bluuebunny/crossref_metadata_2025 huggingface dataset:
Technical Basis for Revised Reference Crack Growth Rate Curves for Pressure Boundary Steels in LWR Environment
Authors: Bamford W. H.
Published: November 2009

Reference fatigue crack growth rate curves have been contained in Appendix A of Section XI since its inception. The curves have been designed to be applicable to carbon and low alloy pressure vessel steels exposed to either air or light water reactor coolant environments. Data obtained over the past several years have shown a different behavior of these steels in the LWR environment than that predicted by the present reference curve. A revised set of reference curves have been formulated, incorporating a new curve shape as well as a dependency of growth rate on R ratio (minimum load/maximum load). This article provides the background and justification for such a revision, details the methodology used to develop the revised curves, and includes an evaluation of the adequacy and impact of the revised curves as compared with the single curve which they replace.
Computation of Seismic Response from Higher Frequency Modes
Authors: Vashi K. M.
Published: November 2009

A general procedure is presented for a more accurate, rapid and economical computation of response from higher frequency modes, when the modal superposition time history or response spectra method is used for dynamic analysis of structures subject to uniform, translational seismic excitation. The procedure utilizes special amplification characteristics of earthquake loading for frequencies not less than a certain assigned value and certain properties of structural modal characteristics. The upper bound for the assigned value of frequency is usually 33 cycles/s. This procedure requires computation of only those frequencies that are lower than the assigned value, and other modal properties associated with these lower frequencies. For rigid structures (i.e., structures with frequencies not less than the assigned value), this procedure reduces itself down to the familiar static analysis.
Thoughts on a Code of Practice for Forged High-Pressure Vessels of Monobloc Design
Authors: Ford H. , Watson E. H. , Crossland B.
Published: November 2009

The use and operational experience of forged high-pressure monobloc vessels is reviewed. It is noted that such vessels fall mainly into two categories: firstly those like stirred autoclaves for use in the continuous polyethylene process which are subjected to at the most two or three thousand cycles of pressure in a lifetime; and secondly, those such as isostatic compaction vessels which may be subjected to more than a hundred thousand cycles of pressure. It is concluded that the design procedures for one category are not sufficient for the other. Review of the performance of polyethylene autoclaves suggest that the design procedures which are based on well-established fundamental principles are more than adequate to ensure a safe design. With isostatic compaction vessels there is the added requirement to design against fatigue, and in particular to ensure adequate strength in the transition region between the threaded portion of the bore required for the screwed plug and the main bore, as it is mainly in this region that calamitous failures have been initiated. Some thoughts on some of the requirements for a code of practice for forged high-pressure vessels are put forward.
Pressure Transient Analysis of Elbow-Pipe Experiments Using the PTA-2 Computer Code
Authors: Youngdahl C. K. , Kot C. A. , Valentin R. A.
Published: November 2009

Severe hydraulic transients may be produced in the intermediate heat transport system of a liquid-metal-cooled breeder reactor by a sodium/water reaction in a failed steam generator. The PTA-2 computer code has been developed to analyze these transients, including the effects of plastic deformation of the piping and cavitation on pulse propagation. Comparisons are shown between PTA-2 predictions and the results of two experiments performed at Stanford Research Institute. Piping was plastically deformed by a pressure pulse traversing the experimental system, and the resulting rarefaction waves caused cavitation to occur. Excellent agreement between computation and experiment was obtained for dynamic strain and pressure distributions and the location and duration of the cavitation. The effect of elbow curvature on pulse propagation was found to be masked by pipe plasticity effects.
Stress Analysis of O.D. Notched Thick-Walled Cylinders Subjected to Internal Pressure or Thermal Loads
Authors: Kapp J. A. , Pflegl G. A.
Published: November 2009

Finite element stress analysis has been performed to determine the effects of two O.D. notch configurations in a cylinder subjected to internal pressure, or containing autofrettage residual stress. The effects on the residual stresses were determined by simulating these stresses with equivilent temperature loads. The results show that the deeper of the two notch cofigurations is far more severe resulting in a maximum stress concentration factor of 6.6. The shallower notch has a maximum stress concentration factor of 3.7. An additional result is that by introducing notches in autofrettaged cylinders a significant amount of the residual stresses are relieved which indicates that smaller applied pressures can be applied before yielding occurs. The results also show that the possibility of O.D. initiated fatigue failure is greatly increased.
Test of Thick Vessel with a Flaw in Residual Stress Field
Authors: Bryan R. H. , Holz P. P. , Iskander S. K. , Merkle J. G. , Whitman G. D.
Published: November 2009

A 152-mm-thick cylindrical test vessel fabricated of A533, grade B, class 1 steel, was pressurized to failure at −23°C. The vessel contained a fatigue-sharpened notch adjacent to a half-bead weld repair that had not been stress relieved. Residual stresses and fracture toughnesses were determined before the pressure test by measurements on a prototypic weld, and fracture predictions were made by linear elastic fracture analysis. Predictions agreed well with test results, demonstrating the important influence of high residual stresses on fracture behavior.
A Computational Method for Free Surface Hydrodynamics
Authors: Hirt C. W. , Nichols B. D.
Published: November 2009

There are numerous flow phenomena in pressure vessel and piping systems that involve the dynamics of free fluid surfaces. For example, fluid interfaces must be considered during the draining or filling of tanks, in the formation and collapse of vapor bubbles, and in seismically shaken vessels that are partially filled. To aid in the analysis of these types of flow phenomena, a new technique has been developed for the computation of complicated free-surface motions. This technique is based on the concept of a local average volume of fluid (VOF) and is embodied in a computer program for two-dimensional, transient fluid flow called SOLA-VOF. The basic approach used in the VOF technique is briefly described, and compared to other free-surface methods. Specific capabilities of the SOLA-VOF program are illustrated by generic examples of bubble growth and collapse, flows of immiscible fluid mixtures, and the confinement of spilled liquids.
A Structural Priority Approach to Fluid-Structure Interaction Problems
Authors: Au-Yang M. K. , Galford J. E.
Published: November 2009

In a large class of dynamic problems occurring in nuclear reactor safety analysis, the forcing function is derived from the fluid enclosed within the structure itself. Since the structural displacement depends on the fluid pressure, which in turn depends on the structural boundaries, a rigorous approach to this class of problems involves simultaneous solution of the coupled fluid mechanics and structural dynamics equations with the structural response and the fluid pressure as unknowns. Such an approach requires that the computer codes used to derive the forcing function and to analyze the structural response be radically modified or even abandoned. This paper offers an alternate approach to the foregoing problems. It is shown that for this kind of problem, the effect of fluid-structure interaction can be accounted for by a fluid mass matrix, which can be computed by the series expansion method. The advantage of this approach is that neither the computer code used to calculate the forcing function nor the ones for structural dynamics analysis need be modified. In fact, once the proper fluid mass matrix is computed, the problem can be solved by ordinary methods of structural dynamic analysis. Furthermore, since the fluid mass matrix is computed by a series expansion method, interfacing with a finite-element structural analysis computer code is relatively simple. On the other hand, the technique is restricted to small structural displacement with cylindrically symmetric fluid-structure boundaries. In addition, the fluid must be single phase.
A Sensitivity Study on Numerical Analysis of Dynamic Girth Crack Propagation
Authors: Kobayashi A. S. , Emery A. F. , Love W. J. , Jain A.
Published: November 2009

Dynamic motion of pre-existing girth crack in an axially stressed, 18-in-dia 316 stainless steel pipe in the presence of large-scale yielding was analyzed by a finite difference shell code. A critical crack tip opening angle (CTOA) was used as a dynamic fracture criterion and the sensitivities of dynamic crack propagation to differences in CTOA, finite differences mesh sizes, initial crack sizes and initial crack bluntnesses, were analyzed numerically. Hold-off times for the onset of dynamic crack propagation nearly doubled and tripled, while terminal crack velocities decreased about 22 percent and 47percent when the CTOA was increased from 0.10 to 0.19 and to 0.30, respectively. Doubling of the axial length of the initial crack length and an overdriving condition simulated by a larger CTOA did not change the terminal crack velocity.
Added Mass and Hydrodynamic Damping of Perforated Plates Vibrating in Water
Authors: De Santo D. F.
Published: November 2009

Experiments are described in which the fluid dynamic forces acting on perforated plates vibrating in water were measured. The test results are expressed in terms of added mass and hydrodynamic damping. Dimensionless formulas are presented which give accurate values for the added mass of the plates tested and which yield satisfactorily conservative lower bounds for the hydrodynamic damping force in both the linear and nonlinear (large-amplitude) damping range. The formulas for added mass and for low-amplitude damping apply to plates of any thickness that have any uniform square pattern of circular perforations. All of the results are general in that fluid density, viscosity, vibration amplitude, and frequency are all free parameters.
A Three-Dimensional Geometrically Nonlinear Analysis of Pipelaying in an Ocean Environment
Authors: Odorizzi S. , Schrefler B. A.
Published: November 2009

A three-dimensional analysis for pipelines suspended between the ocean floor and a laying barge or a stinger is presented. The analysis performed is capable of handling not only variations in bending stiffness, weight and buoyancy, crosscurrents and lateral bay drift, but also the effects of external hydrostatic pressure and buckling of the pipes. For this purpose a total Lagrangian geometrically nonlinear analysis in space. Examples are given which demonstrate the versatility of the analysis proposed.
Three-Dimensional Finite Element Analysis of Elastic-Plastic Crack Problems
Authors: Kiefer B. V. , Hilton P. D.
Published: November 2009

A three-dimensional, elastic-plastic finite element program is developed and applied to analyze the stress field in a plate containing a through crack. The center cracked plate is subjected to uniform tensile loading which results in mode I opening of the crack surfaces. Transverse variations of the opening tensile stress component and of the effective stress (von Mises) in the vicinity of the crack front are presented. They clearly demonstrate the three-dimensional nature of this problem with distributions that depend on specimen thickness. For thinner plates, the plastic deformation concentrates near the plate surfaces while the normal stress is largest in the plate interior. In thicker plates the deformation and normal stress fields are more uniform in the plate interior near the crack front, but they develop a rapid boundary layer-type variation in the vicinity of the plate surfaces.
A Computational Model of Backlay Welding for Controlling Residual Stresses in Welded Pipes
Authors: Brust F. W. , Rybicki E. F.
Published: November 2009

Intergranular Stress Corrosion Cracking (IGSCC) has been a problem in Boiling Water Reactor (BWR) piping systems. One method for retarding IGSCC is to eliminate tensile residual stresses at the pipe inner surface in the heat affected zone produced by the welding process. A method called backlay welding can be effective in producing compressive residual stresses at the pipe inner surface. This paper describes a computational model and its use in examining the effectiveness of the backlay welding process. The model has demonstrated an ability to predict weld-induced residual stresses for a variety of pipe sizes and welding conditions. Computational results for backlay welding are in agreement with residual stress data. The mechanisms causing residual stresses and the effect of the number of backlay weld layers on residual stresses are discussed.
Further Studies of the Interface Boundary Conditions for Bolted Flanged Connections
Authors: Jofriet J. C. , Sze Y. , Thompson J. C.
Published: November 2009

In the design of bolted flanged connections, the a-priori unknown interface contact stress condition is an important factor, determining directly whether leakage is probable and, indirectly, the stresses at critical regions such as the shell/flange junction. To provide designers with such information without the need of an often costly iterative analysis, data from numerical and physical models of typical flanged connections are analyzed. The dependence of the location, distribution and magnitude of the contact stress on the geometry of the connection and the assembly or working load level is established. Results are presented in a nondimensional form which makes them applicable to all geometrically similar flanges. Certain simple approximate relationships between the nondimensional variables describing the contact zone and the normalized contact stress distribution are noted and their usefulness as design aids explained.
Pneumatic Rupture of a Brittle Pipe: The Depressurization Transient Adjacent to the Ruptured Zone
Authors: Baum M. R. , Elston M. J. H.
Published: November 2009

A simple theoretical model is developed to predict the pressure transient within a gas-pressurized pipe when an adjacent section shatters into many fragments. Comparison with experiment shows that the model correctly predicts the general form of the transient over a wide range of bursting pressure and rupture zone lengths, though the measured initial depressurization rates all fall below the predicted values.
Evaluation of Thermal Conductivity in Layered Vessels
Authors: Armstrong W. P. , Jawad M. H.
Published: November 2009

Thermal conductivity in layered vessels is evaluated experimentally from full-scale models. The effects of various parameters, such as wrapping tightness, pressure variation, heating versus cooling, and temperature, are investigated. A summary and recommendations are given for design purposes.
Acoustic Loading Effects on Oscillating Rod Bundles
Authors: Lin W. H.
Published: November 2009

This paper is concerned with the analytical study of the interaction between an infinite acoustic medium and a cluster of circular rods. The acoustic field due to oscillating rods and the acoustic loading on the rods are first solved in a closed form. The acoustic loading is then used as a forcing function for rod responses, and the acousto-elastic couplings are solved simultaneously. Numerical examples are presented for several cases to illustrate the effects of various system parameters on the acoustic reaction force coefficients. The effect of the acoustic loading on the coupled eigenfrequencies are discussed.
Transient Cavitation in Fluid-Structure Interactions
Authors: Kot C. A. , Hsieh B. J. , Youngdahl C. K. , Valentin R. A.
Published: November 2009

A generalized column separation model is extended to predict transient cavitation associated with fluid-structure interactions. The essential feature of the combined fluid-structure interaction calculations is the coupling between the fluid transient, which is computed one dimensionally, and the structural response which can be multidimensional. Proper coupling is achieved by defining an average, one-dimensional, structural velocity and by assuming a spatially uniform pressure loading of the structure. This procedure is found to be effective even for very complex finite element structural models for which the required computational time step is orders of magnitude smaller than that for the fluid transient. Computational examples and comparison with experimental data show that neglecting cavitation and setting the fluid velocity at all times equal to that of the structural boundary leads to unreal negative pressure predictions. On the other hand a properly coupled column separation model reproduces the important features of fluid-structure interactions, converges rapidly, and gives reasonable fluid and structural response predictions.
The Relationship Between Breach Development and the Depressurization Transient During Axial Rupture of a Gas-Pressurized Steel Pipe
Authors: Baum M. R.
Published: November 2009

Theoretical models are developed to predict the depressurization generated by a propagating axial rupture in a gas-pressurized steel pipe. The pressure transient is composed of a relatively slow depressurization within the rarefaction wave which propagates through the undisturbed gas ahead of the developing breach and a rapid depressurization within the breach zone. The models combine a simplified one-dimensional treatment of the gas flow local to the breach with experimental breach area growth data. An instantaneous steady flow through the developing breach is assumed to determine the boundary condition for the rarefaction wave. The breach zone depressurization is assumed to be dominated by the transverse wave action initiated by the arrival of the breach at the observation point. In both cases the predicted transients are in good agreement with experimental pressure histories.
Influence of Service Exposure on Base and Weld Metal of 1/2 Cr-1/2 Mo-1/4 V High-Pressure Steam Inlet Piping
Authors: Ellis F. V. , Hilton S. O. , Henry J. F. , Bynum J. E.
Published: November 2009

An investigation was performed on a circumferential weld joint in a 1/2 Cr-1/2 Mo-1/4 V high-pressure steam inlet pipe following the detection of steam leakage in a weld area. The component, 326 mm o.d. × 55 mm wall steam pipe, had accumulated approximately 75,000 hr of service at 566C. A special welding technique had been employed with the 2-1/4 Cr-1 Mo weld metal which created a fully refined heat-affected zone (HAZ) grain structure. The failure path conformed to the contour of the HAZ through more than half of the wall thickness. The cracking was intergranular and had propagated in a narrow zone of material at the intersection of the fine-grained HAZ and the parent metal. For the base metal, the short-time rupture strengths of the service-exposed material were below those of the unexposed material. A Larson-Miller parameter correlation indicated that the nominal operating stress and temperature are in the regime where the rupture strengths for the service-exposed base material are as good as those for unexposed material.
The Cross-Flow Response of a Tube Array in Water—A Comparison With the Same Array in Air
Authors: Weaver D. S. , Koroyannakis D.
Published: November 2009

A water tunnel study was conducted on a parallel triangular array of tubes with a pitch ratio of 1.375. The array was geometrically identical to that used previously in a wind tunnel study so that the tube response to cross flow could be compared. It was seen that the response curves for tube arrays in water are much less regular than those in air, creating ambiguity in defining the stability threshold. The irregularities are seen to be associated with shifts in relative tube mode and frequency. Arrays in water apparently first become unstable in one of the lowest frequencies of the band of frequencies associated with a given structural mode. The added mass coefficient computed from the observed frequency at instability is a little larger than the largest added mass coefficient obtained from existing theory for tube arrays in quiescent fluid.
A Simplified Method for Determining Acoustic and Tube Eigenfrequencies in Heat Exchangers
Authors: Planchard J. , Remy F. N. , Sonneville P.
Published: November 2009

A method of computation of eigenfrequencies of large tube arrays is presented, which is based on homogenization techniques. It is supposed that the fluid is compressible, at rest and contained in a cavity; the bundle geometry is assumed to be repetitive; an equivalent sound velocity through the tubes can then be calculated, and the fluid-structure interaction is taken into account. A new eigenvalue problem is so obtained, defined over a simpler domain, i.e., the region occupied by both fluid and tubes; it is then easy to solve it for computing the eigenfrequencies of the coupled system. Numerical and experimental results are presented and some details of the experimental apparatus are given.
The Effect of Pipe Thickness on Residual Stresses due to Girth Welds
Authors: Rybicki E. F. , McGuire P. A. , Merrick E. , Wert J.
Published: November 2009

This paper addresses the question of what effect the pipe thickness has on weld residual stresses in 304 stainless steel piping. Two diameters are considered. These are nominal 4-in. and 10-in. diameters. Four pipe wall thicknesses corresponding to schedules 10, 40, 80, and 160 are examined for each pipe. The focus is on residual stress distributions on the pipe inner surface because this is a primary site for intergranular stress corrosion cracking in 304 stainless steel pipes. The trends in residual stress values are toward more compressive stresses at the pipe inner surface for thicker pipes with the same nominal diameter. Residual axial stresses for the thick 10-in. schedule 160 pipe were found to be compressive while those for the thinner schedule 80 pipe were tensile. X-ray residual stress data for a 6-in-dia schedule 160 pipe fall between the results for the 4-in. and 10-in. schedule 160 pipes and support the findings of the study.
A Finite Element Model for Thick-Walled Axisymmetric Shells
Authors: Barrett D. J. , Soler A.
Published: November 2009

The symmetrically loaded moderately thick-walled shell of revolution can be treated by general finite elements, or for certain geometric conditions, by extended thin shell finite elements that have incorporated transverse shear deformation. In this work, we develop a higher order theory finite element model for symmetrically loaded shells of revolution which is useful for configurations which are out of the range of validity of the extended thin shell elements. Legendre polynomial series expansions are key features of the development and lead to nonlinear distributions of both stress and deformation in the thickness variable. Problems are solved to yield some initial data for comparison of the cost and accuracy of the higher order theory finite element model to other shell element models.
Applications of Energy Release Rate Techniques to Part-Through Cracks in Experimental Pressure Vessels
Authors: Bass B. R. , Bryan R. H. , Bryson J. W. , Merkle J. G.
Published: November 2009

In nonlinear applications of computational fracture mechanics, energy release rate techniques are used increasingly for computing stress intensity parameters of crack configurations. Recently, deLorenzi used the virtual-crack-extension method to derive an analytical expression for the energy release rate that is better suited for three-dimensional calculations than the well-known J-integral. Certain studies of fracture phenomena, such as pressurized-thermal-shock of cracked structures, require that crack tip parameters be determined for combined thermal and mechanical loads. A method is proposed here that modifies the isothermal formulation of deLorenzi to account for thermal strains in cracked bodies. This combined thermo-mechanical formulation of the energy release rate is valid for general fracture, including nonplanar fracture, and applies to thermo-elastic as well as deformation plasticity material models. Two applications of the technique are described here. In the first, semi-elliptical surface cracks in an experimental test vessel are analyzed under elastic-plastic conditions using the finite element method. The second application is a thick-walled test vessel subjected to combined pressure and thermal shock loading.
Dynamic Crack Curving and Branching in Line-Pipe
Authors: Ramulu M. , Kobayashi A. S. , Kang B. S.-J.
Published: November 2009

The newly derived dynamic crack curving and crack branching criteria are briefly reviewed. The two criteria are justified by a micro-mechanics model and are used to predict crack curving and crack branching of dynamic photoelastic experiments involving Homalite-100 fracture specimens. The latter crack branching criterion requires as a necessary condition a critical dynamic stress intensity factor, Klb, which is accompanied by a sufficient condition involving the former crack curving criterion. This criteria is further verified by a dynamic finite element analysis of a bursting steel pipe of Congleton [26] and Almond, et al. [27], where the numerically computed branching stress intensity factor and branching angle are in good agreement with experimental results.
On a Study of the Use of the (T˙) Integral in Fracture Analysis of Solids With Inelastic Rate-Constitutive Laws
Authors: Nakagaki M. , Atluri S. N.
Published: November 2009

Here, the following topics are discussed: (i) a new integral (ΔT1) of relevance in the presence of cracks in an elastic-plastic material characterized by a rate-independent incremental constitutive law under the assumption of infinitesimal deformations, (ii) the conditions for path-independency of this integral, (iii) the physical meaning of (ΔT1) whether or not it is path-independent, (iv) its relation to J under conditions of radial loading when deformation theory of plasticity may be valid. The features of this new parameter (ΔT1) are brought out in a numerical solution of a compact tension specimen which is subject to a history of (displacement-controlled) loading/unloading/reloading. The implications of the present results in the context of more rational elastic-plastic fracture criteria are briefly discussed.
VCE Method of J Determination for a Pressurized Pipe Under Bending
Authors: Yang C. Y. , Palusamy S. S.
Published: November 2009

The J values for a circumferential through crack in a 4-in. (101.6-mm) schedule 80 pipe subjected to axial and bending loads were determined. The Virtual Crack Extension (VCE) method was used to compute J values. The VCE calculated J values are then compared with those obtained by the differential potential energy method and a simplified fracture analysis method. Good comparisons are observed between the results obtained from all of these three methods up to a load level well above the first yield. Advantages of using VCE method are discussed. Experimental results are presented for an identical pipe, made of 304 wrought stainless steel, containing a circumferential through-wall crack and subjected to internal pressure and external bending moment. The VCE method is used to obtain the load versus J relationship from which the initiation load is estimated using the J initiation value obtained from compact tension specimens. This value is then compared to the initiation load determined by acoustic emission measurements. These two results agree within the estimated experimental scatter.
A Procedure for the Assessment of the Structural Integrity of Nuclear Pressure Vessels
Authors: Bloom J. M.
Published: November 2009

This paper presents a simple engineering procedure that the utility industry can use to assess the integrity of typical nuclear-grade pressure vessels. The procedure recognizes both brittle fracture and plastic collapse and is based on a set of proposed failure assessment curves which make up a safety/failure plane. The plane is defined by the stress intensity factor/fracture toughness ratio as the ordinate and the applied stress/reference plastic collapse stress ratio as the abscissa. The failure assessment procedure is based in part on the British Central Electricity Generating Board’s R-6 failure assessment diagram and the deformation plasticity solutions of the General Electric Company. Two parameters, a plastic collapse parameter (Sr′) and linear elastic fracture mechanics parameter (Kr′) are calculated by the user. The point (Sr′, Kr′) is plotted on the appropriate failure assessment diagram. If the point lies inside the respective curve, the structure is safe from failure. Moreover, for a given pressure and a postulated or actual flaw size, the margin of safety of the structure can be simply determined. Consistent with Appendix A of Section XI, (Division 1) of the ASME Boiler and Pressure Vessel Code the procedure presented in this paper is limited to ferritic materials 4 in. (102 mm) and greater in thickness. Details of the derivation of the proposed set of failure assessment curves are provided along with a sample problem illustrating the use of these curves.
Fast Floor Response Spectra Generation Technique
Authors: Yan M. J.
Published: November 2009

A consistent technique is derived for generating floor response spectra for equipment in nuclear reactor systems using response spectral analysis. The use of this technique eliminates the requirement for a time history analysis. The technique is based on the dynamic theory of coupling the supporting building with a very light spring-mass system representing the equipment. The response of the spring-mass system in the coupled systems is the floor response spectrum at the spring-mass system frequency. Resonant and off-resonant cases are derived separately. This technique is more efficient in the use of computer time than the conventional time history techniques. Moreover, a more realistic response spectrum is generated by this technique.
Second Marshall Study Group Report on PWR Pressure Vessel Integrity
Authors: Davies L. M. , Garne L. , Collier J. G.
Published: November 2009

The Second Report of the Marshall Study Group, entitled “An Assessment of the Integrity of PWR Pressure Vessels,” was published recently by the United Kingdom Atomic Energy Authority. The Report considers the integrity of a 4-loop PWR pressure vessel as now made, from the best available materials and using the most modern fabrication practices.
Sensitivity of Estimated Tube Life to Material Property Variation
Authors: Berman I. , Rao M. S. M.
Published: November 2009

The estimated tube life of the Incoloy 800 tubes of a solar receiver panel under nonaxisymmetric loading is compared for various material property assumptions. The basis of each life evaluation is an elastic-creep analytical study of up to 20 load cycles. The effect on tube life of a variation in the creep rate for the failure modes of creep ratcheting and creep fatigue is studied in some detail. As shown for these elastic-creep conditions, the creep damage and mean diametral strain accumulations per cycle decrease linearly over the calculated 20 cycles when plotted against cycle number on a log-log scale. The predictions of total creep damage and mean diametral strain in 10,000 cycles based on the extrapolated log-log scale curve are substantially lower than the predictions based on multiplication of the change in value of the 20th day of operation by 10,000. A limited evaluation of the effects of variations in other material parameters is also made.
Repair of Bellows Expansion Joints
Authors: Merrick E. A. , O’Toole W. , Malkmus M.
Published: November 2009

A metal bellows expansion joint is a highly engineered, precisely manufactured piping system component. It cannot withstand mechanical abuse and perform its intended function without repair or replacement. A 304 stainless steel two-ply metal bellows expansion joint was intentionally damaged by drilling or grinding holes and grooves through the outer ply and subsequently weld-repaired by welding patches over the defects or by filling the grooves. In addition, gouges that did not penetrate the outer ply were blended to a smooth contour. This assembly was fatigue tested to demonstrate that when inadvertent damage does occur the bellows may be repaired. There are three methods of repair which may, under closely controlled circumstances, be a justifiable alternate to replacement of the bellows. Details of this testing program are described in this paper.
Crack Initiation Under Low-Cycle Multiaxial Fatigue in Type 316L Stainless Steel
Authors: Jacquelin B. , Hourlier F. , Pineau A.
Published: November 2009

Low-cycle fatigue tests corresponding to fatigue life range between 103 and 105 cycles were carried out at room temperature on one heat of 316 L austenitic stainless steel. These tests included: (i) reversed tension-compression, (ii) reversed tension-compression with a superimposed steady torque, (iii) pulsated tension-compression with a stress ratio (Rσ) such that −0.5<Rσ<0, (iv) reversed and pulsated tension-compression with a superimposed steady internal pressure. In tests (ii), the torsional ratcheting effect was measured. SEM observations were used to determine the number of cycles corresponding to Stage I crack initiation and the orientation of Stage I microcracks. It was observed that the in-depth growing Type B shear microcracks were most damaging. A simple criterion is proposed Ni=No(Δγp B)α•(σnB)β where Ni is the number of cycles to crack initiation, Δγp B is the range of plastic shear strain on Type B planes, σnB is the maximum normal stress acting on these planes, No,α and β are parameters adjusted from the Manson-Coffin law and reversed cyclic stress-strain behavior.
Lifetime Analysis of Fusion Reactor First Wall Components
Authors: Watson R. D. , Peterson R. R. , Wolfer W. G.
Published: November 2009

Linear elastic fracture mechanics is used to predict the growth of a semi-elliptical surface flaw through a thin-walled actively cooled 316 stainless steel first wall in a tokamak power reactor, which is subjected to pulsed surface heat fluxes, 14 MeV neutron irradiation and sputtering from particle bombardment. The results from an inelastic stress analysis, which includes thermal creep, irradiation creep, swelling, and wall thinning, are coupled to the crack growth calculations. The effects of temperature, R-ratio, threshold ΔK, neutron-induced embrittlement, creep crack growth and two-dimensional flaw shape changes are included. Predictions for a cylindrical blanket module with hemispherical first wall end cap indicate that severe reductions in lifetime can occur when radiation damage effects are included and demonstrate the need for high fluence data on da/dN and KIc.
Experimental Investigation of Cylindrical Shell Stresses due to Penetration Loads Where R/T = 1264
Authors: Whipple R. A. , Hagstrom J. , Dykstra H.
Published: November 2009

Stresses and displacements for a nozzle connection typical of those found in a large storage or pressure vessel were measured for applied radial forces, circumferential moments and longitudinal moments. The test program was conducted on a 2 1/2-in. φ penetration, centered and welded into a 60 in. × 60 in. cylindrical panel with a radius to thickness ratio of 1264. The nozzle diameter to cylindrical shell diameter ratio was 0.01. The panel edges were bolted to a stiff rectangular frame. This report presents the measured radial deflections and nozzle rotations, the membrane stress resultants and shell bending moments in the vicinity of the penetration for the three loadings. A brief description of the model and the test procedure is also presented.
Corrosion Fatigue Crack Growth in Reactor Pressure Vessel Steels in PWR Primary Water
Authors: Scott P. M. , Truswell A. E.
Published: November 2009

Experimental results for corrosion fatigue crack growth in several different ferritic pressure vessel steels including A533-B and A508-III exposed to simulated PWR primary water at 288°C are described. Since relatively little influence of environment was detected in low-frequency tests on these materials, in contrast with data reported from another laboratory, specimens have been exchanged and tested in each laboratory. These results are described, and possible reasons for the observed differences when each tested the same material are discussed. The environmental influence on corrosion fatigue crack growth is analyzed on the basis of a model of a sequence of protective oxide rupture/repassivation events during fatigue cycling. The repassivation kinetics and the controlling electrochemical factors are judged to be of crucial significance in determining the extent of environmental enhancement of fatigue crack growth.
Progress in Developing Constitutive Equations for Inelastic Design Analysis
Authors: Pugh C. E.
Published: November 2009

A summary is given of the constitutive equations that have been developed for use in design assessments of elevated temperature components of liquid metal fast breeder reactors. The discussion addresses representations of short-term (plastic) and long-term (creep) inelastic material responses. Attention is given to improved representations of the interactions between plastic and creep deformations. Most of the discussion is in terms of constitutive equations that make use of the concept of separating the total strain into elastic, plastic, and creep portions. Additionally, some discussion is given of progress being made toward establishing design equations based on unified measures of inelastic strain that do not distinguish different strain portions.
Elastic-Plastic Analysis of Crack Opening, Stable Growth and Instability Behavior in Flawed 304 SS Piping
Authors: German M. D. , Kumar V.
Published: November 2009

Crack initiation, stable growth, instability and crack opening behavior in flawed 304 SS piping has been examined within the framework of the engineering approach developed by Kumar, German and Shih [1]. Crack geometries considered include part-through, complete circumferentially cracked pipe subjected to remote tension, and through-wall flawed pipe in tension and in bending. Effect of flaw type and size, pipe diameter and length, and applied loading on the failure load and mechanism is investigated. Results are employed to assess the net section stress criterion based on plastic collapse. Crack opening area of interest in leak rate evaluations is calculated as a function of applied load or pipe end deflection for stationary as well as growing cracks.
Heat-to-Heat Variations in Creep-Rupture Properties of Annealed 2 1/4 Cr-1 Mo Steel
Authors: Klueh R. L.
Published: November 2009

The creep and creep-rupture properties of 13 heats of annealed 2 1/4 Cr-1 Mo steel were determined at 510 and 566°C (950 and 1050°F). The microstructures of all heats were primarily polygonal ferrite (75–80 percent); the balance was mostly bainite with 1–2 percent pearlite and scattered carbides. At each temperature the results indicated considerable data scatter for the high-stress (short rupture life) tests. As the stress was lowered, the creep and stress-rupture properties converged, which resulted in a decrease in the data scatter. Much of the variation and change in the properties could be attributed to the carbide precipitation reactions that occur in the steel.
Nonlinear Bending and Collapse Analyses of a Poked Cylinder and Other Point-Loaded Cylinders
Authors: Sobel L. H.
Published: November 2009

Numerical results based on the STAGSC-1 finite element computer program are presented for the geometrically nonlinear behavior of cylindrical shells subjected to inward-directed radial point loads. Three elastic shell problems are considered: the poked cylinder (single load at midlength), which is the problem of primary interest, and the venetian blind and pinched cylinder, which are check cases. Load versus displacement curves obtained for the three problems reveal that geometric nonlinear (large displacement) effects are important. For the poked cylinder it is concluded that the maximum at the limit point of the load-displacement curve corresponds to a small local snapping of the cylinder that does not result in a loss of load-carrying capacity. The paper also discusses certain features of STAGSC-1 that should be helpful to users of the program.
A Guide for Determining Postweld Heat Treatment Requirements for ASME Code Section VIII Pressure Vessels
Authors: Carpenter D. D.
Published: November 2009

This paper discusses some uncertainties that occasionally arise when considering postweld heat treatment and presents, by the use of decision trees, a quick method for determining whether or not postweld heat treatment is required.
Design Guidance for Elastic Followup
Authors: Naugle F. V.
Published: November 2009

The basic mechanism of elastic followup is discussed in relation to piping design. It is shown how mechanistic insight gained from solutions for a two-bar problem can be used to identify dominant design parameters and to determine appropriate modifications where elastic followup is a potential problem. It is generally recognized that quantitative criteria are needed for elastic followup in the creep range where severe unbalance in the stiffness of connected line segments can pose potential problems. Approaches for criteria development are discussed.
Dynamic Tests of Cracked Pipe Components
Authors: Hale D. A. , Heald J. D. , Sharma S. R.
Published: November 2009

Dynamic tests were conducted involving notched sections of 4-in. (10-cm) stainless steel and Inconel-600 pipe. The specimen was a four-point bending beam with end masses sized to give an elastic first-mode frequency near that of typical field-installed piping systems (15 Hz). Specimens were loaded using sinewave excitation at this first mode natural frequency. Specimen response was compared to predictions from an elastic-plastic dynamic analysis previously developed on this program. In addition, specimen loads at failure were compared to those predicted from a net section collapse failure criterion. The results confirmed that the elastic-plastic dynamic analysis adequately predicted the dynamic response of flawed pipes under seismic-type excitation. Furthermore, net section collapse does not occur under dynamic loading conditions which simulate natural frequencies of as-installed light water reactor piping systems. Finally, a net section collapse criterion yields conservative estimates of the load capacity of flawed pipe sections provided crack growth is properly accounted for.
Correlation of Support Impact Force and Fretting-Wear for a Heat Exchanger Tube
Authors: Ko P. L. , Basista H.
Published: November 2009

Flow-induced tube vibration can cause dynamic interactions between a tube and its supports. Both wear information and results from vibration analyses are needed to achieve a realistic assessment of long-term tube wear. Normal and oblique impact forces at the tube supports characterize dynamic interaction between tube and tube-support, and can be correlated to the rate of fretting-wear. A statistical analysis of the force signal provides an indication of the time distribution of various force levels during a vibration cycle. Different schemes for obtaining a weighted sum of these force levels were developed to account for changes in excitation levels, tube/support clearance, and the type of tube motion. With one of the schemes, the correlation to measured wear data was good. Therefore, fretting-wear can be estimated directly from the analytically predicted support impact force in a steam generator or heat exchanger tube. The effects of other support parameters, such as tube support land area, can be added to the empirical equation. A series of tests involving the three parameters mentioned were performed in room temperature water. Forces along two orthogonal axes at the support were recorded and analysed. The paper presents the results of these tests and shows the correlation between the wear results and the force functions. A computer code for predicting tube/support dynamic interaction is used to estimate wear damages from the experimental force-wear correlation.
The Influence of High-Frequency Excitation on Piping and Support Design
Authors: Lockau J. , Haas E. , Steinwender F.
Published: November 2009

The effect of a high-frequency excitation on piping systems and supports is demonstrated. The influence of local plasticity on the dynamic behavior is shown in an analytical benchmark. The evaluation of several full-scale experiments resulted in rather large safety margins between calculated and allowed stresses. The stresses were calculated following the standard nuclear codes. No failure occurred in the tested structures even under extreme overloading. This demonstrates the high capacity of structures to survive dynamic load. A theoretical explanation is found in the effect of energy absorption by plastic deformation. This effect has been evaluated in a 1-DOF system showing for austenitic material 15 percent of material damping for 3 Sm. If this effect should be the result of modal response spectra analysis, the corresponding spectra would have to show very flat amplification ranges. The reduction of the overstresses by this approach could be shown in 2 numerical examples.
Evaluation of the Growth and Stability of Stress Corrosion Cracks in Sensitized Austenitic Piping
Authors: Horn R. M. , Kass J. N. , Ranganath S.
Published: November 2009

This paper presents the results of a research program conducted to evaluate the behavior of stress corrosion cracks in sensitized austenitic piping exposed to high temperature, high purity oxygenated water. The program was directed toward the development of a predictive method which included a design margin assessment and an evaluation of crack growth leading to a predictive model. As part of the margin assessment, the program developed diagrams which predicted net section collapse as a function of crack size. Acceptance flaw sizes were then determined by applying a safety factor on the net section collapse condition. The growth behavior of stress corrosion cracks was assessed using laboratory test crack growth rate data coupled with linear elastic fracture mechanics. Knowing the initial flaw size, the crack growth rate data can be used to predict the final flaw size at the end of the next inspection period. Continued operation would be acceptable during this period if the final flaw size is less than the acceptance value. The method developed here can be applied using stress information available in ASME (American Society of Mechanical Engineers) Code piping stress reports and crack growth data presented here. The method developed can be used to establish an in-service inspection plan for power plants with cracked piping allowing continued plant operation. Example predictions for 4-in. (10.16-cm) and 24-in. (61-cm) pipe were made to demonstrate the methodology’s use.