bluuebunny/crossref_metadata_2025 huggingface dataset:
Removal of user fees and system strengthening improves access to maternity care, reducing neonatal mortality in a district hospital in Lesotho
Authors: Steele Sarah Jane , Sugianto Hartini , Baglione Quentin , Sedlimaier Sandra , Niyibizi Aline Aurore , Duncan Kristal , Hill Julia , Brix Jesper , Philips Mit , Cutsem Gilles Van , Shroufi Amir
Published: October 2018

Objective

Lesotho has one of the highest maternal mortality rates in the world. While at primary health care (PHC) level maternity care is free, at hospital level co‐payments are required from patients. We describe service utilisation and delivery outcomes before and after removal of user fees and quality of delivery care, and associated costs, at St Joseph's Hospital (SJH) in Roma, Lesotho.

Methods

We compared utilisation of delivery services, stillbirths and maternal and neonatal mortality for the periods before (1 July 2012 to 31 December 2013) and after (1 January 2014 to 30 June 2015) user fee removal through a retrospective chart review and estimated additional costs attributed to user fee removal from provider (hospital) and patient perspectives.

Results

Of 4715 deliveries 3855 were at SJH and 860 at PHC centres. Of women delivering at SJH 684 (18.5%) were ≤19 years and 894 (23.6%) were HIV positive. After user fee removal hospital deliveries increased by 49% — from 1547 to 2308 — and neonatal mortality decreased from 4.8 to 1.3 per 1000 live births (P = 0.033). Extrapolating costs to the entire country, 1 USD per capita per year would allow user fee removal at hospital level, the provision of free transport to/from and accommodation at hospital.

Conclusion

Removing user fees for hospital delivery care in Lesotho is feasible and affordable, and has the potential to improve maternal and neonatal outcomes by removing financial barriers to skilled birth attendants and increasing coverage of institutional deliveries.
Actualización en la comprensión y manejo de la intoxicación por acetaminofén
Authors: Castellanos Garzón Rafael Gustavo , Barrios Peralta Elkin Rene , Vides Velásquez Alberto Adolfo , Olarte Maria Francisca
Published: October 2018

La intoxicación por acetaminofén es una de las causas más frecuentes de falla hepática aguda fulminante y una de las principales causas de atención en los servicios de urgencias, por intoxicación debida a medicamentos. Recientemente, se han registrado avances en la comprensión fisiopatológica, diagnóstico y tratamiento de esta entidad clínica. Los mecanismos de estrés oxidativo y daño del ADN mitocondrial explican los daños producidos en esta intoxicación. En esta revisión se presentan aspectos referentes a la epidemiología, mecanismos fisiopatológicos, diagnóstico y tratamiento de la intoxicación por acetaminofén.
Modelos de entrenamiento en cirugía mínimamente invasiva para pieloplastia laparoscópica: revisión de la literatura*
Authors: Moreno Feddy , Villamizar Pedro , Corchuelo Valentina , Rodríguez Miguel , Ordoñez Stephanie , Tejada Marcela
Published: October 2018

Resumen

Introducción: la pieloplastia laparoscópica es un procedimiento mínimamente invasivo empleado para solucionar quirúrgicamente estenosis, bloqueo u obstrucción de la unión ureteropélvica o pieloureteral. Objetivo: explorar los diferentes modelos de entrenamiento en cirugía mínimamente invasiva para pieloplastia laparoscópica que se encuentran reportados en la literatura. Materiales y métodos: se revisó la literatura con búsqueda sistemática en PubMed, Google Académico y SciELO, mediante la declaración PRISMA y la combinación de los descriptores médicos en salud Model training AND laparoscopic pyeloplasty. Además, se empleó GoPubMed para obtener información bibliométrica que contextualizara las redes de investigación y publicación entre los diferentes modelos de entrenamiento para pieloplastia laparoscópica. Resultados: Se incluyeron 17 referencias en la búsqueda sistemática de la literatura con los que se realizó la discusión a partir de la usabilidad, la estética y el tiempo operatorio de la pieloplastia laparoscópica. Conclusión: Todos los modelos de entrenamiento contribuyen a que los operadores disminuyan los tiempos quirúrgicos, alcanzando valores próximos a la pieloplastia laparoscópica in situ, inclusive, a la pieloplastia abierta. De forma particular, los modelos anatomopatológicos elaborados con modelamiento de siliconas logran un notable acercamiento a la realidad morfológica a partir de la estética de las estructuras y permiten aumentar el número de intentos quirúrgicos y la cantidad de horas de práctica.
Fatigue Monitoring: Case Studies in Nuclear Power Plant
Authors: Bourguigne G. , Schroeter F.
Published: October 2018

During design of Class I components in Nuclear Power Plants, cumulative usage factors (CUF) are conservatively calculated to estimate fatigue damage, and results must be below the limits of the applicable codes. Nevertheless, when these results are used to evaluate the possibility of using these components for an extended life, the results are frequently above code limits. Many Nuclear Power Plants have installed commercial fatigue monitoring systems at critical components in order to assess transient severity and cycle count for life extension fatigue calculations among other reasons. Since the commissioning of the system, unexpected operation modes and thermal stratification was discovered and evaluations needed to be done. Findings, interpretations and solving are presented in this paper.
Effect of Autoclave Cure Time and Surface Preparation on Film Adhesive Bond in Lightweight Material Joints
Authors: Morfini Isotta , Goglio Luca , Belingardi Giovanni , Nassar Sayed A.
Published: October 2018

This study investigates the effect of cure time and surface roughness on mechanical performance of single lap joints (SLJ). Test joints are made of aluminum/aluminum or aluminum/magnesium adherends that are autoclave-bonded using a commercially available film adhesive. Joint mechanical performance is assessed in terms of the static load transfer capacity (LTC), fatigue life and failure mode. Except for the cure time, all the rates of the other autoclave-bonding parameters are kept constant; namely, the level of cure temperature and pressure, as well as the rates of autoclave heating, cooling, pressurization and depressurization. Test data, failure mode analysis, discussion, observations and conclusions are provided.
Analytical Modeling of Self-Loosening of Bolted Joints
Authors: Fort Valentin , Bouzid Abdel-Hakim , Gratton Michel
Published: October 2018

Self-loosening of bolted joints is a common issue in Pressure Vessel and Piping equipment. This phenomenon can not only cause the industry a lot of losses due to maintenance but can result in catastrophic incidents leading to environment and health issues. This paper presents several improvements and innovations that are brought to the subject of self-loosening of bolted joints through a study involving analytical, numerical and experimental work.

A new model to prevent self-loosening of bolted joints is developed. Particular focus is put on the effect of the clamping plate thickness on the self-loosening of the joint. A fully instrumented experimental set-up, in conjunction with an M12-1.75 bolt, is deployed to track the bolt tension decrease with the application of an imposed cyclic transversal displacement. In addition to the measurement of the transverse relative displacement between the two clamping parts, the clamping and transverse loads are also recorded. Finally, the relative rotation between the bolt and the nut is measured by means of a rotation sensor directly installed on the nut. The results show that there is a good agreement between the analytical, numerical and experimental results. The new model is compared with FEM and experimentation for different plate thickness configurations.
Plastic Collapse Stresses for Pipes With Circumferential Twin Flaws Using Combination Rules
Authors: Hasegawa Kunio , Li Yinsheng , Kim Yun-Jae , Lacroix Valery , Strnadel Bohumir
Published: October 2018

When discrete multiple flaws are in the same plane, and they are close to each other, it can be determined whether they are combined or standalone in accordance with combination rules provided by fitness-for-service (FFS) codes, such as ASME, JSME, BS7910, FKM, WES2805, etc. However, specific criteria of the rules are different amongst these FFS codes.

On the other hand, plastic collapse bending stresses for stainless steel pipes with circumferential twin flaws were obtained by experiments and the prediction procedure for collapse stresses for pipes with twin flaws were developed analytically. Using the experimental data and the analytical procedure, plastic collapse stresses for pipes with twin flaws are compared with the stresses in compliance with the combination criteria. It is shown that the calculated plastic collapse stresses based on the combination criteria are significantly different from the experimental and analytical stresses.
Development of a Closed-Form Expression for the Assessment of the Integrity of Internally Corroded Pipelines
Authors: Fahed M. , Barsoum I.
Published: October 2018

Carbon steel pipelines are renowned for their long-term resistance to the hydrostatic pressure of the transported fluid. Nevertheless, failure of carbon steel pipes can be catastrophic if not predicted or mitigated properly. One of the most common failure causes in carbon steel pipelines is corrosion of the pipeline inner and outer surfaces. The corrosion on pipeline walls will eventually lead to severe loss of material to a point which will cause complete loss of pipeline integrity. The study will assess the burst pressure of predefined internal corrosion-defected carbon steel pipelines through finite element analysis. The mechanical response of the host carbon steel pipeline is empirically estimated. A set of corrosion defect geometrical sizes, such as depth width and length to be considered is carefully developed. Accordingly, a parametric study considering the developed set of defect geometrical parameters, as well as the mechanical response of the pipe material, is conducted. The parametric study is performed through finite element analysis to investigate the influence of the highlighted parameters to the overall burst pressure of the pipe. Based on the results from parametric study of corrosion-defected carbon steel pipelines, the Buckingham π-theorem modelling approach is used to derive an analytical closed-form expression to predict the burst pressure of defected pipes containing internal corrosion defects of an arbitrary size.
Challenges Associated With the Quantitative Analysis of Ductile Damage Using X-Ray Computed Tomography
Authors: Cooper Adam J. , Burnett Timothy L. , Tuck Olivia C. G. , Sherry Andrew H.
Published: October 2018

We have recently reported on the mechanistic differences in ductile failure between stainless steel manufactured by hot isostatic pressing (HIP) and forging, from which it was established that the oxygen concentration must be properly controlled. As part of an ongoing investigation into the mechanics of ductile failure in novel HIP materials, X-ray CT has been employed as a tool to quantify and characterize the differences in ductile damage below the fracture surface of failed compact tension fracture toughness test specimens. Herein we report on some of the challenges associated with handling data relative to the fracture surface, which can extend far into the cores under investigation.
2025 Nuclear Code: The Vision for the Future of ASME Nuclear Codes and Standards
Authors: Matthews Dale E. , Hill Ralph S. , Bruny Charles W.
Published: October 2018

ASME Nuclear Codes and Standards are used worldwide in the construction, inspection, and repair of commercial nuclear power plants. As the industry looks to the future of nuclear power and some of the new plant designs under development, there will be some significant departures from the current light water reactor (LWR) technology. Some examples are gas-cooled and liquid metal-cooled high temperature reactors (HTRs), small modular reactors (SMRs), and fusion energy devices that are currently under development. Many of these designs will have different safety challenges from the current LWR fleet.

Variations of the current LWR technology are also expected to remain in use for the foreseeable future. Worldwide, many LWRs are planned or are already under construction. However, technology for construction of these plants has advanced considerably since most of the current construction codes were written. As a result, many modern design and fabrication methods available today, which provide both safety and economic benefits, cannot be fully utilized since they are not addressed by Code rules.

For ASME Nuclear Codes and Standards to maintain and enhance their position as the worldwide leader in the nuclear power industry, they will need to be modernized to address these items. Accordingly, the ASME Nuclear Codes and Standards organizations have initiated the “2025 Nuclear Code” initiative. The purpose of this initiative is to modernize all aspects of ASME’s Nuclear Codes and Standards to adopt new technologies in plant design, construction, and life cycle management. Examples include modernized finite element analysis and fatigue rules, and incorporation of probabilistic and risk-informed methodology. This paper will present the vision for the 2025 ASME Nuclear Codes and Standards and will discuss some of the key elements that are being considered.
The Reciprocal Effect Among a Quarter-Circle Corner Crack and a Non-Aligned Surface Crack of Comparable Size in an Infinitely Large Plate Under Uniaxial Tension
Authors: Perl M. , Levy C. , Ma Q.
Published: October 2018

The reciprocal effect between a quarter-circle corner crack and a non-aligned surface crack of comparable size is addressed in the present study. The significance of understanding the reciprocal effect between the non-aligned parallel cracks is to assist in the evaluation of non-aligned multiple cracks as required in various fitness-for-service codes. For non-aligned parallel cracks, on-site inspection needs to decide whether the cracks should be treated as coalesced or separate multiple cracks. In the existing literature, criteria and standards for the adjustment of multiple non-aligned cracks are very source dependent, and those criteria and standards are often derived from on-site service experience without rigorous and systematic verification. Based on this observation, the authors previously reported on the effect of an embedded parallel crack on an edge crack in 2-D scenarios and, more recently, in 3-D scenarios of a circular corner crack influenced by a parallel surface crack. It may be just as important to evaluate the mutual effect of a quarter-circle corner crack on a non-aligned surface crack as reflected in their stress intensity factors (SIFs). In the present study, the quarter-circle corner crack and the non-aligned surface crack are assumed to be of the same length a2 = a1 = 15mm. While keeping throughout the entire analysis the geometry of the quarter-circle corner crack unchanged, the relative depth of the semi-elliptical surface crack is varied so that b1/a1 = 0.2–1.0. For each particular case a pair of horizontal (H) and vertical (S) separation distances between the two cracks is chosen (H/a2 = 0.4–2 and S/a2 = −0.5–2) and the SIFs along the 3D crack fronts are extracted for both the corner and the surface crack. The reciprocal effect on the SIFs for both cracks are discussed. It is found that the mutual influence between the corner crack and the surface crack are equally important, and each may dominate the decision making based on present criteria and standards in Fitness-for-Service.
Building the UK ABWR: Developments in Structural Integrity Safety Cases for Highest Reliability Components in the UK
Authors: Jelfs Tim , O’Neill James , Beveridge Angus
Published: October 2018

Nuclear power plants contain certain components whose gross failure would lead to intolerable radiological consequences. In the UK, a common terminology used for such components is Very High Integrity (VHI). If it is not possible to engineer lines of protection for these components, a safety case must demonstrate to UK regulators that the probability of gross failure is demonstrably so low that it can be discounted. A previous paper [Ref. 1] has described, at a high level, how the structural integrity safety case for a nuclear new build project in the UK — the UK Advanced Boiling Water Reactor (UK ABWR) is being structured.

As described in [Ref. 1], the structural integrity safety case for the UK ABWR is based on the guidance provided by the UK Technical Advisory Group on Structural Integrity (TAGSI) and aims to demonstrate a multi-legged safety case with robust and independent legs giving confidence of defense in depth. Design to the internationally recognized ASME code [Refs. 2, 3, 4] is supplemented by a significant number of beyond code requirements such as supplementary inspection and inspection qualification, augmented material testing requirements, defect tolerance assessment to the well-established R6 procedure [Ref. 5], and demonstration that design and manufacturing processes have reduced risks to As Low as Reasonably Practicable (ALARP).

This paper provides an updated position of the progress made on the UK ABWR project. It also provides more specific details on the activities the future licensee, Horizon Nuclear Power, has performed in support of the demonstration that design and manufacturing processes have reduced risks to ALARP. This kind of additional work is vital to providing the UK regulator with confidence that the risk of failure of VHI components has been reduced to ALARP.
Influence of Defect Distribution on Dynamic Elastic Buckling of Rings Under Internal Uniformly-Distributed Pressure Pulse
Authors: Dong Qi , Yang Sha , Zhang Liucheng
Published: October 2018

In our previous papers, it has been reported that when rings and shells are subjected to an internal uniformly-distributed pressure pulse, dynamic elastic buckling due to the nonlinear coupling between the breathing mode and bending modes may occur and further cause the strain growth phenomenon in explosion containment vessels. In this study, the influence of defect distribution on dynamic buckling of plane-strain rings under internal uniformly-distributed pressure pulse is studied, in which three cases with one defect, six defects and twelve defects are employed in the finite element model. It is found that defects influence the initial buckling response shapes and occurrence of dynamic buckling. However, the excited bending mode is the same for the different defect distribution cases.
PTS on Embedded Rotated Cracks and Projection Rules
Authors: Stefanini L. , Blom F. J.
Published: October 2018

The Pressurized Thermal Shock (PTS) is one of the transients of concern in a nuclear reactor. The phenomenon takes place when the down-comer and internal Reactor Pressure Vessel (RPV) surfaces are rapidly cooled down while the system is still under pressure.

This event is considered life limiting for the safety case where cracks are postulated and the RPV material embrittled by neutron radiation damage.

During this study, an elliptical embedded crack was postulated in a cylindrical geometry simulating the RPV. The system, initially at high temperature and under pressure load condition, was subject to a PTS transient. Thermal and structural analyses were carried out for various crack configurations. Particularly, besides the axial crack, skewed embedded axial cracks were modeled and analyzed (30°, 45° and 65°) for PTS phenomenon. Finite element analysis were carried out with ANSYS considering two variants: no-heat transmission and total heat transmission through the crack. Results showed that the highest stress intensity factor is obtained at an axial crack (0°). Moreover, it is shown that considering no-heat transmission through the crack is a conservative approach.

The ASME code approach to the skewed axial cracks characterization by projection is considered. It is found that the ASME approach is conservative, with an excess conservatism for largely skewed axial cracks. The same conclusions were reached when considering the projection rules from the R6 code.
Probabilistic Leak Before Break
Authors: Stefanini L. , Blom F. J.
Published: October 2018

In this study a probabilistic Leak-Before-Break (LBB) analysis was carried out based on the R6 FAD Option 1 assessment method. The method uses the material fracture toughness and yield stress in order to determine, deterministically, a Critical Crack Length (CCL) and a Leakage Rate (LR) through a crack. In order to define the fracture toughness of the material, the Master Curve approach was used accordingly to BS7910:2013 Annex J. Initially, deterministic analyses were carried out and the fracture toughness and yield stress were set to 190 MPa√m and 158 MPa, respectively. In order to implement a probabilistic approach, the yield stress and fracture toughness were introduced as stochastic parameter. The Fracture toughness was generated using a Weibull distribution to match the Master Curve. The distribution was built such that 190 MPa√m represents the 5% probability fracture toughness. The Yield stress (0.2% proof strength) was generated using a normal distribution with standard deviation 10.35 MPa such that the average value was 175 MPa and the lower bound (5% of probability of occurrence) was 158 MPa. The choice of building the distribution as above mentioned was justified by the fact that in structural integrity assessment the lower 5% is generally used for material parameters. Thus, once a Detectable Leakage Rate (DLR) was determined, it was possible to assign an implicit probability of failure to the deterministic case. The calculations were then extended by using several LR formulas. The calculations were carried out making use of the probabilistic software RAP++ coupled to MATLAB. The probabilities of failure were calculated with regard to a postulated DLR and a DLRSF corrected with a safety factor of 10. The probabilities of failure for the DLRSF were proved to be 9 to 15 times higher than for the postulated DLR case, which leads to the opportunity of conservatism reduction.
Consideration of Pressure Vessels Codes and Standards for Fire Emergency Rescue in China: Now and Future
Authors: Wang Junjun , Xue Lin , Ruan Zhen , Wu Peiying , Zhang Lei
Published: October 2018

As of the end of 2015, more than 20 transportable pressure vessel leakage accidents were put out every day by fire forces in China. Accidents put out by fire forces are primarily handled in accordance with codes and standards. This paper investigates and analyzes the codes and standards systems for pressure vessel and fire emergency rescue (FER) in China. Existing codes and standards for pressure vessel leakage do not include FER, which results in the firefighters being encumbered when addressing these accidents. Treatment methods for hazardous chemicals are included in the FER codes and standards, but they are not aimed at pressure vessels. One of the goals of the Plan for Furthering the Standardization Reforms released by the State Council in 2015 was to integrate and reduce the number of codes and standards. It is impossible to establish new FER standards for pressure vessels. To address this issue, this paper presents a new concept of pressure vessels standard for FER. This new concept features two aspects: (1) China’s Standardization Committee on Boilers and Pressure Vessels should absorb some fire practitioners, in particular fire scientific researchers and firefighters; and (2) the pressure vessel FER technologies, methods, and structural components should be added to the pressure vessel codes and standards.
The Follow Up on Profiled Wire Gasket Development and Testing With Case Studies
Authors: Currie Anthony
Published: October 2018

The paper discusses the development of sealing technology within the organisation with particular emphasis on the gasket manufactured by profiled winding wire. This will be referred to as a PWG.

The paper is a continuation of the paper presented in Paris PVP2013-97050 and follow up in PVP2014-28948. It discusses further laboratory testing and briefly describes 4 related field service case studies.

The paper details tests which include: Thermal cycle, sealing performance, compression and recovery testing carried out in both laboratory and field conditions. The 4 related studies are based around the use on large flanges, the use in oxygen rich environment, the use in a thermal cyclic environment and on problematic flange corrosion.
Compact Crack Arrest Tests for the Validation of a Finite Element Material Model of the Reactor Pressure Vessel Steel of the Nuclear Power Plant KKG
Authors: Mayer Uwe , Mutz Alexander , Nicak Tomas
Published: October 2018

The integrity of a reactor pressure vessel (RPV) has to be given for its operating time in accordance with the regulations. An assessment of the RPV against brittle failure needs to be conducted specially for one of the most severe loading cases. This is the loss-of-coolant accident (LOCA). Cold water is injected into the RPV at operating conditions. This thermal shock of the ferritic pressure vessel wall leads to loading conditions at the beltline area known as Pressurized Thermal Shock (PTS).

The assessment against brittle failure is based on a deterministic fracture analysis. Common parameters like stress intensity factors are employed to calculate the PTS event for an assumed (postulated) flaw. Subsequently the results of the fracture mechanics analysis are compared with material properties obtained from the irradiation surveillance program of the RPV to demonstrate the exclusion of brittle fracture initiation.

The validation considers the material data and the velocity of the crack growing into the specimen until it stops. The measured crack propagation velocity for tests performed according to ASTM E1221 [1] is compared to the result of the Finite Element (FE) simulation of a Compact Crack Arrest (CCA) test.

For five of eight tests performed at −60 °C crack propagation velocity values were determined ranging from 509 m/s to 694 m/s with an average value of 618 m/s.
Low Cycle Fatigue Behavior of Alloy 800H Base Metal and Weldments at 700°C
Authors: Kim Seon-Jin , Dewa Rando Tungga , Kim Woo-Gon , Kim Eung-Seon
Published: October 2018

Alloy 800H is currently being considered as one of the near-term candidate materials for design and construction of some major high temperature components of a very high temperature reactor (VHTR). System start-ups and shut-downs as well as power transients will produce low-cycle fatigue loadings of components. The aim of this work is to study the low cycle fatigue behavior of Alloy 800H base metal and weldments at 700°C. The weldment specimens were machined from gas tungsten arc welding (GTAW) butt-welded plate such that the loading direction was oriented transverse to the welding direction. Fully reversed total-strain controlled low-cycle fatigue tests have been performed at total strain ranges of 0.6, 0.9, 1.2 and 1.5%. For all the low-cycle fatigue tests, triangular test waveforms with a constant strain rate of 10−3/s were applied. Low-cycle fatigue testing was conducted in accordance with ASTM Standard E606 on servo-hydraulic test machines. And also, creep-fatigue experiments were carried out at 700°C employing 0.6% total strain range and 10−3/s strain rate using trapezoidal waveform with tension hold time. The main focus is to characterize the low-cycle fatigue properties for Alloy 800H weldment specimens from the cyclic deformation behavior and fatigue fracture behavior. The cyclic deformation behavior was influenced by total strain range and material property. The fatigue life was decreased with increasing the total strain range for both base metal and weldment. However, the lives of weldment specimens have a longer life than that of base metal at lower total strain ranges. It was also observed that creep effects play a significant role in fatigue life reduction.
Pneumatic Testing of Piping: Managing the Hazards for High Energy Tests
Authors: Arti Bader , Weyer Robert , Dang Thanh , Taagepera Jaan
Published: October 2018

Pneumatic pressure testing is used extensively during construction of LNG plants to avoid the problems that can be caused by water that may be left in a piping system (particularly in valves) if hydrotesting was performed. Due to the much greater compressibility of gas, there is significantly more energy (and thus risk) associated with a pneumatic test than with a hydrostatic test.

A major gas project safely conducted numerous pneumatic tests with stored energies of up to 6,675 MJ. Observing a commonly used limit of 270 MJ would have resulted in hundreds of additional closure welds.

This paper discusses practical aspects of performing pneumatic testing, the risk mitigations put in place and present two calculation methods that can be used to check whether exclusion zones for blast wave pressure are adequate for fragment throw.
Winding-Autofrettage Study on Reinforced Thermoplastics Vessel Based on ANSYS ACP
Authors: Huang Jinhao , Duan Chenghong , Wu Liang , Luo Xiangpeng
Published: October 2018

The process, by applying an internal pressure higher than the working pressure in advance after completion of the winding to cause the liner entering the plastic stage and producing the corresponding permanent plastic deformation for the purpose of improving the carrying capacity of the vessel, is called internal pressure autofrettage. In this paper, for the high-density polyethylene liner filament winding vessels which are winded by the equivalent cooling method, the ANSYS ACP module is used to analyze the stress distribution under autofrettage condition and working condition. The influence of autofrettage pressure and cooling temperature on the stress distribution under the working conditions of the vessel is addressed. This study could provide a reference for the optimization of winding process.
FEM Contact Stress Analysis at the Bearing Surfaces in Bolted Joints Under External Loadings
Authors: Shirakawa Atsushi , Sawa Toshiyuki , Naruse Tomohiro
Published: October 2018

The higher bolt preload is better for increasing the integrity of bolted joints. However, the bearing surface could be permanently deformed with too much high preload and the bolt preload decreases with permanent deformation. Thus, an upper limit of bolt preload per contact area at the bearing surfaces, which is called as the critical contact stress, must be examined for various materials of clamped parts. In the previous research, the critical contact stresses were obtained by compressing a cylindrical bar. However, the contact stress distribution of compressing a cylindrical bar is much different to that of an actual bolted joint. In addition, a lot of previous researches used the stress-strain curves under tensile loadings for analyzing the contact stress distributions at the bearing surfaces.

In this study, the Finite Element Method is used for contact stress analysis at the bearing surfaces in clamped bolted joints under external loading. Various materials for clamped part are chosen such as steel, aluminum alloy, cast iron and stainless steel. Firstly, the stress-strain curves for the above materials were measured under compressive loadings. The differences in the stress-strain curves under tensile and compressive loadings are evaluated with the above materials. Next, using actual bolts, the displacements at the bearing surfaces in cylindrical clamped parts consisting of the above materials were measured. Finally, elasto-plastic FEM contact stress analyses are carried out for analyzing the plastic displacements at the bearing surfaces under compressive loadings. The mean displacement at the bearing surfaces are compared with those obtained from the experiments for each material. The FEM results of the relationship between the contact stress and the plastic displacement at the bearing surface are in a fairy good agreement with the experimental results for each clamped material. In addition, the critical contact stress at the bearing surface is discussed for each material. Two proposals for the critical contact stress at the bearing surface are described and compared with the critical contact stress of VDI2230.
Technical Basis for Proposed Fifth Revision to ASME Code Case N-513
Authors: Cimock Dylan , Houston Eric J. , Cipolla Russell C. , McGill Robert O.
Published: October 2018

Code Case N-513 provides evaluation rules and criteria for temporary acceptance of flaws, including through-wall flaws, in moderate energy piping. The application of the Code Case is restricted to moderate energy, Class 2 and 3 systems, so that safety issues regarding short-term, degraded system operation are minimized. The first version of the Code Case was published in 1997. Since then, there have been four revisions to augment and clarify the evaluation requirements and acceptance criteria of the Code Case that have been published by ASME. The technical bases for the original version of the Code Case and the four revisions have been previously published [1, 2, and 3].

There is currently work underway to incorporate additional changes to the Code Case and this paper provides the technical basis for the changes proposed in a fifth revision. These changes include clarification for buried piping, investigation of various radii used in the Code Case, removal of the 0.1 limit on the flexibility characteristic for elbow flaw evaluation, and an update of the stress intensity factor parameters for circumferential through-wall flaws. In addition, a new flaw evaluation procedure is given for through-wall flaws in gate valve body ends. This procedure evaluates flaws in the end of the valve body as if in straight pipe. These changes and their technical bases are described in this paper. Clarifications and changes deemed editorial are not documented in this paper.
Introduction of Technical Document in Japan for Safe Use of Ground Storage Vessels Made of Low Alloy Steels for Hydrogen Refueling Stations
Authors: Fukumoto Hajime , Wada Yoru , Matsunaga Hisao , Sano Takeru , Kobayashi Hiroshi
Published: October 2018

As is well known, low alloy steels are widely used as materials for high pressure vessels because of their high tensile strength and reasonable price, but also show severe hydrogen embrittlement. Therefore, in 2016, the authors introduced a scenario for the safe use of low alloy steels in highly pressurized hydrogen gas as a “Guideline” at ASME PVP 2016 [1]. Following discussions with stakeholders and experts in recent years, we published Technical Document (TD) as an industrial standard prior to regulation, on the safe use of ground storage vessels made of low alloy steels in Hydrogen Refueling Stations (HRSs) based on performance requirements. This article presents an outline of the TD describing the required types of testing as performance requirements for confirming the good hydrogen compatibility of low alloy steels, such as controlling tensile strength in an appropriate range, confirming leak-before-break, determining the life of ground storage vessels by fatigue testing and determining the inspection term by fatigue crack growth analysis using the fatigue crack growth rate in highly pressurized hydrogen.
N-Bar Problems As Approximations to the Bree Problem
Authors: Messner M. C. , Sham T.-L. , Wang Yanli
Published: October 2018

The Bree solution to the problem of a ratcheting cylinder under constant pressure and cyclic thermal load is a fundamental result in nuclear engineering and widely used as the technical basis for the ASME Boiler and Pressure Vessel Code and other design methods. However, because the loading conditions in the Bree problem are difficult to achieve experimentally there have been relatively few works experimentally examining the problem and extending it to other relevant design situations, for example cladded components. In contrast, 2-bar problems are widely studied experimentally and are relatively easy to setup. These 2-bar problems are thought to be representative of Bree-type geometries, but a formal connection has not been demonstrated. This work formally establishes the connection between the Bree cylinder and an n-bar problem — a coupled bar experiment with, in general, more than two bars linked in parallel. The connection suggests that n-bar experiments using a fairly limited number of bars might be an experimentally-accessible setup that better represents ratcheting phenomenon in actual nuclear pressurized components. Such experiments could test surrogate cladded or multi-material components by using bars of different materials. Finally, this work suggests control schemes that yield optimally efficient n-bar experiments — experiments that best replicates a Bree cylinder with a limited number of bars.
A Treatise on Weld Evaluation
Authors: Chandiramani Dipak K. , Narayana Sadasivan
Published: October 2018

Welds are inspected by various techniques which include visual examination, surface examination and volumetric examination.

While the above techniques would qualify a weld to workmanship criteria, they would not necessarily be indicative of weld properties.

Preparation and qualification of welding procedures and testing of production welds are indicative that the weldment would probably provide a safe and satisfactory service life.

However, weldments have to operate at their design conditions which may include high temperatures and ASME Codes do not necessarily stipulate tests for verification of high temperature properties. In addition, defective welds are often repaired by removing the originally deposited weld metal and re-welding. The effects of double heat input are not necessarily evaluated.

In this paper, an insight is provided into the factors which provide assurance that weldments will perform satisfactorily in service and the combination of non-destructive evaluation methods which would enable effective detection of imperfections.

Non-destructive volumetric examination method for welds has traditionally be radiography. With the advent of automated data acquisition methods in Ultrasonics, like Time of Flight Diffraction and Phased Array Ultrasonic Testing, these methods are rapidly replacing radiographic methods for weld inspection.

Ultrasonic acceptance criteria in ASME Section VIII Div. 1, ASME Section VIII Div. 2 and ASME Section IX do not include evaluation of porosity as ultrasonic methods do not easily detect porosity.

The result of all this is that today we are accepting welders qualified using Ultrasonic examination as per ASME Section IX but on the job there is still the option of inspecting the weld using Radiography in which, excessive porosity can be a cause for weld repair.

Considering this and various other criteria, a comprehensive weld evaluation methodology is proposed taking advantage of the strengths of each inspection technique while welding technology used would ensure that welds have required properties at service temperatures.

A proposal is also made to improve the detectability of imperfections using modifications of existing Ultrasonic A-scan Techniques.
Fracture Toughness Testing Using Non-Standard PCVN Specimens: Experiments and Specimen Geometry Effects on T0 Reference Temperature
Authors: Barbosa Vitor Scarabeli , Ruggieri Claudio
Published: October 2018

This work addresses an experimental investigation on the cleavage fracture behavior of a high strength, low alloy structural steel using non-standard PCVN specimens. The primary purpose is to investigate the effects of increased specimen span on experimentally measured fracture toughness values and implications for the characterization of the temperature dependence of toughness based on the Master Curve methodology. Fracture toughness testing conducted on various PCVN geometries with increased specimen span extracted from an A572 Grade 50 steel plate provides the cleavage fracture resistance data in terms of the J-integral at cleavage instability, Jc. The experimental results show a potential effect of specimen span on Jc-values which can help mitigating the effects of constraint loss often observed in smaller fracture specimens. An exploratory application to determine the reference temperature, T0, derived from the Master Curve methodology also provides additional support for using non-standard bend specimens in routine fracture applications.
Rules for Flaw Interaction for Subsurface Flaws in Operating Pressurized Vessels: Technical Basis of Code Case N-877
Authors: Lacroix Valéry , Dulieu Pierre , Blasset Sebastien , Tiete Ralf , Li Yinsheng , Hasegawa Kunio , Bamford Warren , Udyawar Anees
Published: October 2018

When multiple flaws are detected in pressure retaining components during inspection, the first step of evaluation consists of determining whether the flaws shall be combined into a single flaw or evaluated separately. This combination process is carried out in compliance with proximity rules given in the Fitness-for-Service (FFS) Codes. However, the specific criteria for the rules on combining multiple flaws into a single flaw are different among the FFS Codes.

In this context, revised and improved criteria have been developed, to more accurately characterize the interaction between multiple subsurface flaws in operating pressure vessels. This improved approach removes some of the conservatism in the existing ASME Code approach, which was developed in the 1970s based on two flaws interacting with each other.

This paper explains in detail the methodology used to derive improved flaw proximity rules through three-dimensional FEM and XFEM analyses. After the presentation of the calculations results and the improved criteria, the paper also highlights the multiple conservatisms of the methodology using several sensitivity analyses.
Design and Application of an Equator Flexible Supported Acrylic Spherical Vessel for Neutrino Detector
Authors: Zhou Fan , Du Yang , Chen Zhiping , Hou Shaojing , Heng Yuekun
Published: October 2018

The second stage of the Daya Bay neutrino experiment, the Jiangmen Underground Neutrino Observatory (JUNO), will be launched to investigate more neutrino physics. The vessel, which is used to contain the liquid target for detecting neutrinos, plays a significant role in JUNO. It must meet diverse design criteria according to the requirements for physics measurement and safe operation. This paper proposed an alternative structural scheme for the containment vessel. Acrylic is selected as the material for its high transparency and excellent mechanical properties. A sphere 35.5m in diameter is chosen as the optimum shape of the vessel. The sphere is supported at its equator boss by beams and rods. And a rubber layer functions as buffer between acrylic and steel supporting structures to avoid rigid contact. The preliminary design of the scheme is given and verified by finite element analysis. Results show that this scheme can meet the requirements of strength and stability and should be a feasible choice for JUNO.
Assessment of the Fitness for Service of the Flamanville EPR Reactor Pressure Vessel Closure Head and Bottom Head Domes Containing a Segregation Zone Characterized by a High Carbon Content
Authors: Delvallée-Nunio Isabelle , Loiseau Olivier , Monhardt Daniel , Buiron Audrey , Dubois Franck
Published: October 2018

To complete the manufacturing process qualification of the closure head and bottom head domes of the Flamanville EPR RPV in 16MND5 ferritic steel (similar to A508 cl3), AREVA NP performed in 2014 material testing on a sacrificial dome so-called UA Sup. These tests revealed that the Charpy impact energy at 0°C — in the positive segregation zone at ¼ thickness — was lower than 60 J, the minimum value required by the French regulation. Thereafter, this result was explained by the high carbon content close to 0.3 % — against 0.18 % in the ladle — due to the forging process. The positive segregation was insufficiently eliminated to avoid high carbon content in certain location.

As the level of Charpy impact energy is an indicator of the level of fracture toughness, a thorough material characterization of the segregation zone, as well as a brittle fracture analysis have been proposed and carried out by AREVA NP to demonstrate that the Flamanville EPR RPV domes are tough enough for a safe operation.

The principles of the demonstration approach were reviewed by ASN and IRSN in 2015 and the final safety case was submitted to the ASN and IRSN review in December 2016. The latter led to the conclusion that, even if the segregation zone fracture toughness is lowered in comparison to that of the acceptance test zone, this does not put into question the Flamanville EPR RPV fitness for service as long as adequate in-service inspection of the domes is periodically performed.

This paper aims at presenting the key elements of the IRSN assessment from part of which this conclusion was drawn, namely the material testing program, the description of the loadings in normal and accidental conditions, and the brittle fracture analysis.
Relationship of Fracture Behaviours Between Full-Scale Pipe Bending and Small-Scale Toughness Tests
Authors: Park Dong-Yeob , Tajika Hisakazu , Sakimoto Takahiro , Igi Satoshi , Gianetto James A. , Liang Jie , Gravel Jean-Philippe , Kondo Joe
Published: October 2018

A comparison of the fracture behaviours for a full-scale (FS) pipe bending test and small-scale fracture toughness tests was carried out in this investigation. For the FS pipe test, two 4-meter long large diameter (914 mm) X70 pipes were girth-welded together to facilitate bend testing with an internal pressure of 72% of specified miniminm yield strength (SMYS). The test assembly also contained a semi-ellipical notch that was prepared by means of electrical discharge machining (EDM) from the outside surface in the heat-affected zone. Single-edge notched bend (SE(B) or SENB) and single-edge notched tension (SE(T) or SENT) test specimens were prepared from a duplicate girth weld produced with the same pipe and weld procedure with equivalent notch depths. The FS pipe test showed deformation along the pipe axis asymmetric to the girth weld centre. The comparison of fracture behaviours between small-scale and FS tests suggests that toughness measurements (crack-tip opening displacement or J-integral) at maximum load might be useful as a reference for strain-based design although further work is needed.