bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of the Effect of Notch Bluntness on Hydrogen Embrittlement and Fracture Behavior Using FE Analyses
Authors: Jeon Jun-Young , Larrosa Nicolas O. , Oh Young-Ryun , Kim Yun-Jae , Ainsworth Robert A.
Published: November 2015

This paper introduces a method to characterize the effect of notch bluntness on hydrogen embrittlement for high strength structural steel, FeE 690T, C(T) specimens. Hydrogen concentration depending on notch radius is assessed via finite element (FE) hydrogen diffusion analysis already developed and validated by the authors. Reduction in fracture toughness, KIC or JIC, due to hydrogen embrittlement is evaluated by means of a coupled hydrogen diffusion-ductile damage analysis. The ductile damage simulation used in this study is based on the model known as ‘stress-modified fracture strain model’. Tensile properties and fracture strains are modified according to the level of hydrogen concentration in the simulation and its effect on the fracture behavior of the specimen is simulated for different notch radii.
Push Probe Method for Installing Corrosion Smart Monitoring Test Stations and Collecting Soil Samples on In-Service Pipelines at Depths Up to Forty Feet at Nuclear Power Plants
Authors: Lupia Greg , Darois Matt , Kleinfelder Hank
Published: November 2015

Innovative Method for Installing Pipe Depth Smart Test Stations at Exelon Nuclear Generation Stations to Quantify Corrosion Rates, Evaluate Cathodic Protection Effectiveness, Quantify Corrosion Potentials and Perform Subsurface Soils Analysis to Support Aging Management Plans and Reasonable Assurance Commitments on In-Service Buried and Underground Pipe and Tanks

For several decades ANSI and NACE direct assessment (DA) standards for monitoring cathodic protection and coating quality (SP0502) have been relied upon by pipeline operators and regulators to accurately monitor the impact of corrosion on transmission pipelines. These same standards have been proven far less useful when deployed in nuclear power plant subsurface environments.

In order to meet regulatory and industry commitments the challenge has been to develop a cost effective method to accurately monitor nuclear plants’ buried pipe. The in-scope pipe is comprised of a dense complex of multiple systems in close proximity at depths sometimes exceeding 30-ft. Most nuclear plants have been in service for over 30 years and rely on original buried pipe systems to perform as designed. These systems are manufactured using various metals, which are bonded together to reduce electrical step and touch potential hazards. Each of these factors reduce the confidence factor of DA, but combined they make the procedure even less effective.

Smart Monitoring Test Stations can be installed without excavation at depths of up to forty feet directly into the subject pipeline local environment. This provides access to critical condition and assessment information that was previously unavailable. Smart test stations have been designed with the following components: two Electrical Resistance Probes (ER), two CP coupons and a stationary reference electrode.

This paper will describe the planning and obstacles encountered during the installation, operation and interpretation of data from recent experiences related to the installation of test stations at Exelon Nuclear Generating Stations. We will describe the process from planning to successful completion including:

• Smart Monitoring Test Station features and function

• Value of precise location insertion of probes

• Digitizing plant buried and underground pipe and tanks

• Smart monitoring test station site location selection

• Push probe method to capture soil samples

• Analyzing and interpreting soil samples

• Evaluating potential impacts from groundwater

• Push probe method of installing smart test stations at or near pipe depth

• Monitoring data from test stations

• Application of information to support AMP and NEI commitments
Study on LTA Measurement for FFS Assessment
Authors: Tahara Takayasu , Kaida Takuyo , Niimura Minoru , Sakai Shinsuke
Published: November 2015

FFS assessment technologies for pressure equipment have been studied and standardized in recent 15 years in Japan. FFS assessment of local thin area, LTA, is the most frequently used in process industries. However reliability of thickness measurement of LTA and influence to FFS assessment has not been studied much in the past.

Uncertainty of thickness measurements and Remaining Strength Factor, RSF, were investigated on Round Robin Testing using manual UT and additional new technology such as flexi-alley UT and 3D LED system for LTA in pipes, It is recommended to use suitable combination of Manual or mechanized UT and 3D LTA measurement system in case of assessment of critical flaws and decision making for repair and replacement of pressure equipment.
Qualification of Temper Bead Welding by an Alternative Hardness Testing Approach
Authors: McCracken Steven L. , Sutton Benjamin
Published: November 2015

In 2004, ASME Section IX added maximum hardness essential variables for temper bead procedure qualification when impact testing is not specified or required by the applicable book section. The assumption with specifying a maximum hardness criterion is that high hardness after temper bead welding indicates inadequate tempering. As discussed in PVP2013-97793 [2], imposing a maximum hardness criterion for temper bead qualification can actually lead to acceptance of a heat affected zone (HAZ) microstructure with less than optimum impact properties. In fact, depending on the weld HAZ microstructure the impact properties can vary widely from very low to very high at the same hardness. This paper describes an alternative hardness test protocol for temper bead procedure qualification. Rather than using a single maximum hardness acceptance threshold, this new test protocol characterizes the base material response to temper bead welding by determining the maximum achievable hardness with a bead-on-plate test and with a hardness calculation. Research shows that a high hardness in the HAZ prior to depositing the tempering weld layers provides the optimum microstructure for achieving desired HAZ impact properties. With proper tempering the HAZ hardness is reduced below the maximum achievable hardness. Temper bead procedure acceptance is thus determined by the drop in HAZ hardness after depositing the temper bead weld layers. Application of this new hardness test protocol for temper bead qualification is proposed as an alternative to a single maximum hardness acceptance criterion.
Geometrical Comparison of Numerical Models Used in the Design and Validation of Mechanically Rolled Tube-Tubesheet Joints
Authors: Madsen Søren Bøgelund , Ibsen Claus Hessler , Gervang Bo , Kristensen Anders Schmidt
Published: November 2015

The focus of this paper is the validation and comparison of simplified numerical models of the mechanical rolling process used in tube to tubesheet joints. The investigated models is an axisymmetric model and planar models with plane strain and stress. There are different pros and cons for the different simplified models and therefore they are compared to an experiment where all geometries are measured before and after expansion. This comparison gives an insight into when the different models are valid. The models investigated is an axisymmetric model, a simple 2D expansion model with both plane strain and stress assumptions. Therefore, it is desirable to investigate how close these simplified models can predict the geometry changes after expansion measured in the experiment. The conclusion of the paper is that a planer model with plane strain is the best model at predicting the actual deformation after expansion.
Elevated Temperature Lap Shear Testing of a Carbon Fiber Epoxy Composite Repair System
Authors: Hawkins Amanda P. , Johnson Bradford H.
Published: November 2015

Thermoplastic matrix materials will lose lap shear strength — among other properties — as they approach their glass transition temperature. The lap shear properties of these materials should be characterized to account for any change in temperature when designing composite repairs for leaking pipes. Not properly accounting for any decrease in lap shear strength at higher temperatures could cause the repair to be much shorter axially than required by the ASME PCC2 Article 4.1 standard, resulting in a potentially compromised repair. The results of this study showed that the lap shear strength of these two polymeric materials, a two part epoxy and cyanate ester, can decrease with increasing temperature. Also, this study confirms that epoxy bonds better to surfaces with a higher surface roughness, which is especially important in pipe repair applications with through wall defects.
Application of Torsion Ce Factor for Piping Non-Planar Through-Wall Flaws
Authors: Hoang Phuong H.
Published: November 2015

Solution for multi-axis loading on piping non-planar flaws has been studied by many authors (Hoang 2010, 2011), (Kunio 2012, 2014), (Li, 2010, 2012) and ( Bezensek, 2010) to provide a technical basis for an equivalent moment in applications of ASME Section XI, Appendix C limit load approach for pipe flaw evaluation. The equivalent moment is defined as the square root of the sum of the squares (SRSS) of bending moment and torsion with a multiplier of Ce. It has been shown that Ce=1 is applicable for piping with crack-like planar flaws and for part-through-wall non-planar flaws subjected to some limitations. However, the Ce factor for through-wall non-planar flaws has not been investigated. Since Code Case 513-3 allows the use of Section XI, Appendix C procedure for non-planar through-wall flaws, the Ce factor is studied in this paper to support the applications with torsion loading.
Basis of the Upcoming Changes to Piping Seismic Design Rules in the ASME BPVC Section III, Division 1, Article NB-3200
Authors: Adams Timothy M.
Published: November 2015

When the piping seismic design rules of the ASME Boiler and Pressure Vessel Code, Section III, Division 1 Subsections NB, NC, and ND were updated in 1994 a strain based criterion was incorporated in Article NB-3200. Due to objections to this criterion by the USNRC they were subsequently removed and replaced by guidance which stated that for Article NB-3200 for Service Level C and D reversing dynamic loads use the simplified design rules of Article NB-3600. The use of simplified Article NB-3600 rules in the NB-3200 design by analysis Article is inconsistent with the philosophy of NB-3200 and precludes the analyst from using detailed analysis methods for piping for Service Level C and D reversing dynamic loads. In 2012 an effort was undertaken to develop a more detailed design by analysis criteria for reversing dynamic loads. This paper provides the background and basis for changes that are anticipated to be implemented in the near future in the ASME Boiler and Pressure Vessel Code, Section III, Division 1 for the design by analysis rules of Article NB-3200 for reversing dynamic loads in piping systems.
On Material Qualification and Strength Design for Hydrogen Service
Authors: Yamabe Junichiro , Matsunaga Hisao , Furuya Yoshiyuki , Matsuoka Saburo
Published: November 2015

To clarify the usefulness of the safety factor multiplier method for hydrogen components given in the CHMC1-2014 standard, we performed slow-strain-rate tensile and fatigue testing by using smooth and notched specimens in air and in high-pressure hydrogen gas. We also conducted fatigue-crack growth tests by using compact tension specimens in air and in hydrogen gas. Testing of notched specimens sampled from a Cr–Mo steel gave a safety factor multiplier of 3.0. This value agreed well with that predicted by crack growth analysis taking into account hydrogen-enhanced fatigue-crack growth. The safety factor multipliers of types 304, 316, and 316L austenitic stainless steels were predicted to be 2.0, 1.6, and 1.3, respectively, from their fatigue-crack growth behaviors. The safety factor based on the safety factor multiplier method seems to be overly conservative for the various steels in high-pressure hydrogen gas service. We therefore propose a new and promising design method for specific component applications that is based on design by rule and design by analysis. The importance of operational histories of components for hydrogen service is introduced to permit the precise prediction of their fatigue lives.
Low-Velocity Impact Analysis of a Stiffened Composite Panel
Authors: Akula Venkata M. K.
Published: November 2015

The layered architecture of composite material allows for designing light-weight structural components. However, one of the challenges associated with composite structures is design and analysis considering impact damage. Although the damage associated with high-velocity impact events is often readily observed in a structure, by loss of material, for example, low-velocity impact damage is not always visible. However, low-velocity impact damage can undermine the strength capacity of a composite component. To ensure the structural integrity of components, predicting the residual strength after impact damage is critical.

In this paper, a methodology for analysis of low-velocity impact on a curved composite panel is discussed. First, impact analysis of the panel utilizing Abaqus\Explicit is presented. A metallic projectile is utilized to simulate a tool drop event. Thereafter, a simulation technique for predicting the residual strength of the panel is discussed. The residual strength is measured in terms of collapse load when the panel is subjected to axial compression. Finally, parameter sensitivity analysis is performed to understand the influence of the various design parameters on the residual strength of the component after impact. This procedure requires automating the entire simulation workflow. The results of the simulation are presented along with the important observations.
Study on Gradual Change of Corrosion Behaviors in 13MnNiMoR Steel Weld Joint Serviced in EO Reactor
Authors: Ge Zhiqiang , Geng Luyang , Gong Jianming , Jiang Yong , Tang Jianqun
Published: November 2015

This paper will focus on the gradual change of corrosion behaviors among different zone metal of 13MnNiMoR steel weld joint in the EO reactor service environment. Metallographic analysis and electrochemical corrosion tests in boiler water have been carried out on cylindrical specimens, taken from the 13MnNiMoR steel welded joints at the direction across the weld. Metallographic structures, values of linear polarization resistance (Rp) and potentiodynamic polarization curves on sections normal to the axis of the specimens have been obtained. The results showed that the Rp values and potentiodynamic polarization curves of the weld joint were significantly varied with the microstructure among different zones. Results indicated that the overheating zone in HAZ shows the minimum value of Rp and the maximum value of corrosion current density (icorr), which make it the weakest part of the joint from a corrosion stand point.
Nonlinear FEA of a Corroded Pipe
Authors: Akula Venkata M. K.
Published: November 2015

Analysis of pipelines subjected to corrosion is critical to ensure their integrity and safe operation. Although regulatory codes such as ASME, API, etc. can provide guidance in determining the fitness of a pipeline, often finite element analysis is needed to more accurately predict the structural response. In this paper, we present the techniques that could be used for performing buckling analysis of a pipe with a surface flaw. Several procedures, available in Abaqus, such as the nonlinear Newton-Raphson solver, the implicit dynamics solver, etc. are discussed in the context of predicting the collapse load. The assumptions associated with the use of each solver are presented along with a discussion on their predictive capabilities. Thereafter, parametric sensitivity analysis to study the influence of the design parameters on the collapse load is discussed. The sensitivity analysis requires automating the entire simulation workflow, including the flaw geometry, for predicting the collapse load.
Further Comments on Validation Approaches for Weld Residual Stress Simulation
Authors: Tran Minh N. , Hill Michael R. , Olson Mitchell D.
Published: November 2015

Tensile weld residual stress (WRS) in the presence of primary water has been identified as a main driver for stress corrosion cracking in dissimilar metal welds found in the cooling circuit of pressurized water reactors. Thus, WRS data are needed to support plant management decisions, and so are of interest to a broad range of stakeholders in pressure vessel technology. In an effort to validate predictive WRS models and quantify modeling uncertainty, the U.S. Nuclear Regulatory Commission (NRC) and the Electric Power Research Institute (EPRI) have cooperatively organized a research program on WRS. This paper is a follow-up to earlier work, which described a series of WRS data analysis methods that provide a range of figures of merit, from simple (e.g., root mean square difference from a benchmark) to complex (e.g., comparison of predicted crack growth behavior), that can be used to judge WRS data quality. The present work applies those methods to assess model outputs developed during the second NRC/EPRI international round robin study (Phase 2b) on WRS modeling. The results of exercising the data analysis methods are presented, and compared to results obtained from an analysis of data from the previous round robin (Phase 2a).
An Analytical Interpretation of Welding Linear Heat Input for 2D Residual Stress Models
Authors: Song Shaopin , Pei Xianjun , Dong Pingsha
Published: November 2015

Welding residual stress simulation using finite element analysis has become increasingly common in supporting fitness-for-service assessment. Two dimensional (2D) cross-section models, such as using generalized plane strain assumptions for linear welds in plate structures and axisymmetric assumptions for piping and vessel girth welds are typically used due to their computational efficiency and simplicity in data reduction process, especially for performing a large amount of parametric analyses. However, there seem no consistent procedures in place for translating actual weld linear heat input used in practice to a 2D cross-section model in which heat loss in welding travel direction is unaccounted for, often resulting in overheating to a significant degree if actual welding heat input is used.

This paper starts with the introduction of a two-part analytical linear heat input representation for a simplified 2D weld residual stress modeling procedure in which weld metal is deposited at a preset temperature such as melting with a hold time. The first part is based on a simple thermodynamics concept, which describes the heat required for elevating a weld pass from room temperature to deposition temperature. The second part is based on an equivalent transient heat transfer solution that measures the amount of heat needed to sustain deposit temperature during hold time. With this proposed method, linear heat input involved in a 2D residual stress model can be inferred for relating to actual welding conditions, typically specified in terms of current, voltage, and welding speed. By the same token, for a given set of welding parameters, welding heat flow modeling procedure involved in a 2D FE residual stress model can be consistently defined in terms of deposit temperature and hold time. A number of validation case studies are presented and the results have showed that the proposed procedure provides an effective means for inter-relating actual welding linear heat input and heat content associated with 2D residual stress models.
Remaining Fatigue Life Time Assessment of Welded and Braced Side Branches
Authors: Pereboom Hajo , Pijpers Richard , van Beek Pieter , Macdonald Kenneth
Published: November 2015

High cycle fatigue failure is likely to occur when a rather undamped offshore installation is operated over a long period of time. Especially welded parts are vulnerable to fluctuating stress ranges, if the structural components, such as the small bore side branches, are loaded in resonance. In particular, the welded connections at e.g. tie-in points can be critical. Therefore, it is important to know what the current status of existing welded connections is and how long they can still be operated at any specific operating condition without failure.

This paper describes an advanced fatigue assessment method to determine the cumulative damage in the critical parts of the system. The method is developed for industrial applications where the available information is limited. The method comprises of a mechanical analysis and a fatigue assessment based on a fracture mechanics crack growth model. The method enables determination of inspection intervals and at the same time layout optimization for a long term safe operation. This paper pays special attention to complex, braced small bore side branches. Standard fatigue stress assessment methods can be conservative for the fatigue assessment of high frequent stress ranges with relatively low stress ranges. The current paper shows the effect of the fracture mechanics procedure for an example of a braced side branch connected to the main piping: both a fracture mechanics model and a detailed 3D FE model are made. With these models, the hot spot stress in the welds is evaluated and tailor-made S-N-curves are derived. With information of the operating history, the cumulative damage is determined for the weld detail. This knowledge on the current damage status is crucial for future operations.
Benchmark for the Calculation of Quasi-Laminar Elliptical Cracks Interaction Under Bi-Axial Loading
Authors: Dulieu Pierre , Lacroix Valéry , Shim Do Jun , Brust Frederick (Bud)
Published: November 2015

In the frame of the Structural Integrity demonstration of the Doel 3 and Tihange 2 RPVs flawed with quasi-laminar cracks, alternative proximity rules based on 3D eXtended Finite Element Method (X-FEM) calculations have been developed by Tractebel Engineering. The calculations have been performed with the X-FEM software Morfeo Crack. This software uses the Level-Sets method allowing a very straightforward cracks modelling.

A large part of the development of these proximity rules for quasi-laminar flaws has been dedicated to the validation of the models and the calculations. This validation has been done through a benchmark with Engineering Mechanics Corporation of Columbus (Emc2). This company uses:

• The Finite Element Alternating Method (FEAM) for calculating stress intensity factors through the FRAC@ALT program. The FEAM is a state-of-the-art method for obtaining stress intensity factors for three-dimensional surface and embedded crack problems.

• The X-FEM functionality as implemented in Abaqus software.

The benchmark consists of the Stress Intensity Factor calculation of interacting quasi-laminar flaws and of the interaction factor assessment as well.
Acoustic Vibration Induced Fatigue in Pipe Joints
Authors: Prakash Ajay , Diwakar Philip , Lin Dan , Deane Paul , Liu Yuqing , Jaouhari Matt
Published: November 2015

High acoustic energy has the potential to cause severe acoustic induced vibration (AIV) that can lead to fatigue failure at high stress concentration locations (discontinuities) in a piping system. AIV at pipe junctions (Lateral, Tee, and Wye) and welded support attachments (trunnions and shoes) is evaluated using Finite Element Analysis. At different size pipe junctions, branch and header pipe shells may be subjected to different sound pressure. Also, inertia associated with different wall thickness(s) can lead to very different dynamic response of the two shell walls. The effect of these differences on AIV response is analyzed. Resulting response for different junction reinforcement designs is evaluated and compared to an unreinforced ‘stub-on’ configuration to assess the designs.
Influence of PWR Environment on Fatigue Crack Initiation and Growth of Type 316 Stainless Steel
Authors: Fujikawa Ryosuke , Abe Shigeki , Nakamura Takao , Kamaya Masayuki
Published: November 2015

This study was aimed at investigating the role of crack initiation and growth rate on the fatigue life reduction by environmental effect. First, crack length and the number of cracks were observed on the inner surface of specimens after fatigue test in PWR environment and air. Next, incubation time was deduced by inverse analysis. Third, statistical crack initiation and growth behavior was simulated by a Monte Carlo model. The influence of multiple crack interaction and coalescence to the fatigue life were discussed. It was revealed that environmental effect enhanced crack initiation and accelerated crack growth. Moreover, coalescence of cracks was estimated to influence fatigue life of 316 stainless steel in PWR environment.
Dependence of Bonding Temperature Conditions on Metal Thickness Effects in Bonded Dissimilar Materials
Authors: Tateno Masayoshi , Yokoi Eiichiro
Published: November 2015

This study provides information on the dependence of bonding temperature conditions on metal thickness effects in bonded dissimilar materials as a composite material system. Effects of metal thickness on the bonding strength were confirmed each bonding temperature condition by using silicon-nitride and nickel to confirm for each joint manufactured by a bonding method, two stages bonding process. This process used in this experiment consists of two stages, first bonding process as the ceramic is bonded to thin layer metal at high temperature, and secondary process as thick metal is bonded to the thin metal layer of the joint at lower temperature than first stage’s one. Bonding tensile strength of the joint specimen was evaluated experimentally. The bonding strength was dominated by the residual stress near the edge of the interface on ceramic side. The maximum bonding strength appears at optimum metal thickness. It shows that the optimum metal thickness depends on the first temperature condition. Reduction of the residual stress was considered based on the experimental and numerical results. Two stages bonding process can be applied for high strength bonded dissimilar materials as useful engineering application by setting optimum metal thickness each bonding temperature condition.
Temperature Effects on Piezoelectric Wafer Active Sensors
Authors: Ma Linlin , Sun Xiaoyi , Lin Bin , Yu Lingyu
Published: November 2015

This paper discusses the temperature effects of using piezoelectric wafer active sensors (PWAS) technologies for structural health monitoring (SHM) in pressure vessels and piping (PVP) applications, e.g. dry cast storage system (DCSS). The research into monitoring of DCSS health has experienced a dramatic increase following the issuance of the Blue Ribbon Commission (BRC) on America’s Nuclear Future Final Report in 2012. The interim storage of spent nuclear fuel from reactor sites has gained additional importance and urgency for resolving waste-management-related technical issues. PWAS have emerged as one of the major SHM technologies developed particularly for generating and receiving acousto-ultrasonic waves for the purpose of continuous monitoring and diagnosis. Durability and survivability of PWAS under temperature effects was first tested in experiments. The analytical model of PWAS based sensor and sensing system under temperature effects was then developed. This paper compared the analytical model and experimental results of PWAS under temperature changes. Since the environmental variability of a sensing system includes changes in both the sensors and the sensing methodology including acoustic emission (AE), guided ultrasonic waves (GUW), and electro-mechanical impedance spectroscopy (EMIS), we also performed several temperature exposure with different PWAS sensing configurations under a controlled oven. The potential of PWAS for DCSS applications has been explored. The paper ends with conclusions and suggestions for further work.
Multilayer Kinematic Hardening Model for Carbon Steel and its Application to Inelastic Analyses of an Elbow Subjected to Cyclic In-Plane Bending
Authors: Iwata Koji , Karakida Yasuhisa , Jin Chuanrong , Nakamura Hitoshi , Kasahara Naoto
Published: November 2015

Carbon steel STS410 (JIS Standard), which is widely used for high pressure piping components, exhibits cyclic hardening under repeated loading. Extreme seismic loading can cause repetitive large strains, eventually leading to the failure of components. For failure assessment of such components, inelastic analyses using cyclic plasticity constitutive models are needed. In this paper, a multilayer kinematic hardening model for cyclic plasticity, equipped with a set of standard stress-strain characteristics, is developed for STS410 under isothermal condition of various temperatures. This model can express not only the nonlinearity of stress-strain relations, but cyclic hardening of a material by introducing a generic stress-strain relation composed of a combination of monotonic and steady state cyclic stress-strain curves. Finite element large deformation elastic-plastic analyses with this model are conducted for a cyclic in-plane bending test of an elbow. The proposed constitutive model predicted well characteristic features of global deformation and local strain behaviors of the elbow.
Rousselier Parameter Calibration for Esshete Weld Metal
Authors: Arun Sutham , Sherry Andrew H. , Sheikh Mohammad , Smith Mike C.
Published: November 2015

This paper describes an investigation concerning calibration of the Rousselier ductile damage model parameters for an industrial grade weld material (Esshete 1250). Parameters such as σ1 and the mesh size (Lc) were calibrated using numerical models of tensile and fracture toughness test specimens (smooth round bar and side-grooved compact-tension (CT) types) and adopting the Rousselier damage model as a constitutive relation. The process of parameter calibration was investigated by comparing the numerical load-displacement, crack initiation and growth predictions with experimental data measured using the two test geometries. It was found that it was not possible to obtain a single set of parameters which provided a good agreement between numerical predictions and experimental behaviour for both smooth tensile bar and CT specimen due to the difference in the failure mechanism of these specimens. Therefore, experimental J-R curve data determined from unload-compliance CT laboratory specimen fracture toughness tests of Esshete weld material were used to determine the values of these two parameters. The calibration results showed that the values of σ1 affect the change of the slope of J-R curve, whereas an increase in Lc elevates the crack growth resistance. The ductile fracture behaviour of the weld material is best simulated using the value of Lc = 50 μm and σ1 = 506 MPa. A detailed description of the numerical approach and calibration steps undertaken are provided.
The Effects of Specimen Size on the Very High Cycle Fatigue Properties of FV520B-I
Authors: Zhang Ming , Wang Weiqiang , Li Aiju
Published: November 2015

The authors researched the effects of specimen size on the very high cycle fatigue properties of FV520B-I through ultrasonic fatigue testing. The test results showed that the very high cycle fatigue mechanism was not changed and the fatigue properties declined as the specimen size increased. The S-N curve moved downward and the fatigue life decreased under the same stress level maybe due to the heat effects of large specimens in tests. The fatigue strength and the fatigue life were predicted by relevant models. The prediction of fatigue strength was close to test result, and the prediction of fatigue life was less effective compared with the previous prediction of small size specimen test results.
SNF Transportation Package Response to MacArthur Maze Fire Scenario: Leak Rate Determination After Seal Failure
Authors: Adkins H. E. , Suffield S. R. , Klymyshyn N. A. , Cuta J. M. , Piotter J.
Published: November 2015

Extensive and detailed modeling of the possible effect of the MacArthur Maze fire scenario on an over-the-road spent nuclear fuel transportation package has shown that the potential consequences could include release of radioactive material due to failure of the package seals. Structural and thermal modeling of the performance of the lid closure and closure bolts show that the lid closure bolts would maintain positive clamping force throughout the fire transient scenario, such that the total release possible, even with conservative and bounding modeling assumptions, is two to three orders of magnitude below the regulatory limit for accident conditions. Typical leak rate models, such as the ANSI standard ANSI N14.5, are based on the expectation of intact seals for the package. Very little analytical work has been done to investigate leak rates from failed seals, since seal failure is, by definition, unacceptable performance in real-world applications. In order to evaluate the potential release from the SNF package subjected to the conditions of this fire scenario, an analytical modeling approach was developed to determine bounding leak rate estimates through the interface of the package closure lid and body flange. This modeling approach postulates complete loss of the O-ring seal material, and assumes only metal-to-metal contact, maintained by the clamping force of the closure bolts, as it varies due to differential thermal expansion and changing internal package pressure during the transient. This paper describes the analytical approach used to perform the leak rate modeling for the SNF package, and presents results for the limiting design basis loading of the package.
The Effect of Bolt Size on the Assembly Nut Factor
Authors: Brown Warren , Lim Tze-Yew
Published: November 2015

In a previous publication, the effect of diameter and material of the bolt and nut on Nut Factor was examined. The conclusion was that for stainless steel bolting and some anti-seize products, as the bolt diameter increased, so did the Nut Factor. Recent additional testing has revealed that this may not always be the case.

This paper presents a summary of the recent testing and draws practical conclusions regarding the need for specific Nut Factor testing and better quality control of ASTM A193 bolts and ASTM A194 nuts.
Determination of Local Tensile and Fatigue Properties With the Use of Sub-Sized Specimens
Authors: Džugan Jan , Konopik Pavel , Rund Martin , Prochazka Radek
Published: November 2015

Determination of mechanical properties with the use of sub-sized specimens is very important topic nowadays. The use of sub-sized samples can be quite wide in all cases when limited amount of the experimental material is available such as evaluation of residual life of in-service components, properties determination of developed nano-structured materials, assessment of dilatometric samples used for thermal and thermo-mechanical treatment development, local properties of weld joints and so on. Concerning this large application field it would be very useful to prepare standard for small size samples especially for most demanded material properties: tensile properties, notch impact transition temperature, fatigue properties, fracture toughness and creep. One of the widely used methods of miniature sample testing is Small Punch Test (SPT) that is used for determination of all above mentioned properties. However the main drawback of this method is need of known correlation relation between considered property and SPT for the material of interest. The correlation is needed due to different loading mode in comparison between SPT and standard test methods. Unfortunately, transferability of these correlation parameters between labs is very limited and thus each lab has to determine its own that limits the use of this method. More interest is recently paid to development of small size samples procedures using miniaturized standardized samples maintaining big advantage — the same loading mode between small sized and full sized samples. The same loading mode significantly reduces or completely removes complexity of the results transfer from small to standard size samples. The current paper is dealing with overview of various applications of small sized tensile tests and fatigue tests. Concerning tensile tests quasi static tensile test at room temperature as well as at elevated temperature are show together with results of dynamic tests and special tests of metastable supercooled austenite. The developed procedures performance is demonstrated by comparison of standard size and sub-size specimens results comparison for all tests, except supercooled austenite tests, where no standard size specimen exists.
Investigation of a Chronic Leaking Problem of a Heat Exchanger Girth Flange
Authors: van Zyl Gys
Published: November 2015

A shell-and-tube heat exchanger experiences frequent leaks from the gasket between the shell girth flange and tube sheet. The leaks manifest during start-up of the equipment and have traditionally been arrested by assembly retorque. An investigation was launched to understand the cause of recurring leaks and propose measures to eliminate the problem. A standard design review using the ASME BPVC [1] rules for bolted flanges found no concern with the design of the flanges. More detailed numerical simulation studies were performed that considered thermal conditions in addition to mechanical loads (pressure and bolt loads). The heat exchanger operation involves phase changes in the media on both the shell and tube sides (boiling/condensing) — as a result, the flanges experience rather severe thermal gradients during regular operation. These thermal gradients cause distortion of the tube sheet and girth flange and result in relaxation of the gasket compression in specific areas. This paper will provide a detailed discussion about the numerical simulation studies that were performed on the girth flange joint, as well as the modifications that were proposed to alleviate the problem.
Comparison of Ring Compression Testing to Three Point Bend Testing for Unirradiated ZIRLO Cladding
Authors: Korinko Paul S. , Sindelar Robert L. , Kesterson Ronald L.
Published: November 2015

Safe shipment and storage of nuclear reactor discharged fuel requires an understanding of how the fuel may perform under the various conditions that can be encountered. One specific focus of concern is performance during a shipment drop accident. Tests at Savannah River National Laboratory (SRNL) are being performed to characterize the properties of fuel clad relative to a mechanical accident condition such as a container drop. Unirradiated ZIRLO tubing samples have been charged with a range of hydride levels to simulate actual fuel rod levels. Samples of the hydrogen charged tubes were exposed to a radial hydride growth treatment (RHGT) consisting of heating to 400°C, applying initial hoop stresses of 90 to 170 MPa with controlled cooling and producing hydride precipitates. Initial samples have been tested using both a) ring compression test (RCT) which is shown to be sensitive to radial hydride and b) three-point bend tests which are less sensitive to radial hydride effects.

Hydrides are generated in Zirconium based fuel cladding as a result of coolant (water) oxidation of the clad, hydrogen release, and a portion of the released (nascent) hydrogen absorbed into the clad and eventually exceeding the hydrogen solubility limit. The orientation of the hydrides relative to the subsequent normal and accident strains has a significant impact on the failure susceptability. In this study the impacts of stress, temperature and hydrogen levels are evaluated in reference to the propensity for hydride reorientation from the circumferential to the radial orientation. In addition the effects of radial hydrides on the Quasi Ductile Brittle Transition Temperature (DBTT) were measured. The results suggest that a) the severity of the radial hydride impact is related to the hydrogen level-peak temperature combination (for example at a peak drying temperature of 400°C; 800 PPM hydrogen has less of an impact/ less radial hydride fraction than 200 PPM hydrogen for the same thermal history) and b) for critical strains in post drying handling, storage and accident conditions the 3 point bend strain tolerance is less affected by radial hydrides than the conventional ring compression test (the radial hydride related Quasi DBTT associated with a three point bend straining is lower (better) than that measured by the ring compression tests).
Band offsets in HfSiO4/IGZO heterojunctions
Authors: Hays David C. , Gila Brent P. , Pearton Stephen J. , Ren Fan
Published: November 2015

InGaZnO4 (IGZO) is attracting interest for transparent thin film transistors because of its excellent transport properties even in amorphous films deposited at low temperatures. The basic parameters of potential gate dielectric materials for IGZO is still lacking in many cases. The authors have measured the band offsets of sputtered HfSiO4 on IGZO using x-ray photoelectron spectroscopy and obtained the bandgaps of the materials using reflection electron energy loss spectroscopy. The effect of atmospheric exposure on the band offsets was systematically examined. Previous work has shown that both HfO2 and SiO2 have nested type I alignments on IGZO. However, the HfSiO4/IGZO system has a staggered, type II alignment, with a valence band offset of −0.43 ± 0.04 eV for samples in which all the layers were kept in vacuum or −0.27 ± 0.03 eV for samples exposed to atmosphere prior to the measurement. The conduction band offset for HfSiO4/IGZO was derived as 3.07 ± 0.31 eV for the vacuum samples from the measured bandgap of the IGZO (3.16 eV) and 3.01 ± 0.30 eV for vented samples.
Magnetic fields make waves in cuprates
Authors: Julien Marc-Henri
Published: November 2015

High magnetic fields reveal underlying electronic states in high-temperature superconductors

[Also see Report by

Gerber
et al.

]
Control of Giardiasis by Interleukin-17 in Humans and Mice—Are the Questions All Answered?
Authors: Singer Steven M.
Published: November 2015

For years, studies of the immune response to
Giardia lamblia
infection focused on the production of IgA by infected hosts and antigenic variation by the parasite to escape destruction by this IgA. A new study by Hanevik and colleagues (C. S. Saghaug, S. Sørnes, D. Peirasmaki, S. Svärd, N. Langeland, and K. Hanevik, Clin Vaccine Immunol 23:11–18, 2016,
http://dx.doi.org/10.1128/CVI.00419-15
) highlights the emerging role of interleukin-17 (IL-17) in immunity to this parasite. Along with recent studies of
Giardia
infections of animals, this work shows that IL-17 appears to be essential for the control of these infections and to be a key factor linking cellular and humoral immune responses.
Fluoroquinolones and collagen associated severe adverse events: a longitudinal cohort study
Authors: Daneman Nick , Lu Hong , Redelmeier Donald A
Published: November 2015

Objectives

Fluoroquinolone-associated tendon ruptures are a recognised complication, but other severe collagen-associated adverse events may also be possible. Our objectives were to confirm the association of fluoroquinolones and tendon rupture, to clarify the potential association of fluoroquinolones and retinal detachment, and to test for a potentially lethal association between fluoroquinolones and aortic aneurysms.

Setting

Population-based longitudinal cohort study in Ontario, Canada.

Participants

Older adults turning 65 years between April 1 1997 and March 31 2012 were followed until primary outcome, death, or end of follow-up (March 31 2014). Fluoroquinolone prescriptions were measured as a time-varying covariate, with patients considered at risk during and for 30 days following a treatment course.

Primary outcome measures

Severe collagen-associated adverse events defined as tendon ruptures, retinal detachments and aortic aneurysms diagnosed in hospital and emergency departments.

Results

Among the 1 744 360 eligible patients, 657 950 (38%) received at least one fluoroquinolone during follow-up, amounting to 22 380 515 days of treatment. The patients experienced 37 338 (2.1%) tendon ruptures, 3246 (0.2%) retinal detachments, and 18 391 (1.1%) aortic aneurysms. Severe collagen-associated adverse events were more common during fluoroquinolone treatment than control periods, including tendon ruptures (0.82 vs 0.26/100-person years, p<0.001), retinal detachments (0.03 vs 0.02/100-person-years, p=0.003) and aortic aneurysms (0.35 vs 0.13/100-person-years, p<0.001). Current fluoroquinolones were associated with an increased hazard of tendon rupture (HR 3.13, 95% CI 2.98 to 3.28; adjusted HR 2.40, 95% CI 2.24 to 2.57) and an increased hazard of aortic aneurysms (HR 2.72, 95% CI 2.53 to 2.93; adjusted HR2.24, 95% CI 2.02 to 2.49) that were substantially greater in magnitude than the association of these outcomes with amoxicillin. The hazard of retinal detachment was marginal (HR 1.28, 95% CI 0.99 to 1.65; adjusted HR 1.47, 95% CI 1.08 to 2.00) and not greater in magnitude than that observed with amoxicillin.

Conclusions

Fluoroquinolones are associated with subsequent tendon ruptures and may also contribute to aortic aneurysms.
Defining chronic cancer: patient experiences and self-management needs
Authors: Harley Clare , Pini Simon , Bartlett Yvonne Kiera , Velikova Galina
Published: November 2015

Objective

Chronic cancer is poorly defined and strategies for supporting patients during this disease phase are lacking. This research defines chronic cancer, explores patient experiences and reviews patients' support needs against those described in the 2007 Department of Health Generic Choice Model for Long-term Conditions (DoH-GCM).

Design

Semistructured interviews were audio recorded, transcribed and data explored for emergent themes. The a priori themes from DoH-GCM were applied: clinical support; self-care and self-management; supporting independence; psychological support; and social and economic factors.

Results

56 patients >12 months postdiagnosis of advanced cancer were recruited from five clinics at a Yorkshire cancer centre: breast (n=11); renal (n=11); colorectal/gastrointestinal (n=12); gynaecological (n=12); and prostate (n=10). Most patients aspired to livingnormallives. Challenges included frequent and lengthy hospital appointments, long-term symptom control and uncertainty. Only renal and prostate patients reported routine access to specialist nursing. Uptake of support services was varied and there was generally poor understanding of support pathways for non-medical problems and issues occurring when patients were not receiving active treatment. There was variation in coping strategies and ability of patients to attain a positive outlook on life.

Conclusions

For patients to do well in this cancer phase requires good self-management of symptoms plus taking an active role in accessing appropriate services as needed. Care planning at the point of transition to the chronic phase of cancer should focus on evaluating patients' needs, clarifying support pathways, increasing the profile and involvement of community services and organisations, and supporting patients and families develop effective self-management skills.