bluuebunny/crossref_metadata_2025 huggingface dataset:
The relation between student motivation and student grades in physical education: A 3‐year investigation
Authors: Barkoukis V. , Taylor I. , Chanal J. , Ntoumanis N.
Published: January 2014

Enhancing students' academic engagement is the key element of the educational process; hence, research in this area has focused on understanding the mechanisms that can lead to increased academic engagement. The present study investigated the relation between motivation and grades in physical education (PE) employing a 3‐year longitudinal design. Three hundred fifty‐four Greek high school students participated in the study. Students completed measures of motivation to participate in PE on six occasions; namely, at the start and the end of the school year in the first, second, and third year of junior high school. Students' PE grades were also recorded at these time points. The results of the multilevel growth models indicated that students' PE grades increased over the 3 years and students had better PE grades at the end of each year than at the beginning of the subsequent year. In general, students and classes with higher levels of controlling motivation achieved lower PE grades, whereas higher levels of autonomous motivation were associated with higher PE grades. These findings provide new insight on the associations between class‐ and individual‐level motivation with objectively assessed achievement in PE.
The Differential Effects of Racially Homophilous Sponsorship Ties on Job Opportunities in an Elite Labor Market: The Case of NCAA Basketball Coaching
Authors: Seebruck Ryan , Savage Scott V.
Published: January 2014

We examine how an assistant coach's race and the race of his supervisor (the head coach) interact to affect future job quality. While past research argues that homophily is beneficial to job mobility, we find differential effects based on the race. OLS and OLR regression analyses on the quality of one's first head coaching job in NCAA men's basketball indicate that black assistant coaches working under black head coaches (black homophily) are significantly disadvantaged compared to all other racial combinations: white assistants with white supervisors (white homophily), white assistants with black supervisors (white heterophily), and black assistants with white supervisors (black heterophily). In contrast, there is no significant difference in job quality among the latter three groups: white homophily, white heterophily, and black heterophily. This indicates that while homophily is neither advantageous nor disadvantageous for whites, it is disadvantageous for black job candidates. This racially based disadvantage makes it difficult for minority job candidates to break through the glass ceiling and has real‐world financial implications.
Curating Inequality: The Link between Cultural Reproduction and Race in the Visual Arts
Authors: Blackwood Andria , Purcell David
Published: January 2014

Although the U.S. population is becoming more racially and ethnically diverse, research indicates that minority participation in the arts continues to decline. This article addresses the racial disparity of public art museum attendance by examining the role of the art museum curator and the process by which concepts of race are reproduced within the space of the public art museum. Utilizing Bourdieu's theories of cultural reproduction, social space, and symbolic power as a preliminary framework of inquiry, we examine the concept of whiteness as privileged social construct. Through face‐to‐face in‐depth interviews with museum curators, we investigate the means by which the dominant cultural narrative of whiteness is maintained through the preferences, decisions, and social interactions of curators. We draw upon critical white studies, a part of critical race theory, to underline the manner in which whiteness presents itself as a position of dominance. Our findings show that whiteness is maintained through the process of exclusion by presenting the white cultural narrative as both ordinary and invisible.
Identification of a novel HLA‐C*04 allele, HLA‐C*04:162
Authors: Wang D. , Gao S. , Xu Y. , He L. , Zhen J. , Zou H.
Published: January 2014

HLA‐C*04:162 differs from the closely matching allele C*04:01:01:01 by one nucleotide substitution in exon 4 at position 883 A/G.
Goodstart: a cluster randomised effectiveness trial of an integrated, community‐based package for maternal and newborn care, with prevention of mother‐to‐child transmission of HIV in a South African township
Authors: Tomlinson Mark , Doherty Tanya , Ijumba Petrida , Jackson Debra , Lawn Joy , Persson Lars Åke , Lombard Carl , Sanders David , Daviaud Emmanuelle , Nkonki Lungiswa , Goga Ameena , Rohde Sarah , Sitrin Deborah , Colvin Mark , Chopra Mickey
Published: January 2014

Background

Progress towards MDG4 for child survival in South Africa requires effective prevention of mother‐to‐child transmission (PMTCT) of HIV including increasing exclusive breastfeeding, as well as a new focus on reducing neonatal deaths. This necessitates increased focus on the pregnancy and early post‐natal periods, developing and scaling up appropriate models of community‐based care, especially to reach the peri‐urban poor.

Methods

We used a randomised controlled trial with 30 clusters (15 in each arm) to evaluate an integrated, scalable package providing two pregnancy visits and five post‐natal home visits delivered by community health workers in Umlazi, Durban, South Africa. Primary outcomes were exclusive and appropriate infant feeding at 12 weeks post‐natally and HIV‐free infant survival.

Results

At 12 weeks of infant age, the intervention was effective in almost doubling the rate of exclusive breastfeeding (risk ratio 1.92; 95% CI: 1.59–2.33) and increasing infant weight and length‐for‐age z‐scores (weight difference 0.09; 95% CI: 0.00–0.18, length difference 0.11; 95% CI: 0.03–0.19). No difference was seen between study arms in HIV‐free survival. Women in the intervention arm were also more likely to take their infant to the clinic within the first week of life (risk ratio 1.10; 95% CI: 1.04–1.18).

Conclusions

The trial coincided with national scale up of ARVs for PMTCT, and this could have diluted the effect of the intervention on HIV‐free survival. We have demonstrated that implementation of a pro‐poor integrated PMTCT and maternal, neonatal and child health home visiting model is feasible and effective. This trial could inform national primary healthcare reengineering strategies in favour of home visits. The dose effect on exclusive breastfeeding is notable as improving exclusive breastfeeding has been resistant to change in other studies targeting urban poor families.
Three-Dimensional Stress Intensity Factors for Ring Cracks and Arrays of Coplanar Cracks Emanating From the Inner Surface of a Spherical Pressure Vessel
Authors: Perl M. , Berenshtein V.
Published: January 2014

Certain spherical pressure vessels are composed of two hemispheres joined together by a girth weld. These vessels are susceptible to multiple cracking along the weld resulting in one or more cracks developing from the inner surface of the vessel and creating either a ring (circumferential) crack, or an array of coplanar cracks on the equatorial-weld plane. In order to assess the fracture endurance and the fatigue life of such vessels it is necessary to evaluate the Stress Intensity Factors (SIF) distribution along the fronts of these cracks. However, to date, only two solutions for the SIF for an internal ring crack as well as two 3-D solutions for a single internal semi-elliptical crack prevailing in various spherical pressure vessels are available. In the present analysis, mode I SIF distributions for a wide range of ring, lunular, and crescentic cracks are evaluated. The 3-D analysis is performed, via the FE method employing singular elements along the crack front. SIFs for numerous ring cracks of different depths prevailing in thin, moderately thick, and thick spherical vessels are evaluated first. Subsequently, Three-dimensional Mode I SIF distributions along the crack fronts of a variety of lunular and crescentic crack array configurations are calculated for three spherical vessel geometries, with outer to inner radii ratios of R0/Ri = 1.01, 1.1, and 1.7 representing thin, moderately thick, and thick spherical vessels. SIFs are evaluated for arrays of density δ = 0 to 0.99; for a wide range of crack-depth to wall-thickness ratios, a/t, from 0.025 to 0.95; and for various lunular and crescentic cracks with ellipticities, i.e., the ratio of crack-depth to semi-length, a/c, from 0.2 to 1.5. The obtained results clearly indicate that the SIFs are considerably affected by the three-dimensionality of the problem and by the following parameters: the crack density of the array – δ, the relative crack depth – a/t, crack ellipticity – a/c, and the geometry of the spherical vessel – η. Furthermore, it is shown that in some cases the commonly accepted approach that the SIF for a ring crack of any given depth is the upper bound to the maximum SIF occurring in an array of coplanar cracks, of the same depth, is not universal.
Spiral Wound Gasket Compressibility and Pressure Ratings
Authors: McCarthy John , Waterland A. Fitzgerald (Jerry) , Reid Dan
Published: January 2014

The industry practice of using pressure rating nomenclature to describe spiral wound gasket compressibility can contribute to some level of confusion regarding the proper design and selection of these gaskets. This situation can result in a misconception that a more easily compressed “soft” gasket (for example, “0–999 psi” rating) cannot be used in a higher pressure application. This is not necessarily true, and in many cases a softer (less dense) gasket construction can actually be beneficial in both high and low pressure applications. This article addresses both the terminology used to describe spiral wound gasket compressibility and the design characteristics of these gaskets in an effort to improve the understanding of this subject.
A Concept for Development of Hydrogen-Resistant Austenitic Steels
Authors: Gavriljuk Valentin , Shanina Bela , Shyvanyuk Vladyslav , Teus Sergey
Published: January 2014

Austenitic steels represent a promising class of engineering materials for hydrogen use in vehicles, e.g. for tanks and pipelines. This topic is analyzed in terms of the effect of alloying elements on the interatomic bonds in the solid solutions and, consequently, on the interaction between hydrogen atoms and dislocations and hydrogen embrittlement, HE. The effect of Cr, Ni, Mn, Mo, Si, Al, Cu, C, N was studied. It is shown that the physical reason for HE amounts to the hydrogen-caused increase in the concentration of free electrons in the austenitic solid solution. For this reason, the alloying with elements decreasing the concentration of free electrons is expected to improve resistance of austenitic steels to HE. Alloying with Cr, Mn, Mo and Si is shown to be useful, whereas Cu, Al, Ni, N assist hydrogen degradation. The role of Ni amounts only to stabilization of the fcc austenitic lattice and its absence or the decrease of its content in steel is desirable. Based on the obtained results, recommendations are made for design of austenitic steels with increased hydrogen resistance.
Numerical and Experimental Investigation of Flow-Acoustic Resonance of Side-by-Side Cylinders in a Duct
Authors: Mohany Atef , Arthurs David , Bolduc Michael , Hassan Marwan , Ziada Samir
Published: January 2014

The phenomenon of flow-excited acoustic resonance is a design concern in many engineering applications, especially when wakes of bluff bodies are encountered in ducts, piping systems, heat exchangers, and other confined systems. In this article, the case of self-excited acoustic resonance of two side-by-side cylinders in a duct with cross-flow is investigated both numerically and experimentally. A single spacing ratio between the cylinders, T/D = 2.5, is investigated, where D is the diameter of the cylinders and T is the center-to-center distance between them. The numerical investigation is performed using a finite-volume method at a Reynolds number of 30,000 to simulate the unsteady flow field, which is then coupled with a finite element simulation of the resonant sound field. The experimental investigation is performed using phase-locked Particle Image Velocimetry (PIV) during the occurrence of flow-excited acoustic resonance. The results of both methods reveal that the flow-excited acoustic resonance produces a strong oscillatory flow pattern in the cylinder wakes with strong in-phase vortex shedding being synchronized by the excited acoustic resonance. The distribution and strength of the aeroacoustic sources and sinks within the flow field have been computed by means of Howe’s theory of aerodynamic sound for both the experimental and numerical cases, with the results of the two methods comparing favorably, showing similar trends in the oscillating flow fields, and very similar trends in the distribution of net acoustic power.
Cyclic Fatigue in Metal Bellows
Authors: Stelmar Scott
Published: January 2014

Engineers who encounter the need for metal bellows expansion joints in piping and heat exchangers are often challenged by cyclic fatigue life calculation methods. ASME has published formulas for predicting low cycle fatigue life of metal bellows. Both B31.3 Appendix X and BPVC VIII Appendix 26 are similar in their approach, but are based on a data set generated in 1986 that produces excessively conservative results. Since that time, members of the Expansion Joint Manufacturers Association and others have provided additional data sets that allow further extension and accuracy of formulaic methods for calculating fatigue life. Additionally the experiments were designed to allow discrimination by various metal classes identifying superior alloys for bellows element performance. Major corrections are possible that will allow increased confidence and economy of design for those engineers that must adhere to the requirements of the American Codes.
Monitoring With Good Cause — Basic Principles and Current Status
Authors: Rothenhöfer Horst , Manke Andreas
Published: January 2014

With the interest in long term operation of nuclear power plants there is a growing interest in monitoring the degradation of a component. The intention is to prevent failures, leakages and incidents and thus enhance safety and reliability of a plant. While researchers are developing new sensors and technologies, there is a long tradition in fatigue monitoring in Germany and a growing number of plants in other countries is implementing that well-proven methodology.

This paper summarizes the current status and long-term experience of fatigue monitoring and explains the basic principles and benefits. It declares why fatigue has a special importance among other degradation mechanisms in a holistic approach. Fatigue monitoring is a combination of load monitoring and fatigue assessment methods.

More than 30 years of monitoring have revealed that unspecified loads and unexpected load cycles do occur in service that could violate the integrity of safety relevant components. The knowledge of real load histories not only results in realistic usage factors but empowers operators to optimize operation modes for preventing failures and reducing the annual increments of fatigue usage.

Numerous examples — such as leaking valves, unintended valve switching, fluctuating thermal stratification or water hammer — demonstrate that unintended or unexpected loads occur every now and then at different locations with different causes. To discover these loads immediately after occurrence means a direct feedback about root causes for degradation which is a valuable decision support for appropriate corrective or preventive actions.

Fatigue monitoring has proved to enhance safety and to generate significant economic benefits. Now it is time to make it an international standard.
Statistical Performance Evaluation of Soft (Elastomer) Seat Pressure Relief Valves
Authors: Gross Robert E. , Harris Stephen P.
Published: January 2014

Risk-based inspection methods enable estimation of the probability of failure on demand for spring-operated pressure relief valves at the United States Department of Energy’s Savannah River Site in Aiken, South Carolina. This paper presents a statistical performance evaluation of soft seat spring operated pressure relief valves. These pressure relief valves are typically smaller and of lower cost than hard seat (metal to metal) pressure relief valves and can provide substantial cost savings in fluid service applications (air, gas, liquid, and steam) providing that probability of failure on demand (the probability that the pressure relief valve fails to perform its intended safety function during a potentially dangerous over pressurization) is at least as good as that for hard seat valves. The research in this paper shows that the proportion of soft seat spring operated pressure relief valves failing is the same or less than that of hard seat valves, and that for failed valves, soft seat valves typically have failure ratios of proof test pressure to set pressure less than that of hard seat valves.
Master Curve and J-R Fracture Toughness of SA508/SA533-B-1 Weld and HAZ
Authors: Nanstad Randy K. , Chen Xiang , Sokolov Mikhail A. , Rabin Barry H. , Yang Ying
Published: January 2014

A large heat of low-alloy steel that met both specifications for SA508 Grade 3 Class1 forging steel and SA533 Type B Class 1 plate steel (A508/A533) was procured and used to fabricate a submerged-arc weldment for potential application in high temperature gas-cooled reactors. Compact specimens, 1TC(T), were machined from the weld metal and from the heat-affected-zone (HAZ) of the weldment. Tests of both materials were performed to obtain the fracture toughness reference temperature, To, using the Master Curve procedure of ASTM E-1921, and J-R curves to evaluate material behavior at various threshold temperatures in Code Case N-499-2 (2001) of the ASME Boiler and Pressure Vessel Code. Tests were performed at various temperatures up to 593°C. Unloading compliance was the primary technique used, although dc-potential drop was also monitored during the tests, and the normalization procedure of E1820 was used to compare the results from each procedure. Moreover, many tests at the highest temperatures were performed with no unloading and the normalization procedure provided in E1820 was used to analyze the load-displacement measurements. The fracture toughness for the HAZ is superior to that of the weld metal both in terms of transition temperature and ductile fracture toughness.
Outer Surface Prior to Inner Surface Double Autofrettage Technique for a Compound Cylinder
Authors: Abdelsalam Ossama R. , Sedaghati Ramin
Published: January 2014

The autofrettage and shrink-fit processes are used to enhance the load carrying capacity and fatigue life of the pressure vessels. Previous works were mainly concerned with increasing the compressive residual stress at the near bore area of the compound cylinders, ignoring the harmful high tensile residual stress developed at the outer part of the cylinder. Also, the idea of multiple or re-autofrettage had been only used at the inner surface of the cylinder to increase the magnitude of compressive residual stress at the near bore area. In this study, a new design approach is proposed by applying an autofrettage cycle on the external surface of the cylinder prior to an autofrettage cycle on the internal surface of the cylinder. It is shown that this double autofrettage cycle not only increases the magnitude of compressive residual stress at the near bore area but also decreases the tensile residual stress at the near outer surface area. Moreover, the proposed double autofrettage process has been combined with shrink-fit and standard inner surface autofrettage processes to produce new combinations of a two-layer compound cylinder. The fatigue life for these new combinations has been evaluated to verify the improvement while using the double autofrettage process.
Behavior of Compressive Residual Stresses in High Strength Steel Welds Induced by High Frequency Mechanical Impact Treatment
Authors: Khurshid Mansoor , Barsoum Zuheir , Marquis Gary
Published: January 2014

Residual stress state plays an important role in the fatigue life of welded structures. They can be beneficial or detrimental, depending on the nature of residual stresses. High frequency mechanical impact (HFMI) treatment is a post-weld fatigue improvement technique for welded joints. In this research work the behavior of compressive residual stresses induced in welded joints in high strength steels (HSS) by HFMI treatment has been investigated. Longitudinal non load carrying attachments in HSS are tested with constant amplitude (CA) and variable amplitude (VA) loading. Stress concentration factors have been calculated using Finite Element Analysis (FEA). Residual stresses have been measured at different cycles during fatigue testing using X-ray diffraction technique. It is observed that the induced residual stresses are quite stable with some relaxation in CA and VA loading. The overloads in VA loading seem to be more detrimental. Relaxation of residual stresses is more obvious in VA tests.
Protection Against Local Failure for Impulsively Loaded Vessels
Authors: Clayton Alan M. , Duffey Thomas A.
Published: January 2014

Significant changes were recently made in design limits for pressurized vessels in Section VIII, Division 3 of the ASME Code. There is now a local damage-mechanics based strain-exhaustion limit as well as a separate global plastic collapse limit. In addition, Code Case 2564 (Sec VIII, Div 3) has recently been approved to address impulsively loaded vessels. Recent studies have shown that local strain limits play a particularly important role for these impulsively loaded vessels. In this paper, the new local strain-exhaustion procedure, originally intended for static-pressure-loaded vessels, is evaluated for adequacy in conservatively predicting failure for impulsively loaded vessels. Based upon a symmetrically loaded cylindrical shell geometry, it is found that direct extension of the new local failure rules in the ASME Code to impulsively loaded vessels is unconservative. However, a hoop-strain local failure criterion predicts failures reasonably well.
Time Integration Method With Structure-Dependent Difference Equations
Authors: Chang Shuenn-Yih , Huang Chiu-Li
Published: January 2014

A novel family of structure-dependent integration method is proposed for time integration. This family method can have the possibility of unconditional stability, second-order accuracy and the explicitness of each time step. Since it can integrate the most important advantage of an implicit method, unconditional stability, and that of an explicit method, the explicitness of each time step, a lot of computational efforts can be saved in solving an inertial type problem, where the total response is dominated by low frequency modes and high frequency responses are of no interest.
Change Gasket: Overview and Recent Developments
Authors: Currie Russ
Published: January 2014

The paper discusses the development of sealing technology within the organisation with particular emphasis on the novel gasket (NG) referred to as Change.

The paper will introduce the concept and product; it will discuss the series of tests including comparison with four other gasket styles commonly used in the sealing industry. A brief summary of product development is under taken and sealing industry gasket constants and calculations are used to highlight the benefits of novel technology.
A Review of State-of-the-Art Methods for Pressure Vessels Design Against Progressive Deformation
Authors: Rohart Philippe , Hariri Saïd , Simonet Yves
Published: January 2014

Progressive plastic deformation is one of the damage mechanisms which can occur in pressure vessels subjected to cyclic loading. For design applications, the main rule proposed by codes against this failure mode is the so-called 3f (or 3Sm) criterion. During the last decade, studies have shown that this condition can be unreliable, and proposed to restrict its application. In parallel, theoretical developments enabled shakedown analyses to be considered as an interesting design methodology, and to be incorporated in codes and standards (EN13445, CODAP) from the early 2000′s. This paper gives a review of innovative methods based on shakedown theory, that can be used in the determination of elastic shakedown limits, ratchet limits, or cyclic steady state. These approaches are based on different concepts, such as elastic compensation (Linear Matching Method), Gockfeld theory (Uniform Modified Yield, Load Dependent Yield Modification), or the research of stabilized cycle (Direct Cyclic Analysis). Each method is presented and applied on a Benchmark example in Abaqus, and results are compared to reference data from codes. A final assessment focuses on accuracy and computation time, and underlines the benefits that could be expected for industrial applications.
A Methodology for Generation of Best-Estimate Pipeweld Failure Probabilities and Leak Rates for Pressurised Water (PWR) Reactor Plant
Authors: Wilson James , Heaton Elizabeth
Published: January 2014

This paper presents an overview of the work undertaken by Rolls-Royce to develop a methodology for the generation of best-estimate Pressurised Water Reactor (PWR) pipeweld failure probabilities and leak rates using the WinPRAISE software code.

WinPRAISE (the code) uses fracture mechanics principles to generate best-estimate pipeweld Probabilities of Failure (P(f)) by performing a monte-carlo statistical crack growth analysis. Calculation inputs include material properties and a detailed model of service loadings. Since the WinPRAISE default initial weld defect size distribution and frequency database is for MMA type welds, factors can be applied to the output to take credit for improved welding techniques such as automated TIG.

The leak before break philosophy for ductile PWR pipe materials has also been used to develop a criterion to determine an appropriate best-estimate initial through-wall crack geometry. The applied bending stress at the pipeweld and fluid mechanics principles can then be utilised to provide the corresponding initial leak rate. This model of initial through-wall crack geometry has resulted in a reduction in pipeweld initial leak rate estimates which benefits the probabilistic safety assessment for the applicable plant.

This paper presents the Rolls-Royce methodology for generation of best-estimate probabilities of failure and leak rates for PWR pipewelds based upon fatigue crack growth of welding defects.
Statistical Analysis and Monte-Carlo Simulations of Warm Prestressing of Pre-Cracked Small Single Edge Notch Bend Specimens
Authors: van Gelderen Derreck , Lauerova Dana , Posta Miroslav , Pistora Vladislav , Booker Julian , Smith David
Published: January 2014

Warm prestressing is widely acknowledged as being able to enhance material toughness, especially in steels that exhibit lower shelf cleavage fracture. The enhancement in toughness has a significant impact on the integrity of pressure vessels, particularly during severe loading conditions, such as pressurised thermal shock.

In this paper, we undertake detailed statistical analyses of experimental data provided via a comprehensive programme of fracture tests at UJV (Ústav jaderného výzkumu Řež a.s.). A warm prestressing model, developed by Chell, is used to predict the change in toughness probabilistically, using Monte-Carlo methods to predict the distribution in toughness following different warm prestressing cycles. The results obtained from this model are also compared to predictions made by the Wallin approach.

Experimental data was generated, at UJV for WWER 440 RPV steel, using small single-edge-notched bend SEN(B) specimens (or pre-cracked Charpy) across a range of different fracture temperatures, warm pre-stress temperatures, and levels of preload, in both as-received and irradiated conditions. In this paper, experimental data obtained only from tests on unirradiated specimens were statistically treated. A three parameter Weibull distribution was used to map the scatter observed in the virgin toughness. The statistical significance of increase in apparent fracture toughness due to warm prestressing was evaluated using the Mann-Whitney test. It was further shown by Monte-Carlo simulations that the Chell and Wallin models provide slightly conservative predictions of the resulting fracture toughness. Both, the experimentally measured and predicted values of the resulting fracture toughness, depend on the specific tests conditions, especially on the level of preload.
Technical Justification Supporting Operation With a Tube Installed in a Mis-Drilled Hole of a Steam Generator Tubesheet
Authors: Ruiz Roberto , Gomez Enrique , Wilson Robert M. (Con)
Published: January 2014

An evaluation is described for a tube with manufacturing induced bending, resulting from installation in a tubesheet mis-drilled hole. Considerations include manufacturing processes such as tube installation and tube expansion plus evaluations of the resulting tube stresses using ASME B&PV Code Section III rules. Also considered are operating issues such as potential interaction with neighboring tubes, tube vibration and wear, and the potential for accelerated tube corrosion. This is a companion paper to “ASME Section III Stress Analysis of a Heat Exchanger Tubesheet with a Misdrilled Hole and Irregular or Thin Ligaments”.
Failure Analysis of Corrosion Test Coupons and a Failed Tube From an Ethanol Vaporizer
Authors: Gilkey Mark H. , Kloos Rachel
Published: January 2014

Costly production losses at a production plant from failed ethanol vaporizers prompted further investigation into the cause of failure. Three corrosion test coupons from a vaporizer and a leaking tube from a second vaporizer were examined for evidence of corrosion damage and for the cause of damage.

Results suggest that sulfur in the water component of the product was a contributing cause of the corrosion in each case.
MOP, MAOP, DP and MAWP: Understanding the Differences to Avoid Unnecessary Costs
Authors: Aumuller John J. , Carucci Vincent A.
Published: January 2014

The ASME pressure vessel and piping codes and standards provide excellent references for code writers in international jurisdictions when developing their own national codes and for safety authorities when developing regulatory acts. The inclination to customize this effort may add unnecessary complexity that unintentionally obscures the underlying engineering principles.

In developing the Canadian pipeline code, the authors use the notion of maximum operating pressure or MOP similar to the MOP found in the ASME codes for pipelines. While the ASME code definitions are explicit and articulate, the MOP defined in the Canadian code is less so and has led to inadvertent confusion by industry users. Misunderstanding of complementary terminology used in ancillary ASME standards has contributed to further complexities. The use of the term, maximum allowable operating pressure or, MAOP in the ASME pipeline codes has further reduced clarity when integrating this term into international codes and regulatory acts.

This paper examines, in detail, some aspects of the Canadian pipeline code and illustrates via a representative case study some of the aforementioned difficulties that have arisen. These difficulties resulted in unnecessary derating of assets by imposing operational limits that were well below actual capacity. A clear explanation of the engineering principles underlying the provisions for codes which use a “design by rules” philosophy will help operators set appropriate limits for both static and dynamic loads that may not be apparent in the specific codes considered and will be expository for regulators and code users in general.
Advanced Inlay System for Inlet/Outlet Nozzles of RV for Preventive Maintenance Against Alloy 600 PWSCC in Japanese PWR Plants
Authors: Yamamoto Kazuhide , Kizawa Masahiko , Kawazoe Hiroki , Kobayashi Yuki , Onishi Ken , Hase Daisaku
Published: January 2014

Because many nuclear plants have been in operation for ages, the importance of preventive maintenance technologies is getting higher. One conspicuous problem found in pressurized water reactor (PWR) plants is the primary water stress corrosion cracking (PWSCC) observed in Alloy 600 (a kind of high nickel based alloy) parts. Alloy 600 was used for butt welds between low alloy steel and stainless steel of nozzles of Reactor Vessel (RV), Steam Generator (SG), and Pressurizer (Pz). As PWSCC occurred at these parts may cause Loss of Coolant Accident (LOCA), preventive maintenance is necessary. PWSCC is considered to be caused by a mixture of three elements: high residual tensile stress on surface, material (Alloy 600) and environment. PWSCC can be prevented by improving one of the elements. MHI has been developing stress improvement methods, for example, Water Jet Peening (WJP), Shot Peening by Ultrasonic vibration (USP), and Laser Stress Improvement Process (L-SIP). According to the situation, appropriate method is applied for each part. WJP has been applied for RV nozzles of a lot of plants in Japan. However PWSCC was observed in RV nozzles during the inspection before WJP in recent years, MHI developed the Advanced INLAY system to improve the material from Alloy 600 to Alloy 690. Alloy 600 on the inner surface of the nozzles is removed and welding with Alloy 690 is performed. In addition, heat treatments for the nozzles are difficult for its structural situation, so ambient temperature temper bead welding technique for RV nozzles was developed to make the heat treatments unnecessary. This paper describes the specifications of the advanced INLAY system and introduces the maintenance activities which MHI has applied for three plants in Japan by March 2012.
Coalesced Martensite in Pressure Vessel Steels
Authors: Pous-Romero Hector , Bhadeshia Harry
Published: January 2014

An alloy commonly used for large pressure vessels, known as SA508 Gr. 3, has a microstructure after heat treatment consisting of a mixture of tempered bainite and martensite at fast cooled regions near surfaces subject to water quenching. These two phases are conventionally recognised to consist of fine platelets, each of which is approximately 0.2 μm in thickness; enhancing strength and leading to good toughness properties.

We have discovered in our experimental work that there are circumstances where the adjacent platelets of a similar orientation can coalesce as the austenite transforms, to produce much coarser structures which are believed to be detrimental to toughness. An examination of published micrographs reveals that such coalesced regions existed but were not noticed in previous studies. The mechanism of coalescence is described and methods to ameliorate the coarsening are discussed.
Residual Stress Measurement in a Stainless Steel Clad Ferritic Plate Using the Contour Method
Authors: Naveed Nida , Hosseinzadeh Foroogh , Kowal Jan
Published: January 2014

In pressure vessels stainless steel weld-overlay cladding is a widely used technique to provide a protective barrier between the corrosive environment and the ferritic low alloy base metal. While the cladding layers enhance corrosion resistance, the induced residual stresses due to the deposition of weld layers are of major concern. It is of paramount importance to understand how residual stresses interact with service loading when the vessel is pressurized. Therefore, knowledge of the initial residual stresses due to cladding is an essential input for structural integrity assessment of pressure vessels.

In the present paper the Contour Method was conducted to measure residual stresses in an austenitic steel cladded plate that was fabricated from a ferritic steel base plate with three layers of austenitic stainless steel weld metal cladding deposited on the top surface. The Contour Method was chosen for various reasons. First, it provides a full 2D variation of residual stresses over the plane of interest. Second, it is not limited by the thickness of components or microstructural variations and finally it should potentially capture the variation of residual stresses in each individual weld beads and due to the possible phase transformation in the ferritic base material. The map of longitudinal residual stresses was measured by sectioning the test component along a transverse plane at mid-length. The measured residual stresses were in good agreement with published results in the open literature.
Experimental Investigation of Pulsatile Flow Through Prosthetic Heart Valves
Authors: Barannyk Oleksandr , Karri Satya , Oshkai Peter
Published: January 2014

Qualitative and quantitative flow visualization study was conducted for the case of a biomimetic pulsatile flow through an artificial heart valve placed into an asymmetric model of an aortic root with sinuses of Valsalva. A prototype trileaflet valve was tested alongside with a tilted disk valve and a bileaflet valve. The study was conducted in test conditions corresponding to 70 beats/min, 5.5 l/min target cardiac output and a mean aortic pressure of 100 mmHg. Flow visualization data obtained using digital particle image velocimetry (PIV) was phase-averaged in order to provide accurate, time-resolved patterns of flow velocity and viscous shear stress values. In the case of the tri-leaflet valve, during systole, a stable jet emanates from the valve, with vortical structures forming on the sides of the jet. These vortical structures entrain the surrounding fluid into the jet, which leads to development of a shear flow instability downstream of the valve. For all considered valve types, a recirculating flow was observed in the sinus area during both the systole and the diastole. No indication of a stagnating flow region was observed, as the fluid was completely washed out from the aortic sinus within each cardiac cycle.
FEM Calculations and Evaluation of Sealing Performance in Comparison of Raised Face and Flat Face Flange Connections
Authors: Kurosawa Ryou , Sawa Toshiyuki , Omiya Yuya , Kobayashi Takashi , Temma Kentaro
Published: January 2014

The bolted connections inserting gasket such as circular flange connections have been widely used in mechanical structures, which is nuclear and chemical industry, and so on. They are usually used under internal pressure. And they are required the high sealing performance. In the circular flange with non-asbestos compressed sheet gaskets, the two flange surfaces, raised-face and flat-face, are used. The raised-face flange on the sealing performance is examined by many researchers and reported. The flat-face is well known that flange rotation is smaller than that in raised-face flange under the internal pressure. However the sealing performance of the flat-face flange connection isn’t examined. Thus, the sealing performance of the flat-face flange connection is not examined. In this paper, the contact gasket stresses of these connections under internal pressure are analyzed using the finite element method (FEM) of each flange surfaces, taking into account a hysteresis in the stress-displacement curve of the gasket. And then, using the contact gasket stress distributions obtained from FE analysis and the relationship between gasket stress and leak rate obtained from a gasket sealing test (JIS B2490), method for estimating an amount of leakage is examined. The leakage tests were also conducted to measure an amount of gas leakage using an actual circular flange connection with a gasket. The estimated results are in a fairly good agreement with the experimental results.
Flaw Criticality Assessment for Core Spray Sparger Support Bracket Shroud Cracking
Authors: Vecchio Robert S. , Gosselin Stephen R. , Wolfe Ken
Published: January 2014

Stress corrosion cracking (SCC) has been observed in the weld joining the core spray sparger bracket to the core shroud at a number of Boiling Water Reactors (BWRs). The cracking occurs preferentially on the shroud side of the weld and has typically been detected with visual inspections. Limited ultrasonic (UT) inspections have been performed at selected plants. EPRI BWRVIP investigations showed that the cracks are relatively shallow and oriented in the radial direction (with respect to the shroud). This report documents results of a project performed by LPI (Lucius Pitkin, Inc.) whose objective was to develop a generic fitness-for-service evaluation for the observed cracking.

Deterministic SCC crack growth calculations were performed associated with cracking observed in the field. The extent of crack growth was based on the 95 percentile K-dependent the crack growth rate (da/dt) relationship for the BWR shroud materials identified in BWRVIP 14A [1]. The calculations also considered the changes in material properties and crack growth rates as the crack extends beyond the weld HAZ within the shroud thickness. The results demonstrate that the cracking is essentially benign and that extraordinary efforts to characterize fully the cracking are unwarranted. These results will be used as part of the technical basis for revised BWRVIP guidance for inspection of the sparger brackets.
Interaction and Assessment of Multiple Local Wall Thinning Defects
Authors: Peng Jian , Zhou Changyu , Dai Qiao
Published: January 2014

The safety assessment of pipes with multiple local wall thinning defects (LWTs) is systematically investigated by finite element analyses (FEA) with special attention to the interaction of multiple LWTs. It is interesting that the arrangement of LWTs (axial arrangement and circumferential arrangement), the load condition (pure pressure, pure bending and complicated load) and the relative depth play important roles in the interaction of multiple LWTs. The effective stress area and critical stress can be used to explain their influences. Moreover, existing assessment methods of multiple LWTs in some defect assessment standards such as API 579/ASME FFS, ASME B31G, BS 7910 and GB 19624 are reviewed. It’s noticed that the influences of arrangement, load condition and relative depth are ignored in existing standard methods, but they can influence the assessment results significantly. In order to consider these issues, an improved assessment of multiple LWTs based on API 579/ASME FFS is proposed. This improved assessment method has considered the influences of arrangement, load condition and relative depth, and can give better results.
Study on In-Flow Fluidelastic Instability of Circular Cylinders Caused by Air Cross Flow (Triangular Arrays)
Authors: Nakamura Tomomichi , Fujita Yoshiaki , Sumitani Takuya , Hagiwara Shinichiro
Published: January 2014

The in-flow instability of cylinder arrays corresponds to the in-plane instability of U-bend tubes in steam generators. This rarely occurring phenomenon has recently been observed in a nuclear power plant in U.S.A. For this reason, the importance of studying this instability has recently increased.

The fluidelastic instability of a cylinder array caused by cross-flow was found to easily occur in air-flow and hardly in water-flow in our previous report. The present report introduces the results of this phenomenon in several patterns of triangular cylinder arrays in air-flow. The pitch spacing between cylinders is one of the parameters, which varies from P/D = 1.2 to 1.5, for a five-by-five cylinder array. The instability is examined both in the in-flow direction and in the transverse direction. The test cylinders are supported with thin plates to move in one direction. The number and the location of the flexibly supported cylinders are the other parameters.

Differences between the instability in the in-flow and in the transverse direction are found. Among these differences the most important is the fact that the fluidelastic instability has not been observed for a single flexible cylinder in the in-flow direction, although it is observed in the transverse direction.

However, the in-flow instability can be estimated with the Connors’ type formula as in the transverse direction.
Evaluation of Creep-Fatigue Damage Based on Simplified Model Test Approach
Authors: Wang Yanli , Li Tianlei , Sham T.-L. (Sam) , Jetter Robert I.
Published: January 2014

Current methods used in the ASME Code, Subsection NH for the evaluation of creep-fatigue damage are based on the separation of elevated temperature cyclic damage into two parts, creep damage and fatigue damage. This presents difficulties in both evaluation of test data and determination of cyclic damage in design. To avoid these difficulties, an alternative approach was identified, called the Simplified Model Test or SMT approach based on the use of creep-fatigue hold time test data from test specimens with elastic follow-up conservatively designed to bound the response of general structural components of interest. A key feature of the methodology is the use of the results of elastic analysis directly in design evaluation similar to current methods in the ASME Code, Subsection NB. Although originally developed for current material included in Subsection NH, recent interest in the application of Alloy 617 for components operating at very high temperatures has caused renewed interest in the SMT approach because it provides an alternative to the proposed restriction on the use of current Subsection NH simplified methods at very high temperatures.

A comprehensive review and assessment of five representative simplified methods for creep-fatigue damage evaluation is presented in Asayama [1]. In this review the SMT methodology was identified as the best long term approach but the need for test data precluded its near term implementation. Asayama and Jetter [2] is a summary of the more comprehensive report by Asayama [1] with a summary of the SMT approach presented by Jetter [3].

In this paper, the previously documented development of the SMT approach and applicable restrictions are discussed and reviewed; the design of the SMT specimen, measurement issues and constraints are presented; the test apparatus and measurement system is described; initial test results and their application to a prototypic design curve are presented; and further testing and analysis for ASME Code incorporation are discussed.
Acoustic Emission Test of Pressure Vessel Leakage
Authors: Zhang Zhongzheng , Liang Hua , Ye Cheng , Cai Wensheng , Jiang Jun
Published: January 2014

In order to study acoustic emission (AE) signals characteristics of pressure vessel leakage, several cases of common in-service pressure vessel with leakage failure such as seal leakage, pitting corrosion perforation and safety valve leakage were tested by AE technology. Through statistical parameters of AE signals and waveform analysis on leakage process, the distribution characteristics of the AE hits, amplitude and frequency etc. were summarized on the different forms of leakage failure. The study will provide a reference for the device parameter configuration, sensor selection and estimation of the failure mode on in-service pressure vessel leakage.