bluuebunny/crossref_metadata_2025 huggingface dataset:
TRANS2A: An Unconditionally Stable Code for Thermal Transient Stress Analysis in Piping
Authors: Strong B. R. , Slagis G. C.
Published: November 2009

A technique for numerical integration of the finite difference (matrix) formulation of the unsteady heat transfer equation has been applied to the thermal stress analysis requirements of ASME B&PV Section III, Article NB-3650. This technique, with its properties of unconditional solution stability, has been incorporated into a new computer program, TRANS2A, which has been designed totally around the needs of the stress analyst. To be of maximum aid to the analyst, in addition to the necessary output of thermal gradients (ΔT2 and ΔT2) and average temperatures (Ta and Tb), TRANS2A provides a complete set of thermal stress histories and tables of thermal stress extrema. Values of the thermal stresses are output at maxima of the thermal gradient terms (with or without adjacent sections), in addition to the extrema of the secondary and secondary plus peak stresses and time of occurrence. Each solution is performed for a set of seven general and three optional stress indices. The process allows a strict and simple data interface to the combined stress analaysis computation without excessive approximations. Data may also be stored so that sections need not require repeated analyses. All computational output, from the detailed heat transfer solution to the stress summaries, may be requested or deleted at the option of the analyst. For generality, TRANS2A includes a complete set of temperature-dependent material properties for all current piping materials and a complete set of fluid properties for water, steam, and sodium. Fluid transient data are input using phase and temperature, and a choice of four flow rate specifications. Accepted heat transfer correlations for laminar and turbulent flow in liquids and gases are included, with smoothing at two-phase excursions. Samples of the TRANS2A benchmark problems are included, with discussions on data interface and sensitivity for erratic fluid transients.
Application of the Tearing-Mode Crack-Growth Instability Theory to a Cracked Pressure Vessel Nozzle
Authors: Musicco G. G. , Rossow M. P. , Szabo B. A.
Published: November 2009

The theory of tearing-mode crack-growth instability as developed by Paris and his associates is briefly outlined. Then the theory is applied to study the stability of a deep crack in a pressure vessel nozzle. The finite-element method is used to analyze the structure, which is idealized as a two-dimensional elastic-plastic body. Based on the theory and the results of the finite-element calculation, the stability (or instability) of the crack is predicted, as a function of pressure in the vessel. A detailed examination of the solution near the crack tip is made to verify that the necessary conditions for J-controlled crack growth are present.
Stress Intensity Factors due to Residual Stresses in Thin-Walled Girth-Welded Pipes
Authors: Rybicki E. F. , Stonesifer R. B. , Olson R. J.
Published: November 2009

The effect of a girth-weld-induced residual stress field on the linear elastic fracture mechanics of a thin-walled pipe is examined. The procedure for using the residual stress distribution to compute KI and KII for a circumferential crack which is growing radially is described. In addition to the two-pass girth weld, stress intensity factors are computed for a residual stress distribution in a flat plate and for a hypothetical residual stress state in a second thin-walled pipe. The computed stress intensity factor for the flat plate geometry and its residual stress distribution are compared with a solution from the literature as a check on the computational procedure. The through-the-thickness residual stress distribution due to the two-pass girth weld is similar to a half-cosine wave. For purposes of comparison, the hypothetical through-the-thickness distribution selected for the second pipe is similar to a full cosine wave. The stress intensity factor is presented as a function of crack depth for a crack initiating on the inner surface of the pipe. The redistribution of residual stresses due to crack growth is also shown for selected crack lengths. The study shows that residual stress-induced crack growth in pipes can be significantly different from that in flat plates due to the possibility of locked-in residual bending moments in the pipe. These locked-in moments can have effects similar to externally applied loads and can either promote or restrain crack growth. A residual stress distribution is illustrated in which crack growth, if initiated, would continue through the entire wall. Also, a residual stress distribution is illustrated for which the crack could arrest after a certain amount of growth.
Analytical/Experimental Correlation of a Nonlinear System Subjected to a Dynamic Load
Authors: Anderson J. C. , Masri S. F.
Published: November 2009

Analytical and experimental studies of the dynamic response of a system with geometric and material nonlinearity are described. The dynamic excitation consists of sinusoidal and impulsive base acceleraton. The dynamic system, which is representative of many practical cases involving mechanical equipment and piping systems, consists of a cantilever beam with a gapped support at the free end. The material nonlinearity considers both the effect of yielding and the effect of strain rate on the initial yield level. The analytical studies are performed by transforming the continuous system to an equivalent single-degreee-of-freedom system and using numerical techniques to solve the resulting equation of motion. Experimental studies are conducted and responses are measured on the same dynamic systems. Critical comparisons are made between the calculated and measured responses.
Flow Velocity Dependence of Damping in Tube Arrays Subjected to Liquid Cross-Flow
Authors: Chen S. S. , Jendrzejczyk J. A.
Published: November 2009

Experiments are conducted to determine the damping for a tube in tube arrays subjected to liquid cross-flow; damping factors in the lift and drag directions are measured for in-line and staggered arrays. It is found that: 1) fluid damping is not a constant, but a function of flow velocity; 2) damping factors in the lift and drag directions are different; 3) fluid damping depends on the tube location in an array; 4) flow velocity-dependent damping is coupled with vortex shedding process and fluid-elastic instability; and 5) flow velocity-dependent damping may be negative. This study demonstrates that flow velocity-dependent damping is important. These characteristics should be properly taken into account in the mathematical modeling of tube arrays subjected to cross-flow.
Ductile Fracture of Pipes and Cylindrical Containers With a Circumferential Flaw
Authors: Erdogan F. , Delale F.
Published: November 2009

The paper deals with the problem of ductile fracture of a pipe or cylindrical container having a relatively long and deep circumferential part-through crack or a through crack and subjected to a uniform axial membrane load in the crack region. After describing the evolution of the ductile fracture process, first the results of the elasticity solution for the circumferentially cracked cylindrical shell based on the Reissner’s transverse shear theory are presented. The elastic-plastic part-through crack problem is then considered. In the analysis the plastic deformations are approximated by a perfectly plastic layer similar to the conventional Dugdale model. The load carrying capacity of the cylinder is then estimated in various ways by using the crack opening stretch along the leading edge of the crack as the critical load factor.
A Finite Element Formulation for Fluid-Structure Interaction in Three-Dimensional Space
Authors: Kulak R. F.
Published: November 2009

In this paper a development is presented for a three-dimensional hexahedral hydrodynamic finite-element. Using trilinear shape functions and assuming a constant pressure field in each element, simple relations were obtained for internal nodal forces. Because the formulation was based upon a rate approach it was applicable to problems involving large displacements. This element was incorporated into an existing plate-shell finite element code. Diagonal mass matrices were used and the resulting discrete equations of motion were solved using an explicit temporal integrator. Results for several problems were presented which compare numerical predictions to closed form analytical solutions. In addition, the fluid-structure interaction problem of a fluid-filled, cylindrical vessel containing internal cylinders was studied. The internal cylinders were cantilever supported from the top cover of the vessel and were periodically located circumferentially at a fixed radius. A pressurized cylindrical cavity located at the bottom of the vessel at its centerline provided the loading.
Vibrations of Square and Hexagonal Cylinders in a Liquid
Authors: Shinohara Y. , Shimogo T.
Published: November 2009

A mathematical model is proposed to describe the dynamic behavior of square and hexagonal cylinder bundles immersed in a liquid. First, the hydrodynamic forces associated with cylinder motions are examined, and then equations of motion of the spring-mounted cylinders including liquid coupling are derived. When the number of cylinders is very large, these equations are replaced by partial differential equations on the assumption that the cylinder bundles form a continuum. The results of this study have application in the modeling of vibration of a nuclear fuel assembly under the excitation of earthquakes.
The Inelastic Line-Spring: Estimates of Elastic-Plastic Fracture Mechanics Parameters for Surface-Cracked Plates and Shells
Authors: Parks D. M.
Published: November 2009

Recent studies of the mechanics of elastic-plastic and fully plastic crack growth suggest that such parameters as the J-integral and the crack tip opening displacement can, under certain conditions, be used to correlate the initiation and early increments of the ductile tearing mode of crack growth. To date, elastic-plastic fracture mechanics has been applied mainly to test specimen geometries, but there is a clear need for developing practical analysis capabilities in structures. In principle, three-dimensional elastic-plastic finite element analysis could be performed, but, in fact, such analyses would be prohibitively expensive for routine application. In the present work, the line-spring model of Rice and Levy [1-3] is extended to estimate the J-integral and crack tip opening displacement for some surface crack geometries in plates and shells. Good agreement with related solutions is obtained while using orders of magnitude less computing time.
Experience With Simplified Inelastic Analysis of Piping Designed for Elevated Temperature Services
Authors: Severud L. K.
Published: November 2009

Screening rules and preliminary design of FFTF piping were developed in 1974 based on expected behavior and engineering judgment, approximate calculations, and a few detailed inelastic analyses of pipelines. This paper provides findings from six additional detailed inelastic analyses with correlations to the simplified analysis screening rules. In addition, simplified analysis methods for treating weldment local stresses and strains as well as fabrication-induced flaws are described. Based on the FFTF experience, recommendations for future Code and Technology work to reduce design analysis costs are identified.
On the Motion of an Axial Through Crack in a Pipe
Authors: Emery A. F. , Perl M. , Love W. J. , Kobayashi A. S.
Published: November 2009

Based upon photographs of running cracks, a simple split ring model is proposed to simulate axially running cracks in very ductile materials. The model is used in conjunction with a one-dimensional transient fluid flow analysis to calculate the velocity of the crack and the fluid pressure history for air, cold water, and hot water-filled pipes. The model is capable of predicting crack initiation, extension, and arrest.
Residual Stress Redistribution Caused by Notches and Cracks in a Partially Autofrettaged Tube
Authors: Pu S. L. , Hussain M. A.
Published: November 2009

A simple method is provided for the computation of the redistribution of residual stresses and the stress intensity factors due to the introduction of notches and cracks in a partially autofrettaged tube. Numerical results of several crack and notch problems are obtained by the method of thermal simulation. These results are shown to be in excellent agreement with those obtained from the classical method of superposition. The new method based on thermal simulation is easier to apply and it avoids the alternate method of superposition requiring cumbersome distributed crack face loadings for each crack configuration.
Creep Rupture Bending Test of 20 Percent Cold-Prestrained Ni-Fe-Cr Alloy Straight Tubes at 1100 F(593 C)
Authors: Woo H. H. , Ryder R. H. , Holko K. H. , Stetson R. F.
Published: November 2009

A four-point bend test was performed on 20 percent cold-prestrained Ni-Fe-Cr alloy tubes at 1100 F (593 C) to verify that creep rupture damage can be used to predict failure in a nonuniform stress field. Deflection control and acoustic emission techniques were used to detect crack initiation, strain gages were employed to record the strain history in the specimen, and a scanning electron microscrope was utilized to check crack initiation and propagation. Stress analyses were made using simplified and finite element methods. Comparison of test results and analyses concluded that creep rupture damage can be used to predict local material failure for structural components under multiaxial nonuniform loading conditions.
A Plastic Fracture Mechanics Prediction of Fracture Instability in a Circumferentially Cracked Pipe in Bending—Part I: J-Integral Analysis
Authors: Zahoor A. , Kanninen M. F.
Published: November 2009

A method of evaluating the J-integral for a circumferentially cracked pipe in bending is proposed. The method allows a J-resistance curve to be evaluated directly from the load-displacement record obtained in a pipe fracture experiment. This method also permits an analysis for fracture instability in a circumferential crack growth using a J-resistance curve and the tearing modulus parameter. The influence of the system compliance on fracture instability is discussed in conjunction with the latter application. The results suggest that a compliant piping system containing a crack can exhibit ductile fracture instability after some stable crack growth. The importance of using a J-resistance curve that is consistent with the type of constraint for a given application is emphasized.
Near-Contact Explosive Forming
Authors: Berman I. , Schroeder J. W.
Published: November 2009

The method of near-contact explosive forming with controlled media is defined and described. Economical examples of the shaping of flat or curved plates with four flat edges, expansion of tubes into tubesheets or outer tubes, and expansion of plugs into tubes are given.
An Analytical Assessment of the Effects of Residual Stresses and Fracture Properties on Service Performance of Various Weld Repair Processes
Authors: Bloom J. M.
Published: November 2009

This paper discusses analytical work done to assess the relative importance of residual stresses and fracture mechanics material properties on the service performance of various weld repair processes. In the first part of this analytical work, a model was developed which quantified the performance of various repair weld procedures. The assessment was based on fracture mechanical performance of two different weld/crack configurations as measured by fracture toughness and fatigue crack growth. One configuration was a crack located in the weld parallel to the welding direction. The other was a crack perpendicular to the weld centered about the midpoint of the weld. Both models were quantified in terms of both brittle fracture and fatigue crack growth mechanisms. Further studies were made assuming that the various weld procedures do not change the material properties of the weld metal, such as fatigue crack growth rates. Several cases were then analyzed assuming a range of residual stress variations in the weld. The results of these analyses quantified the importance of magnitude and distribution of the various chosen residual stress patterns. In the second part, actual material properties were obtained from the literature for the various weld procedures and used to analyze the structural performance in terms of fatigue crack growth resistance. Data taken from a Welding Institute report was used to make comparisons between six different weld metals and two different weld processes. A performance factor, Q, the ratio of fatigue cycles for the weld metal to fatigue cycles for the base metal, was calculated for the six weld metals as a function of residual stress divided by applied stress. Results of the analysis indicated that the highest strength weld metal gave the best performance in terms of fatigue crack growth resistance, while the lowest strength weld gave the worst performance as measured by Q. In addition, scatter in the fatigue crack growth rates was examined for the various weld repair procedures. Based on data obtained from several published sources, the scatter in fatigue crack growth rate was found to be a factor of 3. Allowing for variations in the magnitude of residual stress of an order of magnitude, it was shown that the scatter in fatigue crack growth rate completely overshadows the effect of residual stress variations which could conceivably be produced by the various weld procedures.
Impacted Notch Bend Specimens
Authors: Kobayashi A. S. , Ramulu M. , Mall S.
Published: November 2009

The proposed test procedure for instrumented impact testings is evaluated by the experimental and numerical dynamic fracture results obtained for Homalite-100, polycarbonate, A533B steel and 6061 aluminum notched bend specimens. As expected, brittle fracture of the polymeric, steel and aluminum impacted notch bend specimens considered in this paper cannot be predicted by the static stress intensity factors at the instant of crack propagation. The fracture energy was only a fraction of the total energy and was equally unsuitable for dynamic fracture characterization of these specimens. This evaluation suggests that despite the enormous correlation studies which justify the use of static analysis for specific specimens under specified loading conditions, the proposed procedure should not be used to evaluate fracture data of impacted notch bend specimens of other configurations and loading rates.
Strain Rate Effects in SA-106 Carbon Steel Pipe
Authors: Peterson D. , Schwabe J. E. , Fertis D. G.
Published: November 2009

Experiments were performed to measure the effect of strain rate on the tensile properties of SA-106 carbon steel pipe, in support of analysis and experimental modeling of postulated pipe whip in nuclear power plants. It was observed that increasing the strain rate from 4 × 10−4 to 4 s−1 raised the yield strength by approximately 30 percent.
Collapse of Oil Well Casing
Authors: Huang N. C. , Pattillo P. D.
Published: November 2009

This paper is concerned with the theoretical study of the collapse of oil well casing under various loading conditions. The analysis is based on a model of a cylindrical shell of infinite length subjected to an axial tension and an external pressure. It is found that when the thickness-radius ratio of the casing is sufficiently small, collapse of the casing may take place in a form of plastic buckling. Critical conditions for plastic buckling are derived based on the J2-incremental theory and the J2-deformation theory. Another type of collapse is caused by the realization of the ultimate strength of the material. Critical conditions in the second case of collapse are calculated based on a plane strain formulation associated with the J2-incremental theory. The theoretical results obtained in this paper correspond well with empirical formulas developed earlier by the API for the design of oil well casing.
Residual Stress Generation and Relaxation in Butt-Welded Pipes
Authors: Nair S. , Pang E. , Dix R. C.
Published: November 2009

A numerical scheme for the determination of thermally induced local residual stresses and their relaxation behavior during heat treatment in the case of butt-welded pipes is described. The procedure is illustrated by considering 304 stainless steel and SAE 1020 steel pipes. The results are compared with available experimental and numerical results.
Fatigue Design in Mining Size Reduction Equipment
Authors: Svalbonas V.
Published: November 2009

The mining size reduction equipment industry is reviewed regarding efforts to obtain a consistent fatigue design philosophy. Serious structural failures, which have prompted various company efforts in this area, are reviewed. Efforts to obtain design criteria have been hampered by lack of data concerning the mundane materials, such as cast iron, used in the fabrications. Similar research from high technology industries, therefore, does not provide directly applicable data. However, new testing efforts are underway, and basic fatigue data is being gathered with the goal of providing consistent design, fabrication and nondestructive examination programs.
A Finite Element Time Integration Method for the Theory of Viscoplasticity Based on Infinitesimal Total Strain
Authors: Zirin R. M. , Krempl E.
Published: November 2009

A forward gradient method is employed in the formulation of a time integration scheme for the theory of viscoplasticity based on total strain. The theory uses a viscosity function and an equilibrium stress-strain diagram to characterize a material in monotonic loading. Eight-noded quadrilateral elements integrated by a 2 × 2 quadrature provide spatial modeling. For a thick-walled, axially constrained cylinder under internal pressure the stability of the proposed integration scheme is demonstrated. It is shown that pressurization rate considerably influences the state of stress in the cylinder. The stresses redistribute with time when the pressure is held constant. For long times an equilibrium solution can be obtained. When a bilinear equilibrium stress-strain diagram with zero work-hardening is chosen, the equilibrium solution is shown to correspond to the elastic-perfectly plastic solution.
Biaxial Cyclic Deformation and Creep-Fatigue Behavior of Materials for Solar Thermal Systems
Authors: Majumdar S.
Published: November 2009

Biaxial cyclic deformation and creep-fatigue data for Incoloy 800 and Type 316H stainless steel at elevated temperature are presented. Tubular specimens were subjected to constant internal pressure and strain-controlled axial cycling with and without hold times in tension as well as in compression. The results show that the internal pressure affects diametral ratchetting and axial stress range significantly. However, the effect of a relatively small and steady hoop stress on the cyclic life of the materials is minimal. A 1-min compressive hold per cycle does not seriously reduce the fatigue life of either material; a tensile hold of equal duration causes a significant reduction in life for Type 316H stainless steel, but none for Incoloy 800. Fracture surfaces of specimens made of both materials were studied by scanning electron microscopy to determine the reason for the difference in behavior.
Full Life Elastic-Plastic-Creep Analysis and Comparison to Tests of Axially Cycled Pressurized Tubular Specimens
Authors: Berman I. , Rao M. S. M. , Gupta G. D.
Published: November 2009

Full life elastic-plastic-creep analyses of axially cycled pressurized tubular 316H stainless steel and Incoloy 800 specimens were run in order to evaluate creep ratcheting and creep fatigue behavior. Analytical results were obtained for the loading conditions and the 593°C (1100°F) material properties of the tests reported by Majumdar [1]. Both “book” value and other material property assumptions were used in the analyses and compared with the test results. Some conclusions from these tests are that book property analyses can, in some cases, underestimate the results. Modification of the material properties to more closely mirror actual conditions can, in some cases, greatly improve the predictions.
A Theoretical Model for Fluid-Elastic Instability in Heat Exchanger Tube Bundles
Authors: Lever J. H. , Weaver D. S.
Published: November 2009

A simple theoretical model has been developed from first principles for the fluid-elastic instability in heat exchanger tube bundles. A series of experiments were conducted to verify the basic assumption that only a single tube need be modeled in a flow channel which preserves the basic geometry of the array. The mechanism of instability is found to be one of flow redistribution due to tube motion and a phase lag resulting from fluid inertia. Quite good agreement is found with available experimental data for a parallel triangular array without the need for empirical fluid force coefficients. The model includes the effects of tube array pattern and pitch.
Methods for Minimization of Solution Costs for Transient Dynamic Analysis of Nonlinear Periodic Structures
Authors: Van Kirk J. S. , Bogard W. T. , Wood L. R.
Published: November 2009

Techniques are described for the transient dynamic analysis of nonlinear periodic structures. These techniques consider the special characteristics of periodic structures in conjunction with the pseudo-force approach using numerical integration to reduce computerized solution costs. Comparisons with a general purpose finite element code demonstrate the savings in solution costs.
Plastic Strain Concentrations in Perforated Structures Subjected to Alternating Loads
Authors: Kichko R. D. , Badlani M. , Spaniel F. , O’Donnell W. J. , Porowski J. S.
Published: November 2009

Perforated plates with a uniform triangular penetration pattern subjected to alternating loads are analyzed. The cases of equibiaxial and shear loading are considered and the finite element method is used to obtain elastic-plastic solutions for various ligament efficiencies. The plastic strain concentrations for alternating loads are compared to those for monotonic loading. Useful methods of obtaining plastic strain concentration factors for alternating loads using the results for monotonic loading are given.
Flow-Induced Vibration of Tube Arrays With Various Pitch-to-Diameter Ratios
Authors: Tanaka H. , Takahara S. , Ohta K.
Published: November 2009

Tube arrays in cross flow start to vibrate abruptly when the flow reaches at a certain velocity. The threshold flow velocity depends upon the geometrical arrangement of tubes. It is very important for practical applications to understand the relations between the threshold velocity and pitch-to-diameter ratio of tube array. Unsteady fluid dynamic forces on a tube array with a pitch-to-diameter ratio of 2.0 were clarified experimentally and the characteristics of the threshold velocity were revealed by calculating the velocity with the unsteady forces. By comparing the threshold velocities of tube arrays of pitch-to-diameter ratio of 2.0 and 1.33, the characteristics of threshold velocity with respect to pitch-to-diameter ratio were clarified.
Analytical Failure Prediction of Spherical Composite Pressure Vessels
Authors: Knight C. E.
Published: November 2009

The geometrical complexity of winding patterns for fiber composite spherical pressure vessels has most often resulted in design and analysis based on use of assumed spherical symmetry. Development of computer programs for detailed geometrical description of the fabricated structure winding pattern provides the data needed to perform a finite element analysis and make design improvements. Stress distributions are evaluated by the Weibull statistical failure theory and a failure pressure is predicted. Selected results for a specific case are presented.
The Accumulation of Damage in Plates Subjected to Steady Mechanical Load and Cyclic Thermal Downshocks on One Surface
Authors: Phillips J.
Published: November 2009

Computer calculations, incorporating analysis of elastic, plastic and creep effects, are performed on a Bree plate subjected to steady mechanical load and cyclic thermal downshocks on one surface. Particular attention is given to the accumulation of creep and fatigue damage which is calculated from the stress-strain distributions using linear damage summation rules. The computations examine the dependence of the damage accumulation on such factors as the applied loads, the degree of hardening in the material, the length of the creep dwell period and the severity of the transient thermal loadings as measured by the Fourier and Biot numbers. This indicates which considerations are likely to be important in the design of fast reactor components which experience loadings of this type.
The Accumulation of Damage in Plates Subjected to Steady Mechanical Load and Cyclic Thermal Downshocks on Both Surfaces
Authors: Phillips J.
Published: November 2009

Previously reported computations are extended to analyze a Bree plate subjected to steady mechanical load and cyclic thermal downshocks on both surfaces. It is shown that two critical plate thicknesses can be identified, one below which thermal cycling has no effect, and one above which the full effects of rapid transient thermal loading are observed. The significant effects which material properties, such as the degree of strain hardening present, can have on the plate behavior are also illustrated. These findings are relevant to design of fast reactor components which experience loadings of this type.
Residual Stresses and Their Redistribution During Annealing of a Girth-Butt Welded Thin-Walled Pipe
Authors: Josefson B. L.
Published: November 2009

The redistribution of calculated welding stresses during different post weld heat treatments (PWHT) is numerically investigated for a girth-butt welded thin-walled pipe made of a micro-alloyed carbon manganese steel. A finite element analysis with assumed rotational symmetry is performed. The influence of creep, relaxation and phase transformations is included. The amount of stress reduction is found to be mainly controlled by the holding temperature. Most of this reduction was observed to occur during the end of the heating period where the transient stresses followed the fall of the yield stress with temperature.
The Development of the Breach Generated by Axial Rupture of a Gas-Pressurized Steel Pipe
Authors: Baum M. R.
Published: November 2009

The development of an axial breach during pneumatic rupture of a thin-walled, mild steel pipe is investigated by high-speed photography. Data are presented for the variation of breach area with time, the velocity of the propagating breach tip and the velocity of the free edges. The results indicate that the initial stages of breach growth are controlled by inertia effects, but this is soon superseded by growth dictated by the straining of the free edges and the progress of the propagating crack. A “fully open” breach (breach area = twice pipe cross sectional area) is achieved when the breach length is three pipe diameters. At a breach length of eight pipe radii the breach geometry immediately behind the propagating crack has ceased developing and remains fixed in the subsequent breach development. The measured crack tip propagation velocity, which reaches a peak steady value well before the breach is “fully open,” is compared with a theoretical limit based on the propagation velocity of a displacement wave in a plastic membrane.
Moment Loads Induced by Pressure and Momentum Forces in Piping
Authors: Ware A. G.
Published: November 2009

A structural load, which is often overlooked when ASME Code analyses of piping and nozzles are conducted, is the moment induced by axial elongation of a pipe segment due to internal fluid pressure and momentum. An example illustrates that this effect can sometimes produce stresses which are too large to be ignored.
Stress-Intensity Factors for Internal and External Surface Cracks in Cylindrical Vessels
Authors: Raju I. S. , Newman J. C.
Published: November 2009

The purpose of this paper is to present stress-intensity factor influence coefficients for a wide range of semi-elliptical surface cracks on the inside or outside of a cylinder. The crack surfaces were subjected to four stress distributions: uniform, linear, quadratic, and cubic. These four solutions can be superimposed to obtain stress-intensity factor solutions for other stress distributions, such as those caused by internal pressure and by thermal shock. The results for internal pressure are given herein. The ratio of crack depth to crack length from 0.2 to 1; the ratio of crack depth to wall thickness ranged from 0.2 to 0.8; and the ratio of wall thickness to vessel radius was 0.1 or 0.25. The stress-intensity factors were calculated by a three-dimensional finite-element method. The finite-element models employ singularity elements along the crack front and linear-strain elements elsewhere. The models had about 6500 degrees of freedom. The stress-intensity factors were evaluated from a nodal-force method. The present results were also compared to other analyses of surface cracks in cylinders. The results from a boundary-integral equation method agreed well (±2 percent), and those from other finite-element methods agreed fairly well (±10 percent) with the present results.
Elastic-Plastic Fracture of Cylindrical Shells Containing a Part-Through Circumferential Crack
Authors: Ezzat H. , Erdogan F.
Published: November 2009

In this paper the problem of fatigue crack propagation and ductile fracture of a cylindrical shell containing a macroscopic circumferential flaw is considered. The main interest in the study is in applications to line pipes and other cylindrical containers under secondary axial stresses in addition to the primary stresses coming from the internal pressure. The stress intensity factor for the part-through crack used in analyzing and correlating the fatigue crack propagation rate is obtained by using a line spring model in conjunction with Reissner’s shell theory. To analyze the ductile fracture instability and to correlate the experimental and theoretical results, the crack mouth opening displacement is used as the parameter. The experiments were performed on 20-in-dia (o.d.) and 0.34-in-thick X60 steel pipes. A 0.025-in-wide part-through circumferential flaw was introduced into the pipes as a crack starter which were then tested under four-point bending. The limited data on fatigue crack propagation give the expected result, namely that the crack propagation rate in pipes may be predicted from the fatigue results performed on simpler geometries provided the stress intensity factors in pipes are calculated with sufficient accuracy. The ductile fracture results show that the technique based on the asymptotic behavior of COD may be quite useful to determine a conservative estimate of the fracture instability load.
Qualification of Induction Heating Stress Improvement for Mitigation of Stress Corrosion Cracking
Authors: Hughes N. R. , Diaz T. P. , Pestanas V. V.
Published: November 2009

This paper describes the efforts toward qualification of induction heating stress improvement (IHSI) for mitigation of intergranular stress corrosion cracking (IGSCC) in Boiling Water Reactor (BWR) piping. The IHSI process, which is applied to piping after it is fully erected, produces compressive residual stresses on the pipe inside surface in the vicinity of the weld heat affected zone (HAZ). The creation of these compressive stresses has been confirmed by surface and through-wall strain gage and X-ray diffraction residual stress measurements on 4, 10, and 16-in. dia Schedule 80 welded and IHSI treated pipes. Confirmation of increased resistance to IGSCC due to the IHSI process has been accomplished by full-sized 4-in-dia pipe tests in General Electric’s Pipe Test Laboratory. The pipe test utilized an environment of oxygenated high-purity water at 288°C (550°F). Axial loads were applied which exceeded the material 288°C yield strength.
Response of Containment Vessels to Explosive Blast Loading
Authors: Karpp R. R. , Duffey T. A. , Neal T. R.
Published: November 2009

The response of steel containment vessels to the blast loading produced by the detonation of high explosives is investigated by experiments, computations, and analysis. The vessels are thin-wall shell structures that are nearly spherical. All explosive charges are solid spheres, centrally initiated and centrally positioned within the vessels. Most of the work concerns vessels that contain, in addition to the explosive charge, air at ambient or reduced pressures. One-dimensional, Lagrangian, finite-difference calculations are used to study the blast phenomenon and the details of the loading pulse applied to the vessel wall. The results are verified by comparisons with pressure gage records. In addition, vessel response to the pressure loading is calculated by both finite-difference and finite-element computer codes. The two-dimensional motion, which occurs after significant wave interactions have taken place in the test vessels, can be simulated, with reasonable accuracy, by finite-element calculations.
Dynamic Elastic-Plastic Behavior of Circumferential Cracks in a Pipe Subject to Seismic Loading Conditions
Authors: Griesbach T. J.
Published: November 2009

An analytical study is performed to investigate the structural stability, and inherent integrity, of a Pressurized Water Reactor primary coolant loop cold leg pipe containing a through-wall circumferential crack. The purpose of this study is to gain a better understanding of the mechanisms and extent of crack opening behavior in a real piping system, and, thus, establish the basis for improved pipe break criteria. Cracks extending one-half the circumference or greater are considered in the pipe. Combined operating pressure plus external seismic loads are applied simultaneously to cause a maximum crack opening effect. A dynamic elastic-plastic analysis is performed to calculate stress intensity factors at the crack tip. The results are compared with experimental fracture toughness data to assess the material’s capability to resist crack extension. A fatigue crack growth study is also performed to determine the range of initial flaw sizes which could grow and extend during normal operation to threaten the integrity of the cold leg pipe.
Optimizing Cylindrical and Spherical Pressure Vessels Containing Ideally Behaving Gases and Solid Inserts
Authors: Arbel A. , Eliezer D.
Published: November 2009

Expressions were derived for the minimum outer radii of thick-walled cylindrical and spherical pressure vessels which contain a given amount of ideally behaving gas and a solid insert.
Fracture Mechanics Data Deduced From Thermal-Shock and Related Experiments With LWR Pressure Vessel Material
Authors: Cheverton R. D. , Canonico D. A. , Iskander S. K. , Bolt S. E. , Holz P. P. , Nanstad R. K. , Stelzman W. J.
Published: November 2009

Thermal-shock experiments with steel cylinders have been conducted at ORNL to investigate the behavior of long axial inner-surface flaws during loading conditions similar to those imposed by a PWR LOCA. The scope of the three most recent experiments was dictated by results of the PWR-LOCA fracture-mechanics analysis and included: 1) initiation and arrest of shallow and deep flaws, 2) a series of initiation-arrest events with deep penetration of the wall, 3) long crack jumps, 4) arrest in a rising K1 field, and 5) warm prestressing. For the purpose of designing the experiments and evaluating their results, the static initiation and arrest toughness curves were determined for the test cylinders, and this was done using compact specimens. The experiments demonstrated WPS and arrest in a rising K1 field and indicated that LEFM is valid for thermal-shock loading.
An Analysis of Dynamic Fracture in an Impact Test Specimen
Authors: Nishioka T. , Perl M. , Atluri S. N.
Published: November 2009

Numerical simulations of fast fracture in four cases of dynamic tear test experiments on 4340 steel are performed using a moving singular finite element method. The experimentally measured crack propagation histories are used as input data to the so-called generation phase simulations to determine the dynamic stress intensity factor histories. In most numerical analyses of dynamic fracture specimens, the load and support points have been treated as fixed boundary conditions. In the present paper, more realistic boundary conditions (contact/no-contact), in which the specimen can separate from the tup and the supports are introduced. The results are also discussed in the light of current controversies surrounding the dynamic fracture toughness properties governing crack propagation under impact loading.
On the Plastic and Viscoplastic Constitutive Equations—Part I: Rules Developed With Internal Variable Concept
Authors: Chaboche J. L. , Rousselier G.
Published: November 2009

The description of monotonic and cyclic behavior of material is possible by generalizing the internal stress concept by means of a set of internal variables. In this paper the classical isotropic and kinematic hardening rules are briefly discussed, using present plastic strain tensor and cumulated plastic strain as hardening variables. Some additional internal variables are then proposed, giving rise to many possibilities. What is called the “nonlinear kinematic hardening” leads to a natural description of the nonlinear plastic behavior under cyclic loading, but is connected to other concepts such as the Mroz’s model, limited to only two surfaces, and similarities with other approaches are pointed out in the context of a generalization of this rule to viscoplasticity.
Stress Redistribution During Annealing of a Multi-Pass Butt-Welded Pipe
Authors: Josefson B. L.
Published: November 2009

The reduction of welding stresses during some standard post-weld heat treatments (PWHT) is numerically determined for a multi-pass butt-welded pipe made of a micro-alloyed C-Mn steel. Most of the stress reduction is found to occur during heating to the holding temperature. The further reduction obtained during the subsequent holding period is significant only for holding temperatures above 550°C. Both welding stresses and stresses during annealing were calculated by use of the FE-method assuming rotational symmetry. Experiments performed on a welded pipe indicate that the assumption of rotational symmetry is justified for the welding residual stress field, but not for the transient stress field present during welding of each pass.
Seismic Analysis of Structures With Coulomb Friction
Authors: Shah V. N. , Gilmore C. B.
Published: November 2009

A modal superposition method for the dynamic analysis of a structure with Coulomb friction is presented. The finite element method is used to derive the equations of motion, and the nonlinearities due to friction are represented by pseudo-force vector. A structure standing freely on the ground may slide during a seismic event. The relative displacement response may be divided into two parts: elastic deformation and rigid body motion. The presence of rigid body motion necessitates the inclusion of the higher modes in the transient analysis. Three single degree-of-freedom problems are solved to verify this method. In a fourth problem, the dynamic response of a platform standing freely on the ground is analyzed during a seismic event.
Stress Analysis of Nozzles in Cylindrical Vessels With External Load
Authors: Steele C. R. , Steele M.-L.
Published: November 2009

The analysis is carried out for a cylindrical vessel with a nozzle subjected to external loading consisting of longitudinal and circumferential moments and radial force. The Flu¨gge-Conrad solutions with the Sanders-Simmonds concentrated force solution are utilized for a local analysis, to which asymptotic approximations for the effect of the vessel length and continuity around the vessel circumference are added. This is incorporated in a computer code FAST for which set up and run times are minimal for a given case of geometry and load. The comparison with experimental results is about as good as can be expected for eight models, with parameters in the ranges: 50 ≤ D/T ≤ 2530, 0.01 ≤ d/D ≤ 0.5, and 6.5 ≤ d/t ≤ 240. Hence, the calculation should be useful for an improvement in nozzle design. Example curves and tables of stress factors are included.
Experiments on the Determination of Immersed Shell Structure Mobilities via Scale Modeling
Authors: Sattinger S. S.
Published: November 2009

Experiments were conducted to confirm scaling relations for structural frequency response functions as applied to immersed shell structures using same-material, same-liquid scale models. Accelerance (acceleration/force) frequency response magnitude data were acquired for full-scale and half-scale versions of a fixed-free open cylinder mounted in a rigid vessel. The data confirmed that corresponding frequencies in the model and prototype were in proportion to the inverse of the geometric scale. The peak accelerance magnitudes were normalized by damping to form quantities which should scale despite differences in the corresponding modal damping values. Discrepancies in some of these normalized magnitudes coincided with angular mismatches in mode shapes attributed to minor manufacturing differences in the specimens. Thus, peak frequency responses for a prototype immersed shell structure can be estimated from scale model measurements if typical prototype damping values are known, but the locations of corresponding responses may differ between the model and the prototype in some cases.
A Simplified Method for the Inelastic Analysis of Structures Under Cyclic Loadings
Authors: Tribout J. , Inglebert G. , Casier J.
Published: November 2009

This paper discusses a simplified method which was proposed a few years ago by J. Zarka and J. Casier to obtain a straightforward evaluation of the total inelastic strain which accumulates in a structure under cyclic loadings when shakedown occurs for a linear kinematic hardening material. The theoretical basis is recalled and an example of the application of the method is given which underlines its efficiency.
The Stress Analysis of Rectangular Structures Subjected to Internal Pressure
Authors: Carter A.
Published: November 2009

An analytical procedure is presented which the author developed several years ago. This is compared with the ASME Code procedure which is shown to be deficient.
Development of Engineering Codes of Practice for Corrosion Fatigue
Authors: Scott P. M. , Tomkins B. , Foreman A. J. E.
Published: November 2009

The recognition that time-dependent effects of aqueous corrosion can have a large influence on fatigue failure in carbon and low alloy steels for nuclear reactor pressure vessels is having an important influence on the continuing process of revision and improvement of design and inspection codes. The contrasting requirements of engineering codes for design purposes or for in-service inspection purposes are discussed. The critical assumptions in each are highlighted and illustrated with examples incorporating recent improvements in the mechanistic understanding of the development of corrosion fatigue failure. The consequences of adopting a crack-tolerant approach in the design phase, as distinct from the evaluation of defects found in service, are also critically examined.