bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Reliability of Ocean Vehicles Using Asymptotic Wave Load Distribution
Authors: Mansour A. E. , Sinha R. N.
Published: November 2009

Asymptotic extreme distribution of wave loads acting on a marine vehicle is derived and used in a reliability framework to estimate the safety of the structure. Both exact and approximate methods of reliability analysis are used and the resulting probabilities of failure are compared. The effect of correlation between the wave load and the still water load on the risk of failure is also examined. The results of the comparison showed that the approximate reliability analysis underestimates the failure probability compared to the exact method, and that the correlation effect between the wave and still water loads is not significant.
Numerical Modeling and Subharmonic Bifurcations of a Compliant Cylinder Exposed to Waves
Authors: Liaw C. Y.
Published: November 2009

The occurrence of subharmonic responses in compliant structures including nonlinear coupling between the wave force and the structural motion is studied using simplified models of a cylinder submerged in waves. In particular, the existence and sensitivity of subharmonics in the responses are evaluated by varying the mathematical model for wave force, the structure/wave frequency ratio, the drag coefficient and the wave height. It is concluded that subharmonic bifurcation of order 1/2 can be a common phenomenon in compliant structural systems, especially if the system has a low ratio of drag force to inertia force.
A Comparison of Methods for Synthesis of Directional Seas
Authors: Miles M. D. , Funke E. R.
Published: November 2009

Numerical models for synthesis of directional seas are evaluated. Several authors have recently reported limitations associated with the commonly used double summation model which is neither ergodic nor spatially homogeneous for a finite number of terms. In order to overcome these problems, a modified double summation model is presented which uses unidirectional, narrow-band random wave trains as the fundamental components rather than plane sinusoidal waves. Various alternatives for generating the fundamental wave trains are investigated by numerical simulation and results are also compared to a simpler single summation wave model.
Behavior of Unstiffened and Stiffened Steel Tubular T-Joints
Authors: Raghava G. , Rao A. G. M. , Murthy D. S. R.
Published: November 2009

Offshore towers standing in deep sea are susceptible to cyclic nature of wave forces. Fatigue failure initiates at the welded tubular joints of these structures where a very high stress gradient and localized stress concentration exist due to abrupt changes in the geometry. Stress concentration plays a vital role in the design of steel tubular joints, as it directly affects the fatigue life of the structures. This paper presents results of an experimental study on the behavior of an unstiffened and a stiffened steel tubular welded T-joint under axial brace loading. The effect of internal ring stiffeners has been studied theoretically and experimentally. In the experimental technique, the specimens were extensively strain-gaged and the stress distribution determined under static load. The analytical results have been obtained by finite element technique.
The Design of Tension Leg Platforms by a Constrained Optimization Method
Authors: Nordgren R. P.
Published: November 2009

A method is developed for optimizing the size of a tension leg platform (TLP) and its tethers so as to minimize the weight-based cost of the TLP system subject to various design constraints. The method is intended for preliminary design studies of feasibility and cost sensitivity. Design constraints include minimum tension and maximum tensile stress in the tethers, maximum platform offset under current and waves, and minimum fatigue life of the tethers due to resonant vibration. Other given quantities include deck load, riser pretension, tether properties, and basic results from structural design studies and hydrodynamic analysis or model tests for a specific class of platforms. Example in TLP design studies are presented to illustrate application of the constrained optimization method.
Hydrodynamic Loading on Macro-Roughened Cylinders of Various Aspect Ratios
Authors: Theophanatos A. , Wolfram J.
Published: November 2009

This paper describes experiments which comprise part of the UK joint SERC/industry-sponsored program on fluid loading. The experiments have been undertaken in a novel test rig which accelerates a cylinder from rest to a constant velocity in a still water tank and cover the Reynolds number range 105 to 106. Results are presented for 30 cylinders ranging in diameter from 150 mm to 400 mm. The test program comprised: (a) cylinders with different distributions of marine growth (mussels and kelp) and artificial roughness at low surface cover; (b) fully sand/gravel-roughened cylinders with aspect ratios (L/D) from 3.75 to 10 and relative roughness (k/D) up to 0.025; (c) cylinders covered in regular arrays of pyramids at (k/D) up to 0.1. Based on the results, some tentative conclusions are drawn about the estimation of the effect of marine fouling on the fluid loading of offshore structures.
Buckling Under Normal Pressure of Cylindrical Shells With Various End Conditions
Authors: Malik Z. , Morton J. , Ruiz C.
Published: November 2009

A simplified method of analysis, capable of predicting the buckling pressure of cylindrical shells with varying degrees of end restraint is presented and compared to published results. The case of the free end is given special attention since no complete analytical solution is known to the authors.
Kinetics of Void Development in Fracturing A533B Tensile Bars
Authors: Shockey D. A. , Seaman L. , Dao K. C. , Curran D. R.
Published: November 2009

The phenomenology of fracture in A533B pressure vessel steel was established by examining fractured and partially fractured round bar tensile and Charpy specimens. In the upper shelf region (above 200°F, 366°K) fracture occurs by the nucleation, growth, and coalescence of voids. Quantitative data establishing the void kinetics were obtained by counting and measuring fracture surface dimples and voids below the fracture surface. A computational fracture model is being constructed based on the observed fracture phenomenology and experimental void kinetics data. The model, written as a subroutine for use in finite difference computer codes, is intended to generate fracture toughness data that can be used to calculate critical loads in reactor components.
Dynamic Propagation of Circumferential Cracks in Two Pipes With Large-Scale Yielding
Authors: Emery A. F. , Kobayashi A. S. , Love W. J. , Jain A.
Published: November 2009

The dynamic motions of circumferentially oriented, through cracks in two axially pre-stressed pipes were analyzed by a finite-difference shell code in the presence of large-scale yielding. Lacking any dynamic fracture criterion for large-scale yielding, a static ductile fracture criterion based on crack-tip opening angle (CTOA) was used. The results for a 6-in- (15.2-cm-) dia A533B steel and for an 18-in- (45.7-cm-) dia 316 stainless steel pipe subjected to axial loads showed that crack velocities were reduced to less than one half of the corresponding crack velocities of comparable brittle cracks. The onset of ductile crack propagation was delayed significantly in the larger 18-in- (45.7-cm-) dia 316 stainless steel pipe, thus indicating that this hold-off time is influenced by the inertia of the separating pipe segments. The importance of a realistic dynamic ductile fracture criterion is underscored.
Dynamic Finite Element Analysis of Cracked Bodies
Authors: Glazik J. L.
Published: November 2009

Application of the finite element method to problems involving finite cracked bodies subjected to impact loadings is discussed. Mass matrices for a particularly simple, well-established singular element have been developed and applied to the problem of a centrally cracked strip whose ends are loaded by a step tensile stress. The results agree extremely well with those obtained by using a higher order singular element. Results are also presented for this problem employing an equally coarse finite element mesh with no singular element at all, and again good agreement is demonstrated. The problems of an edge cracked strip suddenly pulled at its ends and of a cracked cylinder subjected to sudden internal pressure are also analyzed using these two approaches. The response of these examples, like the majority of cracked finite bodies, are dominated by their vibrational modes. Results indicate that for the purpose of determining the maximum amplification of the stress intensity factor due to dynamic loading, the use of a singular element is unnecessary.
Pressure Transient Analysis in Piping Systems Including the Effects of Plastic Deformation and Cavitation
Authors: Youngdahl C. K. , Kot C. A. , Valentin R. A.
Published: November 2009

Computational methods for analyzing pressure transients in the intermediate heat transport system of a sodium-cooled breeder reactor are being developed at Argonne National Laboratory. The pressure pulses produced by a sodium/water reaction in a steam generator may plastically deform sections of the piping, and wave interactions may then produce cavitation in the system. Both these phenomena have a large effect on the pressure pulses traversing the pipe network and, consequently, on the transient loading on major components. Comparisons will be shown between predictions of the PTA-2 computer code and the results of experiments performed at Stanford Research Institute. In these experiments, a pressure pulse caused plastic deformation of a thin-walled pipe, producing a rarefaction wave which then produced a cavitated region in another pipe.
Response of Water-Filled Thin-Walled Pipes to Pressure Pulses: Experiments and Analysis
Authors: Romander C. M. , Schwer L. E. , Cagliostro D. J.
Published: November 2009

Experiments are performed to verify modeling techniques used in fluid-structure interaction codes that predict the response of liquid-filled piping systems to strong pressure pulses. Pressure pulses having a 150-μs rise time, a 2000-psi (13.8 MPa) magnitude, and a 3-ms duration are propagated into straight, water-filled Ni 200 pipes (3-in. (7.6-cm) O.D. 0.065-in. (0.165-cm) wall). Attenuation of the pressure pulse and the strain and deformation along the pipes are measured. The experiments are modeled in WHAM, a two-dimensional, finite-element, compressible fluid-structure interaction code. The experimental and analytical results are discussed in detail and are found to compare favorably.
The Effect of Corner Radius on Plate-Cylinder Intersections
Authors: Laberge C. A. , Baldur R.
Published: November 2009

Curves are presented for the stress concentration factors due to inside corner radii between cylinders and flat-head closures. The analysis is based on a finite element study of pressure loaded cylinder-plate intersections in which the significant parameters were systematically changed in order to cover the complete field of useful design boundaries. The results are based on a solution using some 240 elements (nearly 1000 degrees of freedom) and sufficient number of points have been calculated to produce smooth curves. The application of the results permits a more realistic determination of fatigue dependent stresses in pressure vessels and indicates the sufficient hub lengths for welded constructions. The paper indicates the degree of conservatism of the ASME Boiler and Pressure Vessel Code and shows that cost savings can be achieved by reference to the theoretical data contained herein.
A Theoretical Model for Self-Excited Vibrations in Hydraulic Gates, Valves and Seals
Authors: Weaver D. S. , Ziada S.
Published: November 2009

A general theoretical model is presented for the jet flow mechanism of self-excited vibrations of flow control devices operating at small openings. The coupled nonlinear differential equations are solved numerically using the Runge-Kutta method. The vibration displacement and discharge characteristics are given for a variety of parameters such as structural stiffness, fluid inertia and discharge coefficient. The predictions are shown to agree reasonably well with the experimental observations of swing check valve vibrations.
Calculations of Added Mass and Damping Coefficients for Hexagonal Cylinders in a Confined Viscous Fluid
Authors: Yang C. I. , Moran T. J.
Published: November 2009

A finite element model is formulated and computations performed for the hydrodynamic reactions of harmonically oscillating hexagonal cylinders in an incompressible, viscous fluid. Regular hexagonal cylinders pack closely together, increasing the hydrodynamic coupling effect. The formulation is based on a velocity and pressure approach assuming the amplitude of the motion is sufficiently small to allow linearization of the Navier-Stokes equations. The equations of motion are discretized through a Galerkin process with a six-node triangular finite element mesh. C°-type elements and mixed interpolation functions are used with quadratic functions for velocity and linear functions for pressure. The hydrodynamic reactions, in terms of added mass and damping coefficients, of an hexagonal cylinder oscillating in a confined circular cylinder and an array of seven hexagonal cylinders in a confined domain are computed. The effects of the size of the gap between adjacent cylinders and the frequency of oscillation are studied.
Stresses and Displacements at the Intersection of Two Right Cylindrical Shells Subject to a Nonequilibrated Loading
Authors: Naghdi A. K. , Gersting J. M.
Published: November 2009

Cylindrical shells having pipe attachments and branches are extensively used in many industrial installations. Boilers, reactors, and cylindrical tanks are obvious examples. In this investigation the solution to the problem of stresses and displacements at the intersection of a simply supported circular cylindrical shell with a pipe attachment subject to a uniform load on its top is derived. It is assumed that the axes of the two cylindrical shells are intersecting and that they are perpendicular. Numerical values of stress resultants and stress couples at various points along the intersection curve of the two shells for several geometrical configurations are presented.
On the “Slip-On” Buckle Arrestor for Offshore Pipelines
Authors: Kyriakides S. , Babcock C. D.
Published: November 2009

If a pipeline buckles in the presence of sufficiently large external pressure a propagating buckle is initiated. The buckle propagates along the pipeline until it encounters a region of adverse conditions—low pressure or an arresting device. This paper describes a complete experimental analysis of the parametric dependence of the so-called “slip-on” arrestor. An empirical formula is derived for the efficiency of this arrestor. It was also found that quasi-static design criteria underestimate the arrestor efficiency under dynamic conditions. Any gap between the arrestor and the pipe greatly affects the efficiency.
A Finite Element Model for Elastic and Slip Responses of Fusion Magnets
Authors: Chang T. Y. , Suzuki H. , Reich M.
Published: November 2009

A finite element model to simulate the elastic and slip responses of fusion magnets under operating loads is proposed. To represent the elastic actions, a material homogenization procedure based on the existing composite technology was applied to obtain the effective stress strain relations for the heterogeneous, laminated magnets. In addition, a friction-type model was utilized to simulate the interlayer slip of the magnets when the shear stresses reach the bonding strength of the adhesives. Numerical examples are given to demonstrate the applicability of the proposed model.
The Plastic Modulus Method for Experimental Limit Loads
Authors: Schroeder J.
Published: November 2009

A theory is proposed such that slopes of tangents drawn to plastic portions of load-displacement curves for the determination of limit loads can be estimated using the elastic portion of load-displacement curves, the elastic modulus and a plastic modulus. The approach is called “the plastic modulus method” and appears to reduce uncertainties in the use of the tangent-intersection method.
Analytical Puncture Study of Circular Metal Plates
Authors: Shieh R. C.
Published: November 2009

An existing closed-form solution for large-deflection static responses of centrally loaded, rigid, perfectly plastic circular metal plates (with emphasis on steel plate cases) that are clamped (built-in) or simply supported at the edges is first modified to take into account the effects of elastic deformation and material strainhardening in an approximate manner. The modified theoretical solution is first shown to correlate very well with experimental results. Then it is applied in solving the quasi-static plate puncture problem in which the punch bar penetrates slowly into the plate. An analytical/experimental correlation study on punch force-deflection relationship and incipient plate puncture energy is made on newly obtained experimental data. Effects of variation of strainhardening parameter, boundary conditions and shear deformation on incipient puncture energy are studied, and plate puncture design curves are developed in the form of nondimensional incipient plate puncture energy as a function of punch diameter/plate thickness ratio for various values of punch diameter/plate diameter ratio. Application of these analytical techniques/design curves to the design of nuclear shipping cask plate components subject to regulatory puncture drop loading is also discussed.
Analysis of Bolted Joints with Nonlinear Gasket Behavior
Authors: Soler A. I.
Published: November 2009

Design methods for full face gaskets in bolted pressure vessel joints have received little attention in the literature. Such gasketed joints play a prominent role in attaching rectangular plan from water boxes to rectangular tubesheets in condenser water boxes. With higher cooling water pressures becoming evident due to cooling tower circuits, the water box-tubesheet structure, and its bolted joint connection requires rigorous analysis for both structural integrity and leak tightness. Although it is well known that gasket material has a highly nonlinear stress strain behavior, very few analyses are available to calculate and evaluate the effect of the nonlinear gasket behavior in a bolted joint connection. In this paper, an approximate method for simultaneously analyzing structural integrity and leak tightness of typical bolted flange connections with nonlinear gasket material is developed. The flange is modeled as an elastic element, the bolt is simulated by a linear spring with bending and extensional resistance, and the gasket is modeled by a series of nonlinear compression springs. A simple nonlinear stress-strain relation for initial loading and unloading of the gasket is developed based on experimental data. The analysis technique employs an incremental procedure which follows the configuration through preloading and pressurization and checks structural integrity and gasket leakage. To illustrate the method, a typical full face gasket and flange construction is studied, and the effect of gasket properties on the final state is investigated. A series of simulation results are obtained which illustrate clearly the effect of gasket prestrain, undersizing of bolts, and wall rotational resistance. Of particular importance is a simulation comparing results obtained using actual nonlinear gasket stress-strain data with results obtained using linear models for the gasket. It is demonstrated that for full face gasket configurations, simulation of the nonlinear behavior is required to achieve accurate results. The procedure developed in this work is ideal for optimization of flange gasket configurations because of its cost effectiveness while simultaneously evaluating the interaction between structural integrity and joint leak tightness.
Inelastic Flexibility and Strain Concentration of Pipe Bends in Creep Range with Plastic Effects
Authors: Watanabe O. , Ohtsubo H.
Published: November 2009

The creep behaviors of pipe bends under in-plane bending are studied by the use of the simplified ring element method. The typical two loading cases are studied; (a) constant in-plane moment, and (b) constant in-plane rotation. The present paper investigates (a) inelastic flexibility, (b) creep strain concentration, and (c) stress relaxation by considering effects of yielding on creep deformations. The numerical results verify the validity of the previous analytical methods for elastic stationary creep behaviors by Spence or Kachanov.
A General Fatigue Evaluation Method (Elastic Stress or Plastic Strain with Constant or Varying Principal Direction)
Authors: Kelley F. S.
Published: November 2009

A method is proposed for ASME Section III fatigue evaluations which can be applied in the elastic or plastic ranges with constant or varying principal stress/strain directions. The generality of the method is demonstrated. For biaxial or triaxial loadings, the method is shown to be more consistent than the Code procedure given in NB-3228.1.
A Damage-Tolerant Design and Inspection Philosophy for Nuclear and Other Pressure Vessels
Authors: Adams N. J. I.
Published: November 2009

Statistical analyses of pressure vessel failure rates indicate that, to date, the record is very good. However, the public hazard and environmental consequences of failure in certain industrial processes now give cause for much greater concern. With the exception of an Appendix in ASME III, the current design codes and requirements for new vessels are all based on the assumption that they are free from cracklike defects, but engineers recognize that such perfect vessels cannot be manufactured. Taking into account failure mechanisms, material properties, pre and in-service inspection, proof testing, failure statistics and probabilistic methods, views are put forward on how a damage-tolerant design and inspection philosophy may be developed to reduce further the possibility of “rogue” vessel failure.
Creep Analysis of Orthotropic Rotating Cylinder
Authors: Bhatnagar N. S. , Arya V. K. , Debnath K. K.
Published: November 2009

The stress and strain-rate distributions in the wall of a hollow thick-walled circular cylinder, rotating about its own axis with a constant angular speed, have been obtained using Norton’s law for the steady-state creep. The cylinder is assumed to be made of a homogeneous and orthotropic material. The numerical computations, for a number of steels and steel alloys commonly used to manufacture the cylinder, have been carried out for three cases of anisotropy. The effect of anistropy and of exponent n in creep law has been studied. It is observed that the stress and strain-rate distributions are significantly affected by the anisotropy of material and the value of exponent n. It is also noticed that the values of the effective stress for an anisotropic material for which the ratios of axial to tangential strain rate and of radial to tangential strain rate are equal to 1.2, are lower than the corresponding values for an isotropic material for which these ratios are 1.0. And, because of a power law between effective strain rate and effective stress, much lower values of the effective strain rate for the foregoing anisotropic material than those for the isotropic material will be obtained. Thus the use of the aforementioned anisotropic material may be beneficial for the manufacture of the cylinders because (i) it will result in a longer life for the cylinders (because of the lowest strain rate), or (ii) it will allow the cylinder to sustain larger forces without a risk of failure under creep.
The Effects of Geometric Irregularities on the Design Analysis of Thin-Walled Piping Elbows
Authors: Thomas K.
Published: November 2009

Geometric irregularities, such as ovality, in thin-walled elbows are known to give additional stresses under internal pressure loading. This paper presents results of detailed analyses, using the STAGS program, of a range of elbow geometries which have specified nonuniformities. Nonuniformities considered were thickness variation, initial ovality, intrados wrinkling and shrinkage of longitudinal welds. Loadings were in-plane bending and internal pressure. Results show that stresses due to in-plane bending are not significantly affected by the nonuniformities. However, stresses due to internal pressure are amplified by through-the-wall bending due to noncircularity of the cross section. Ovality, wrinkling and longitudinal weld shrinkage produce stress perturbations of comparable magnitude under internal pressure. Numerical data from the analyses are reduced to polynomial functions which give the maximum stress in the elbow as a function of pressure, radius-thickness ratio and degree of nonuniformity for long and short radius elbows.
Stress and Strain Concentrations in Perforated Structures Under Steady Creep Conditions
Authors: Porowski J. S. , O’Donnell W. J. , Tanaka T. , Badlani M.
Published: November 2009

Steady creep solutions are obtained for perforated materials under various loading conditions. Norton’s creep power law is used and the plane stress problem is analyzed for both the triangular and square penetration patterns of circular holes. Maximum local stresses at the hole boundaries are obtained for calculating creep rupture damage. Local creep strain concentration factors are also obtained. The interrelations between the elastic, plastic and creep solutions are investigated.
Elastic Thermal Stresses in Bimetallic Pipe Welds
Authors: Blevins R. D.
Published: November 2009

The elastic thermal stresses in a welded transition between two pipes of the same size but different alloys are explored. A stress-free temperature is postulated and the stress due to a uniform change in temperature is characterized by the maximum stress intensity in the weld. A simple expression for predicting this maximum stress intensity is developed based on the results of finite element analysis.
Approximate Elastic Stresses in a Tee Branch Pipe Connection Under Internal Pressure
Authors: Updike D. P.
Published: November 2009

An approximate method for calculating the elastic stresses at the crotch of a tee branch pipe connection under internal pressure is presented. The analaysis is based on shell theory together with stress multipliers for the peak bending stress in the fillet. A table of factors for rapid calculation is given.
Background of New Code Rules for Integral Flat Heads with a Large, Central Nozzle
Authors: Schneider R. W.
Published: November 2009

Paragraph UG-39 (c) of ASME Section VIII, Division 1, 1980 Edition states: “Flat heads that have an opening with a diameter that exceeds one-half of the head diameter or shortest span, as defined in UG-34, shall be designed as a flange in accordance with the Rules for Bolted Flange Connections given in Appendix 2.” The application of Appendix 2 to such configurations is subject to various interpretations, accordingly, rules have been written for the specific case of a single, large central opening (nozzle) in integral flat heads. The new rules will appear in the Winter 1980 Addenda; for configurations not provided for the designer is referred to U-2 (g).
Recent Advances in the ASME Section VIII Division 1 and 2 Pressure Vessel Codes
Authors: Karcher G. G. , Ecoff R. A.
Published: November 2009

Numerous revisions, updates and advances have been incorporated in the ASME Section VIII Code on “Pressure Vessels.” All of them have been published in “Mechanical Engineering” as required by ANSI accredited organization procedures and a few have also been the subject of specific technical papers. The objectives of this paper is not the duplication of these already published works but rather a highlighting of the more significant or, in some cases, subtle revisions that have been incorporated in Section VIII since the 1974 edition. By way of introduction, the basic design philosophies of Division 1 and 2 are also outlined.
A Hybrid Numerical Method for Homogeneous Equilibrium Two-Phase Flows in One Space Dimension
Authors: Shin Y. W. , Wiedermann A. H.
Published: November 2009

This paper discusses a hybrid numerical method to calculate homogeneous equilibrium two-phase flows in one space dimension. A finite difference method is used for field solution while the method of characteristics is employed for treating boundary conditions. The boundary method is a new method that uses an integral procedure for precise specification of boundary values leading to an accurate overall solution. No extraneous information, or nonphysical approximation, is required as often is the case in most other attempts where the boundary error was the cause of difficulties and was detrimental to the inaccuracy of the overall solution and the eventual numerical instability due to the large gradient in phase distribution commonly existing near the boundaries. Procedures for many types of boundary conditions commonly encountered in reactor system analyses have been formulated and discussed. Sample problems have been calculated for two-phase water/steam mixture and single-phase nitrogen gas. The results are presented to demonstrate the degree of accuracy attainable from the hybrid method. The basic method discussed may be generalized to apply to more general nonequilibrium two-phase flow models with unequal phase velocities provided real characteristics exist.
Pulse Propagation in Fluid-Filled Elastic Curved Tubes
Authors: Hu C. K. , Phillips J. W.
Published: November 2009

The propagation of fluid transients through elbows is studied. A set of one-dimensional governing equations for the propagation of pressure pulses in an inviscid compressible fluid contained in a thin-walled naturally curved elastic tube is formulated and solved by two different techniques. For continuous waves, reflection and transmission coefficients for elbows are determined numerically by considering periodic waves in an assemblage of straight and curved tubes. For pulse propagation, the method of characteristics is employed to solve the assemblage problem. An experimental arrangement for pulse studies is described and experimental results are compared with numerical results from the method of characteristics.
Dynamic Crack Propagation in Precracked Cylindrical Vessels Subjected to Shock Loading
Authors: Popelar C. H. , Gehlen P. C. , Kanninen M. F.
Published: November 2009

Previous work has shown that a speed-independent dynamic fracture toughness property can be used in an elastodynamic analysis to describe crack initiation and unstable propagation under impact loading. In this paper, a further step is taken by extending the analysis from simple laboratory test specimens to treat more realistic crack-structure geometries. A circular cylinder with an initial part-through wall crack subjected to an impulsive loading on its inner surface is considered. The crack is in a radial-axial plane and has its length in the axial direction long enough that a state of plane strain exists at the center of the crack. Crack growth initiation and propagation through the wall is then calculated. It is found that, once initiated, crack propagation will continue until the crack penetrates the wall. Crack arrest within the wall does not appear to be possible under the conditions considered in this paper.
Acoustic Emission Monitoring During Rupture Test of Pressure Vessel and Laboratory Fracture Test
Authors: Ohtsuka N. , Nakano M. , Ueyama H.
Published: November 2009

In order to relate the results of a field AE test on a large structure to observations made from small laboratory specimens, acoustic emission (AE) was monitored during a pressurization test on a model vessel containing several kinds of artificial defects and during laboratory tests on small specimens to simulate the defects. The active AE sources in the vessel were concentrated mainly around an artificial weld crack and a sawcut notch. The total number of AE events is compared with displacement, load, crack tip opening displacement, and AE signal amplitude under various test conditions on two types of defects. The significant difference in AE generating mechanism, size of defects, loading parameter and rate between the tests is discussed by the fracture mechanics approach.
Further Numerical Studies on Dynamic Circumferential Crack Propagation in a Large Pipe
Authors: Awaji H. , Kobayashi A. S. , Emery A. F. , Love W. J. , Perl M. , Kistler B. L.
Published: November 2009

Dynamic ductile crack propagation analyses of pre-existing circumferential through cracks in a large pipe subjected to uniaxial tension were conducted by a finite difference dynamic shell code. These dynamic results together with the results of previous dynamic ductile circumferential crack propagation suggest that crack propagation in the presence of large-scale yielding is controlled mainly by the rotary inertia of the two fracturing pipe segments.
Piping Response to Steam-Generated Water Hammer
Authors: Gruel R. L. , Huber P. W. , Hurwitz W. M.
Published: November 2009

Theoretical estimates are presented for the impulse generated by the collapse of a steam bubble trapped by a column of subcooled liquid in a pipe. Predictions are compared with experimental results obtained in a laboratory scale test system. The excitation of pipe responses by the transmission of the water hammer impulse through pipe bends is discussed and predictions are presented for two simple piping configurations. Experimentally measured pipe deflections excited by a steam-generated water hammer are compared with the predictions.
Piercing of Cylindrical Tubes
Authors: Johnson W. , Reid S. R. , Ghosh S. K.
Published: November 2009

Experiments are described in which cylindrical tubes were perforated normally at their central section. Quasi-static tests were performed using mainly square-section punches possessing pointed pyramidal heads of semi-angle 30 deg, the tubes being supported along their support generator. The dynamic tests comprised high-speed penetration of tubes using conically headed cylindrical projectiles. The equipment and experimental procedures are briefly described and results are presented showing typical punch load-penetration curves, the variation of punch load with tube length and that of a nondimensional characteristic punch load (defined later) with length-to-diameter ratio of the tubes. Typical specimens and the sequence of events during the course of a penetration process are also illustrated. The characteristics of petalling and plugging modes of failure together with those effects which are specifically dynamic in character are reported.
On the Buckling Design of Spherical Shells
Authors: Morton J. , Murray P. R. , Ruiz C.
Published: November 2009

Experimental results are interpreted in the light of numerical analaysis, imperfection sensitivity and Design Codes. Two cases are discussed: spherical shells under uniform external pressure and partly filled spherical shells, supported on a continuous equatorial ring. The imperfection sensitivity associated with the first loading case leads to the selection of safety factors that depend on the actual shell stiffness. The second case, in which the load results in a biaxial tension-compression state of stress, is treated approximately in terms of a plate under biaxial load.
A Computational Model for Improving Weld Residual Stresses in Small Diameter Pipes by Induction Heating
Authors: Rybicki E. F. , McGuire P. A.
Published: November 2009

Girth welding can produce tensile residual stresses on the pipe inner surface. Because tensile stresses enhance the possibility of stress corrosion cracking, methods for altering the weld-induced stress state are being investigated. One method, Induction Heating for Stress Improvement (IHSI), involves induction heating the pipe while cooling the inner surface. The method is being evaluated using both experimental and computational studies. This paper presents computational results of a 101.66-mm (4-in.) Schedule 80 stainless steel pipe. Results include comparisons of computed values for residual stresses with laboratory data. Computed values of residual stresses and laboratory data are in agreement and, for this case, clearly show that the IHSI process can change weld-induced tensile residual stresses to compressive values. A comparison of computational results for applying the IHSI process to a stress-free pipe and a welded pipe indicate that for geometry and process parameters considered here, the IHSI-induced compressive residual stresses on the pipe inner surface for these two cases are similar. The experimental results presented here show the feasibility of controlling weld-induced residual stresses. The computational results demonstrate a capability for predicting the observed stress behavior. The computational capability then provides an efficient tool to aid in developing ways for controlling residual stresses for other pipe sizes and weldment geometries.
Corrosion Fatigue Crack-Growth Behavior of HY-130 Steel and Weldments
Authors: Davis D. A. , Czyryca E. J.
Published: November 2009

Fatigue crack propagation was studied in HY-130 steel base plate, as-deposited shielded metal-arc weld metal, and gas metal-arc weld metal using compact specimens. The effects of seawater, cathodic protection, frequency and hold time were investigated. The results indicated that saltwater increased crack-growth rates in HY-130 base plate at stress intensity factors below 60 ksi in. No significant effects of cyclic load-wave pattern or of frequency (0.10 to 10 cycles per min.) were evident. Cathodic potentials from zinc (−1.05 V) and magnesium couples (−1.40 V) increased fatigue crack-growth rates in seawater. Fatigue crack growth in the weld metals showed different characteristics than in wrought materials in that higher stress intensities were required to initiate crack growth, and growth rates increased over a narrow range of stress intensity. Results of the environmental effects of weld metals indicated that, even under the most severe conditions of cathodic potential in seawater, fatigue crack-growth rates in weld metal were lower than those observed with base plate in air.
Experimental Determination of the Propagation Pressure of Circular Pipes
Authors: Kyriakides S. , Babcock C. D.
Published: November 2009

Local geometric imperfections on pipes under external pressure can lead to local buckling which under the “right” conditions can cause the initiation of a propagating buckle. This buckle, driven by the pressure, propagates up and down the pipe flattening it. The lowest pressure which can sustain a propagating buckle is called the propagation pressure and is a characteristic pressure of the pipe. Experiments have shown this pressure to be dependent on the post yield characteristics of the pipe material behavior, as well as the diameter-to-thickness ratio of the pipe. The collapse mechanism has been modeled by the collapse of a ring under external pressure. By identifying the lowest postbuckling pressure of the ring with the propagation pressure an empirical expression for the latter quantity has been established.
A Plastic Fracture Mechanics Prediction of Fracture Instability in a Circumferentially Cracked Pipe in Bending—Part II: Experimental Verification on a Type 304 Stainless Steel Pipe
Authors: Wilkowski G. M. , Zahoor A. , Kanninen M. F.
Published: November 2009

The possibility of a pipe fracture emanating from a stress corrosion crack in the heat-affected zones of girth-welds in Type 304 stainless steel pipes was investigated. The J-resistance curve—tearing modulus parameter for the prediction of crack initiation, stable growth and fracture instability—was employed. To evaluate the analysis, a pipe fracture experiment was performed using a spring-loaded four-point bending system that simulated an 8.8-m (29-ft) long section of unsupported 102-mm- (4-in-) dia pipe. An initial through-wall crack of length equal to 104 mm (4.1 in.) was used. Fracture instability was predicted to occur between 15.2 and 22.1 mm (0.60 and 0.87 in.) of stable crack growth at each tip. In the actual experiment, the onset of fracture instability occurred beyond maximum load at an average stable crack growth of 11.7 to 19 mm (0.463 to 0.750 in.) at each tip.
Trial Application of the Draft Structural Design Criteria for Breeder Reactor Core Components to a Typical Blanket Assembly Duct
Authors: Sazawal V. K.
Published: November 2009

This paper presents the results of a comprehensive trial application of the draft structural design criteria for highly irradiated core components to a typical blanket assembly duct. The development of the criteria (proposed RDT F 9-7) is sponsored by the U.S. Department of Energy. The activity focuses on the evaluation of the criteria using a typical breeder reactor blanket assembly as a test case and is not intended for judging the adequacy of the component design. Pertinent design rules from the draft criteria are applied to the component to determine: (a) difficulties, if any, that may arise in interpretation and application of the criteria, and (b) adequacy of the criteria rules and analysis methods to address various potential failure mechanisms expected in the reactor core during service. Based on the trial application, various recommendations are made to promote further development of the criteria.
Effect of Tube Banks on Rarefaction Wave Propagation
Authors: Squarer D. , Manhardt A. E.
Published: November 2009

In a continuing effort to study the effect of steam generator feed line break on steam generator internals, a theoretical and experimental study has been undertaken. This paper summarizes results of a study whose goal is to check the effects of tube rows on rarefaction wave propagation generated by a sudden rupture. The effect of the tubes is presented in terms of measured pressures and strains with and without tubes. Ten rows of tubes are found to cause a transmission loss in the 1:10 steam generator scale model smaller than 689 kPa along the feed line centerline and have little effect away from the centerline, or on the pressure difference across the divider plate. Theoretical considerations include: estimating transmission losses in terms of tube bank geometry, wave length and frequency, and incident pulse; reflection from a free jet, and potential flow solution to the flow field near the pressure vessel-feed line interface.
Plastic Buckling of Various Shells
Authors: Bushnell D.
Published: November 2009

The phenomenon of plastic buckling is first illustrated by the behavior of a fairly thick cylindrical shell, which under axial compression deforms at first axisymmetrically and later nonaxisymmetrically. Plastic buckling encompasses two modes of behavior, nonlinear collapse at the maximum point in a load versus deflection curve and bifurcation buckling. Accurate prediction of critical loads corresponding to either mode in the plastic range requires a simultaneous accounting for moderately large deflections and nonlinear, irreversible, path-dependent material behavior. A thumbnail survey is given of plastic buckling which spans three areas: asymptotic analysis of postbifurcation behavior of perfect and imperfect simple structures, general nonlinear analysis of arbitrary structures, and nonlinear analysis for collapse and bifurcation buckling of shells and bodies of revolution. Comparisons between test and theory are presented for elastic-plastic buckling of axially compressed unstiffened and ring-stiffened cylindrical shells, internally pressurized torispherical and ellipsoidal pressure vessel heads, and pipes under combined external pressure and bending. The effect on buckling of fabrication processes such as cold forming and welding is discussed for the case of ring-stiffened cylindrical shells. Two examples are given of rather complex shell structures in which considerations of plastic buckling affect the design.
Stress Analysis and Stress Index Development for a Trunnion Pipe Support
Authors: Sadd M. H. , Avent R. R.
Published: November 2009

A finite element stress analysis is presented of a trunnion pipe anchor. The structure is analyzed for the case of internal pressure and various end moment loadings. Stress results were post-processed and decomposed into average and linear varying (through the wall thickness). These decomposed values were then interpreted within the ASME Boiler and Pressure Vessel Code to estimate primary and secondary stress indices. Several computer runs were made for a variety of structural sizes and empirical formulas were developed expressing the stress indices as a function of certain dimensionless ratios.
Dynamic Buckling of Inelastic Spherical Shells
Authors: Funk G. E. , Lee L. H. N.
Published: November 2009

The dynamic buckling behavior of a complete spherical shell made of a bilinear or work-hardening material and under a uniform external impulsive loading is investigated. A quasi-bifurcation theory and a minimum principle are employed to determine, respectively, the onset of the dynamic buckling process and the post-bifurcation nonlinear behavior. Numerical results are obtained for a number of elastic and elastic-plastic cases. The results indicate there is a softening effect in the plastic deviated stress-strain relationship which makes the spherical shell less stable. Furthermore, the higher order terms in stress and strain measures and the coupling of symmetric and asymmetric modes of motion cannot be neglected in the post-bifurcation analysis.
Stiffening Effects on Thin-Walled Piping Elbows of Adjacent Piping and Nozzle Constraints
Authors: Thomas K.
Published: November 2009

Elbows, attached to component nozzles or adjacent piping, experience a stiffening effect due to the restraint of ovalization provided by the nozzle or pipe. Using the thin-shell, finite difference program STAGSC, a numerical study of two elbows of different geometry with varying degrees of ovalization restraint was performed. Attention was confined to small displacement, elastic analysis of pure in-plane and out-of-plane bending. The analysis shows that in all cases there is a significant decrease in elbow flexibility due to the constraints. There is also a corresponding decrease in the circumferential stress index which is approximately proportional to the reduction in flexibility. These results indicate that a simple, rational basis could be developed for modifying elbow flexibility factors to allow for flange and nozzle stiffening in overall piping flexibility analysis. Original data are presented which relate elbow flexibility factors and stress indices to the degree of nozzle constraint for two elbow geometries.
The Effect of Induction Heating Stress Remedies on Existing Flaws in Pipes
Authors: Shadley J. R. , Merah N. , Rybicki E. F.
Published: November 2009

One method for reducing stress corrosion cracking problems called induction Heating for Stress Improvement (IHSI) has been successful in producing compressive residual stresses on the inside surface of welded pipes. During the time that the induction heating coil is turned on, however, the process causes tensile stresses at the inner wall, raising questions about the effect that the induced tensile stress field may have on existing flaws in the pipe. To provide a basis for comparing as-welded stress distributions with the stress distributions occurring during the IHSI process, stress intensity factors were computed for part-through, axisymmetric, circumferential cracks in pipes using linear elastic fracture mechanics analyses. Results for as-welded stress distributions agree with the field experience that most of the crack pipes in Boiling Water Reactor piping systems are smaller diameter pipes in the 4–12-in. (102–305-mm) range. Stress intensity factors in the smaller diameter pipes for the stresses during IHSI were comparable to those for the as-welded stresses. For the 26-in- (660-mm-) dia pipe, the large changes in the stress distributions during the IHSI process suggest the possibility of a net closing or opening of a flaw existing in the pipe prior to the heat treatment.