bluuebunny/crossref_metadata_2025 huggingface dataset:
Stability Derivatives in a Parallel Triangular Tube Bundle Subject to Cross-Flow at Moderated Reynolds Number
Authors: Charreton C. , Béguin C. , Yu R. , Etienne S.
Published: January 2014

This paper deals with the numerical and experimental determination of stability derivative inside a parallel triangular tube bundle for pitch Reynolds number Rep ∈ [60 3.104]. The present work focuses on the derivative of the lift coefficient, in the direction transverse to the flow, of the central cylinder for Rep ∈ [60 1.2.103]. We consider a viscous and incompressible flow for both approaches. First, experiments were done in a loop containing an adjustable central cylinder set with strain gauges to indirectly measure the lift derivative, via the moment of lift. Reynolds number is controlled by using a few glycerin solutions with different viscosities. In parallel, same flow conditions were simulated within 2D simulations. Comparisons were performed between experimental and numerical results. A critical Reynolds was found where the stability derivative seems to cross zero. This fact raises a question about applicability of quasi-steady model for fluidelastic instability.
Evaluation of Mass Transfer Coefficient Under Swirl Flow Generated by the Combination of Pipe Elements: Part 2
Authors: Yamamoto Kei , Suzuki Shota , Nakamura Takao
Published: January 2014

Flow accelerated corrosion (FAC) is a major pipe wall thinning phenomena in power plants. The management of pipe wall thinning has been carried out to pipe elements such as elbow, orifice, etc. of the piping system in power plants. The combination of analytical codes and measurement of pipe wall thinning is usually applied to thinning estimation methods. In piping system, several pipe elements which are connected in series may generate swirl flow. Therefore the arrangement of pipe elements is considered to affect thinning phenomena seriously. So the behavior of swirl flow is one of the major research targets to improve the accuracy of simulation codes. In Mihama Unit 3 pipe degradation accident in 2004, it was pointed out that the swirl flow caused by the piping layout might influence thinning rate behind orifice.

In the article Part1, we focus on the conditions and parameters (combination, distance, etc. of pipe elements) that affect the generation of swirl flow and analyze the effect of such parameters in mass transfer coefficient behind pipe elements. The generation of swirl flow is confirmed analytically in this study.

In the article part2, we develop new defined effective friction velocity considering the ratio between the change of average flow velocity and the change of turbulent velocity in the straight pipe. The effect of swirl flow on geometry factor is also evaluated by the new defined effective friction velocity. We also focus on the flow field of main-stream in the swirl flow. The result of analysis shows the generation of twin vortex under some combinations of pipe elements and suggests that twin vortex may affect the distribution of geometry factor. We compare the analytical results and estimate the cause of Mihama Unit 3 pipe degradation accident. The results of this study will be reflected to the evaluation of fluid-dynamic factor of FAC and improve the accuracy of simulation codes in near future.
Automatic Fatigue Monitoring Based on Real Loads - Calculation Example of a Flange
Authors: Jouan Benoît , Bergholz Steffen , Rudolph Jürgen , König Günter , Manke Andreas
Published: January 2014

The ageing management of power plants is nowadays a main issue for all nuclear industry actors: states, regulatory agencies, operators, designers or suppliers. Consequently, lots of operators have to deal with demanding security requirements to ensure the operation of power plants. Regarding with fatigue assessment of nuclear components, stringent safety standards are synonymous of new parameters to take into account in the fatigue analysis process, for instance: new design of fatigue curves, consideration of environmental parameters or stratification effects. In this context AREVA developed within the integral approach AREVA Fatigue Concept (AFC) new tools and methods to live up to operators’ expectations. Based on measured thermal loads, the Fast Fatigue Evaluation (FFE) process allows for highly-automated and reliable data processing to evaluate time-dependant cumulative usage factors of mechanical components. Calculation and management of results are performed with the software FAMOSi, thus impact of operating cycles on components in terms of stress but also with regard of fatigue can be taken into account to plan an optimized decision related to the plant operation or maintenance activities.

The FFE process was exemplary applied in 2012 in the EnBW Power Plant of Neckarwestheim (GKN II) to perform an informative fatigue diagnose of a spray line flange for different operating cycles. This paper describes the calculation methodology but also some relevant results to point out the benefits of this method to the ageing management of mechanical parts.
Experimental and Numerical 3D Study of Flow-Sound Interaction in a Steam-Line Gate Valve
Authors: Lacombe Romain , Lafon Philippe , Daude Frédéric , Crouzet Fabien , Ziada Samir , Bailly Christophe
Published: January 2014

Piping systems conveying gases at high pressure often generate high level of vibration and noise. These phenomena, in many cases, are initiated by the coupling between an unstable separated flow and an acoustic mode of the piping system. Various types of cavities in pipe flow are among the flow geometries which are known to be liable to the generation of tonal noise. Flow over cavities in ducts and piping systems has been investigated extensively for two and three dimensional situations. In this case, the feedback loop which generates the tonal noise is caused by the coupling between the instability of the shear layer forming at the cavity opening and an acoustic mode. This paper presents a study of tonal noise generation by subsonic pipe flows over a cavity formed inside a fully open gate valve. Previous 2D and 3D studies, presented in a companion paper, have shown that the presence of the valve-seat cavity is responsible for the generation of acoustic tonal noise. In this paper, the full 3D geometry of the valve, on a small scale model, is studied with experiments and using an unsteady compressible flow solver developed at EDF. Experimentally, the evolution of the fluid acoustic coupling in term of frequency and amplitude with the flow velocity is studied. Also, a modal analysis have been done to identify the frequency of acoustic mode of the valve. Numerically, the complex 3D geometry is meshed and computation is performed. The results show an acoustic tonal noise in a frequency range compatible with that experimentally. The study is underway, future analysis of the velocity and acoustic fields in the simulation may help to identify the shear layer and acoustic modes and to identify how they couple together.
Calculation of Elastic Fracture Mechanics Parameters Accounting for Residual Stresses
Authors: Boulay Antoine , Pellet Laure , Bargellini Renaud , Lei Yuebao
Published: January 2014

Most manufacturing processes induce residual stresses in metallic parts which can have a detrimental influence on the in service behaviour and on the integrity of structures. A good consideration of residual stresses is necessary to ameliorate the integrity of structures by avoiding unexpected failures and to have a better understanding and evaluation of the margins remaining in structures strength.

This paper addresses the evaluation and the cross-validation of formulations available in Code_Aster and ABAQUS accounting for the effect of residual stresses in the prediction of elastic fracture mechanics parameters: J-Integral (J) and energy release rate (G).

The latest versions of ABAQUS (from 6.11) and Code_Aster (from STA11.3) allow the effect of residual stresses to be considered in the calculation of the elastic J-Integral and energy release rate G. Contrary to the previous versions, the path-independency of the parameters (J and G) ensure reliable results both in 2D and 3D.
Experimental Investigation on Failure Estimation Method for Circumferentially Cracked Pipes Subjected to Combined Bending and Torsion Loads
Authors: Li Yinsheng , Hasegawa Kunio , Sakai Michiya , Matsuura Shinichi , Miura Naoki
Published: January 2014

When a crack is detected in a nuclear piping system during in-service inspections, the failure estimation method provided in codes such as the ASME Boiler and Pressure Vessel Code Section XI or JSME Rules on Fitness-for-Service for Nuclear Power Plants can be applied to evaluate the structural integrity of the cracked pipe. In the current codes, the failure estimation method for circumferentially cracked pipes includes bending moment and axial force due to pressure. Torsion moment is not considered.

The Working Group on Pipe Flaw Evaluation for the ASME Boiler and Pressure Vessel Code Section XI is developing guidance for combining torsion load within the existing solutions provided in Appendix C for bending and pressure loadings on a pipe. A failure estimation method for circumferentially cracked pipes subjected to general loading conditions including bending moment, internal pressure and torsion moment with general magnitude has been proposed based on analytical investigations on the limit load for cracked pipes. In this study, experimental investigation was conducted to confirm the applicability of the proposed failure estimation method. Experiments were carried out on 8-inch diameter Schedule 80 stainless steel pipes containing a circumferential surface crack. Based on the experimental results, the proposed failure estimation method was confirmed to be applicable to cracked pipes subjected to combined bending and torsion moments.
Verification of the Linear Matching Method for Limit and Shakedown Analysis by Comparison With Experiments
Authors: Ure James , Chen Haofeng , Tipping David
Published: January 2014

The Linear Matching Method (LMM), a direct numerical method for determining shakedown and ratchet limits of components, has seen significant development in recent years. Previous verifications of these developments against cyclic nonlinear finite element analysis have shown favourable results, and now this verification process is being extended to include comparisons with experimental results.

This paper presents a comparison of LMM analysis with experimental tests for limit loads and shakedown limits available in the literature. The limit load and shakedown limits were determined for pipe intersections and nozzle-sphere intersections respectively, thus testing the accuracy of the LMM when analysing real plant components. Details of the component geometries, materials and test procedures used in the experiments are given. Following this a description of the LMM analysis is given which includes a description of how these features have been interpreted for numerical analysis. A comparison of the results shows that the LMM is capable of predicting accurate yet conservative limit loads and shakedown limits.
RCC-MRx — Addenda 2013: Feedback of Application of the Code — Developments of Rules to the Evolution of Projects Needs
Authors: Pétesch C. , Lebarbé T. , Bonne D. , de la Burgade F. , Blat-Yrieix M.
Published: January 2014

The 2012 edition of the RCC-MRx Code has been issued in French and English versions by AFCEN (Association Française pour les règles de Conception et de Construction des Matériels des Chaudières Electro-nucléaires). This Code is the result of the merger of the RCC-MX 2008, developed in the context of the research reactor Jules Horowitz Reactor project, and RCC-MR 2007 which set up rules applicable to the design of components operating at high temperature and to the Vacuum Vessel of ITER.

A significant work has been performed in 2012 and early 2013 to improve the code in order to facilitate its use and understandability, and also to have a better fit with feedback of the main projects (ASTRID, RJH,…). This paper presents the assessment of application of the RCC-MRx and the amendments introduced by the 2013 addenda of the Code.
Study on a Combined Isolation Method for Large LNG Storage Tanks in Soft Site
Authors: Weng Dagen , Liu Shuai
Published: January 2014

The fundamental natural frequency that can determine the seismic response of large LNG storage tank is usually within 2Hz∼10Hz, it is in the range of predominant frequency of strong ground motion. It has been proved that the isolation control technique can be adopted to mitigate the seismic action on the liquid storage tank in the hard site, but in the soft site, if the conventional isolation design methods are still be used for seismic mitigation of the large LNG storage tank, the problems that the isolation period is too long, and the horizontal displacement of the isolation layer is too large under strong earthquake will be produced. For these problems, a combined isolation design method that is suitable for soft site is proposed in this paper. Based on the Malhotra’s simplified elastic-wall model of liquid storage tank, the simplified multi-mass mechanical model of combined isolated large LNG storage tank is established, and the seismic response of the LNG storage tank under the case of SSE (safety shutdown earthquake) is analyzed. The results show that the seismic-reduced effectiveness of the combined isolated LNG storage tank is obvious, and the horizontal displacement of isolation layer can be controlled in an acceptable range.
On-Line Monitoring of Cracks in Piping Weldment Using Array Probed Direct Current Potential Drop
Authors: Yoon Jae Young , Kim Ye Ji , Hwang Il Soon , Ayers L. , Short M. , Bromberg L. , Ballinger R. G.
Published: January 2014

The equipotential switching array probed direct current potential drop (ESAP-DCPD) system has been developed to monitor on-line the initiation and growth of a crack in piping weldment. The new technology of equipotential establishment at all borderlines of a monitoring segment eliminates any significant current leakage to outside systems. The thermal fluctuation of DCPD signal has been suppressed by using an already established switching current method. The arrangement of an array probe surrounding the weldment was optimized by performing finite element analysis (FEA) of DCPD in such ways to improve its detectability for circumferential cracks. In order to verify the reliability and detectability of piping weld monitoring, artificial cracks introduced into a full-scale weldment mockup were monitored by using ESAP-DCPD in laboratory environments. Then experimental results were compared with FEA results for the mockup to show a good agreement. Therefore FEA can be used to design a field application system. In order to pursue a first-of-a-kind application in a nuclear power plant, a preliminary licensing basis has been developed through development of an initial 10 CFR 50.59 analysis, as described herein.
Application of the Creep Italian Standard Through an Automatic Procedure and Comparison With the American Code
Authors: Grisolia Ottaviano , Scano Lorenzo
Published: January 2014

A previously-developed computer program [1] features the least-squares analysis for finding the best fitting model’s regression coefficients: The analysis is acted on points (test temperature, ultimate strength at 100000 hours) available in literature for any creep-sensitive material. The automatic procedure gives time to rupture at operation temperature directly through the model chosen for the curve Larson-Miller parameter (LMP) – stress. It applies the first-choice method in the Section II of the guideline [2] to the Italian technical procedure for creep-operated pressure vessel components [3].

Aim of the present work is to compare the results of the Italian code with those predicted by the API 579-1 standard [4]. Comparison is on data gathered by one author in his previous work [5]. That investigated a high energy pipeline after 230000 hours of service and calculated critical components’ life through an API 579-1 Level-3 assessment. Present study uses stresses from standard analysis based on B31.1 code [6] and from a finite element analysis (FEA, elastic and plastic): it finds out the residual life of three components, a 90-LR bend and two tees. Besides, it carries out creep assessment according to the Italian procedure and API 579-1 (Level 1 to 3); the former is LMP-approach based whereas the latter uses both LMP and the Omega methods.

For the Level-1 assessment (B31.1 stresses), the Italian procedure and the API 579-1 return consistent results. Acting a Level-2 assessment through an elastic FEA, results are consistent only when the API 579-1 analysis adopts the Omega Method. The LMP-approach method (minimum stress to rupture data) shows instead more conservative results. API 579-1 Level-3 assessment incorporates creep, plasticity and relaxation: When compared with the Italian procedure it predicts longer creep lives (up to a factor of ten).
Overview of International Implementation of Environmental Fatigue
Authors: de Haan - de Wilde F. H. E. , Hannink M. H. C. , Blom F. J.
Published: January 2014

For many nuclear power plants worldwide the operation period will be extended from 40 to 60 years in the coming years. As the operation period increases the importance of knowledge of ageing mechanisms like fatigue increases. Knowlegde of the influence of the environment is crucial, since environmental fatigue is a relatively new development which is a modification to the existing assessment method and has to be projected to 60 years as well.

This paper contains the results of a literature survey of environmentally assisted fatigue in nuclear power plants. It describes the current status and developments in the world. The main regulatory rules, guidelines and methods from the US, Germany, Japan, Finland and France are presented.

At this moment different approaches for incorporating the effect of the coolant water environment exist, although the general trend is towards a more uniform approach worldwide. The most common approach is the incorporation of an environmental fatigue correction factor (Fen) in the fatigue derivation of the cumulative usage factor. The Fen formulas and the S-N fatigue curves differ but the general equations are:

Fen = N air / N water

and

CUF = Σ U partial * Fen partial

Alternatives like using fatigue curves including the environmental effects, using threshold criteria and calculation of an allowable Fen based on testing, are described.

Research and material tests are still on-going and subject of international development. An overview of the current international state-of-the-art is presented.
Seismic Response of Unanchored Liquid Storage Tanks
Authors: Vathi Maria , Pappa Patricia , Karamanos Spyros A.
Published: January 2014

Unanchored liquid storage tanks under strong seismic loading may exhibit uplifting of their bottom plate, with significant effects on the dynamic behavior and the structural integrity of the tank. In the present paper, base uplifting mechanics is examined numerically through a two-step methodology: (a) a detailed finite element shell model of the tank for incremental static analysis, capable of describing the state of stress and deformation at different levels of loading and (b) a simplified modeling of the tank as a spring-mass system for dynamic analysis, enhanced by a nonlinear spring at its base to account for the effects of uplifting. Three cylindrical liquid storage tanks of different aspect ratios are modeled and examined both as anchored and unanchored. The results are aimed at possible revisions in the relevant seismic design provisions of EN 1998-4 and API 650.
Initiation of PWSCC in Nickel Base Alloy 182
Authors: Wehbi Mickaël , Crépin Jérôme , Couvant Thierry , Duhamel Cécilie
Published: January 2014

To date, welded nickel base alloy 182 used in Pressurized Water Reactors (PWRs) components have shown a higher susceptibility to Primary Water Stress Corrosion Cracking (PWSCC) during laboratory tests than in power plants. However, an increasing number of cracks reported in American, Swedish and Japanese nuclear power plants on Alloy 182 enlighten the need for a predictive initiation model of PWSCC. Initiation of PWSCC involves several factors such as material, environment and loading history, interacting with each other. Building such a model first requires to focus on these parameters separately, in order to have a better understanding of the involved mechanisms at a local scale in crack initiation. This study focuses on the correlation between EBSD/strain field results to improve the accuracy of the actual initiation model [1] involving local parameters.
Image Quality Assessment of Four Different Computed Radiography Systems for NDT Applications
Authors: Peterzol Angela , Bader Bruno , Banchet Julien , Caperaa Claire , Didier Vivian
Published: January 2014

Computed radiography (CR) is a digital radiographic technique, which uses very similar equipment to conventional radiography except that in place of a film to create the latent image, an imaging plate (IP) made of a photostimulable phosphor is used [1].

CR systems are commonly used in medical applications since they have proven reliability over more than two decades. Conversely, the NDT community has discussed the efficacy of film replacement by CR for more than 15 years. Though some standards were introduced in 2005 (ASTM E 2033, CEN EN 14784-2) and others are on the way (PR ISO 17636-2), CR is actually not included within the French RCCM, while the technique is commonly used in US for nuclear applications according to ASME (Section V, article 2).

Since 2006, AREVA has been evaluating the performance of CR in comparison to conventional RT in the framework of EN 14784 for the digital part and the RCCM for the conventional part. The objective was to build a technical justification report to eventually support introduction of CR into the RCCM.

In 2009 the subject gave rise to collaboration between AREVA NP – NETEC and EDF-CEIDRE, for a joint project to establish performance limits of CR towards EN 14784 specifications and RCCM image quality indicator (IQI) requirements [2]. In this paper, we present performance comparison results of four different CR systems. The measurements were conducted in 2012 and they demonstrate the current state of achievable image quality in CR. The performance has been evaluated for steel with a thickness range of 20÷60 mm using an Iridium 192 gamma source. Image quality has been assessed in terms of EN 462 and ASTM (E 747, E 1742) IQI. The results have been scored considering the PR ISO 17636-2, RCCM 2007, and ASME V-2010. This also permitted comparison among the different standard requirements.
Development of a Model for Low-Cycle Fatigue Assessment of 347 SS Butt-Welded Joints
Authors: Lang Eliane , Rudolph Jürgen , Beier Heinz Thomas , Vormwald Michael
Published: January 2014

This contribution deals with the low cycle fatigue behavior of butt-welded joints of austenitic stainless steel (1.4550, type 347). The focus is on the problem how to model these welded joints adequately with the objective of its assessment. Thereby, the differences between as-welded and machined weld are considered, in addition. The considerations — presented here — are based on previous investigations reported by Lang et al. [10]. Therein, a new approach was proposed in order to determine the local strains and the LCF relevant influence of the butt weld. It is based on material mechanics and includes an accurate modeling of the real weld geometry — based on 3D scans with very high resolution. Originating from this detailed model an idealized model is derived that takes into account significant parameters of a butt weld. In addition, the inhomogeneity of the weld is considered in the model, now, that has previously been ignored. Therefore, the part around the weld was partitioned in material zones according to their hardness. The underlying hardness measurements revealed significant influences of the load history. The results of the numerical simulations based on the new model are compared to them of the scan-based model and the measuring results from related fatigue tests. Considering further fatigue influences as the size and surface roughness the new approach is intended to be adopted in a global design and calculation concept for low-cycle fatigue assessment of butt-welded joints — applicable for normal users.
A Technical and Economic Comparison of Raised Face Versus Ring Joint Flanges
Authors: Reichert Christopher D. , Messer Barry , Reichert Larissa C.
Published: January 2014

On new construction projects, designers are frequently faced with the choice of whether to use raised face or ring joint flanges for piping systems. Often, decisions are made based on flange types used in the past, without due consideration for the merits of either style. On major piping projects, the decision can have significant and far reaching impacts for the owner of the facility, from a cost, constructability, and operational point of view.

The authors of this paper studied several recent projects in North America and Europe and performed a technical comparison of the strengths and weaknesses of each style of flange. The authors also performed a comprehensive estimate of the cost differential between using the different styles of flanges. The provision of both technical and economic data in one paper is intended to provide a resource of data that designers need to make an informed decision about which style of flange to use.
Evaluating the Performance of Urban Water Pipelines Using Hybrid HFA-FEA Approach
Authors: Sadat Shokouhi Seyed Kazem , Dolatshah Azam , Vosoughifar Hamid Reza , Rahnavard Yousef
Published: January 2014

Seismic behavior of the urban water pipelines has been considered due to its vital role, and also experiences of recent earthquakes which demonstrate poor seismic performance of mentioned pipelines. Previous experiences such as Bam (2003), Chile (2010) and Japan (2011) earthquakes indicated that urban water pipelines were out of service after earthquake and numerous problems were apparent on the post-disaster management. In this research, the water pipeline network of a zone in Tehran city was selected as a case study. The Hydraulic Failure Analysis (HFA) of the water pipelines in the proposed zone was carried out and failure potential points of the pipelines were determined. In addition, these points were investigated using orifice theory of leakage problem. Then, the proposed network was modeled using Finite Element Analysis (FEA). Also, nonlinear time-history analysis has been undertaken using three seismic scaled records of different earthquakes. Eventually, a statistical test demonstrated that there is a significant difference in the seismic performance of piping system before and after an earthquake.
Research and Development of a Rubber O-Ring Sealing Device for High Pressure Vessels
Authors: Zhou Fan , Chen Zhiping , Fan Haigui
Published: January 2014

An O-ring made of rubber exhibits excellent sealing performance with a wide range of applications. The highest sealing pressure can be up to 400MPa. The temperature ranges from −60 °C to 200 °C and the medium is low-corrosiveness. This paper proposes an O-ring sealing device for high pressure vessels, which can be opened and operated outside a cylinder. There are no bolts bearing the axial stress under the internal pressure load, and the sealing efficiency of this device is guaranteed by the dimension chain. The whole sealing device has no threaded connections except for the oriented screw which does not bear load under the working conditions. Based on this newly developed sealing device, a high pressure vessel with the design pressure of 60 MPa and the internal diameter of 700 mm used to simulate 6000 m deep sea environment is developed and investigated. This paper firstly introduces the rationale behind the design of the sealing structure for this high pressure vessel, and then discusses a finite element model of the cylinder end for this high pressure vessel and the stress classification method which is used to evaluate the safety of the critical sections. Lastly, the paper presents a set of experimental devices and a series of experiments which were carried out. The results show that the proposed sealing structure can be used in high pressure vessels. The results also verify the assumption of triangle contact pressure distribution between the shear ring and the cylinder end. It is hoped that this study will be of interest and value to researchers when they design the similar structures in the future.
Validation of the Accuracy of Approximation in a Design Formula for an Air Spring by Using Numerical Analysis
Authors: Asami Toshihiko , Yokota Yasutaka , Okura Masahito , Ise Tomohiko , Honda Itsuro , Sakamoto Hiroya
Published: January 2014

Previously, the authors proposed an approximation formula for designing an air spring that consists of two air tanks connected by a long pipe. The analysis was based on a linear approximation, so there is no amplitude dependency in the amplitude ratio for the sinusoidal vibration of a system with an the air spring. However, according to the experiment, it was found that there is remarkable amplitude dependency in a system with this type of air spring, so the frequency response curves for the system change with the magnitude of the input amplitude. It became clear that the approximation formula is in agreement with the limit value when the input amplitude approaches zero.

We consider that the deviation between the approximation formula and the experimental results are caused by the various assumptions which used in the analysis. As we remove these assumptions one by one, we perform the numerical analysis based on the finite difference method for this air spring. As a result, it was found that the effects of the turbulent flow in the pipe and the pressure loss at the inlet and outlet of the pipe are very small. A major influence is attributed in the connector that connects the pipe to the air chamber. The flow is throttled and disturbed at the connector whose inner diameter is smaller than the inner diameter of the pipe.
Dependence of Tensile Strength on Geometrical Interface Conditions of Bonded Dissimilar Materials
Authors: Tateno Masayoshi , Yokoi Eiichiro
Published: January 2014

Many engineering structures applied for generating energy are said to have been requiring high strength under high temperature conditions. Fine ceramic is expected to be useful in structural applications in various industries by joining to metals. Ceramic can be used in structural parts for engineering where resistance to high temperature and/or high strength are required from the viewpoint of the optimum structural design. Use of ceramic for engineering structures by joining to metal generates a bonded interface between the ceramic and metal.
Non-Destructive Detection of Crack in HDPE Plate by Nanometric Change in Surface Profile
Authors: Tada Naoya , Uchida Makoto , Matsukawa Yoshitaka
Published: January 2014

When a mechanical load is given to a cracked material, an undulation appears in surface profile around the crack. The undulation is caused by stress-strain concentration at the crack tip and its release near the crack center. If the load is very small and within the elastic deformation range, the material recovers the original shape after unloading and no damage remains. Therefore, this surface undulation by a small mechanical load can be used for detection of crack on the material surface. In this study, non-destructive crack detection method by nanometric change in surface profile is proposed, and the experiment and related finite element analyses were carried out for notched high-density polyethylene (HDPE) plates. Non-uniform height change by a small mechanical load around the notch on the surface of HDPE plate was measured by a laser scanning microscope. The height change distribution agreed with the analytical result.
Solid-Liquid Flow Through a Wellhead Choke Valve
Authors: Malavasi Stefano , Messa Gianandrea Vittorio , Ferrarese Giacomo
Published: January 2014

Wellhead choke valves are often subjected to the flow of solid-liquid mixtures due to sand production in oil extraction processes. Generally, the mixture is very dilute, and the main concern of engineers is the extensive wear arising from the continuous impacts between the particles and the internal parts of the valve. However, specific heavy oil extraction processes, such as the CHOPS technique, involve the production of a large amount of sand in the flow during the first months of life of the well. Many problems may arise from these high solid loadings, such as the change of regulation and dissipation characteristics of the device, and the risk of occlusion due to sand accumulation. In the present work the flow of sand-water mixtures through a choke valve is investigated by means of a two-fluid model which has already proved reliable for simpler flows. Starting from the single-phase flow case, validated with respect to our own experimental data, the effect of the presence of sand is studied, focusing on the influence of solids concentration (5 to 20%) and particle size (90 to 200 μm) on the dissipation characteristics of the device. Moreover, the distribution of the solids concentration is investigated to understand the behavior of the mixture and identify the most critical areas within the device.
To Determination of the WWER RPV Steels Crack Resistance Characteristics
Authors: Orynyak Igor , Zarazovskii Maksym , Radchenko Sergii , Kozlov Volodymyr
Published: January 2014

The efficiency of fracture toughness determined by the methodology of normative document PNAE G-7-002-86 has been analyzed.

Crack resistance characteristics of WWER-1000 reactor pressure vessel base metal at unirradiated condition are obtained by experimental way. All specimens were made of the RPV support forging (15Kh2NMFA steel) of abandoned Crimean NPP Fracture toughness experiments were carried out on three types of specimens CT 1T, CT 0.5T and SEB over a temperature range from −130°C to −40°C in fully accordance to the ASTM E1921. Charpy impact energy data obtained on twelve specimens over a temperature range from −80°C to 80°C has been used to determine the 47J transition temperature.

Comparison of obtained fracture toughness data with normative curve shows that the last one has unreasonably high lower shelf. It has been found that the PNAE G-7-002-86 Code, which uses the ideology of transition temperature shift, is too conservative to estimate WWER-1000 RPVs resistance against brittle fracture for the pressurized thermal shock (over 90 MPa·√m area of stress intensity factor).
Stress Analysis on New Multilayer Cylinder With Use of Thin Inner Shell and Cross-Helical Wound Shaped-Steel Ribbon for Pressure Vessels
Authors: Chen Ping , Chen Shuilian
Published: January 2014

In this paper, a stress analysis on a new type of multilayer cylinder using thin shell and cross-helically interlocked shaped-steel ribbon wound layers is carried out under the action of internal pressure based on the elastic and elastic-plastic mechanics.
Steam Methane Reformer Furnace Outlet Manifold Component Repair Experience
Authors: Oza Shaileshkumar H. , Penso Jorge A.
Published: January 2014

The steam methane reformer of RIL SEZ refinery was commissioned in 2009. Cold header replacement was planned in 2012, due to severe hot spots occurrences. While performing field welds at bull tee to cone material transitions, cracking was experienced when welding static cast tees (20Cr-32Ni-1Nb alloy) to hot header and reducers (cone). Cracks were reported in tees’s heat-affected-zones. Specific weld repair procedures were developed.

This paper discusses the in-service damaging mechanisms that apply to these headers including creep, thermal fatigue, thermal shock, metal dusting, thermal aging embrittlement and reheat cracking. This paper also discusses fabrication discontinuities such as solidification cracks, reheat cracks and ductility dip cracks. Then, the metallurgical analyses completed on the header components are discussed.

Finally, the repairs are described including the learning steps that led to the final successful repair. The following sections of this paper depict how the innovative engineering solution was arrived at, analyzing the risks of continued operation, inspection, monitoring, and finalizing the strategy for on-line repair to sustain operation.
Probabilistic Evaluation of the Integrity of Steam Generator Tubes Subjected to Flow Induced Vibrations
Authors: Hassan Marwan , Riznic Jovica
Published: January 2014

Flow-Induced Vibrations (FIV) continue to affect the operations of nuclear power plant components such as heat exchanger tube bundles. The negative effect of FIV is in the form of tube fatigue, cracking and fretting wear at the supports. Fretting wear at the supports is the result of tube/support impact and friction. Fluidelastic and turbulence forces are the two main excitation mechanisms that feed energy into the system causing these violent vibrations. To minimize this effect all support clearances must be kept at a very small value. This paper investigates the consequences of losing the effectiveness of a particular support as a result of corrosion or excessive fretting wear. A full U-bend tube subjected to both fluidelastic and turbulence forces is utilized in this work.
Derivation of the Depth Dependent Mechanical Characteristics of Ion-Irradiated F82H Steels by Using a Finite Element Analysis
Authors: Kim Jongmin , Shin Chansun , Noh Sanghoon , Lee Bongsang
Published: January 2014

Changes in mechanical material properties caused by neutron irradiation during the nuclear power plant operation are one of the key safety issues for the maintenance and long-term operation of nuclear power plants (NPPs). Ion-irradiation is widely used to simulate neutron irradiation condition in laboratory environment, such an irradiation effect on the material property is varied along the depth of a material subjected to ion irradiation. Since the ion irradiation induces a depth-dependent dose from the surface of a material. The load-depth (L-h) curve and nano-hardness measured from nanoindentation, which is used to obtain the material properties using small specimen, normal to the ion-irradiated surface is a result of complex average of varying mechanical property along the indentation depth.

The present paper investigates a method to evaluate depth (or dose)-dependent mechanical properties by combining experiment and finite element (FE) analysis of nanoindentation. The method is applied to reduced activation ferritic-martensitic steel, F82H. The material was ion-irradiated using Fe3+ ions of 1.7 MeV accelerating voltage at 300°C. The applicability of reverse algorithm was reviewed, and separate FE analyses were performed to determine material parameters by using trial set of material parameters. The ion-damaged surface layer was divided into several layers in the FE modeling. The L-h curve using determined stress-strain curve by using trial set of material parameters was found to be better agreement than reverse algorithm with experimentally measured one by nanoindentation. The advantage and limitation of the method investigated in this study will be discussed in detail.
Experimental Investigation of Friction Stir Seal Welding of Tube-Tubesheet Joints
Authors: Al-Badour Fadi A. , Merah Nesar , Shuaib Abdelrahman , Bazoune Abdelaziz
Published: January 2014

To ensure heat exchanger tube-tubesheet joints tightness, industrial standards may recommend performing a combination of roller expansion and seal welding, using conventional fusion welding processes. Solid state friction stir welding (FSW) has several advantages over the conventional fusion welding but has not yet proven its usefulness in seal and strength welding of heat exchanger tube-tubesheet joints where the available space is very limited and weld pass is of a relatively complex contour.

In this work, a newly designed tool and procedure are applied to friction stir seal weld (FSSW) tube-tubesheet joints. The effects of process conditions such as welding speed and tool offset on dependent process parameters including welding loads and joint quality are investigated on a 600-series aluminum three-tube test cell.

The results revealed that the quality of the seal weld of tube-tubesheet joints is affected by the preceding parameters at different levels.
Predictions of Creep Crack Initiation Periods in Pre-Compressed 316H Stainless Steel
Authors: Tarnowski K. M. , Davies C. M. , Webster G. A. , Dean D. W.
Published: January 2014

Pre-compression of 316H stainless steel significantly alters its tensile, uniaxial creep and crack growth behaviour. It has previously been shown that reliable and conservative creep crack initiation predictions can generally be obtained for as-received 316H stainless steel using a variety of prediction methods. Given the changes in material behaviour caused by pre-compression, this paper applies similar prediction methods to pre-compressed 316H stainless steel at 550°C.

Several procedures are available for estimating creep crack initiation time periods. The suitability of a procedure depends on the availability of the necessary material data. The procedures considered in this paper include the use of the creep fracture mechanics parameter C*, the crack opening displacement concept, the sigma-d approach and the time dependent failure assessment diagram.

Creep crack growth tests have been performed on compact tension specimens manufactured from 316H stainless steel which was uniformly pre-compressed by 4% and 8% at room temperature. For each test, the time for creep crack initiation to occur was recorded. Predicted creep crack initiation times have been compared with the experimentally determined values. Comparisons with as-received material are also included.

For pre-compressed material, conservative creep crack initiation predictions were only consistently achieved using steady state creep crack growth rates predicted from C*. This is a significant difference to as-received material for which conservative predictions were generally obtained by a variety of methods. At this time, there is only a limited set of pre-compressed data making it difficult to draw firm conclusions about the appropriateness of the various creep crack initiation prediction methods. The differences in the results between the pre-compressed and as-received material do however highlight the need for further tests on pre-compressed material.
Investigation of Soil-Structure Interaction and Higher-Mode Effects on Dynamic Response of Base-Isolated Structure Founded on Half Space
Authors: Tsai C. S. , Su H. C.
Published: January 2014

This paper attempts to investigate the effects of soil-structure interaction (SSI) and higher modes on the dynamic responses of base-isolated structures through closed-form solutions for a superstructure, seismic isolator, and soil system under various conditions, comprising the cases of rigid and half-space foundations. The proposed system considers continuum media for both the superstructure and soil foundation, which can take the effects of higher modes into account, along with a discontinuous layer with a governing equation that interprets the mechanical behavior of the base-isolation system. Then, the closed-form solutions in terms of well-known frequency and impedance ratios under various conditions of soil foundations were obtained through rigorous mathematical derivations and validations by collapsing the entire system to a single degree-of-freedom system in structural dynamics and well-known cases of wave propagation in elastic solids. The closed-form solutions derived in this study explicitly revealed the characteristics of the SSI and higher mode effects in influencing the seismic behavior of base-isolated structures. Furthermore, the SSI effects on the dynamic responses of the entire system were extensively evaluated. The conclusive results of this paper will be useful for understanding the SSI and higher mode effects on the dynamic responses of base-isolated structures.
Overview of the Fatigue Design Discussions in the United States From These Past 10 Years
Authors: Harrison Harry , Gurdal Robert
Published: January 2014

The topic of fatigue is probably the topic that has been discussed the most in the U.S. these past ten to fifteen years during the ASME-Code Meetings. It seems now that the rules dictated by the U.S. NRC will be final in the U.S. sometime during the year 2014. These final rules could possibly have an influence on the other countries, although some of these other countries have already noticed that these Fatigue Rules are very severe, especially when penalizing the ASME-Code usage factors by the environmental F(en) factors proposed by the U.S. NRC and the associated procedures.

The purpose of this paper is to describe some of the past and on-going discussions taking place in both the United States and Europe, and to present the most important comparison Figures, as far as those new Rules are concerned. These comparison Figures are for both in-air fatigue design and fatigue design with the consideration of the environmental effects. Comparisons need to be performed, for example, between past component fatigue tests and the new fatigue Rules provided by the U.S. authorities.

In addition, suggestions for future simplified rules are presented in this paper. These simplified Rules are for the fatigue design when using the ASME-Code from the U.S. or a modification of the current ASME-Code fatigue methodology in case the severe F(en) factors need to be applied.
Fully-Plastic Strain-Based J Estimation Scheme for Circumferential Surface Cracks in Pipes Subjected to Reeling
Authors: Parise Luís F. S. , Ruggieri Claudio , O’Dowd Noel P.
Published: January 2014

Modern installation techniques for marine pipelines and subsea risers are often based on the reel-lay method, which introduces significant (plastic) strains on the pipe during reeling and un-reeling. The safe assessment of crack-like flaws under such conditions requires accurate estimations of the elastic-plastic crack driving forces, ideally expressed in a strain-based formulation to better account for the displacement controlled nature of the reeling method. This paper aims to facilitate such assessments by presenting a strain-based expression of the well-known EPRI estimation scheme for the J integral, which is directly based upon fully plastic descriptions of fracture behaviour under significant plasticity. Parametric finite element simulations of bending of circumferentially cracked pipes have been conducted for a set of crack geometries, pipe dimensions and material hardening properties representative of current applications. These provide the numerical assessment of the crack driving force upon which the non-dimensional factors of the EPRI methodology, which scale J with applied strain, are derived. Finally, these factors are presented in convenient graphical and tabular forms, thus allowing the direct and accurate assessment of the J integral for circumferentially cracked pipes subjected to reeling.
Extrapolation of Creep Strength by Fracture Energy for 316FR Stainless Steel at 823K
Authors: Nagae Yuji , Asayama Tai
Published: January 2014

316FR stainless steel is a candidate material to be used for a reactor vessel and internals for fast reactors with a design life of 60 years at an operating temperature of 823K. This paper describes an extrapolation approach based on fracture energy for calculating creep strength. A change in fracture energy is assumed to be expressed as a power-law function of time to failure and energy density rate. The energy density rate is calculated using initial stress, rupture elongation, and time to rupture. It is important to evaluate a change in rupture elongation for the extrapolation of creep strength at 823K. The time to rupture at 823K is estimated and extrapolated on the basis of the fracture energy approach. This paper shows the validity of extending the design life to 60 years by using the Larson–Miller parameter compared with the estimation by the fracture energy approach.