bluuebunny/crossref_metadata_2025 huggingface dataset:
Dissimilar Metal Weld Pipe Fracture Testing: Analysis of Results and Their Implications
Authors: Rudland D. , Lukes R. , Scott P. , Olson R. , Cox A. , Shim D.-J.
Published: August 2013

Typically in flaw evaluation procedures, idealized crack shapes are assumed for both subcritical and critical crack analyses. Past NRC-sponsored research have developed estimation schemes for predicting the load-carrying capacity of idealized cracks in nuclear grade piping and similar metal welds at the operating conditions of nuclear power reactors. However, recent analyses have shown that growth of primary water stress corrosion cracks (PWSCC) in dissimilar metal (DM) welds is not ideal; in fact, very unusual complex crack shapes may form, i.e., a very long surface crack that has a finite length through-wall crack in the same plane. Even though some experimental data on base metals exists to demonstrate that complex shaped cracks in high toughness materials fail under limit load conditions, other experiments demonstrate that the tearing resistance is significantly reduced. At this point, no experimental data exists for complex cracks in DM welds. In addition, it is unclear whether the idealized estimation schemes developed can be used to predict the load-carrying capacity of these complex-shaped cracks, even though they have been used in past analyses by the nuclear industry. Finally, it is unclear what material strength data should be used to assess the stability of a crack in a DM weld.

The NRC Office of Nuclear Regulatory Research, with their contractor Battelle Memorial Institute, has concluded an experimental program to confirm the stability behavior of complex shaped circumferential cracks in DM welds. A combination of full-scale pipe experiments and a variety of laboratory experiments were conducted. A description of the pipe test experimental results is given in a companion paper. This paper describes the ongoing analyses of those results, and the prediction of the load-carrying capacity of the circumferential cracked pipe using a variety of J-estimation scheme procedures. Discussions include the effects of constraint, appropriate base metal material properties, effects of crack location relative to the dissimilar base metals, and the limitations of the currently available J-estimation scheme procedures. This paper concludes with plans for further development of J-estimation scheme procedures for circumferential complex cracks in DM welds.
The Combined Effects of Residual Stress and Warm Prestressing on Cleavage Fracture in Steels
Authors: Rosahl Karin , Booker Julian , Smith David
Published: August 2013

Residual stresses (RS) appear in most engineering structures, either because they have been deliberately introduced or they are a by-product of the manufacturing process. Since RS play an important role in increasing and decreasing the possibility of failure, it is necessary that their effect on the integrity of the structure is understood. In the presence of RS, many components are subjected to a variety of prior loading histories. One such case is often associated with warm prestressing (WPS), where the component is subjected to some form of preloading at a temperature higher than operating conditions. The aim here was to explore how WPS, together with RS, might influence the subsequent fracture conditions for cleavage fracture. First, a model for WPS is reconsidered so that it could be used for Monte Carlo (MC) simulations of WPS. Results are compared with experimental data. The model is then adopted to consider the effects of long range residual stress created in fracture samples through an initial misfit. This is done by fitting the sample into a structure, with the new system subsequently being subjected to WPS conditions. The advantage of the system model is that it facilitates the systematic prediction of the interrelationship and interaction between the applied loads and the misfit (or residual) stresses. The results show that tensile RS act to enhance the effects of WPS, and the WPS cycle, in itself, can act to relax the initial residual stress.
Residual Stress Modeling of Induction-Bent Pipes
Authors: Ding Y. , Yetisir M. , McDonald H.
Published: August 2013

The induction bending process using local induction heating is widely used to produce large diameter pipes with relatively small bend radii at low tooling cost. This process was considered for the fabrication of stainless steel feeder pipes for CANDU® reactors instead of cold and warm bending processes. Wall thickness measurements were performed, before and after bending, using an ultrasonic testing method on a number of test bends fabricated with this induction bending process. Residual stress measurements have been performed on a test bend by X-ray diffraction. A numerical model has been developed using LS-DYNA® to predict the residual stress and the deformed shape of these bends. The numerical model has also been used to study the effect of some key input parameters, such as bending speed, bending temperature, process parameters of induction heating and cooling, and the yield strength of the feeder material. This information can be used to improve the bending process such that lower residual stress and more uniform wall thickness can be achieved. In this paper, the simulation work is summarized and the comparison between the simulation results and the measurement data are presented.
High-Accuracy Analysis Methods of Fluid Temperature Fluctuations at T-Junctions for Thermal Fatigue Evaluation
Authors: Qian Shaoxiang , Kanamaru Shinichiro , Kasahara Naoto
Published: August 2013

T-junctions are widely used for fluid mixing in nuclear power and process plants. Temperature fluctuations generated by the mixing of hot and cold fluids at a T-junction can cause thermal fatigue failure. The existing method for evaluating thermal fatigue leads to an over-conservative evaluation in part. CFD/FEM coupling analysis is a useful tool for the more rational evaluation of thermal fatigue.

The present paper aims to verify another high-accuracy difference scheme used for simulating fluid temperature fluctuations at T-junctions for rational evaluation of thermal fatigue. In addition to the high-accuracy numerical methods presented in the previous paper, the TVD 2nd-order upwind difference scheme (2UD) is also used for the CFD analysis. In the present simulation, the TVD 2UD scheme is only applied to calculate the convective term of the energy equation to facilitate the comparison with the previous simulation.

For comparison, the simulation conditions including the geometry of T-junction are the same as those in the experiments in the literature. The simulation results for distributions of time-averaged fluid temperature are very close to the experimental and previous simulation results. Especially, the predicted results of fluid temperature fluctuations of our concern also agree with the experimental and previous simulation results very well. The simulation results indicate that the TVD 2UD scheme is also a high-accuracy numerical method for the simulation of unsteady phenomena, along with the hybrid scheme.
Simulation for a Floating Roof Behavior of Cylindrical Storage Tank due to Wind Load: Part 2 — Sloshing Response Analysis
Authors: Yoshida Shoichi , Kuroda Shinichi , Uejima Hidesaku , Ishida Kazuo , Shiratori Masaki , Sekine Kazuyoshi , Tsuchida Tomohiko , Iwata Katsuki
Published: August 2013

The floating roofs are used in large cylindrical storage tanks to prevent evaporation of oil. The single-deck floating roof, considered herein, consists of a thin circular plate called “deck” attached to a buoyant ring of box-shaped cross section called “pontoon”. The deck plates are deformed to create waves and they are subjected to cyclic bending due to wind load. This phenomenon may lead to initiate fatigue cracks at the welding joints. It is important to know the vibration characteristics of the waves in the deck plate. The authors have reported a CFD analysis of a cylindrical storage tank due to uniform wind flow in another paper. This paper presents the axisymmetric finite element analysis for the sloshing response of the single-deck floating roofs in a cylindrical storage tank subjected to wind load obtained by the CFD analysis. It is assumed that the liquid is incompressible and inviscid, and the roof is linear elastic while the sidewall and the bottom are rigid. The basic vibration characteristics of the waves in the deck plate, such as frequency and amplitude, are investigated.
Cleavage Dynamic Propagation Analysis in a Nuclear Reactor Pressure Vessel Steel Using a High-Speed Camera
Authors: Bousquet Amaury , Marie Stéphane , Bompard Philippe
Published: August 2013

Initiation stage of cracks is considered as a key issue, but more and more component integrity analyses investigate the crack propagation and arrest possibility. This study deals with physical mechanisms of cleavage crack propagation and numerical computations related to brittle fracture. Dynamic effects, involved in unstable cleavage crack propagation, have to be taken into account to properly depict brittle crack propagation, arrest and possible propagation re-initiation events.

Experiments were carried out on thin CT specimens made of 16MND5 PWR vessel steel at five temperatures (−150°C, −125°C, −100°C, −75°C, −50°C). In addition to standard crack gages, an innovative experimental technique has been used to determine crack propagation. By the means of developments on the experimental protocol (improvements of isolation and airtightness of the thermal chamber, optimization of the experimental protocol to eliminate ice in the thermal chamber and in order to have a good acquisition quality), use of a high-speed framing camera was made possible to measure crack propagation on a CT mirror polished surface. This optical device, combined with this optimized experimental process, has allowed the study of straight and branching crack paths with high accuracy. The framing camera (520 000 fps up to 1 100 000 fps) has allowed to have a very accurate estimation of crack speed even up to 1000 m.s−1 and also to detect some phases of crack branching during propagation and phases of arrest-re-initiation. Numerical computations, based on X-FEM and combining a local non linear dynamic approach with a RKR type fracture stress criterion, have been performed to depict experimental crack behavior.

This paper describes this innovative experimentation and the interpretation by FE calculations and SEM observations associated with quantitative 3D optical microscopy.
Benchmarking xLPR Version 1.0 With the PRO-LOCA Version 3.0 Code
Authors: Kurth Robert , Kurth Elizabeth , Young Bruce , Cox Andrew , Olson Rick , Scott Paul , Rudland Dave , Iyengar Raj , Harrington Craig
Published: August 2013

The US Nuclear Regulatory Commission (NRC) in conjunction with the US nuclear power industry under the leadership of the Electric Power Research Institute (EPRI) is developing a new probabilistic fracture mechanics (PFM) code as a means of demonstrating compliance with the 10CFR50 Appendix A, General Design Criterion 4 (GDC-4) requirement that primary system piping exhibit an extremely low probability of rupture. This PFM code, called xLPR (eXtremely Low Probability of Rupture) will be comprehensive by addressing all aspects of the problem, i.e., crack initiation, growth, stability, surface crack detection and leakage detection.

Previously, the NRC, along with two of its contractors, Battelle Memorial Institute and Engineering Mechanics Corporation of Columbus (Emc2), developed a probabilistic fracture mechanics code called PRO-LOCA[1] which was to have been used as a tool for re-evaluating the break frequency versus break size curves developed as part of the technical basis for the transition break size as part of the redefinition of the emergency core cooling system (ECCS) requirements in 10CFR50.46. PRO-LOCA was subsequently developed as part of an international cooperative research program led by Battelle called MERIT (Maximizing Enhancements in Risk-Informed Technology). Today PRO-LOCA is being further developed as part of another international cooperative program called PARTRIDGE (Probabilistic Analysis as a Regulatory Tool for Risk-Informed Decision GuidancE). The focus of this paper is three-fold. First, the relationship between PRO-LOCA and xLPR will be described. Secondly, the enhancements being made to PRO-LOCA will be discussed and compared to xLPR development. Finally, the results of some comparative cases where PRO-LOCA (Version 3.0) was benchmarked against xLPR (Version 1.0) are provided.
Influence and Modeling of Residual Stresses in Thick Walled Pressure Vessels With Through Holes
Authors: Troiano E. , Parker A. P. , Izzo J. H.
Published: August 2013

Thick walled pressure vessels are often autofrettaged in order to impart favorable near bore compressive residual stresses which can significantly increase the life of the vessels. These stresses can be imparted via a thermal shrink process in which there is no loss of residual stresses due to the Bauschinger Effect, or more economically with a mechanical swage or hydraulic overload process in which the Bauschinger Effect is present.

In some cases these vessels have holes bored through the wall in order to take advantage of the escaping gasses for actuation of external peripherals associated with the vessel. These through holes, which can be angled or perpendicular to the centerline of the pressure vessel can significantly reduce the fatigue life of the vessel depending on the wall ratio of the vessel as well as the, angle of inclination of the hole to the centerline of the vessel.

This study utilizes the classic stress based Paris Law fatigue life approach which takes into account the residual stresses as a function of radial location to assess the life of the vessel in the region of both configurations of through holes. It quantifies the concentration of stresses associated with the perpendicular and angled through wall holes, and the amount of pressure that actually enters the hole. The analysis is employed to ensure that the life within these through holes meets or exceeds the safe life of the vessel without holes which has been determined by assuming a log normal distribution from of a sample size of six with the 90% lower confidence bound on the 0.1th percentile of the population.
Practical Evaluation of PTFE Thermal Behavior Using the Hot Blowout Thermal Cycling Test
Authors: Bausman Anita R. , Waterland A. Fitzgerald (Jerry)
Published: August 2013

Differential thermal expansion between polytetrafluoroethylene (PTFE) gasket materials and metallic flange/bolt systems, combined with thermally influenced creep relaxation characteristics of all PTFEs, creates limitations in the ability of some PTFE gasket materials to provide long term, reliable sealing performance in process or thermal cycling applications. ASTM F-36 gasket recovery data is sometimes used to assess a gasket’s thermal cycling capabilities; however, it is a poor means of establishing suitability for cycling performance as it is a short duration, ambient temperature test that measures recovery, or springback, of the gasket after the compressive load has been completely released. In order to provide a direct qualification of thermal cycling performance and capabilities, the Hot Blowout Thermal Cycling (HOBTC) test was developed under the guidance of the PVRC (Pressure Vessel Research Council)Bolted Flange Connection Committee as part of the 1995 PTFE Gasket Protocol. The HOBTC test results provide a practically applicable temperature limit under which the tested material, typically a PTFE, can operate safely. In addition, test data reported graphically provide additional insight about the long term behavior of the PTFE material. This paper reviews the current status of the HOBTC test, in the process of being made into an ASTM standard, and practical application of test results to achieve reliable gasket performance.
Evaluation of Allowable External Pressure for Branch Pipe Connections
Authors: Iwahara Kotaro , Tachi Kenichi , Amano Yoichi , Miyazaki Katsumasa , Tsunokawa Kiyoharu
Published: August 2013

Although the allowable external pressure for branch pipe connections is estimated by evaluation procedure for straight pipe, the applicability of procedure for straight pipe to branch pipe connections has not been clear. The applicability of evaluation procedure for straight pipe to branch pipe connections regarding to evaluation of allowable external pressure evaluation was discussed in this study. The buckling pressure of branch pipe connections was estimated by linear eigenvalue analysis with FEA (Finite Element Analysis). The types of branch pipe connections were T-joints and T-pipes. The range of configurations in branch pipe connections for FEA, such as ratio of outer diameter in main to branch pipe D/d and ratio of outer diameter to thickness in main pipe D/T, were determined by survey of branch pipe connections in the Japanese nuclear power plants. The results of the FEA showed that the buckling strength of branch pipe was found sufficiently to be superior than that of straight piping from comparisons of estimations by FEA for branch pipe connections and those by formula for straight pipe in the design code. It was concluded that the formula for straight pipe is applicable for the evaluation of allowable external pressure for branch pipe connections.
The Combined Weight Function Method Application for the Estimation of the Crack Opening Area for Through Crack in the Shells
Authors: Orynyak Igor V. , Yakovleva Elena S. , Kozlov Volodymyr R.
Published: August 2013

The through–wall crack opening area is one of the main calculation parameters for the “leak before break” analysis of the piping system with postulated through crack. The existing methods for calculation of COA, in fact, consider the shell (pipe) to be a flat body and neglect the linear components across the pipe wall thickness (as in the theory of plate) both of load distribution as well as displacement field. Based on the combining weight function method the simple procedure for determination of approximate expression for the fundamental displacement field under polynomial loading of the crack surfaces in the shell as a sum of the uniform and linear components is proposed. Based on this method the formulas for calculating COA at the polynomial membrane and linear loading are derived. The comparison of the obtained COA values with results existing in the literature is performed for the cylindrical shell with axial and circumferential cracks. The contribution of the linear component of the COA to its total value has been estimated.
Estimation of Remaining Fatigue Life for Elbow Pipe Subjected to Cyclic Overload
Authors: Abe Hisanori , Matsuo Kazuya , Takahashi Koji
Published: August 2013

Low-cycle fatigue tests for STPT410 elbow pipes were conducted under displacement control with and without an internal pressure of 9 MPa. First, preliminary fatigue tests were conducted under constant displacements of ±15, ±20 and ±30 mm. Next, two-step fatigue tests were carried out in which the elbows were first subjected to cyclic displacements of ±30 or ±20 mm, which correspond to cyclic overload, and then subjected to a second displacement of ±20 or ±15 mm until a fatigue crack penetrated. The total usage factor was 0.8∼1.2. Thus, the remaining fatigue life of a given elbow pipe can be predicted by the cumulative fatigue damage rule.
Investigation on Developing Seismic Safety Evaluation Method Using Elasto-Plastic Analysis
Authors: Nakamori Tomohito , Kojima Nobuyuki , Ueda Yuya , Shimizu Hiroshi , Monde Masatsugu , Okamoto Hiromu , Ikeda Kazutoyo , Hosotani Terushige , Matsuzaki Daichi , Ishihama Kiyoshi
Published: August 2013

As seismic motion level for seismic resistant designing has been increased, usual tolerance is no longer enough in the existing domestic PWR and BWR plants.

In this study, the authors had an eye on devices supported by four legs in the existing domestic PWR and BWR plants, and established a reasonable earthquake-proof evaluating safety method compared to the original method (JEAG4601.that is earthquake resistant design code for nuclear plants in Japan).

This was done by establishing an analytical method which premises elasto-plastic deformation of the support legs that do not associated with device’s function maintenance.

At first, the support leg’s configuration of the devices supported by four legs in the existing plants was organized, and for the typical legs, the elasto-plastic behavior of support leg itself was verified by element test. Then the authors have established an analytical method that would simulate with result in element test.

Secondly, main configuration (including support leg configuration) of the practical device was organized, and for the typical devices the elasto-plastic behavior of the practical test object was verified by seismic excitation test. Then, the authors have established an analytical method that would simulate with result in seismic excitation test.

By implementing the established analytical method to a few practical devices supported by four legs in the existing domestic PWR and BWR plants, this analytical method was a reasonable method compared to the original standard.
Evaluation of Stuffing Box Forces Associated With the Thermal Expansion of e-PTFE and Graphite Packing Sets
Authors: Girão Carlos D. , Guenther Keith
Published: August 2013

This paper evaluates the stuffing box forces associated with mechanical packing sets comprised of a combination of e-PTFE and Graphite materials. Utilizing a simulated stuffing box test device and protocol, radial and axial forces associated with thermal stresses are measured for different packing configurations. The testing varies the quantity and location of both e-PTFE and Graphite packing material within a five ring packing set. Test results are reported with comparative data and correlations among the configurations.
Justification for a New Industry Standard for Torque Wrench Calibration
Authors: Hamilton Scott R. , Smith Thomas J.
Published: August 2013

In most cases, it is assumed that a manual or hydraulic torque wrench will deliver the requested torque value if set correctly. However, torque wrenches have moving parts that will be subject to wear. They are also subject to harsh operating conditions in the field, which elevates the risk of damage. Calibration is the measurement of a device’s output to a known standard and adjustment to within specific tolerances if necessary.

There are several different codes and standards that are followed in the industry, but these practices are normally left up to interpretation. Common sense tells us calibration of torque wrenches on a periodic basis would be advisable. Many in the industry have different policies that are inconsistent when considering several factors of a calibration program. This may be because there is not data available to justify the cost of such a calibration program or misconceptions on what calibration is and when it should be completed. An analysis of the data reveals exactly why regular, periodic calibration of torque wrenches should be an important part of any maintenance program. By using certain methods of calibration, one can mitigate the risk of an un-calibrated torque wrench affecting one’s facility. This paper includes general trends for a sample of torque wrenches that received calibration in order to compare the overall accuracy of the wrenches prior to calibration versus post-calibration. The study was conducted on data obtained from the calibration of hundreds of wrenches over a five year period. This may be considered a reasonable snap-shot of the inaccuracy of torque wrenches that may be expected in the field if recent calibration has not been performed.

Due to the highly prevalent misconceptions regarding calibration found in the petrochemical and oil industry, there needs to be an industry standard for torque wrench calibration. Our hypothesis for this paper states that each torque wrench that is used in the field, whether it is new, used, or repaired, shall have an individual calibration performed at no less than a 12 month interval. This standard will prevent material damage to the installation and operation of equipment by correcting both slight deviations from accuracy tolerances and, especially, extreme outliers. The material presented in this paper will show justifcation of an industry standard that should be adopted.
Constitutive Model Development for Thermo-Mechanical Fatigue Response Simulation of Haynes 230
Authors: Ahmed Raasheduddin , Menon Mamballykalathil , Hassan Tasnim
Published: August 2013

Turbine engine combustor components are subject to thermo-mechanical fatigue (TMF) during service. The combustor liner temperatures can sometimes reach as high as 1800°F. An accurate estimate of the strains at critical locations in the combustor liner is required for reliable lifing predictions. This demands the need for a detailed analysis of the TMF responses and a robust constitutive model capable of predicting the same. A large set of experiments have been carried out on the liner material, a nickel based alloy, HA 230, in an effort to understand its thermo-mechanical fatigue constitutive response. The out-of-phase strain-controlled TMF experiments with a negative mean strain show a positive mean stress response, while the in-phase TMF experiments with a positive mean strain show a negative mean stress response. A Chaboche based viscoplastic constitutive model is under development. It will have several essential features such as nonlinear kinematic hardening, isotropic hardening, strain range dependence, rate dependence, temperature dependence and static recovery. The constitutive model being developed for accurately calculating the stress-strain response is being carried out with the final objective of predicting the strains in an actual combustor liner in service through finite element simulation for fatigue lifing.
EPRI Guidelines for Fabrication of Components Manufactured From Grade 91 Steel
Authors: Parker Jonathan , Coleman Kent
Published: August 2013

Over the last 10 years EPRI has been researching critical information on the factors affecting the performance of creep strength enhanced ferritic steels in general and Grade 91 steel in particular. This work has resulted in a major new report which provides recommended guidelines for fabrication and the associated quality assurance to ensure that component properties meet or exceed the minimum expectations of ASME design approaches. The present paper outlines the recommendations in the report and provides technical background for specific aspects of the guide.
Design and Baseline Testing of Motor Operated Valves (MOVs) for Generation 3+ Nuclear Power Generating Plants
Authors: Hobbs Matthew E. , Gradle Richard J. , Bensinger Floyd A.
Published: August 2013

Flowserve is supplying motor operated valves (MOVs) to Generation 3+ nuclear power plants. These valves have been custom designed to meet the design and qualification criteria for ASME Section III, Class 1 nuclear service. To support plant operations, the valve designs benefit from the lessons learned from US NRC Generic Letter 89-10, “Safety-Related Motor-Operated Valve Testing and Surveillance”, the subsequent MOV testing programs, the Joint Owners Group (JOG) MOV Periodic Verification Program and ASME QME-1 functional qualifications.

As a result, some new MOV designs are larger and heavier than typical valves of corresponding size and pressure class supplied to existing nuclear power plants.

During the valve functional testing portion of valve manufacturer’s production testing, each MOV assembly is instrumented to record stem thrust and torque, position, motor operator voltage and current draw, and limit switch and torque switch function. The data are digitally recorded for further review and acceptance. The baseline data will allow the end user to confirm proper MOV installation and setup. The baseline data can also be compared to future in-situ test data to evaluate potential performance degradation during the nuclear power plant operation.

This paper discusses:

• MOV design parameters and design features

• The production testing to establish and record MOV baseline functional data and

• ASME QME-1-2007 qualification of these MOVs
Dynamic Stability of an Elastic Beam Subjected to Follower Forces
Authors: Fujita Katsuhisa , Gotou Akihide
Published: August 2013

The stability of nonconservative system of a beam is investigated when an elastic beam is subjected to follower forces. The mathematical formulations for a conservative system and a nonconservative system are established regarding to a uniform cantilever subjected to a concentrated force and a uniform distributed force axially. The displacement of a uniform cantilever is assumed to be obtained by superposing the modal functions which are normal modes in a vacuum, and is estimated by applying the Galerkin’s method. Changing the forces, the eigenvalue analysis is performed, and the root locus is calculated for the stability analysis. And, the relationship between forces and frequencies for the undamped system and the damped system of the uniform cantilever subjected to a concentrated force and a uniform distributed force is investigated. When the system is considered to be conservative, the divergence phenomenon is confirmed to appear first. On the other hand, when the system is considered to be nonconservative, the flutter phenomenon is confirmed to appear first although the critical force becomes high. And, by changing the structural damping, the destabilized effect due to the damping is confirmed when an elastic beam is subjected to follower forces.
Material Characterization and Modeling Within Safety Analysis of Packages for Transport of Radioactive Material
Authors: Neumann Martin , Ballheimer Viktor , Sterthaus Jens , Schubert Sven , Eisenacher Germar , Wille Frank
Published: August 2013

In mechanical design safety assessment of packages for the transport of radioactive material the International Atomic Energy Agency (IAEA) regulations [1, 2] require the use of one of four methods of demonstration of compliance with regulations: tests with prototypes, reference to previous satisfactory demonstrations, tests with scaled models as well as calculation or reasoned argument. In all cases characterization of material behavior is necessary. The need for material characterization can be split into three groups: characterization for material modeling in the design and verification process, determination of assessment criteria and inspections during manufacturing.

The paper deals primarily with material characterization for the material modeling in the design phase and authorities approval process. Main package components are discussed: cask body and lids, screws, trunnions, impact limiter and basket (structure holding the content in specified position). Depending on the material used for these components this paper shows exemplary a possible set of material investigations in order to allow modeling in design and assessment during the approval process.
Development of Material Model Parameters Suitable for the Finite Element Simulation of Ferritic Welds
Authors: Bate Steve , Shallcross Neil , Stone Karen , Francis John , Mark Alison , Gill Chris
Published: August 2013

The prediction of residual stresses in ferritic welds using finite element techniques requires materials properties to describe the thermal, tensile, cyclic and phase transformation behaviour that the material undergoes during welding and also during creep as the effect of post weld heat treatment is also of interest. Ferritic steels will transform at a temperature above about 850°C to austenite. As the steel is cooled, a further phase transformation in the structure occurs. The precise structure formed depends on the detailed chemical make-up of the steel and on the rate at which it is cooled. On slow cooling from above 850°C a pearlite-ferrite microstructure is formed. On more rapid cooling, other microstructures, particularly bainite at intermediate cooling rates and martensite at the highest cooling rates are formed. Predicting the phase on cooling requires a Continuous Cooling Transformation diagram that is suitable for welding thermal cycles and reflects the time spent above the austenitisation threshold which influences the austenitic grain size formed and subsequently the phase of material on cooling. Material properties for a SA508 Grade 3 steel and a low carbon SD3 filler metal have been generated and fitted to constitutive models that are available in the finite element codes ABAQUS and SYSWELD. The choice of hardening model and its associated parameters have been evaluated on the basis of the observed cyclic behaviour in materials testing. Validation of these models has then been carried out by finite element simulations of welded mock-ups which have been measured using neutron diffraction. These include an autogenous weld beam and groove weld specimens containing up to eight weld passes. The rationale for using these simple specimens has been to:

• Validate the capability of the model to predict the correct phase transformation behaviour and resulting stresses.

• Account for the different behaviour of the parent and filler material.

• To develop the capability for representing the material cyclic behaviour.

On the basis of these simulations recommendations have been made on the material models (and their parameters) that may be used for the finite element simulation of the welding process.
Mechanical Behaviour of High Burn-Up SNF Under Normal and Accident Transport Conditions: Present Approaches and Perspectives
Authors: Ballheimer Viktor , Wille Frank , Rolle Annette , Droste Bernhard
Published: August 2013

Transport packages for spent fuel have to meet the International Atomic Energy Agency requirements for different transport conditions. Physical state of spent fuel and fuel rod cladding as well as geometric configuration of fuel assemblies are important inputs for the evaluation of package capabilities under these conditions. In this paper, the mechanical behaviour of high burn-up spent fuel assemblies under transport conditions is analysed with regard to assumptions to be used in the activity release and criticality safety analysis. In particular the different failure modes of the fuel rods (fine cracks or complete breakage), which can cause release of gas, volatiles, fuel particles or fragments have to be properly considered in these assumptions. In view of the complexity of interactions between the fuel rods as well as between fuel assemblies, basket, and cask containment, the exact mechanical analysis of such phenomena is nearly impossible. The gaps in information concerning the material properties of cladding and pellets, especially for the high burn-up fuel, make the analysis more complicated additionally. In this context some practical approaches based on experiences of BAM Federal Institute for Material Research and Testing within safety assessment of packages for transport of spent fuel are discussed.
Creep and Fracture Behavior of Centrifugal Cast HP40Nb Alloy Containing Lead
Authors: Chen Tao , Chen Xuedong , Lu Yunrong , Ye Juan , Lian Xiaoming
Published: August 2013

Centrifugal cast HP40Nb alloys are commonly used as ethylene pyrolysis and reformer furnace tube materials. The actual wall temperature can usually reach 1423 K. The technical specifications require that the rupture life shall be at least 120 h under test condition of 1373 K at 17 MPa. The effects of amounts of Lead on the creep and stress rupture performance of the centrifugal cast HP40Nb alloy have been investigated at the temperature of 1373 K and the constant stress of 17 MPa. In this paper, HP40Nb alloy tubes with different contents of Lead element by centrifugal casting were selected, by high temperature stress rupture test and microscopic observation of creep damage, relationship between the content of Lead and high temperature stress rupture lives was given, as well as the threshold value of Lead element. It could provide the basis for ethylene pyrolysis furnace tubes manufacturers and design specifications.
A Fully Implicit, Lower Bound, Multi-Axial Solution Strategy for Direct Ratchet Boundary Evaluation: Theoretical Development
Authors: Jappy Alan , Mackenzie Donald , Chen Haofeng
Published: August 2013

Ensuring sufficient safety against ratchet is a fundamental requirement of pressure vessel design. Determining the ratchet boundary can however prove difficult when using a full elastic plastic finite element analysis and a number of direct methods have been proposed that overcome the difficulties associated with ratchet boundary evaluation. Here, a new approach based on fully implicit methods, similar to conventional elastic-plastic methods, is presented. The method utilizes a two-stage procedure. The first stage determines the cyclic stress state, which can include a varying residual stress component, by repeatedly converging on the solution for the different loads by superposition of elastic stress solutions using a modified elastic-plastic solution. The second stage calculates the constant loads which can be added to the steady cycle whilst ensuring the equivalent stresses remain below a modified yield strength. During stage 2 the modified yield strength used is updated throughout the analysis thus satisfying Melans Lower bound ratchet theorem. This is achieved through the same elastic plastic model as the first stage, using a modified radial return method. The methods that have been proposed here are shown to provide better agreement with upper bound ratchet method than the Hybrid method, however some limitations in this type of method have been identified and are discussed.
A Fully Implicit, Lower Bound, Multi-Axial Solution Strategy for Direct Ratchet Boundary Evaluation: Implementation and Comparison
Authors: Jappy Alan , Mackenzie Donald , Chen Haofeng
Published: August 2013

Ensuring sufficient safety against ratcheting is a fundamental requirement of pressure vessel design. However, determining the ratchet boundary using a full elastic plastic finite element analysis can be problematic and a number of direct methods have been proposed to overcome difficulties associated with ratchet boundary evaluation. This paper proposes a new approach, similar to the previously proposed Hybrid method but based on fully implicit elastic-plastic solution strategies. This method utilizes superimposed elastic stresses and modified radial return integration to converge on the residual state throughout, resulting in one Finite Element model suitable for solving the cyclic stresses (stage 1) and performing the augmented limit analysis to determine the ratchet boundary (stage 2). The modified radial return methods for both stages of the analysis are presented, with the corresponding stress update algorithm and resulting consistent tangent moduli. Comparisons with other direct methods for selected benchmark problems are presented. It is shown that the proposed method consistently evaluates a lower bound estimate of the ratchet boundary, which has not been demonstrated for the Hybrid method and is yet to be clearly shown for the UMY and LDYM methods. Limitations in the description of plastic strains and compatibility during the ratchet analysis are identified as being a cause for the differences between the proposed methods and other current upper bound methods.
Assessment of Slot Influence in the Fatigue Thermal Life of Coke Drums
Authors: Vivas Gabriel A. , Araque Egler D. , Pertuz Alberto D. , Oka Masaaki
Published: August 2013

Delayed coke drums are vertical thin-walled pressure vessels that operate under severe conditions by cyclic heating and quenching operations. The high stresses can lead to premature drum failure in the form of through wall cracking resulted from low cycle fatigue. One of the ways that has been used to reduce the growth of cracks localized near the shell to skirt weld is by the addition of different slots configurations in the skirt. In order to estimate fatigue life, a finite element analysis (FEA) was carried out using a decoupled thermo-mechanical assessment. In the first step, a thermal analysis was done to estimate the variation of temperature throughout the coking cycle. In the second step, this thermal response was combined with the mechanical loads to estimate the total stress and strain. The validity of the models has been demonstrated by several FEA results and by some field measured data. It is proposed a set of mathematical relations that allows predicting the behavior of fatigue lifetime as a function of slot size and hole radius.
On Pipe Elements Currently Available for Nuclear Power Piping Analysis and Their Benchmark Tests
Authors: Zeng Lingfu , Jansson Lennart G.
Published: August 2013

In this paper, an overview is given for various pipe elements currently available in commercial general-purpose finite element software, such as ADINA, ANSYS and ABAQUS and several others, with respect to their formulations, applications and limitations. Throughout the overview, a comparison to piping analysis based on a usual 3-diemnsional beam theory, which appears in many software particularly developed in early years for piping analysis is made. Benchmark tests ranging from simple to relative complex nuclear piping systems, given by US Nuclear Regulatory Commission (NRC), are taken for addressing three key concerns in nuclear piping analysis: reliability, accuracy and effectivity. It is demonstrated that: (1) piping analysis using software developed purely based on traditional curved beam theory can go wrong; and (2) a reliable piping analysis, in particular, for complex loading conditions and non-linear applications, can only be achieved by using so-called pipe-shell elements.
Evaluation of Long-Term Creep Strength of ASME Grades 91, 92, and 122 Type Steels
Authors: Kimura Kazuhiro , Takahashi Yukio
Published: August 2013

Creep rupture data of ASME Grades 91, 92 and 122 type steels have been collected and long-term creep rupture strength of the steels has been evaluated. Similar study was conducted by the SHC committee in 2004 and 2005, therefore, the evaluation of long-term creep rupture strength was conducted with emphasis on the long-term creep rupture data obtained after the previous study. Creep rupture strength was analyzed by means of region splitting analysis method in consideration of 50% of 0.2% offset yield strength, in the same way as the previous study. Almost the same results were obtained on base metal of Grade 92 as the previous study, however, evaluated 100,000 hours creep rupture strength of base metal of Grades 91 and 122 were lower than the previous results. For Grades 91 and 122 type steels, moreover, creep rupture strength of the plate steel were lower than those of pipe and forging steels. Tendency to decrease with increase in nickel content was observed on long-term creep rupture strength of tube steel of Grade 91 at 600°C. According to the evaluation of long-term creep strength of the steels, allowable tensile stress was reviewed and proposed revision was concluded.
Experimental Research on High-Temperature Pipe Corrosion On-Line Monitoring
Authors: Ye Yufeng , Xia Li
Published: August 2013

Nowadays, Ultrasound guided wave has adapted to the monitoring corrosion of pipeline at room temperature, but not worked well at high temperature. This paper introduced the basic theory of guided wave on high temperature on-line monitoring; based on some research on the test pipeline, we researched the technology of high temperature on-line monitoring, and made use of the technology on 7 high temperature pipes in Catalytic Cracking Unit to obtain the monitoring the corrosion of high temperature pipeline based on the magnetostrictive effect of guided wave technology by taking one of them as an example to monitor its corrosion and analysis the data.
Reliability Analysis for the Feeder Subject to Wall Loss
Authors: Wang Min , Yuan Xianxun , Duan Xinjian , Kozluk Michael J.
Published: August 2013

Wall thinning is one of the most common degradation mechanisms experienced in piping system. Gradual wall thinning can cause the pipe to leak or in the worst scenario, to rupture. Wall thinning due to FAC of feeder pipe in CANDU® reactors has been identified as an active degradation mechanism, and local thinning has been observed in various locations such as elbows/bends and Grayloc. The assessment of structural integrity is important for the fitness-for-service of those feeders whose wall thickness is predicted to be lower than the required minimum wall thickness before their design life and therefore subject to costly repair or replacement. Among various probabilistic methods, the first-order reliability method (FORM) is adopted in this paper to evaluate the structural reliability of feeders subject to wall thinning, while the wall thickness, one of the key parameters in the reliability analysis, is modeled by three methods based on the wall thickness measurements. They are linear regression analysis, random thinning rate analysis and gamma process modeling. The difference and limitation of the methods for reliability analysis are addressed.
Pipe Elbows Under Strong Cyclic Loading
Authors: Varelis George E. , Karamanos Spyros A. , Gresnigt Arnold M.
Published: August 2013

Motivated by the response of industrial piping under seismic loading conditions, the present study examines the behavior of steel process piping elbows, subjected to strong cyclic loading conditions. A set of experiments is conducted on elbow specimens subjected to constant-amplitude in-plane cyclic bending, resulting into failure in the low-cycle-fatigue range. The experimental results are used to develop a low-cycle-fatigue curve within the strain-based fatigue design framework. The experimental work is supported by finite element analyses, which account for geometrical and material nonlinearities. Using advanced plasticity models to describe the behavior of elbow material, the analysis focuses on localized deformations at the critical positions where cracking occurs. Finally, the relevant provisions of design codes (ASME B31.3 and EN 13480) for elbow design are discussed and assessed, with respect to the experimental and numerical findings.
Thermal Fatigue Evaluation Method of Pipes by Equivalent Stress Amplitude
Authors: Suzuki Takafumi , Kasahara Naoto
Published: August 2013

In recent years, reports have increased which are about failure cases caused by high cycle thermal fatigue both at light water reactors and fast breeder reactors. One of the biggest reasons of the cases is a turbulent mixing at a Tee-junction, where hot and cold temperature fluids are mixed, in a coolant system. In order to prevent thermal fatigue failures at Tee-junctions, The Japan Society of Mechanical Engineers (JSME) published the guideline S017-2003 (or JSME guideline) which is an evaluation method of high cycle thermal fatigue damage at a nuclear piping. It has some limitations in terms of its inconstant safety margin and its complexity in evaluation procedure, however. In order to solve these limitations, this paper proposes a new evaluation method of thermal fatigue damage with use of the “equivalent stress amplitude” which represents random temperature fluctuation effects on thermal fatigue damage. Because this new method makes methodology of evaluation clear and concise, it will contribute to improving the guideline for thermal fatigue evaluation.
Serrated Metal Graphite Faced Gaskets for Ring Joint Flanges
Authors: Veiga José C. , Cipolatti Carlos F. , Kavanagh Nelson , Castro Fabio , Zandoná Valtemir
Published: August 2013

Metal Ring Joint gaskets are used in piping and equipment that operate at high pressure and/or temperature. Flange faces for these gaskets are precisely machined and small imperfections on the sealing surface make them unusable, requiring replacement or expensive field machining. During plant shut-downs time constraints may not allow for flange replacement or surface repairs. As a temporary fix gasket manufacturers offer other gasket styles like graphite faced serrated metal or spiral wound. This paper studies the use of graphite faced serrated metal gaskets in ring joint flanges. In addition to laboratory tests, also the results of a successful application of a Double-Rail gasket in a shut-down of a Petrochemical plant are shown.