bluuebunny/crossref_metadata_2025_split huggingface dataset:
Residual Stress Measurement in a Stainless Steel Clad Ferritic Plate Using the Contour Method
Authors: Naveed Nida , Hosseinzadeh Foroogh , Kowal Jan 
Published: January 2014

In pressure vessels stainless steel weld-overlay cladding is a widely used technique to provide a protective barrier between the corrosive environment and the ferritic low alloy base metal. While the cladding layers enhance corrosion resistance, the induced residual stresses due to the deposition of weld layers are of major concern. It is of paramount importance to understand how residual stresses interact with service loading when the vessel is pressurized. Therefore, knowledge of the initial residual stresses due to cladding is an essential input for structural integrity assessment of pressure vessels.
In the present paper the Contour Method was conducted to measure residual stresses in an austenitic steel cladded plate that was fabricated from a ferritic steel base plate with three layers of austenitic stainless steel weld metal cladding deposited on the top surface. The Contour Method was chosen for various reasons. First, it provides a full 2D variation of residual stresses over the plane of interest. Second, it is not limited by the thickness of components or microstructural variations and finally it should potentially capture the variation of residual stresses in each individual weld beads and due to the possible phase transformation in the ferritic base material. The map of longitudinal residual stresses was measured by sectioning the test component along a transverse plane at mid-length. The measured residual stresses were in good agreement with published results in the open literature.
Flaw Criticality Assessment for Core Spray Sparger Support Bracket Shroud Cracking
Authors: Vecchio Robert S. , Gosselin Stephen R. , Wolfe Ken 
Published: January 2014

Stress corrosion cracking (SCC) has been observed in the weld joining the core spray sparger bracket to the core shroud at a number of Boiling Water Reactors (BWRs). The cracking occurs preferentially on the shroud side of the weld and has typically been detected with visual inspections. Limited ultrasonic (UT) inspections have been performed at selected plants. EPRI BWRVIP investigations showed that the cracks are relatively shallow and oriented in the radial direction (with respect to the shroud). This report documents results of a project performed by LPI (Lucius Pitkin, Inc.) whose objective was to develop a generic fitness-for-service evaluation for the observed cracking.
Deterministic SCC crack growth calculations were performed associated with cracking observed in the field. The extent of crack growth was based on the 95 percentile K-dependent the crack growth rate (da/dt) relationship for the BWR shroud materials identified in BWRVIP 14A [1]. The calculations also considered the changes in material properties and crack growth rates as the crack extends beyond the weld HAZ within the shroud thickness. The results demonstrate that the cracking is essentially benign and that extraordinary efforts to characterize fully the cracking are unwarranted. These results will be used as part of the technical basis for revised BWRVIP guidance for inspection of the sparger brackets.
Study on In-Flow Fluidelastic Instability of Circular Cylinders Caused by Air Cross Flow (Triangular Arrays)
Authors: Nakamura Tomomichi , Fujita Yoshiaki , Sumitani Takuya , Hagiwara Shinichiro 
Published: January 2014

The in-flow instability of cylinder arrays corresponds to the in-plane instability of U-bend tubes in steam generators. This rarely occurring phenomenon has recently been observed in a nuclear power plant in U.S.A. For this reason, the importance of studying this instability has recently increased.
The fluidelastic instability of a cylinder array caused by cross-flow was found to easily occur in air-flow and hardly in water-flow in our previous report. The present report introduces the results of this phenomenon in several patterns of triangular cylinder arrays in air-flow. The pitch spacing between cylinders is one of the parameters, which varies from P/D = 1.2 to 1.5, for a five-by-five cylinder array. The instability is examined both in the in-flow direction and in the transverse direction. The test cylinders are supported with thin plates to move in one direction. The number and the location of the flexibly supported cylinders are the other parameters.
Differences between the instability in the in-flow and in the transverse direction are found. Among these differences the most important is the fact that the fluidelastic instability has not been observed for a single flexible cylinder in the in-flow direction, although it is observed in the transverse direction.
However, the in-flow instability can be estimated with the Connors’ type formula as in the transverse direction.
Evaluation of Creep-Fatigue Damage Based on Simplified Model Test Approach
Authors: Wang Yanli , Li Tianlei , Sham T.-L. (Sam) , Jetter Robert I. 
Published: January 2014

Current methods used in the ASME Code, Subsection NH for the evaluation of creep-fatigue damage are based on the separation of elevated temperature cyclic damage into two parts, creep damage and fatigue damage. This presents difficulties in both evaluation of test data and determination of cyclic damage in design. To avoid these difficulties, an alternative approach was identified, called the Simplified Model Test or SMT approach based on the use of creep-fatigue hold time test data from test specimens with elastic follow-up conservatively designed to bound the response of general structural components of interest. A key feature of the methodology is the use of the results of elastic analysis directly in design evaluation similar to current methods in the ASME Code, Subsection NB. Although originally developed for current material included in Subsection NH, recent interest in the application of Alloy 617 for components operating at very high temperatures has caused renewed interest in the SMT approach because it provides an alternative to the proposed restriction on the use of current Subsection NH simplified methods at very high temperatures.
A comprehensive review and assessment of five representative simplified methods for creep-fatigue damage evaluation is presented in Asayama [1]. In this review the SMT methodology was identified as the best long term approach but the need for test data precluded its near term implementation. Asayama and Jetter [2] is a summary of the more comprehensive report by Asayama [1] with a summary of the SMT approach presented by Jetter [3].
In this paper, the previously documented development of the SMT approach and applicable restrictions are discussed and reviewed; the design of the SMT specimen, measurement issues and constraints are presented; the test apparatus and measurement system is described; initial test results and their application to a prototypic design curve are presented; and further testing and analysis for ASME Code incorporation are discussed.
FEM Analysis on Pressure Vessel Components Containing LTAs Against Seismic Load Using Combined Non-Linear Isotropic/Kinematic Hardening Model
Authors: Zhou Runze , Kojima Ikuo , Kaida Takuyo , Tsuji Hirokazu 
Published: January 2014

Fitness-for-service (FFS) assessments are quantitative engineering evaluations that perform to demonstrate the integrity of an in-service component that may contain a flaw or damage [1]. It can be used to make run-repair-replace decisions to help determine if pressured equipment containing flaw that have been identified by inspection can continue to operate safety for some period of time.
This paper provides a FFS assessment on carbon steel pipe which contained a LTA (Local Thin Area) against seismic load by FEM (Finite Element Method) analysis. ABAQUS Ver. 6.10, which has the combined isotropic / kinematic hardening model [2], is used to simulate the LTA contained carbon steel pipe against seismic load. Material parameters in the hardening model are identified by a symmetric strain cycle experiment based on ASTM E606. Isotropic hardening component is introduced by specifying the equivalent stress defining the size of the yield surface, as a tabular function of the equivalent plastic strain. Kinematic hardening component is obtained from the stabilized cycle of a specimen that is subjected to symmetric stain cycles.
The authors introduced the way how to calibrate the material parameters of combined isotropic / kinematic hardening model. Then the authors calculated up to 100 cycles on carbon steel pipe which contained a Local Thin Area against seismic load at 300 degrees centigrade. The results comparison between FEM analysis and experiment shows that stress-strain hysteresis loop tendency and number of cycles to failure are predicted accurately.
European Project on Structural Integrity STYLE: Project Status
Authors: Keim Elisabeth , Nicak Tomas 
Published: January 2014

The safety and reliability of all systems has to be maintained throughout the lifetime of a nuclear power plant. Continuous R&D work is needed in targeted areas to meet the challenges of long term operation of existing designs and for the GEN-III designs. A special focus is placed on reactor coolant pressure boundary (RCPB) components, because its integrity and functionality from the time of first operation until end of life is required to ensure plant safety.
The overall objective of STYLE is to assess, optimize and develop the use of advanced tools for the structural integrity assessment of RCPB components relevant to ageing and life time management and to support the integration of the knowledge created in the project into mainstream nuclear industry assessment codes.
The project concept is based on carefully selected research topics, which thematically cover the complex multidisciplinary character of structural assessment of RCPB components. The prioritization of the work reflects the needs of industrial end-users and assessment of currently available techniques and data at European and international level.
This paper describes the current status of the project STYLE and summarizes its main results achieved up to date (Feb 2013).
The project is coordinated by AREVA GmbH with 20 partner organizations from Europe, one collaborator from USA and one collaborator from Russia:
AREVA GmbH,
Germany (coordination, WP2 leader)
AREVA SAS, France
Bay Zoltan, Hungary
CEA, France (WP1 leader)
EDF, France
EDF Energy Ltd., UK (WP7 leader)
EK, Hungary
IdS, France
INR, Romania
IWM, Germany
JRC, Netherlands (WP4 leader)
NRI, Czech Republic
NRG, Netherlands
SCK-CEN, Belgium
AMEC, UK (WP3 and WP5 leader)
University of Bristol, UK
University of Manchester, UK
Tecnatom, Spain
Vattenfall, Sweden (WP6 leader)
VTT, Finland
ORNL, USA
NIKIET, Russia
Performance Study of the Simplified Theory of Plastic Zones for the Fatigue Check
Authors: Hübel Hartwig , Willuweit Adrian , Rudolph Jürgen , Ziegler Rainer , Lang Hermann , Rother Klemens , Deller Simon 
Published: January 2014

As elastic-plastic fatigue analyses are still time consuming the simplified elastic-plastic analysis (e.g. ASME Section III, NB 3228.5, the French RCC-M code, paragraphs B 3234.3, B 3234.5 and B3234.6 and the German KTA rule 3201.2, paragraph 7.8.4) is often applied. Besides linearly elastic analyses and factorial plasticity correction (Ke-factors) direct methods are an option. In fact, calculation effort and accuracy of results are growing in the following graded scheme: a) linearly elastic analysis along with Ke correction, b) direct methods for the determination of stabilized elastic-plastic strain ranges and c) incremental elastic-plastic methods for the determination of stabilized elastic-plastic strain ranges.
The paper concentrates on option b) by substantiating the practical applicability of the simplified theory of plastic zones STPZ (based on Zarka’s method). Application relevant aspects are particularly addressed. Furthermore, the applicability of the STPZ for arbitrary load time histories in connection with an appropriate cycle counting method is discussed.
Note, that the STPZ is applicable both for the determination of (fatigue relevant) elastic-plastic strain ranges and (ratcheting relevant) locally accumulated strains. This paper concentrates on the performance of the method in terms of the determination of elastic-plastic strain ranges and fatigue usage factors. The additional performance in terms of locally accumulated strains and ratcheting will be discussed in a future publication.
Toughness Behavior of Through-Wall Cracks in Dissimilar Metal Welds
Authors: Rudland D. , Lukes R. , Shim D.-J. , Kalyanam S. 
Published: January 2014

Over the years, J-estimation scheme procedures have been develop to predict the load-carrying capacity of through-wall cracks in nuclear grade piping materials. These procedures employ analytical or numerical procedures coupled with the fracture toughness of the material to predict the pipe response. For cracks in welds, the behavior has been shown to be related to the toughness of the weld and strength of the typically lower-strength base metal. However, with the advent of primary water stress corrosion cracking (PWSCC), flaws in dissimilar metal (DM) welds have occurred. These welds consist of a nickel-based weld joining stainless steel and carbon steel base metals.
Prior research has demonstrated that crack-driving force for through-wall circumferential cracks in DM welds is highly influenced by both the stainless steel and carbon steel base metals, and is related to the axial position of the flaw within the weld. This effect brings into question the accuracy of typical J-estimation scheme procedures for calculation of load carrying capacity for circumferential through-wall flaws in DM welds. In addition, it is unknown if the apparent toughness of the cracked pipe is also affected by the position of the crack in the weld.
Work is currently underway, sponsored by the NRC Office of Nuclear Regulatory Research, to investigate the behavior of through-wall and complex cracks in DM welds. In a prior paper, a series of full-scale pipe bend and laboratory-sized fracture experiments were documented. Initial analyses of those test results suggest that typical J-estimation scheme procedures could be used to predict the response if the weld toughness from a compact tension specimen and the appropriate material strength was used. In this paper, the fracture toughness from the DM weld is estimated from the pipe experiments using an η-factor solution and numerical techniques and these results are compared to the compact tension results. The results from this paper add insight into the effect of crack size and location within the DM weld on the apparent pipe toughness for through-wall cracks in DM welds.
Effect of Surface Finish and Loading Conditions on the Low Cycle Fatigue Life of Stainless Steel Welded Piping in PWR Environment
Authors: Fukuta Yuichi , Nomura Yuichiro , Asada Seiji 
Published: January 2014

NUREG/CR-6909 of USA and JSME of Japan proposed new rules for evaluating environmental effects in fatigue analyses of reactors components. These rules were established from a lot of fatigue data with polished specimens under simple loading condition. The effects of surface finish or complex loading condition were reported in some papers, but these data were obtained with the simple shaped specimens.
In order to evaluate the effects of surface finish and loading condition and to confirm the applicability of the proposed rules to actual components, Low Cycle Fatigue tests are performed in PWR environment with the specimens cut from 316 austenitic stainless steel welded piping. The pipes are machined to have three levels of surface finish condition and the load pattern simulating the thermal stress is applied to specimens.
In this study, the effect of surface finish on fatigue life is included to be small for 316 austenitic stainless steel welded piping. Considering the insensitive region in the current evaluation rule, predicted accuracy is increased and possibility of improving the current rule is indicated.
Development of Seismic Design Method for Free Standing Rack
Authors: Iwasaki Akihisa , Nekomoto Yoshitsugu , Morita Hideyuki , Taniguchi Katsuhiko , Okuno Daisaku , Matsuoka Toshihiro , Chigusa Naoki 
Published: January 2014

For high earthquake resistance and ease of installation, free standing racks which are not anchored to the pool floor or walls has been adopted in many countries.
Under the earthquake, the response of the free standing rack is highly nonlinear and involves a complex combination of motions (sliding, rocking, twisting, and turning) and impacts between the fuel assemblies and the fuel cell walls, rack-to-rack, and the pit floor and the rack pedestals. To obtain an accurate simulation of the free standing rack, the seismic analysis requires careful considerations of these complex phenomena (sliding, rocking, twisting, and turning), fluid coupling effects and frictional effects.
The important evaluation items while applying the free standing rack to the actual nuclear plants are maximum sliding displacement of the rack, maximum rocking displacement and maximum leg load under earthquake. When the sliding displacement increases, the rack may collide against the spent fuel pool wall. In addition, the free standing rack should not exhibit tilt sufficient to cause to the rack to overturn. The vibration tests were conducted in order to predict the rack behavior under earthquake, and the analysis method was validated by comparison to tests results. Furthermore, we developed the seismic design method to obtain the margin of safety for free standing rack.
Benchmark on Residual Stress Modeling in Fracture Mechanics Assessment
Authors: Marie S. , Deschanels H. , Chapuliot S. , Le Delliou P. 
Published: January 2014

In the frame of development in analytical defect assessment methods for the RSE-M and RCC-MRx codes, new work on the consideration of residual stresses is initiated by AREVA, CEA and EDF. The first step of this work is the realization of a database of F.E. reference cases.
To validate assumptions and develop a good practice guideline for the consideration of residual stresses in finite element calculations, a benchmark between AREVA, CEA and EDF is going-on. A first application presented in this paper focuses on the analysis of the crack initiation of aged duplex stainless steel pipes submitted to an increasing pressure loading. Residual stresses are related to pipe fabrication process and act as shell bending condition. Two tests were performed: the first with an internal longitudinal semi-elliptical crack and the second with an external crack.
The analysis first focuses on the ability to accurately estimate the measured pressure at the crack initiation of the two tests. For that purpose, the comparison of results obtained with different methods of taking into account the residual stresses (i.e. thermal fields or initial strain field). It then validates post-treatment procedures for J or G determination, and finally compares of the results obtained by the different partners.
It is then shown that the numerical models can integrate properly the impact of residual stresses on the crack initiation pressure. Then, an excellent agreement is obtained between the different numerical evaluations of G provided by the participants to the benchmark so that best practice and reference F.E. solutions for residual stresses consideration can be provided based on that work.
Evaluation of the Stratification Loads With the EDF Fatigue Assessment Device
Authors: Naudin Claire , Vidard Stéphane 
Published: January 2014

A fatigue assessment device, Fatiguemètre, has been developed by EDF especially for sensitive zones of components of French PWR NPP. The main objective of this device is the evaluation of a realistic usage factor (damage criterion) by using operating data. Two requirements are to use as less specific transducers as possible and simplified thermomechanical methods for the calculation of stress variation. Some monitoring devices had nevertheless been necessary to get correlations between in service data, for instance flow rate and thermal stratification distribution. This instrumentation, called a stratimeter, consists of a ring of thermocouples installed around a section of a pipe.
The present studies were carried out on stabilized thermal stratification states and also on transients of different rates. These input data are always representative of the operating and design transient occurring on the FWL next to the connection with the steam generator. The first use of the Fatiguemètre device revealed the need of optimization on some thermomechanical methods. Investigating steady-state (stabilized) or slow enough transients of temperature stratifications, it was found that it is possible to calculate sufficiently accurate stresses without the use of any stress intensification factor, when applying temperatures from outer wall measurement as mean wall temperatures. The new discretization of Duhamel formula gives a satisfying evaluation of the local stratification stress value.
Crack Initiation Under Equibiaxial Fatigue, Development of a Particular Equibiaxial Fatigue Device
Authors: Bradaï S. , Gourdin C. , Courtin S. , Leroux J. C. , Gardin C. 
Published: January 2014

Fatigue lifetime assessment is essential in the design of structures. Under-estimated predictions may result in unnecessary in service inspections. Conversely, over-estimated predictions may have serious consequences on the integrity of structures.
In some nuclear power plant components, the fatigue loading may be equi-biaxial because of thermal fatigue. So the potential impact of multiaxial loading on the fatigue life of components is a major concern. Meanwhile, few experimental data on austenitic stainless steels is available. It is essential to improve the fatigue assessment methodologies to take into account the potential equi-biaxial fatigue damage. For this reason, a new experimental data must be obtained on the considered material with a strain tensor in equi-biaxial tension.
The aim of this paper is to present a new device “FABIME2” developed in the LISN in collaboration with EDF and AREVA. This new device allows accurate quantification of the effects of both equi-biaxial strain state as well as structure (such as mean stress) on the fatigue life. A Finite Element Modeling is also performed in order to obtain a precise description of the strain state in the specimen.
A Novel Image Processing Method for ARCMAC Point to Point Optical Strain Measurement
Authors: Yang Haoliang , Davies Catrin Mair , Hooper Paul , Morris Andy , Dear John 
Published: January 2014

The remaining life of high pressure steam pipes in power stations is heavily dependent upon material creep rates. Monitoring strain in these pipes is difficult due to demanding operational conditions and has resulted in the development of a rugged optical strain gauge system by E.ON UK. The E.ON UK auto-reference creep management and control (ARCMAC) gauge is a point-to-point biaxial creep strain measurement technique. Room temperature validation of the gauge was done using a UK National Physical Laboratory (NPL) extensometer calibration rig (ECR). These gauges have been successfully installed and measurements have been acquired on high temperature (∼600 °C) low-alloy ferritic steel power plant piping.
In conjunction with the ARCMAC gauges, research has been ongoing to seek effective methods to process the corresponding ARCMAC images. This paper describes a novel image processing method for the analysis of ARCMAC images. This method processes ARCMAC images with high efficiency and accuracy even if images were taken in demanding environmental conditions. This novel image processing method has been developed into a standalone software program named ARCMAC Assistant to assist both experiment and field work. Experiments involving calibration test work and in-situ creep tests have been used to validate its accuracy.