bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Method for Field Evaluation of Heat Treatment to Identify Vessels That Are Susceptible to Sulfide Stress Cracking
Authors: Ramirez Guillermo , Kenady Kollin , Jackson Joshua E. 
Published: October 2017

Inadequate heat treatment in the head and head-to-shell weld areas of a low-pressure separator vessel was determined to have led to conditions which allowed for the development of sulfide stress cracks, and ultimately resulted in rupture of the vessel. This determination was made through the use of destructive testing and failure analysis of the ruptured vessel. Generally, verification of vessel heat treatment is done through review of temperature recordings from manufacturing documentation or third party verification at the time of fabrication. Unfortunately, heat treatment records of pressure vessels are often misplaced, lost during acquisitions/mergers, or simply never existed.
Under the assumption that these vessels were adequately heat treated, the vessel’s owners do not normally take into consideration the high residual stresses which create favorable conditions for sulfide stress cracking (SSC) and other stress corrosion cracking type damage mechanisms. In this case, cold formation of the head resulted in high residual stresses in the flange and knuckle regions. The welds, which had not been properly post-weld heat treated, similarly had high residual stresses. These high stresses resulted in favorable conditions for the SSC to occur when exposed to a corrosive environment such as oil and gas operations.
In an effort to prevent similar events from occurring in the future, it was determined to be necessary to evaluate other vessels for inadequate heat treatment that may result in SSC. A non-destructive approach was investigated to evaluate vessels, especially in the absence of the aforementioned heat treatment records, to determine if the formed heads and heat affected zones after welding had adequate heat treatment. A method was developed to identify vessels without adequate heat treatment utilizing standard non-destructive testing techniques. There is the potential that many other low pressure vessels in lethal service could have received inadequate heat treatment. This methodology can therefore be used to determine the heat treatment state for these pressure vessels without destructive testing.
Shock Waves, Vibrations, and Resonance in Linearly Elastic Beams
Authors: Leishear Robert A. 
Published: October 2017

Equations can describe the stresses in linearly elastic simple beams, subjected to different types of suddenly applied, or dynamic, incident loads. The assumption of linearly elasticity simplifies the nonlinear aspects of structural vibrations. Simplified linear models are applicable to many vibration analyses, and provide significant insights into vibration behavior.
When a load impacts a beam, there are two different stresses created. The primary bending stress is the bending stress of the beam due to perpendicular loading. The secondary bending stress is a much higher frequency bending stress that travels along the surface of the beam relative to the moving load front. In general, the primary bending stress has a much larger magnitude than the secondary bending stress. The maximum stress values for the primary and secondary bending stresses may be described by dynamic load factors (DLF’s); where the maximum stress caused by an applied load equals the DLF multiplied by the static stress; and the static stress is the equilibrium stress for the load in question applied to the beam.
For example, consider the primary stresses due to a sudden pressure increase, which is applied perpendicular to a beam’s axis. The maximum stress in that beam is double the static stress, and deflection, that would be caused if that incident pressure is statically applied. That is, the DLF < 2 for a pressure that is suddenly applied over the incident surface of a beam: the maximum possible stress is twice the static stress.
Now consider the secondary stress. A localized bending stress occurs when a pressure wave travels parallel to the axis of a beam, and this bending stress has a DLF < 4. That is, a high frequency bending stress travels along the beam with a maximum magnitude equal to four times the applied pressure; the maximum stress is four times the static stress.
As other examples, stresses due to different types of loads may be evaluated. A gradually increasing pressure yields 1< DLF < 2, depending on the loading rates. A harmonically applied load may yield a DLF theoretically equal to infinity, but damping greatly reduces the maximum DLF. Also, these harmonic loads can significantly excite higher mode frequencies, i.e., the applied load may excite any one of a number of a structure’s natural frequencies. New theory is presented here to describe shock waves, suddenly applied loads, and resultant vibrations to coherently relate these complex quantities.
Microstructural Evaluation of 9Cr-3W-3Co-Nd-B Heat-Resistant Steel (SAVE12AD) After Long-Term Creep Deformation
Authors: Hamaguchi Tomoaki , Okada Hirokazu , Kurihara Shinnosuke , Hirata Hiroyuki , Yoshizawa Mitsuru , Iseda Atsuro 
Published: October 2017

The new ferritic heat-resistant steel composed of 9Cr-3W-3Co-Nd-B, registered as ASME Code Case 2839, has been developed for large diameter and heavy wall thickness pipes and forgings of fossil-fired power boilers. The steel, which contains 0.01 mass% boron, a small amount of neodymium, and optimized amounts of nitrogen, is characterized by the superior long-term creep strengths of both the base metal and welded joint. P92 had equiaxed subgrain structures changed from martensite lath structures and coarsened M23C6 type carbides after long-term creep. In contrast, the developed steel, SAVE12AD, maintained martensite lath structures with fine M23C6 along the boundaries even after the long-term creep stage. The addition of high amounts of boron suppressed the coarsening of M23C6 along the boundaries, thereby stabilizing the martensite lath structure in the base metal of the steel. Consequently, SAVE12AD had higher creep rupture strength than other high chromium ferritic steels.
To investigate the creep rupture strength of welded joints, two welded joints with Ni-based alloy and Grade 92 welding filler wires were prepared by automatic gas tungsten arc welding. The creep rupture strength of each welded joint showed small degradation compared with the base metal in the long-term creep stage over 10,000 hours. These were ruptured 1.5 mm away from the fusion line, which was the same area as Type IV cracking. Microstructural observations were carried out by electron back scatter diffraction analysis using simulated heat-affected zone samples at different peak temperatures from 750 °C to 1350 °C in order to clarify the microstructure in the heat-affected zone. No fine grain area was observed in the microstructure after the simulated heat-affected zone at 910 °C just above AC3 transformation temperature, although there were fine grains along prior austenite grain boundaries, which seemed to form with the diffusion transformation. The creep cracks seemed to have initiated from the fine grain structures, resulting in the rupture at the same area as Type IV cracking. However, the creep rupture strength degradation of the welded joints against the base metal was significantly smaller than that of conventional steel welded joints owing to the suppression of fine grains found in the heat-affected zone heated around AC3 temperature.
The developed 9Cr-3W-3Co-Nd-B steel (SAVE12AD) will be used for large diameter and heavy wall thickness pipes and forgings in 600 °C ultra super critical power plants.
Low-Damage Design Philosophy for Future Earthquake-Resistant Structures
Authors: Chouw Nawawi 
Published: October 2017

Current seismic design philosophy used worldwide tolerates a degree of damage at locations predefined by the designer, as long as a complete structural collapse is precluded. By accepting plastic deformations, the maximum acceptable forces can be controlled and construction costs can be reduced. Major earthquakes, e.g. the Canterbury earthquakes, showed that well-designed structures behave as anticipated. The joints suffered plastic deformation as the designer intended, while the occupants remained alive. Repair costs, however, were often high. Costs also accrue because, post-earthquake, the infrastructure is no longer fit for purpose. These costs are very difficult to predict.
Low-damage seismic design, in contrast, can be achieved by activating rigid-like body movement of structural members. Development of forces resulting from structural local deformation can then be prevented. Consequently, associated damage to structural members can be avoided. Recent research outcomes at the University of Auckland Centre for Earthquake Engineering Research will be presented.
Fundamental Study on Evaluation Method of Nonlinear Sloshing Wave Height of Cylindrical Tanks
Authors: Morita Hideyuki , Takata Tomosige , Madokoro Hideki , Sago Hiromi , Murakami Hisatomo , Yokoi Shinobu , Yamamoto Tomohiko 
Published: October 2017

When cylindrical tanks installed in the ground, such as oil tanks and liquid storage tanks, receive strong seismic waves, including the long-period component, motion of the free liquid surface inside the tank called sloshing may occur. If high-amplitude sloshing occurs and the waves collide with the tank roof, it may lead to accidents such as damage to the tank roof or outflow of internal liquid. Therefore, it is important to predict the wave height of sloshing generated by an earthquake input.
Sloshing is vibration of the free liquid surface, and when the sloshing wave height is small, it can be approximated with a linear vibration model. In that case, the velocity-response-spectrum method using velocity potential can estimate the sloshing wave height under an earthquake input. However, when the sloshing wave height increases and the sloshing becomes nonlinear, it is necessary to evaluate the wave height using other methods such as numerical analysis.
Taking into consideration that design earthquake levels tend to increase and the use of seismic isolation mechanisms has continued to spread in recent years, it is possible that the long-period components of an earthquake input which act on cylindrical tanks will also increase. Therefore, although it is thought that the evaluation of nonlinear sloshing wave height is important, there are few examples which quantitatively evaluate the wave height of nonlinear sloshing.
In this study, as a simple evaluation technique of a nonlinear sloshing wave height, the applicability of the correction coefficient proposed by Shimada et al. was examined based on the flow analysis which used Volume of Fluid (VOF) method. Moreover, it was studied that the VOF method can be used to evaluate nonlinear sloshing wave height and sloshing wave crest impact pressure acting on the fixed roof of a tank.
Shaking table tests will continue to be carried out in order to verify the applicability of the simple evaluation technique of nonlinear sloshing wave height. Results from flow analysis code will also be validated against these test results.
Modal Analysis of a Triangular-Pitch Bundle Subjected to Two-Phase Cross-Flow
Authors: Deri Enrico 
Published: October 2017

Flow-induced vibrations of tubes in two-phase heat exchangers are a concern for the nuclear industry. EDF has developed a numerical tool, which allows one to evaluate safety margins and thereafter to optimize the exchanger maintenance policy.
The software is based on a semi analytical model of fluid-dynamic forces and dimensionless fluid force coefficients which need to be evaluated by experiment. A test rig was presented in previous PVP conferences with the aim of assessing parallel triangular tube arrangement submitted to a two-phase vertical cross-flow: a kernel of nine flexible tubes is set in the middle of a rigid bundle. These tubes vibrate as solid bodies (in translation) both in the lift and drag directions.
This paper presents some extended physical analysis applied to some selected points of the aforementioned experiment series: the response modes are identified by means of operational modal analysis (i.e. under unmeasured flow excitation) and presented in terms of frequency, damping and mode shapes.
Among all the modes theoretically possible in the bundle, it was found that some of them have a higher response depending on the flow velocity and the void fraction. Mode shapes allow to argue if lock-in is present and to clarify the role of lift and drag forces close to the fluidelastic instability.
Simplified Assessment of Studs Allowing for Low Constraint Conditions
Authors: James P. , Madew C. , Jackson M. 
Published: October 2017

Defect tolerance assessments are carried out to support the demonstration of structural integrity for high integrity components such as nuclear reactor pressure vessels. These assessments often consider surface-breaking defects and assess Stress Intensity Factors (SIFs) at both the surface and deepest points. This can be problematic when there is a high stress at the surface, for example due to the stress concentration at the root of a screw thread. In the past this has led to the development of complex and costly 3D finite element analyses to calculate more accurate SIFs, and still resulting in small apparent limiting defect sizes based on initiation at the surface point.
Analysis has been carried out along with supporting materials testing, to demonstrate that the increased SIF at the surface point is offset by a reduction in crack-tip constraint, such that the material exhibits a higher apparent fracture toughness. This enables a more simplistic assessment which reduces the effective SIF at the surface such that only the SIF at the deepest point needs to be considered for many defects. This then leads to larger calculated limiting defect sizes. This in turn leads to a more robust demonstration of structural integrity, as the limiting defect sizes are consistent with the capability of non-destructive examination techniques.
An overview of the supporting materials testing is provided in an accompanying paper. The accompanying paper details how it was not possible to demonstrate the required material response with conventional tests, such as those using shallow-notched bend specimens. Instead it was necessary to develop modified specimens in which semi-elliptical defects were introduced into a geometry which replicated the notch acuity at the root of a screw thread. These tests were used to quantify the stud materials sensitivity to constraint. Conventional three-point bend tests were also seen to confirm these values.
A series of R6 constraint modified assessments have been considered to understand the benefit from including a loss of constraint, particularly when assessing the surface breaking SIF. This has necessitated a series of complex finite element analyses to define the elastic SIF as well as the elastic constraint parameter, T-Stress, T. Further verification analyses have also been performed to determine the equivalent elastic-plastic J and Q parameters. These have been used to provide guidance on how best to assess surface breaking defects within studs. This has shown that the increased perceived toughness at the surface location means that under the majority of conditions, the assessment can simply be based upon the SIF at the depth location using high constraint fracture toughness.
This paper provides an overview of the process undertaken to provide simplified guidance on assessing defects within studs that allows benefit from constraint loss.
ASME Code-Case Proposal to Explicitly Quantify the Interaction Between the PWR Environment and Component Surface Finish
Authors: Métais Thomas , Courtin Stéphan , De Baglion Laurent , Gourdin Cédric , Le Roux Jean-Christophe 
Published: October 2017

Fatigue rules from ASME have undergone a significant change over the past decade, especially with the inclusion of the effects of BWR and PWR environments on the fatigue life of components. The incorporation of the environmental effects into the calculations is performed via an environmental factor, Fen, which is introduced in ASME BPV code-case N-792 [5], and depends on factors such as the temperature, dissolved oxygen and strain rate.
Nevertheless, a wide range of factors, such as surface finish, have a deleterious impact on fatigue life, but their contribution to fatigue life is typically taken through the transition factors to build the fatigue design curve [2] and not in an explicit way, such as the Fen factor. The testing supporting the rules pertaining to Environmental Fatigue Correction Factor (Fen) Method in ASME BPV was performed on specimens with a polished surface finish and on the basis that the Fen factor was applicable without alteration of the historical practice of building the design curve through transition factors. The extensive amount of testing conducted and reported in References [2] and [7] (technical basis for ASME BPV current EAF rules) was used to propose a set of transition coefficients from the mean air curve to the design curve on one hand, and on the other hand to build a Fen factor expression, defined as the difference between the life in air and in PWR environments.
The work initiated by AREVA in 2005 [9] [10] [11] demonstrated that there is a clear interaction between the two aggravating effects of surface finish and PWR environment for fatigue damage, which was not experimentally tested in the References [2] and [7]. These results have clearly been supported by testing carried out independently in the UK by Rolls-Royce and AMEC FW [12]. These results are all the more relevant as most NPP components do not have a polished surface finish. Most surfaces are either industrially polished or installed as-manufactured.
It was concluded that this proposal could potentially be applicable to a wide range of components and could be of interest to a wider community. EDF/Areva/CEA have therefore authored a code-case introducing the Fen-threshold, a factor which explicitly quantifies the interaction between PWR environment and surface finish. This paper summarizes this proposal and provides the technical background and experimental work to justify this proposal.
European Standard on Small Punch Testing of Metallic Materials
Authors: Bruchhausen Matthias , Austin Tim , Holmström Stefan , Altstadt Eberhard , Dymacek Petr , Jeffs Spencer , Lancaster Robert , Lacalle Roberto , Matocha Karel , Petzová Jana 
Published: October 2017

Life extension of aging nuclear power plant components requires knowledge of the properties of the service-exposed materials. For instance, in long term service the tensile and creep properties might decline and the ductile-to-brittle transition temperature (DBTT) might shift towards higher temperatures. Monitoring of structural components in nuclear power plants receives much attention — in particular in the context of lifetime extension of current plants, where the amount of material available for destructive testing is limited.
Much effort has therefore been invested in the development of miniature testing techniques that allow characterizing structural materials with small amounts of material. The small punch (SP) test is one of the most widely used of these techniques. It has been developed for nuclear applications but its use is spreading to other industries.
Although the SP technique has been used for more than 30 years, there is currently no standard covering its most widely used applications. Within the auspices of ECISS TC 101 “Test methods for steel (other than chemical analysis)” WG 1 is currently developing an EN standard on the “Small Punch Test Method for Metallic Materials”. The standard will address small punch testing for the determination of tensile/fracture properties as well as small punch creep testing.
This paper gives an overview of the state-of-the art of the SP tests and describes the scope of the standard under development.
Assessment of the Influence of the Use of Weld Overlay As a Repair Method on the Stress Level of Bulged Sections of Coke Drums
Authors: Vivas Gabriel A. , Moret Armando J. , Bello Roberto E. , Melian Luis M. , Araque Egler D. 
Published: October 2017

Several studies recognized that cracks in delayed coke drums resulted from low cycle fatigue induced by cyclic thermal stress [1], [2], [3]. According to a coke drum survey coordinated by API in 1996 [1], there are two different areas where cracks are produced. The first zone is located at the shell to skirt weld, and the second at the bulged areas found in the cylindrical section. In the second case, from 145 coke drums 57% reported that had shell bulging problems. Of the drums that bulged, 87 % also showed cracks.
Recently, it has been reported the use of a novel weld repair procedure on bulged sections of a drum. In this repair, the bulge is overlaid with weld metal on the inside or outside on the bulge depending on the bulge shape. It has been reported that this repair procedure can stop further bulging on the shell, but detailed information about its influence has not yet been published.
Finite element analysis of several bulged patterns that were identified from some laser mappings are used to compare the level of the stress after a weld overlay repair is made. The study was carried out running a sequentially-coupled thermo-mechanical analysis. The assessment shows the influence of the thickness and the extent of the weld overlay on the level of stress on bulged coke drums. The results indicated that depending on the initial bulged shape this repair method either reduces or increases the level of the stress. When an inward deformation pattern is observed, an external reinforcement is recommended; however, when an outward deformation pattern is developed in a coke drum, an external weld overlay repair is not recommended.