bluuebunny/crossref_metadata_2025_split huggingface dataset:
Research on Effects of Surface Finishing and Mean Stress on Fatigue Lives of Notched Specimens - Surface Finishing Effect for Notched Specimens of Carbon Steel
Authors: Takanashi Masahiro , Wang Yun , Hirano Akihiko , Kitamura Yoshihide 
Published: November 2024

Abstract
The DFC1 and DFC2 subcommittees of the Japan Welding Engineering Society developed a new approach to fatigue analysis. A part of the approach has been revised and incorporated into JSME Environmental Fatigue Evaluation Method for Nuclear Power Plants 2022 Edition, which also includes the factor for the effect of surface finish. Considering the factor was devised on the basis of limited tests and literature reviews, the subsequent subcommittees, DFC3 and DFC4, investigated the effect of surface finish on the fatigue strength. This paper presents the effect of surface finish on the fatigue strength of carbon steel in a series of studies by the subcommittees. Initially, four series of smooth round bar specimens were prepared. One series was polished, while the other three were machined to target surface roughness levels of Rz = 6.3, 25, and 50 μm, respectively. Strain-controlled fatigue tests were conducted on these specimens. The fatigue strength of Rz = 6.3 μm was comparable to that of the polished specimen. However, it reduced with an increase in surface roughness. The fatigue strength ratio of the polished specimen to the machined specimen was defined as the factor for the effect of surface finish, Ksf. The maximum value of Ksf was about 1.15, which rose in the high-cycle region. Subsequently, considering that actual components typically fatigue at structural discontinuities, load-controlled fatigue tests were conducted on round notched specimens, with the notch root polished and machined to Rz = 25μm. The Ksf was obtained in the same manner as for the smooth specimen. It was hence affirmed that the Ksf of JSME, developed from the smooth specimen test results, is applicable to structural discontinuities where fatigue failures arise in actual components.
Hillside Nozzle Crack Analysis Comparison Using FAD and Crack Driving Force Methods With 3-D Crack Meshes
Authors: Thorwald Greg 
Published: November 2024

Abstract
Computing accurate crack assessments, such as via methods described in the API 579-1/ASME FFS-1 standard, helps support reliable pressure vessel operation, maintenance and inspection. When solutions of the actual crack geometry or location are not available, three-dimensional (3-D) crack meshes can be used in Finite Element Analysis to compute the solutions. Two crack assessment methods are used in this paper to assess postulated cracks in the weld connecting a hillside nozzle to the vessel’s elliptical head. The first method is the Failure Assessment Diagram, and the second method is the crack driving force.
Both crack assessment methods concurred that the cracks are sub-critical. The deeper crack case located at the side of the nozzle gave the largest J-integral value of the examined cracks and was less than the material estimated toughness. Weld residual stress was included in the analyses by a simplified method applying a delta temperature to the weld zone nodes to cause contraction in the weld, resulting in tensile residual stress.
When using 3-D crack meshes, the crack driving force method may be advantageous to include both weld residual stress and pressure loading within a single elastic-plastic model, and the analysis needs to converge only to the design pressure. The FAD method uses elastic analyses to compute the stress intensity for each load category (i.e., primary, secondary, or residual), which are quicker to run. In this analysis, an estimated reference stress was used because the elastic-plastic analysis of the pressure load to compute the reference stress did not provide sufficient results.
A Thermal Striping Evaluation Methodology for Natrium™ Internal Components Using Frequency Response Function Solutions
Authors: Xu Heqin , Riordan Tom , Bhuiyan Shafiq , Koneru Saradhi , Cohen Michael 
Published: November 2024

Abstract
Liquid sodium is used as the coolant in the Natrium (a TerraPower and GE-Hitachi technology) reactor design because of its outstanding thermal properties. Sodium becomes liquid at above 98°C and remains in liquid state up to a very high temperature of 883°C at atmospheric pressure. This feature allows the reactor to have a high operating temperature while maintaining a sufficient margin to avoid boiling of the coolant under all design basis events, without any pressurization as is typically utilized in a light water reactor (LWR) design. On the other hand, there are certain critical structural mechanics issues for the components in contact with high temperature liquid sodium. Besides the design basis thermal transients, the primary coolant streams flowing out of the fuel assemblies and control assemblies may experience incomplete mixing of hot and cold jet flows, causing a special thermal hydraulics phenomenon called thermal striping. The thermal striping may have a temperature fluctuation over 50°C at frequencies of 0.1 to 10 Hz. The temperature fluctuation in the flow may also be caused by thermal stratification at the interface of the horizontal relatively hot and cold streams. Due to the high frequency temperature fluctuation in the liquid sodium, the structures in contact with the flow are subjected to nontrivial cyclic thermal stresses which may cause high cycle fatigue (HCF) damage to the structures. The structures containing both liquid sodium and cover gas may also experience temperature fluctuation due to free surface level fluctuation at the liquid/gas interface where the cover gas and the liquid sodium have very different thermal conductivities. This paper presents frequency response function (FRF) solutions to evaluate the thermal striping limits of the Natrium internal components against the fatigue crack propagation prevention criteria while considering the cyclic range of thermal stresses and stress intensity factor due to the thermal striping on one side of a component, and various boundary conditions on the other side.
Elastic-Plastic Finite Element Analysis Utilizing Detailed Crack Profiles
Authors: Holloman Ryan , Blanks Daniel , Martinez Miguel , Thorwald Greg , Turnquist Michael 
Published: November 2024

Abstract
Operators are required to mitigate any known risk identified during a pipeline inspection, meaning all detected crack-like defects must be investigated. While defects with depths or lengths exceeding the limits set by the pipeline owner will be repaired, shallower or shorter crack-like defects are often evaluated using engineering analysis and judgement. Deterministic assessment based on modern fracture mechanics is commonly used to inform the mitigation process. However, these assessments often assume lower bound material properties and generalize the crack shape as semi-elliptical for simplicity and conservatism, potentially rendering overly conservative results.
Through evolving in-line inspection (ILI) technology, ultrasonic imaging technologies can now capture the true profile of a crack-like defect. Rather than assuming a semi-elliptical crack based on a single depth and length measurement, detailed crack shape analysis now offers reduced conservatism and improved accuracy. However, averaging techniques are often used to characterize a detailed crack shape given that closed-form fracture mechanics models such as API 579-1/ASME FFS-1 Fitness-for-Service (API 579) or MAT-8 require an assumed semi-elliptical geometry.
An alternative deterministic assessment is provided that can be executed with the detailed crack profile using elastic-plastic finite element analysis to calculate burst pressure and remaining life. Three-dimensional (3-D) crack meshes of the detailed crack profiles are generated using the ILI data, enabling the J-integral to be accurately computed along the entire crack front. The maximum crack front J-integral value is compared to the pipe’s toughness to determine the predicted burst pressure. The 3-D custom shape crack results can then be compared to the API 579 and MAT-8 fracture models. This alternative approach reduces conservatism, which can aid operators and reduce costs while maintaining asset integrity.
Electromagnetic Lithium Ring Compression for Magnetized Target Fusion Application: Trajectories
Authors: Dick Jean-Sebastien , Sirmas Nick , Bernard Scott , Santos Lemuel , Forysinski Piotr 
Published: November 2024

Abstract
To achieve commercially relevant fusion conditions in a magnetized plasma, rapid and efficient heating must surpass heat loss. In Magnetized Target Fusion (MTF) experiments, which heat plasma by compression, a magnetic flux conserver made of metal is essential for plasma confinement, and an understanding of the compression trajectory of this plasma liner is crucial to the design and operation of the machine.
In this work, lithium rings, 527 mm in diameter and 55 mm in height, were produced by centrifugal casting and electromagnetically compressed using a high voltage power supply with capacitor energy ranging from 100 kJ to 250 kJ. High speed cameras were used to track the trajectories of the inner and outer edges of the top surface of the ring, as well as its inner edge at the equator. Magnetic field sensors were positioned at a number of radial locations to measure the change in magnetic flux density during ring compression. Ring parameters, such as thickness and temperature, were explored to attain symmetric compression trajectories free of buckles.
A 2D-axisymmetric numerical model was developed using the ANSYS LS-DYNA software package to predict compression trajectories and evaluate the energy efficiency of the compression. The aim of this work is to assess the use of concentric coil electromagnetic compression, also known as a theta-pinch, in magnetized target fusion using a solid lithium liner and to validate the LS-DYNA model. Close agreement between simulation and experiment was observed. This research contributes to advancing Magnetized Target Fusion technologies, with implications for future fusion energy applications.
Comparative Study of Crack Shape on the Ductile Fracture Response of Cracked Pipelines
Authors: Zhang Xinfang , Yoosef-Ghodsi Nader , Kainat Muntaseer , Leung Juliana Y. , Adeeb Samer 
Published: November 2024

Abstract
Buried pipelines are subjected to various types of loads, including external pressure from soil overburden and internal pressure from pressurized fluids. These loads can induce axial and hoop stresses, which are the primary factors leading to the formation of integrity threats, such as cracks. The presence of cracks can render a pipeline susceptible to failure, posing a significant threat to its operation, safety, and the environment. This underscores the importance of promptly detecting and evaluating even seemingly minor surface defects, as they can significantly damage the structural integrity of the pipeline. It is also crucial to accurately predict the failure pressures of pipelines with cracks to ensure that the operating pressure remains below this critical limit with an adequate margin of safety. A variety of approaches exist for assessing cracks in pipes, including empirical approaches such as MAT-8, Ln-Sec and CorLAS™ models, as well as numerical approaches like the extended finite element method (XFEM). XFEM is a powerful tool to estimate the failure pressures of pipelines containing cracks. It extends the capabilities of the traditional Finite Element Method (FEM) and offers a more effective means of simulating crack propagation. In ABAQUS, initial cracks can be modelled in either sharp or blunted shapes. However, it is uncertain whether the shape of the crack affects the failure pressures of cracked pipelines. For this purpose, detailed parametric studies are necessary to investigate the implications of pre-existing cracking shapes on the ductile fracture response of pipes subjected to pure mode I loading.
Fitness-for-Service Analysis of a Light Water Reactor Pressure Vessel Under Complex Operating Conditions
Authors: Tran Minh N. , Muransky Ondrej , Spencer Benjamin W. 
Published: November 2024

Abstract
Conventional power-generation plants, including nuclear plants, have been traditionally designed to provide a steady baseload energy capacity, optimizing output efficiency while minimizing variable costs. However, the growing adoption of large-scale renewable energy-generation systems, which rely on intermittent sources such as solar and wind, has introduced more variability into the energy supply in interconnected electricity grids. As a result, the next generation of power plants needs to operate in what is known as load-following mode, requiring flexible adjustments in electricity production to align with the energy demand on the grid. This transition from the steady baseload operation to load-following operating conditions can significantly increase the number of times various plant components are exposed to transient stresses. This increased thermomechanical cycling can lead to accelerated material degradation, thereby elevating the risk of premature component failure. It becomes imperative to conduct a comprehensive analysis of fatigue, creep-fatigue, and stress corrosion cracking life to assess the resilience of the various engineering components under these flexible load-following operating conditions.
This study aims to develop a comprehensive numerical model of a light-water reactor pressure vessel (RPV) to investigate its degradation under various operating scenarios. This coupled thermomechanical finite element analysis evaluated the stress response of the RPV caused by considering fluctuations in thermal and mechanical loads caused by the varying pressure and temperature occurring during the load-following operation. Critical locations on the RPV are subsequently identified based on the stress response. The stress intensity factors for the postulated flaws at those locations are then calculated, followed by an evaluation of the reactor’s life in accordance with the American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section XI. This comprehensive life assessment covers a number of transients expected during the flexible load-following operation, providing invaluable insights into the RPV’s structural integrity. Moreover, the development methodology can be adapted to other reactor components, as well as components of conventional power stations affected by varying operating conditions.
Research on Effects of Surface Finishing and Mean Stress on Fatigue Lives of Notched Specimens (5) - Application of Elastic-Plastic FE Analyses for Notched Specimens of Carbon Steel
Authors: Nakane Motoki , Wang Yun , Takanashi Masahiro , Hirano Akihiko , Kitamura Yoshihide 
Published: November 2024

Abstract
The DFC3 and DFC4 subcommittees of the Japan Welding Engineering Society had investigated the effect of mean stress on fatigue properties of notched carbon steel and mean stress correction methods. In these studies, small specimens were adopted for fatigue tests and these tests are conducted by load control because the cross section of the notch root is too narrow to measure the strain. However, it is very important to understand the strain or stress state at the notch root to evaluate the fatigue test results.
In this study, an elastic-plastic analysis method for circular notched carbon steel specimens was investigated to contribute to the setting of fatigue test conditions and the evaluation of test results. The equivalent strain amplitudes calculated from the analyses were almost consistent with the S-N curves of smooth specimens and this agreement showed the validity of the application of the analytical method to circular notched specimens. Furthermore, the loading conditions for fatigue tests of circular notched specimens subjected mean stress were examined. The results indicated that fatigue tests with mean stress of about 5 MPa to 17 MPa and 9 MPa to 17 MPa can be expected for the notched specimens with stress concentration factor Kt = 1.5 and Kt = 1.8, respectively.
Validation Program for Seals and Flange Gaskets in Hydrogen and Hydrogen-Methane Blends Applications
Authors: Lejeune Hubert , Felten Jérémy 
Published: November 2024

Abstract
There is an increasing interest in hydrogen as a clean energy carrier in decarbonizing energy systems. Hydrogen’s various production paths and use for storing and transporting energy make it a flexible option for linking diverse sources of power generation with transmission and distribution networks. Large-scale hydrogen consumption will require a well-developed hydrogen transport infrastructure. For example, the European Hydrogen Backbone (EHB) initiative, bringing together more than thirty energy infrastructure operators, is working on the definition of hydrogen infrastructure including existing and new pipelines. Seals are identified as key components for the performances of these infrastructures, but a lack of recognized test protocols and available test data are reported by the end-users.
In this context, with several partners, Cetim (Technical Center for Mechanical Industry) has launched in 2022 a testing program on different seal types (“O”-rings, gaskets and dynamic seals) to evaluate their sealing performances and integrity (including Rapid Gas Decompression) with 100% hydrogen, 20% hydrogen - 80% methane blends and 100% helium (or 100% methane) as a reference gas. Long term thermal ageing was also involved to check the performances stability. This paper will identify facilities presently in use for validation, the testing protocols with which these tests are conducted and most importantly, their results.
Analysis and Treatment of Pipeline Vibration in Centrifugal Compressors
Authors: Wang Chengwen 
Published: November 2024

Abstract
While going through the startup process of a centrifugal compressor unit, the pipline of compressor tertiary outlet bypass to a gas expander and supporting structure was observed to be shaking abnormally. The shaking was significant enough that worker feld foot numbness on the steel grating and at a level that the owner was afraid of approaching the piping. The initial assumption was that the piping or the piping supports had been improperly designed. After being reinforced with the supports, the vibration still hadn’t been alleviated.
Further investigation revealed that the root cause of the problem was a flow-generated pulsation of the compressor that excited the pipeline shell mode. But the project’s start-up schedule was tight, and had no time to use CFD to analysis the reason. meantime it’s hard to change the excitation of the compressor and the mode of piping. The ultimate solution to the problem was the “flow-splitters” method to reduce the pulsation. we installed two porous noise reduction plates on the original flange of the pipeline. At last the vibration dropped to an acceptable range in the shortest possible time, ensuring the start-up progress. It provided a practical basis for the treatment of pipeline vibration of large centrifugal compressor in the future.
Present Status of the FRACTESUS Project: Numerical and Experimental Round Robins on Irradiated and Unirradiated Materials
Authors: Bonny Giovanni , Uytdenhouwen Inge , Altstadt Eberhard , Arffman Pentti , Cicero Sergio , Obermeier Florian , Petit Tom , François Pierrick , Tanguy Benoît , Swan Helen , Wilcox Hannah 
Published: November 2024

Abstract
The FRACTESUS project aims to determine the effect of specimen size on the fracture toughness properties. The project has entered its last year and many preliminary data are available. In this contribution, we report on the status of the three main inter-laboratory round robins (RR) that have been completed: i) numerical round robin; ii) experimental round robin on unirradiated materials; and iii) experimental round robin on irradiated material. The numerical round robin is completed by nine different laboratories and shows that the different numerical tools and set-ups used by the different laboratories provide comparable and consistent results. The experimental round robin on six unirradiated materials is completed by 13 different laboratories (&gt; 480 fracture toughness tests). Except for the 73W weld material, the reference temperatures T0 obtained from MC(T) specimens by the different laboratories compares well to the ones obtained from large (mostly 1T-C(T)) specimens. The experimental round robin on the irradiated 73W weld material is performed by seven different laboratories (&gt; 112 fracture toughness tests). Similar to the unirradiated case, T0 obtained from the MC(T) data set largely underestimates T0 from large specimens by about the same amount.
An Application for Crystal Plasticity Finite Element in Updating Industrial Integrity Assessment Practices
Authors: Horton Edward W. , Mostafavi Mahmoud , Knowles David , Chevalier Marc 
Published: November 2024

Abstract
Within the nuclear sector, structural integrity assessments must be performed to prove a plant is still safe to operate. Currently these assessments are conservative out of necessity, however if this conservatism could be reduced power plants could remain in operation for longer. To help increase the accuracy of predictions better material models can be used which take account of detailed features that are not completely considered, such as microstructure variation in fabricated component. Crystal plasticity (CPFE) is a technique that accounts for microstructure, so has the potential to help inform future revisions of integrity assessments. In this work CPFE is used in conjunction with the assessment code R5 to predict the life of a volume of material. The mesh within this volume is changed to represent microstructures often seen in service. It was found that CPFE was able to predict similar life to an inelastic model produced using suggestions from R5. The CPFE model also showed that different microstructures give a varying mechanical response which is something traditional continuum models are not directly capable of modelling.
Allowable Stress and Allowable Flaw Sizes Estimated by Converted Tensile Properties From Hardness for Austenitic Stainless Steel Pipe
Authors: Ha Yoosung , Yamaguchi Yoshihito , Hasegawa Kunio , Negyesi Martin 
Published: November 2024

Abstract
If a flaw in a high-toughness ductile pipe of a power plant is detected during periodic in-service inspection, stress applied at the flaw location of the pipe is compared with an allowable stress. When the applied stress is less than the allowable stress, the plant can operate continuously for a certain evaluation period in accordance with ASME Code Section XI. The flow stress given by the average of yield strength and ultimate tensile strength is an important material parameter for allowable stress. Recently, many fitness-for-service codes and technical reports have adopted conversions from hardness measurement values to yield strength and ultimate tensile strength. In this paper, we introduced the flow stress obtained from converted tensile properties from Vickers hardness using the presented equations for austenitic stainless steel. The allowable stress and allowable crack depths (sizes) estimated by the Vickers hardness were compared with those determined by actual tensile properties. As a result, the flow stress converted from hardness was about 1.5 times larger than that obtained by actual flow stress. The allowable flaw sizes calculated by the flow stress converted from hardness gave an appropriate indication when the allowable or applied stress was very low. However, the flow stress converted from hardness gave unconservative allowable stress, when the applied stress was large. Since the results are based on one available hardness measurement, other hardness measurements should be necessary to confirm these preliminary conclusions.