elastic-Plastic Fracture Mechanics Methodology Using the Modified J, JM, Resistance Curve Approach
Authors: Ernst H. A. , Landes J. D.
Published: November 2009

The J-resistance curve approach is reviewed, and its use for instability predictions is explained in detail. A complete elastic-plastic fracture mechanics methodology using the modified J, JM is presented and applied to predict load-displacement characteristics of untested specimen geometries.
Stress Component Indices for Elbow-Straight Pipe Junctions Subjected to In-Plane Bending
Authors: Karabin M. E. , Rodabaugh E. C. , Whatham J. F.
Published: November 2009

Through use of the computer code BENDPAC, a number of solutions for elbows attached to straight pipes are produced. This study focuses on the stresses at the elbow-straight pipe junction. It is noted that the largest stress component is in the hoop direction for h values less than 0.5, whereas for h greater than 0.5, the axial stress dominates. Simple expressions for stress indices in both directions are given.
Experimental Investigation of Nozzle-Induced Cylindrical Shell Stresses Where R/T = 1264
Authors: Whipple R. A.
Published: November 2009

Stresses and displacements for a nozzle connection typical of those found in large storage tanks or pressure vessels were measured for applied radial forces, circumferential moments and longitudinal moments. The test program was conducted on a 12 1/2-in-dia penetration, centered and welded into a 60 in. × 60 in. cylindrical panel with a radius to thickness ratio of 1264. The nozzle diameter to cylindrical shell diameter ratio was 0.05. The panel edges were bolted to a stiff rectangular frame. This report presents the measured radial deflections and nozzle rotations, the membrane stress resultants and shell bending moments in the vicinity of the penetration along with penetration membrane and bending stresses for the three loadings. A brief description of the model and the test procedure is also presented.
Appraisal of Allowable Loads by Simplified Rules
Authors: Moulin D.
Published: November 2009

This paper presents a simplified method to analyze the buckling of thin structures like those of Liquid Metal Fast Breeder Reactors (LMFBR). The method is very similar to those used for the buckling of beams and columns with initial geometric imperfections, buckling in the plastic region. Special attention is paid to the strain hardening of material involved and to possible unstable post-buckling behavior. The analytical method uses elastic calculations and diagrams that account for various initial geometric defects. An application of the method is given. A comparison is made with an experimental investigation concerning a representative LMFBR component.
Localized Plastic Buckling of a Heavy Beam on a Contacting Surface
Authors: Yun H. D. , Kyriakides S.
Published: November 2009

The paper considers the uplifting of a long elastoplastic heavy beam on a rigid flat foundation caused by an axial load. The problem is studied through a large deflection formulation. The beam is considered to possess a localized initial geometric imperfection. It is found that the load-deflection response is characterized by a limit load. Plastic effects can precipitate the limit load and cause a more localized type of deformation with higher curvatures. The problem is presented as a model for the “beam mode buckling” of pipelines due to earthquake-caused axial loads.
Structural Analysis of an LMFBR Shield Assembly Duct Under Thermo-Mechanical and Seismic Loads
Authors: Malik S. N. , Sazawal V. K.
Published: November 2009

This paper describes the stress analysis performed to assess structural adequacy of the Clinch River Breeder Reactor (CRBR) core removable shield assemblies. Removable shield assemblies are located in the peripheral region of the core (between blanket assemblies and the fixed radial shield), and are subjected to severe cross-sectional thermal gradients and seismic loads requiring a relatively complex duct load pad design. For cost-effectiveness, the analysis was conducted in two stages. First, an elasto-plastic seismic stress analysis was performed using a detailed nonlinear finite element model (with gaps) of the load pad configuration. Next, in order to determine the total strain accumulation and the creep-fatigue damage the maximum seismic stresses combined with the “worst” thermal stresses from a single assembly model were used to perform a simplified inelastic analysis using two sets of material properties to bound the changing material conditions during reactor operation. This work demonstrated the necessity and applicability of the two simplified analysis techniques in elevated temperature structural design, i.e., the treatment of time-dependent degradation of material properties due to temperature and nuclear irradiation, and the use of time-independent finite element stress analysis results to perform a simplified creep-fatigue analysis.
FEM Analysis of the Collapse Strength of a Tube
Authors: Tokimasa K. , Tanaka K.
Published: November 2009

Using the FEM program, the effects of geometry, residual stress and the elasticplastic behavior of material on the collapse strength of a tube is analyzed and the following results are obtained. The plastic collapse pressure is maximum when the circumferential residual stress on the inner surface is tensile and is equal to 0.7σy. The plastic collapse pressure of a perfectly round tube can be approximately estimated by the following equation independent of the plastic-hardening behavior of the material: P = 2σ0.04 (D/t − 1)/(D/t)2. Based on these FEM results, a new formula is presented to evaluate the collapse strength of a tube.
An Element Independent Corotational Procedure for the Treatment of Large Rotations
Authors: Rankin C. C. , Brogan F. A.
Published: November 2009

A new corotational procedure is developed which enables existing finite element formulations to be used in problems that contain arbitrarily large rotations. Through the use of a nonsingular large rotation vector, the contribution of the rigid body motion of the element to the total displacement field is removed before element computations are performed, with the result that almost any element can be easily upgraded to handle large rotations. This paper contains a derivation of the theory, an outline of the implementation into the STAGS code, and a demonstration of performance for problems involving large rotations and moderate strains.
Experimental Study on Crack Growth Behavior for Austenitic Stainless Steel in High Temperature Pure Water
Authors: Hishida M. , Saito M. , Hasegawa K. , Enomoto K. , Matsuo Y.
Published: November 2009

Crack growth behavior of Type 304 stainless steel in a simulated BWR water environment was investigated for the quantitative characterization of subcritical flaw growth in BWR piping systems. Crack propagation rates under corrosion fatigue and stress corrosion cracking were generated using compact specimens. The effects of several parameters on the rates were discussed. Furthermore, surface crack growth behavior was examined under different modes of cyclic loading, and results were discussed in comparison with compact specimen data. The corrosion fatigue crack propagation rates strongly depended on the frequency and the stress ratio. The rates became higher as the frequency lowered and the stress ratio increased. No effect from dissolved oxygen concentration and heat treatment of the steel was observed in tests, where transgranular cracking mainly took place. Stress corrosion cracking rate data indicated KISCC was above 15 MPa•m1/2. On the other hand, surface crack growth behavior included scattered crack propagation rates. However, the relationship between da/dN and ΔK was basically similar to that obtained in the compact specimens, except under given test conditions, where the acceleration for the crack growth rate at a crack tip on the panel surface was different from that at the deepest point.
Acoustic Emission Testing and Structural Evaluation of Seamless, Steel Tubes in Compressed Gas Service
Authors: Blackburn P. R. , Rana M. D.
Published: November 2009

Tube trailers are used in the distribution of industrial gases. The tubes, which are seamless steel, measure 22-in. diameter, about 1/2-in. wall, and 34 ft long. The U. S. Department of Transportation mandates periodic re-tests of tubes every 5 yr. Acoustic emission re-tests have been substituted for hydrostatic re-tests. This paper presents an analysis of flaws using fracture mechanics methods and establishes a maximum allowable flaw depth. It describes the acoustic emission test method and presents some typical results. Also, some discussion of the hydrostatic re-test is included.
Dynamic Characteristics of Heat Exchanger Tubes Vibrating in a Tube
Support Plate Inactive Mode
Authors: Jendrzejczyk J. A.
Published: November 2009

Tubes in shell-and-tube heat exchangers, including nuclear plant steam generators, derive their support from longitudinally positioned tube support plates (TSPs). Typically, there is a clearance between the tube and TSP hole. Depending on design and fabrication tolerances, the tube may or may not contact all of the TSPs. Non-contact results in an inactive TSP which can lead to detrimental flow-induced tube vibrations under certain conditions dependent on the resulting tube-TSP interaction dynamics and the fluid excitation forces. The purpose of this study is to investigate the tube-TSP interaction dynamics. Results of an experimental study of damping and natural frequency as functions of tube-TSP diametral clearance and TSP thickness are reported. Calculated values of damping ratio and frequency of a tube vibrating within an inactive TSP are also presented together with a comparison of calculated and experimental quantities.
Simplified, Detailed, and Isochronous Analysis and Test Results for
the In-Plane Elastic-Plastic and Creep Behavior of an Elbow
Authors: Sobel L. H. , Newman S. Z.
Published: November 2009

Predictions obtained from simplified and detailed MARC analyses are compared with experimental results for the elastic-plastic and creep behavior of a 16-in-dia 304 stainless steel piping structure subjected to an in-plane closing bending moment. The piping structure is composed of a 90-deg elbow and two straight tangent pipes. The simplified analysis is found to considerably overestimate the measured results, especially for the case of creep behavior. The correlation of detailed analysis predictions with measured results is satisfactory for the elastic-plastic behavior of the structure, and inconclusive for the creep behavior, since the creep predictions are based on a commonly used creep law rather than on the actual (but unmeasured) creep properties. The paper also shows that predictions of creep deformation obtained from the relatively inexpensive time-independent isochronous method of analysis agree well with results given by a “complete” and more costly time-dependent creep analysis.
Analysis of J-Integral and Crack Growth for Surface
Cracks by Line Spring Method
Authors: Miyoshi T. , Shiratori M. , Yoshida Y.
Published: November 2009

This paper describes the analysis of J-integral and crack growth for the surface cracks in work-hardening bodies. First, the complementary energy method has been formulated, which evaluates the stiffness and J-integral of the single-edge-cracked plate under combined tension and bending. Next, the complementary energy method has been combined with the thick shell line spring method in order to analyze the J-integral and crack growth for the surface cracks. It has been shown that the J-integral and crack growth for the surface cracks in work-hardening plates and shells can be analyzed by this method in short computing time and with good accuracy.
Evaluation of the J-Integral of a Crack in a
Pressure Vessel Under Thermal Transient Loadings
Authors: Kikuchi M. , Miyamoto H. , Sugawara S.
Published: November 2009

To assure the safe design of reactor vessels, the parameters of the fracture mechanics are evaluated for an assumed crack subjected to internal pressure and thermal loading. Several kinds of cracks are assumed to exist in the pressure vessel and two and three-dimensional finite element analyses are carried out. As the parameters of fracture, the J-integral and extended ones for a thermal field and a multi-phase material are used. The effect of the cladding on the J values is evaluated and discussed. It is shown that the contraction of the vessel wall, due to the decrease of the temperature at the inner surface, strongly affects the J value. Though three-dimensional analyses, the shape of the growing surface crack is estimated from the distribution of the J values along the crack front.
Analytical Simulation of Dynamically Equivalent
Components
Authors: Ibrahim Z. N.
Published: November 2009

The inertia concept of modal mass was developed to provide a consistent methodology for establishing an analytically equivalent dynamic model of any discrete section within a complex piping network. The multidegree of freedom system is reduced to several multiple excitation single degree of freedom (SDOF) systems representing its modal masses and modal stiffnesses. The multiple excitation residual mass and residual stiffness matrices were also formulated. The combination of modal mass-modal stiffness SDOF systems and residual mass-residual stiffness matrices can simulate the complete dynamic characteristic of any desired portion of the piping network. This technique was extended to cover substructuring applications, and was proved mathematically to be equivalent to the conventional modal synthesis formulation.
Hydrodynamic Pressures on Tanks by Momentum Balance
Authors: Haroun M. A.
Published: November 2009

The application of the momentum balance method for the evaluation of the hydrodynamic pressures in a seismically excited rectangular tank is examined. The method was originally reported by Von Karman and has been recently rationalized by Housner. It uses two apparent masses derived according to the momentum balance in both the vertical and the horizontal directions. The application of the method in a seismic analysis of tanks has clarified a misinterpretation originally associated with the method. Both rigid and flexible tanks are treated, and the resulting hydrodynamic pressure distributions are compared with available solutions.
Refined Theory for Bending and Torsion of Perforated
Plates
Authors: Meijers P.
Published: November 2009

An asymptotic solution is given for the effective elastic constants and the stresses in a perforated plate which is loaded in bending and torsion. In this solution terms 0(h/R)2 are neglected with respect to unity; h being the plate thickness and R the hole radius. In addition to the doubly periodic solution of the classical plate problem another bi-potential problem and two auxiliary problems, viz., a plane strain and a torsion problem for a half-infinite strip, have to be solved. The asymptotic solution together with an approximate solution for an infinitely thick plate permits us often to construct a solution which covers the entire range of h/R; viz., 0≤h/R<∞. In a number of cases accurate interpolation requires additional finite-element calculations. The numerical data presented here apply to a square or an equilateral triangular hole pattern.
Fillet Welds Under Bending and Shear
Authors: Fessler H. , Pappalettere C.
Published: November 2009

A 12-mm-thick plate representing a vessel wall and two others representing attachments on the “inside” and “outside” (forming a symmetrical cross) are jointed by 12-mm, full penetration fillet welds. The attachment plates are in shear and bending; the vessel wall is in tension. Full-size, frozen-stress, photoelastic models of a real weld and four simplified shapes have been made, tested and analyzed to determine surface stresses and their directions in the attachment plate and in the fillet welds. Two-dimensional SCFs for the (horizontal) cross section in tension give safe overestimates of measured peak bending stresses. The directions of the fillet stresses are generally within 20 deg of expected values.
3-D Elastic Analysis of a Circular Nozzle Corner
Crack
Authors: Wilkening W. W.
Published: November 2009

A 3-D linear elastic analysis has been performed for a circular crack located in the nozzle corner region of a nuclear pressure vessel. The stress intensity factor, K, was found to be virtually constant along the crack front for this particular nozzle corner flaw, which extends one quarter of the distance through the nozzle corner diagonal. The magnitude of K is discussed in relation to the stress intensity factor for the ASME Maximum Postulated Flaw, and is compared to the results of a number of other analyses reported in the literature.
Ductile Fracture Micromechanisms in A508 CL3 Structural
Steel
Authors: Barnby J. T. , Creswell S. L. , Nadkarni A. S. , Spencer B. S.
Published: November 2009

Studies of the critical void volumes ahead of cracks at the initiation of fracture at 100° C in the ductile regime show that the void volume has a maximum at a distance of about one to two crack tip opening displacements ahead of the original crack tip. The critical void volume maximum is approximately the same for prefatigue cracked notched bend bars and cusp-shaped cracks (formed by spark machining) at initiation in A508 CL3 steel. The maximum in void volume tends to have a lower value and to be closer to the crack tip for lower values of constraint stresses (that is for lower triaxiality).
Extensions of the Failure Assessment Diagram Approach Semi-Elliptical
Flaw in Pressurized Cylinders—Part II
Authors: Bloom J. M.
Published: November 2009

Approximate closed-form J-integral expressions based on the estimation scheme for use in the Deformation Plasticity Failure Assessment Diagram (DPFAD) approach are presented for an axially oriented semi-elliptical flaw in a pressurized cylinder for crack depth to wall thickness ratios, a/t, from 1/4 to 3/4 and aspect ratios, a/l, from 0 to 1/2. The DPFAD approach was used to derive closed-form J-integral expressions from limited elastic-plastic finite element solutions. Results are also presented in terms of the DPFAD curves as functions of a/t and a/l for the strain-hardening exponent of n = 8.6. Curves are given for the calibration constant h1 as a function of a/t and a/l for ease of interpolation. Lastly, discussion is provided as to the applicability of the solutions and a possible interpolation scheme for obtaining h1 values for n other than 8.6.
Increased Allowable Stresses for Earthquake and Wind Loads in Section
VIII, Division 1
Authors: Selz A.
Published: November 2009

There has been a need for some time to provide rules for allowable stresses for short-time and infrequent loading such as earthquake and wind loads in Section VIII, Division 1 of the Boiler and Pressure Vessel Code. Such rules exist in Section VIII, Division 2, in Section III, and in many other Codes. Division 1 has been silent on the subject. This has caused some manufacturers to make their own rules, and some to overdesign their hardware. Neither situation is without problems. Therefore, in 1979 the Boiler and Pressure Vessel Committee undertook to develop rules for Section VIII, Division 1. This work resulted in the addition of paragraph UG-23(d) to the Code, in the Summer, 1983 Addenda. The paragraph permits an increase in general primary membrane stress of 20 percent for earthquake and wind loads for temperatures below the creep regime.
Analysis of Half-Pipe Heating Channels on Pressure Vessel
Shells
Authors: Blach A. E.
Published: November 2009

Half-pipe heating channels are used on the outside of pressure vessels such as agitators, mixers, reactors, etc., to avoid the high external pressure associated with heating jackets. No applicable method of analysis is contained in the ASME Code and proof tests are normally required for registration with governing authorities. An analytical method is presented which permits the evaluation of stresses in shell and half pipe; numerical examples are included.
Fracture of Circumferentially Cracked Pipes
Authors: Zahoor A.
Published: November 2009

Closed-form expressions are derived for linear elastic axial displacement and bending deflection of circumferentially cracked pipe under combined tension and bending. Formulas are then presented for the applied tearing modulus for: 1) load control and 2) displacement-controlled loading. These formulas are very useful for predicting crack initiation and instability under small-scale yielding conditions.
Prediction of Environmental and Strain-Rate Effects on the Stress Corrosion Cracking of Austenitic Stainless Steels
Authors: Maiya P. S.
Published: November 2009

The stress corrosion cracking (SCC) susceptibility of austenitic stainless steels in high-temperature water is controlled by environmental variables (e.g., dissolved oxygen, corrosion potential, impurities), microstructure (e.g., degree of sensitization), and strain rate. A phenomenological model based on the slip-dissolution mechanism and elastic-plastic fracture mechanics is presented to quantitatively describe the effects of both environment-related parameters and strain rate on SCC in constant extension rate tests. The model predictions are in good agreement with the results of tests performed on Types 304, 316, and 316NG stainless steel at different strain rates in a wide variety of environments relevant to boiling-water reactors.
Progress in Collapse Analyses
Authors: Riks E.
Published: November 2009

In the field of finite element structural analysis, the computation of collapse states of structures prone to unstable behavior has long been considered a difficult if not intractable problem. Only recently have procedures that deal effectively with this difficulty found their way in general-purpose finite element codes. Although the explanation for the cause of the so-called limit point obstacle is actually simple—an inappropriate parameterization of the governing equations in the neighborhood of the limit point—this cause does not seem to have been widely understood in the period of development of the finite element technique. In this paper, some of the remedies that have been proposed to overcome the problems are reviewed, including the principle of adaptive parameterization which is now the basis of a new procedure for collapse analysis in the finite element code STAGS. The discussion also includes the treatment of simple bifurcation points because unstable bifurcation can be considered a special form of collapse. It can be concluded that collapse problems, in the sense discussed in this paper, no longer present difficulties that exceed those normally encountered during the solution of nonlinear deformation paths. Further developments, in particular those with respect to improved efficiency, are in progress. Some of the promising ventures in this direction are indicated.
A Method for Correlating Severity of Different Seismic Qualification Tests
Authors: Kana D. D. , Pomerening D. J.
Published: November 2009

A general methodology has been developed for correlating the severity of various seismic qualification motions that can have very different dynamic characteristics. The approach is based on a vibrational equivalence concept which allows a severity comparison between two different waveforms. The comparison is in terms of a fragility ratio, DFR, which is a ratio of vibrational input level to that which the specific equipment is capable of sustaining at its fragility level. Measurement of the severity at both levels can be characterized in terms of response spectrum, power spectrum, or other parameters which may be used, or have been used, in typical equipment qualification procedures. Relationships among the various parameters are defined so that transformations from one to another are possible. The inherent use of the fragility function for the methodology causes some problem in that such data are not generally included in previous qualification information. This problem is overcome by defining a lower-bound, or acceptable approximate fragility function, which is based on the previous qualification levels. A method of measuring relative severity of two motions is also developed in terms of a relative severity ratio, DSR. This ratio is proportional to several other relative severity factors that have been established by other researchers.
Impact Simulation of Process Equipment Tubes and Support Plates—A Numerical Algorithm
Authors: Sauve´ R. G. , Teper W. W.
Published: November 2009

The occurrence of flow-induced vibration fretting wear in process equipment such as heat exchangers and steam generators accounts for the majority of the failures due to vibration. One of the parameters which plays a vital role in the prediction of tube wear rate is the impact force which occurs when the free displacements of the tube exceed the clearance in the support plates, resulting in a collision. To date the determination of these impact forces reported in the literature has been restricted to simplified mathematical models which consider only straight spans of tube with gaps. The need to consider more generalized configurations has led to the development of an analytical method which simulates the nonlinear dynamic-impact response of multi-supported tubes including U-bends and the effect of nonuniform gap clearances at the supports. The approach is incorporated into a computer code based on the finite element and displacement methods using an unconditionally stable numerical integration scheme to solve the nonlinear equations of motion. The algorithm developed includes equilibrium iteration and variable time stepping based on convergence criteria, which ensures that temporal solution errors are minimized. The direct integration of the equations enables all the frequencies (subject to the finite element mesh) to be included. This is necessary since the high-frequency response at impacting may be significant. At present, the method is being used to simulate impact between tubes and support plates in steam generators and heat exchangers in order to determine tube bundle susceptibility to fretting wear failure at the design stage or operational phase. The paper describes the analytical development of the method, verification cases, and applications to the problem of tube/support plate impacting.
Acoustic Resonance in Heat Exchanger Tube Bundles—Part II: Prediction and Suppression of Resonance
Authors: Blevins R. D. , Bressler M. M.
Published: November 2009

In the first part of this series, experimental data were presented which suggest that the acoustic resonance in heat exchanger tube bundles is tied to periodic vortex shedding from the tubes. In this paper, a semi-empirical model for predicting the onset of resonance is developed. This model is compared with experimental data and other models from the literature. Methods of suppressing the resonance are developed and experimental data on their effectiveness are presented.
Structural Assessment Techniques for Thermal Striping
Authors: Clayton A. M. , Irvine N. M.
Published: November 2009

Life assessment techniques for components subject to random surface temperature fluctuations (thermal striping) are outlined. The approach depends on the thermal information available and ranges from simple evaluation of the initiation of fatigue cracking to the complete analysis of crack growth. A new bounding technique is described, and some uncertainties in the various analyses listed.
Residual Stress Effects on Fatigue Crack Growth Behavior in Stainless Steel Welds
Authors: Mills W. J. , James L. A.
Published: November 2009

Standard fatigue precracking of fracture toughness specimens taken from stainless steel welds with a double-V design was found to result in extremely uneven crack fronts. Material variability within the weld zone could not explain the irregular crack fronts, which must therefore be associated with residual stress effects. Uniform fatigue cracks could be obtained by sectioning the double-V weld at the mid-thickness to relieve residual stresses and by precracking at a stress ratio of 0.4. Residual stresses can impact the leak-before-break position for welded structures.