bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Evaluation of Environmentally Assisted Fatigue (EAF) in Consideration of Recent Updates of the Formulas and Hold Time Effects
Authors: Reese Sven H. , Seichter Johannes , Klucke Dietmar , Karabaki H. Ertugrul 
Published: November 2015

Environmentally Assisted Fatigue (EAF) has been focus of various research activities and has been addressed in nuclear Codes and Standards like German safety standard KTA 3201.2 [1], 3211.2 [2] or ASME CC N-792 [3] for example.
Based on experimental investigation under laboratory conditions a numerical correction factor Fen was proposed in NUREG CR-6909 [4] in 2007 after precursors in the Japanese JSME code [6]. In 2012 the EPRI Technical Report “Guidelines for Addressing Environmental Effects in Fatigue Usage Calculations” [7] introduced some practical guidelines for the application of the EAF to real plant components based on the set of formulas from 2007. Since this report the set of formulas have been adapted several times (e.g. in ANL-LWRS 47-2011 [8]) while the current revision of NUREG/CR-6909 in 2014 [9] describes the current state of the art.
At E.ON Kernkraft GmbH a goal-oriented and engineering based research program called NuMEA (Numerical Methods to take Environmentally Assisted Fatigue into Account) has been established, focusing on recommendations of the EPRI guideline in the context of application to real plant components and available temperature measurement data.
First main focus of the R&D activity is to calculate the EPRI sample for verifying developed procedures and taking different procedures for determining the sign to be assigned to the relevant stress intensity into account. The documentation of the procedures applied within the EPRI guideline is not comprehensive enough for real-plant evaluation application. Thus, additional definitions and procedures have been developed to ensure practical application of the procedures being developed. Additionally, updated formulas being recently introduced in the context of the NUREG/CR-6909 Rev. 1 [9] have been implemented.
Second topic of the activities is to develop a procedure to take hold-time effects into account numerically based on existing experimental data. Motivated by the fact that the introduction of a potentially beneficial effect of hold times is foreseen in the framework of piping design of the German KTA safety standards, the existing engineering approach (PVP2014-2819 [10]) is appended to fatigue calculation of NPP components.
This paper presents the results and the highlights of the E.ON R&D project NuMEA.
Effect of Surface Condition on the Fatigue Life of Austenitic Stainless Steels in High Temperature Water Environments
Authors: Platts Norman , Tice David , Stairmand John , Mottershead Kevin , Zhang Wenzhong , Meldrum James , McLennan Alec 
Published: November 2015

High temperature water environments typical of LWR operation are known to significantly reduce the fatigue life of Type 300 series austenitic stainless steels in laboratory studies relative to air environments. This environmental impact on fatigue life has led to the issue of US-NRC Regulatory Guide 1.207 and supporting document NUREG/CR-6909 which predicts significant environmental reduction in fatigue life (characterised by an environmental factor Fen) for a range of actual and design basis transients. However, application of this factor to design curves (obtained from laboratory air data by the application of factors for size, surface finish, environment etc) may be unduly conservative. For example there are reasons to expect that a given surface condition will not have the same impact in air compared to water environments.
The aim of the current work was to determine the impact of different surface conditions, typical of operating plant, on the fatigue life in both air and high temperature (300°C) water environments. This work indicates that, in a simulated PWR high temperature water environment, the impact of either a roughly ground/abraded surface finish (simulating flapper wheel dressing) or a simulated surface scratch on fatigue life relative to a polished surface finish is approximately half of the effect observed in ambient temperature air. This suggests that the application of a Fen value calculated in accordance with NUREG/CR-6909 to the design curves may indeed unduly over-estimate the impact of surface finish on fatigue life.
Presentation of the 2015 Revisions to the RCC-M Code
Authors: Malouines Philippe 
Published: November 2015

The paper describes the general approach followed by AFCEN, the French Society for Codified Rules for Design, Construction and In-Service Inspection of Nuclear Island Components, from the technical and organizational points of view. The RCC-M code, reissued in 2012 and modified with addenda in 2013 2014, and 2015 is presented. The main new topics of activity of the RCC-M Subcommittee are considered: conformity with regulation(s), use of International Standards, equivalence with other codes and harmonization, and latest publication for the quality management system.
The paper highlights how industrial experience is currently being integrated into the RCC-M code, and how the code is evolving to take into account the enlargement of the AFCEN Membership, new AFCEN organization rules, and the international environment, and best practices. The processes for dealing with requests for modifications and interpretations are described.
ASME Sec VIII Div 3 Fatigue Life Predictions Using Critical Plane Approach
Authors: Karpanan Kumarswamy , Thomas William 
Published: November 2015

ASME VIII Div 3 fatigue evaluation is based on the theory that cracks tend to nucleate along the slip lines oriented in the maximum shear stress planes. This code provides methods to calculate the fatigue stresses when the principal stress direction does not change (proportional loading) and axes change (nonproportional loading). When principal stress direction does not change within a fatigue cycle, shear stress amplitude is calculated only on the three maximum shear stress planes. But when the principal stress directions do change within a loading cycle, the plane carrying the maximum shear stress amplitude (also known as critical plane) cannot be easily identified and all planes at a point needs to be searched for the maximum shear stress amplitude.
This paper describes the development of an ANSYS-APDL macro to predict the critical plane at each surface node of an FE model using the FEA stress results. This macro searches through 325 planes (at 10° increments along two angles) at each surface node and for each load step to identify the maximum shear stress and the corresponding normal stress for each surface node. The fatigue life is calculated for each surface node and is plotted as a color contour on the FEA model. This macro can be extended to calculate the fatigue life using other critical plane approaches such as the Findley and Brown-Miller models.
The Effect of Nozzles and Nozzle Loadings on Shell Buckling
Authors: Clarke Edward , Frith Robert 
Published: November 2015

This paper investigates the effect of nozzles and nozzle loadings on the overall buckling capacity of a vessel subject to external pressure designed to ASME VIII Div 1.
ASME VIII Div 1 provides a well-established design-by-rule (DBR) approach for vessels subject to external pressure, but this takes no consideration for the presence of openings or nozzles. There are empirical rules regarding nozzle reinforcement for external pressure, but these do not directly consider the buckling capacity of the overall vessel.
This paper therefore assesses the impact of nozzles on the buckling capacity of a cylindrical shell, where the nozzle is reinforced as per code requirements. The effect of reduced reinforcement is also analyzed.
Subsequently the effect of nozzle loads is also assessed. Nozzles are loaded with ‘allowable’ loads, determined using finite element analysis in accordance with industry practice and code principles.
The buckling capacities are assessed using ASME VIII Div 2 Part 5 methods, using a parametric study with over 500 models. Variables considered are vessel diameter, vessel length, nozzle diameter, and both integral and pad-reinforced nozzles are used.
Research on Hold Time Effects in Fatigue of Stainless Steel: Simulation of Normal Operation Between Fatigue Transients
Authors: Solin Jussi , Reese Sven , Karabaki H. Ertugrul , Mayinger Wolfgang 
Published: November 2015

In PVP2011-57942 we reported improved endurance in fatigue tests with intermediate annealing to roughly simulate steady state operation between fatigue transients in NPP components. Quantification of this effect is in focus of our continued research on fatigue performance of niobium stabilized stainless steel (1.4550, X6CrNiNb1810mod). Similar effect is expected in nuclear power plants during normal operation — e.g. in a PWR surge line or in pressurizer spray lines.
Holds affect cyclic stress strain response. Stress amplitude, tensile mean stress and apparent elastic modulus are increased immediately after a hold, while decreased by cycles in between. Axial shortening is measured during hot holds at zero stress. This all suggest cyclic accumulation of lattice defects and recovery during holds. Recovery may occur through thermally activated dislocation migration together with diffusion, grouping and annihilation of lattice defects. More than one thermally activated processes control the rates of contraction during hold periods at elevated temperatures. Hold hardening delays crack formation by preventing plastic strain localization, in components also on macroscopic level.
A mechanism informed model is sought for transferring laboratory data to real plant components in terms of improving accuracy of numerical fatigue usage assessment. Anticipated mechanisms behind gradual changes in material responses are discussed in relation to quantitative effects of holds.
Correlation Between Transition Temperature Shifts of Impact Tests Using Standard and Subsize Specimens
Authors: Brumovsky Milan , Kytka Milos 
Published: November 2015

Special weld of 15Kh2MFA (Cr-Mo-V) type steel was investigated in several laboratories within the IAEA Coordinated round robin exercise. Specimens were irradiated by several fluences and impact tests of standard Charpy size and 5×5 and 3×4 mm specimens were then tested to determine appropriate transition temperatures and their shifts.
When applied normally used criteria (impact energy, lateral expansion, ductile fracture appearance), shifts in standard specimens and subsize specimens correlate well but not in 1:1 ratio — shifts in subsize specimens were observed to be smaller than in standard ones — the smaller size of specimens, the smaller transition temperature shifts have been obtained.
The paper tries to find appropriate criteria for better correlation between shifts in different sizes of impact specimens that can be supported by proper analysis.
Overview of NIST Activities on Sub-Size and Miniaturized Charpy Specimens: Correlations With Full-Size Specimens and Verification Specimens for Small-Scale Pendulum Machines
Authors: Lucon Enrico , McCowan Chris N. , Santoyo Raymond L. 
Published: November 2015

NIST in Boulder Colorado investigated the correlations between impact test results obtained from standard, full-size Charpy specimens (CVN) and specimens with reduced thickness (sub-size Charpy specimens, SCVN) or reduced or scaled cross-section dimensions (miniaturized Charpy specimens, MCVN). A database of instrumented impact test results was generated from four line pipe steels, two quenched and tempered alloy steels, and an 18 Ni maraging steel. Correlations between specimen types were established and compared with previously published relationships, considering absorbed energy, ductile-to-brittle transition temperature, and upper shelf energy. Acceptable correlations were found for the different parameters, even though the uncertainty of predictions appears exacerbated by the expected significant experimental scatter.
Furthermore, we report on the development of MCVN specimens for the indirect verification of small-scale pendulum machines (with potential energies between 15 J and 50 J), which cannot be verified with full-size verification specimens. Small-scale pendulum machines can now be verified at room temperature with certified reference specimens of KLST type (3 mm × 4 mm × 27 mm), supplied by NIST at three certified absorbed energy levels (low energy, 1.59 J; high-energy, 5.64 J; super-high energy, 10.05 J). These specimens can also be used to verify the performance of instrumented Charpy strikers through certified maximum force values. Certified reference values for both absorbed energy and maximum force were established by means of an interlaboratory comparison (Round-Robin), which involved nine qualified and experienced international laboratories.
Effect of Material Properties of Gasket on the Sealing Performance of Pipe Flange Connections at Elevated Temperature
Authors: Sawa Toshiyuki , Takagi Yoshio , Torii Hiroyasu 
Published: November 2015

The sealing performance of the pipe flange connection depends on the compressive gasket stress. Therefore, the unexpected leakage can be avoided by estimating the change in compressive gasket stress during operation. In order to make such estimation, the material properties of the gasket are required as well as those of bolt and flange material. When the pipe flange connection is used under heated condition, the thermal expansion coefficient shows an important role. For example, if the thermal expansion coefficient of gasket is larger than that of pipe flange material, the gasket stress is expected to be increased by increasing the temperature and the sealing performance of pipe flange connection is improved. However, a gasket tends to be softening at high temperature. Beside, the creep phenomenon of gasket induces the decrease of gasket stress. Thus, the behavior of the gasket is complicated and it should be investigated to make a reliable design.
In this paper, the high temperature properties, including thermal expansion and stress relaxation property of spiral wound gasket with expanded graphite are examined by compression tests at elevated temperature. The stress analysis with high temperature material properties obtained from the compression tests also conducted to estimate the sealing performance of pipe flange connection. As a result, the pipe flange connection with spiral wound gasket is expected to keep the superior sealing performance at 300 C for long time.
Fracture Properties in Dissimilar Metal Weld Junctions: Experimental Methodology of Characterization
Authors: Bourgeois M. , Perez G. , Chapuliot S. 
Published: November 2015

Within the framework of European project MULTIMETAL (Structural performance of multi-metal component), several fracture tests on different types of multi-material specimens have been performed. Present fracture toughness standard methods, e.g. ASTM E 1820 are not directly intended for Dissimilar Metal Welds (DMWs). Therefore further investigations are needed in order to define the best practice in fracture mechanical tests and their analysis for DMWs.
Specimens were taken from welded plates: a narrow gap Inconel DMW junction between ferritic and austenitic stainless steels, designed and delivered by AREVA France. The work is focused on the nickel alloy - ferritic steel interface which is the weakest area of such welded pipes regarding ductile tearing. This paper is focusing on the experimental methodology in this particular case of multi-material fracture test specimens.
The first difficulty consists in machining specimens with a location of crack plane at the interface or close to the interface. Physically, the interface between the nickel alloy weld and the ferritic steel is not a straight plane. Some normalized specimen - geometries like CT (Compact Tension specimen), SE(B) (Single Edge Bend specimen), or SE(T) (Single Edge Traction specimen) - have been machined in the DMW junction. Some recommendations are discussed about this first step of work.
The second difficulty is the procedure of fracture test itself. The present fracture toughness standard method uses the method of compliance for the determination of J-Δa curves. The plasticity, in ferritic and stainless steel parts of specimens, has induced unsymmetrical response. Locally the path of the crack has been influenced by the gradient of properties of the multi-material medium (weld, heat affected zone). The J values, determined at crack initiation, are dependent of the location of crack plane. Results between specimens are compared and discussed.
Based on the current standard, this article highlights some shortcomings of this standard when used in heterogeneous specimens. The well-known problem of transferability is also pointed out (different values of J for crack initiation depending of the geometry and size of specimen).
In conclusion further numerical works are needed to assess experimental results and provide intrinsic material data, in terms of fracture properties of the Nickel alloy-ferritic steel interface.
Use of Elastic Follow-Up to Study the Effect of Displacement Controlled Loading on Plastic Collapse Pressures for Circumferentially Cracked Pipes
Authors: Wu Guiyi , Smith David J. , Pavier Martyn J. 
Published: November 2015

Structural integrity assessments of pressurised pipes consider plastic collapse as a potential failure mode. This paper uses finite element analysis to explore the effect of the pipe end boundary conditions on the collapse pressure. Two end conditions are considered: a fixed axial load and a fixed axial displacement. The fixed axial displacement condition represents a long-range axial residual stress. In the R6 structural integrity assessment procedure long-range residual stress is associated with elastic follow-up. However, no guidance is given on whether the level of elastic follow-up is sufficient to justify treating long-range residual stress as a primary stress.
In this paper, a method is proposed to estimate elastic follow-up of an internally pressurised pipe containing a fully circumferential crack. It is found that the elastic follow-up is related to the length of the pipe. A short pipe that contains a fully circumferential crack, subjected to a displacement induced axial stress, has a global collapse that is not modified by the fixed displacement condition. The short pipe corresponds to a small elastic follow-up factor, Z. However, as the elastic follow-up factor increases, the presence of long-range residual stress starts to make a contribution to global collapse. When elastic follow-up is significant, a long-range residual stress has the same effect on global collapse as does a mechanical stress.
Stresses on Aluminum Brazed Plate Fin Heat Exchangers in a Floating Environment
Authors: Hölzl Reinhold , Lehmacher Axel 
Published: November 2015

The present paper describes a study for the application of Aluminum Brazed Plate Fin Heat Exchangers (PFHE) in a floating environment. Due to the continuous movements of the ship hull a main focus is given to fatigue considerations because it is well known that aluminum does not have a distinct endurance limit. Therefore it is mandatory to base a fatigue evaluation on a design code as for example the German AD2000 Merkblatt S2 [16] which allows fatigue evaluation of aluminum. There an endurance limit of 5 million cycles is defined. On that basis two plate fin heat exchangers were analyzed focusing on accelerations due to ship motion and thermal fatigue as a secondary consequence of ship movements (liquid sloshing, unsteady flows).
For the acceleration due to ship motions a value out of a concept study was taken. This value of 2.5 m/s2 was used for acceleration in three directions for both exchangers. All calculated stresses were below the endurance limit and therefore no measures have to be taken.
Thermal fatigue as secondary effect of the ship movements was analyzed as a worst case investigation for a block in shell exchanger. The resulting fatigue loads seem not to be a concern in this specific case but it is strongly recommended to carefully check any design for similar or different applications. Furthermore it is recommended generally to carefully ensure stable process conditions.
Summing up all these points the application of PFHE in a floating environment has to be investigated very carefully but seems to be possible.
Fatigue Monitoring in the Context of Long-Term Operation of the Goesgen Nuclear Power Plant Using AREVA’s FAMOSi
Authors: Wermelinger Thomas , Bruckmüller Florian , Heinz Benedikt 
Published: November 2015

In the context of long-term operation or lifetime extension most regulatory bodies demand from utilities and operators of nuclear power plants to monitor and evaluate the fatigue of system, structures and components systematically. As does the Swiss Federal Nuclear Safety Inspectorate ENSI. The nuclear power plant Goesgen started its commercial operation in 1979 and will go into long-term operation in 2019. The increased demand for monitoring and evaluating fatigue due to the pending long-term operation led the Goesgen nuclear power plant to expand the scope of their surveillance and therefore to install AREVA’s fatigue monitoring system FAMOSi in the 2014 outage. The system consists of 39 measurement sections positioned at the primary circuit and the feed-water nozzles of the steam generators. The locations were chosen due to their sensitivity for fatigue. The installed FAMOSi system consists of a total of 173 thermocouples which were mounted in order to get the necessary input data for load evaluation. The advantage of FAMOSi is the possibility to obtain real data of transients near places with highest fatigue usage factors. Examples of steam generator feed-in during heating-up and cooling-down will be given. In addition, spray events before and after the installation of closed loop controlled spray valves will be compared.
The measurements and the results of the load evaluation are not only of interest for internal use e.g. in regard to optimization of operation modes (e.g. load-following), but must also be reported to ENSI annually. In addition, by evaluation of stresses and determination of usage factors combined with an optimization of operation modes an early exchange of components can be avoided.