bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow-Induced Transverse Vibration of a Cantilevered Prism and Vibration-Generated Power Using Magnetostrictive Material
Authors: Kiwata Takahiro , Yamaguchi Makoto , Kono Takaaki , Ueno Toshiyuki
Published: January 2014

Free-vibration tests of a cantilevered rectangular prism with a side ratio of less than D/H = 0.5 (D, depth of the rectangular prism in the flow direction; H, height of a rectangular prism) that experiences low-speed galloping at a lower reduced velocity than the resonant reduced velocity were conducted in a water tunnel. We also carried out a power generation experiment using an iron-gallium alloy, which is a magnetostrictive material, to investigate the possibility of harvesting energy from a flow-induced transverse vibration. The effects of the side ratio of the rectangular prism and the configuration of a fin that was fitted on the back of a rectangular prism to increase the flexural rigidity on the response amplitude were investigated. The vibration of a rectangular prism with D/H = 0.1 occurred at a lower reduced velocity than that of the other rectangular prisms. This prism has the largest increment rate of the non-dimensional response amplitude ηrms for reduced velocity Vr, and the vibration has an uniform amplitude for each reduced velocity. The reduced velocity at the 20% non-dimensional response amplitude of a rectangular prism Vr0.2 decreases linearly with decreasing side ratio D/H. The response amplitude of the rectangular prism with D/H = 0.2 is only slightly dampened for all values of the reduced mass-damping parameter Cn.

The values of Vr0.2 of the rectangular prism with a fin increased as the depth ratio of the fin increased. The response amplitude of the rectangular prism with/without a fin was found to be related to the second moment of area of the prism. The energy harvester using magnetostrictive material and a rectangular prism with D/H = 0.2 generates a maximum electric power of 8.8 mW.
Effect of Make-Up on the Structural Performance of Standard Buttress Connections Subjected to Tensile Loading
Authors: Galle Timothy , De Waele Wim , De Baets Patrick
Published: January 2014

When establishing oil wells, pipe sections are connected by means of threaded couplings. In an effort to minimize the possibility of failure by jumpout, standard buttress connections were introduced. Part of their strength is directly acquired as a result of radial interference during make-up.

This paper discusses the results of a numerical study evaluating the effect of make-up on the performance of a standard 4.5 inch API buttress connection when axial tensile force is applied. In order to characterize the structural performance, the load distribution along the coupling length is evaluated, combined with a parameter defining thread separation. The latter is indicative for jumpout and the tendency of creating a leak path throughout the thread helix.

From the results it is clear that relative axial displacement within the coupling occurs, even when made up, because of an initial clearance among the load and stab flanks. This clearance may cause a connection to leak through the thread helix when available thread compound cannot heal this leak path. Despite undesirable effects on the sealability and rigidness of this joint, such a clearance is required to decrease frictional forces during make-up while maintaining the desired radial interference.
A CFX Simulation of the OECD/NEA T-Junction Benchmark
Authors: Gillis Jay C. , Belley Benoit P. , Romero Martin
Published: January 2014

In response to a solicitation for Computational Fluid Dynamic (CFD) simulations of flow in a T-junction from the Nuclear Energy Agency of the Organization for Economic Co-operation and Development (OECD/NEA) [1], Structural Integrity (SI) Associates of San Jose, CA, USA has completed a simulation using the commercially available CFD code ANSYS-CFX. The simulation was carried out for geometry and flow conditions matching an experiment underway at Vattenfall Research and Development in Sweden where two streams of differing temperature mix in a T-junction. The benchmark was to be a blind test of CFD simulations. Experimental results were not released until after benchmark participants submitted the results of their simulation to the OECD/NEA.

The CFD simulation done by SI was carried out on an all hexahedral mesh of 1,881,504 elements generated using the ANSYS Mechanical Finite Element program. The mesh was then transferred into the CFX program and, after applying proper boundary conditions, a time-dependent simulation was done using the Large Scale Eddy Simulation (LES) turbulence model [2] with Wall Adjusting Local Eddy Viscosity (WALE) sub-grid scale (SGS) turbulence model [2, 3].

Comparisons of the CFD results to the Vattenfall data show close correspondence for mean and root-mean-square (rms) turbulent temperature fluctuations.
Fitness-For-Service Assessment of Pressure Equipments With Local Metal Loss Subjected to Seismic Loading
Authors: Yamamoto Takashi , Kaida Takuyo , Nagata Satoshi , Tsuji Hirokazu
Published: January 2014

The concerns about Fitness-For-Service (FFS) assessment technique for pressure equipments with local metal loss have been growing from some characteristic damages, for example, many examples of the corrosion under insulation (CUI) of pressure equipment, have been reported from petroleum and petrochemical industries. FFS assessment procedure for the pressure equipments for metal loss has been validated by the results of various burst tests and FEM simulations for internal pressure loads.

There has, however, been little study to validate FFS assessment for pressure equipments subjected to seismic load. This paper suggests an FFS assessment procedure for pressure equipments with local metal loss subjected to both internal pressure and seismic loading. To ensure consistency to High Pressure Gas Law in Japan, allowable stress is based on the Japanese seismic design code. Developed stress on local metal loss from both internal pressure and seismic load is evaluated in accordance with API 579/ASME FFS-1.

The authors have verified safety margin and reliability of this method to toward to practical application. In order to verify, some cyclic bending load testings and finite element analysis were implemented under the conditions of ambient temperature and 300 degree C. The results of these validations show that the safety margins against low cycle fatigue are the range of 2.6 to 4.6. In addition, the test results at 300 degree C showed higher safety margin than that in ambient temperature.
Crack Propagation due to Movement or Size Change of Hot Spot in Pipe
Authors: Wirgart Jonas Erik , Terai Takayuki , Kasahara Naoto
Published: January 2014

Thermal fatigue may occur downstream from mixing tee junctions where hot and cold water are turbulently mixed. Depending on the momentum of the incoming flows, different characteristic eddies are formed which create a local hot spot on the inner surface of the pipe. The hot spot have an unstable discrete boundary that spatially oscillates and this creates an oscillating multidimensional thermal load that induces high cycle thermal fatigue.

To predict the thermal fatigue lifetime of a pipe subject to this kind of thermal load, transient FEM simulations with an ideal hot spot in two and three dimensions were conducted. The crack lengths induced by the frequency of the oscillating boundary was analysed and it was found that the most harmful frequency for a pipe is in the nondimensional frequency of 0.01 to 1.0. Additionally, the simulation method was validated against data publications of FAT3D experiments.

The simulations have been compared to the current proposed Japanese design code for mixing tee junctions. The study shows that this multidimensional effect induces larger crack lengths than the current design code. The reason of this was analysed.
Fatigue Analysis of Free Span for Submarine Pipeline
Authors: Dong Jie , Chen Xuedong , Wang Bing , Guan Weihe , Yang Tiecheng , Fan Zhichao , Pan Jianhua
Published: January 2014

The offshore oil and gas are mainly gathered and transported by submarine pipeline due to its merits of continuity, convenience and less effect of climate. Free span often occurs because of the unevenness and scour of seabed and endangers the safe running of pipeline. Fatigue is one main failure mode for free span. In this paper, combined with the actual service status of submarine pipeline, considering the variation of velocity with time, the load of wave and current, the effect of cross-flow vibration to the in-line vibration, the fatigue failure of the detected free span is analysed primarily and detailedly by correlated standard, and the results are given.
Detection of Wall-Thinning Defects in Nuclear Piping Components Using an Advanced Infrared Thermography Technique
Authors: Kim Jin Weon , Yun Kyung Won , Jung Hyun Chul
Published: January 2014

An advanced infrared thermography (IRT) technique, known as lock-in mode IRT, has been developed and employed to improve the detection capability of defects in materials with high thermal conductivity. Lock-in mode IRT has been shown to provide better detection capability than conventional active IRT. Therefore, to investigate application of this technique to nuclear piping components, we conducted lock-in mode IRT tests on pipe specimens containing simulated wall-thinning defects. We obtained phase images of the wall-thinning defects and compared them with thermal images obtained from conventional active IRT tests. The results indicated that the ability to size the detected wall-thinning defects in piping components was improved by using lock-in mode IRT. The improvement was especially apparent when detecting short and narrow defects, and defects with slanted edges. However, the detection capability for shallow wall-thinning defects did not improve much when using lock-in mode IRT.
Shakedown Boundary and Limit Load Determination of a 90-Degree Back to Back Pipe Bend Subjected to Steady Internal Perssures and Cyclic In-Plane Bending Moments
Authors: Abdalla Hany F.
Published: January 2014

Shakedown analysis of 90–degree back–to–back pipe bends is scarce within open literature. According the author’s knowledge, no shakedown analysis exists for such structure based on experimental data. Ninety degree back–to–back pipe bends are extensively utilized within piping networks of nuclear submarines and modern turbofan aero–engines where space limitation is considered a paramount concern. Additionally, on larger scales, 90–degree back–to–back pipe bend configurations are also found within piping networks of huge liquefied natural gas tankers. The structure analyzed is formed by bending a straight pipe to acquire the geometry of two 90–degree pipe bends set back–to–back each having a nominal pipe size (NPS) of 10 in. Schedule 40 Standard (STD). In the current research, the 90–degree back–to–back pipe bend setup analyzed is subjected to a spectrum of steady internal pressures and cyclic in–plane bending moments. A previously developed simplified technique for determining elastic shakedown limit loads is utilized to generate the elastic shakedown boundary of the 90–degree back–to–back pipe bend analyzed. In addition to determining the elastic shakedown boundary, elastic and post shakedown domains (Bree diagram), the maximum moment carrying capacities (limit moments) are also determined and imposed on the generated Bree diagram of the analyzed structure. The simplified technique outcomes showed excellent correlation with the results of full elastic–plastic cyclic loading finite element simulations.
Towards a Smoothed Particle Hydrodynamics Algorithm for Shocks Through Layered Materials
Authors: Zisis Iason , van der Linden Bas , Giannopapa Christina
Published: January 2014

Hypervelocity impacts (HVIs) are collisions at velocities greater than the target object’s speed of sound. Such impacts produce pressure waves that generate sharp and sudden changes in the density of the materials. These are propagated as shock waves. Previous computational research has given insight into this shock loading for the case of homogeneous materials. Shock-wave propagation through materials with discontinuous density distribution has not been considered in depth yet.

Smoothed Particle Hydrodynamics (SPH) is a numerical technique, which has been extensively used for the simulation of HVIs. It is especially suitable for this purpose as it describes both the solid and fluid-like behavior effectively as well as the violent breakup of the material under impact. In previous studies on SPH, impact loading of composite materials was modeled by homogenization of the material, or under assumption of being a so-called functionally graded material (FGM). Both these models neglect the reflection-transmission effects on the interface between materials of different density.

In this paper the shock loading of layered materials is studied. A modification to the standard SPH method is developed and tested, that incorporates materials with purely discontinuous density distribution. The developed method’s performance at simple shock loading cases is investigated; reflection-transmission patterns of shock-waves through layered materials are discussed, along with a parametric study of the governing parameters.
Low Speed Instability of Two-Dimensional Rectangular Prisms
Authors: Matsuda Kazutoshi , Kato Kusuo , Hisadomi Keigo , Harada Kentaro
Published: January 2014

A wind tunnel study was carried out to examine the low speed instability of rectangular cross sections, which could occur at a lower wind speed range than that of Karman vortex-induced oscillation, if the Scruton number Sc = 2mδ/(ρD2), in which m = the mass of the system per length; δ = the system damping measured in still air; ρ = air density; D = is a reference length, is very small. The low speed instability was found by the full-scale measurements at bracing members having a rectangular cross section of the long-spanned truss bridge in Japan. The Scruton number of the bracing members was estimated to be approximately 2–3, therefore the low speed instability was thought to occur. However, the occurrence depended on the wind conditions. Unfortunately there are few past researches on the low speed instability on a rectangular cross section of B/D of less than 2, which is the ratio of the width B and height D. In this study, the free oscillation experiment and unsteady aerodynamic lift measurement were conducted in order to clarify the effects of an angle of attack, a yaw angle, cross section shapes and the turbulence intensity on the low speed instability.
Development of New Weld Heat Input and Dilution Equations for Gas Tungsten Arc Welding: Part 1
Authors: Tatman Jonathan K. , McCracken Steven L. , Hicks Trevor G.
Published: January 2014

Predicting weld dilution for machine gas tungsten arc welding (GTAW) is a challenge due to the number of variables associated with the welding process. Proper heat input and power ratio controls are critical in many welding applications to control weld dilution, such as for dissimilar metal welds where low weld dilution is necessary to prevent solidification cracking or for cladding where weld dilution is minimized to maintain corrosion resistance of the clad material. This paper discusses the preliminary development and validation of improved weld dilution, heat input, and power ratio equations for the GTAW process. The new equations incorporate power added for the hot wire GTAW process, filler metal material properties, and the heat used to melt the filler metal when added to the GTAW process. The weld dilution equation was validated by comparing calculated dilution values to measured values from bead-on-plate weld trials performed on a variety of filler metals and substrates. Results of the testing and validation along with limitations of the new equations are discussed.
Assessment of Weld Overlay Defects in a Hydrocracking Unit Reactor
Authors: Robai Mohammed S. , Al-Sudairy Jarallah A. , Al-Harbi Abdullah M. , Joseph Joy
Published: January 2014

Asset Performance Management is a key element of operational excellence. It refers to the management systems, strategies and activities aimed at maintaining the integrity of plant assets for their desired life. The safe operation of the assets is to be ensured at any cost. The objective of this paper is to offer one of the most critical assets in a refinery, namely the Hydrocracking Unit (HCU) reactor, as a case study addressing assessment of defects found in the weld overlay.

The reactor was built in 1978 according to ASME Sec. VIII Div. 2 and has been in operation since then. The reactor is constructed of Chromium-Molybdenum (Cr-Mo) base material (SA 336 F21) with thickness of 266 mm and corrosion resistant stainless steel (TP-347 with thickness of 3.2 mm) weld overlay. The very high operating temperature and pressure of the reactor in hydrogen rich hydrocarbon service and the resulting thermal stress and material degradation caused disbonding and cracks in the stainless steel weld overlay. This paper will address the approach that was used to alleviate such type of defects. Also, various considerations that go into the assessment are discussed and recommendations are suggested.
Application of Improved Kent’s Pipeline Risk Scoring Method Based on Fuzzy Mathematics in the Risk Assessment of Embedded Petroleum Pipeline
Authors: Ye Cheng , Zhi Youran , Fang Xuefeng , Jiang Ping
Published: January 2014

Numerous risk factors exit in the petroleum transmission process of embedded pipelines. Using scientific risk assessment technology to distinguish various hidden perils of pipeline accidents and the corresponding impacts is of significant value in the risk controlling of embedded petroleum pipelines and thus insure their normal operation. The common used Kent’s scoring method can systematically evaluate the relative risk of pipelines, but it has some shortcomings in reflecting the impact differentiations of various influencing factors on the pipeline risk due to the identical assignment of weights for four categories of factors. In this work, we first systematically make risk identification for the embedded petroleum pipelines and further propose a kind of improved Kent’s scoring method, i.e. the Multilevel Fuzzy Comprehensive Evaluation (MFCE) method based on the fuzzy mathematics theory, in which the fuzzification between various influencing factors are considered. Using the MFCE method, it is able to make semi-quantitative risk assessment, as well as risk classification and grading for the embedded petroleum pipeline network in a specific urban area. Finally, with the assistance of the Geographic Information System (GIS) platform, the risk evaluation results of the embedded pipelines with the MFCE method can provide scientific aid decision making basis for the early warning of risk and the emergency plan compilation for the pipeline accidents.
Improved Reliability of Small Punch Testing by Correction of Testing System Stiffness and Measurement of Hydrogen Sensitivity
Authors: Lee Hae Moo , Park Jong Seo , Chung In Hyun , Baek Un Bong , Nahm Seung Hoon
Published: January 2014

Conventionally embrittlement of components for petrochemical equipment has been determined by small punch (SP) testing, which involves carrying out mechanical testing of specimens sampled from practical structures to estimate the integrity and residual life of the equipment. The application range of SP testing has been expanded to cryogenic environments, and attempts have recently been made to expand it further to high-pressure hydrogen environments. To examine the effect of hydrogen on pipeline materials before SP testing, the amount of hydrogen permeation was measured under several testing conditions. The test specimens were prepared as follow. First, after obtaining a section (10 mm in width, 10 mm in height, and 0.7 mm in thickness) from a steel pipe made of X70, X65, or X42 as the base metal by wire cut electric discharge processing. Subsequently, grinding both surfaces, the test specimen was finished to maximum surface roughness of less than 6 μm, with a final thickness of 0.5 ± 0.005 mm. The aim of this study was to determine whether sensitivity to hydrogen could be measured by SP testing; hence, the test was conducted at a punch speed of 4 × 10−3 mm/min, which is much slower than the 0.2 ∼ 2 mm/min adopted for conventional SP testing, like CWA 15627. The maximum load measured for all three steels under 10 MPa was not influenced by machine type (servo hydrodynamic or electromechanical), holding time after charging hydrogen, or bolt fastening torque. Different means for correcting SP curves depending on the stiffness of the testing machines were suggested, and their effectiveness throughout testing was demonstrated.
Study of a Fluid-Structure Interaction Instability Mechanism in a Tube Bundle With Multiphase-POD Approach
Authors: Pomarède Marie , Liberge Erwan , Sigrist Jean-François , Hamdouni Aziz , Longatte Elisabeth
Published: January 2014

Multiphase-Proper Orthogonal Decomposition Reduced-Order Method has been proven to be efficient for the low-cost study of fluid-structure interaction mechanisms. Applications to a single tube under cross-flow, then to a tube bundle system revealed good behaviours of this method, which was shown to be able to accurately reproduce the velocity flow field as well as the solid displacement, even in the case of large magnitudes. The goal here is to go further by studying an instability mechanism with the Multiphase-POD technique, involving a tube array configuration because of its high interest in the nuclear domain. We first want to know if this method can reproduce critical to unstable cases and finally, we are interested in the possibility of leading a parametric study coupled with the Multiphase-POD Method in order to evaluate the instability threshold. Indeed, parametric studies coupled with a reduced-order method could lead to a CPU time additional gain, since only one basis calculation could cover several configurations with low computational cost.
Comparison of Flaw Driving Force Estimates in Simulated Weld Residual Stress Fields
Authors: Dewees David J. , Dodds Robert H.
Published: January 2014

Previous work has focused on the methods and results for calculating flaw driving force in simulated three-dimensional (3D) weld residual stress (WRS) fields using contour (J) integral techniques. This paper extends that work to look at explicit modeling of the crack tip opening displacement (CTOD) in these same WRS fields, and for the same range of semi-elliptical flaws. Comparison is made between the predicted trends of driving force with crack size for the calculated driving force (J-integral) versus the “measured” value (CTOD). Implications for fracture assessments are given, and recommendations for future work are made.
Evolution of Mechanical Behavior of 6XXX Aluminium Alloy due to the Precipitation State During a Thermo-Mechanical Process
Authors: Bardel Didier , Perez Michel , Nelias Daniel , Chaise Thibaut , Garnier Jerôme , Bourlier Florent
Published: January 2014

The aim of this research is to link the microstructural state and the mechanical properties of an age hardening alloy during a fast heat treatment such as encountered during welding.

A coupled model between precipitation state and mechanical properties is used to predict the yield strength and hardening behavior that can be observed experimentally. The method permits the identification of the kinematic and isotropic contributions in the hardening model. The methodology is applied to a 6061-T6 aluminium alloy which is used in the Jules Horowitz reactor vessel.

The general idea of this methodology is to couple an efficient microstructural model to a mechanical one based on the dislocation theory and ad’hoc experiments. The theoretical background is based on the work of Kampmann and Wagner, known as the KWN model, to account for nucleation, growth/dissolution and coarsening of precipitates. This analysis requires transient thermo-mechanical experimental data. The efficiency of these models and their coupling are shown for a serie 6XXX aluminium alloy which contains β″ and β′ precipitates. Ultimately these models are coupled to a FEA model and allows to predict the distribution of precipitates within each element of the mesh, and subsequently its mechanical behavior.
Practical Sealing for Common Gasket Materials and Construction Types
Authors: Bausman Anita R. , Waterland A. Fitzgerald (Jerry)
Published: January 2014

This paper surveys common gasket materials and construction types evaluated against sealing conditions. The end-user often asks the question, “Which type of gasket should I use for this application?” While much attention has been recently focused on temperature/pressure performance, other end-user concerns include whether or not a particular joint is capable of achieving a desired leakage range (e.g., tightness) and how well a gasket may compensate for some non-ideal flange issues. Different gasket materials/constructions are more forgiving than others. Selected gaskets often used in the chemical process industry will be compared for minimum gasket seating stress to achieve various tightness levels, the required “chemical service tightness” gasket stress against the “max out” component stress for a typical joint, and associated gasket compression. This paper compares ASME Class 150 NPS 3” and 4” joints using gaskets of various materials and constructions. Materials include fiber, filled and expanded PTFEs, flexible vermiculite, and flexible graphites. Construction types include sheet-based rings, spiral wounds, groove-profiles, and corrugated metal. Comparing typical stress and compression ranges for the various materials and constructions will help the end-user learn to narrow the selection of available gaskets and achieve a more economical bolted joint design.
Gasket Selection and Assembly Criteria for Internal Sealing Manways and Handholes
Authors: Waterland A. Fitzgerald (Jerry)
Published: January 2014

Internal sealing manways, hand-holes, drum doors, etc. present very unique sealing and assembly challenges. Unlike other conventional gasketed connections, the majority of the gasket compression forces are developed during operation, and not during assembly. This creates several critical issues that must be understood and overcome in the original gasket selection process and the assembly itself. Even if considered and addressed in the original gasket selection and assembly process, these internal sealing manways will likely still require a post start-up retorque. The timing of the re-torque is of critical importance in ensuring worker safety and continued equipment reliability and uptime.
Pipe Girth Weld Residual Stress Intensity Factor Profiles for Structural Integrity Assessment
Authors: Bouchard P. John
Published: January 2014

The influence of the residual stress field in a welded structure on crack growth and fracture is commonly assessed through its contribution to the stress intensity factor (SIF) for the crack of interest. This contribution is most often calculated by assuming a bounding through-thickness residual stress profile for the specific type of weldment with an appropriate SIF solution for the crack location, shape and structure of concern. Although more realistic residual stress profiles for stainless steel pipe girth welds have been developed recently their use, in some cases, leads to an underestimate of the SIF. A new approach is developed for determining bounding SIF values for cracks in residual stress fields of stainless steel pipe girth welds. The forms of the proposed SIF profiles are based on recently published SIF solutions for cracks in periodic residual stress fields [1]. It is shown that the SIF profiles bound those based on a large database of residual stress measurements without being excessively conservative. The outcome is a simple new method for defining more realistic SIF profiles for use in structural integrity assessments of stainless steel pipe girth welds.
Evaluation Procedure of Limit Load for Non-Aligned Multiple Flaws
Authors: Iwamatsu Fuminori , Miyazaki Katsumasa , Takazawa Hidekazu , Saito Koichi
Published: January 2014

The fitness-for-service codes such as the ASME Boiler and Pressure Vessel Code Section XI require the characterization of non-aligned multiple flaws for flaw evaluation, which is performed using a flaw alignment rule. Worldwide, almost all such codes provide their own alignment rule, often with an unclear technical basis regarding the application of the rule to plastic collapse due to ductile fracture as prescribed by limit load analysis based on a net-section approach. Therefore, evaluation procedures to calculate collapse load for non-aligned multiple flaws have been proposed in various experimental and analytical studies. In these proposals, a collapse load for non-aligned multiple flaws is evaluated using the net-section stress approach in consideration of the ratio of a distance between flaws to a flaw length parameter. However, because each study proposes its own appropriate length and distance parameters, which are based on a few experimental results limited to that study, the applicability of the proposed parameters to evaluation of collapse load for arbitrary flaw sizes and locations is unclear.

In this study, we performed fracture test result on a flat plate with two through-wall flaws in order to determine appropriate parameters for the evaluation procedure of the collapse load for non-aligned multiple flaws. Appropriate parameters were determined by correlation coefficients obtained by comparison of maximum loads of fracture tests and collapse loads of evaluation with various parameters. We found that the appropriate parameters to apply the alignment rule with equations to evaluate collapse load for non-aligned flaws were the ratio of the vertical or direct distance between flaws to the maximum or average flaw length.
Methodology for Numerical Welding Simulation Validation: The Dissimilar Metal Weld Case
Authors: Gilles Ph. , Courtin S. , Vincent R. , Yescas M. , Gommez F.
Published: January 2014

Welding processes induce residual stresses and distortion in the welded joint and the connected components. For manufacturing purpose distortion is the main issue and up to now the problem is handled by post weld corrective actions. Welding residual stress fields are not considered at the design stage in French codes and standards. However, it is well known that residual stresses are likely to increase the risks of fatigue or corrosion and may cause failure in brittle materials. Ferritic parts of large components are post-weld heat treated; allowing disregarding the influence of residuals stresses thanks to their relief. Preventive measures, including mitigation by fine polishing are undertaken in corrosion sensitive zones. The influence of residual stresses on fatigue is more complex to analyze: in low cycle fatigue, residual stresses should be relieved or redistributed after few cycles with plastic straining, and for high cycle fatigue, residual stress effects are accounted for through a mean stress offsett.

When considered, residual stress fields are often represented in a very crude manner by a membrane distribution of the most influent stress component through the thickness of the structure. In a less rough way, several codes or fitness-for-purpose guidelines (API [1], British standards [2]) propose residual stress profiles relative to several weld configurations. Nevertheless for a given case, the given profiles may differ significantly for several reasons: the degree of conservatism, the number of covered cases, the embedded margins accounting for uncertainties.

Some ill-posed benchmark problems have shown that numerical simulation of residual stresses may deliver very scattered results. AREVA has therefore developed a methodology to validate welding simulations. The scope is limited to fusion welding. The simulations are based on a Thermo-Metallurgical Mechanical model in which the welding energy is represented by an equivalent heat source.

This paper presents the actual state of development of this methodology which will be illustrated through 4 examples of residual fields in Dissimilar Metal Welds. Residual stress measurements have been performed for each of the four mock-ups by different techniques. Based on this important experimental and numerical campaign some actions of improvement of the validation methodology are finally listed.
Experimental Investigation of the Strain-Strengthen Effect on the Existed I+II Mixed Mode Fatigue Crack Transformation Propagation in an Austenite Stainless Steel
Authors: Li Huifang , Wang Zhenbei , Sun Xiaoju , Qian Caifu
Published: January 2014

In this paper, I+II mixed mode fatigue crack transformation propagation in austenitic stainless steel 06Cr19Ni10 was tested. Finite element method with displacement approach was employed to calculate stress intensity factors at the crack tip. Strain-strengthening effect on the new crack initiation and propagation of the existed pre-crack was investigated. It is found that under the uni-axial loading, the inclined pre-crack grows in a direction perpendicular to the applied load, making crack mode transferred from I+II mixed mode to Mode I. When strain-strengthened, the new crack initiation from the pre-crack tip is much more difficulty and crack propagation is slower. Finite element non-linear analysis shows that a residual compressive stress distribution is formed around pre-crack tip after strain-strengthening. The residual compressive stress is responsible for the difficult initiation and slow propagation of the new crack.
Environmental Fatigue Factors (NUREG/CR-6909) and Strain Controlled Data for Stabilized Austenitic Stainless Steel
Authors: Solin Jussi , Reese Sven , Karabaki H. Ertugrul , Mayinger Wolfgang
Published: January 2014

Experimental research on fatigue performance of niobium stabilized stainless steel (1.4550, X6CrNiNb1810 mod) relevant for German NPP primary piping has previously demonstrated good long life performance.

Slow rate fatigue tests in 325 °C PWR water are first time presented and discussed in this paper. Good fatigue performance was measured also in hot water. Our experiments give consistently about doubled lives or 50% smaller Fen factors in compared to predictions by NUREG 6909.

Transferability of the laboratory data, reference and design curves together with the proposed Fen evaluation procedure to component evaluation will be discussed.
Predictions of Fracture Toughness for Weld Material When Adopting a Novel Particle Failure Criterion and a Measured Experimental Particle Distribution
Authors: James Peter , Ford Mike , Jivkov Andrey P.
Published: January 2014

It is important for safety case justification of the continued use of nuclear power plant that any changes in the ferritic RPV steels’ fracture toughness with temperature, irradiation and geometry can be accounted for, particularly with regards to plant life extension. It has been demonstrated that local approach methods have the potential to provide such estimates by assessing the likelihood of cleavage rupture.

Here a micro-structurally informed, post-processing, local approach methodology with a new rupture criterion is presented. This has been applied to a base and weld material pair, made available under the EU FP7 PERFORM 60 Programme. This material has been selected as tensile and fracture data are available along with results of recently performed analyses to characterise and quantify the size distribution of fracture initiators for the weld material (predominantly found to be alumino-silicates) which is used as an input to the model.

A series of finite element analyses have been performed for two-dimensional three-point bend specimens over a range of temperatures, constraint and irradiation states. Application of the local approach model to these results have then been favourably compared to the experimentally determined toughness. This has been achieved for a range of conditions when using the experimentally determined initiator particle distribution and maintaining the same calibration terms throughout for each material.
Parametric Study of the Coupling Power Factor for the Statistical Energy Analysis of Piping Acoustic Vibration
Authors: Dweib Ahmed H.
Published: January 2014

Energy-based finite element model is utilized for the evaluation of the Statistical Energy Analysis (SEA) coupling factor and the dependence of the coupling factor on the different system parameters is studied.

Previous research has shown that the coupling factor is largely dependent on the modal densities of the fluid and pipe subsystems, which depend on the pipe dimensional parameters. The coupling factor depends also on the spectrum of the acoustic power generated, which in turn depends on the mass flow rate, the pressure reduction ratio and the characteristics of the pressure-reducing device.

This study is concerned with the piping system parameters, downstream of the pressure-reducing valve. The system parameters selected for consideration are the pipe diameter to thickness ratio D/T and the pipe length to diameter ratio L/D. The study presents the effect of the variation in these two dimensionless parameters on the coupling factor.

The results of the analysis can be used directly in the formulation of SEA power flow equations for large piping systems with multiple sources of acoustic energy as part of the fatigue life evaluation in critical services.
Fatigue of Stainless Steel Components: Toward Codified Rules Improvements
Authors: Faidy Claude
Published: January 2014

During the past 30 years many fatigue tests and fatigue analysis improvements have been developed in France in order to improve Codified Fatigue Rules of French Nuclear Codes: RCC-M, RSE-M and RCC-MRx.

This paper will present comments and proposals for development of these rules associated to Gaps and Needs in order to finalize and justify the AFCEN Codes new rules.

Recently 3 new international R&D results confirm possible un-conservative fatigue material data:

- High cycle fatigue in air for stainless steel,

- Environmental effects on fatigue S-N curve for all materials, and in particular stainless steels,

- Fatigue Crack Growth law under PWR environment for stainless steel.

In front of these new results, AFCEN is working on a 1st set of rules based on existing knowledge:

- Air fatigue curve: mean and design

- PWR Environmental effects with detrimental correction factors

A periodic up-dating of AFCEN proposed rules will be done using French and International R&D programs with a particular attention on harmonization with other Code rules developed in USA, Japan and Germany, in particular.
The Influence of Viscous Dampers on the Better Performance of Water Pipelines Subjected to Near-Fault Earthquakes
Authors: Sadat Shokouhi Seyed Kazem , Dolatshah Azam , Vosoughifar Hamid Reza , Rahnavard Yousef
Published: January 2014

Experiences of the previous earthquakes such as Bam, Northridge etc demonstrate that lifelines have no proper performance due to Near-Fault (NF) earthquakes. Hence, this research evaluates the influence of viscous dampers on the better performance of the water pipelines subjected to NF earthquakes. For this purpose, the water pipelines network of a zone in Tehran city was selected as a case study. The pipeline network was modeled using Finite Element Analysis (FEA), and nonlinear time-history analysis was undertaken via seismic scaled records of NF earthquakes. The obtained results indicated the critical points of network which were failed due to seismic waves. As a solution, viscous dampers were employed for improving the behavior of the mentioned points. The obtained results demonstrate that the failure points were retrofitted efficiently by viscous dampers.
Acoustic Resonance Experiments in a Reservoir-Pipeline-Orifice System
Authors: Tijsseling Arris S. , Hou Qingzhi , Svingen Bjørnar , Bergant Anton
Published: January 2014

Acoustic resonance in liquid-filled pipe systems is an undesirable phenomenon that cannot always be prevented. It causes noise, vibration, fatigue, instability, and it may lead to damage of hydraulic machinery and pipe supports. If possible, resonance should be anticipated in the design process and be part of the hydraulic-transients analysis.

This paper describes acoustic resonance tests carried out at Deltares, Delft, The Netherlands, within the framework of the European Hydralab III programme. The test system is a 49 m long pipeline of 206 mm diameter that is discharging water from a 24 m high reservoir through a 240 mm2 orifice to the open atmosphere. The outflow is partly interrupted by a rotating disc which generates flow disturbances at a fixed frequency in the range 1.5 Hz to 100 Hz. In previous studies [1, 2] a similar system was analysed theoretically. Herein experimental data are presented and interpreted. Steady oscillatory behaviour is inferred from pressures measured at four different positions along the pipeline. Heavy pipe vibration during resonance was observed (visually and audibly) and recorded by a displacement transducer.
Fluid Transient Analysis for Safety Valve Vent Stack Using S-RELAP5 Code
Authors: Hsieh Jen-Sheng , Brocheny Pascal
Published: January 2014

This paper is to present a fluid transient analysis for the safety valve vent stack which is an open discharge system using the AREVA in-house thermal hydraulic code S-RELAP5. S-RELAP5 was developed by AREVA to perform thermal hydraulic analyses. It is a RELAP5-based thermal-hydraulic system code which incorporates features of the NRC RELAP5/MOD2 and RELAP5/MOD3 as well as other improvements. S-RELAP5 deals with one-dimensional two-phase, two-fluid, non-equilibrium hydrodynamic model with a non-condensable gas field.

ASME B31.1-2010 Non-mandatory Appendix II provides formulas for hand calculation of blow down forces at elbow exit and vent pipe. In general, this approach generates only steady state forces. To more accurately calculate forcing functions, S-RELAP5 is a good tool to achieve this task. The purpose of this S-RELAP5 application is to show that the usage of BRANCH and other components in the S-RELAP5 code can effectively simulate the safety valve open system discharge. This is a first-of-a-kind application of the code. Furthermore, this method provides an alternative to the ASME Appendix II hand calculation. In this paper a sample problem from ASME Appendix II is utilized to generate the time history forcing functions to demonstrate the versatility of S-RELAP5. These forcing functions can then be used for the subsequent piping dynamic analysis.
Time-History Analysis of a Super-Large Storage Tank Under Seismic Excitation
Authors: Bu Fan , Qian Caifu
Published: January 2014

In this paper, two finite element models are established for a super-large storage tank with or without a floating roof on the medium level. Time-history analysis with consideration of fluid-solid coupling for the deformation of tank wall and medium sloshing during or after an earthquake is performed with the emphasis on the effects of the floating roof. It is found that the upper part of tank is more sensitive to the earthquake action than the lower part. The wind girders and the reinforcing rings play a big role in limiting the radial deformation of the upper part of the tank wall. The floating roof has little effect on the tank wall deformation, but it is effective in suppressing the medium sloshing during the earthquake. After the earthquake, the radial deformation of the tank wall attenuates quickly, but the sloshing attenuation of the medium presents a slow progress and the floating roof inhibits the sloshing attenuation of the medium.
On the Hot Blow-Out Characterization of PTFE-Based Gasket Materials
Authors: Bouzid Abdel-Hakim , Benabdallah Samir
Published: January 2014

The objective of this work is to improve the HOt Blow-out Test procedure (HOBT) to determine the maximum operating temperature of Teflon-based gaskets. The study aims to analyze the relaxation of these gaskets due to creep at high temperature. The determination of their safe operating temperature limit requires a good knowledge of its capacity to resist creep-relaxation due to temperature exposure in the short and long term. This work investigates the effects cumulative gasket deformation due to thermal cycling, gasket stress level and holding time on the relaxation of these materials. In parallel, an experimental fixture has been developed to measure the thermal expansion coefficient and the short term creep resistance of such materials.

Based on a previous work, the introduction of a fixed number of cycles of heating and cooling in the HOBT test procedure has shown that ratcheting damage may have some impact on reduction of the gasket stress and the temperature limit of PTFE. The effect of holding temperature for a short period of time will also be investigated. The modified HOBT rig allows measurement of the gasket deflection during the test in order to accurately quantify the cumulative permanent deformation. Several types of PTFE-based gaskets will be tested in order to cover a wide range of gaskets to justify the generalization of the modified procedure.
The Brittle Strength Assessment of WWER-1000 Reactor Pressure Vessel Nozzle With Cladding
Authors: Oryniak Andrii , Radchenko Sergii , Orynyak Igor
Published: January 2014

Brittle strength calculation of RPV nozzle is the central point of the integrity assessment of the reactor pressure vessel when extending its life. The important part of this calculation is a determination of the stress intensity factor, SIF, for the postulated crack of partly elliptical form in a nozzle under inner pressure, bending moments (from the main circulating pipe) and difference of temperatures. In this paper we use method of influence functions as the most convenient one for solution of similar tasks. Eight basic laws of the crack surface loading are introduced which account for real stress distribution in the depth and length direction of a crack including the jump of stress between cladding and main metal due to the difference in the thermal expansion factors. To determine the dimensionless SIF under chosen laws of loading were developed the FEM models of nozzle with crack of different ratios of axes. For all possible modes (regimes) of operation were carried the detailed calculations of the temperature field in the nozzle, which were used later for determining the stress state at each time point. The stress field defined in 120 discrete points of the crack surface was treated by the method of least squares for the presention as a linear combination of eight basic load laws with defined coefficients. The procedure for determination of the temperature brittle strength margin which employs the presentation of critical values of SIF (fracture toughness) in the exponential function form is described.
Study on Evaluation Accuracy Required for Stress Intensity Factor Solution
Authors: Miura Naoki , Nagai Masaki , Shiratori Masaki
Published: January 2014

Stress intensity factor solutions are often used as a dominant fracture mechanics parameter for fatigue crack growth analysis. In ASME Boiler and Pressure Vessel Code Section XI as well as JSME Rules on Fitness-for-Service for Nuclear Power Plants, fatigue crack growth is predicted on the basis of the stress intensity factor range. Stress intensity factor solutions are frequently provided by the correction factors, which are tabulated as the functions of structure and/or crack sizes. In this study, the effect of the variation of the correction factors on the crack growth analysis results was investigated for pipes with surface cracks. The evaluation accuracy required for the correction factors of the stress intensity factor solutions was then examined and recommended from the comparison with the necessary accuracy of the parameters used for the fatigue crack growth analysis.