bluuebunny/crossref_metadata_2025 huggingface dataset:
3-D Stress Intensity Factors due to Autofrettage for an Inner Radial Lunular or Crescentic Crack in a Spherical Pressure Vessel
Authors: Perl M. , Steiner M. , Perry J.
Published: November 2015

Three dimensional Mode I Stress Intensity Factor (SIF) distributions along the front of an inner radial lunular or crescentic crack emanating from the bore of an autofrettaged spherical pressure vessel are evaluated. The 3-D analysis is performed using the finite element (FE) method employing singular elements along the crack front. A novel realistic autofrettage residual stress field incorporating the Bauschinger effect is applied to the vessel. The residual stress field is simulated in the FE analysis using an equivalent temperature field. SIFs for three vessel geometries (R0/Ri=1.1, 1.2, and 1.7), a wide range of crack depth to wall thickness ratios (a/t=0.01–0.8), various ellipticities (a/c=0.2–1.5), and three levels of autofrettage (e=50%, 75%, and 100%) are evaluated. In total, about two hundred and seventy different crack configurations are analyzed. A detailed study of the influence of the above parameters on the prevailing SIF is conducted. The results clearly indicate the possible favorable effect of autofrettage in considerably reducing the prevailing effective stress intensity factor i.e., delaying crack initiation, slowing crack growth rate, and thus, substantially prolonging the total fatigue life of the vessel. Furthermore, the results emphasize the importance of properly accounting for the Bauschinger effect including re-yielding, as well as the significance of the three dimensional analysis herein performed.
Statistical Performance Evaluation of Spring Operated Pressure Relief Valve Reliability Improvements 2004 to 2014
Authors: Watson Holly L. , Gross Robert E. , Harris Stephen P.
Published: November 2015

The United States Department of Energy’s Savannah River Site (SRS) in Aiken, South Carolina, is dedicated to promoting site-level risk-based inspection (RBI) practices in order to maintain a safe and productive work environment. Inspecting component parts of operational systems, such as pressure relief valves (PRVs), is a vital part of SRS’s safe operating envelope. This paper is a continuation of a SRS program to minimize the risks associated with PRV failures. Spring operated pressure relief valve (SOPRV) test data accumulated over the past ten years resulted in over 11,000 proof tests of both new and used valves. Improved performance is seen for air service valves resulting from changes to the maintenance program. Although, statistically significant improvement was not seen for liquid, gas, or steam service valves, analysis shows that the overall probability of failure on demand is trending down. Current SRS practices are reviewed and the reasons for improved performance are explored.
Comparison of Transition Temperature Shifts From Notch Impact and Fracture Toughness (Master Curve) Testing
Authors: Brumovsky Milan , Kytka Milos , Falcnik Michal
Published: November 2015

Evaluation of integrity and lifetime of reactor pressure vessels is usually based on fracture mechanics approach using empirical correlation between transition temperatures from impact tests and static fracture toughness test results in the form of “design curve”. Moreover, material degradation during operation is also usually monitored by impact surveillance specimen testing under the assumption that shifts in temperature dependencies if impact toughness and static fracture toughness are the same.

To verify this assumption, study of the correlation between these two shifts has been performed on WWER steels — 15Kh2MFA (Cr-Mo-V) and 15Kh2NMFA (Ni-Cr-Mo-V) types. Several sources of results have been used : (a) reconstitution of tested remains of Charpy V-notch impact test specimens from irradiated programs was performed to obtain pre-cracked Charpy size specimens for three point bending type fracture toughness testing, (b) comparison of tests results from surveillance programs irradiated by similar fluences, (c) experimental irradiation programs with accelerated irradiation in research reactor.

Additionally, some results from the recent study of irradiation embrittlement of high nickel weld are included — its behavior shows to some extraordinary tendency.

Thanks to the use of reconstitution, both series of specimen were irradiated under the same conditions — temperature and neutron fluence and comparison is reliable. Results show that transition temperatures from fracture toughness testing are larger than those from Charpy impact tests. Similar results have been obtained also for other two groups of results.
Effect of Thermal Cutting Methods on the Fatigue Life of High Strength Structural Steel S690Q
Authors: Garcia Tiberio , Cicero Sergio , Álvarez Jose A. , Carrascal Isidro , Martin-Meizoso Antonio
Published: November 2015

This paper analyzes the effect of different cutting methods on the fatigue life of high strength steel S690Q. The research covers three cutting methods (oxy-fuel, plasma and laser) and two specimen geometries: plain specimens with rectangular sections and cut edges, and specimens with machined edges and a cut hole in the middle section. All the specimens were conducted to failure by applying fatigue cycles, the stress ratio (R) being 0.1, and the corresponding S-N curves were obtained for each combination of cutting method and specimen geometry. Measurements of roughness and hardness have been performed in order to explain the influence of the cutting method on the fatigue life of this particular steel. Fatigue results have been compared with the predictions provided by current fatigue standards, analyzing the possibility of extrapolating their S-N curves, focused on oxy-fuel cuts, to plasma and laser cuts.
Elasto-Plastic Properties in Dissimilar Metal Weld Junctions: Stress-Strain Curves Determination for Constitutive Materials
Authors: Bourgeois M. , Ancelet O. , Chapuliot S.
Published: November 2015

Within the framework of European project MULTIMETAL (Structural performance of multi-metal component), several fracture tests on different types of multi-material specimens have been performed. Present fracture toughness standard methods, e.g. ASTM E 1820 are not directly intended for Dissimilar Metal Weld (DMW). Therefore further investigations are needed in order to define the best practice in fracture mechanical tests and their analysis for DMWs.

Specimens are taken from welded plates: a narrow gap Inconel DMW junction between ferritic and austenitic stainless steels, designed and delivered by AREVA France. The aim of this work is to provide guidelines for the determination of DMW fracture properties. For that purpose, fracture specimen needs to be modelled by FE. The first task, which is the purpose of that paper, is the determination of the mechanical properties in terms of stress-strain curve of all DMW constitutive materials: austenitic stainless steel, ferritic steel, heat affected zone of the ferritic steel zone and Nickel alloy zone properties.

Conventional techniques for tensile test are not able to provide the tensile curve of the different materials constituting a weld joint. Image correlation techniques are well suitable but imply too long and difficult work for the images analysis. Therefore CEA has developed an intermediate solution based on laser sensors which provides a complete profile of the specimen during the tensile test. Using Bridgman equations, the stress and strain can be deduced from the measurement of the shape of the specimen (reduction of section but not only…). This innovative device has been used with new developments using local Bridgman equations in the post-processing of measurements. This allows to access to the material behaviour of several materials with only one specimen.

Numerical interpretation using FE methods is presented and confirms the material behaviour determined from the experimental work using Bridgman equations assumptions.

Finally, this combined experimental and numerical work has provided material data relative to all constitutive materials of the DMW junction. A hardened area in stainless steel material due to the welding process has been pointed out, and the heat affected zones of the ferritic material have been characterized in terms of stress-strain curves. The next stage of the project is to carry out tests on fracture specimens and to model these multi-materials specimens by FE. The gradient of elasto-plastic properties is now available for this next step.
Analytical Expressions for Liquid-Column Velocities in Pipelines With Entrapped Gas
Authors: Tijsseling Arris S. , Hou Qingzhi , Bozkuş Zafer
Published: November 2015

High pressures and high temperatures may arise in pipelines when a liquid column is suddenly accelerated into a gas pocket trapped at a closed end. A mass oscillation occurs that is described by nonlinear equations for both liquid and gas. Analytical expressions are derived for the uniform velocity of the liquid column, from which pressures and gas temperatures follow. The obtained results are validated against theoretical and experimental results published by fellow researchers.
Ductile Fracture Simulation Considering Strain Rate Loading Effect
Authors: Nam Hyun-Suk , Kim Ji-Soo , Kim Yun-Jae , Kim Jin-Weon , Oh Chang-Young
Published: November 2015

This paper is based on a ductile failure simulation under dynamic loading conditions using finite element (FE) analyses. Recently a simple finite element method in a quasi-static test has been proposed to implement fracture simulation based on the well-known stress modified fracture strain model. The stress-modified fracture strain model is determined to be incremental damage in terms of stress triaxiality and fracture strain for dimple fracture from tensile test result with FE analyses technique. Since dynamic loading effect is especially important to assess pipe with crack-like defect, this work propose the integrated model which combines quasi-static with dynamic loading effect. In order to validate stress-modified fracture strain model in dynamic loading conditions, this paper compares results of FE analysis using proposed method with strain dependent smooth bar tests and notch tensile tests using Johnson-Cook equation. In conclusion, the stress-modified fracture strain model criterion can be calibrated by FE analyses with strain rate dependent fracture toughness test results.
FEM Analysis and Preload Evaluation of Bolted Joints Subject to Low Temperature
Authors: Yan Yi , Wen Menggang , Li Yun
Published: November 2015

Bolted joints are broadly used in various industrial products. Especially in chemical engineering, the reliability of bolted joints can have a significant influence on the safety of chemical systems. In some fields, such as liquefied natural gas (LNG) industry, equipment usually works in low temperature (−162°C). Different materials with various thermal expansion rates are usually used in bolted joints; Therefore the preload and stress distribution of bolted joints in low temperature can change apparently due to the different axial and radial thermal deformation. If the preload design in normal temperature is inappropriate, the bolted joints may either encounter relaxation or over-tightening in working temperature. In this study, a theoretical analysis is proposed in order to evaluate the appropriate preload selection of bolted joints work in low temperature. FE analysis is made to examine the accuracy of the theoretical formula. The result shows that the error is less than 10% in most cases. The stress distribution on the bolt thread region is studied and the result shows that the maximum tensile stress on the bolt thread region is much higher than in non-thread region. Availability and safety should be both considered in preload selection of bolted joints working in low temperature. Finally the effect of radial thermal deformation difference is discussed when the thermal expansion rate difference is high. The effect of radial thermal deformation difference should not be neglected in some cases.
Overview of Recent NUGENIA Activities Particularly in Relation to Structural Integrity
Authors: Sharples John , Keim Elisabeth
Published: November 2015

NUGENIA, an international non-profit association founded under Belgian legislation and launched in March 2012, is dedicated to nuclear research and development (R&D) with a focus on Generation II and III power plants. NUGENIA is the integrated framework between industry, research and safety organisations for safe, reliable and competitive nuclear power production, and is aimed at running an open innovation marketplace, to promote the emergence of joint research and to facilitate the implementation and dissemination of R&D results. The technical scope of NUGENIA consists of eight technical areas. One of these areas, Technical Area 4, is associated with the structural integrity assessment of systems, structures and components.

A brief overview of recent NUGENIA activities in general is provided in this paper and a specific focus is given on developments in relation to Technical Area 4.
Residual Stresses in Clad Nuclear Reactor Pressure Vessel Steels: Prediction, Measurement and Reconstruction
Authors: Serasli Karim , Coules Harry , Smith David
Published: November 2015

Most residual stress measurement methods are limited in terms of their stress and spatial resolution, number of stress tensor components measured and measurement uncertainty. In contrast, finite element simulations of welding processes provide full field distributions of residual stresses, with results dependent on the quality of the input conditions. Measurements and predictions are often not the same, and the true residual stress state is difficult to determine. In this paper both measurements and predictions of residual stresses, created in clad nuclear reactor pressure vessel steels, are made. The measurements are then used as input to a residual stress mapping technique provided within a finite element analysis. The technique is applied iteratively to converge to a balanced solution which is not necessarily unique. However, the technique aids the identification of locations for additional measurements. This is illustrated in the paper. The outcomes from the additional measurements permit more realistic and reliable estimates of the true residual state to be made. The outcomes are compared with the finite element simulations of the welding process and used to determine whether there is a need for additional input to the simulations.
Cyclic Deformation at the Tip of Inclined Cracks in Steel Plates
Authors: El Emam Hesham M. , El-Sisi Alaa Eldin M. , Salim Hani A. , Sallam Hossam E. M.
Published: November 2015

The evaluation of the crack tip deformation is essential to the estimation of crack growth under either static or cyclic loading. A 3-D elastic-plastic finite element analysis was developed to simulate the crack tip deformation along mixed mode inclined edge cracks in a steel plate subjected to either monotonic or cyclic loading at selected R-ratios. Bilinear kinematic hardening model was used to describe the material behavior. The development of the monotonic (Δm) and cyclic (Δc) crack tip plastically deformed zones and opening displacements were traced to find the effect of the crack inclination angle, which significantly affected the size and shape of the crack tip plastic zone. The finite element results compared well with the analytical results based on modified Dugdale’s model. It was observed that Mode II has a significant effect on the plastic zone in the case of equal inclined crack length (EICL), i.e., Mode II increases as the crack angle decreases. Also, it is interesting to note that for the EICL, the magnitude of Δc is delayed to appear with decreasing the inclination angle. Whereas, the variation of monotonic and cyclic plastic zone size in the equal crack horizontal projection (ECHP) case is not affected by the crack inclination angle. Furthermore, it was observed that the static crack tip opening displacement (CTOD) and the cyclic CTOD are independent of the crack inclination angle.
Models of the Temperature Dependence and Scatter in J-R and J0.1 for Ferritic Reactor Pressure Vessel Steels
Authors: Kirk Mark , Erickson Marjorie , Stevens Gary
Published: November 2015

At the 2014 ASME Pressure Vessel and Piping Conference, these authors and others presented a paper that drew together a number of models describing the fracture toughness of ferritic reactor pressure vessel (RPV) steels. That paper summarized models of both the temperature dependence and scatter in a number of fracture toughness metrics (i.e., KJc, KIa, JIc, and J0.1). That paper also provided equations that quantify the interrelationships between these toughness metrics, and how these interrelationships are affected by hardening. Significantly, all of these models and interrelationships are linked via a single parameter: the Master Curve index temperature, To, which can be measured as described in ASTM Standard Test Method E1921. Work is currently underway within the ASME Section XI Working Group on Flaw Evaluation (WGFE) to develop a revision to Code Case N-830 that incorporates all of these models, and provides information on how to apply them in a flaw evaluation. As part of that work, an effort was initiated to augment these models by the addition of a model that can be used to predict the temperature variation of, and the scatter in, J-R curve behavior. A J-R curve model is also expected to support on-going WGFE efforts to in development of acceptance criteria for flaws in ferritic components operating in the upper shelf temperature range.

The work presented in this paper provides a model of the J-R behavior of ferritic RPV steels. When combined with other fracture toughness models to be published in Code Case N-830-1, this model allows prediction of the mean J-R curve, confidence bounds on the mean, and the temperature dependence of J-R all based only on input of To. The J-R model described herein has equivalent or better accuracy to other models described in the literature, and generally has fewer fitting parameters than those other models. Because the full J-R curve is predicted, this model is also useful for prediction of J0.1.
Applicability of Fracture Toughness Curves Developed for Japanese Pressure Vessel Steels to Structural Integrity Evaluation
Authors: Yoshimoto Kentaro , Hirota Takatoshi , Sakamoto Hiroyuki
Published: November 2015

Surveillance tests have been conducted on Japanese Pressurized Water Reactor (PWR) plants for more than 40 years to monitor irradiation embrittlement of reactor pressure vessel (RPV) beltline materials. Fracture toughness specimens are contained as well as tensile and Charpy impact specimens in a surveillance capsule and utilized for structural integrity evaluation. Therefore, a lot of fracture toughness data have been obtained by fracture toughness tests using such as Compact Tension (CT) and Wedge Opening Loading (WOL) specimens. More than one thousand data have been accumulated for both unirradiated and irradiated materials until 2013. Additionally, in terms of fracture toughness, Master Curve (MC) concept has been widely used for fracture toughness transition curve expression of ferritic steels. Considering such a situation, the new fracture toughness curves using Tr30, which denotes Charpy V-notch 30ft-lb transition temperature, as an indexing parameter were developed based on MC concept depending on product form for Japanese RPV steels in 2014.

In this study, applicability of the newly developed curves of Japanese RPV steels to structural integrity evaluation is investigated. Especially, this paper focused on conservatism of the curves and the adequate margin to be added in evaluation of RPV integrity employing statistical methodology.
Development of an Advanced PWR Reactor Internals System Finite Element Model for Flow-Induced Vibration Analyses
Authors: Palamara Matthew J. , Smith Stephen D. , Walker Adam P. , Basel Richard A. , Meyer Gregory A.
Published: November 2015

The reactor vessel internals (RVI) are located within the reactor vessel, which is part of the reactor coolant system (RCS) loop in Westinghouse nuclear plant designs. Historically, the coolant passing through the RCS loop has been highly turbulent and has generated significant turbulence-induced excitation (TE) for the RVI. In an effort to analytically quantify the response of RVI structures due to TE for new designs, a methodology is employed which combines both first principle concepts as well as operational experience. As part of this process, TE-induced forcing functions are developed based upon the numerous flow fields around the components of interest. After the TE-induced forcing functions are developed, they are applied to a system finite element model (SFEM), in a transient dynamic finite element analysis to capture dynamic system-level interactions. To benchmark the response of the numerical model, both narrowband and broadband model responses are compared to empirical data extrapolated from model-scale flow-induced vibration test results. This comparison shows a strong agreement between the empirical data and the SFEM, validating that the dynamic response and system interactions of RVI structures due to TE can be accurately characterized through numerical simulation of the system.
Master Curve Testing of Reactor Pressure Vessel Multilayer Welding Seams
Authors: Viehrig Hans-Werner , Houska Mario , Altstadt Eberhard
Published: November 2015

Reactor pressure vessel (RPV) multilayer welding seams show an inhomogeneous structure. It raises concerns that the evaluation of non-uniform material might not be amenable to the statistical analysis methods on which the Master Curve approach is based. In particular with regard to weld metals, it can be expected that the cleavage fracture toughness is strongly influenced by the orientation of the Charpy size SE(B) specimen. The T-L oriented SE(B) specimen (axis axial and crack propagation in circumferential direction) comprises of various welding beads along the crack front whereas in a L-S specimen (axis axial and crack propagation through the thickness) the crack tip is located in one welding bead with an approximately uniform structure.

The paper summarises fracture toughness results measured on welding seams of decommissioned and non-commissioned RPVs of WWER type nuclear reactors and the non-commissioned Biblis-C RPV. Specimens of T-L and T-S orientation were tested. The results show, that in general the cleavage fracture toughness values, KJc-1T, follow the Master Curve description. However, the number of KJc-1T data outside the 2% and 98% tolerance bounds is larger than predicted by the underlying model, which indicates non-uniform material.

There is a large variation in the evaluated through thickness T0 values of the investigated multilayer beltline welding seams. Within the sampling range of the surveillance specimens, T0 values vary with a span of 30 to about 60 K depending on the applied welding technology. The fracture toughness strongly depends on the intrinsic weld bead structure. Hence, the position of the fatigue crack tip of the pre-cracked SE(B) specimen at the multilayer welding seam is crucial and defines the cleavage fracture toughness. Modified Master Curve based evaluation procedures like the MC based approach of the SINTAP procedure were applied to get fracture toughness values which are representative for the most brittle fraction the test series.

Despite of the pronounced non-homogeneity of the micro-structure along the crack front of T-L specimens, crack initiation sites are randomly distributed along the crack front. This means that one of the basic assumptions in ASTM E1921, i.e. the uniform distribution of initiation sites, is fulfilled also for the T-L specimens from the multilayer weld metal.
Vibration Spectrum of a Water Pipe Under the Effect of Unsteady Fluid Loading
Authors: Berro Hassan , Moussou Pierre
Published: November 2015

A simplified method for estimating the vibrations of water pipes under the effect of unsteady fluid flows is proposed. The first natural frequencies of water pipes being about some 10 Hz due to standard design rules, and supports being arranged with spans of the order of 5 m, the fluid flow can reasonably be described as incompressible, so that acoustics do not play a significant role within this framework. Assuming for the sake of simplicity that the fluid velocity field is the gradient of a potential, it generates an inertial pressure field along the pipe. Simple equations are derived for describing the fluid flow associated with a given mode shape of the pipe, and coupled equations are provided which link the unsteady fluid flow to the vibrations. A simple test case is provided, which supports the idea that for water pipes, the vibration velocity of the structure and the unsteady fluid velocity are in the same order of magnitude.
Analysis of Dynamic Stress in the Reactor Core Barrel due to the Pressure Pulsations
Authors: Orynyak Igor , Dubyk Iaroslav , Batura Anatolii
Published: November 2015

This article presents vibrations analysis of the reactor core barrel caused by pressure pulsations induced by the main coolant pump. For this purpose, the calculations of the pressure distribution in the annulus between the core barrel and the reactor pressure vessel, bounded above by a separating ring were performed. Using transfer matrix method is obtained the solution of two-dimensional problem of pressure pulsations in the annulus between reactor core barrel and reactor vessel. The calculation results are compared with the pulsation pressure measurements made at commissioning unit 2 of the South Ukraine Nuclear Power Station. The distribution of pressure over the height of core barrel was obtained, which makes possible to estimate its strength for variant deformation of the core barrel as a beam, and in the case of deformation of the core barrel as a shell. The calculation results are used to assess the reliability of core barrel pre-load, which clamps the core barrel flange in place at the top, at full power operating.
The Influence of Creep Strain on Crack Length Measurements Using the Potential Drop
Authors: Tarnowski K. M. , Davies C. M. , Nikbin K. M. , Dean D. W.
Published: November 2015

One of the most common methods for estimating crack extension in the laboratory is electrical potential drop (PD). A key limitation of this technique is that it is sensitive to strains at the crack tip as well as crack extension. When producing J-R curves the onset of crack growth may be identified from a point of inflection on a plot of PD vs. CMOD. For creep crack growth (CCG) tests however, the effects of strain are often ignored. This paper investigates whether a similar method may be applied to CCG testing.

A single CCG test was performed on type 316H stainless steel and a point of inflection, similar to that observed during J-R curve testing was identified. A finite element (FE) based approach was used to investigate this phenomenon further. A 3D sequentially-coupled structural-electrical FE model was used to reproduce the experimental PD vs. CMOD plot up to the point of inflection. The model was capable of predicting the general relationship between strain and PD. It predicted the magnitude of the change in PD to within 30%. A simplified 2D FE model was then used to perform a parametric study to investigate whether a similar trend may be expected for a range of materials. Power law tensile and creep properties were investigated with stress exponents of 1, 3 and 10. The results confirm that a point of inflection should be observable for the range of material properties considered.
A Study of the Effects of Scaling on Structural Integrity Assessment
Authors: Orrock Paulo , Smith David J. , Truman Christopher E.
Published: November 2015

For nuclear welded components the complex nature of the residual stresses involved means it is often advantageous to produce mock-ups in order that the structural integrity and performance may be assessed. The weight and size of these components can make the production of mock-ups prohibitively expensive, and so the use of scaled models is considered here. Numerical analysis and finite element simulations have been carried out to investigate the scaling laws encountered affecting the applied loads, stress fields and crack driving forces that are of interest in the full sized component.

To illustrate the effects of scaling we consider the introduction of a residual stress through prior plastic deformation in rectangular beams of different sizes. A simple scaling law provides the loads required to introduce the same magnitude and distribution of residual stresses in different sized specimens. This is pertinent to uncracked beams. In contrast, if a crack is introduced this scaling law is no longer applicable and the stress intensity factor associated with residual and applied stresses differ for different sized specimens. Alternatively, to create the same crack driving force in different sized specimens different initial residual stress fields are required. The implications of these findings are discussed in the context of future work.
The Effect of Jacket-Side Liquid on the Burst Pressure Estimation of a Jacketed Vessel
Authors: Xu Yu , Young Kuao-John
Published: November 2015

This study is intended to clarify the influence of jacket-side liquid on determining the burst pressure of a jacketed vessel subjected to deflagrations inside the vessel chamber. The influence of jacket-side liquid is modeled as either being nearly incompressible due to its high bulk modulus or sustaining a constant level of jacket chamber pressure. Employing finite element analyses, this paper reveals how jacket-side liquid compressibility affects the interaction between the vessel shell (inner wall) and jacket (outer wall) when the vessel shell is subjected to an internal deflagration. The study results indicate that simply combing the separate burst pressures of the vessel shell and jacket can result in insignificant difference in calculating the burst pressure of the jacketed vessel that is made of ductile materials and has a relatively small gap between the vessel shell and jacket.
An Analytical Solution for Calculating Stresses on Full Encirclement Sleeves Used on Pipes and Pressure Vessels
Authors: Nadarajah Chithranjan
Published: November 2015

Welded full encirclement sleeve repairs are used regularly in petrochemical industries as repairs for piping and pressure vessels. This publication describes a proposed methodology for calculating the stresses on a welded full encirclement sleeve using a simple analytical approximation. The analytical results are compared with finite element results and are found to be in reasonable.
Measurement of Environmental Stress Cracking Resistance (ESCR) Using Notch-Free Specimens
Authors: Jar P.-Y. Ben
Published: November 2015

Transverse loading on a plate specimen has been explored as an alternative method (named plate test) to ASTM D1693 for characterizing environmental stress cracking resistance (ESCR) of polyethylene (PE). The plate test does not require any pre-notch in the specimens to initiate the crack growth. Rather, the crack is generated during the test, initiated by the constraints for lateral contraction in the necking process. This paper introduces the set-up for the plate test, describes the deformation process, presents preliminary results for 4 types of PE, and compares results from the plate test with those from ASTM D1693.
Comparison Between the ASME Code NB-3600 Piping Design Branch Connection Stress Analyses and Finite Element Analyses
Authors: Faraz Umar , Gurdal Robert
Published: November 2015

Stresses in Class 1 branch connections that consist of large bore run pipe with a reinforced branch nozzle should rarely be limited by the run–branch interface stresses. The end of the “branch nozzle – branch pipe” interface is the location on the branch nozzle one would expect to see the limiting stress. Therefore, it is important that reasonable Design Rules are maintained in the ASME Code Section III for the stress analyses of the Class 1 Piping branch connections to avoid over-predicting the “run pipe - branch nozzle” interface stresses. This will allow the analysts to concentrate on load reductions needed in a logical manner.

In Class 1 Piping Design, the calculation of the branch total stress due to the moments is the result of the sum of the stresses from the run moment and of the stresses from the branch moment with these branch moment stresses being calculated using either the branch pipe cross-section or the branch nozzle cross-section. This in itself is already severe, when compared with other Piping Design Rules for branch connections. In addition, starting with the ASME Code year 2002, the branch-side moment stress is based exclusively on the branch pipe cross-section, which leads to a higher moment stress, and this higher moment stress is still absolutely added to the run-side moment stress. As indicated in that ASME Code year 2002 and beyond, this addition is independent of the length of the branch nozzle reinforcement. This leads to total moment stresses that are the sums of moment stresses that do not occur at all at the same location.

The purpose of this technical paper is to compare a) the stresses calculated with the earlier more correct Class 1 Piping methodology from 2001 and before 2001; b) the stresses calculated with the more recent and more severe Class 1 Piping methodology; and c) the stresses from finite-element analyses.

Conclusions are provided on what should be done for the future Class 1 Piping Design methodology of branch connections.
Proposal of Common Rules for Fatigue Crack Growth Law of the JSME Rules on Fitness-for-Service
Authors: Hojo Kiminobu , Itatani Masao , Arai Taku
Published: November 2015

The JSME Codes and Standards Committee have provided many kinds of crack growth rates of SCC and fatigue cracking as Appendix in the code and the code cases. However each code has been separately investigated and there is no common rule among SCC growth rates or fatigue crack growth rates. The working group (WG) members discussed to construct the common rules for fatigue crack growth. Sensitivity study for loading rise time in PWR environment was investigated with slower rise time. Using the proposed common rule, the subgroup (SG) on Evaluation and Standard will transfer the fatigue crack growth rates in the code cases to the code.
Application of Visual Beam Ultrasonic Phased Array in Inspection of Weld in Tubular Node
Authors: Wang Shaojun , Tang Xiaoying , Yu Houde , Qian Yaozhou , Cheng Jun , Wang Jifeng , Huang Yichang
Published: November 2015

Responding to complexity and particularity welding on the geometry of TKY tubular node, this paper constructs mathematical model of tubular joint weld of arbitrary section by simplifying the geometry structure, and draws welded joints and ultrasonic sound beam lines based on the actual specifications in order to solve the problems of low efficiency, positioning difficulty, missing inspection and etc. The computeraided simulation technology can realize the visualization in the beam coverage model of welded joints, which can commendably guide the design of ultrasonic phased array inspection and overcome the blindness of the instrument detection parameters, thus improving the effectiveness and pertinence of the actual detection. Study shows that it is beneficial to enhance the effectiveness of the detection tubular joint weld by employment of Visual beam and ultrasonic phased array technology.
Influence of Specimen Geometry and Strain Rate on Ductile-Brittle Transition Characterisation of Reactor Pressure Vessel Steels Using the Small Punch Technique
Authors: Adams Jack , Hurst Roger C. , Borradaile J. Bryan , Bache Martin R.
Published: November 2015

The small punch (SP) tensile test, originally developed for assessing the integrity of nuclear containments, has seen a renaissance in recent years with the introduction of a Code of Practice and a standardisation proposal. For nuclear applications, the extremely low volumes of material that are required allows specimens to be manufactured from quasi-destructive scoop samples, surveillance specimens or even previously tested Charpy specimens. The low volume of material also alleviates the health and safety requirements and the cost associated with testing active materials. By assessing the energy absorbed before fracture, it is possible to build an entire SP ductile-brittle transition curve using less material than is required for a single Charpy test.

Small punch testing has been performed on SA 508-3 NESC-1 spinning cylinder material to establish ductile-brittle transition data, for comparison to that obtained by conventional Charpy impact test techniques. Multiple SP ductile-brittle transition curves have been constructed, building upon the framework of the existing Code of Practice. Novel geometries and associated machining techniques employed to incorporate notches into the surface of the SP specimen, and also the application of relatively high strain rates have been investigated. Post-test fractography illustrates the influence of both stress raising features and strain rate on small punch fracture behaviour.
Optimizing Measurement of Fatigue Crack Growth Relationships for Cr-Mo Pressure Vessel Steels in Hydrogen Gas
Authors: Somerday Brian , Bortot Paolo , Felbaum John
Published: November 2015

The objective of this study was to explore an approach for measuring fatigue crack growth rates (da/dN) for Cr-Mo pressure vessel steels in high-pressure hydrogen gas over a broad cyclic stress intensity factor (ΔK) range while limiting test duration, which could serve as an alternative to the method prescribed in ASME BPVC VIII-3, Article KD-10. Fatigue crack growth rates were measured for SA-372 Grade J and 34CrMo4 steels in hydrogen gas as a function of ΔK, load-cycle frequency (f), and gas pressure. The da/dN vs. ΔK relationships measured for the Cr-Mo steels in hydrogen gas at 10 Hz indicate that capturing data at lower ΔK is valuable when these relationships serve as inputs into design-life analyses of hydrogen pressure vessels, since in this ΔK range crack growth rates in hydrogen gas approach rates in air. The da/dN vs. f data measured for the Cr-Mo steels in hydrogen gas at selected constant-ΔK levels demonstrate that crack growth rates at 10 Hz do not represent upper-bound behavior, since da/dN generally increases as f decreases. Consequently, although fatigue crack growth testing at 10 Hz can efficiently measure da/dN over a wide ΔK range, these da/dN vs. ΔK relationships at 10 Hz cannot be considered reliable inputs into design-life analyses. A possible hybrid approach to efficiently establishing the fatigue crack growth rate relationship in hydrogen gas without compromising data quality is to measure the da/dN vs. ΔK relationship at 10 Hz and then apply a correction based on the da/dN vs. f data. The reliability of such a hybrid approach depends on adequacy of the da/dN vs. f data, i.e., the data are measured at appropriate constant-ΔK levels and the data include upper-bound crack growth rates.
Applicability of Net-Section Collapse Load Approach to Maximum Load Predictions of Multiple Circumferential Cracked Pipes: Numerical Study
Authors: Lee Myeong-Woo , Kim Seung-Jae , Lee So-Dam , Jeon Jun-Young , Kim Yun-Jae
Published: November 2015

To estimate maximum load-carrying capacity of pipes with multiple circumferential cracks, the net-section collapse load approach has been proposed. Although the proposed method has been validated against pipe test data, experimental data are quite limited due to large sets of variables to be considered. In this paper, a numerical method is proposed to generate virtual pipe test data with wide ranges of crack geometry and interspacing. To get confidence of the proposed numerical method, it is firstly applied to simulate existing 4-inch diameter schedule 80 pipes with two circumferential cracks. Predicted maximum loads agree well with experimental data. Then the proposed method is applied to generate maximum loads for wider ranges of crack geometry and loading conditions. It is found that the net-section collapse load approach works well for all cases considered.
Streamwise Fluidelastic Instability in a Deformed Rotated Triangular Tube Array With Pitch-to-Diameter Ratio of 1.375
Authors: Keogh Daniel B. , Meskell Craig
Published: November 2015

A study of the surface pressure distribution of a cylinder in a deformed rotated triangular tube array with pitch-to-diameter ratio of 1.375 has been performed. This work was motivated by the failure of steam generators in San Onofre Nuclear Generating Station (SONGS) in Southern California, which occurred as a result of fluidelastic instability in the streamwise direction. This particular failure occurred in the U-bend region of the steam generators. The presence of anti-vibration bars (AVB) in this region prevent the tubes from experiencing fluidelastic insatiably (FEI) in the transverse direction but offer little support in the streamwise direction. This study analyses the streamwise direction vibration of the tubes in the U-bend region using experimental data and a simplified quasi-steady model. Surface pressure data was gathered in a draw down wind tunnel for a range of flow velocities using an instrumented cylinder with 36 pressure taps around the circumference of the cylinder at midplane. The instrumented cylinder was mounted in the 4th and 6th rows of the tube array. The effect of streamwise displacement of up to ±10% of the instrumented tube and its neighbours was investigated. Although bi-stable flow was detected, only the forces in the lift direction were substantially affected. The displacement dependent drag forces acting on the instrumented cylinder were determined by integrating the pressure distributions with respect to angle. Hence the coupled fluid stiffness matrix could be assembled for each flow velocity studied. The effect of Reynolds number was also investigated for a number of scenarios.
Lessons From an Operational Small Leakage at Tsuruga Nuclear Power Station
Authors: Kobayashi Hiroyuki , Urabe Osamu , Fujino Takushi
Published: November 2015

Operational small leakage is occasionally observed in a nuclear power plant, and the leak forces an operator to decide whether to shut down the plant or not. Even if the leakage is just a little, it might draw the considerable attention in the society, so that the operator sometimes gets into the situation to judge more severely than technical judgment. Furthermore, at the time of plant restart and the system leak test just after maintenance, even the operator doesn’t accept any leakage considering the long management for the leakage up to the next outage.

On the other hand, once the operator shut down the plant, it sometimes takes long time to restart again because of the difficulty to obtain new pipes and valves in short time. The temporary repair techniques referred to the JSME code might be able to be applied to maintain the plant operation, however some difficulties exist in a practical process.

One of the authors has faced with many cases in which the operational small leakage had to be dealt at Tsuruga nuclear power station. This paper shows some cases of them and discusses lessons which are related to the codes and standards.
Deformation Characteristics of a High Chromium, Power Plant Steel at Elevated Temperatures
Authors: Golden Brian J. , Li Dong-Feng , Tiernan Peter , Scully Stephen , O’Dowd Noel P.
Published: November 2015

The changing face of power generation requires an improved understanding of the deformation and failure response of materials that are employed in power plants. Important insights can be obtained through microstructurally motivated modelling studies. With the drive for increased efficiency, there is a corresponding drive towards increasing operating temperatures in conventional power plant. With these increasing temperatures, and with the increased flexibility required of modern power plant working in a mixed energy economy, more robust material testing and modelling tools are required to accurately predict the response of power plant steels. This works deals with the development of a material model for a martensitic steel, P91, relevant to the range of temperatures typically seen in a modern power plant. High temperature (20, 400, 500, 600°C) tensile testing at various strain rates was carried out the steel. Tests were taken to failure and the stress strain response recorded. Electron backscatter diffraction (EBSD) is employed to determine the complex microstructure of the P91 material. This information is incorporated within a representative volume element (RVE) and a nonlinear, rate dependent, finite strain crystal plasticity model used to represent the deformation of the material. The material model was calibrated to each temperature and strain rate to give a robust physically based model that has been fully validated through experimental data.
Direct Measurements of Acoustic Damping and Sound Amplification in Corrugated Pipes With Flow
Authors: Golliard Joachim , Belfroid Stefan , Vijlbrief Olav , Lunde Knud
Published: November 2015

The flow-induced pulsations in corrugated pipes result from a feedback loop between an acoustic resonator and the noise amplification at each shear layer in the axisymmetric cavities forming the corrugations. The quality factor of the resonator is determined by the reflection coefficients at the ends of the corrugated pipe and by the damping in the pipe. In this work, the damping of acoustic waves in a set of smooth and corrugated pipes is measured by a direct method.

For these measurements, the tested pipes are placed between two measuring pipes equipped with flush-mounted pressure transducers to allow reconstruction of the acoustic waves with the two-microphone method. Loudspeakers are used to generate acoustic waves, and anechoic terminations allow near reflection-free conditions. The tests are done in air without flow and with flow velocities up to 60 m/s.

The results for the corrugated pipes allow to investigate the influence of the corrugations on the damping. Two cases are considered: Without flow, the visco-thermal damping is increased for the corrugated pipe compared to a smooth pipe of same diameter. When there is a flow in the pipe, the damping results depend strongly on the flow velocity. At certain frequencies which depend on the flow velocity, the damping increases or decreases. The regions of increase or decrease are shown to be at constant ranges of Strouhal numbers. The decrease of the damping can in some cases be such that acoustic waves are amplified through the corrugated pipe. This corresponds to the acoustic source behavior of the shear layers. The measured amplification is compared to the computed source term due to the axisymmetric cavities.
The Effect of Load Frequency on the Temperature Dependence of Fracture Life of Notched Specimens for 9-12Cr Steel Under Creep-Fatigue Conditions
Authors: Shirai Y. , Yokobori A. T. , Sugiura R. , Fukuda T. , Matsumoto D. , Ishikawa H. , Ito K.
Published: November 2015

In order to operate a thermal power plant safely, it is necessary to establish the prediction methods of fracture life for heat-resistant steels which is used in thermal power plant. For the establishment of prediction methods, it is necessary to consider the effects of creep damage and creep-fatigue interaction on the fracture life.

Therefore, in this paper, creep-fatigue tests were conducted on notched specimens of W-added 9-12Cr steels for various temperatures and load frequencies. From these results, the influence of load frequency on temperature dependence of crack growth life for 9-12Cr steels was determined.