bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth of Buckling Instabilities During Radial Collapse of a
Ring
Authors: Duffey T. A. , Warnes R. H. , Greene J. M.
Published: June 2008

Conditions leading to the growth of initial imperfections for rings or long cylindrical shells subjected to initial uniform inward impulsive velocity loading are investigated. The work is motivated by a need to prevent buckling of rings during the contracting ring test, which is used to determine intermediate strain rate compressive stress-strain data. A previous analysis by Abrahamson is extended to include deceleration of the ring during inward motion; and the results of this deceleration are found to greatly influence the growth of imperfections (buckling). Qualitative comparisons with experimental data are presented.
Fatigue Crack Growth: A Case Study of Synthetic Tower Spectrum
Loading
Authors: Cheng J. , Qian J.
Published: June 2008

Hourly pressure variations were recorded during six years in two synthetic towers, giving a total of 105,000 readings. The readings were converted into a 15-block pressure amplitude spectrum of 12,655 cycles following standard methods employed in the aircraft and automotive industries. The spectrum was applied to center-cracked tension specimens and crack growth rates were measured. The results show that the crack growth rate data can be plotted conservatively against the range of the equivalent stress intensity factor calculated as a root-mean-cube value. Futhermore, it is shown that the 9704 cycles of lowest 1.9 MPa pressure amplitude caused 12 percent of the cumulative fatigue damage, whereas the 13 start-up and shut-down cycles of highest 15.2 MPa amplitude caused 8.2 percent of the damage.
Brittle and Ductile Creep Rupture Life Prediction of 1CrMoV Steel
Notched Thick Plates
Authors: Ando K. , Takeda Y. , Takezoe K.
Published: June 2008

An analytical prediction method of brittle and ductile creep rupture life of 1CrMoV steel notched thick plate is proposed. Rupture time is evaluated as a sum of crack initiation life ti and crack growth life tp. In the case of ductile creep at high stresses, ti is evaluated by the creep deformation criteria. In addition, in the case of brittle creep at low stresses, ti is evaluated by Kachanov’s damage mechanics theory. Materials constants in Kachanov’s theory can be determined by the relatively short-term creep rupture test of notched specimen, etc., according to the present method. Creep rupture test, interrupted creep test, and micro-structural observation, have been used, which can explain the variety of material behavior, i.e., notch weakening at low stresses and notch strengthening at high stresses. In addition, in this analysis the analytically estimated creep crack initiation life corresponds to the time to creep void initiation just inside the notch root.
A Simplified Method for Predicting Creep Collapse of a Tube Under
External Pressure
Authors: Nishiguchi I. , Kaji Y. , Ioka I. , Yamamura T. , Yamada Y.
Published: June 2008

A simplified method is proposed to predict the creep collapse behavior of a long tube subjected to external pressure. The shape of the cross section of a tube is assumed to be quasi-elliptical characterized by a single variable, often called as shape factor in the literature. The growth of the displacement field is represented by the change of shape factor which is governed by an ordinary differential equation. A general class of creep constitutive equations can be employed with an accompanying elasticity whose effect is crucial under higher external pressure. Plane strain condition is assumed. Nonlinearity of stress distribution through the wall of the tube is allowed according to the creep constitutive equation in general, while the strain distribution is assumed to be linear. The method is applied to the analyses of heat tubes, which are typical for heat exchangers of high-temperature gas-cooled reactors, and is compared with the computer solution by the finite element method based on a finite deformation theory, as well as solutions by other simplified methods.
The ASME Pressure Vessels and Piping Division—25 Years of Progress
Authors: Farr J. R.
Published: June 2008

1991 is the Silver Anniversary of the ASME Pressure Vessels and Piping Division. The PVP Division was formed 25 years ago to serve as a focal point for mechanical engineering as related to the pressure vessels and piping industry. Through the PVP Division’s extensive publications, conferences, short courses, and tutorial lectures, pressure vessel and piping technology and new development information has been disseminated throughout the world. This chronological essay of significant events and contributing people has been written for posterity to record the first 25 years of the Division. May the next 25 years bring equal or greater success to the ASME Pressure Vessels and Piping Division!
Strength Aspects of Safety and Life Extension of RBMK Reactors
Authors: Bougaenko S. E. , Rivkin E. Yu. , Rodchenkov B. S.
Published: June 2008

RBMK channel power reactors belong to the one-loop boiling water reactors with graphite as a moderator. Equipment, pipelines and core elements are the main components of the coolant recirculation circuit. Analysis in terms of fracture mechanics shows that the circuit elements conform to the “leak-before-break” criterion, with the pipelines and equipment keeping their availability during the whole design operation period. The core is a critical component for the circuit availability.
Service Properties of Reactor Structural Steels and Prediction of NPP Equipment Life With PWR-Type Reactors
Authors: Zvezdin Yu. I. , Shur D. M. , Popov A. A.
Published: June 2008

The results obtained from the experimental investigation of Cr-Ni-Mo-V and Mn-Ni-Mo-V steel service properties used in the USSR reactor building, as well as the static crack resistance KIC versus reference temperature dependence and Paris kinetic diagrams of fatigue crack growth rate in air and water of high parameters, are given.
Influence of Weld Factors on Creep-Rupture Cracking at Elevated Temperature
Authors: Dhalla A. K.
Published: June 2008

The purpose of this paper is to identify the weld effects which are of primary importance in elevated temperature design. A full-scale Fast Flux Test Facility (FFTF) Intermediate Heat Exchanger (IHX) was tested at Westinghouse to investigate weld effects at elevated temperature. The IHX was subjected to two and a half times the design pressure. In addition, one of the four welded nozzles of the IHX was subjected to 26 severe thermal downshock transients, which were interspersed with 156 hr of creep hold time at 1100°F (593°C). At the end of testing, creep rupture cracks were observed in the weldments at the nozzle to cylinder intersections, whether or not they experienced downshock transients. Detailed three-dimensional inelastic analyses were performed to investigate the effects of welding on the creep-rupture strength of weldments. The analyses suggest that the weldment material property variation contributed to creep-rupture cracking at high primary pressure loading. The weld metal and heat-affected zone had higher yield strength, but lower creep ductility compared to the nozzle base material. The analytical predictions and metallurgical observations suggest that the role of residual stresses on creep-rupture cracking is of secondary importance, and need not be numerically simulated in the elevated temperature design of weldments.
Seismic Evaluation of Systems and Components
Authors: Lin C.-W.
Published: June 2008

Analysis of systems and components for seismic loads has been under continuous development during the last decade. Unlike the early stages of development where the emphasis was on conservatism, the past decade has seen tremendous amount of growth in improved evaluation techniques, more realistic criteria, and better understanding in the dynamic behavior of systems and components under earthquake loads. Accuracy of the evaluation method and the effect of over conservatism on the reliability of the design during operating conditions have become the focus of attention. This has sparked renewed interest in revising many basic assumptions made in the early history of seismic analysis. This revision has also led to many new methods of evaluation and new design concepts. In this paper, developments in seismic evaluation during the last decade are reviewed. The objective is to provide a self-contained overview of the techniques, criteria, and procedures that have contributed to the state of the art development in the entire evaluation process leading to the design acceptability of systems and components.
Examination of Riser Clamps on High-Temperature Piping (Design Paper)
Authors: May G. H.
Published: June 2008

Pipe supports on high-temperature critical piping can fail due to unexpected high loading conditions, inadequate design, incorrect installation or operational errors. Riser clamps are particularly susceptible to failure because of their torsion and moment loading. Since likely failure locations are invariably hidden under insulation, a technique is described to determine when further investigation is warranted. Likely failure locations and types of recommended tests are also described.
Effect of Hydrostatic Retest on the Fatigue Behavior of a Steel Gas Cylinder
Authors: Bhuyan G. S. , Akhtar A. , Webster C. T. L.
Published: June 2008

Retardation effect of the hydrostatic test on the subsequent crack growth in an AISI 4130X steel gas cylinder has been predicted. The post-test retardation period depends upon the size of the crack; the smaller the crack size the larger the crack growth retardation period. The beneficial effect of the present recertification test, conducted at 5-yr interval at a pressure of 1.67 times the design service pressure, depends upon the number of pressure cycles incurred between retests.
Multishock Compactions of a Die-Contained Copper Powder Medium Analyzed by Improved Theory
Authors: Sano Yukio , Tokushima Koji , Inoue Tokujiro
Published: June 2008

In the present paper, the multishock compaction process of a die-contained copper powder medium supported by an elastic plug at one end and impacted by an elastic punch at the other end, is analyzed by means of an improved theory having the effect of elasticity of the punch and plug. The compactions computed first have a constant sum of lengths of the medium and plug S0*=110, a constant ratio of punch mass to powder mass filled in the die M*=20, and an initial punch velocity ν0=50m/s. The computations of the compactions for the medium with very short lengths and the plug with long lengths confirm the existence of the medium length Scr1* corresponding to the first critical plug-length found in the previous study, and support the compaction process and the final mean density ρmean*-initial medium length S* relation of the medium shorter than the length Scr1* which were inferred in the study. Furthermore, the effect of elastic waves in the punch and plug on the process of the medium longer than Scr1* are examined. There are one common factor and one significant different factor in the processes. Explicitly, the waves in the plug exert different influence on compaction processes of the medium with different lengths, whereas the waves in the punch have similar influence on the processes. The elastic waves in the plug and die wall friction cause the medium length Scr2* corresponding to the second critical plug-length inferred in the previous study. Moreover, the waves in the plug make the form of the computed relation curve more complicated than the inferred one. The computed curve has the lengths Scr3* and Scr4* at which the density has an extreme value, respectively. Approximate similarity conditions for the compactions with various values of S0* are given by two fixed parameters M* and ν0 in region S*(1/2)S0*. The computed ρmean*–S* and ρmean*–S*/S0* relations support these conditions. Furthermore, the computations of the compactions reveal that the waves in the punch, medium, and plug behave in similar manner during the processes, though they have different strengths.
Longitudinal Motion of a Thick Transversely Isotropic Hollow Cylinder
Authors: Tsai Y. M.
Published: June 2008

The propagation of a longitudinal harmonic wave in a transversely isotropic shell has been investigated in the development of ultrasonic techniques for thick hollow composite cylinders. The characteristic equation for satisfying the stress-fee inner and outer cylindrical boundaries has been obtained in an exact form in terms of the wavelength, the cylinder radii and the material constants. The phase velocity of the fundamental mode is calculated for a wide range of the wavelength for various cylinder radii for some typical sample materials. The shell wave speeds for the second mode of vibration are also presented. Comparisons are made between shell wave speeds and plate wave speeds. The spread of the wave speeds for the composite shells is shown to be much wider than that for an isotropic shell.
Membrane Analysis of Composite Reinforced Composite Spherical Shells
Authors: Boussouf D. M.
Published: June 2008

This paper presents a stress analysis of composite reinforced spherical shells with closed apex. The shell structure may be composed of an isotropic metal layer and a unidirectional composite layer. The analysis uses the load-sharing approach and assumes no shear transfer between layers. Analytical solutions for layered spherical structures which are subject to both mechanical and thermal loading are derived. Numerical results are presented. The difference in radii of the liner and the composite overwrap is taken into account.
Nonlinear Analysis of Transverse Shear Deformable Laminated Composite Cylindrical Shells—Part I: Derivation of Governing Equations
Authors: Soldatos K. P.
Published: June 2008

Based on the concept of an “intermediate” class of deformations, a theory suitable for the nonlinear static and dynamic analysis of transverse shear deformable circular and noncircular cylindrical shells, composed of an arbitrary number of linearly elastic monoclinic layers, is developed. The theory is capable of satisfying zero shear traction boundary conditions at the inner and outer shell surfaces. Upon assuming that the shell is subjected to a certain initial stress state and applying the highly nonlinear governing equations derived to the adjacent equilibrium criterion, a set of Love-type linearized equations is further derived. These latter equations are suitable for buckling and/or vibration analyses; in a companion paper, they are solved and used for the study of the influence of transverse shear deformation on the buckling loads of axially compressed cross-ply laminated circular and oval cylindrical shells.
Effectiveness of Wear Plate at the Saddle Support
Authors: Seng Ong Lin
Published: June 2008

A theory is presented to analyze the effectiveness of incorporating a wear plate at the saddle support of a cylindrical pressure vessel. The wear plate can be either welded to the vessel or of loose fitting. The theory is based on a contact stress formulation together with the use of a cylindrical shell bending theory for simply supported cylinder. The effectiveness of the wear plate in reducing the peak circumferential saddle-horn stress is quantified by definition of a stress reduction factor. Parametric data are carried out for the saddle angle of 120 deg. From the study, the optimum thickness of the wear plate for three different angular extensions, are obtained.
Tube-Tubesheet Joint: A Proposed Equation for the Equivalent Sleeve Diameter Used in the Single-Tube Model
Authors: Chaaban A. , Ma H. , Bazergui A.
Published: June 2008

The tube-to-tubesheet joint analysis can be greatly simplified by considering a single tube surrounded by an annular sleeve representing the tubesheet. One of the problems is how to choose the appropriate outer diameter of the annular sleeve model. In this paper, the nonlinear finite element method and some other analytical solutions were used to investigate this problem. Due to the many dimension, fabrication, and material-related parameters, the orthogonal design method was used to minimize the number of calculations while providing an accurate understanding of the influence of all involved parameters. Based on the results, empirical equations for determining the equivalent external sleeve diameter that can be used in the single-tube model and for approximating the residual contact pressure, are proposed.
Transformation Plasticity and Residual Stresses in Single-Pass Repair Welds
Authors: Oddy A. S. , Goldak J. A. , McDill J. M. J.
Published: June 2008

Prediction of the residual stresses caused by welding is important when post-weld stress relief is not feasible. Phase changes and transformation plasticity have a significant effect on the residual stresses generated by welding and heat-treatment of some alloys. Transformation plasticity occurs when the stresses generated by the transformation of individual grains interact with the macroscopic stress state to produce plastic strains. Heuristic methods requiring empirical constants have been used in the past. A method based on the fundamental laws of plasticity and basic material properties is proposed to incorporate transformation plasticity in a finite element program. The transformation plasticity which occurs depends on the stress state. During any increment the stress state can change substantially. If the step size is too large, the analysis may become unstable. A method which allows larger steps while eliminating the instability and improving the convergence is presented. A three-dimensional (3D) analysis of a short longitudinal pipe weld in a typical pressure vessel steel is shown. The significance of this phenomenon in welds is demonstrated by comparing the residual stress states predicted with and without transformation plasticity.
A Method for Suppression of Pressure Pulses in Fluid-Filled Piping—Part I: Theoretical Analysis
Authors: Shin Y. W. , Wiedermann A. H.
Published: June 2008

A simple, nondestructive method to suppress pressure pulses in fluid-filled piping is theoretically analyzed, and the result provides the basis needed for design and evaluation of a pressure-pulse suppression device based on the proposed theory. The method is based on forming of fluid jets in the event of a pressure surge, such that the pulse height and the energy of the pulse are reduced. The results for pressure pulses in the range of practical interest show that a substantial reduction in the pulse height can be attained, with accompanying reduction of the pulse remaining in the system. The analysis also reveals that a certain amount of trade-off exists in the design of the suppression device; a certain level of pulse energy remaining in the system must be accepted in order to keep the pulse height below a certain level, and vice versa.
Technical Basis for a Revised Fatigue Crack Growth Rate Reference Curve for Ferritic Steels in Air
Authors: Eason E. D. , Gilman J. D. , Jones D. P. , Andrew S. P.
Published: June 2008

Appendix A of the ASME Boiler and Pressure Vessel Code, Section XI, contains a reference curve for fatigue crack growth rates in air in ferritic steels that was established in 1973 with a limited amount of data. In the past 15 years, many additional data have been collected that do not agree with the trend exhibited by this original reference curve. In light of these new data, an analysis has been undertaken to re-evaluate the fatigue crack growth rate curve in the Code. As a result, an improved reference curve that considers the dependence of crack growth rate on R-ratio and ΔK has been developed. This paper presents the technical basis for the improved curve, some details on the analysis used to determine it, and comparison of the current Section XI Code with the available ferritic steel database and the new reference curve. The format proposed for adoption of the new reference curve is presented, with comments on the practical effect of the proposed change.
An Evaluation of Approximate Pipe Bend Equations
Authors: Whatham J. F.
Published: June 2008

The findings from approximate equations for the elastic analysis of elliptical pipe bends under in-plane bending or pressurization are tested against an exact thin shell analysis. Although stresses are not compared, the simple equations give, with surprising accuracy, the flexibility of pipe bends and the bending moment in a pressurized torus.
Fluid-Structure Dynamics With a Modal Hybrid Method
Authors: Brenneman B. , Au-Yang M. K.
Published: June 2008

Large structures in nuclear power plants are often separated by very thin fluid-filled cavities. For example, core support structures, thermal shields, and reactor vessels are usually large concentric cylindrical shells with annuli between them as small as 2 percent of the shell diameter. Such thin cavities cause the structures to be very strongly coupled, and such coupling must be accurately modeled to predict the dynamic responses of new designs to turbulence, pump acoustic loading, loss-of-coolant accidents, and seismic events. This paper summarizes a very versatile and efficient method of solving these problems with small personal computers. Among other things, this method uses component modal synthesis with the hybrid approach, and the solution of the resulting unsymmetric eigenvalue problem for the coupled vibration modes. System responses are then found in terms of “right” and “left” eigenvectors. Comparisons with test results are also presented.
Flaw Assessment Procedure for High-Temperature Reactor Components
Authors: Ainsworth R. A. , Ruggles M. B. , Takahashi Y.
Published: June 2008

An interim high-temperature flaw assessment procedure is described. This is a result of a collaborative effort between Electric Power Research Institute in the US, Central Research Institute of Electric Power Industry in Japan, and Nuclear Electric plc in the UK. The procedure addresses pre-existing defects subject to creep-fatigue loading conditions. Laws employed to calculate the crack growth per cycle are defined in terms of fracture mechanics parameters and constants related to the component material. The crack growth laws may be integrated to calculate the remaining life of a component or to predict the amount of crack extension in a given period. Fatigue and creep crack growth per cycle are calculated separately, and the total crack extension is taken as the simple sum of the two contributions. An interaction between the two propagation modes is accounted for in the material properties in the separate calculations. In producing the procedure, limitations of the approach have been identified. Some of these limitations are to be addressed in an extension of the current collaborative program.
Modeling of Notch Effects on Stress Corrosion Cracking
Authors: Maiya P. S. , Pai B. K.
Published: June 2008

The intergranular stress corrosion cracking (IGSCC) of sensitized Type 304 stainless steel (SS) has been investigated by slow strain rate tests (SSRTs) in 289°C water containing sulfate impurity. Both smooth and circumferentially notched specimens were used to assess the effects of strain concentrations on stress corrosion cracking (SCC). Experiments were conducted over a range of nominal strain rates of 10−5 to 10−7 s−1. A comparison of the results observed for the smooth and notched specimens suggests that the estimated growth rates of small cracks in SSRT specimen geometry is influenced by the presence of strain concentrations. In particular, the average crack growth rates estimated from tests performed at the same nominal strain rate are observed to increase with the notch depth, and power-law relationships exist between strain rate and SCC parameters such as failure time and crack growth rate. The strain concentration factors at the notch roots of Type 304 specimens subjected to axial load have been estimated by finite-element elastic-plastic stress analyses, as well as by Neuber’s rule. The nominal and crack-tip strain rate effects on SCC in both smooth and notched specimens are interpreted in terms of a model based on elastic-plastic fracture mechanics and film-rupture mechanisms that invoke diffusion-controlled SCC growth kinetics.
The Elastic-Plastic Analysis of Tubes—III: Shakedown Analysis
Authors: Jiang W.
Published: June 2008

This paper presents an investigation of the shakedown behavior of tubes subjected to cyclic centrifugal force and temperature, and sustained internal and external pressures. It is found that the steady states can always be attained as a result of the kinematic hardening. Then, when shakedown occurs, the stresses and strains will cycle between the cooling state and the heating state. The steady-state solutions for the cases of elastic shakedown and reversed plasticity are discussed and given in this paper.
Numerical Simulation of the Severe Cold Bending of Thick Steel Plates
Authors: Soudki K. A. , Sansalone M. , Ingraffea A. R. , Vossoughi H.
Published: June 2008

This paper presents results of a finite element study of the severe cold bending of thick, high-strength steel plates using an explicit, two-dimensional, finite element code. A parametric study was performed to study the effect of contact surface conditions and the plate’s material model on the behavior of the plate during cold bending. The results of these numerical studies were compared with experimental data measured by Weng in 1984 and analytical equations proposed by Dat in 1980. It was found that the model with isotropic hardening and no friction showed the best agreement with the experimental and analytical results.
Residual Stresses in Tube-Tubesheet Joints With Grooves
Authors: Updike D. P. , Kalnins A. , Caldwell S. M.
Published: June 2008

Hydraulic expansion of a tube into a grooved tubesheet is modeled as an elastic-plastic process. A special shell theory is used to obtain the tube residual stresses in the vicinity of the grooves. It is found that the maximum tensile residual stresses occur at the inside surface of the tube, but their magnitudes are lower than those in the transition region. The results also suggest the use of a higher hydraulic forming pressure for grooved joints than for ungrooved joints.
Heavy-Section Steel Technology Program: Fracture Issues (Survey Paper)
Authors: Pennell W. E.
Published: June 2008

Large-scale fracture mechanics tests have resulted in the identification of a number of fracture technology issues. Identification of additional issues has come from the reactor vessel materials irradiation test program and from reactor operating experience. This paper provides a review of fracture issues with an emphasis on their potential impact on a reactor vessel pressurized thermal shock (PTS) analysis. Mixed mode crack propagation emerges as a major issue, due in large measure to the poor performance of existing models for the prediction of ductile tearing. Rectification of ductile tearing technology deficiencies may require extending the technology to include a more complete treatment of stress state and loading history effects. The effect of cladding on vessel fracture remains uncertain to the point that it is not possible to determine at this time if the net effect will be positive or negative. Enhanced fracture toughness for shallow flaws has been demonstrated for low-strength structural steels. Demonstration of a similar effect in reactor pressure vessel steels could have a significant beneficial effect on the probabilistic analysis of reactor vessel fracture. Further development of existing fracture mechanics models and concepts is required to meet the special requirements for fracture evaluation of circumferential flaws in the welds of ring-forged vessels. Fracture technology advances required to address the issues discussed in this paper are the major objective for the ongoing Heavy Section Steel Technology (HSST) program at ORNL.
Numerical Modeling of Full-Scale Pipe Rupture Tests
Authors: Emery A. F. , Chao Y. H. , Kobayashi A. S. , Love W. J.
Published: June 2008

The split-ring model is used to simulate full-scale pipe rupture experiments. Using experimentally measured pressures and pipe material characteristics, the model correctly predicts crack extension histories and depressurization rates. The model is also successful in predicting the occurrence of crack arrest and the arrest length.
On the Use of the Hole-Drilling Technique for Residual Stress Measurements in Thin Plates
Authors: Hampton R. W. , Nelson D. V.
Published: June 2008

The strain gage blind hole-drilling technique may be used to determine residual stresses at and below the surface of components. In this paper, the hole-drilling analysis methodology for thick plates is reviewed, and experimental data are used to evaluate the methodology and to assess its applicability to thin plates. Data on the effects of gage pattern, surface preparation, hole spacing, hole eccentricity, and stress level are also presented.
Simplified Nonlinear Ratchet Model for Dynamic Analysis of Pressure
Components
Authors: Lazzeri L.
Published: June 2008

A method for the analysis of components under the combined effect of pressure and externally applied dynamic generalized forces is described; comparison with tests is provided. It is concluded that neglecting the effect of ductility in the computation of the response leads to unrealistic results. A method of analysis is presented.
Multiple Stability Boundaries of Tubes in a Normal Triangular Cylinder Array
Authors: Andjelic´ M. , Austermann R. , Popp K.
Published: June 2008

This paper reports on experiments using a normal triangular cylinder array with a pitch-to-diameter ratio of 1.25 in air-cross-flow. The array consists of 18 tubes, in which 9 freely suspended tubes are linear iso-viscoelastically mounted. This unique tube mounting enables the linear damping of 9 cylinders (4, 3 and 2 cylinders in the first, second, and third cylinder row, respectively) to be continuously varied over a wide mass-damping parameter range of 10 < μδ/(ρd2) < 80. The experimentally observed phenomenon are correlated with nonlinear vibration theory terminology in order to improve the characterization of the excitation mechanisms. Experimental results are presented showing three stability boundaries for one flexibly mounted tube in an otherwise fixed array, as was predicted by Lever and Weaver’s “wavy wall channel model.” Flow visualization, for that arrangement, shows that their model describes the actual fluid flow past the tube reasonably well. Furthermore, multiple stability boundaries for small groups of flexibly mounted cylinders in an otherwise fixed cylinder array have, for the first time, been measured.
Analysis of Composite Plates Containing Cracks
Authors: Kwon Y. W.
Published: June 2008

Effect of microcracks, such as local matrix crack and fiber breakage, on a macroscale crack in a unidirectional composite plate was studied for various fiber volume fractions, as well as different material properties of fiber and matrix materials. A finite element analysis was performed for this study. It showed that microcracks, located near a macroscale crack tip, resulted in a significant increase of stress intensity factor at the crack tip.
A Probabilistic Approach to the Evaluation of the PTS Issue
Authors: Cheverton R. D. , Selby D. L.
Published: June 2008

An integrated probabilistic approach for the evaluation of the pressurized-thermal-shock (PTS) issue was developed at the Oak Ridge National Laboratory (ORNL) at the request of the Nuclear Regulatory Commission (NRC). The purpose was to provide a method for identifying dominant plant design and operating features, evaluating possible remedial measures and the validity of the NRC PTS screening criteria, and to provide an additional tool for estimating vessel life expectancy. The approach was to be integrated in the sense that it would include the postulation of transients; estimates of their frequencies of occurrence; systems analyses to obtain the corresponding primary-system pressure, downcomer coolant temperature, and fluid-film heat-transfer coefficient adjacent to the vessel wall; and a probabilistic fracture-mechanics analysis using the latter data as input. A summation of the products of frequency of transient and conditional probability of failure for all postulated transients provides an estimate of frequency of vessel failure. In the process of developing the integrated-pressurized-thermal-shock (IPTS) methodology, three specific-plant analyses were conducted. The results indicate that the NRC screening criteria may not be appropriate for all U.S. pressurized-water-reactor (PWR) plants; that is, for some PWRs, the calculated mean frequency of vessel failure corresponding to the screening criteria may be greater than the “primary-acceptance-criterion” value in Regulatory Guide 1.154. A recent review of the ORNL IPTS study, which was completed in 1985, indicates that there are a number of areas in which the methodology can and should be updated, but it is not clear whether the update will increase or decrease the calculated probabilities.
Nondestructive Measurement of Welding Residual Stresses by Acousto-Elastic Technique and Prediction of Fatigue Crack Growth
Authors: Kobayashi H. , Arai Y. , Ohsawa Y. , Nakamura H. , Todoroki A.
Published: June 2008

Nondestructive measurements of residual stresses were successfully attempted by the acoustoelastic technique on butt-welded joints of a carbon steel for nuclear piping. Usefulness of the technique considering the effect of the material anisotropy is emphasized. Based on the measured residual stresses, predictions of the fatigue crack growth were done using the superposition technique. It is shown that predictions agree well with experiments. The effect of the accuracy in residual stress measurements on the predictions is also included.
1992 CALVIN RICE LECTURE: Some Curiosity-Driven Research in Fluid
Structure Interactions and Its Current Applications
Authors: Pai¨doussis M. P.
Published: June 2008

This lecture has a dual purpose: (i) to present, in outline, the research on a couple of interesting topics in fluid-structure interaction; and (ii) to show that, although this research was undertaken with little or no practical application in mind, unexpected uses and applications materialized ten or twenty years subsequently. The two topics of research chosen are (a) stability of pipes conveying fluid, and (b) stability of cylinders in axial flow. The applications and uses range from a marine propulsion system, to research on emphysema, to understanding and modeling of flow-induced vibration and leakage-flow-induced instabilities in power-generating equipment, and to the dynamics of deep-water risers.
Assessment of an Improved Multiaxial Strength Theory Based on Creep-Rupture Data for Type 316 Stainless Steel
Authors: Huddleston R. L.
Published: June 2008

A new multiaxial strength theory incorporating three independent stress parameters was developed and reported by the author in 1984. It was formally incorporated into ASME Code Case N47-29 in 1990. In the earlier paper, the new model was shown to provide significantly more accurate stress-rupture life predictions than the classical theories of von Mises, Tresca, and Rankine, for type 304 stainless steel tested at 593°C under different biaxial stress states. Further assessments for other alloys are showing similar results. The current paper provides additional results for type 316 stainless steel specimens tested at 600°C under tension-tension and tension-compression stress states and shows 2–3 orders of magnitude reduction in the scatter in predicted versus observed lives. A key feature of the new theory, which incorporates the maximum deviatoric stress, the first invariant of the stress tensor, and the second invariant of the deviatoric stress tensor, is its ability to distinguish between life under tensile versus compressive stress states.
Fracture Toughness of Aged Stainless Steel Primary Piping Welds Evaluated by Multiple and Single-Specimen Methods
Authors: Huang F. H.
Published: June 2008

Fracture toughness testing was conducted on compact tension specimens cut from the Fast Flux Test Facility primary piping materials of 16-8-2 and 308 stainless steel welds aged at 427 and 482°C for 20,000 and 50,000 hr. The ductile fracture behavior of the materials was characterized at 205, 427, and 482°C using multiple and electric-potential single-specimen techniques. Electric-potential data were used to caculate crack extensions via an electric-potential calibration equation for the construction of J-R curves. Results demonstrate that the critical fracture-toughness values are in good agreement with those from the multiple-specimen method. Results showed that 20,000-hr aging caused more than 35 percent degradation in fracture resistance, and 50,000-hr aging resulted in a slight increase in Jc for 16-8-2 stainless steel welds. It was found that the fracture toughness levels of the primary piping after long-term aging were high and adequate at the aging temperatures and that fuel handling temperature, nonductile fracture was not expected to occur in these materials.
Improving Toughness of Electron Beam Welds of Heavy Mn-Mo-Ni Steel Plates for Pressure Vessels
Authors: Tomita Y. , Tanabe K. , Koyama K.
Published: June 2008

Electron beam welding melts and solidifies steel plate without using any welding material, unlike the conventional welding. Therefore, the toughness at the weld metal can decrease, depending on the chemical composition of the steel plate. Toughness at the electron beam weld can be increased by turning the microstructure from upper bainite into lower bainite and making the effective grain size finer. The microstructure can be controlled by the addition of alloy elements and optimization of impurity elements. In case the chemical compositions cannot be varied, largely because of the specification for their ranges, and the weld metal microstructure remains as upper bainite even after the application of microstructure control, methods to improve the toughness of electron beam weld itself, regardless of steel grades, becomes necessary. Phenomena peculiar to the electron beam weld are segregation during solidification and intergranular segregation over the dendrite surface. The fracture initiation is accelerated by the microcracks caused by the segregations during solidification. The fracture propagation is promoted by intergranular cracking caused by the intergranular segregation. By reducing these segregations, the fracture initiation and propagation are restrained and toughness increases despite the upper bainite microstructure. This can be achieved by the higher purification of steel. Through the foregoing investigations, ASTM A533 Type B Class 2 steel plate of 100 mm in thickness for electron beam welds has been developed for pressure vessels. Various welding tests as pressure vessels have been conducted, and it becomes clear that the developed steel plate has excellent toughness at the weld superior to those obtainable by conventional welding. The use of this steel greatly reduces the welding period compared to the conventional welding method.
Integral Hydro-Bulge Forming of Single and Multi-Layered Spherical Pressure Vessels
Authors: Hashemi J. , Rasty J. , Li S. , Tseng A. A.
Published: June 2008

The recently developed integral hydro-bulge forming (IHBF) process was utilized in the manufacturing of single and multi-layered spherical pressure and storage vessels. Single-layered spherical vessels of 1.6-mm thickness and diameters of 316.5, 634.1, and 953.2 mm were manufactured. As an alternative means of manufacturing thick-walled spherical pressure vessels, the IHBF procedure was modified and used informing double-layered composite pressure vessels with an effective thickness of 15 mm. The results showed that the modified IHBF process may successfully be applied in the manufacturing of multi-layered spherical vessels of various thicknesses and diameters. In this paper, the conventional and modified IHBF procedure will be outlined and the experimental results and analysis will be presented. Finally, areas where further work is needed are identified.
Passive Vibration Control Scheme Using Circular Viscoelastic Waveguide Absorbers
Authors: Shin Y. S. , Watson S. J. , Kim K. S.
Published: June 2008

A waveguide absorber is a device mounted on a vibrating structure at the selected points to transfer energy from the structure to the device which dampens the energy. The waveguide absorbers reported here are made of viscoelastic material which absorbs vibration energy and dissipates it in the form of heat. The novelty of this approach to damping is the simplicity of application and the effectiveness in the broadband frequency range with relatively less material. In this study, the impedances of the circular viscoelastic waveguide absorbers were evaluated experimentally at different temperatures and the results were compared with those of prediction. The application of the waveguide absorbers in the most effective manner to maximize damping of the structure is also studied. The impedance matching techniques were studied to minimize the vibration amplitude of the structure.
Static and Dynamic Buckling of a Fiber Embedded in a Matrix With Interface Debonding
Authors: Kwon Y. W. , Serttunc M.
Published: June 2008

Analyses were performed for static and dynamic buckling of a continuous fiber embedded in a matrix in order to determine effects of interfacial debonding on the critical buckling load and the domain of instability. A beam on elastic foundation model was used for the study. The study showed that a local interfacial debonding between a fiber and a surrounding matrix resulted in an increase of the wavelength of the buckling mode. An increase of the wavelength yielded a decrease of the static buckling load and lowered the dynamic instability domain. In general, the effect of a partial or complete interfacial debonding on the domain of dynamic instability was more significant than its effect on the static buckling load. For dynamic buckling of a fiber, a local debonding of size 10 to 20 percent of the fiber length had the most important influence on the domains of dynamic instability regardless of the location of debonding and the boundary conditions of the fiber. For static buckling, the location of a local debonding was critical to a free, simply supported fiber, but not to a fiber with both ends simply supported.
The Stress Analysis of a Cylinder With a Partition Plate Subjected to Internal Pressure
Authors: Fan Degui
Published: June 2008

This paper presents a method to calculate stresses of a cylinder with a partition plate, whose equations for determining bending stresses of a cylinder and its partition plate are different (less conservative) from those in ASME Boiler and Pressure Vessel Code, Section VIII, Division 1. The paper contains: 1) the derivation of equations for calculating bending stresses of a cylinder and its partition plate; 2) the comparisons between the method in ASME Code VIII-1 and the author’s method, and commentary on the equations for determining bending stresses of a cylinder and its partition plate in ASME Code VIII-1. Also, the recommendation to modify the equations for determining bending stresses of a cylinder and its partition plate in ASME Code VIII-1 has been put forward.
Use of Fundamental Modeling of Environmental Cracking for Improved Design and Lifetime Evaluation
Authors: Andresen P. L. , Ford F. P.
Published: June 2008

This manuscript reviews an approach for improved design and lifetime evaluation for environmental cracking based on fundamental modeling of the underlying, operative processes in crack advance. In outlining this approach and its application in energy industries, the requirements for a life prediction methodology will be highlighted and the shortcomings of the existing design and lifetime evaluation codes will be discussed. Examples will be given of its development and application in a variety of cracking systems, such as environmental cracking of stainless steels and nickel alloys in hot water, and irradiation-assisted stress corrosion cracking.
Contact Between Vessel Shell and Welded Pad in Nozzle Reinforcement
Authors: Chen H. , Chao Y.-J.
Published: June 2008

In the thin shell analysis of welded pad reinforced nozzles in pressure vessels, no contact between pad and vessel is often assumed. The significance of this contact force to the stress distribution in the structure is little known. In this paper, stress results from the finite element analysis, which includes the contact force between the pad and the vessel, are reported. A comparison of the finite element results with those from thin shell analysis and experiments shows that the finite element method with contact assumption yields improved theoretical prediction for the stress distribution. The effect of both the gap and friction between the pad and the vessel are also investigated.
Experimental Studies on a Nonlinear Hydroelastic Vibration of a Clamped Cylindrical Tank Partially Filled With Liquid
Authors: Chiba M.
Published: June 2008

Experimental studies have been carried out on the nonlinear hydroelastic vibrations of a clamped circular cylindrical tank with a flexible wall and a rigid bottom. In the studies, two test cylinders, made of polyester, with radius R = 240 mm, thickness h = 0.254 mm, and length L = 480 and 160 mm (L/R = 2.0 and 2/3), respectively, were used. The tank is fully or partially filled with water having a free surface. The nonlinearity of the response of the flexible wall when the wall of the tank is harmonically excited by points was investigated, with varying liquid height. It was found that the degree of the nonlinearity depends on the vibration mode, i.e., a circumferential wave number and an axial wave number of the shell, on the length of the tank, as well as on the height of the liquid contained in it. The results obtained here were compared with the experimental results of a cantilevered tank, which was previously carried out. The influence of a thin film floating on the free surface upon the bulging-type responses, in which shell wall response is predominant, was also examined. On the free surface, sub-harmonic response with order 1/2 was observed when the amplitude of the shell wall became large.
An Experimental Study of Assessment of Weld Quality on Fatigue Reliability Analysis of a Nuclear Pressure Vessel
Authors: Dai Shu-Ho
Published: June 2008

The steam generator in a PWR primary coolant system is one of the pieces of equipment made in China for the Qinshan nuclear power plant, Zhejiang. It is a crucial unit belonging to the category of nuclear pressure vessel. The purpose of this research work is to carry out an examination of the weld quality of the steam generator under fatigue loading and to assess its reliability by using experimental results of a fatigue test of the nuclear pressure vessel steel S-271 (Chinese Standard) and of qualified tests of welded seams of a simulated prototype of the bottom closure head of the steam generator. A guarantee of weld quality is proposed as the quality assurance of safety for the China National Nuclear Safety Supervision Bureau. The results of the reliability analysis reported in this work can be taken as supplementary material for a Probabilistic Risk Assessment (PRA) of the Qinshan nuclear power plant [1, 2]. According to the requirement of Provision II-1500 CYCLIC TESTING, ASME Boiler and Pressure Vessel Code, Section III, Rules for Construction of Nuclear Power Plant Components [13], a simulated prototype of the bottom closure head of the steam generator was made in this work for the qualified tests. Qualified tests with small sample size present a problem which is difficult to solve in reliability analysis, and are therefore of interest. Here, we offer proposals attempting to solve this problem.