bluuebunny/crossref_metadata_2025 huggingface dataset:
Global-Local Analysis of a Composite Riser
Authors: Akula Venkata M. K.
Published: November 2014

Composite materials are often utilized in weight-critical applications, owing to their higher specific strength\stiffness characteristics. In addition, composite materials also possess qualities such as better corrosion resistance, lower coefficient of thermal expansion, etc., which makes them a potential material choice for riser systems in high pressure and high temperature environments. However, design certification of risers using the finite element method requires modeling and analysis techniques, centric to the multi-layered nature of composite structures.

Riser systems, owing to their high aspect ratios, have traditionally been modeled with beam elements. The methodology for extracting the stress results and certifying a metallic riser is well established in the Oil and Gas industry. However, for analyzing a composite riser, three-dimensional shell or hexahedral elements are generally required to capture the through-the-thickness (or pipe cross-sectional) variation of structural response, especially in critical regions such as touchdown point, pipe-intersection zones, etc.

In this paper, a method for analyzing a detailed local model (discretized with shell\hexahedral elements) driven by results from a global model (meshed with beam elements) is presented. The global model captures the structural response whereas the local model provides cross-sectional stress\strain information for individual layers. Although the method is illustrated for a composite riser, it is also applicable to metallic structures.
Effect of Cutting Method on Fatigue Crack Initiation and Fatigue Life of Structural Steel S355M
Authors: Garcia Tiberio , Cicero Sergio , Carrascal Isidro , Madrazo Virginia , Álvarez José Alberto
Published: November 2014

This paper analyses the effect of the cutting method on both the fatigue crack initiation and the fatigue life of steel S355M. The research covers three cutting methods (plasma, laser and oxy-fuel) and two specimen geometries: plain specimens with rectangular section and cut edges, and specimens with machined edges and a cut hole in the middle section. All the specimens were conducted to failure in a resonance machine 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. The crack initiation time was estimated by analyzing the evolution of the resonance frequency on each specimen. The results show a significant influence of the cutting method on both the crack initiation and the fatigue life of this particular steel.
Evaluation of ASME Pressure Vessel Code Prohibitions on Rod and Bar Stock and Potential Remedies
Authors: Aumuller John J. , Carucci Vincent A.
Published: November 2014

The ASME Codes and referenced standards provide industry and the public the necessary rules and guidance for the design, fabrication, inspection and pressure testing of pressure equipment. Codes and standards evolve as the underlying technologies, analytical capabilities, materials and joining methods or experiences of designers improve; sometimes competitive pressures may be a consideration. As an illustration, the design margin for unfired pressure vessels has decreased from 5:1 in the earliest ASME Code edition of the early 20th century to the present day margin of 3.5:1 in Section VIII Division 1. Design by analysis methods allow designers to use a 2.4:1 margin for Section VIII Division 2 pressure vessels.

Code prohibitions are meant to prevent unsafe use of materials, design methods or fabrication details. Codes also allow the use of designs that have proven themselves in service in so much as they are consistent with mandatory requirements and prohibitions of the Codes. The Codes advise users that not all aspects of construction activities are addressed and these should not be considered prohibited. Where prohibitions are specified, it may not be readily apparent why these prohibitions are specified. The use of “forged bar stock” is an example where use in pressure vessels and for certain components is prohibited by Codes and standards.

This paper examines the possible motive for applying this prohibition and whether there is continued technical merit in this prohibition, as presently defined. A potential reason for relaxing this prohibition is that current manufacturing quality and inspection methods may render a general prohibition overly conservative. A recommendation is made to better define the prohibition using a more measurable approach so that higher quality forged billets may be used for a wider range and size of pressure components.

Jurisdictions with a regulatory authority may find that the authority is rigorous and literal in applying Code provisions and prohibitions can be particularly difficult to accept when the underlying engineering principles are opaque. This puts designers and users in these jurisdictions at a technical and economic disadvantage.

This paper reviews the possible engineering considerations motivating these Code and standard prohibitions and proposes modifications to allow wider Code use of “high quality” forged billet material to reflect some user experiences.
Development of Enertech’s Advanced Normally Open NozzleCheck Valves for Generation III+ Nuclear Power Plants
Authors: Mkrtchyan Haykaz
Published: November 2014

Enertech introduced the first Normally Open NozzleCheck valves to the nuclear power industry nearly 20 years ago. This passive valve design was developed to address reoccurring maintenance and reliability issues often experienced by various check valve types due to low or turbulent flow conditions. Specifically, premature wear on the hinge pins, bushings and severe seat impact damage had been discovered in several applications while the systems were in steady state operating conditions.

Over the last two decades, Enertech has continued to improve upon the design of the valve, with the culmination coming most recently in support of Generation III+ passive reactor requirements. This entirely new valve is designed with minimal stroke, ensuring quick closure under low reverse flow conditions which no other check valve design could support. Additionally, features such as first in kind test ports, visual inspection points, and the ability to manually stroke the valve in line have resolved many of the short comings of previous inline welded flow check valves.

Most importantly, advanced test based methodologies and models developed by Enertech, allow for accurate prediction of NozzleCheck valve performance. This paper presents the development of Enertech’s advanced Normally Open NozzleCheck Valve for Generation III and III+ nuclear reactor designs. The Valve performance was initially determined by using verified and validated computational fluid dynamic (CFD) methods. The results obtained from the CFD model were then compared to the data gathered from a prototype valve that was built and tested to confirm the performance predictions. Enertech has fully tested and qualified the Normally Open NozzleCheck valve which is specifically designed for applications that require a high capacity in the forward flow direction and a quick closure during low reverse flow condition with short stroke to minimize the hydraulic impact on the system.
Flow-Induced Vibration of a Cylinder in the Wake of Another of Smaller Diameter
Authors: Alam Md. Mahbub , Ran An , Zhou Yu
Published: November 2014

This paper presents cross-flow induced response of a both-end-spring-mounted circular cylinder (diameter D) placed in the wake of a rigid circular cylinder of smaller diameter d. The cylinder vibration is constrained to the transverse direction. The cylinder diameter ratio d/D and spacing ratio L/d are varied from 0.2 to 1.0 and 1.0 to 5.5, respectively, where L is the distance between the center of the upstream cylinder to the forward stagnation point of the downstream cylinder. A violent vibration of the cylinder is observed for d/D = 0.2 ∼ 0.8 at L/d = 1.0, for d/D = 0.24 ∼ 0.6 at 1.0 < L/d ≤ 2.5, for d/D = 0.2 ∼ 0.4 at 2.5 < L/d ≤ 3.5, and for d/D = 0.2 at 3.5 < L/d ≤ 5.5, but not for d/D = 1.0. A smaller d/D generates vibration for a longer range of L/d. The violent vibration occurs at a reduced velocity Ur (=U∞/fnD, where U∞ is the free-stream velocity and fn the natural frequency of the cylinder system) beyond the vortex excitation regime (Ur ≥ 8) depending on d/D and L/d. Once the vibration starts to occur, the vibration amplitude increases rapidly with increasing Ur. It is further noted that the flow behind the downstream cylinder is characterized by two predominant frequencies, corresponding to the cylinder vibration frequency and the natural vortex shedding frequency of the cylinder, respectively. While the former persists downstream, the latter vanishes rapidly.
Effects of Mechanical Loading on Residual Stress and Fracture: Part II — Validation of the BS 7910:2013 Rules
Authors: Hadley Isabel , Smith Simon
Published: November 2014

Failure of welded structures due to the presence of flaws is typically driven by a mixture of applied and residual stresses, yet in most cases only the former are known accurately. In as-welded structures, a typical assumption is that the magnitude of welding residual stress is bounded by the room temperature yield strength of the parent material. The UK flaw assessment procedure BS 7910:2013 also assumes that mechanical loading (either as a result of proof testing or during the initial loading of an as-welded structure) will bring about a relaxation in residual stress. Conversely, the UK structural assessment code for nuclear structures, R6, contains a warning on the ‘limited validation’ of the BS 7910 approaches for stress relaxation and suggests that they should be used ‘with caution’. The aim of this study was therefore to review the basis of the BS 7910 clauses on stress relaxation with a view to harmonising the BS 7910 and R6 rules for cases in which the original welding residual stress distribution is not known.

A companion paper describes the history of the residual stress relaxation clauses of BS 7910. A considerable programme of work was carried out in the late 1980s to justify and validate the clauses, using a range of experimental and numerical work. This included analysis of work carried out by the UK power industry and used in the validation of the R6 procedure. The full underlying details of the work have not hitherto been available in the public domain, although the principles were published in 1988. The approach proposed in BS 7910 combines ‘global’ relaxation of residual stress (Qm) under high mechanical load with ‘local’ enhancement of crack tip driving force through the adoption of a simplified primary/secondary stress interaction factor, ρ. This is different from the method adopted by R6, but appears to be equivalent to allowing negative values of ρ under conditions of high primary stress.

A re-analysis of the original TWI work, using the current version of BS 7910, has shown nothing to contradict the approach, which represents a workable engineering solution to the problem of how to analyse residual stress effects in as-welded structures rapidly and reasonably realistically when the as-welded stress distribution is unknown.
Fracture Toughness Behavior of Complex Cracks in Dissimilar Metal Welds
Authors: Rudland D. , Benson M. , Shim D.-J.
Published: November 2014

Currently, J-estimation scheme procedures to predict the load-carrying capacity of idealized circumferential through-wall cracks in nuclear grade piping materials employ analytical or numerical procedures coupled with the fracture toughness of the material to predict the pipe response. However, with the advent of primary water stress corrosion cracking (PWSCC), complex-shaped cracks occur in dissimilar metal (DM) welds. These welds consist of a nickel-based weld joining stainless steel and carbon steel base metals.

The NRC Office of Nuclear Regulatory Research (RES) is conducting a program to investigate the behavior of circumferential through-wall and complex cracks in DM welds. In a prior paper, a series of full-scale pipe bend and laboratory-sized fracture experiments were documented. Initial analyses of those test results suggest that reasonable prediction of through-wall crack response is obtained from typical J-estimation scheme procedures using the weld toughness from a compact tension (CT) specimen and the appropriate material strength. In addition, the J-R curves from the through-wall cracked pipe tests, calculated using published η-factor solutions and numerical techniques, were very similar to the CT J-R curves. In this paper, the fracture toughness for the circumferential complex cracked experiments, which was developed from a modified η-factor solution, is presented. These results are compared to the CT and through-wall crack pipe J-R curve results. In addition, predictions of load carrying capacity using the complex crack J-R curve and through-wall crack J-estimation schemes are presented and illustrate the need for the development of a complex crack J-estimation scheme. To support this development, a net-section collapse solution and a modified K-solution is presented. Finally, the need for additional work to generalize the elastic solution and its incorporation into a closed-form J-estimation scheme is discussed.
Finite Element Analysis of a Pipe Junction With a Thermal Sleeve Subject to Thermal and Pressure Transient Events
Authors: Pattinson Alec , Dodds James , Hugill Peter , Reed Gary
Published: November 2014

This paper describes the results of a Finite Element Analysis (FEA) of a pipe junction consisting of a thermal sleeve subject to rapid temperature changes. The purpose of the analysis was to utilise derived Computational Fluid Dynamic (CFD) temperatures to calculate stresses on the pressure boundary and thermal sleeve of a pipe junction.

Several transient events were modelled and analysed. Work was then carried out in accordance with the relevant articles of the ASME Boiler and Pressure Vessel Code, Section III, sub-section NB. Work included, design, hydrotest, Level A (including fatigue) and simplified elastic plastic assessments, however not presented within this paper.

The likely fracture performance of the pressure boundary was also investigated, however are also not presented within this paper.
Acoustic Fatigue Evaluation of Branch Connections
Authors: Lin Dan , Prakash Ajay , Diwakar Philip , David Bertito
Published: November 2014

High acoustic energy is known to cause vibrations in pipes, and in some severe cases acoustic induced vibration can lead to fatigue failure at branch connections with high stress concentration. Industry guidelines suggest using mitigation measures such as fabricated full wrap-around reinforcement pad (re-pad) or Sweepolet fittings at branch connections. Effectiveness of these mitigation measures is evaluated via a finite element analysis of four types of branch connections; (i) Sockolet, (ii) Sockolet with 2″ wide partial re-pad, (iii) Sockolet with full wrap-around re-pad, and (iv) Sweepolet. Four distinct acoustic frequency ranges (1/3 octave bands) with associated sound pressure levels are used as the excitation source. Maximum stress levels in the main header pipe at the branch tie-in are monitored to assess the potential for vibration damage. Of the four branch connections, Sockolet with full wrap-around re-pad is found to be least susceptible to damage, followed by the Sweepolet. Unreinforced Sockolet is most susceptible to damage, and the Sockolet with partial re-pad is only marginally better.
Whirl Stability of Herringbone-Grooved Gas-Lubricated Journal Bearing
Authors: Fujita Katsuhisa
Published: November 2014

A herringbone-grooved gas-lubricated journal bearing can rotate silently at high speed with low friction, and moreover it can be small-sized. In this paper, the equation of motion of a herringbone-grooved gas-lubricated journal bearing is derived using the gas force which can be obtained by applying the Navier-Stokes equation to the grooved and the ridged parts of a journal. The stability analysis is performed by using the analysis method by Routh-Hurwitz, the root locus of complex eigenvalue analysis, and the transient time history response analysis. The physical meanings of the stability charts which have not been explained sufficiently in the conventional studies are clarified by considering the forward whirling motion and the backward whirling motion, and the more reasonable stability charts are proposed. In addition, it is reported that the present analysis results show a good agreement with the already reported experimental results. Furthermore, the parametric studies as for the specification of gas-lubricated bearing are performed, and it is shown that the stability charts are affected by the change of specifications intricately.
Account for Metal to Metal Contact Between Gasket Centering Ring and Flange Facing in Calculation Using the XP CEN\TS 1591-3 Method: Comparison With Other Analytical Method and Finite Element Analysis
Authors: Lejeune Hubert , Ton That Yann
Published: November 2014

The european standard EN1591-1 [1], initially published in 2001, defines a calculation method for bolted gasketed circular flanges, alternative to the TAYLOR-FORGE method, used as the basic method in most codes. In 2007, a new part, XP CEN/TS 1591-3 [2], has been added to the EN1591 series. This technical specification enables to take into account the Metal to Metal Contact (MMC), appearing inside the bolt circle on some assemblies. Due to a lack of industrial feedback and detailed validation, this document has not been raised to the standard status.

In that context, under the request of its Pressure Vessel and Piping commission, CETIM has performed a study comparing this calculation method to Finite Element Analysis (FEA) on several industrial configurations. After a description of the XP CEN/TS 1591-3 calculation method, the major results obtained for spiral wound gasketed joints where MMC appears between centering ring and flange facing are presented and compared with FEA results. Moreover, results obtained with other classical analytical calculation methods as TAYLOR FORGE and EN1591-1 on the same Bolted Flange Connections (BFC) configuration are also analysed and compared to XP CEN/TS 1591-3 results.
Automated Fracture Mechanics and Fatigue Analyses Based on Three-Dimensional Finite Element for Welding Components
Authors: Nakamura Hitoshi , Tajima Seiichi , Hazama Osamu , Gu Wenwei
Published: November 2014

This paper describes the structure and application of a software system that automates the fatigue initiation and crack propagation analysis based on FEM. The system automatically performs necessary procedures to track propagation history of cracks: insertion of a crack and updating of three-dimensional finite element mesh in accordance with the crack propagation. Most of the meshing is carried out by a Delaunay tessellation method. A tubular hexahedral mesh is generated at the crack front and the fracture mechanics parameters are computed using commercial codes to ensure accuracy. The generation of this tubular hexahedral mesh is fully automatic as well.

The system is equipped with a function to automatically perform fatigue analyses using the stress-strain histories at nodes of a three-dimensional FEM model. The standard low cycle fatigue analysis approach is adopted. Using the function, cumulative fatigue for a given FEM model is provided. Some analyses for several examples were carried out for validation. The important example is the surface crack propagation in steel pipes with residual stress.
A Coupled Fluid-Solid Model to Investigate Leak Rates for Leak-Before-Break Assessments
Authors: Gill Peter , Davey Keith , Sharples John
Published: November 2014

A multiscale model is discussed here which incorporates fluid mechanics into a structural model. This is so that leak rates can be output from a crack in a finite element model without any complex meshing or post processing. The model can be implemented into any standard finite element solver, meaning leak rates can be investigated for cracks in realistic components. Crack opening area is obtained directly from the special elements that surround the crack, and leak rate is output with the solution. By adopting this holistic approach, it makes the calculation of leak rate more efficient, with the added benefit of higher accuracy. Furthermore, this provides a tool to investigate thermal interactions between the fluid and solid. Presented in this paper is a description of the physical model, and an outline of the numerical solution procedure. Leak rates are also discussed for the case of crack in a plate. The numerical tool provides an effective way of coupling a fluid model with microscale effects, to a macroscale solid model. Investigations using this new method have the potential to reduce uncertainty in leak rate evaluation. Also, by reducing the uncertainty, it is suggested that there would be an increase in the number of situations where Leak-before-Break could be applied in Nuclear Power Plants.
Influence of Residual Tensile Stress on Stress Corrosion Behavior of the Base Metal of X80 Pipe
Authors: Xiong Qingren , Liu Daoxin , Zhang Guanjun , Zhang Jiming , Qin Changyi , Xu Zipeng
Published: November 2014

The influence of residual stress on stress corrosion behavior was studied by way of SSRT test on the base metal of X80 pipe with different residual tensile stress in the simulating soil environment aqueous solution; and the electrochemical test techniques were adopted to test the effect of the residual stress on electrochemical polarization behavior and AC impedance characteristics of the base metal. It is shown that the base metal specimens without introducing the residual stress of X80 UOE pipe and X80 SAWH pipe have different stress corrosion sensitivity in this solution. The base metal specimens with different residual stress of X80 pipe only occurs the anodic metal dissolution reaction on the material surface in this kind of solution without forming the passive film. The residual tensile stress leads to the increase of the electrochemical activity and the reduction of impedance of the base metal surface of X80 pipe, and it accelerates the nucleation and early propagation of the stress corrosion crack, which promotes the SCC sensitivity of the base metal.
Characteristics of Fatigue Crack Growth and Stress Corrosion Cracking in Aggressive Environments of Aluminum Alloys for Hydrogen Gas Containers
Authors: Ogawa Takeshi , Hasunuma Shota , Sogawa Naoki , Yoshida Taiki , Kanezaki Toshihiko , Mano Satomi
Published: November 2014

Hydrogen gas container is one of the critical components for fuel cell electric vehicle (FCEV), which is expected for CO2-free personal transportation. In order to choose an appropriate material for its metal boss and liner, crack growth resistance should be evaluated for various aspects such as fatigue crack growth (FCG) and stress corrosion cracking (SCC) in salt water or humid air environments for the purpose of commercial vehicle use. In the present study, FCG tests were carried out for A6061 and A6066 alloys in laboratory air and in 3.5% NaCl solution for compact (CT) and single edge notched (SEN) specimens. Some SEN specimens were cut from machined hydrogen container made of A6066 at the neck and the shoulder locations. SCC tests were carried out for A6061, A6066 and A6351 (fine and coarse grains) alloys in 3.5% NaCl solution and in humid air for CT specimen.
US Nuclear Regulatory Commission Perspective on Buried and Underground Piping Issues at Nuclear Power Plants in the United States
Authors: Alley David
Published: November 2014

This paper provides a historical perspective on the need for, and development of, buried and underground piping tanks programs at nuclear power plants. Nuclear power plant license renewal activities, Nuclear Regulatory Commission Buried Piping Action Plan, and the rationale for addressing the issue of buried pipe through an industry initiative as opposed to regulation are discussed. The paper also addresses current NRC activities including the results of Nuclear Regulatory Commission inspections of buried piping programs at nuclear power plants as well as Nuclear Regulatory Commission involvement in industry and standards development organizations. Finally, the paper outlines the Nuclear Regulatory Commission’s future plans concerning the issue of buried piping at US nuclear power plants.
The Role of Composite Repair Technology in Rehabilitating Piping and Pipelines
Authors: Alexander Chris
Published: November 2014

Composite materials have been used to repair high pressure pipelines and piping for the better part of 20 years. The initial aim of composite repair technology was focused on reinforcing corrosion. However, composite materials are now used to reinforce a wide array of anomalies and features including dents, mechanical damage, vintage girth and seam welds, wrinkle bends, elbows, tees, branch connections, and even cracks.

In this paper the author provides an industry overview including results and insights from multiple research programs sponsored by composite repair manufacturers, pipeline operators, and the Pipeline Research Council International, Inc. Discussions will also be included regarding the important role that the ASME PCC-2 and ISO 24817 composite repair standards have in ensuring that quality control measures are in place. The ongoing focus of these efforts has been to demonstrate to industry the capabilities that composite repair systems have to provide long-term solutions for reinforcing damaged equipment.
Bolted Flanged Joint Creep/Relaxation Results at High Temperatures
Authors: Mann J. Adin , Hilsabeck Jeremy , Mckoon Cale , Jackson Courtnee
Published: November 2014

An ASME Class 300 NPS12 flange connection between a control valve and a pipe has been evaluated at a temperature of 1100° F with testing and Finite Element Analysis (FEA). The goal of the testing was to validate the FEA simulation. The valve side of the test sample was a cast structure, the pipe side was a forged flange butt welded to a pipe section, and the gasket was a Thermiculite filled spiral wound gasket. The valve, flange, and piping material are SA-217, SA-182, and SA-335 (2 ¼ Cr – 1 Mo) steel respectively. The bolt length and flange geometry was measured before and after loading the bolts, and before and after heating the sample in order to measure changes in the bolt load and flange rotation which would indicate creep/relaxation in the joint. Tests were run with two types of bolts, B16 (SA-193) and 718 (SB-637), and also with two gasket arrangements, no gasket and then a spiral wound gasket. The results of the completed test and the correlation to an FEA analysis will be presented.
Burst Tests of B16.9 Welded Tees
Authors: Stonehouse Mark , Paulin Tony , Becht Charles , Becht Charles
Published: November 2014

This paper presents the results of a small sample of ASME B16.9 welding tee burst tests. The intent of this study was to make a comparison between what is commonly accepted in industry as a B16.9 welding tee to the burst test requirements of B16.9 paragraph 9. The tests conducted show that the current fabrication techniques and some accepted criteria for B16.9 certification can produce thin sections in the tee which do not meet the required burst test pressures.

The test descriptions and results are presented as well as recommendations for future study and potential modifications to the ASME B16.9 standard to address the concerns.
Application of 3D X-Ray Tomography to Enhance the Calibration of Ductile Fracture Models
Authors: Daly Michael , Leonard Fabien , Sherry Andrew H.
Published: November 2014

Reactor Pressure Vessels (RPV) are manufactured from medium strength low allow ferritic steel specifically selected for its high toughness and weldability. The normal operating temperature of RPV steels is sufficiently high to ensure that the material remains ductile throughout its service life with an extremely low probability of cleavage under normal and off-normal loading conditions. Understanding and having the ability to predict ductile fracture behaviour is consequently important.

The ductile fracture mechanism is characterised by the nucleation, growth and coalescence of voids at initiating particles within the volume of high triaxial stress and plastic strain ahead of a crack-tip or stress concentrator. The fracture properties of the steels are conventionally determined using standard pre-cracked compact test specimens. Mechanistically based models of fracture can be calibrated against those data.

This paper describes the use of 3D laboratory X-ray tomography to characterise the void distribution associated with the ductile fracture in test specimens and use the data to calibrate the Gurson-Tvergaard-Needleman ductile fracture model.

The tomography successfully captures voids ≥ 6um in diameter and has been used to define the average distribution of void volume fraction as a function of distance below the fracture surface. The tomography results also allow an estimate of the critical and final void volume fractions to be made as well as capture secondary void peaks well below the fracture surface.

This distribution of voids was used to calibrate the Gurson-Tvergaard-Needleman model in order to correlate experimental observations with the finite element models. The models have been able to replicate the observed trends of the void volume fraction distributions away from the fracture surface including the secondary peaks observed by tomography and to reproduce similar J-R curve behaviour as that observed in the test specimens.
On the Estimation of Dynamic Load Factor of Thin Cylindrical Pressure Vessels in Deflagration Events
Authors: Xu Yu , Young Kuao-John
Published: November 2014

The determination of the dynamic load factor (DLF) of pressure vessels in deflagration events is essential to bridging the gap between transient dynamic pressure load and static pressure load. The static pressure load is being used by industrial codes as the basic type of load for pressure vessel design. Employing the methodology previously developed by the authors, this paper presents an analytical solution for estimating the DLF of a simply-supported thin cylindrical pressure vessel in a deflagration event. The DLF is successfully simplified as a function of four key parameters: deflagration type (non-venting or venting), pressure rise time in the deflagration event, the frequency of the fundamental extensional mode of the shell circumference, and length to diameter ratio. The master curves of DLF versus length to diameter ratio are presented for both non-venting and venting deflagration events.
Three-Dimensional Fracture Mechanics Analyses of Single-Edge Cracked Plate Specimens
Authors: Jin Zhaoyu , Wang Xin
Published: November 2014

In this paper, single-edge cracked plate (SECP) specimens are analyzed using three-dimensional finite element analysis under mode I loading conditions. The stress intensity factor K, T11 and T33 stresses along the crack front of the SECP specimens with the crack surface subjected to uniform, linear, parabolic or cubic stress distributions are calculated. The relative crack depth, a/W, is varied by 0.2, 0.4, 0.6 or 0.8. And the relative thickness, t/W, is chosen by 0.1, 0.2, 0.5, 1.0, 2.0 or 4.0, respectively. For engineering applications, empirical equations of normalized stress intensity factor K, T11 and T33 stress at the mid-plane are also obtained. By superposition, the results enable the calculations of these fracture mechanics parameters under the loading conditions of tension, bending and nonlinear stress distributions.
Implementation of a Stuctural-Acoustic Homogenized Method for the Dynamic Analysis of a Tube Bundle With Fluid Structure Interaction Modeling in ABAQUS: Formulation and Applications
Authors: Veron Eric , Sigrist Jean-François , Broc Daniel
Published: November 2014

The present paper deals with the dynamic analysis of a tube bundle with Fluid Structure Interaction (FSI) modeling using a structural acoustic homogenized method. Such a coupled problem leads to many degrees of freedom [a system of very large matrices] to compute tube displacements and pressure in the acoustic domain, it is therefore irrelevant to use standard coupled methods in industrial cases. Instead, specific modelings have to be used, such as structural acoustic homogenized method. Implementation and applications of such a technique within the general finite element code ABAQUS are performed using the so-called UEL Fortran subroutine. Firstly, general theoretical aspects on the homogenized method proposed by Broc & Sigrist are revisited. Then, subroutines developments are validated comparing results from the homogenized method to those of a standard approach on the representative case of a 10×10 tube bundle in two-dimensional and three-dimensional configurations subjected to seismic loadings. Results show that: (i) homogenized elements can easily be used as standard elements from the ABAQUS elements library, (ii) the homogenized approach is accurate on a physical point of view and (iii) considerably reduces modeling effort and computational time compared to a standard structural acoustic method.
Three-Dimensional Finite Element Simulations of Elastic and Elastic-Plastic Crack Growth Using Automated Re-Meshing Techniques
Authors: London Tyler , Smith Simon D. , Eren Şefika Elvin
Published: November 2014

This paper concerns the numerical simulation of elastic and elastic-plastic crack growth in welded components. Three-dimensional, spline-based, automatic crack re-meshing algorithms have been developed at TWI to simulate crack propagation using the commercial finite element analysis software ABAQUS. These methods allow for fatigue crack growth simulations employing the Paris law, mean stress effects and more advanced elastic crack growth laws, and incorporate nodal release techniques or iterative stationary crack methods coupled with experimentally measured tearing resistance curves for elastic-plastic crack growth. The flexibility, stability and accuracy of these numerical methods are demonstrated through several examples. The application of the crack growth simulations to full-life engineering critical assessments (ECA) of offshore structures is also described and demonstrated.
Comparison of Numerical Methods for Calculation of Vertical Soil Pressures on Buried Piping due to Truck Loading
Authors: Marohl Michael P. H.
Published: November 2014

Calculation of pressures in a soil body due to finite loads imposed on the soil surface is a necessary step in the design and analysis of buried commodities. This study compares two commonly-applied numerical methods used to develop the vertical soil pressure profiles applied to buried pipes.

The methods compared in this study differ in theory, basis, assumptions, complexity, and results, and therefore the comparison is meaningful. Provided is a comparison between design vertical forces on different sizes of buried pipes at a range of soil depth, determined using an integration of Boussinesq’s equation [1] and the method specified by AASHTO [2]. The Boussinesq equation is defined as a function of location in varying two dimensional soil planes and the integration is performed over the boundary of the pipe as well as the applied soil surface footprint. The soil surface loading considered in this study includes the AASHTO Design Truck and the AASHTO Design Tandem, positioned as required by the AASHTO LRFD code [2]. Recommendations for application of the results is provided based upon the resulting force magnitude calculated and ease of application of the methods. Consideration of the effects of redistribution of loading due to pavements or other rigid surfaces is outside the scope of this study.
Creep Life Evaluations of ASME B31.1 Allowance for Variation From Normal Operation
Authors: Cohn Marvin J.
Published: November 2014

The ASME B31.1-2012 Power Piping Code (Code) paras. 102.2.4, 102.3.3, and 104.8.2 provide an allowance regarding operating above the design temperature and internal pressure for short time periods.

This study is an evaluation of the permitted increased life consumption associated with the above Code operating allowances for piping materials operating in the creep range. Three base metal materials are considered in this study, ASTM A335 Grades P11, P22, and P91.

Two case studies were evaluated, A) 15% stress increase for 10% of the operating hours, and B) 20% stress increase for 1% of the operating hours. It was determined that these allowances increased the base metal creep rupture life consumption of Grade P11 material up to 8%, Grade P22 material up to 14%, and Grade P91 material up to 25%. Allowance A results in permitting significantly more creep damage life consumption than Allowance B.

Main steam and hot reheat piping system typical operating temperatures and stresses were evaluated for these variation allowances. This study revealed that Grade P22 base metal creep damage is slightly more sensitive to stress than Grade P11 material creep rupture damage, and Grade P91 base metal creep damage is substantially more sensitive to stress than Grade P22 material creep rupture damage.
Advanced INLAY System for Inlet/Outlet Nozzles of RV for Preventive Maintenance Against Alloy 600 PWSCC in Japanese PWR Plants
Authors: Yamamoto Kazuhide , Kizawa Masahiko , Kawazoe Hiroki , Kobayashi Yuki , Miyoshi Yoshiyuki
Published: November 2014

Since PWSCC has been observed in Alloy 600 used for butt welds between the low alloy steel RV-nozzles and stainless steel pipes in recent years, MHI has developed the inlay technology for outlet/inlet nozzles as a preventive maintenance and repair method. The inner surface, even if it has PWSCC, is exchanged from Alloy 600 to Alloy 690 which has excellent PWSCC resistance, by applying inlay.

This paper introduces the experiences of the MHI inlay System (RV-INLAY) and describes the merits as a counter measure against PWSCC. MHI has adopted the Cylindrical container for RV-INLAY. The Cylindrical container is installed into RV when the cavity is filled with water, then we can secure an atmospheric working space inside outlet/inlet nozzles. 3 or 4 manipulators are installed on the bottom of the container and carry out precise works like ambient temperature temper bead welding, UT, ECT, dimensional or visual inspection exchanging many kinds of tools (end-effectors) on the tip of the manipulators remotely. Heavy devices for machining, blast-decontamination or nozzle-plug handling are carried down into the container and set remotely using the special handling crane. Manipulators and other heavy devices move remotely to reduce the radiation exposure and simultaneously in 3 or 4 nozzles to shorten the working period. By using the Cylindrical container, we can directly access the inside outlet/inlet nozzles. This is different from the other preventive maintenance methods which need to access from outside of outlet/inlet nozzles. We can apply RV-INLAY from inside the nozzles without considering the difficulty in access due to the tight space and high radiation outside the nozzles. Furthermore when a RV is manufactured in a factory, we apply PT for the groove face before welding and the surface after welding. During RV-INLAY operation, we apply PT in the same manner because we can secure an atmospheric working space inside outlet/inlet nozzles. As a result, we can ensure the quality of welding same as manufacturing process in a shop. In addition, we don’t have to consider the crack propagation after RV-INLAY and we can perform ISI without preparing repair equipment against PWSCC. The Cylindrical container has a seal function same as the seal-plate used in usual outages, and it can separate the water inside the cavity from RCS. While the Cylindrical container is installed into RV, the RCS is drained and RCS piping works can be performed in parallel. In fact, we have shortened the outage duration by implementing RV-INLAY and RCS piping works in parallel. This is one reason why MHI has not selected under water welding but RV-INLAY.
Consistency Between Evolution of Codified Rules and SFR Prototype Development: Astrid and RCC-MRX Example
Authors: Blanc M. , Pétesch C. , Gélineau O. , Lebarbé T. , Blat-Yrieix M.
Published: November 2014

The main objective of a standard or a code is to capitalize the technical feedback of constructions. It is the case of the RCC-MR code (now RCC-MRx) which has integrated the technical results of projects such as PHENIX, SUPERPHENIX, Jules Horowitz Reactor, ITER vacuum vessel. These rules are now planned to be used for new plants and it appears that they have to be updated to meet the needs of Gen IV projects like the ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration) project or MYRRHA (Multi-purpose hybrid research reactor for high-tech applications) project.

This paper presents the ASTRID project approach to initiate in the earlier stage of the design an evaluation of the rules in order to improve as soon as possible the code. The result of this approach in terms of code modifications and improvement objectives are also presented.
Application Case of RCC-MRX 2012 Code in Significant Creep
Authors: Lejeail Yves , Lamagnère Pierre , Petesch Cécile , Lebarbé Thierry , Matheron Philippe , Martin Antoine
Published: November 2014

This paper gives an application case of the RCC-MRx mechanical design code for nuclear components in the domain of significant creep. It could be seen as a guide for engineers who have to perform mechanical creep and creep-fatigue analyses with this code. The application case is a spherical shell with an internal radius of 1250 mm and a thickness of 50 mm, which is made in AISI 316L. The structure is assembled by manual arc welding of plates using 19Cr-12Ni-2Mo type rods. The shell is intended to operate at 550°C mean temperature under an internal pressure of 5 MPa due to argon gas (the atmospheric pressure is considered outside). During operating, the internal temperature is equal to 600°C and the external temperature is 500°C. The shell is periodically stopped for servicing: during these periods, the temperature is 50°C and uniform, and the internal pressure is equal to the atmospheric pressure. A cycle is defined by a 500 h dwell time at 550°C followed by a 24 h arrest at 50°C; transient temperatures, thermal shocks during starting and arrest are neglected. The application of the RCC-MRx is shown for different damages, such as:

- Excessive strain, plastic instability and rupture for primary loadings (negligible and significant creep);

- Ratcheting, fatigue, creep-fatigue for all type of loadings.

The effect of welds on expected life (creep, fatigue), and the comparison of calculated lives and allowed operating cycles for 316L and 316LN are described.
An Investigation on Multiple Axial Surface PWSCC Growth Behaviors in Primary Alloy 600 Components Using the PWSCC Initiation Model and Damage Mechanics Approach
Authors: Kim Jong-Sung , Heo Eun-Ju , Jeon Jun-Young , Kim Yun-Jae
Published: November 2014

The paper proposes a new numerical method to predict the growth behavior of the multiple PWSCCs in the primary alloy 600 components. The method based on the PWSCC initiation model and macroscopic phenomenological damage mechanics approach can induce same results irrespective of the element size. The assessment method was verified comparing with the previous study results. The verified method was applied to collinear and parallel axial surface cracks. As a result, for the collinear crack, the penetration times of the collinear cracks are earlier than those of the single cracks, and the penetration time increases with increasing the space between two cracks. For the parallel crack, the penetration times of the parallel cracks are later than those of the single cracks, and the penetration time increases with decreasing the space between two cracks.
Fitness for Service Assessment of a Packed Column Subjected to Fire Damage
Authors: Shao Shanshan , Cao Luowei , Li Zhifeng , Liu Jianjun
Published: November 2014

When pressure vessels are subjected to fire damage, they maybe deform partially and the mechanical properties of materials would be degraded. Fitness for service assessment can help to minimize reconstruction costs and allow safe resumption of unit operation as fast as possible. The safety of a packed column subjected to fire damage due to spontaneous combustion of FeS during a shutdown period is assessed according to API 579-1/ASME FFS-1. First, the highest temperature during the fire accident was estimated. The possible damage was examined by hardness test, dimensional checks, in-situ field metallography, ultrasonic test and penetration test. The Heat Exposure Zones were defined based on the results of visual inspection and test. The plates containing Widmanstätten or localized distortions were replaced. The column leaned with the vertical deviation of 85mm which could not satisfy the requirement of the national standard GB 50461-2008. The finite element method is adopted to analyze the influence of the vertical deviation with the consideration of wind loading. The analytical results show that the vertical deviation of 85mm has no significant effect on the safe operation of the column before the next inspection.
Stress Intensification Factors for Unreinforced Elbow Branch Connections in Old Carbon-Steel Pipelines
Authors: Scano Lorenzo
Published: November 2014

Unreinforced branch connections are a typical component of steel pipelines, designed and manufactured according to the piping code standards of reference. These joints are constructed welding together two straight pipes at different angles respect to their axis and the Stress Intensification Factors (SIFs) of the welded area are readily available from the standards for stress analysis purposes. Nevertheless, branches manufactured using elbows are occasionally encountered during Fitness-For-Service evaluations of the older carbon-steel pipelines conveying fluids at low pressure and room temperature. In the present paper the SIFs for these peculiar joints were determined using FEA and compared with those obtained by FEA and by code for the classic 90° unreinforced branch connections manufactured with straight pipes. 42 tees were considered in the analysis with diameters ranging from 3″ to 10″ on the run side and from 2″ to 10″ on the branch side; thicknesses from piping Schedule 10, 40 and 80 were adopted in the investigation and long radius elbows were only considered. The SIFs for the elbow branch tees were found to be 1.1 to 1.35 times those of the standard joints for unitary diameter ratios and 0.8 to 1.1 in the other cases. The maximum SIF (out-of-plane branch) was found to be linearly related to the elbow flexibility. A simple formula was then proposed to conservatively calculate the SIFs of the elbow branch connections using the values provided by the codes for a standard stress analysis where the joint is modeled with straight pipes. Finally, the elbow tees were evaluated against fatigue via solid FEA obtaining a lower estimate of their safe life respect to the standard joints.