bluuebunny/crossref_metadata_2025 huggingface dataset:
Dissociation of dysfunctional breathing and odour intolerance among adults in a general‐population study
Authors: Bonde Ellen , Andersson Eva , Brisman Jonas , Eklöf Mats , Ringsberg Karin C. , Torén Kjell
Published: May 2012

Background:  Many patients present with a mixture of respiratory problems such as shortness of breath, heavy breathing, coughing and odour intolerance. If these patients are diagnosed as asthma, it might sometimes be a false diagnosis. Concepts such as sensory hyperreactivity, hyperventilation, asthma‐like symptoms, odour intolerance and dysfunctional breathing are used to refer to these patients. Non‐respiratory symptoms such as headache, fatigue and bloating are sometimes also part of the clinical picture. Our aim was to use factor analysis to increase our understanding of breathing‐related symptoms in a general‐population frame.

Methods:  A respiratory questionnaire was answered by 10 108 subjects in a general‐population sample. Items aiming to identify individuals with breathing‐related symptoms and asthma were included. We used factor analysis with Varimax rotation to extract discriminatory components (i.e. groups of symptoms), based on the questionnaire items. The aim was to find groups of items (factors) as distinct as possible, still allowing overlap and showing the importance of each item in the separated factor.

Results:  Five distinct factors were identified in the factor analysis, representing dysfunctional breathing, odour intolerance, asthma, bronchitis and a group with mixed symptoms, respectively. These five factors explained 55% of the variance.

Conclusions:  Based on our findings, we conclude that non‐asthmatic breathing‐related symptoms may be separated into at least two categories in a general population, odour intolerance and dysfunctional breathing. These two categories seem to be two distinct groups of subjects with breathing‐related symptoms and may represent different clinical entities separated from asthma and bronchitis.

Please cite this paper as: Bonde E, Andersson E, Brisman J, Eklöf M, Ringsberg KC and Torén K. Dissociation of dysfunctional breathing and odour intolerance among adults in a general‐population study. Clin Respir J 2013; 7: 176–182.
Assessing the potential of wildfires as a sustainable bioenergy opportunity
Authors: Verón Santiago R. , Jobbágy Esteban G. , Di Bella Carlos M. , Paruelo José M. , Jackson Robert B.
Published: May 2012

As the environmental and economic consequences of fossil‐fuel use become clear, land is increasingly targeted as a source of bioenergy. We explore the potential for generating electricity from biomass vulnerable to fires as an ecologic and socioeconomic opportunity that can reduce the risk of greenhouse gas generation from wildfires and help to create incentives to preserve natural and seminatural vegetation and prevent its conversion to agriculture, including biofuel crops. On the basis of a global analysis of the energy generation and spatial distribution of fires, we show that between 2003 and 2010, global fires consumed ~8300 ± 592 PJ yr−1 of energy, equivalent to ~36–44% of the global electricity consumption in 2008 and >100% national consumption in 57 countries. Forests/woodlands, cultivated areas, shrublands, and grasslands contributed 53%, 19%, 16%, and 3.5% of the global energy released by fires. Although many agroecological, socioeconomic, and engineering challenges need to be overcome before diverting the energy lost in fires into more useable forms, done cautiously it could reconcile habitat preservation with economic yields in natural systems.
Time-Linearized and Time-Accurate 3D RANS Methods for Aeroelastic Analysis in Turbomachinery
Authors: Kersken Hans-Peter , Frey Christian , Voigt Christian , Ashcroft Graham
Published: May 2012

A computational method for performing aeroelastic analysis using either a time-linearized or an unsteady time-accurate solver for the compressible Reynolds averaged Navier--Stokes (RANS) equations is described. The time-linearized solver employs the assumption of small time-harmonic perturbations and is implemented via finite differences of the nonlinear flux routines of the time-accurate solver. The resulting linear system is solved using a parallelized generalized minimal residual (GMRES) method with block-local preconditioning. The time accurate solver uses a dual time stepping algorithm for the solution of the unsteady RANS equations on a periodically moving computational grid. For either solver, and both flutter and forced response problems, a mapping algorithm has been developed to map structural eigenmodes, obtained from finite element structural analysis, from the surface mesh of the finite element structural solver to the surface mesh of the finite volume flow solver. Using the surface displacement data an elliptic mesh deformation algorithm, based on linear elasticity theory, is then used to compute the grid deformation vector field. The developed methods are validated first using standard configuration 10. Finally, for an ultra-high bypass ratio fan, the results of the time-linearized and the unsteady module are compared. The gain in prediction time using the linearized methods is highlighted.
A Numerical Study of the Flow and Heat Transfer in the Pin Fin-Dimple Channels With Various Dimple Depths
Authors: Rao Yu , Xu Yamin , Wan Chaoyi
Published: May 2012

A numerical study was conducted to investigate the effects of dimple depth on the flow and heat transfer characteristics in a pin fin-dimple channel, where dimples are located spanwisely between the pin fins. The study aimed at promoting the understanding of the underlying convective heat transfer mechanisms in the pin fin-dimple channels and improving the cooling design for the gas turbine components. The flow structure, friction factor, and heat transfer performance of the pin fin-dimple channels with various dimple depths have been obtained and compared with each other for the Reynolds number range of 8200–80,800. The study showed that, compared to the pin fin channel, the pin fin-dimple channels have further improved convective heat transfer performance, and the pin fin-dimple channel with deeper dimples shows relatively higher Nusselt number values. The study still showed a dimple depth-dependent flow friction performance for the pin fin-dimple channels compared to the pin fin channel, and the pin fin-dimple channel with shallower dimples shows relatively lower friction factors over the studied Reynolds number range. Furthermore, the computations showed the detailed characteristics in the distribution of the velocity and turbulence level in the flow, which revealed the underlying mechanisms for the heat transfer enhancement and flow friction reduction phenomenon in the pin fin-dimple channels.
Optimum Geometry of Plate Fins
Authors: Karvinen R. , Karvinen T.
Published: May 2012

A method and practical results are presented for finding the geometries of fixed volume plate fins for maximizing dissipated heat flux. The heat transfer theory used in optimization is based on approximate analytical solutions of conjugated heat transfer, which couple conduction in the fin and convection from the fluid. Nondimensional variables have been found that contain thermal and geometrical properties of the fins and the flow, and these variables have a fixed value at the optimum point. The values are given for rectangular, convex parabolic, triangular, and concave parabolic fin shapes for natural and forced convection including laminar and turbulent boundary layers. An essential conclusion is that it is not necessary to evaluate the convection heat transfer coefficients because convection is already included in these variables when the flow type is specified. Easy-to-use design rules are presented for finding the geometries of fixed volume fins that give the maximum heat transfer. A comparison between the heat transfer capacities of different fins is also discussed.
Medical Device Innovators and the 510(k) Regulatory Pathway: Implications of a Survey-Based Assessment of Industry Experience
Authors: Pietzsch Jan B. , Zanchi Marta G. , Linehan John H.
Published: May 2012

Medical device regulation plays a significant role in promoting and protecting the public health. But the regulatory process and its requirements also exercise substantial influence over the design, development, and commercialization of new medical technologies. In recent months, FDA’s premarket notification (510(k)) process, through which the majority of medical devices are cleared to the market, has been at the forefront of policy discussions, and efforts are continuing to further analyze and strengthen the process. In this paper, we report findings from our recently completed, comprehensive, industry-wide survey to provide input and perspective for the current discussions about changes to the 510(k) process. The findings reported here focus on five aspects of the 510(k) process with principal relevance to medical technology developers and innovators: predictability of the process, impact of regulatory requirements, role of guidance documents, interaction with FDA, and international comparisons. The results confirm the substantial influence of regulatory requirements on investment decisions and development priorities. The data suggest that improvement of regulatory process predictability needs to be a top priority for all stakeholders – especially FDA. Increasing the number of guidance documents available to industry, and ensuring that their content is timely updated to reflect current FDA thinking, could be one way to achieve this goal. Consistent implementation of the regulatory process and enhanced communications between sponsors and the agency could further contribute to improvements, along with efforts to provide additional training opportunities for reviewers and industry personnel. The survey data suggest that small companies, when compared to large companies, are particularly challenged by the current process, and should therefore receive particular attention in any reform and improvement efforts.
Statistical Sampling for In-Service Inspection of Liquid Waste Tanks at the Savannah River Site
Authors: Baxter Lindsay R. , Harris Stephen P.
Published: May 2012

Savannah River Remediation, LLC (SRR) is implementing a statistical sampling strategy for in-service inspection (ISI) of liquid waste (LW) tanks at the United States Department of Energy’s Savannah River Site (SRS) in Aiken, South Carolina. As a component of SRS’s corrosion control program (CCP), the ISI program assesses tank wall structural integrity through the use of ultrasonic testing (UT). The statistical strategy for ISI is based on the random sampling of a number of vertically oriented unit areas, called “strips,” within each tank. The number of strips to inspect was determined so as to attain, over time, a high probability of observing at least one of the worst 5% in terms of pitting and corrosion across all tanks. The probability estimation to determine the number of strips to inspect was performed using the hypergeometric distribution. Statistical tolerance limits for pit depth and corrosion rates were calculated by fitting the lognormal distribution to the data. In addition to the strip sampling strategy, a single strip within each tank was identified to serve as the baseline for a longitudinal assessment of the tank safe operational life. The statistical sampling strategy enables the ISI program to develop individual profiles of LW tank wall structural integrity that collectively provide a high confidence in their safety and integrity over operational lifetimes.
A Limiting Defect Study of an Elbow
Authors: Shi Jinhua , Blythe David
Published: May 2012

In order to ensure the integrity of a seamless butt-welding elbow, both the central section and ends of the elbow need to be assessed, as the maximum stress is normally located at the central section of the elbow but there are no welding residual stresses. Furthermore, at the ends (welds) of the elbow, very high welding residual stresses exist if the welds have not been post weld heat treated but the primary stresses induced by the internal pressure and system moments are lower. For a 90 degree elbow welded to seamless straight pipe, both maximum axial and hoop stress components in the elbow can be calculated using ASME III NB-3685. At the ends of the elbow, axial and hoop stress components can be obtained using the stress equations presented in the paper of PVP2010-25055. In this paper, a series of limiting defect assessments have been carried out on an elbow assuming a postulated axial external defect as follows: • A number of assessments have been conducted directly using the axial and hoop stresses calculated based on ASME III NB-3685 for different system moments. • A series of assessments have been carried out using the axial and hoop stresses calculated using the stress equations presented in the paper of PVP2010-25055, a wide range of welding residual stresses and different system moments. A comparison of the assessment results in the elbow and at the ends of the elbow shows that when system moments are relatively low and the welding residual stress is high, the limiting defect size is located at the ends of the elbow; when the system moments are high and the welding residual stress is low the limiting defect size is located at the central section of the elbow. Therefore, it can be concluded that when assessing an elbow, the assessments should be carried out at both the central section and the ends of the elbow, in order to ensure the integrity of the elbow.
RCC-M: Content, Working Approach and Future Evolutions
Authors: Malouines Philippe , Grandemange Jean-Marie
Published: May 2012

The paper covers the general approach followed by AFCEN, the French Society for Design, Construction and In-Service Inspection Rules for Nuclear Island Components, in codes and standards establishing, from the technical and organizational points of views. The RCC-M code is the major reference code existing since the creation of AFCEN. The presentation highlights how the industrial experience was integrated into the industrial codes, and how codes evolve taking into account the evolution of regulations and European and International standards. Processes for updates, interpretations and inquiries are addressed. Recent code evolutions resulting from the New French Nuclear Pressure Equipment Regulation issued in 2005, as well as from the project needs, are covered and the content of the addenda 2008, 2009, 2010 to the 2007 RCC-M edition are described. Future evolutions are also addressed, giving the frame for the objective of a new RCC-M edition in 2012.
LES CFD Simulation of Unsteady Fluid Forces in Tube Bundle
Authors: Delafontaine Serge , Ricciardi Guillaume , Collard Bruno
Published: May 2012

Significant nuclear fuel assembly design innovations are regularly incorporated to meet the highest expectations in terms of safety, performance and flexibility. Despite the continuous upgrades of fuel designs and materials, the fuel failure rate has not markedly decreased during the last decade, partly because of higher burn-up, longer cycle lengths, mixed cores… Safety aspects give rise to the reduction of contamination and the fuel cladding represents the first containment barrier. It is then necessary to maintain its integrity under all operating conditions. Flow-induced vibrations of fuel rods generating grid-to-rod fretting are the dominant fuel leaker mechanism worldwide. This paper presents a Computational Fluid Dynamics (CFD) simulation of the flow around a fuel rod. The swirls generated by the mixing vanes are reproduced, and the corresponding resulting fluid force excitations are extracted. The computed spectra are compared to envelop spectra obtained by tests on fuel assembly mock-ups in our experimental facilities.
Wake Formation for an Oscillating Small-Incidence-Angle Cylinder Pair in Cross-Flow
Authors: Hayder Mir M.
Published: May 2012

The wake region of a pair of equal-diameter staggered circular cylinders in cross-flow is investigated experimentally for Reynolds numbers, based on the mean flow velocity, U, and the cylinder diameter, D, within the range 540 ≤ Re ≤ 755. The centre-to-centre pitch ratio and stagger angle of the cylinders at their mean position are P/D = 2.0 and α = 16°, respectively. In an earlier study, wake formation of a small-incident-angle cylinder pair was investigated for forced oscillation (transverse to the flow direction) of the upstream cylinder only. The present study is aimed to reveal the modification of the wake when the oscillation is shifted from the upstream to downstream cylinder or vice versa. Results with cylinder excitation frequencies in the range 0.07 ≤ feD/U ≤ 1.10 are reported. It is observed that for both upstream and downstream cylinder oscillations with frequency feD/U ≤ 0.10 the wake flow patterns remain essentially the same as those of the corresponding static cases. However, for frequency feD/U > 0.10 the wake undergoes considerable modification vis-a`-vis when the cylinders are stationary, and the flow pattern within the wake is strongly dependent on feD/U value. As also observed in the previous study, there are distinct regions of synchronization between the dominant wake periodicities and the cylinder oscillation over the whole range of feD/U. These synchronizations involve sub- and super-harmonics as well as fundamental synchronizations and are the result of the formation of two rows of vortices, one on either side of the combined wake of the cylinder pair. The manner in which the wake responds to the cylinder oscillation depends strongly on whether it is the upstream or downstream cylinder which is oscillating. Flow-visualization images suggests that the synchronizations on the mean-flow side of the downstream cylinder occur from the outer vortices shed by the downstream cylinder, and those on the mean-flow side of the upstream cylinder occur from the vortices formed by the interaction of the two gap shear layers and the outer shear layer separated from the upstream cylinder.
Failures of Locally Reinforced Pipelines
Authors: Shuai Jian , Liu Wei , Bu Wenping , Wang Xiaolin
Published: May 2012

Enormous attention has been attracted to the safety issues regarding numerous pipelines that have had to be repaired by such local reinforce as welding a tube-cap or patch. The present paper provides a detail description of experimental and numerical research conducted to evaluate the structural condition of locally reinforced pipelines, subjected to internal pressure including cyclic load. Six full-scale pipe specimens are tested under pressure to determine their loading capacity. Their stress distributions are measured, and their stress concentrations and plastic limit loads are analyzed. The result of the present study demonstrates that the burst pressure may not be affected by welding either a tube-cap or patch and cyclic loading, but the plastic limit loads of the repaired pipelines decreased respect to undamaged pipeline, among which the lowest one decreased up to 85% of that of the undamaged pipeline. It is also found that on the pipeline repaired by a single tube-cap or patch the burst occurred away from the welding sites, whereas on the pipeline included several tube-caps in short span the burst took place between the two adjacent tube caps, suggesting that multi-cap repair is disadvantageous to the loading capability of the pipelines. In addition, using nonlinear finite element tools, stresses state in locally reinforced pipeline is calculated. It is showed that bulging occurs in long and narrow area in the pipe along longitudinal direction, addressing where burst rupture occur.
Vibration Excitation Forces in a Normal Triangular Tube Bundle Subjected to Two-Phase Cross Flow
Authors: Perrot E. S. , Mureithi N. W. , Pettigrew M. J. , Ricciardi G.
Published: May 2012

This paper presents test results of vibration forces in a normal triangular tube bundle subjected to air-water cross-flow. The dynamic lift and drag forces were measured with strain gage instrumented cylinders. The array has a pitch-to-diameter ratio of 1.5, and the tube diameter is 38 mm. A wide range of void fraction and fluid velocities were tested. The experiments revealed significant forces in both the drag and lift directions. Constant frequency and quasi-periodic fluid forces were found in addition to random excitation. These forces were analyzed and characterized to understand their origins. The forces were found to be dependent on the position of the cylinder within the bundle. The results are compared with those obtained with flexible cylinders in the same tube bundle and to those for a rotated triangular tube bundle. These comparisons reveal the influence of quasi-periodic forces on tube motions.
Tensile Characterization of a GTAW Bimetallic Weld Mod 9Cr-1Mo–316L(N) With a New Measurement System for Tensile Testing
Authors: Ancelet O. , Perez G. , Forest L.
Published: May 2012

Mod 9Cr-1Mo steel (T91) is a candidate material for steam generator of SFR (Sodium Fast Reactors). In order to validate this choice, it is necessary, firstly to verify that it is able to withstand the planned environmental and operating conditions, and secondly to check if it is covered by the existing design codes, concerning its procurement, fabrication, welding, examination methods and mechanical design rules. A large R&D program on mod 9Cr-1Mo steel has been undertaken at CEA in order to characterize the behavior of this material and of its welded junctions. In this frame, a new measurement system for tensile testing was developed in the laboratory of structural integrity and standards (LISN) of the CEA (French atomic commission), in order to characterize the local behavior of the material during a whole tensile testing. Indeed, with the conventional measurement system (typically an extensometer), the local behavior of the material can only be determined during the stable step of the testing. So, usually the behavior of the material during the necking step of the step is unknown. This new measurement is based on the use of some laser micrometers which allow measuring the minimum diameter of the specimen and the curvature radius during the necking phase with a great precision. Thanks to the Bridgman formula, we can evaluate the local behavior of the material until the failure of the specimen. This new system was used to characterize the tensile propriety of a bimetallic welded junction of Mod 9Cr-1Mo steel and austenitic stainless steel 316L(N) realized with GTAW process and inconel filler metal. These works lead to propose a tensile curve for each materials of the welded junction.
Polarization Curve Modeling With Flow Properties
Authors: Suga Kazuhiro , Kikuchi Masanori , Moteki Taro , Arimura Ryoma
Published: May 2012

The present study proposes a concept of corrosion prediction under flow fields. In the concept, polarization curves in pracical condions are estimated from flow properties based on some polarization curved obtained by simple examinations. In order to achieve it, the study developed a measurement system to characterize corrosion conditions by flow properties. The system allowed the real-time observation of the transition of specimen surface using a channel made of transparent acrylic and micro scope and evaluation of flow properties by computational fluid dynamics. An experiment was carried out to demonstrate the function of the system.
A Numerical Characterization of Flow-Induced Vibration and Fretting Wear Potential in Nuclear Steam Generator Tube Bundles
Authors: Hassan Marwan , Mohany Atef
Published: May 2012

Nuclear power plants have experienced problems related to tube failures in steam generators. While many of these failures have been attributed to corrosion, it has been recognized that flow-induced vibrations contribute significantly to tube failure. In order to avoid these excessive vibrations, tubes are stiffened by placing supports along their length. Various tube/support geometries have been used, but the majority are either support plates (plates with drilled or broached holes) or flat bars. Unfortunately, clearance is often considered necessary between the tubes and their supports to facilitate tube/support assembly and to allow for thermal expansion of the tubes. A combination of flow-induced turbulence and fluidelastic forces may then lead to unacceptable tube fretting-wear at the supports. The fretting wear damage could ultimately cause tube failure. Such failures may require shut downs resulting in production losses, and pose potential threats to human safety and the environment. Therefore, it is imperative to predict the nonlinear tube response and the associated fretting wear damage to tubes due to fluid excitations. Tubes in loose flat-bar supports have complex dynamics due to the possible combinations of geometry. The understanding of tube dynamics in the presence of this type of support and the associated fretting wear is still incomplete. These issues are addressed in this paper through simulations of the dynamics of tubes subjected to crossflow turbulence and fluidelastic instability forces. The finite element method is utilized to model the vibrations and impact dynamics. The tube model simulates a U-tube supported by 16 flat bars with clearances and axial offset. Results are presented and comparisons are made for the parameters influencing the fretting-wear damage such as contact ratio, impact forces and normal work rate. The effect of support clearance and support axial offset are investigated.
Stress Concentration at the Root of Bolt Thread Under Twist With Deformable Flanges
Authors: Shoji Yasumasa , Sawa Toshiyuki
Published: May 2012

Bolts and Nuts are required to fasten objects, such as flanges in various types of plants. It is known that stress concentration at the root is relevant for its strength for both static integrity and fatigue. A lot of investigations were carried out to understand the behavior of the bolt using experimental and numerical methods. Recently, finite element analyses have been used to examine the detailed behavior of the bolt root successfully. The authors reported such example in a recent study [13] using submodelling (or so-called zooming) technique that handled only bolt tension with rigid fastened surface; some factors were missing. In this paper, the twist of the bolt was taken into account and the fastened object is replaced by deformable plates. The stress concentration factor has been reconsidered.
Crack Propagation Simulation: A Local Deformation-Based Mesh Mapping Method for Crack Modeling and a Direct Method for Residual Stress Representation in Welds
Authors: Xu Heqin , Mahmoud Samer , Nana Ashok , Killian Doug
Published: May 2012

Cracks found in a nuclear power plant reactor coolant system (RCS), such as primary water stress corrosion cracking (PWSCC) and intergranular stress corrosion cracking (IGSCC), usually have natural crack front shapes that can be very different from the idealized semi-elliptical or rectangular shapes considered in engineering handbooks and other analytical solutions based on limited shapes. Simplifications towards semi-elliptical shape or rectangular shape may potentially introduce unnecessary conservatism when the simplified shape has to contain the actual crack shape. On the other hand, it is very time-consuming to create a three-dimensional (3D) finite element (FE) model to simulate crack propagation in a natural shape using existing public-domain software like ABAQUS or ANSYS. In this study, a local deformation-based mesh-mapping (LDMM) method is proposed to model cracks with a natural front shape in any 3D structures. This methodology is first applied to model circumferential surface cracks with a natural crack front shape in the cross-sectional plane of a cylinder. The proposed new method can be applied to simulate both shallow and deep cracks. Also discussed in this paper is a direct method to reproduce welding residual stresses in the crack model using temperature fields combined with other sustained loads to predict crack propagations. With this novel LDMM method, natural crack fronts and non-planar crack faces can be easily modeled. The proposed new method can be used to generate a high-quality finite element model that can be used for both linear-elastic fracture mechanics (LEFM) and elastic-plastic fracture mechanics (EPFM) analyses. The study case illustrates that the proposed LDMM method is easy to implement and more efficient than the existing commercial software.
Mechanical Behaviour of SFR Materials: Proposition of Fatigue Weld Joint Coefficient for Mod9Cr-1Mo
Authors: Ancelet O. , Matheron Ph.
Published: May 2012

Mod 9Cr-1Mo steel (T91) is a candidate material for steam generator of SFR (Sodium Fast Reactors). In order to validate this choice, it is necessary, firstly to verify that it is able to withstand the planned environmental and operating conditions, and secondly to check if it is covered by the existing design codes, concerning its procurement, fabrication, welding, examination methods and mechanical design rules. A large R&D program on mod 9Cr-1Mo steel has been undertaken at CEA in order to characterize the behavior of this material and of its welded junctions. In this program, the role of the Laboratory for structural Integrity and Standards (LISN) is to develop high temperature defect assessment procedures under fatigue and creep loadings. In this frame, complementary studies are conducted in order to validate the existing methods (developed for the fast reactors) and to get new experimental data on Mod 9Cr-1Mo steel. In particular, some new experiments are conducted on specimen with a weld joint and compared with classical experiments on base metal specimen. These results associated with finite element modeling allow to propose a weld joint coefficient at 550°C for the Mod9Cr 1Mo steel.
Shakedown and Fatigue Evaluations of Overlay Cladding on Reactor Pressure Vessels
Authors: Asada Seiji , Suzuki Harutaka , Saruwatari Toshiya
Published: May 2012

Overlay cladding is classified to non-pressure boundary. Not only the ASME Boiler & Pressure Vessels Code Section III [1] but also the JSME Design and Construction Code [2] prescribe that no structural strength shall be attributed to cladding and the presence of the cladding shall be considered with respect to both the thermal analysis and the stress analysis. This means the codes do not require stress evaluation for overlay cladding itself. If overlay cladding has a fatigue crack, the crack may grow and extend to the base metal. Thus overlay cladding may give an influence on the integrity of base metal in the pressure boundary. The thermal expansion of stainless steel cladding is different from that of base metal made of low alloy steel, and this difference causes discontinuity of stress distribution between the cladding and the base metal. It is questionable that a stress evaluation line is set on such stress distribution including discontinuity between the cladding and the base metal. An evaluation method based on elastic-plastic analysis is preferable to evaluate such portion. ASME B&PV Sec.III and Sec.VIII, Div. 2 [3] have plastic analysis provisions. Also the JSME D&C Code issued a code case on alternative design methodology by using elastic-plastic finite element analysis for Class 1 vessels [4, 5]. In this paper, shakedown, fatigue and environmental fatigue evaluations are performed for the overlay cladding of direct vessel injection nozzle of Reactor Pressure Vessel by using the JSME Code Case on the alternative design methodology.
Comparison on Mechanical Behavior of Bolted Flanges Per Old and New Section VIII Division 2
Authors: Terada Susumu , Nishihara Tatsuo , Suzuki Tomohiro
Published: May 2012

The allowable stress for 2.25Cr 1Mo 0.25V steel per ASME Section VIII Div.2 2007 edition (hereinafter called New Div2) becomes higher than that per old Div.2. Therefore the thickness of flange can be thinner than that per old Div.2. The internal fluid leakage is main concern as well as stress level especially for large size flanges per New Div.2. In this paper the analysis method using axi-symmetric model are investigated and the numerical analyses using axi-symmetric models for two types of flange design are performed in order to compare the flange rotation, gasket contact stress and stress level of flange and bolts. The contact stress of New Div.2 flange was lower than that of Old Div.2 flange totally. However the maximum gasket contact stress of New Div.2 flange which occurred at outer edge of the gasket is almost same as that of Old Div.2. Therefore it is expected that the sealing performance of flange connections per both Old Div.2 and New Div.2 is almost same.
Numerical Simulation of the Flow-Sound Interaction Mechanisms of Two Side-by-Side Cylinders in Cross-Flow
Authors: Mohany Atef , Hassan Marwan , Ziada Samir
Published: May 2012

A numerical simulation of the flow-excited acoustic resonance for the case of two side-by-side cylinders in cross-flow is performed. One spacing ratio between the cylinders, T/D = 1.25, is investigated, where D is the diameter of the cylinders and T is the center-to-center distance between them. The unsteady flow field is simulated using a finite-volume method at a Reynolds number of 25000. This simulation is then coupled with a finite element simulation of the resonant sound field, by means of Howe’s theory of aerodynamics sound, to reveal the details of flow-sound interaction mechanisms, including the nature and the locations of the aeroacoustic sources in the flow field. At the off resonance conditions two distinct vortex shedding frequencies are observed. These are associated with the wider and narrower wakes of the cylinders. However, when acoustic resonance is initiated the bi-stable flow phenomenon is eliminated and the vortex shedding from both cylinders occurs at a single frequency that is between those observed before the onset of acoustic resonance. Moreover, three main aeroacoustic sources are observed in the wake of the two cylinders. Two aeroacoustic sources are located just downstream of each cylinder and one aeroacoustic source is located in the gap between the cylinders. The numerical results are compared with the experimental results presented in a previous investigation and favourable agreement is obtained.
Theoretical and Experimental Analysis of the Non-Linear Characteristics of an Air Spring With an Orifice
Authors: Yokota Yasutaka , Asami Toshihiko , Ise Tomohiko , Honda Itsuro , Sakamoto Hiroya
Published: May 2012

This paper proposes a simple but accurate method for calculating the dynamic properties of an air spring employing an orifice to produce a damping force. Air springs are very common in rail, automotive, and vibration isolation applications. However, because this type of air spring has non-linear flow characteristics, an accurate model is yet to be proposed. The restoring and damping forces in an air spring with an orifice damper vary with amplitude. This amplitude dependency has not been considered in previous studies. Proposed herein is a simple model for calculating the air spring constant and damping coefficient. However, iterative calculation is required due to the non-linearity of the spring. The theoretical and experimental results are found to agree well. The theoretical equations provide an effective tool for air spring design.
The Evaluation of Crack Opening Areas for Through-Wall Cracks in the Vicinity of Pipe Branch Connections
Authors: Madew Colin , Sharples John , Charles Richard , Gill Peter , Budden Peter
Published: May 2012

A number of papers have been presented at previous ASME PVP conferences, which have evaluated the crack opening areas (COA) and stress intensity factors (K), using elastic finite element analysis techniques, for through-wall cracks in a region where an attachment is welded to a plate. This was a simplified geometry aimed at representing a more complicated geometry of a pipe-branch connection. A number of analyses were considered and conclusions made on the estimation of COA and K using simple handbook solutions. More recently the analyses included the application of nonlinear geometry and the addition of crack face contact when applying bending loads. This paper is a continuation of these previous studies, assessing through-wall cracks in a more realistic pipe-branch connection geometry. The calculated COA and K values for the more complex geometry are compared to values from pipe models with no branch connections, in a similar manner to that applied in the previous work on the simplified plate geometry. Judgments are made on the conservatism, or otherwise, of the estimated COA and K for the more complex geometry solutions compared to the simple geometry solutions.
Continuous Creep Damage Monitoring Using a Novel Potential Drop Technique
Authors: Davies Catrin M. , Nagy Peter , Narayanan Aditya , Cawley Peter
Published: May 2012

A new directional low-frequency Alternating Current Potential Drop (ACPD) technique has been developed for continuous in-situ monitoring of creep strain and damage in alloys. The sensor relies on a modified ACPD technique that measures simultaneously both values of resistance in the axial and lateral directions using a square electrode configuration. The technique monitors the variation in the ratio of the measured axial and lateral resistances, therefore can efficiently separate the mostly isotropic common part of the resistivity variation caused by reversible temperature variations from the mostly anisotropic differential part caused by direct geometrical and indirect material effects of creep. Initially, this ratio can be considered proportional to the axial creep strain, while at later stages, the resistance ratio accelerates due to the formation of directional discontinuities such as preferentially oriented grain boundary cavities and micro-cracking in the material. This ACPD technique has been applied to a series of accelerated creep tests on 2.25CrMoV Steel at 650 °C. The results are presented and the application of the method for online component monitoring is discussed.
LOCA Simulation: Analysis of Rarefaction Waves Propagating Through Geometric Singularities
Authors: Crouzet Fabien , Faucher Vincent , Galon Pascal , Piteau Philippe , Izquierdo Patrick
Published: May 2012

The propagation of a transient wave through an orifice is investigated for applications to Loss Of Coolant Accident in nuclear plants. An analytical model is proposed for the response of an orifice plate and implemented in the EUROPLEXUS fast transient dynamics software. It includes an acoustic inertial effect in addition to a quasi-steady dissipation term. The model is experimentally validated on a test rig consisting in a single pipe filled with pressurized water. The test rig is designed to generate a rapid depressurization of the pipe, by means of a bursting disk. The proposed model gives results which compare favourably with experimental data.
Effect of Oxide Film Mechanical Property on Stress Corrosion Cracking Growth Rate
Authors: Tang Wei , Xue He , Zhao Dan , Fang Xiurong
Published: May 2012

Stress corrosion cracking (SCC) of austenitic stainless steel and nickel-based alloys in high temperature water is one of the key issues for the structural safety and service life of nuclear power plant. The mechanical properties of oxide film would be changed due to the water environment and metal at the crack tip, which have been observed in laboratory stress corrosion cracking tests. The crack growth rate is affected by the deformation-oxidation process of oxide film in SCC tip. In other word, the crack growth rate is also influenced by the mechanical properties of oxide film. To understand the mechanical state at crack tip accurately, the meso-scale stress-strain on the crack tip is analyzed using finite element software ABAQUS. The effect of oxide film mechanical property on stress-strain field at the tip of the SCC is analyzed, which provides a new insight into the research of the mechanism of SCC growth in structural materials in high temperature water environments.
Management of PWR Steam Generator Tube Plugging and Primary Flow-Rate Predictions
Authors: Brunin Olivier
Published: May 2012

The tubes of PWR steam generators are part of the second barrier between the nuclear fuel and the environment. The integrity in operation of the tubes is addressed with Non Destructive Examinations (NDE) and flaw allowances criteria. If a tube does not match the criteria, it is plugged. As a consequence, the steam generators tube plugging (SGTP) may increase during the maintenance outages. This increase has to be managed properly because it basically affects the heat exchange capacity of the Nuclear Steam Supply System (NSSS). This can be managed by performing long-term predictions in order to prepare in advance the possibility of steam generator replacements. But this “long-term operation” management is to be completed with an intermediate term management considering the real operating conditions of the NSSS. Intermediate term predictions, based on a simulation of the mechanisms leading to the degradation of the tubes, are annually compared with the evolution of real NDE and real SGTP. These predictions are completed with the set-up of a model, for each Reactor Coolant System (RCS), considering the relation between the average SGTP and the primary flow-rate. The predictions are used to check that the real operating conditions of each NSSS can be matched with an existing safety file.
Anti-Seize, Friend or Foe, the Properties That Really Matter!
Authors: Oldiges Don , Reeves David , Garrison Wesley
Published: May 2012

There is a lot of misinformation published about anti-seize compounds around friction (or K factors) factors and temperature limits. Anti-seize materials exist to serve two functions, to help even out stud stresses/preloads during assembly, and most importantly, allow the components to be taken apart after they have been exposed to heat. This paper looks at how different anti-seize materials are affected after being exposed to enough heat to burn off the grease base.
Research and Application on Mechanical Behavior of Austenitic Stainless Steels for Cold Stretched Pressure Vessel
Authors: Han Yu , Chen Xuedong , Liu Quankun
Published: May 2012

Austenitic stainless steels (ASS) have good ductility and toughness but low yield strength. In order to save material and realize lightweight of pressure vessels, the cold stretching technology can be used to enhance ASS’s yield strength. Based on the control of different strain, the material parameters of strength, ductility and volume fraction of strain-induced martensite (SIM) were obtained. The results show that cold stretching can significantly improve ASS’s yield strength and have minor effect on material’s plasticity and content of SIM. The ASS still maintain enough plastic margin after cold stretching and thus can substantially reduce the wall thickness of vessel. In the quasi-static conditions, the mechanical parameters are not sensitive to strain rate. However, too small strain rate will lead to occurrence of serrated yielding, which is called Portevin-Le Chatelier (PLC) effect. The conclusions for the cold stretching in pressure vessel provide theoretic basis reference for engineering applications.
Field Calibration and Accuracy of Torque Wrenches
Authors: Brown Warren , Hamilton Scott , Nguyen An , Smith Tom
Published: May 2012

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. It is common sense that calibration of wrenches on a periodic basis would be advisable. This activity is regulated and required in some industries, such as automotive and wind-power generation. However, in the Petrochemical and Oil & Gas industries there are relatively few companies that practice regular calibration. In part, this may be because there is not data available to justify the cost of such a calibration program. It is not until the calibration program is underway that the value can truly be determined. In this paper, the results of field calibration of several hundred torque wrenches is presented and an analysis of the data reveals exactly why calibration of torque wrenches should be an important part of any leak-free bolted joint program.
A Reliability Based Contour Fatigue Design Approach for Nuclear Piping
Authors: Sakai Shinsuke , Takanashi Masahiro , Maeda Junki , Izumi Satoshi
Published: May 2012

One solution to improve over margin design for piping is to apply reliability based approach. By applying limit state function method in design stage, safety margin can be expressed explicitly as reliability index. From practical point of view, however, it is rather complicated for designer to perform reliability approach every time at design stage. Thus, this paper proposes a reliability based contour design curves which are derived from the uncertainty both for Markl’s best fit curve and for loads. Using this method, reliability based fatigue design can be done easily for the given reliability target. This paper shows the derivation of reliability based contour design curve together with some calculation results and finally proposes the simplified procedure.
Dynamic Analysis of Detonation Chamber and Assessment Based on ASME Code Section VIII, Division 3 and Code Case 2564
Authors: Shirakura Takao , Asahina Joseph K. , Hayashi Koichi , Ouchi Masahiko
Published: May 2012

The most simple and effective method for destroying chemical weapons, and thus eliminating stockpiling problems, is to detonate the entire payload in a chamber without separating the chemical agent from the explosives. A double walled chamber was developed by Kobe Steel, Ltd. (KSL) and has destroyed more than 7000 chemical weapons throughout the world since 2000. Explosion analysis (by AUTODYN) and dynamic structural analysis (by LS-DYNA) performed during development of the chamber design are presented with the experimental results. Design of the latest version of the double walled chamber was evaluated in accordance with the ASME Code Section VIII, Division 3 and Code Case 2564 based on the results of dynamic analysis and measured strains.
Experimental Investigation on the Limit Load Estimation Method for Pipes Containing a Circumferential Surface Flaw With Complicated Shape
Authors: Li Yinsheng , Hasegawa Kunio , Miura Naoki , Hoshino Katsuaki
Published: May 2012

When a flaw is detected in the stainless steel pipes at nuclear power plants during in-service inspections, the limit load estimation method provided in the codes such as JSME Rules on Fitness-for-Service for Nuclear Power Plants or ASME Boiler and Pressure Vessel Code Section XI can be applied to evaluate the integrity of the flawed pipe. However, in these current codes, the limit load estimation method is only derived for pipes containing a flaw with uniform depth, although many flaws with complicated shapes, such as stress corrosion cracks, have actually been detected in pipes. In order to evaluate the integrity of the flawed pipes in a more rational way, a limit load estimation method has been proposed by authors considering the complicated circumferential surface flaw in its shape. In this study, failure bending experiments are performed for stainless steel pipes containing a circumferential surface flaw with a complicated asymmetrical shape. The proposed method is verified by comparing with experimental results of failure bending moments obtained in this study and in previous experiments. It is observed that the predicted failure bending moments by the proposed method are consistent with the experimental results, and the proposed method is applicable to estimate the realistic load-carrying capacity of flawed pipes.