bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of antimicrobial stewardship on antimicrobial prescriptions for selected diseases of dogs in Switzerland
Authors: Lehner Claudia , Hubbuch Alina , Schmitt Kira , Schuepbach‐Regula Gertraud , Willi Barbara , Mevissen Meike , Peter Ruth , Muentener Cedric R. , Naegeli Hanspeter , Schuller Simone
Published: October 2020

Background

Antimicrobial stewardship programs (ASPs) are important tools to foster prudent antimicrobial use.

Objective

To evaluate antimicrobial prescriptions by Swiss veterinarians before and after introduction of the online ASP AntibioticScout.ch in December 2016.

Animals

Dogs presented to 2 university hospitals and 14 private practices in 2016 or 2018 for acute diarrhea (AD; n = 779), urinary tract infection (UTI; n = 505), respiratory tract infection (RTI; n = 580), or wound infection (WI; n = 341).

Methods

Retrospective study. Prescriptions of antimicrobials in 2016 and 2018 were compared and their appropriateness assessed by a justification score.

Results

The proportion of dogs prescribed antimicrobials decreased significantly between 2016 and 2018 (74% vs 59%;P < .001). The proportion of prescriptions in complete agreement with guidelines increased significantly (48% vs 60%;P < .001) and those in complete disagreement significantly decreased (38% vs 24%;P < .001) during this time. Antimicrobial prescriptions for dogs with AD were significantly correlated with the presence of hemorrhagic diarrhea in both years, but a significantly lower proportion of dogs with hemorrhagic diarrhea were unnecessarily prescribed antimicrobials in 2018 (65% vs 36%;P < .001). In private practices, in 2018 a bacterial etiology of UTI was confirmed in 16% of dogs. Prescriptions for fluoroquinolones significantly decreased (29% vs 14%;P= .002). Prescriptions for antimicrobials decreased significantly in private practices for RTI (54% vs 31%;P < .001).

Conclusion

Antimicrobials were used more prudently for the examined indications in 2018 compared to 2016. The study highlights the continued need for ASPs in veterinary medicine.
Genetic diversity and historical demography in Bellamya gastropods from the Lake Victoria ecoregion reveal early and severe population collapse
Authors: Whelan Nathan V. , Strong Ellen E.
Published: October 2020

Understanding the interplay between ecological and population genetic processes through space and time is a central goal of landscape genetics. However, most studies that place diversification dynamics in an ecological context have focused on vertebrates, leaving a significant gap in our understanding of the effects of ecosystem change on community composition and demography of invertebrates. In the East African Rift System, cichlid fishes have emerged as a powerful model system for understanding adaptive radiation (Kornfield & Smith, 2000), but few studies have examined diversification of other taxa. In this issue of Molecular Ecology, Van Bocxlaer et al. (2020) use landscape genetic approaches to model historical demography and diversification of viviparid gastropods in the Lake Victoria ecoregion. They show that while phylogeographic patterns are similar between the two, viviparids and cichlids have responded in very different ways to the climatic upheavals of the Pleistocene and that their responses have been at least partially asynchronous. Viviparids have experienced population collapse 30‐ to 50‐fold more severe than that seen in haplochromine cichlids from the region, and population declines began 100K years earlier, prior to the last glacial maximum (~15,000–18,000 years ago). Their results reveal a new facet to the profound and lasting impacts of Pleistocene climate change on the modern fauna of the Lake Victoria ecoregion and its ability to respond to current human‐mediated stressors.
A mobile sex‐determining region, male‐specific haplotypes and rearing environment influence age at maturity in Chinook salmon
Authors: McKinney Garrett J. , Nichols Krista M. , Ford Michael J.
Published: October 2020

Variation in age at maturity is an important contributor to life history and demographic variation within and among species. The optimal age at maturity can vary by sex, and the ability of each sex to evolve towards its fitness optimum depends on the genetic architecture of maturation. Using GWAS of RAD sequencing data, we show that age at maturity in Chinook salmon exhibits sex‐specific genetic architecture, with age at maturity in males influenced by large (up to 20 Mb) male‐specific haplotypes. These regions showed no such effect in females. We also provide evidence for translocation of the sex‐determining gene between two different chromosomes. This has important implications for sexually antagonistic selection, particularly that sex linkage of adaptive genes may differ within and among populations based on chromosomal location of the sex‐determining gene. Our findings will facilitate research into the genetic causes of shifting demography in Chinook salmon as well as a better understanding of sex determination in this species and Pacific salmon in general.
Environmental variables determining the distribution of an avian parasite: the case of thePhilornis torquanscomplex in South America
Authors: Cuervo P. F. , Percara A. , Monje L. , Beldomenico P. M. , Quiroga M. A.
Published: October 2020

Philornisflies are the major cause of myiasis in nestlings of Neotropical birds, being of major concern in geographically‐restricted and endangered bird species. Despite its relevance for the conservation of birds, there is little information about the environmental dimensions determiningPhilornisspp. geographical range. By using maximum entropy, we identified for the first time the macro‐environmental variables constraining the abiotic niche of theP. torquanscomplex in South America, and provided a model map of its potential distribution based on environmental suitability. We identified the minimum temperature of the coldest month as the most relevant variable, associated with the largest decrease in habitat suitability in Brazil and northern South America. Furthermore, the mean temperature of the warmest quarter limited suitability mostly along with the Andean range. In addition, humidity and moisture are influential factors in most of Argentina, northern Chile, and coastal Peru. The geographical projection suggests that environments in most of central‐eastern Argentina, and in a broad area in central Chile, are suitable for the presence of theP. torquanscomplex. Besides providing information about the ecology ofPhilornisspp., this study represents a tool for bird conservation and a reference for future work on the distribution of this genus.
Evolution and diversification of reproductive phased small interfering RNAs in Oryza species
Authors: Tian Peng , Zhang Xuemei , Xia Rui , Liu Yang , Wang Meijiao , Li Bo , Liu Tieyan , Shi Jinfeng , Wing Rod A. , Meyers Blake C. , Chen Mingsheng
Published: October 2020

In grasses, two types of phased, small interfering RNAs (phasiRNAs) are expressed largely in young, developing anthers. They are 21 or 24 nucleotides (nt) in length and are triggered by miR2118 or miR2275, respectively. However, most of their functions and activities are not fully understood.

We performed comparative genomic analysis of their source loci (PHAS) in five Oryza genomes and combined this with analysis of high‐throughput sRNA and degradome datasets. In total, we identified 8216 21‐PHAS and 626 24‐PHAS loci. Local tandem and segmental duplications mainly contributed to the expansion and supercluster distribution of the 21‐PHAS loci. Despite their relatively conserved genomic positions, PHAS sequences diverged rapidly, except for the miR2118/2275 target sites, which were under strong selection for conservation.

We found that 21‐nt phasiRNAs with a 5′‐terminal uridine (U) demonstrated cis‐cleavage at PHAS precursors, and these cis‐acting sites were also variable among close species. miR2118 could trigger phasiRNA production from its own antisense transcript and the derived phasiRNAs might reversibly regulate miR2118 precursors.

We hypothesised that successful initiation of phasiRNA biogenesis is conservatively maintained, while phasiRNA products diverged quickly and are not individually conserved. In particular, phasiRNA production is under the control of multiple reciprocal regulation mechanisms.
Understanding and predicting forest mortality in the western United States using long‐term forest inventory data and modeled hydraulic damage
Authors: Venturas Martin D. , Todd Henry N. , Trugman Anna T. , Anderegg William R. L.
Published: October 2020

Global warming is expected to exacerbate the duration and intensity of droughts in the western United States, which may lead to increased tree mortality. A prevailing proximal mechanism of drought‐induced tree mortality is hydraulic damage, but predicting tree mortality from hydraulic theory and climate data still remains a major scientific challenge.

We used forest inventory data and a plant hydraulic model (HM) to address three questions: can we capture regional patterns of drought‐induced tree mortality with HM‐predicted damage thresholds; do HM metrics improve predictions of mortality across broad spatial areas; and what are the dominant controls of forest mortality when considering stand characteristics, climate metrics, and simulated hydraulic stress?

We found that the amount of variance explained by models predicting mortality was limited (R2 median = 0.10, R2 range: 0.00–0.52). HM outputs, including hydraulic damage and carbon assimilation diagnostics, moderately improve mortality prediction across the western US compared with models using stand and climate predictors alone.

Among factors considered, metrics of stand density and tree size tended to be some of the most critical factors explaining mortality, probably highlighting the important roles of structural overshoot, stand development, and biotic agent host selection and outbreaks in mortality patterns.
A career open to the talents—Nurses’ doing and focus during the history
Authors: Falch Lisbeth Aaskov
Published: October 2020

Based on a historical and a contemporary fieldwork at a Danish hospital, this article offers a genealogical and philosophical exploration of the development of nurses’ doing and focus within a hospital setting from the 1800 s to the present day. This exploration finds that nurses’ doing has changed during history, which is reflected in their focus. Thus, nurses’ focus has developed from, what the Danish philosopher Uffe Juul Jensen refers to as a situation‐oriented, to a disease‐oriented practice, and while new values are established, the conception of care as a core value in nursing seems to have receded. This article also argues that today's nurses are doing what doctors did in the 19th century. The French philosopher Michel Foucault discusses how things repeat themselves in new ways and new contexts. The nursing profession has become ‘a career open to the talents’ where nurses with the appropriate skills and talents are able to build a career, within which they provide status, position and legitimacy. The conclusion of the article discusses the significance of this development for patients and the nursing profession.
Promoting social and environmental justice to support Indigenous partnerships in urban ecosystem restoration
Authors: Hall Monique Mae , Wehi Priscilla M. , Whaanga Hēmi , Walker Erana T. , Koia Jonni Hazeline , Wallace Kiri Joy
Published: October 2020

Urban ecological restoration typically employs western science approaches to restore degraded ecosystems. As yet, few restoration groups acknowledge the history of these degraded urban sites, despite connections, past and present, that root Indigenous Peoples (and others) in these lands. Here, we promote partnership with Indigenous communities from project inception and present two successful case studies from Aotearoa New Zealand. We specifically note that partnering and building relationships with Indigenous communities in restoration efforts require recognition of power inequalities and injustices. We consider success to include both restoration of ecological function and biodiversity and reconnection of all communities to urban ecosystems.
Aiming strategy affects performance‐related factors in biathlon standing shooting
Authors: Köykkä Miika , Ihalainen Simo , Linnamo Vesa , Ruotsalainen Keijo , Häkkinen Keijo , Laaksonen Marko S.
Published: October 2020

This study focused on investigating differences in shooting performance and performance‐related factors between two different aiming strategies (HOLD, low radial velocity during the approach 0.4‐0.2 seconds before triggering, and TIMING, high radial velocity) in biathlon standing shooting. A total of 23 biathletes fired 8 × 5 standing shots at rest (REST) and 2 × 5 shots during a race simulation (RACE). Shooting performance (hit point distance from the center of the target), aiming point trajectory and postural balance were measured from each shot. Shooting performance was similar both at REST (HOLD 33 ± 5 mm vs TIMING 38 ± 8 mm, P = .111) and in RACE (40 ± 11 mm vs 47 ± 12 mm, P = .194). Better shooting performance was related to smaller distance of the aiming point mean location (REST r = 0.93, P < .001, RACE r = 0.72, P = .018) and higher time spent within ⅔ of the distance of the hit area edge from the center 0.6‐0.0 seconds before triggering (REST r=−0.88, P = .001, RACE r=−0.73, P = .016) in HOLD, and to lower aiming point total velocity 0.6‐0.0 seconds before triggering (REST r = 0.77, P = .009, RACE r = 0.88, P = .001) and less aiming point movement 0.2‐0.0 seconds before triggering (REST r = 0.82, P = .003, RACE r = 0.72, P = .012) in TIMING. Postural balance was related to shooting performance at REST in both groups and in RACE in TIMING. Biathletes using the hold strategy should focus on stabilizing the aiming point before triggering and aiming at the center, whereas biathletes using the timing strategy benefit of decreasing the total velocity during the final approach as well as minimizing the aiming point movement right before triggering.
Detection of the HLA‐B*51:322 allele in a Russian individual
Authors: Ananeva Anastasiia , Osipova Nailia , Andryushkina Anna , Shagimardanova Elena
Published: October 2020

HLA‐B*51:322 differs from B*51:01:01:05 by one nucleotide at position 1043C > T resulting in valine at codon 324.
Fast Fracture Evaluation of Steam Generator Channel Heads Considering High Carbon Macro-Segregation
Authors: Shi Kaikai , Zhang Yixiong , Yang Yu , Zheng Bin , Xie Hai , Fu Xiaolong , Shao Xuejiao
Published: October 2020

The Fracture evaluation is important in the structural integrity analysis of nuclear equipment which is subjected to the effects of neutron irradiation. The increment of ductile and brittle transition temperature is mainly due to the neutron irradiation, thermal ageing and strain ageing. In addition to above these factors, the high carbon macro-segregation of low-alloy steels also increases the risk of fast fracture failure as the carbon positive macro-segregation will lead to the increasing transition temperature of low-alloy steels. In this work, a relationship between the carbon content and the increment of transition temperature is developed and is used to the fast fracture failure analysis of the highest carbon content region in steam generator channel head. Results show that ratio between the calculated stress intensity factor considering safety coefficient suggested by ASME design code and the critical stress intensity factor is less than one, which indicates a safe design for the highest carbon content region in steam generator channel head.
Mode I Stress Intensity Factors for Small Defects in a Large Diameter Threaded Fixing
Authors: Towse Adam
Published: October 2020

Mode I Stress Intensity Factors (SIFs) are presented at the surface and depth positions for shallow defects at the root of the male threads of an M130x4 – 6g / 6H threaded connection. The defects range between 1mm and 5mm in depth, and with an aspect ratio (a/b) between 1 (circular) and 0.1 (elongated). For the lowest a/b ratios, the defects approach the shape of an elongated constant depth defect running circumferentially. Such defects may be produced by preferential fatigue crack growth in the circumferential direction, fatigue crack initiation at the root or as a result of thread forming processes.

The Mode I opening SIFs have been calculated using linear elastic Finite Element Analysis using contour integration. The modelling methodology was verified by comparison with published SIF solutions for semi-elliptical surface-breaking defects in a plate and also an unthreaded bar.

SIFs have been calculated for both membrane and bending loading. The defects were placed at the position of greatest bending stress with the defects symmetric about the bending plane.

SIFs have been calculated for different boundary conditions on the female thread side which affect the flow of load out of the stud, and hence the distribution of force in the stud and the resulting SIFs. The results show that if the flow of load in the stud is reversed, simulating reaction through a nut, then the calculated SIFs are higher than the case where the load is not reversed.
Pipeline Crack Half-Life Versus 1.10 Safety Factor at Next Inspection
Authors: Lamborn Lyndon , Shirband Zeynab , Kwok Ernest
Published: October 2020

Periodic inspection is a proven approach to structural integrity management of transportation systems. This is as true for pipelines as it is for aircraft and railways. Setting the re-inspection interval to ensure imperfections cannot grow to critical dimensions prior to the next inspection is a foundational requirement of this maintenance methodology.

API 1176 delineates two methods for re-inspection interval criteria for pipeline crack threat management: (1) maintaining a safety factor of 1.10 and at least a 30% of wall thickness remaining ligament depth until the next inspection, or (2) inspect at the half-life of the feature with the lowest remaining life taking the end of life being a 1.00 safety factor.

Recent proposed regulatory documents and draft rules have down-selected to Method (1), or at least demonstrating compliance to Method (1), which will require some operators who have only been using Method (2) to safely manage this change.

The two methods are compared for every asset of a large North American operator under current actual operating conditions. The relative conservatism of the two methods is directly compared. Sensitivity to a minimum remaining ligament requirement less than the recommended 30% of wall thickness is explored, and leak/rupture threat differentiation is considered. Implications of the change for a liquids pipeline operator in North America are described.
Buckling of Cylinders due to External Pressure: Experimental Work Compared With Finite Element Stress Analysis
Authors: Nadarajah Chithranjan , Hantz Benjamin F. , Krishnamurthy Sujay
Published: October 2020

The current design by analysis for protection against collapse from buckling in ASME Section VIII, Division 2, B&PV Code [8] has three different methods. However, these is no background bases for the three methods and analyst have found that the elastic plastic collapse analysis will give overly conservative results when compared with design by rule. Therefore, this study was undertaken to resolve this concern and develop a new procedure for buckling analysis to be implemented in the ASME Section VIII, Division 2, B&PV Code, Part 5.
Stress Analysis of In-Service Flare Gas Pipeline System and Equipment Nozzle
Authors: Pu Zhe , Ren Bin , Wang Jielu , Song Pan , Chen Delu
Published: October 2020

The flare system is an indispensable safety facility in petrochemical production. The function of the flare system is to collect the tail gas emitted from the production of each device into the main pipe of the flare, lead it pass through the liquid separation tank and the water seal tank in turn, and finally to the high-altitude flare for combustion and discharge into the atmosphere. The high temperature of flare gas pipeline will cause the pipeline to expand under heat. Due to the large thermal stress caused by the thermal expansion of the pipeline, the load on the nozzle of the connected equipment will be increased, which is easy to cause safety accidents. Taking the flare system of a whole factory as an example, this paper introduced a simple discriminated method to measure the flexibility of the pipeline system. The software CAESAR II was used to establish the model of the main flare pipe and the liquid separation tank in the whole factory. The calculated stress state of the pipe system meets the requirements of ASMEB31.3, and the stress of the liquid separation tank nozzle meets the technical conditions of the manufacturer. It is hoped that this method can provide some reference for the regular inspection of pipelines.
Floor Response Spectrum Method of Multiply Supported Piping System Assisted by Time History Analysis
Authors: Takayama Yoshihiro , Yoshida Ayaka , Nobuyoshi Iriki , Maeda Eiichi
Published: October 2020

The independent support motion response spectrum method (ISM) is currently used for seismic analysis to calculate the response of multiply supported piping with independent inputs of support excitations. This approach may derive considerable overestimation in the combination of group responses under the absolute sum rule of NUREG-1061 [1]. Then authors have developed an advanced method of the ISM approach named SATH (Spectrum Method Assisted by Time History Analysis). In the SATH method, both of floor response spectra and time histories of floor acceleration are used as independent inputs of support excitations. The group responses are summed with correlation coefficients which are calculated by considering each time history of modal response by independent inputs of support excitations. In this paper, the necessity of taking the effects of correlation coefficients for the group responses into account in the ISM approach is examined. The SATH method has advantage to derive a more realistic sum rule of the group responses and applicability for the actual design.
A Hybrid Fatigue Analysis Method for Fatigue Monitor System
Authors: Bai Xiaoming , Xie Hai , Shi Kaikai , Ai Honglei , Zheng Liangang , Mi Xue
Published: October 2020

During the operation of nuclear power plants (NPPs), the thermal fatigue is one of the most severe aging factors for the components. Therefore, it is significant to monitor the fatigue degradation of components caused by the thermal variation. Moreover, the fatigue monitor result is widely used in the life extension of NPPs. From this viewpoint, the Nuclear Power Institute of China (NPIC) has developed an advanced fatigue monitor system which can classify the operational transient and calculate the cumulative fatigue usage. In classical fatigue monitor system, two methods are widely used to calculate the cumulative fatigue usage. They are the cycle based method and the stress based method. In the cycle based method, the operational transient is classified into a conservative design transient, and then the remaining times of design transient is used to describe the fatigue condition. Obviously, the cycle based method is fast, but conservative. In the stress base method, the monitored thermal data is used to calculate stress and then do the fatigue analysis. This method is more accurate than the cycle based one, but this method is very time-consuming. In present work, a hybrid fatigue analysis of cycle based and stress based method is proposed. In this method, an off-line stress based fatigue database is developed using finite element method. The cycle based method is adopted to determine the transient effects. However, according to the off-line database, the consumed transient time is no longer an integer, but is a fraction to describe the difference between the cumulative fatigue usage of design transient and the one of operational transient.
A52M/SA52 Dissimilar Metal RPV Repair Weld: Experimental Evaluation and Post-Weld Characterizations
Authors: Virkkunen Iikka , Peltonen Mikko , Sirén Henrik , Nevasmaa Pekka , Huotilainen Caitlin , Keinänen Heikki , Kuutti Juha , Lambai Aloshious , Mohanty Gaurav , Honkanen Mari
Published: October 2020

Aging management of the existing fleet of nuclear power plants is becoming an increasingly important topic, especially as many units are approaching their design lifetimes or are entering long-term operation. As these plants continue to age, there is an increased probability for the need of repairs due to extended exposure to a harsh environment. It is paramount that qualified and validated solutions are readily available.

A repair method for a postulated through cladding crack into the low alloy steel of a nuclear power plant’s reactor pressure vessel has been investigated in this study. This paper is part of larger study that evaluates the current possibilities of such repair welds. The present paper documents the weld-trials and method selection. A parallel paper describes numerical simulations and optimization of weld parameters. The presented weld-trial represents a case where a postulated crack has been excavated and repaired using a nickel base Alloy 52M filler metal by gas metal arc welding-cold metal transfer with a robotic arm. A SA235 structural steel has been used as a base material in this weld-trial. No pre-heating or post-weld heat treatment will be applied, as it would be nearly impossible to apply these treatments in a reactor pressure vessel repair situation.

While Alloy 52M presents good material properties, in terms of resistance to environmentally assisted degradation mechanisms, such as primary water stress corrosion cracking, it is notoriously difficult to weld. Some difficulties and challenges during welding include a sluggish weld puddle, formation of titanium and/or aluminium oxides and its susceptibility to lack of fusion defects and weld metal cracking, such as ductility dip cracking and solidification cracking. Moreover, gas metal arc welding-cold metal transfer is not traditionally used in the nuclear industry. Nonetheless, it presents some interesting advantages, specifically concerning heat input requirements and automation possibilities, as compared to traditional welding methods.

The mechanical properties, in terms of indentation hardness, and microstructure of a weld-trial sample have been evaluated in this study. The fusion boundary and heat affected zone were the main areas of focus when evaluating the mechanical and microstructural properties. Detailed microstructural characterization using electron backscatter diffraction and nanoindentation were performed across the weld interface. Based on these results, the gas metal arc welding cold metal transfer is seen as a potential high-quality weld method for reactor pressure vessel repair cases.
Brittle Fracture of Stainless Steel Dissimilar Metal Welds in the Upper Shelf of the Brittle-to-Ductile Transition Range
Authors: Ben Salem G. , Chapuliot S. , Blouin A. , Bompard P. , Jacquemoud C.
Published: October 2020

Stainless steel dissimilar metal welds (SS DMW) are widely used within the French nuclear power plants where they connect the main components (pressure vessel, pressurizer, steam generator) made of low alloy ferritic steel to the primary circuit pipes made of austenitic stainless steel. Because of their heterogeneous microstructure and mechanical properties, these junctions are critical components for the structure integrity and their fracture resistance has to be demonstrated for all the nominal or accidental operating conditions. This work aims at building a model to evaluate the risk of brittle fracture of the SS DMW in the upper shelf of the brittle-to ductile transition range. The observation of the microstructures around the fusion line revealed a martensitic layer and a fully austenitic zone, which undergo an important carbides precipitation during the post-weld heat treatment and form a narrow hard layer of carburized martensite and austenite. Fracture toughness tests were then carried out on CT specimens in the brittle-to-ductile temperature range and helped identify the MA interface (between martensite and austenite) as the weakest region in the SS DMW because of an intergranular fracture mechanism initiated at the carbides-rich interface. This mechanism was consistently observed for specimens with fatigue precrack fronts in the hard layer. To model the brittle behavior of the MA interface, the stress distributions on the MA interface were calculated with FE numerical simulation of the fracture toughness tests and a 1D 3 parameters Weibull model based on a threshold stress and a threshold length was identified for the CT specimens. The temperature dependence of the model parameters was finally studied and the effect of temperature on the intergranular fracture mechanism of the MA interface was explored.
Evaluation of Mechanical and Corrosion Properties of Base Metal and HAZ Having ASS 304L Forgings Containing Ferrite
Authors: Patel Ritesh , Shah Hardik , Dutt Jimmy
Published: October 2020

Austenitic Stainless Steel type 304L is being widely used for fabrication due to excellent corrosion resistance and good weldability. Ferrite (3–10%) is needed in weld metal to prevent hot cracking during welding, however, base metal should preferably not contain any ferrite. It is observed that thick forged SS304L components may have small percentage of ferrite depending on the chemical composition, forging parameters including intermediate soaking cycle and final solution annealing heat treatment cycle. Little study or information is available on effect of ferrite in base metal on weld/Heat Affected Zone (HAZ) properties.

Present study is aimed to evaluate mechanical and corrosion properties of weldment produced with base metal containing 2–4% of ferrite. Forged tubes with two different levels of delta ferrite, with < 0.5% & 2–4%, were welded to Plates with < 0.5% delta ferrite using Mechanized Gas Tungsten Arc Welding (GTAW) process with Inner Bore Welding Technique. Tensile test, Impact test and Hardness test were performed on base metal & HAZ in as-welded condition for both the cases. Microstructure examination in HAZ and Intergranular Corrosion (IGC) test were also performed for both the cases. Results of mechanical tests, microstructure examination and IGC test have been compared between base metal/HAZ of < 0.5% and 2–4% Ferrite base metal. No significant difference has been observed in test result of tubes with 2–4% delta ferrite as compared to tubes with < 0.5% delta ferrite.
Comparative Evaluation of Plastic Design Methods for Fatigue Assessment of a Nuclear Class 1 Piping Nozzle
Authors: Clarkson David M. , Bell Christopher D. , Mackenzie Donald
Published: October 2020

Design-by-analysis (DBA) procedures for Nuclear Class 1 pressure vessels such as those prescribed within ASME Boiler and Pressure Vessel Code (BPVC) Section III, provide rules to demonstrate assurance against fatigue failure. Two general assessment routes exist, linear finite element analysis (FEA) with stress categorization and elastic-plastic penalty factors, or nonlinear FEA with direct multiaxial strain evaluation. Whilst the elastic design route possesses many practical advantages, it is widely acknowledged to be very conservative, sometimes unacceptably so. At the cost of additional analysis effort, plastic design methods can provide a more appropriate evaluation of fatigue usage, potentially avoiding unnecessary design modifications and reducing the burden of in-service inspection requirements.

This paper presents and compares various strain measures proposed for ASME III plastic fatigue analysis within the technical literature. A case study of a typical pressurized water reactor (PWR) main coolant line (MCL) piping nozzle subjected to pressure and thermal loads is presented. The influence of strain measure selection on the FE-derived strain concentration (Ke) factors is examined. Some important considerations for calculation of realistic Ke factors in ASME III are further discussed.
Validation of a Finite Element Toolbox for Studying Flaw Interaction
Authors: Coules Harry E.
Published: October 2020

Structural integrity assessment often requires the interaction of multiple closely-spaced cracks or flaws in a structure to be considered. Although many procedures for structural integrity assessment include rules for determining the significance of flaw interaction, and for re-characterising interacting flaws, these rules can be difficult to validate in a fracture mechanics framework. int_defects is an open-source MATLAB toolbox which uses the Abaqus finite element suite to perform large-scale parametric studies in cracked-body analysis. It is designed to allow developers of assessment codes to check the accuracy of simplified interaction criteria under a wide range of conditions, e.g. for different interacting flaw geometries, material models and loading cases. int_defects can help analysts perform parametric studies to determine linear elastic crack tip stress field parameters, elastic-plastic parameters and plastic limit loads for simple three-dimensional cracked bodies relevant to assessment codes. This article focusses on the validation of int_defects using existing fracture mechanics results.

Through a set of validation examples, int_defects is shown to produce accurate results for a very wide range of cases in both linear and non-linear cracked-body analysis. Nevertheless, it is emphasised that users of this software should be conscious of the inherent limitations of LEFM and EPFM theory when applied to real fracture processes, and effects such as constraint loss should be considered when formulating interaction criteria.
Failure Limit State Investigation of Misaligned Welded Plates by Using a Damage Model-Based Upon Triaxiality and Lode Parameters
Authors: Santos Iago S. , Sarzosa Diego F. B.
Published: October 2020

This paper presents a numerical study using the finite element method to assess the structural integrity of welded plates. Different levels of weld misalignment were introduced on the FEM models to investigate the influence of this welding imperfection parameter on the limit state of the structure. The models were loaded under displacement-controlled condition to introduce traction and torsion loads seeking to understand the effects of combined loads on the strain capacity of the misaligned welded structure. Surface elliptical cracks having different crack-size ratios were modeled to study the crack growth behavior by taking into account the misalignment of the weld and combined loads. The damage model is based on a failure surface and post-initiation behavior to model the ductile crack initiation and propagation steps, respectively. The models provide useful information to track the evolution of damage on the hot spot point of the welded structure. The model used is dependent on stress triaxiality and a Lode-based parameter and the damage level is driven by the plastic strain. The evolution of stress triaxiality and Lode parameter with loading are presented, and the influence of misalignment on them are shown. An exponential softening law was adopted to predict post-initiation failure behavior. The calibration steps of the parameters required for damage model application are shown for a A285 pressure vessel steel. Overall, the numerical models reveal the deleterious effects of weld misalignment and combined torsional and tensile loads on the strain capacity of the weld.
Practical Estimation of Retorque Requirements
Authors: Bausman Anita
Published: October 2020

The initial assembly of a bolted flanged joint (BFJ) commonly includes several ramped torque steps using various bolt torque patterns, final circular pass(es) at 100% of target torque, and then the choice of whether and when to come back and retorque the just-assembled joint. The value of retorquing a newly assembled bolted flanged joint varies significantly by which gasket material and type is used in the joint. The additional maintenance costs of labor, tool rental, scaffolding, crane usage, etc. to perform a retorque on a joint can be significant, but the larger cost is generally the additional process downtime.

Gaskets based on sheet materials are often retorqued. Conventional practice indicates that BFJs with gaskets made from flexible graphite or fiber sheets typically do not benefit from retorques, or at least do not benefit enough to offset the additional costs. Conversely, industry experience with many polytetrafluoroethylene (PTFE) based gaskets indicates these joints benefit significantly from retorquing a BFJ after initial assembly.

This paper explores some practical methods to estimate potential retorque benefit as a function of retained gasket stress without the retorque at temperatures normally “in range” for the gasket material being considered. That is, at temperatures that would not cause thermal damage to the gasket material. For flexible graphite and fiber materials known to experience mechanical property degradation with time and/or temperature (“aging”), a typical 5-year life is used. For PTFE gaskets known to relax primarily with temperature and that do not appreciably age, use of the Hot Blowout Thermal Cycling test (HOBTC) can provide a quick evaluation of gasket stress loss as a function of temperature. Retained gasket stress in both cases can then be used to estimate tightness for the gasket material using the Room Temperature Tightness (ROTT) data. If the joint is still at or above required tightness, then retorquing the joint soon after initial assembly is of little benefit. If the gasket has lost enough stress, then a retorque can bring the gasket stress back into range to provide sufficient tightness. Knowing this, the end user can make better choices for both gasket material selection and assembly procedures in order to reduce overall job costs.
Development and Test of Liquefied Gas Leakage Rate Measurement Device for Limited Aperture Release
Authors: Liu Cenfan , Ji Fang , Duan Linlin , Chen Sheng , Sun Liang
Published: October 2020

The liquefied gas has been widely used in modern chemical, energy and environment protection industries. To support the integrity management and risk assessment of liquefied gas storage tanks, it is necessary to study the leakage process of liquefied gas with limited holes. There are few researches about the liquefied gas leakage rate from the crack. At present, most measurement methods used to measure leakage rate are flow meter or weighing before and after discharge, which are not suitable for liquefied gas discharge. The discharge of liquefied gas can easily form a two-phase flow in the crack and cannot be measured by the flow meter. However, the method of weighing before and after discharge cannot measure the leakage rate in real time. To realize the leakage rate real-time, online measurement, the new liquefied gas leakage rate measurement device was set up in this study. And the detachable crack leakage modules with different diameters were designed and manufactured. Using R134a refrigerant as leakage experiment medium, the relationship between crack morphology, size, pressure and leakage rate of liquefied gas was studied on the liquefied gas leakage measurement device. The new device can be used as an experimental test platform for evaluating the consequences of different liquefied gas discharge accidents or optimizing the leakage flow coefficient of the specific leakage situation, so as to better simulate the liquefied gas discharge accidents.
Improving Flange Designs Based on ASME Section VIII Div. 1, Appendix 2
Authors: Cary Chris W.
Published: October 2020

Although improved methods for flange design have been under development for many years, ASME Boiler and Pressure Vessel Code Section VIII, Division 1 Appendix 2 continues to be the basis for the design of most custom pressure vessel flanges. While the method does a reasonably good job of calculating flange stress and rotation from the design loadings, it does not closely constrain some of the design input variables, such as gasket width and geometry, allowing the designer to produce poorly-performing designs. Also, the gasket loading factors (m & y values) have long been recognized as needing improvement. These weaknesses occasionally result in flanges which are difficult to seal, even with very high assembly bolt stress. In response to these weaknesses in the Appendix 2 method, various attempts to improve the method may be employed, and are sometimes required by end-user specifications. This paper provides an assessment of the effectiveness of various improvement techniques by examining the actual effects on flange designs across a range of diameter and design pressure, and makes recommendations for the use of such techniques. The analysis methods in PCC-1 and WRC Bulletin 538 are used as the basis of the evaluation, with a focus on gasket stress as fundamental to sealing.
Study on the Predictive Evaluation Method for Liquid Surface Shape and Flow Velocity in Nonlinear Sloshing Based on Simplified Equations
Authors: Ikesue Shunichi , Morita Hideyuki , Takata Tomoshige , Madokoro Hideki , Ishii Hidekazu , Sago Hiromi , Yokoi Shinobu , Yamamoto Tomohiko
Published: October 2020

When cylindrical tanks installed in the ground, such as oil tanks and liquid storage tanks, receive strong seismic waves, including the long-period component, motion of the liquid surface inside the tank called sloshing may occur. If large-amplitude sloshing occurs and the waves collide with the tank roof, it may lead to accidents such as damage of the tank roof or outflow of internal liquid of the tank. Also, there is a possibility that the internal components in the tank may be damaged due to the fluid force generated by the flow of the sloshing.

In order to evaluate the load acting on the tank roof, it is considered that the liquid surface shape and the liquid surface velocity are required as input parameters. In order to evaluate the load acting on the internal component in the tank, the flow velocity generated by sloshing is required as an input parameter. If the sloshing wave height is small, these values can be calculated based on the linear potential theory. However, when the sloshing wave height increases, the sloshing becomes nonlinear, and the difference between the nonlinear sloshing behavior and the linear sloshing behavior. Therefore, the method of evaluating nonlinear sloshing behavior is necessary to evaluate the design load of tank under the large sloshing wave height condition.

In this paper, new methods of evaluating nonlinear sloshing behavior are proposed for the first-order sloshing mode of a cylindrical tank, which can evaluate the maximum nonlinear sloshing wave height, the nonlinear liquid surface shape, the liquid surface velocity, and the flow velocity. Proposed methods, which consist of simplified equations, are expected to be applied to a new sloshing load evaluation method in primary design.1
High Frequency Fatigue and Using Frequency Domain Techniques
Authors: Francis Benjamin , Mair David
Published: October 2020

In recent years API 579 has provided the analyst with a detailed outline of the Wang-Brown algorithm (WBCC) for the cycle counting. The WBCC algorithm has become the generally accepted core of cycle counting implementations whenever multi-axial non-proportional fatigue stress histories are encountered. However, for vibration based fatigue, in the absence of any time history at all; it is common in industry to assess fatigue using frequency domain techniques. This paper presents special considerations for determination of the spectral stress fatigue in the spirit of API 579.

In the frequency domain the stress cycles are counted a priori as a set of complex vectors. These complex stress vectors may represent the full stress tensor of a reduced set in an appropriate sub-space. The phase relationship between the vectors represents the time delay between the stress components of the stress field. This paper presents some of the actions that are necessary in order to accurately capture the phase relationships.

It is often the case that the physics of the driving loads are either unknown or too complex to practically model. This is the case for complex fluid and particle interactions with vessel shells, piping or other wetted surfaces. This paper presents some tools and techniques that can be applied in order to characterize the loading spectrum in a manner which is specifically designed to capture the important fatigue characteristics.

Any fatigue estimation technique must convert the stress vector set into a singularly dimensioned scalar metric that represents the stress amplitude of a cycle. However, the maximum stress amplitude from the cycle is not immediately accessible from the complex stress vectors. While a number of papers present techniques that are intended to calculate the maximum stress amplitude in the case where the stress metric is the equivalent stress this paper provides a slightly more general relation for the phase of the maximum amplitude.

Finally the analyst must compare their calculated fatigue stress amplitudes to the API 579 fatigue curves. Closed form expressions for mono-linear spectral fatigue have been extensively investigated in the literature but more complex fatigue curves do not have such simple solutions. To this end this paper investigates the smooth bar carbon steel fatigue curves of ASME VIII-2.
ATLAS+ European Project: Prediction of Large Ductile Tearing in Austenitic Piping Using Local Approach
Authors: Blouin Arnaud , Marie Stéphane
Published: October 2020

In the frame of the European ATLAS+ project it was decided to evaluate if a continuum damage model can simulate a four-points bending test on an austenitic pipe (316L type) with an aged welded joint. In this paper, the theoretical background is presented. Then, based on finite elements analyses, the GTN model damage parameters are defined by simulating laboratory tests on Notched Tensile specimens and Compact Tension specimen. Finally, the four points bending test simulation is also presented.
Modified 9Cr Steel: Coke Resistant Tubes/Pipes Developed by Vallourec for Refinery Furnaces
Authors: Pirón Javier , Hamart Olivier
Published: October 2020

A new modified 9 wt% Cr steel has been developed in order to improve the resistance against coke deposition on the internal surface of refinery tube furnaces, in comparison to widely used grades, such as Grade 5 (5 wt% Cr) or Grade 9 (9 wt% Cr). The new grade has an improved composition, based on Cr and Si and further additions of Cu and Ni. This optimal chemical analysis has been specified after extensive laboratory testing on different laboratory and industrial heats. Thermogravimetric analyses have been performed to benchmark various materials (ferritic and austenitic grades) in terms of coking rate. Specimens of these alloys have been exposed to this coking atmosphere in a wide temperature range. The new modified 9Cr steel exhibits an almost 10 times lower coking rates than typical Grade 9 steel. The new 9Cr steel shows allowable stress levels up to 90% higher than Grade 9 at temperatures below 500°C (time independent regime) and up to 7% higher stress levels at temperatures above 500°C (creep regime). The industrial feasibility of production of elbows has been successfully implemented and a welding solution using a commercially available filler material has been established.