bluuebunny/crossref_metadata_2025 huggingface dataset:
Bank Opacity and Safe Asset Moneyness
Authors: KIM SANG RAE
Published: November 2024

A bank is more effective as a supplier of money‐like safe assets when (i) its return on equity (ROE) is relatively lower and (ii) it is relatively more opaque about its balance sheet. A model is presented to support this, emphasizing that safe asset investors focus on the left tail of the collateral value distribution. Empirical tests on dealer banks and money market mutual funds' (MMFs') funding relationships confirm that higher ROE leads to MMF withdrawal due to lower moneyness of safe assets. Bank opacity mitigates the strength of this relationship, making it optimal for the banking system to maintain a certain level of opacity.
Can Transcriptomics Elucidate the Role of Regulation in Invasion Success?
Authors: Vaughan Amy L. , Dhami Manpreet K.
Published: November 2024

When a species invades a novel environment, it must bridge the environment–phenotype mismatch in its new range to persist. Contemporary invasion biology research has focused on the role that trait variation and adaptation, and their underlying genomic factors, play in a species' adaptive potential, and thus facilitating invasion. Empirical studies have provided valuable insights into phenotypes that persist and arise in novel environments, coupled with ‘omics tools that further the understanding of the contributions of genomic architecture in species establishment. Particularly, the use of transcriptomics to explore the role of plasticity in the initial stages of an invasion is growing. Here, we assess the role of various mechanisms relating to regulation and functional adaptation (often measured via the transcriptome) that support trait‐specific plasticity in invasive species, allowing phenotypic variability without directly altering genomic diversity. First, we present a comprehensive review of the studies utilising transcriptomics in invasion biology. Second, we collate the evidence for and against the role of a range of regulatory processes in contributing to invasive species plasticity. Finally, we pose open questions in invasion biology where the use of transcriptome data may be valuable, as well as discuss the methodological limitations.
On the Notion of ‘Factor of Production’ in Economic Theory
Authors: Fratini Saverio M.
Published: November 2024

In the marginalist view, production results from the services of the factors, with wages, rent and interest understood as rewards for their contributions. The principle of marginal productivity provided a logical foundation for this idea; but this mechanism requires factors measured in ‘technical units’, so it cannot be used when capital is understood in value terms. The theory then shifted towards a Walrasian conception with heterogenous capital goods and fixed‐coefficient methods. Initially, some scholars believed this approach could be consistent with viewing distribution variables as rewards for factor contributions. The capital theory controversy revealed that this is not the case.
Aedes aegypti control in breeding sites through an insecticidal coating with dual effect: Laboratory trials and safety assessment
Authors: Cárdenas Rocio , Cabrera Olga L. , Carrillo Maria A. , Pineda Alejandra , Ahumada Martha L. , Yañez Yohana , Ismail Hanafy , Paine Mark , Rivera Tatiana , Kroeger Axel
Published: November 2024

Ground water tanks are known to be preferred Aedes aegypti oviposition places providing opportunities for adult and larvae control. Therefore, a dual‐effect insecticidal coating (IC) (alphacypermethrin/ pyriproxyfen) with a slow‐release mechanism and safe for users could be applied within Aedes spp. breeding sites, representing a promising option. Bioassays were designed to determine the mortality and sterilizing effects on gravid mosquitoes exposed to IC. The effect of inhibition of emergence was evaluated in eggs, larvae and pupae exposed in different containers. For the water safety assessment concentrations of active ingredients were determined by reverse phase high performance liquid chromatography (RP‐HPLC) and the health risk was calculated. The IC applied to the interior walls of water‐holding containers showed efficacy against Ae. aegypti in terms of high gravid‐female mortality (81% at 24 h, p < 0.01), sterilizing effect (inhibition of oviposition by 63%, p < 0.01) and emergence inhibition (100% in eggs, L3 and L4; 97% in pupae). The offspring rate was reduced [only 0.15 (38/250) new adults emerged per exposed gravid females as against 11.90 per unexposed female (2976/250) at baseline]. Emergence inhibition was recorded up to 12 months and adult mortality >80% up to 6 months. The use of water stored in treated containers, either for washing or drinking, is not expected to pose a health risk to users. IC applied to domestic water containers has dual and complementary action that reduces Ae. aegypti densities (immature and adult stages). This represents baseline information for a cluster randomized efficacy trial in Colombia.
How scholars can support government analytics: Combining employee surveys with more administrative data sources towards a better understanding of how government functions
Authors: Rogger Daniel , Schuster Christian
Published: November 2024

With the digitization of administrative systems, governments have gained access to rich data about their administrative operations. How governments leverage such data to improve their administration—what we call government analytics—will shape government effectiveness. This article summarizes a conceptual framework which showcases that data can help diagnose and improve all components of a public administration production function—from inputs such as personnel and goods, to processes and management practices, to outputs and outcomes. We then assess to what extent public administration scholarship analyses these data sources and can thus inform government analytics. A review of 689 quantitative articles in two public administration journals in 2013–2023 finds that 50% draw on surveys of public employees and 25% on surveys of citizens or firms. By contrast, administrative micro data (14% of articles) are underexploited. Practitioners and scholars would thus do well to expand the data sources used to inform better government.
Quality competition between traditional and online sellers
Authors: Choi Yoonho , Choi E. Kwan
Published: November 2024

As consumers respond to technological changes, the market share of online sales has seen a significant increase, imposing continuous challenges on traditional sellers. This paper investigates how online sellers affect the quality of traded products in developed countries. Traditional sellers' products imported from developing countries are subject to tariffs, but online sellers bypass them due to de minimis rule. Entry of online sellers may force the traditional sellers to lower their product quality. Under certain conditions, the quality of the online sellers' products might be higher than that of the traditional seller. A rise in the import tariff may force the traditional seller to exit the market. However, if de minimis rule is abolished, the product quality of the traditional seller rises, but that of the online sellers falls.
An Investigation of Dynamic Behavior of Electric Vehicle Gear Trains
Authors: Donmez Ata , Kahraman Ahmet
Published: November 2024

The automotive industry has been experiencing a significant transition toward electrified powertrains in recent years. A torsional model of a common type of electric vehicle (EV) drivetrains is proposed to demonstrate certain dynamic behaviors that are unique to such high-speed applications. This two-stage helical gear drive train is supported by three shafts and connects the electric motor to the vehicle axle. The gear mesh interfaces are modeled by periodically time-varying stiffnesses subjected to backlash and displacement excitations to represent gear tooth errors and modifications. In addition to these internal excitations, torque fluctuations caused by electric motor are included as the external excitations. Two different operating conditions are studied here: (i) steady-state response as the vehicle is operated under steady torque conditions and (ii) transient response during EV system transitions between the drive and regenerative (regen) braking modes of operation. The torsional model predictions are verified through comparisons to simulations from a deformable-body contact model. Parameter sensitivity studies are performed to demonstrate nonlinear behavior of a helical gear train caused by external torque fluctuations as well as the interactions between external and internal excitations. Finally, drivetrain structural modes are shown to respond to drive-regen transitions resulting in certain transient (vibro-impact) behavior with elevated dynamic mesh forces.
Study on Vertical Sloshing Load Acting on Roof of Cylindrical Tanks Under Seismic Wave Excitation
Authors: Ikesue Shunichi , Iwasaki Akihisa , Sago Hiromi , Yokoi Shinobu , Yamamoto Tomohiko
Published: November 2024

During an earthquake, sloshing occurs in a cylindrical tank when a frequency component close to the natural frequency of sloshing is included in the seismic wave. When high amplitude sloshing occurs, the free liquid surface collides with the roof of the tank. Therefore, in tank design, it is important to evaluate the sloshing load acting on the roof.

In a previous study, we proposed a predictive evaluation method of the vertical load acting on the roof of cylindrical tank. The method consists of a nonlinear sloshing model and an impact pressure model, assuming sinusoidal excitation by sloshing natural frequency. Except for some special cases, this method almost agreed with test results and CFD (Computational Fluid Dynamics) analysis, in sinusoidal excitation.

In this study, we extended this method to deal with seismic wave excitation. In seismic wave excitation, the tank is excited by irregular wave, and the phenomenon of sloshing becomes more complicated than sinusoidal excitation. To simplify this complicated phenomenon, we proposed a new concept of equivalent growth wavenumber. This number represents the magnitude of the increase in the peak of liquid surface level during seismic wave excitation. We proposed a method to quantitatively evaluate this number from seismic response analysis. In addition, we proposed a method to evaluate the vertical load on the roof during seismic wave excitation, by introducing this number into the predictive evaluation method.
Structural Integrity Evaluation of 3D Printed Graphene-Reinforced PLA Notched Plates Using Failure Assessment Diagrams
Authors: Cicero Sergio , Arrieta Sergio , Sanchez Marcos
Published: November 2024

Failure Assessment Diagrams (FADs) constitute a well-known structural integrity evaluation tool that allows structural components containing crack-like defects to be assessed through a simultaneous analysis of fracture and plastic-collapse processes. FADs are included in the most recognized structural integrity assessment procedures/standards, such as BS7910 and API 579/ASME FFS-1, and their use is generally limited to metallic components containing crack-like defects.

On the other hand, 3D printed composites, and particularly those obtained through FFF (Fused Filament Fabrication), are assuming structural responsibilities beyond their most extended use as prototyping materials. The resulting structural components may contain notch-type defects (e.g., grooves, corners, holes, etc.) that determine their corresponding structural integrity. Thus, it is necessary to define structural integrity assessment criteria for this kind of materials when containing any kind of stress risers, beyond crack-like defects.

This work justifies the use of BS7910 Level 1 FAD, coupled with a notch correction derived from the Theory of Critical Distances (TCD), to analyze graphene-reinforced PLA plates subjected to pure tensile loading conditions and containing notches. The results reveal that the assessment points representing the plates at failure are located within the FAD area corresponding to unsafe conditions, providing conservative evaluations with moderate safety margins.
Pretest Modeling a Spent Nuclear Fuel Seismic Shake Test
Authors: Klymyshyn Nicholas , Kadooka Kevin , Barrett Nathan , Spitz Casey
Published: November 2024

The U.S. Department of Energy Spent Fuel and Waste Science and Technology (SFWST) program is planning to conduct a series of full-scale shake table tests to simulate hypothetical earthquake conditions and record the response of surrogate spent nuclear fuel (SNF) assemblies in a dry canister storage system mockup. The shake table motions will represent a range of hypothetical earthquake conditions at hypothetical locations in the continental U.S. to generally define the range of mechanical loads that SNF can be expected to experience during extended dry storage periods. This paper describes the pretest predictions made with LS-DYNA models of the mockup storage systems.

The test will use two dry storage system configurations, a mockup vertical concrete cask (VCC) and a mockup horizontal storage module (HSM). The test will use a production-quality canister and basket. Within the canister will be four instrumented fuel assemblies with fuel rods containing surrogate mass and 28 instrumented dummy assemblies that are intended to match the mass and outer dimension of a fuel assembly. The finite element models include models of the VCC and HSM on the shake table to calculate the system level dynamic responses and separate single fuel assembly models to calculate stress and strain in fuel assembly components. Both types of models include nonlinear behavior like rod-to-rod contact and the ability for VCC’s to rock and slide.

This paper presents the expected response of the VCC, HSM, and fuel assemblies to the shake table testing that is planned to start in April of 2024. The earthquake conditions represent seismic hazards in the 2,000-to-20,000-year return period range. The test data is expected to confirm the expectation based on the presented analyses that fuel rod cladding will remain intact, fuel assembly structural components like guide tubes will remain intact, and no significant VCC sliding or tipping will occur in the range of conditions to be tested with the shake table.
NUCOBAM Project, Nuclear Components Based on Additive Manufacturing
Authors: Leopold Gaëlle , Bourgeois Myriam
Published: November 2024

NUCOBAM project aims at developing the qualification process and providing the evaluation of the in-service behavior allowing the use of Additively Manufactured (AM) components in a nuclear installation. Once qualified, the use of AM will allow nuclear industry to (1) tackle component obsolescence challenges and (2) manufacture and operate new components with optimized design in order to increase reactor efficiency and safety. To make this ambition a success, NUCOBAM will conduct the required studies to implement AM process in nuclear design codes and standards to produce nuclear reactor components.

The first part consists in characterization of the materials manufactured by Laser Power Bed Fusion (L-PBF) process in order to establish a qualification and codification methodology. The second part is dedicated to the evaluation of AM material behavior in-service, especially regarding the main degradation mechanisms that occur in LWR (thermal ageing, irradiation, ...). Materials are manufactured and some of them are then submitted to post-treatment (heat treatment or high isostatic pressure). Results are analysed and compared with existing approved manufacturing processes by design codes. This work will lead to evaluate and to deduce the main parameters required for specification.

The consortium thus involves electricity utilities, operating nuclear assets, component manufactures, design owners, public service experts in nuclear and radiation risks as well as research and competence centres involved in mechanical assessment, metal powder qualification, metallurgical characterization, materials irradiations capabilities and nuclear power research.
Study of Crack Initiation and Fracture Toughness Evaluation in JIC Testing of Linepipe Steel Under Gaseous Hydrogen Environment
Authors: Nishihara Yoshihiro , Inoue Ryuichi , Okano Hiroshi , Sakimoto Takahiro
Published: November 2024

Hydrogen is one of the promising energy carrier for achieving the carbon neutral society. The pipeline system is positioned as a major infrastructure indispensable for mass transportation of gaseous hydrogen. Material degradation in hydrogen embrittlement is considered in the hydrogen pipeline code ASME B31.12. The fracture toughness is required to be obtained by the test based on ASME BPVC sec.8 div.3. However, most of the line pipes have low strength and high toughness, so the evaluation by the above method is not suitable from the viewpoint of specimen size and mechanical constraint. Therefore, evaluation of fracture toughness by elastic-plastic fracture toughness test has become common. On the other hand, current standards for elastic-plastic fracture toughness tests, such as ASTM E1820, are based on the premise of conducting tests under atmospheric conditions, and do not consider ductility reduction and crack initiation mechanism changes caused by hydrogen entering steel under hydrogen gas conditions. In this study, the effects of hydrogen and test conditions on the crack initiation limit in JIC tests were investigated, and a method for evaluating the toughness value based on the fracture behavior of specimens under hydrogen gas environment was examined. Focusing on the fact that the stretched zone width (SZW) which is formed at the leading edge of a fatigue pre crack as a trace of plastic deformation just before a stable crack is initiated, in hydrogen gas was shorter than in air, when the fracture toughness (JSZ) obtained from SZW was defined as a value corresponding to the fracture phenomenon, the value obtained from the J-R curve according to the standard was overestimated for JSZ. In order to properly evaluate the fracture toughness value in hydrogen gas more efficiently considering the man-hour required for SZW measurement by fracture surface analysis, a method using J-R curve and blunting straight line prepared in the region of short crack growth was proposed.
Long-Term Creep Strength Evaluation of Welded Joint of ASME Grade 91 Type Steel
Authors: Yaguchi Masatsugu
Published: November 2024

Creep rupture data of welded joints of ASME Grade 91 type steel were collected by the Assessment Committee on Creep Data of High Chromium Steels, which consists of the Federation of Electric Power Companies of Japan, material producers, power plant manufacturers, and institutes in Japan, and the creep rupture life curve of the material was evaluated using the latest dataset to examine the validity of the long-term creep rupture life curves determined by the committee in 2015. The evaluation of the welded joints of Grade 91 type steel is the fourth time in Japan, as similar studies were conducted in 2004, 2010, and 2015. Creep rupture strength was re-evaluated with emphasis on the long-term creep rupture data obtained after the 2015 study, in which the rupture time in new data was up to about 100,000 h. It was found that the evaluation formula for the welded joints of Grade 91 type steel proposed in 2015 can be used for the appropriate evaluation of the new long-term data of the material. The creep curves calculated using the 2015 evaluation formula were also compared with the results of creep strength analysis under actual service conditions obtained using creep data of a long-term used material, and it was shown that they were in agreement with reasonable precision. Therefore, it was suggested that the 2015 evaluation formula for the welded joints of Grade 91 type steel is valid in the long-term region; thus, there is no need to revise it.
Mode I and Mode II Stress Intensity Factors for a Slanted-Edge-Crack Affected by an Adjacent Horizontal Crack Under Remote Tension
Authors: Levy Cesar , Perl Mordechai , Ma Qin
Published: November 2024

Fracture mechanics has been used in Fitness-for-Service assessments of structures containing cracks. The stress intensity factors (SIFs) at the crack tip are the key information in assessing the remaining service life of a cracked component. Extensive studies have been carried out on the mutual influence of adjacent parallel cracks. However, to date no solutions are available for non-parallel cracks. In the present analysis mode I (KI) and Mode II (KII) SIFs of a slanted-edge-crack affected by an adjacent non-parallel horizontal crack are obtained. KI and KII are evaluated for a wide range of the slanted edge crack angle β = 0° to 75°, for various normalized horizontal (S/a2 = −0.4 to 2) and vertical (H/a2 = 0.4) separation distances and for several crack lengths. The problem is solved using a 2-D, plane strain, finite element model, which was successfully validated against presently available solutions. It is found that the presence of the embedded crack always amplifies KI of the edge crack while KII might be either amplified or attenuated depending on the crack configuration. Furthermore, the present results indicate that, for the purpose of Fitness-for-Service, the effective SIF at the tip of the slanted crack always increases due to the presence of the embedded crack.
Tank Bottom Settlement Evaluation
Authors: Nadarajah Chithranjan
Published: November 2024

Localized bottom settlement is a form of settlement on storage tank bottom which is generally made out of lap welded plates. Localized bulges, ridges or depression of the bottom plate can result in lap weld failure which could lead to a leak. Currently tank bottom settlement is evaluated using the procedures in API 653 [1]. However, this procedure tends to be conservative and there are many tanks in operation where the bottom settlement has exceeded the API 653 requirements. Generally, when the bottom settlement exceeds the API 653 criterion, the tank is evaluated on a case-by-case basis using a combination of inspection and numerical analysis to determine whether they are fit for service.

This paper examines the background to the development of the tank bottom settlement procedure in API 653 and two alternative procedures are provided which will result in higher allowable bottom settlement.
Effects of Hydrogen on Fatigue Life Properties of Cold-Rolled Metastable Austenitic Stainless Steels With Artificial Defects
Authors: Yamabe Junichiro , Hashiguchi Kento , Wada Kentaro
Published: November 2024

It is important to understand the effect of hydrogen on the fatigue properties of materials to ensure the safety and reliability of hydrogen components. In this study, a cold-rolled metastable austenitic stainless steel, JIS-SUS301, with a tensile strength of around 1.3 GPa was prepared and subjected to plane-bending fatigue tests in air at room temperature by using uncharged and H-charged plate specimens with a thickness of 2 mm. A drilled hole or a sharp notch was introduced at the center of the plate specimens to control crack initiation sites. The H-charged specimens were exposed to 100 MPa hydrogen gas at 270°C for 200 h. The results showed that in high-stress amplitude regimes, the fatigue life of the specimens with a drilled hole or a sharp notch was significantly degraded by hydrogen. In contrast, the fatigue limit of the specimens with a drilled hole, which was determined by the critical stress for crack initiation, was not degraded by hydrogen, or was slightly raised, while the fatigue limit of the specimens with a sharp notch, which was determined by the threshold stress for crack propagation, was not affected or was only slightly degraded by hydrogen. Although the effect of hydrogen on the fatigue limit differed between the drilled hole and sharp notch, the difference was not significant.
Pipeline Weld Radiographs Defect Detection Based on Improved YOLO V8
Authors: Ren Qingying , Dong Shaohua , Qian Weichao
Published: November 2024

Pipeline transportation is a crucial method for transporting oil and gas, and with the growing energy demand, the scale of oil and gas pipelines is expanding rapidly. Most of the oil and gas pipelines are joined together by welding. Weld defects often lead to significant safety accidents, making it essential to test the quality of the welds. Radiographic Testing (RT) is a widely used Non-Destructive Testing (NDT) technology. The manual inspection of weld negatives obtained by X-ray inspection is a common method for detecting weld defects, but it involves a heavy judgment workload, making it prone to misjudgment and omission. An enhanced algorithm based on YOLO V8 for identifying and localizing weld defects was proposed in this paper to address this issue. The Receptive Field Block (RFB) mechanism was introduced to enhance the network’s feature extraction ability by using different sizes of receptive fields. This approach aims to simulate the human visual system and reduce misleading image backgrounds for small object detection. The EIOU loss function, which considers the overlap area between the detection frame and the real frame, the distance from the center point, and the actual difference between the length and width of the sides, was employed to address the issue of the fuzzy definition of the aspect ratio. Meanwhile, a dataset of six types of defects, including round defects, strip defects, cracks, slag inclusion, incomplete fusion, and incomplete penetration, was established. The experimental results show that the mean average precision (mAP) of the improved YOLO V8 reaches 89.3% for six types of defects. Compared to advanced object detection algorithms like Faster R-CNN, YOLO V5, and the original YOLO V8, the improvements are 44.92%, 22.88%, and 1.4%. The method can accurately and quickly identify a wide range of pipe weld defects.
A New Stress-Intensity Factor Solution for an Internal Surface Crack in Spheres
Authors: Sobotka James C. , Lee Yi-Der , Cardinal Joseph W. , McClung R. Craig
Published: November 2024

This paper describes a new stress-intensity factor (SIF) solution for an internal surface crack in a sphere that expands capabilities for this common pressure vessel geometry. The SIF solution employs the weight function (WF) methodology that enables rapid calculations of SIF values. The WF methodology determines SIF values from the nonlinear stress variations extracted in the uncracked geometry, e.g., from service stresses and/or residual stresses. The current approach supports two degrees of freedom that denote the two crack tips located at the deepest location and the surface of the sphere. The geometric formulation of this solution enforces an elliptical crack front, maintains normality of the crack front with the free surface, avoids non-physical crack shapes with protruding “ears”, and supports two degrees of freedom for fatigue crack growth from an internal crack tip and a surface crack tip. The new SIF solution enables all spherical geometries with the exterior diameter greater than or equal to four times the thickness. This WF SIF solution has been combined with stress variations common for spherical pressures vessels: internal pressure on the interior surface, uniform tension on the crack plane, and bending on the crack plane. These stress variations facilitate solution usability. This work builds on earlier efforts for an external surface crack (PVP2021-61397[1]) and provides a comprehensive solution capability for spheres.

This paper provides a complete overview of this solution. We present for the first time the geometric formulation of the crack front that enables the new functionality and set the geometric limits of the solution, e.g., the maximum size and shape of the crack front. The paper discusses the bivariant WF formulation used to define the SIF solution and details the finite element (FE) analyses employed to calibrate terms in the WF formulation. A summary of verification efforts demonstrates the credibility of this solution against independent results from FE analyses. We also compare results of this new solution against independent SIFs computed by FE analyses, legacy SIF solutions, API 579, and FITNET. These comparisons indicate that the new WF solution compares favorably with results from FE analyses. Finally, we summarize the capabilities of this solution in NASGRO®.
New Evaluation Method Based on CAV for Seismic Fatigue Damage of Plant Pipeline (Applicability to General Pipelines)
Authors: Inada Fumio , Sakai Michiya , Morita Ryo , Tamura Ichiro
Published: November 2024

Unnecessary plant shutdowns are avoided using the cumulative absolute velocity (CAV) on the nuclear power plant’s free-field seismic instrumentation to determine operating basis earthquake in the US; however, the relationship between the CAV and damage mechanism has not yet been clarified. In a previous study, authors found that the CAV of the piping vibration response can relate to the vibration stress, using the velocity rule from the ASME standard for the Operation and Maintenance (OM) of Nuclear Power Plants. Using the velocity rule, a new evaluation method of cumulative fatigue damage can be derived as proportional to CAV of the vibration response to the 2.4th power. The feasibility of this has been confirmed only for cantilevered pipes that have a mass at the tip. In this study, the Z-bend pipeline and three-dimensional pipeline used in the JSME benchmark analysis are considered to confirm the applicability of the new method based on the velocity rule to more general pipelines. The vibration response of these general pipelines to seismic waves was calculated, and the cumulative fatigue damage was evaluated using both the new method and direct calculations. The results were in good agreement.
Study on Compatibility Assessment of Urban Natural Gas Pipeline Welded Joints Under Hydrogen Environment
Authors: Guo Songrui , He Xiang , Shao Lingxiao , Shen Xi , Hua Zhengli
Published: November 2024

Hydrogen, as one of the crucial carriers in achieving the green and low-carbon transition, plays a significant role in a multi-energy structure. Among the existing hydrogen transportation methods, the transportation of hydrogen in the form of hydrogen-blended natural gas through the existing urban natural gas pipeline network is an effective way to enhance transportation efficiency and substantially reduce costs. However, when hydrogen comes into contact with the metal materials of natural gas pipelines, it can lead to hydrogen embrittlement, resulting in a deterioration of the mechanical properties of the metal materials and even causing significant accidents. Notably, the welded joint area of gas pipelines is widely recognized as the vulnerable link in pipeline transportation systems because the microstructure and mechanical properties of the welded joint area differ significantly from those of the pipeline steel base material, making it the most susceptible site for hydrogen embrittlement-induced failure. In this study, using 20# steel as the research subject, specimens were taken from the vertical weld seam in its welded joint area. The slow strain rate tensile test, low cycle fatigue test and fatigue crack growth test under hydrogen environment were carried out to explore the variation of mechanical properties under different working conditions. The results demonstrate that with an increase in hydrogen content, the yield strength and tensile strength of the welded joint in 20# steel decrease slightly, resulting in a deterioration of mechanical properties. The elongation and reduction of area after fracture decrease, indicating reduced material plasticity and an intensified degree of hydrogen embrittlement. With the addition of hydrogen, the overall low cycle fatigue life of specimens decreases. The relative fatigue life for the three materials are 74.22%, 62.02%, and 46.05%, demonstrating a noticeable decline in fatigue performance. Hydrogen significantly increases the fatigue crack growth rate in the weld zone of 20# steel. At a hydrogen addition of 10vol%, the fatigue crack growth rate is already approximately 12 times higher than that in the reference environment with 0vol% hydrogen. Simultaneously, with the increase of hydrogen content, the fatigue crack growth rate and the degree of deterioration both escalate, and the deterioration indexes are all above 90 %. The research findings can be utilized to assess the compatibility of gas pipeline welded joints in a hydrogen environment.
Assessing Bulge-Induced Damage in Coke Drums to Plan Structural Weld Overlay Repairs
Authors: Araque Vivas Egler Dubin , Park Stephen Michael
Published: November 2024

Depending on the cycle time, design, fabrication, and operations, coke drum repairs could be required in as little as five years of operation. In the last fifteen years, use of Structural Weld Overlay (SWOL) as a repair strategy to extend the remaining life of coke drums has increased. Bulge-induced damage in the cylindrical and conical sections is one of the main reasons for SWOL repairs to be executed in vessels.

The Local Plastic Strain Indicator, abbreviated as LPSI, is used as a methodology to show two cases of how bulge-induced damage evolves and at what point SWOL repairs should be applied in coke drums. LPSI identifies and ranks bulges prone to local failures using an estimation of plastic strain calibrated against bulges that developed internal or external bulge-induced damage. The LPSI is the ratio of the plastic strain found at the analyzed point to the calibrated strain limit found at points where through-wall cracks occurred due to bulging, in a percentage form.

As the cases show, there have been many premature repairs executed because of the lack of assessment of surface damage and problems with damage have then developed at the edges of those weld overlay repairs. At the end, guidance about how strain levels and surface damage should be combined to better assess SWOL repairs areas is provided.
Piping Seismic Design Method by ASME CC N-900
Authors: Shibukuwa Kenichi , Wen Jie , Funasaki Kenji
Published: November 2024

In seismic isolation structures for nuclear power plants, it has been reported that conventional seismic design methods cannot be applied to the seismic design of crossover piping against building isolation boundaries, which are supported by numerous supports, due to problems such as the overlap between the large relative displacement of the anchor section and the response amplification of the pipes. One solution to this problem is a seismic evaluation method based on elastic-plastic analysis of piping. ASME published a code case that provides strain-based acceptance criteria for seismic evaluation of piping system for Level D service level in 2019, but it is still not fully used in actual seismic design work because specific evaluation procedures and key design data such as true fracture strain are not developed in ASME CC N-900[1]. Therefore, this paper provides with the strain base criteria, technical background and seismic evaluation procedures by using ASME CC N-900[1]. Also, in order to explain the applicability of the “design evaluation procedure for piping” proposed to actual design, this paper reports a results of sample evaluation to “piping design of small-diameter piping in buildings that can be seismically designed according to ASME Section III NCD-3650” instead of crossover piping against seismic isolated boundaries and confirms the basic characteristics of the piping design evaluation procedure using ASME CC N-900.
Ultrasonic Phased Array Linear-Nonlinear Fusion Imaging Method of Microcracks in Pressure Equipment
Authors: Cheng Jingwei , Fan Zhichao , Chen Xuedong , Chen Wei , Wang Zhe , Bu Yangguang
Published: November 2024

Crack is one of the most significant defects that easily occurs during the use of pressure equipment. The growth of microcracks is seen to be at an exponential rate. Therefore, it is very necessary to detect microcracks within the equipment through non-destructive testing (NDT) promptly to avoid their rapid propagation from giving rise to safety risks during the operation of equipment. As a manifestation of early damage to materials, microcracks are prone to inability of detections and misjudgment of detections by employing conventional detection methods. Acoustic nonlinearity has been shown to deliver some sensitivity to early damage from the materials, so it can be analyzed with the implementation of nonlinear ultrasonic detection techniques. Compared with conventional ultrasonic detection methods, phased array technology utilizes multichannel transmission and reception, delivering wider detection coverage without repositioning the probe. Therefore, this technique is advantageous over other NDT methods for microdefect detection. This paper demonstrates the high sensitivity of nonlinear ultrasonic imaging metrics to the crack tip by combining them with the linear imaging method (total focusing method), thereby achieving morphological reconstruction and quantitative evaluation of buried microcracks within the structure. Experimental results show that the linear-nonlinear fusion imaging method can effectively characterize the defects.
Effect of Hydrogen Pressure on Hydrogen Embrittlement Behavior of 23Cr2Ni4MoV High Strength Steel
Authors: Yang Hao , Chen Xuedong , Fan Zhichao , Zhou Yu
Published: November 2024

In this paper, effects of gaseous hydrogen pressure on the mechanical properties and fracture morphology of the 23Cr2Ni4MoV steel were analyzed by modified slow strain rate tensile (MSSRT) test and scanning electron microscope (SEM). The results show that the plasticity of 23Cr2Ni4MoV is significantly influenced in hydrogen environment with respect to that in nitrogen environment, rather than the yield strength and ultimate tensile strength. The elongation (EL) and the reduction in area (RA) are degraded by 79% and 68% in 35 MPa gaseous hydrogen with respect to the results in 35 MPa gaseous nitrogen. The crack initiates at the surface of the sample in the hydrogen, and the initiation depths influenced by hydrogen are 100 μm, 300 μm, and 700 μm in 1 MPa, 10 MPa and 35 MPa hydrogen environment, respectively. In the nitrogen environment, the microstructure of the crack-initiated region is dimple; while in the hydrogen environment, it is cleavage and rock-sugar like. In addition, in the hydrogen environment, circumferential cracks appear at the surfaces near the fracture of 23Cr2Ni4MoV steel.
Embrittlement of 347H Stainless Steel Welds in 538 °C (1000 °F) Service
Authors: Hau Jorge , Dalal Mitul , Penso Jorge
Published: November 2024

A metallurgical evaluation was conducted involving 347H stainless steel welds removed from a resid hydrocracking unit hot hydrogen pipe system, after 5 and 15 years of service. The welds were found to have embrittled. The absorbed energy of Charpy tests was as low as 18 J (13 ft-lb). Tensile test ductility was as low as 7–9% elongation. The creep ductility of these welds was found to be rather low. The elongation to stress rupture varied from 0.5 to 0.9%. The Ω factor varied from 382 to 548. However, creep strength was as good as new 347H stainless steel base metal. Average magnetic ferrite number FN measurements indicated values of 1.4 to 2.1, on cross sections, and of 1.6 to 2.9 on the OD. All these welds were stabilize-heat treated at 900 °C (1650 ± 25°F) for a minimum of 4 hours when installed and again, to stress relief after welding. This reduced the FN. Solution annealing at 1066 °C (1950 °F) followed by water quenching fully restored Charpy absorbed energy values, tensile test ductility, significantly reduced the yield strength but caused no changes in the tensile strength. This solution annealing treatment increased creep strength but did not restore creep ductility at all. Creep brittle welds are more prone to form crack than creep ductile material, at high stressed locations, which are typically notch-like geometric configurations or defects. Thus, the high creep brittleness found at these 347H welds is a concern, which is why it was investigated.
Development of a Program Based on Re-Meshing for Natural Crack Growth of Multiple Cracks
Authors: Lee Gi-Bum , Hong Chan-Gi , Yoon Seok-Jun , Huh Nam-Su , Park Sung-Hoon
Published: November 2024

Nuclear power plant facilities undergo periodic in-service inspections for structural integrity assessment. During these inspections, when multiple cracks are detected, the stress distribution and fracture mechanics parameters at the crack tips can be significantly influenced by the adjacent cracks. Therefore, to accurately conduct multiple crack evaluation and crack growth, it is essential to consider such crack interactions. Existing code and standards (ASME Section XI, API 579, and BS7910) provide guidelines for the evaluation and coalescence produce for multiple cracks. However, these conventional procedures may assume conservative evaluations, such as merging two close elliptical cracks into a single larger ellipse. In this study, a program based on adaptive meshing through finite element analysis was developed which includes generating crack tip meshes suitable for coalescing multiple cracks. After crack coalescence, criteria for crack tip relaxation considering the spider-web mesh were applied, and the coalescence distance criterion from ASME Section XI was employed. Fatigue crack growth was performed using both the coalescence criteria applied in the program and those from ASME Section XI, and the crack growth results were compared. This analysis aimed to evaluate the impact of the coalescence assumptions from ASME Section XI on crack assessment.
State-Dependent Seismic Fragility Functions for Bolted Flange Joints on Special-Risk Industrial Substructures
Authors: Nardin Chiara , Bursi Oreste S. , Broccardo Marco , Marelli Stefano
Published: November 2024

Seismic vulnerability assessment of industrial plants and process equipment has gained attention lately. However, the complexity of the problem and its modelling, combined with a general scarcity of available data on industrial systems, contributed to limiting or developing risk assessment methods based on extremely simplified models. On these premises, a new methodology that combines limited data from finite element FE models with cutting-edge machine learning techniques is developed to generate state-dependent fragility functions for critical components mounted on archetypical industrial substructure modules. Specifically, referring to the classical forward uncertainty quantification scheme, a physics-informed FE model, calibrated on the results of a comprehensive shake table test campaign of a real-scale industrial braced-frame BF steel substructure, is considered. Time histories of seismic event sequences generated by a site-based ground motion model compose the input provided to the FE model. The uncertainty is then propagated through Monte Carlo analysis on inexpensive-to-run polynomial chaos expansion (PCE) metamodels set for each starting damage level condition measure. As a result, empirical state-dependent fragilities are evaluated, assuming the lognormal distribution.
Prediction of Compressive Residual Stresses According to Ultrasonic Nanocrystal Surface Modification Process Variables of Alloy 600
Authors: Seok Tae-Hyeon , Choi Ju-Won , Huh Nam-Su
Published: November 2024

Primary water stress corrosion cracking (PWSCC) has been reported in Alloy 600 components. PWSCC occurs due to a combination of high tensile residual stress, corrosive environment, and susceptible material. Prevention of PWSCC primarily involves mitigating tensile residual stresses. One of the peening techniques, ultrasonic nanocrystal surface modification (UNSM), applies a static load and high frequency ultrasonic vibrations of 20 kHz to the strike pin, generating high compressive residual stresses on the surface. Predicting the variation in compressive residual stress according to process variables is essential for analyzing the prevention of PWSCC. Numerous studies have been conducted to predict compressive residual stresses according to process variables, but research on Alloy 600 is insufficient. The finite element analysis methodology is compared to experimental results. Static load and amplitude are considered as variables. The analysis results are quantitatively analyzed, categorizing into surface residual stress, maximum residual stress, and effective depth. As the static load and amplitude increase, the compressive residual stress becomes larger and affects deeper. Amplitude has a greater influence on magnitude of surface residual stresses than static load.
Ultrasonic Examination of Welds in Cast Austenitic Stainless Steel PWR Reactor Coolant System Piping Welds
Authors: Hayden John , Van Velsor Jason
Published: November 2024

ASME Section XI Class 1 RCS piping system welds fabricated using CASS materials pose serious and well-understood challenges to their effective ultrasonic examination. For decades, utilities and regulators have struggled with the administrative and financial burdens of Relief Requests, which were, and are still, based on the inability to perform meaningful volumetric examinations of welds in CASS components. Many years of futility and frustration may have also fostered the belief that the technology that would allow the effective and meaningful examination of CASS materials would never be achievable. This is no longer the case.

The failure mechanism for CASS material occurs through the loss of fracture toughness due to thermal aging embrittlement. The susceptibility of CASS material to thermal aging embrittlement is strongly affected by several factors, primary of which are system operating time and temperature, the casting method used during component manufacture and molybdenum and ferrite content. In addition to the existing ASME Section XI requirements for the examination of welds in CASS materials, the susceptibility to thermal aging embrittlement drives the requirement for additional examinations (including ultrasonic examinations) as directed by several NRC-published NUREGs required for plant license renewal.

This paper also describes the laboratory examinations of CASS pipe weld specimens that has resulted in an effective ultrasonic examination technique for the detection, length and through-wall sizing of flaws in CASS piping welds, which plays a very important part for both currently required Inservice Inspections (ISI) and for plant license renewal Aging Management Programs.
Seismic Sliding in Storage Tanks: An In-Depth Analysis and Design Insights
Authors: Manjrekar Vivek , Stokes Neville , Choi Junho
Published: November 2024

The response of storage tanks to earthquake forces has been the subject of extensive research worldwide, resulting in a wealth of data that provides guidance for designing tank components capable of withstanding earthquake loads. This includes determining the necessary freeboard to account for sloshing wave heights, calculating base shear forces, and assessing overturning moments, among other considerations. However, there is a notable gap in the available information pertaining to a crucial aspect of tank behavior during seismic events: their ability to resist sliding. The absence of comprehensive experimental data or research findings in this area has led tank design standards like API 620[1,4] to adopt a conservative approach, considering sliding resistance solely through friction between the tank and the subgrade and imposing higher safety factors. While these safety precautions are undoubtedly essential, they can sometimes result in impractical tank configurations, particularly for large-capacity tanks.

To address this significant knowledge gap, this study focuses on investigating the force required to initiate sliding and the post-sliding impact on tank components, especially anchor straps. Additionally, the research delves into evaluating resistance to lateral loads using the shear friction method by leveraging the shear capacity of mechanical anchorage. To achieve this, nonlinear finite element analysis is utilized using nonlinear geometry and elastic-plastic material properties.