bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ductile Fracture Assessment of Plates Under Biaxial Loading
Authors: Meek Caroline , Ainsworth Robert 
Published: November 2014

There is currently little detailed advice on biaxial and triaxial effects on fracture in fitness-for-service codes and engineering assessment procedures. There has been historical and recent research into such effects using numerical, finite element and experimental investigations into biaxial effects on fracture toughness and J-integral estimation.
However, these studies cover only limited ranges of loadings with, for example, few investigations into loading regimes where the biaxial ratio exceeds unity, i.e. where the loading in the direction of a crack exceeds the crack opening force. This paper first briefly summarises a literature review focussing on the experimental information available on the effects of biaxial loading on ductile fracture. It transpires that although there have been a number of numerical and experimental investigations of biaxial fracture a systematic examination of the effects of biaxial loading is missing in terms of the effect on the crack driving force. Therefore, the paper develops advice for assessment of simple plate geometries under a wide range of biaxial loading conditions to provide advice and recommendations for future inclusion in fitness-for-service codes.
Low Cycle Fatigue Behavior in Air and in PWR Water of a Type 304L Austenitic Stainless Steel Manufactured by Hot Isostatic Pressing Process
Authors: De Baglion Laurent , Cedat Denis , Ould Pascal , Chitty Walter-John 
Published: November 2014

In most industries and more particularly in the Nuclear one, the use of new materials or new manufacturing methods is really challenging because “safety” is still the key point. Among many characterizations required for a new steel grade or a new manufacturing process to be accepted and then introduced in a Nuclear design code, the fatigue properties must be determined with great care.
Nowadays, the consideration of the Pressurized Water Reactor (PWR) primary water environment effect on the Low Cycle Fatigue (LCF) behavior of Austenitic Stainless Steels is an important issue for both Nuclear Power Plants (NPP) lifetime extensions and new builds as described in NUREG/CR-6909 [1].
This study aims to present the LCF behavior in Air and in PWR water at 300°C of a type 304L steel manufactured by Powder Metallurgy coupled with Hot Isostatic Pressing process (PM/HIP) and to compare them with those observed on 304L nuclear grade products such as rolled plate or forged branch [2–5]. It appears that the LCF behavior in Air and in PWR water of this 304L HIP material is better or at least similar to the one observed on classical 304L steels.
Impact of Deformation Stiffness Beyond Yield Point of Pipe Support Structures on Nonlinear Seismic Response Analysis
Authors: Takahashi Tsuneo , Maekawa Akira 
Published: November 2014

The importance of safety evaluation for beyond design conditions has come to be required since the accident at the Fukushima Daiichi Nuclear Power Plant as a consequence of the Great East Japan Earthquake. Real simulations of seismic response for the plant structures and components enhance establishment of reasonable design margins and safety evaluation criteria in a situation beyond design-basis accidents. For piping systems, nonlinear seismic response analysis considering plastic deformation of pipe support structures can lead to a safety evaluation based on more rational input values.
This study discussed seismic response of a piping system and its appropriate analysis method when a plastically deformable pipe support structure was subjected to a much larger seismic load than the designed one. Seismic response analyses of the piping system including a plastically deformable pipe support structure were conducted for various input acceleration levels. The vibration characteristics, response acceleration, and moment of piping were compared in relation to the amount of plastic deformation of the pipe support structure. As a result of the comparisons, a support model with the elastic fully plastic property was proposed as a simple and proper method to calculate the seismic response of the piping system considering the plastic deformation of the pipe support structure.
Study on Equivalent Stress to Control Average Inelastic Behavior of Perforated Plates
Authors: Kultayev Yeldos , Kasahara Naoto 
Published: November 2014

Next generation reactors which are subjected to elevated temperatures must be designed to account for inelastic deformation along with elastic one. In order to simplify design analysis of perforated portions, conventionally axisymmetric models with equivalent elastic materials are employed. To extend to inelastic analysis, a method of Effective Stress Ratio (ESR) has been studied in recent years. Previous studies have shown that perforated plates have their own ESR and it is a function of geometry and is independent from their materials.
In this study the only geometry dependence and physical meaning of ESR were clarified. ESR results were compared with Reference Stress Method (RSM) results for unit-ligaments with various ligament efficiencies. It was revealed that RSM results coincide with ESR. First meaning of ESR is stress ratio between solid plate and perforated plate at the same reference stresses. Second meaning of this ratio is how plasticity properties of equivalent solid plate have to be changed to give the same steady state deformation rate at the same mean boundary stress. Moreover, to clarify stress redistribution control mechanism at different ligament efficiencies, simple models were developed and an estimation method based on simple models was proposed for engineering use.
Proposal for Update on Evaluation Procedure for Reactor Pressure Vessels Against Pressurized Thermal Shock Events in Japan
Authors: Hirota Takatoshi , Sakamoto Hiroyuki , Ogawa Naoki 
Published: November 2014

The evaluation procedure for the reactor pressure vessel integrity of Japanese PWR plants against Pressurized Thermal Shock (PTS) events is prescribed in the Japan Electric Association Code, JEAC 4206, “Method of Verification Tests of the Fracture Toughness for Nuclear Power Plant Components” since 1991. The current procedure was developed based on the PTS verification test program, which was conducted as Japanese national project and the related studies in 1980’s.
Since much progress has been made on fracture mechanics, fracture toughness, in-service inspection techniques/results and so on, it is preferred to advance the current procedure for more credible evaluation by reflecting the latest knowledge.
This paper describes the outline of the studies to update the current procedure.
Crack Growth Prediction and Leakage Potential of Steam Generator Tubes Subjected to Flow Induced Vibrations
Authors: El Bouzidi Salim , Hassan Marwan , Riznic Jovica 
Published: November 2014

Nuclear steam generators are critical components of nuclear power plants. Flow-Induced Vibrations (FIV) are a major threat to the operation of nuclear steam generators. The two main manifestations of FIV in heat exchangers are turbulence and fluidelastic instability, which would add mechanical energy to the system resulting in great levels of vibrations. The consequences on the operation of steam generators are premature wear of the tubes, as well as development of cracks that may leak radioactive heavy water.
This paper investigates the effect of tube support clearance on crack propagation. A crack growth model is used to simulate the growth of Surface Flaws and Through-Wall Cracks of various initial sizes due to a wide range of support clearances. Leakage rates are predicted using a two-phase flow leakage model. Non-linear finite element analysis is used to simulate a full U-bend subjected to fluidelastic and turbulence forces. Monte Carlo Simulations are then used to conduct a probabilistic assessment of steam generator life due to crack development.
Numerical Characterization of the Area Perturbation and Timelag for a Vibrating Tube Subjected to Cross-Flow
Authors: El Bouzidi Salim , Hassan Marwan , Fernandes Lais L. , Mohany Atef 
Published: November 2014

Fluidelastic instability can have disastrous effects on the integrity of steam generators. Over the last five decades there has been a great deal of research done in an attempt to understand this phenomenon. These efforts have resulted in several theoretical models and design guidelines. The semi-analytical model of fluidelastic instability initially developed by Lever and Weaver is based on a single tube in a channel flow. The mechanism responsible for instability was found to be one of flow redistribution. While previous studies have been able to characterize the pressure and velocity within a tube bundle, the behaviour of the area of the channel has not yet been fully investigated.
The current study aims to characterize the area of the channel surrounding the tube. Reynolds Averaged Navier Stokes (RANS) equations are cast in an Arbitrary Lagrangian Eulerian (ALE) form and are used to compute the flow conditions in a rigid tube bundle due to a single flexible tube vibrating in the transverse direction. The properties of the velocity field are used to determine the channel boundaries. Properties of the channel area such as area perturbation, mean area, and area phase are investigated for various reduced flow velocities. Dynamic simulations are conducted to determine the impact on the stability threshold for transverse fluid force cases using a mass damping parameter range of 10–200.
Void Fraction Effect on Added Mass in Bubbly Flow
Authors: Béguin C. , Pelletier É. , Étienne S. 
Published: November 2014

This paper proposes a relation for the added mass coefficient of spherical bubbles depending on void fraction based on results obtained by a semi-analytical method.
This information is essential to completely characterize finely dispersed bubbly flows, where small spherical gas bubbles are present in a continuous liquid phase. Most of the closure relations for Euler-Euler or Euler-Lagrange models are obtained from experiments involving single bubbles. Their applicability to systems with high void fraction is therefore questionable.
This paper uses solid harmonics to solve 3D potential flow around bubbles. Several configurations were calculated for different numbers of particles and spatial arrangements. Our results are compared with previous studies. Depending on the model proposed by previous authors, added mass forces could increase or decrease with the void fraction. This paper solves these discrepancies.
The main purpose of this work is to develop simple formulas fitting our semi-analytical results. These simple formulas are suitable for further use, particularly as added mass models for multiphase flow averaged equations.
Effect of Nonlinearity of Rubber Bearing on a Seismic Isolated Structure Considering Their Layout
Authors: Chirez Sebastien , Fujita Satoshi , Minagawa Keisuke 
Published: November 2014

In Japan, in order to ensure seismic safety requirements for buildings such as hospitals, nuclear power plants and communication centers for instance, seismic isolation systems have been developed. The most widely used technologies are rubber bearings and oil dampers, which can enhance the protection of equipment or machinery set up in those buildings. However, the isolation performance may face difficulties in case of huge earthquakes because of the nonlinearity of rubber bearings.
In a former study of our laboratory, an earthquake response analysis based on the Runge-Kutta-Gill’s method had been carried out in order to assess the behavior of the rubber bearings[1]. In this paper, we use the same method but for further accurate and more realistic simulations, the analytical model has been improved in order to assess the response of rubber bearings depending on their layout when we consider the rocking of the building.
Specificities of Welding Activities in RCC M
Authors: Malouines Philippe , Lainez Bernard , de Mathan Nicolas , Wasylyk Andrew 
Published: November 2014

The paper will cover the general approach of welding requirements in RCC-M 2012Ad2014[1], from a technical and quality point of view.
It will be clarified how EN standards has been taken in account, mainly due to developments pushed by Pressure Equipment Directive (97/23/EC)[2] in Europe. It will be explained how nuclear activities for welding need to restrain the use of standards developed firstly for the needs of non nuclear industries. New ISO/ EN standards related to welding (ISO 9606-1, ISO 15614-1, ISO 3834) will be considered, and how they may lead to international cohabitation, compatibilities or harmonization, between nuclear codes.
Uncertainties and Margins in Environmental Fatigue Analysis Rules
Authors: Faidy C. 
Published: November 2014

During the past 30 years the main rules for fatigue analysis of pressure vessels were based on elastic approaches in order to evaluate cyclic strain amplitude and compare with an S-N fatigue curve for the corresponding material. After review of some rules in different Nuclear and Non-Nuclear Codes, like ASME Boiler & Pressure Vessel Code Section III, French RCC-M and RCC-MRx, European Standards EN 13445, the major conservatisms and uncertainties of different rules are discussed.
All these Codes propose simple rules to evaluate the strain amplitude based on elastic approaches and simplified correction factors (Ke and Kν), transient combination rules and damage cumulating procedure.
In the other hand, the material properties are based on standard fatigue tests done on the material associated to reduction factors to consider some particular effects like scatter, scale, surface roughness, mean stress or environmental effects to transfer them from small specimen to real structures.
Concerned components in this paper are mainly piping systems.
No existing Code covers all the aspects of fatigue with similar conservatisms that can affect the in-service inspection programs and the remaining life assessment of the corresponding components.
After the review of different rules, key factors that affect the results and predictions will be identified. Some proposals will be issued to progress in the near future.
Finally, a first set of recommendation on fatigue analysis will be presented to improve existing codes on harmonized way, associated to material properties needed, as fatigue curves associated to reduction factors.
Life Extension of Hydrocarbon Equipment in Sour Environment
Authors: Al-Mithin Abdul Wahab , Kumar G. Santhosh , Al-Shaiji Mohammad , Hannan Abdul Sattar A. , Jose Vinod 
Published: November 2014

Reliability of equipment is indispensable for the uninterrupted operation of any oil & gas producing facility. Over a period of time, some oil wells producing sour crude were also added to the incoming feed of Gathering centres, which were originally designed for processing sweet crude. Most of the facilities were designed and installed prior to the publication of NACE MR 0175 and NACE TM 0284. As these facilities are still in operation under sour condition, it is prudent to take necessary measures in time for continuing safe operation of these facilities.
In this paper, the authors share their experience in initial detection & online monitoring of service-induced damages to the equipments due to sour service using NDT techniques like Wet Fluorescent Magnetic Particle Inspection, manual ultrasonic testing and time of flight diffraction & Phased Array. The experience gathered during internal coating of the vessels has also been described. Several items of equipment continued in operation to maintain production even after the detection of Hydrogen induced cracking. Periodic monitoring and critical analysis of inspection data provided confidence to continue operation of equipment. This enabled the operating company to extract maximum life of the equipment without compromising on safety.
This Paper focuses on two items of equipment, HP Gas Scrubber from Oil/Gas separation plant and HP Gas Discharge Cooler from CRU. Fitness for Service (FFS) evaluations were carried out for HP Scrubber and the Channel head component of HP Gas Discharge cooler. The analysis was based upon the latest UT scan results and guidelines prescribed in API 579-1/ASME FFS-1. These items of equipment were found not fit for further service. In the interim period, the company procured new scrubber and channel head of the cooler for replacement thus minimizing the shutdown period.
ASME III Fatigue Assessment Plasticity Correction Factors for Austenitic Stainless Steels
Authors: Emslie Julian , Watson Chris , Wright Keith 
Published: November 2014

ASME III NB-3200 provides a method for carrying out fatigue calculations using a simplified elastic-plastic analysis procedure. This allows a correction to elastic analysis to be performed in place of a full elastic-plastic analysis. Two mutually exclusive factors are described: the Poisson’s ratio correction accounts for surface stress exceeding the yield strength of the material and the Ke factor accounts for gross section plasticity. The recently released ASME Code Case N-779 provides a more complex but less onerous calculation of the Ke factor. Correction factors from the JSME and RCC-M codes have also been considered in this paper.
The conservatism of different plasticity correction factors has been examined by calculating a ratio between the equivalent strain range from elastic-plastic Finite Element (FE) models and the strain range from elastic FE models and comparing this to calculated plasticity correction factors. Results show the potential for both the current ASME and Code Case Ke corrections to under-predict the strains when compared to those from an elastic-plastic FE assessment.
A preliminary investigation has been carried out into an alternative correction factor based on linearised stress and local thermal stress ranges. This addresses the discontinuity between the two correction methods for surface and sectional plasticity which has been identified as a feature of the ASME correction methodology.
Development of Generic Failure Frequency of LNG Plant Equipment Using Offshore Reliability Data
Authors: Kang Seok-Jun , Kim Moon-Ki , Choi Jae-Boong 
Published: November 2014

American Petroleum Institute (API) introduced the methodology, which is called Risk-Based Inspection (RBI), for calculating the risk of equipment operated in refinery or petrochemical plants [1]. However, RBI has limitations for applying directly to LNG plants, because API makes the RBI code suitable only to refinery or petrochemical plants. Especially, developing new gff value is needed, because RBI results can be influenced as generic failure frequency (gff) changes [2].
The objective of this paper is recommending new gff only for the main equipment in LNG plant. In order to solve the problem, three gffs will be used. The three are API providing gff value, the gff obtained by OREDA which gathers the data during long period in offshore petrochemical and gas plant, and the gff from real data of Test bed train No.1 working in the present [3]. In this respect, POF values which are calculated by API gff and OREDA gff will be compared. Afterward, the reliability of each cases will be verified by using operating data of Test bed train No.1.
Reciprocating Compressor Cylinder’s Cooling: A Numerical Approach Using CFD With Conjugate Heat Transfer
Authors: Balduzzi Francesco , Ferrara Giovanni , Babbini Alberto , Maleci Riccardo 
Published: November 2014

The working cycle of a reciprocating compressor is characterized by heat generation, mainly due to compression transformation and friction phenomena. The main consequences are a reduction of the volumetric efficiency and an increase in the gas discharge temperature. Current regulations such as API618 for reciprocating compressors require a cylinder cooling system. Therefore, a proper design of the cooling circuit is needed in order to achieve the best balance between refrigerating potential and system capacity.
A systematic methodology for the evaluation of the heat transfer process is essential and since experimental characterization of the circuit is complex and case-dependent, the use of a numerical technique is the most favorable and generalizable approach. Within this scenario, 3D analysis shows a great potential although several phenomena must be accounted for in order to accurately model the system.
In this paper, a conjugate heat transfer (CHT) analysis on a double-acting water-cooled reciprocating compressor cylinder is presented, where the three-dimensional flow field of the water circuit and the thermal conduction inside the solid metal are solved simultaneously. The best practice for the imposition of consistent boundary conditions for the metal body is given with special attention to the heat transfer coefficient values for the suction and discharge gas chambers, the compression chamber and the external ambient. The assessment of the numerical methodology is completed with an investigation on the influence of wall roughness and buoyancy effects.
Dynamics of the Forced Karman Wake: Comparison of 2D and 3D Models
Authors: Mureithi Njuki W. , Xu Xiaofei , Baranyi Laszlo , Nakamura Tomomichi , Kaneko Shigehiko 
Published: November 2014

The interaction between the cylinder motion and the wake is a complex feedback phenomenon in which the symmetry relationship between the wake and the cylinder motion plays a key role. Depending on the frequency of oscillation the symmetry relationship between the unforced von Karman wake and the imposed forced oscillations can induce a series of bifurcations. This detailed bifurcation behavior is the subject of study in the present work. 2D and 3D simulations are carried out for a Reynolds number Re=1000. As the inline cylinder forcing amplitude is increased, the wake undergoes a series of bifurcations and associated changes in the flow structure. Although the 2D analysis is clearly non-physical, it leads to a ‘simpler’ and more tractable model.
Detailed comparison of the 2D and 3D POD modes provides insight into the forced wake dynamics. The 3D spatial mode shapes are significantly similar to those from 2D simulations. The relative modal energy distribution captures well the wake flow complexity. The first mode contains over 90% of the flow energy in the 2D simulations. This ratio drops significantly in the 3D case to around 45%. Clearly 3D effects are very important when it comes to energy distribution between the modes. However, the predominance of the first mode seems high enough to maintain the 2D-like dynamics.
The wake flow is found to undergo two main transitions with increased forcing. The first is periodic shedding to chaotic shedding. The second is chaotic shedding to half-frequency shedding caused by a period-doubling bifurcation. The 2D simulations correctly predict these bifurcations — including the type and the number of bifurcations. The results suggest that the forced wake dynamics are primarily dominated by two-dimensional rather than 3D dynamics. However, 3D effects are important in determining the exact parameter values where bifurcations occur. A previously developed low order analytical model, based on 2D simulations, is also used to predict the wake bifurcation behavior. The relevance of the low order model has interesting implications for VIV control.