bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluid-Structure Simulations of Vortex Shedding Induced Vibrations on Two In-Line Cylinders in Water Cross-Flow
Authors: Vivaldi Daniele
Published: November 2022

Experimental tests accessing both fluid and structure behaviors are mandatory for a consistent assessment of fluid-structure interaction (FSI) numerical simulations. In this paper, published results of an experimental configuration of two in-line cantilever cylinders subjected to water cross-flow were considered: instantaneous fluid velocities and pressure are available on several positions inside the test section, together with the cylinder vibrations. FSI simulations were performed by coupling Ansys Fluent (for the fluid domain) with Ansys Mechanical (for the solid domain). URANS simulations and Scale-Adaptive Simulations (SAS) were employed as CFD simulation approach. The structure displacements were taken into account through an Arbitrary Lagrangian-Eulerian approach. The fluid-structure coupling was 2-way explicit. Simulations were performed for two different water mass flow rates. For the highest one, vortex-induced resonance is observed experimentally. The numerical results show consistent agreement in terms of shedding frequency and velocity spectra behind the cylinders. The calculated vibration response is overall consistent for the cylinders not featuring vortex-induced resonance; nevertheless, the experimentally observed vortex-induced resonance could not be reproduced by the numerical simulations. The inability to calculate the resonance is explained by the fact that it is found to be caused by the 4th shedding harmonic being in resonance with the cylinder natural frequency: this high harmonic peak could not be numerically reproduced, even by SAS.
Revision of the Annex Z V Concerning the Calculation of Bolted Joints in the French Nuclear Code RCC-M®
Authors: Lejeune Hubert , Rohart Philippe , Triay Manuela , Di Rienzo Aurélien
Published: November 2022

AFCEN is the publisher of the French Nuclear code RCC-M® (Design and Construction Rules for Mechanical Components of PWR Nuclear Islands) [1]. It has launched an action for the revision of the Annex Z V and F 7000, respectively concerning the design and the installation of the bolted flange connections. It should be published as probationary phase rules (Section VI of RCC-M®), in the next version of the code, in 2022. The proposed modifications for F 7000 have already been described in [2], and this paper focuses on the proposed modification for the calculation method detailed in the Annex Z V.

First, the general philosophy and structure of the Annex, including both Taylor-Forge based (Z V 2000) and NF EN 1591-1 [3] based (Z V 3000) calculation methods, is introduced. Then the major proposed improvements introduced in Z V 2000 (Taylor-Forge based), compared to current edition, are detailed. This includes the management of the metal-to-metal contact (MMC) in the connection (between flanges or between flanges and the gasket limiter ring) that can be required in both assembly and operation. Moreover, the use of specific gasket types involved in these connections (Expanded Graphite Ring or Metal Energized C-Ring...) is covered in this paper. Finally, a focus is also performed on other introductions, like the management of standard connections (including standard flanges, gasket, and bolts), the account for the tightening scatter, the effective gasket width determination in regard with the flange rigidity, and the internal force variation in the connections due to thermal expansion.
A Reduced Order Modeling in Finite Element for Rapid Qualification of Creep-Resistant Alloys
Authors: Hossain Md Abir , Stewart Calvin M.
Published: November 2022

This study outlines the application of a Reduced Order Modeling (ROM) approach for the probabilistic creep response of components subject to creep conditions. Time-dependent creep damage is unavoidably inflicted in elevated temperature. Typical operating condition fluctuations experienced during service can greatly limit creep life when compared to the ideal design conditions. To mimic the uncertainty in component, probabilistic Finite Element Analysis (FEA) can be employed; however, numerous full-field FEA simulations (103−105 trials) for probabilistic assessments are time-intensive and computationally prohibitive. To address this challenge, the computationally efficient ROM approach is introduced for probabilistic creep deformation, damage, and rupture predictions in FEA. In this approach, full-scale probabilistic simulation using a 1D model are performed, the extremum conditions retrieved, and applied in 2D/3D model simulations to capture the scatter bands of component response. The Wilshire-Cano-Stewart (WCS) model is calibrated to quintuplicate 304 Stainless steel data. Test condition, initial damage, and material property uncertainty are incorporated into the WCS model via appropriate probability distribution function (pdfs). A USERCREEP.F material model is developed for the WCS model and compiled for ANSYS FEA simulations. Deterministic simulations of the WCS model are carried out in FEA for validation. The goodness-of-fit between the prediction and experiment are observed to be satisfactory. Probabilistic predictions are executed in the 1D model to generate the creep deformation, damage, and rupture prediction. The extremum cases of ductility, rupture, and area under creep (AUC) curves are established. The extremum cases alone are simulated using a 2D model to capture the component level uncertainty. A %Error statistical analysis is performed to verify the accuracy of ROM approach and further validate the approach for proposed simulation of a complex geometry (e.g., turbine blade) at a significantly reduced computational time and memory. Future investigations will introduce stochasticity, temporal, and spatial uncertainty for component-level simulation and improved prediction.
Study on the Predictive Evaluation Method of Load Acting on Roof in Nonlinear Sloshing of Cylindrical Tank
Authors: Ikesue Shunichi , Morita Hideyuki , Ishii Hidekazu , Sago Hiromi , Yokoi Shinobu , Yamamoto Tomohiko
Published: November 2022

Sloshing is a motion of free liquid surface in a tank, which is caused by strong seismic waves with long period components. Sloshing with large amplitude causes damage to the tank roof.

In our previous study, a method was proposed to evaluate vertical load acting on a roof of cylindrical tank due to collision of sloshing liquid surface. The method is a combination of the pressure model based on Wagner’s model and the simplified nonlinear sloshing model that calculates liquid surface shape and velocity. But, the method tends to underestimate the vertical load when roof height is high and overestimate when it is low.

In this study, a new method is proposed to evaluate vertical load acting on a roof of cylindrical tank. This proposed method is constructed by a new pressure model, a new nonlinear sloshing liquid surface model, and a new local liquid surface wave model. Its pressure model is developed by applying the pressure model of two-dimensional flat plate surface to the circumferential wetted region of the roof. Its nonlinear sloshing liquid surface model is developed by adding higher order radial modes of liquid surface shape. Its local liquid surface wave model is developed by considering a nonlinear local liquid surface behavior induced by roof collision.
Investigation Into Degradation of a Pilot Operated Pressure Relief Valve Main Seat During Development Testing
Authors: Kane Martin , Thompson Phil , Stewart David
Published: November 2022

Rolls-Royce has many years of experience of satisfactory performance of cobalt based valve seats used in Pressurised Water Reactor (PWR) environments.

During design development testing of a pilot operated pressure relief valve for a PWR application, rapid degradation of the main seat was observed. This paper reflects on the issues encountered during testing and the investigation into potential degradation mechanisms and causes of the failure.

Excessive leakage of the valve seat was experienced after a very low number of operating cycles and short test duration. Visual inspection of the valve identified damage to the weld deposited, cobalt-based alloy (Co – 25Cr – 5W – 1C) contact faces of the main seat. A metallurgical examination of the damaged surfaces subsequently concluded the most likely cause to be flow erosion-corrosion. This was supported by a literature review of valve seat failures and laboratory studies on wear and degradation of cobalt-based alloys.

An unrelated failure had occurred earlier in the development test programme, which is believed to have introduced a minor surface defect onto the valve seat face. It is believed that this defect created the conditions required for flow erosion-corrosion to occur.

Furthermore, the investigation concluded that given the right environmental conditions and surface defect, flow erosion-corrosion of cobalt-based alloy (Co – 25Cr – 5W – 1C) can occur rapidly. This can cause extensive surface damage over a very short duration, resulting in excessive valve seat leakage. This highlights the importance of pre-service Non-Destructive Examination (NDE) of Pressure Relief Valve seating faces, specifically the allowable acceptance criteria and method applied.

The results of the metallurgical examination and literature review are presented, along with the investigation into the cause of the observed damage to the valve seating faces.
Forward and Inverse Problems in Transient Responses of Plates Under Impact Loadings
Authors: Ji Ming , Inaba Kazuaki
Published: November 2022

By clarifying the free vibration and transient response of the flat plate in contact with the fluid, it is useful for the design of systems such as piping and plants and the development of innovative equipment. We have been studying free vibration and transient response of thin and thick plates and shells.

In this paper, transient responses of plates under a point impact load are studied. The first-order plate theory is used to derive the equations of motion by Hamilton’s principle. The out of plane dominated vibration and in-plane dominated vibration can be decoupled. The transient displacement and strain histories are obtained using the method of mode superposition. The low density and high compliance of Polyvinylidene Fluoride (PVDF) films make them a suitable method to measure the external dynamic force history. The force history is applied to conduct the theoretical analysis. The strain histories obtained from the theoretical analysis are compared with those obtained from experiments. Moreover, the effect of the thickness on the displacement and strain histories is studied.

In addition, the inverse problems of identifying the impact force history are investigated. The transfer function between the impact force and measured responses: displacement and strain histories, are obtained from the theoretical analysis. A deconvolution technique using wavelet approach for reconstructing impact force is used. The reconstructed impact force is in good agreement in with the measured force using PVDF films.
Improved Method of Estimating Steam Hammer Loads
Authors: Walters Trey W.
Published: November 2022

Recent research has shown that a commonly used method to estimate transient pipe forces does not reliably yield conservative predictions. As the topic of transient compressible flow is quite complex, engineers should be very cautious in applying simple algebraic formulas to estimate loads for design use. With that caution in mind, some engineers would still like to have a simple method available. This paper develops a new method that offers an improved way of estimating transient pipe loads. Comparisons are made against numerical simulations for a realistic power station piping example using real gas models for the steam properties and pipe friction. The comparisons are surprisingly good for this example. The improved method provides better estimates than methods commonly used today and is recommended as a replacement for such methods. Engineers should consider using the new, improved method as a preliminary design tool and for screening purposes. Engineers should take extra care in using the new method for detailed design purposes.
Inelastic Response Evaluation Method of Equipment Considering Peak Broadening of Response Spectrum
Authors: Tamura Ichiro , Iwamoto Takuma , Minakawa Yusuke , Maruyama Naotomo , Tsuruki Masaki
Published: November 2022

In order to evaluate seismic responses considering the elasto-plastic properties of equipment and piping systems, nonlinear time history analyses are utilized. When the analyses are used for seismic evaluation of equipment and piping systems in nuclear power plants, it is required to consider the uncertainty in the frequencies owing to uncertainties in the material properties of the structure and soil. The Boiler and Pressure Vessel Code of ASME indicates that the analysis using floor motions with different time intervals, where the time intervals are modified corresponding to the response spectrum broadening, is applicable. However, nonlinear time history analysis of inelastic models is relatively time-consuming compared to linear analysis, and conducting several analysis cases indicated in the Code might increase the burden of analytical work. Therefore, simplified method is desirable to consider the uncertainty in time history analysis.

In this paper, a simplified method using inelastic response spectrum is developed to consider the uncertainty in time history analysis. The applicability of the developed method is investigated by comparing the results of parametric survey with those of the developed method.
Effects of Strain Rate on Strain-Based Failure Assessment of Cask 1m-Puncture Drop for 304 Stainless Steel
Authors: Kim Hune-Tae , Seo Jun-Min , Kim Ji-Hye , Kim Yun-Jae
Published: November 2022

In this paper, a strain-based failure assessment is performed on a canister made of stainless steel when a spent nuclear fuel dry storage system goes through a drop accident, to investigate the effects of strain rate on strain-based failure assessment results. The KORAD-21 multi-purpose dry storage container system developed for interim storage and transportation at the Korea Radioactive Waste Agency (KORAD) is considered. A finite element (FE) analysis is performed on a 1m puncture drop of the KORAD-21 model. Based on the FE results, the canister under a 1m puncture drop is evaluated by two different criteria: (1) strain-based acceptance criteria suggested in ASME Boiler and Pressure Vessels Code Section III, Appendix FF, “Strain-based acceptance criteria for energy-limited events” and (2) the Johnson-Cook fracture strain model based on experimental data. The difference between the two criteria is that the Johnson-Cook fracture strain model expresses the true fracture strain as a function of stress triaxiality and strain rate, whereas the formula in App. FF establishes strain limit (combination of uniform strain and true fracture strain) as a function of stress triaxiality only. In this study, the safety margins of Appendix FF are analyzed by comparing the failure assessment results for canister drop simulation with those applying the Johnson-Cook fracture strain model.
Thick-Walled Cylindrical Specimens Under PTS Loading: Crack Propagation Analysis With XFEM-IGA
Authors: Mora Mendez Diego Fernando , Niffenegger Markus , Mao Gaojun
Published: November 2022

The integrity assessment of reactor pressure vessel (RPV) often considers only the crack initiation to evaluate the safety margin and excludes the crack propagation analysis. In this contribution, the combined eXtended Finite Element (XFEM) method with the Initiation-Growth-Arrest (IGA) algorithm, shortly written as XFEM-IGA, is applied to a thick-walled cylindrical specimen with a circumferential crack under Pressurized Thermal Shock (PTS). The results of the crack propagation analysis are compared with the experimental ones to validate the approach, which were taken from large-scale experiments on thick-walled cylinders under PTS performed in the FALSIRE project. In order to simulate the cylinder with the XFEM-IGA approach, a reduced three dimensional finite element (FE) model of a small sector (a slice of the cylinder) is used by applying cyclic symmetry boundary conditions. Thus, the model profits from the cyclic symmetry not only of the cylinder geometry but also the circumferential crack. The closed-form for the stress intensity factor for an internal circumferential crack in a thick-walled cylinder is combined with the IGA algorithm and is presented to verify the quality of the results. The results are shown in terms of the SIF evolution and crack depth during the PTS transient. The crack depth shows several initiation-arrest-reinitiation cycles and final arrest. However, some differences in the number of these cycles and final crack depth are observed between the simulation and the experimental results.
Relationship Between Natural Period, Strength, and Response Of Piping Systems Subjected to Seismic Motion
Authors: Tamura Ichiro , Tamura Shinji
Published: November 2022

The relationship between the natural period, strength, and the response of piping systems subjected to seismic motion was investigated for straight piping systems and piping systems with elbows. The strength of each mode of a piping system subjected to seismic motion, or seismic inertia force, is represented by the modal yield acceleration, that is, the modal yield strength normalized by the modal mass. The response of that is represented by the modal ductility factor, that is, the ductility factor of the first yielding part of the piping system in its mode. The relationship between the natural period and modal yield acceleration is represented by the proposed piping yield diagram. The relationship between the natural period, modal yield acceleration, and the response is represented by the well-known inelastic response spectrum, or constant-ductility response spectrum. Using these diagrams and spectra, the responses of piping systems to various seismic motions could be estimated without performing individual dynamic analyses of them.
Mechanical Performance of Aged Long Fibers: Direct Water Exposure and Temperature Effect
Authors: Nazaripoor Hadi , Sunny John , Hammami Ahmed , Mertiny Pierre
Published: November 2022

Long fiber-reinforced composite materials consist of continuous fibers with high strength and modulus embedded in either a thermoset or thermoplastic matrix. The resulting composite material provides a combination of properties that cannot be achieved with either of the constituents acting alone. In composite structures, fibers are the primary load-carrying element, whereas the matrix transfers stress to and between the fibers while protecting them from adverse environmental conditions and mechanical damages. While thermosetting matrices provide a high level of protection against water permeation, exposure to moisture may still be significant in certain thermoplastics. Therefore, the effect of moisture on the reinforcing elements and the degradation rate may be considerable. The presented study investigated the effects of environmental aging conditions on different commercially available continuous fibers, i.e., glass fiber, carbon fiber, and basalt fiber. The fibers were soaked in water at room and elevated temperature to investigate the degradation mechanisms and, ultimately, the mechanical performance of the fibers. Mechanical testing was performed with wet fibers and dried fibers after aging. In addition, scanning electron microscopy was employed to explore the responsible mechanism for fiber degradation by environmental aging.
Modelling the Effects of Hydrogen Pressure on Fatigue Crack Growth Behavior in SA372 Pressure Vessel Steels
Authors: Saxena Ashok , Findley Kip O.
Published: November 2022

Low alloy ferritic steels used in fabricating cost-effective cylinders for hydrogen storage are susceptible to hydrogen embrittlement. A model first proposed by Amaro et al. (ARFiDS model) for predicting the effects of hydrogen pressure on the kinetics of hydrogen assisted fatigue crack growth (HA-FCG) in X-100 pipeline steels for pressure between 1 and 20 MPa is adapted in this study and used for predicting the HA-FCG behavior of SA372 Grade J Class 70 pressure vessel steels for pressures ranging between 10 and 102 MPa. The crack growth kinetics in these steels exhibit a typical two-region behavior labelled as the transient and steady-state regions, characterized by distinct power-law exponents in the relationship between fatigue crack growth rate, da/dN, and the cyclic stress intensity parameter, ΔK. The predicted HA-FCG behavior from the model is compared with experimental data for SA 372 steel for hydrogen pressures ranging from 10 to 102 MPa and is shown to perform well for load ratios, R, of 0.2 and 0.5 over a wide range of crack growth rates. The phenomenological basis for the model is discussed.
Best Practices for Tightening Bolted Flange Connections Utilizing a Torque Wrench With an Extension
Authors: Benet Steve , Dupre Ross , Wilson Jeffery
Published: November 2022

Bolted flange connections are widely used in the transportation, power generation, and chemical production industries. The goal of these connections is to contain the media within the bolted flange connections with minimal leaks. While there is increased focus in the industry on general flange assembly best practices, there is little to no focus on flange assembly best practices involving extension tools. In the circumstances, extension tools could be required to reach the fasteners to apply a predetermined torque. Yet, how do we know the torque set on the torque wrench is the same torque transmitted through the torque wrench and the extension to the fastener? Does the length of the extension and torque wrench matter, or does the orientation or angle of the extension in relation to the torque wrench affect the resultant torque?

This paper will explore the variables which affect the applied torque when using an extension tool and detail the best practices to utilize when using this system to tighten bolted flange connections. With the data collected for this testing, end-users will gain a better understanding of the variables affecting the applied torque when using an extension and methods of ensuring the proper torque is applied to each fastener.
Finite Element Analysis of Outer Pressure Containment Vessel and Proton Beam Pipe for Proton Radiography Under Operational Loads
Authors: Holguin Ryan , Hill Dallas , Reichert Heidi , Deines Kyle , Bustos Gerald
Published: November 2022

This paper presents the results of ASME Boiler and Pressure Vessel Code (BPVC) Section VIII Division 2 analyses on a containment pressure vessel system designed to host small-scale shock physics experiments containing hazardous materials. These shock physics experiments are imaged using proton radiography at Los Alamos Neutron Science Center (LANSCE). The pressure vessel system examined is separated into two subsystems, the Outer Pressure Containment Vessel (OPCV) and the Beam Pipe and Auxiliary Hardware (BPAH). The OPCV mates with the BPAH to transport the proton beam and form the outer containment pressure boundary. An Inner Pressure Confinement Vessel (IPCV) is mounted inside the containment pressure boundary. The IPCV can be used to host a variety of physics experiments, which can include high explosive and hazardous materials. The IPCV is an impulsively loaded pressure vessel, while the OPCV and beam pipes are statically loaded. The OPCV and BPAH are designed to satisfy ASME BPVC Section VIII Division 2 Alternative Rules, Part 5 Design by Analysis Requirements for all load conditions expected during service. The BPAH is a series of stainless-steel tubes with low-profile flange assemblies, bellows, and aluminum windows to allow for proton imaging. The low-profile flanges are required for clearance of magnet bores located periodically along the length of the BPAH. The bellows are included along the beamline for ease of installation. The OPCV is a pressure vessel designed to interface with the BPAH, IPCV, and proton imaging alignment system. The OPCV and BPAH are both designed to support full vacuum loads. Major considerations for the BPAH are thermal elongation, collapse of bellows, and stresses due to clamp supports. Lifting loads and static equivalent loads transmitted from the IPCV are additional considerations for the OPCV. Under ASME BPVC Section VIII Division 2 Part 5.2.4, Elastic-Plastic Stress Analysis Method, Paragraph 5.2.4.3(a), Global Criteria, the requirements for analysis and acceptance are defined for the load cases described. A finite element analysis (FEA) model, performed in ANSYS 2020 R1, evaluates the design of the OPCV and BPAH under the aforementioned ASME guidance and criteria.
Review on Non-Metallic Pressure Vessels for Cryogenic Applications
Authors: Yuan Yutong , Ge Zhoutian , Bai Jiangkun , Wang Guoying , Shi Jianfeng
Published: November 2022

On-board cryogenic storage of liquid hydrogen (LH) and liquid natural gas (LNG) plays an important role in the alternative gaseous fuel to reduce greenhouse gaseous emissions in transportation. Metallic pressure vessels are the common choice for liquid gases storage; however metallic materials are usually denser and corrosion-prone. Non-metallic pressure vessels have a better prospect of liquid gases storage due to some unique advantages, e.g., light weight, good corrosion resistance, and low thermal conductivity. This paper made a summarization about non-metallic pressure vessels for cryogenic application for further reference. Several cryogenic pressure vessels were introduced, including the application scenario and service conditions. The failure of non-metallic cryogenic pressure vessels was reviewed, and the corresponding causes and efforts for preventing the failure were introduced.
EPR Piping Material Study: Basic Characterization and Low Cycle Fatigue at Room Temperature
Authors: Seppänen Tommi , Alhainen Jouni , Arilahti Esko , Solin Jussi , Vanninen Rami , Pulkkinen Erkki
Published: November 2022

The 1963 ASME Section III design fatigue curve was generically applicable to a range of stainless steels in low cycle fatigue. In high cycle fatigue the behavior is sensitive to factors such as material strength, which raises questions about the applicability of the post-2009 ASME III stainless steel design fatigue curve as the generic and mandatory requirement up to 1011 cycles. In response, international codes and standards are investigating and incorporating opportunities for alternative design curves. Long-term Finnish research supports and application of risk-informed inspection and long-term operation strategies benefit from addressing material-specific behavior in fatigue management. In the ongoing study, stainless steel material batches representative of the EPR reactor in Olkiluoto have been selected for experimental fatigue research. This paper presents the first results on a 12″ schedule 140 Z2CND1812 N2 Class 1 pipe, including tensile properties and low cycle fatigue at room temperature.
Algorithm and Application of Pipeline In-Line Inspection Data Alignment
Authors: Cui Kaiyan
Published: November 2022

With the publication of GB 32167, pipeline in-line inspection has been executed comprehensively in China, which causes many problems such as mismatching, missing and misreporting of pipeline features, commanding inspection level of different providers to improve the inspection quality, data mining of multiple rounds of inspections and so on. In-line inspection data alignment can solve these problems efficiently. In this paper, a series of in-line inspection data automatic alignment experiences and rules are put forward, which can find out the error of in-line inspection data initially, realize the alignment of above-ground and underground features of pipeline, search and locate the combined defects of one inspection data, and match defects of different rounds of inspections. Thus problems such as locating pipeline defects and segments above ground, judging and analysis of different kinds of combined defects, quality verification of inspection data from different service providers, knowing the evolution of defects for pipeline, etc. can be solved. The methodology is applied to one certain product oil pipeline in China and the following results are obtained. Two ILIs data alignment rates of bends, girth wields and defects are 100%, 99.05% and 28.6%. The result shows that 2 dents intersecting the metal loss in 2016 ILI and 4 metal losses in the heat affected zone of girth weld in 2021 ILI are unreported. Reasons for low defects alignment rate are proposed. The results demonstrate problems such as misreporting and missing of combined defects, bends, girth welds and other features, as well as quality problems and logical errors existed in two rounds of ILIs data. The relevant advices were given to the pipeline enterprise finally.
Study of a Method for Determining the Fracture Toughness of Pipe Steel Based on Instrumented Charpy Impact Testing
Authors: Yatong Zhao , Jian Shuai , Lei Shi , Zijian Huang , Zhanfeng Chen
Published: November 2022

With the development of oil and gas transmission pipelines towards large diameter, and high strength, high steel grade pipeline steel materials represented by X80 have become the primary choice for oil and gas transmission pipelines. In order to achieve a low-cost and rapid acquisition of fracture toughness of pipeline steel in engineering, the feasibility of Charpy impact testing is investigated. In this paper, the test method of pipe fracture toughness based on instrumented Charpy impact test is investigated in detail, taking X80 pipeline steel as an example, and its fracture mode and expansion law are studied in combination with fracture morphology analysis. The dynamic J-integral of the material was obtained by the rate of change curve method of flexibility, and then the equation for solving the quasi-static J-integral based on the dynamic test method of CVN specimens was established. An innovative empirical equation for solving the J-integral based on the load-displacement curve was established based on the method of dimensional analysis. The results show that the method is suitable for rapid engineering solutions with good results, offering new possibilities for the assessment and study of weld fracture toughness.
Hydrogen Permeability of Self-Healing Copolymers for Use in Hydrogen Delivery Applications
Authors: Hitchcock Dale , Krentz Timothy , Mullins Anastasia , James Charles , Liu Qianhui , Wang Siyang , Gaikwad Samruddhi , Urban Marek W.
Published: November 2022

Safe and reliable fueling components are essential for large scale deployment of H2 fuel. Field data has shown that existing materials used in dispensing hoses do not meet current standards for component reliability. Currently modern copolymerization methods are under investigation to create a new platform for inner hose technologies using self-healable copolymers. Ideally these inexpensive self-healable copolymer inner layers will reduce the cost of H2 delivery hoses and extend their service life beyond 25,000 refills.

In this work gas driven hydrogen permeability measurements were performed on a variety of self-healing copolymer membranes all of which have exhibited excellent self-healing properties in previous studies. Copolymers were prepared with Poly(2,2,2-trifluoroethyl methacrylate/n-butyl acrylate) [p(TFEMA/nBA)] and Poly(methyl methacrylate/nbutyl acrylate) [p(MMA/nBA)]. Measurements were performed through a range of temperatures and source pressures. Additionally, the effects of composition, copolymer ratio, and molecular weight on the hydrogen permeability, solubility, and diffusivity were all studied. As expected, hydrogen permeation through the samples is proportional to the source pressure and inversely proportional to the molecular weight of the polymer. In general, the self-healing copolymers exhibit hydrogen permeabilities consistent with literature data for similar elastomers. These results suggest this class of self-healable copolymers may be promising candidates for use as inexpensive inner layers in hydrogen dispensing hoses with extended service life.
Evaluating and Mitigating Fatigue Risk of Choked Flow
Authors: Liu Yuqing , Diwakar Philip , El Jaouhari Ismat , Lin Dan
Published: November 2022

Uncontrolled manual operation of high energy vent lines could cause immediate fatigue failure at branch connections. Past failures have been attributed to high kinetic energy created due to choked flow at unprotected small-bore branch connections. In this paper, a risk-assessment method has been developed for choked flow in high energy systems. Computational Fluid Dynamics (CFD) tools were used to simulate formation and propagation of shock wave. A state-of-art method Fluid Structure Interaction (FSI) was used to investigate the dynamic pressure fluctuation in the piping system. Finite Element Analysis (FEA) was used to evaluate stresses and vibration responses at the toe of welds.

This study found the fatigue risk of choked flow is caused by high-frequency shell-mode vibration. However, unlike the other high-frequency shell-mode vibration phenomenon (the acoustic-induced-vibration) which propagates in the piping system, the risks of choked flow are found to be only in the immediate vicinity of the choking point and decays exponentially with distance. A vibration velocity index defined in recent publications is used and modified to predict the vibration stress in various pipe sizes and branch fittings. Mitigation options are also discussed in this paper.
Expertise in Materials Application Prevents Failures in Pressurized Components
Authors: Benz Ana , Bell Matthew
Published: November 2022

Pressure components are designed to prevent failures; their fabrication has detailed mechanical and manufacturing requirements. However, unforeseen contaminants, installation conditions, residual stresses, field heat treatments, and other unexpected circumstances often determine service life.

While a corrosion allowance aids when managing uniform corrosion losses, this is not the case for pitting, damage within crevices, stress corrosion, and high temperature-related cracks. To manage these losses, service experience and meticulous inspections, among others, are needed. This paper illustrates failures due to damage in localized areas. Practices needed to prevent these failures are emphasized.
Parametric Study on the Vibration of Small-Bore Piping Branch Connections
Authors: van Zyl Gys , Brodzinsky Richard
Published: November 2022

In vibration service, small-bore piping connections, especially unsupported cantilever configurations, are associated with a high level of concern as potential fatigue crack initiation locations. Various international guidelines and procedures address the assessment of piping vibration in general and of small-bore connections in particular. In this work, a review of these guidelines as applied to a specific class of small-bore connection was performed by means of a finite element parametric study on a large number of branch connections. The small-bore configuration evaluated in this work is an unsupported cantilever connection made using an integrally reinforced forged branch fitting with butt-welded joints. At the end of the branch is a flanged connection with either a blind flange only, or a single or double valve with a blind flange. For the parametric study a random distribution of run pipe diameter and thickness and branch pipe diameter, thickness, and length was used to evaluate a few thousand different small-bore configurations. Modal analysis was used to determine the relationship between stress and velocity at two critical locations: the weld between the branch fitting and header and the weld between the branch pipe and branch fitting. Results of the parametric study were processed and compared to the evaluation criteria of a number of established and upcoming guidelines and standards.
Development of Life Estimation Method for Nozzle Welds in Large Scale Piping of Modified 9Cr-1Mo Steel -Part II: Analytical Study
Authors: Takahashi Yukio , Shigeyama Haruhisa , Yaguchi Masatsugu
Published: November 2022

Creep strength-enhanced ferritic (CSEF) steels are widely used in fossil power plants operated in many countries and life management for the components made of these materials are of critical importance for plant operators. In particular, failures in welded joints in softened heat affected zone (HAZ) categorized as type IV failure have taken place widely in piping and boiler headers and prediction of such failure became a urgent requirement to be addressed. Following the simple longitudinal welds, weldments used for attaching various nozzles to main piping or boiler headers became the portions susceptible to type IV failure, stimulating the needs for prediction of their lives also. As a result, it turned out that a more sophisticated approach which can deal with complicated geometries involved in these weldments needs to be developed.

With such a background, the authors carried out an internal pressure creep test at 650 °C using the pipe of P91 steel with the outer diameter of 457.2 mm. Outline of testing condition as well as the results including the periodic damage inspection by several methods is presented in the accompanying paper whereas related analytical efforts will be described in this paper. Detailed finite element analyses were performed on nozzles with different geometries, incorporating creep deformation properties of each continuant of welded joint. Moreover, failure criterion based on inelastic strain energy density has been developed for softened HAZ, taking into account of the dependency on temperature, creep strain rate as well as stress triaxiality factor. Results obtained using these properties were compared with the test results in terms of the location and extent of cracking due to creep damage accumulation. They showed reasonable agreement, demonstrating the soundness of the developed approach.
Analysis on the Evolution Process of Dynamic Performance of Single Bolt Connection
Authors: Zheng Mingpo , Liu Zhifeng , Yan Xing , Chen Wentao , Li Ming
Published: November 2022

The connection quality of the bolted joints directly determines the service performance and reliability of the structure. However, there will always be a certain degree of loss in the bolt clamping force during the long-term service, accompanied by degradation of the mechanical performance. Herein, the experimental study on the single bolt connection was carried out to analyze the evolution process of dynamic performance. The clamping force was continuously monitored after tightening to obtain a quantitative analysis of its loss with and without external loads. The loosening curves of the clamping force with the service time was established respectively considering the main influencing factors. Transverse cyclic loads were applied to obtain the service loosening data of the bolt clamping force. The dynamic performance characterization parameters of the structure under different clamping forces were obtained through the modal test. On the basis of established force-performance relationship, the service conditions of the connection structure were evaluated to propose a performance evolution equation that varies over time. A comprehensive understanding of the service and evolution process of bolted joint was obtained through the experiment and analysis in this work. It provides an important reference significance in the performance prediction and control of bolted joints, which can help design a more reasonable structure.
New Evaluation Method for Seismic Fatigue Damage of Plant Pipeline (Quantitative Performance and Consideration of Application)
Authors: Inada Fumio , Sakai Michiya , Morita Ryo , Tamura Ichiro
Published: November 2022

In previous reports, it was shown that the cumulative absolute velocity (CAV) for each wave of the pipe seismic response corresponds to the vibration stress amplitude. A new seismic fatigue evaluation method was proposed by applying this relationship to Miner’s law of material fatigue damage. As a result, the cumulative fatigue damage can be calculated in proportion to the CAV of each wave to the power of 2.4. In this study, how the new method can be used to evaluate the cumulative fatigue damage quantitatively is considered. The cumulative fatigue damage was evaluated by the rain flow method as well as the new method where the parameters showing the effect of the concentrated mass and the pipe configuration on the vibration stress-velocity relationship were calculated accurately using the precisely analyzed mode function. The two results were found to be in good agreement. It is considered that this new method can give the evaluation result that envelops the pipes of the entire plant by appropriately setting the parameters.
High Pressure Connections Bolt Tightening – Requirements, Challenges, Problems, and Solution Proposition
Authors: Lutkiewicz Przemyslaw , Kirkemo Finn , Robertson David
Published: November 2022

There are many International and National standards for flanges and clamp connections. Different bolt pretension values are required by these standards. In general, two bolt tightening methods are recognized: by torque or tension tools. The tensioning method is more accurate; however, this requires temporary higher pretension. ISO-27509, for example will need temporary bolt pretension equivalent to 90–95% of yield strength, API 6A allows up to 83% of bolt yield strength. Metric and Imperial bolting types can be used. Both types have related thread standards with specific tolerance classes. It is known from field experience that in some cases combination of thread tolerances, bolt size, and tightening with tension tool, the induced interference between the nut and stud threads can prevent the turning of the nut preventing the correct pre-load. This paper investigates the problem and proposes some solutions to avoid jamming. Paper will present general overview and deep problem investigation based on Finite Elements nonlinear analysis results. The requirement for smooth nut turning thread clearance will be calculated. The thread tolerances will be compared and investigated in light of existing standards and beyond. The threads load carrying capacities will be also addressed in light of analytical calculations. The thread stripping phenomena will be also addressed. In addition, the torque tool method will be discussed in term of bolt stress and accuracy. The bolt scatter will be included in the discussion.
Constraint Effect on Fracture in Ductile-Brittle Transition Temperature Region (Report 2)
Authors: Hojo Kiminobu , Hirota Takatoshi , Nagoshi Yasuto , Fukahori Takuya , Sakima Kimihisa , Ohata Mitsuru , Minami Fumiyoshi
Published: November 2022

In order to predict fracture behavior of a structure with low constraint, tensile fracture tests using flat plate specimens with a surface flaw were performed at −80°C and −120°C in the ductile-brittle transition temperature (DBTT) region. The shape of the flat plate was 50mm thickness, 200mm width, and 500mm length. A semi-elliptical flaw of 5mm depth and 25mm length was introduced on the specimen’s surface. The measured KJ at fracture of the flat plate specimens were located between the predicted fracture probability bound of 5% and 95% of KJc from the laboratory specimen, C(T) and SE(B), including those for bending load obtained in the previous paper of the PVP2021 conference, Report 1. The Weibull parameters of the Weibull stress, m and σu, for the Beremin model and the parameters of the GTN model from the laboratory specimens, SE(B) and C(T) specimens, were used for the fracture probability prediction. Based on this verification result of the prediction procedure using the coupled model of the Beremin model and the GTN model, the plastic constraint correction coefficient χ, was proposed for fracture evaluation of a reactor pressure vessel. For simplification of the fracture evaluation, uniaxial loading plate models which accurately simulate the mechanical behavior of a reactor pressure vessel for representative PTS transients were applied for calculation of the coefficient χ.
The Development of a New Method to Compare the Fatigue Crack Growth Rates of Austenitic Stainless Steel Operating in a PWR Primary Coolant Subjected to Plant Realistic Temperature Loading
Authors: Howe Benjamin , Scenini Fabio , Burke Grace , Mann Jonathan
Published: November 2022

Fatigue Crack Growth Rates (FCGRs) of austenitic stainless steels can be significantly enhanced when tested in a high temperature water environment compared to those tested in air. Existing FCGR models are based on simple isothermal waveform loading. Recent work has highlighted that there may be a potential benefit into taking account of plant realistic loading waveforms in fatigue assessments as these may be less damaging than predictions based on simple loading conditions. As a result, new methods to account for these plant realistic loads have been developed to reduce excess conservatism of existing methods for predicting FCGRs.

To provide confidence in these methods, a previous UK thermomechanical fatigue testing programme has been conducted on Compact Tension (C(T)) specimens subjected to plant realistic loads, with the crack length and Crack Growth Rates (CGRs) being monitored in-situ using the Direct Current Potential Drop (DCPD) technique. This paper utilizes three different methodologies to evaluate the CGR of samples that underwent corrosion fatigue in different conditions namely; DCPD, post-mortem measurement of crack advance using Scanning Electron Microscopy (SEM), and the measurement of the spacing between striations to infer CGR.

It was found that DCPD provided a good global average of FCGRs at the crack front but does not capture local changes associated with the local microstructure.

Overall, it was shown that post-mortem examination for stage measurements can be reliably applied to infer CGR on samples that were not instrumented with DCPD.
Simulation of Compression Set of EPDM O-Rings During Aging
Authors: Zaghdoudi Maha , Weber Mike , Kömmling Anja , Jaunich Matthias , Wolff Dietmar
Published: November 2022

It is common practice in the application of finite element analysis to model compression set (CS) of elastomers during aging with two different material models according to the two-network theory of Tobolsky. The theory relies on the existence of two networks. The first one represents the original network after vulcanization and is sensitive to chain scission. The second network accounts for the formation of additional crosslinking during aging. Besides the use of user subroutines to describe the two-network model, an element overlay technique is also needed as the full set of both material behaviors did not exist for assignment to a single element. This element overlay technique is valuable for research and developmental purposes but makes extension to industrial usage quite challenging. Our goal is to simulate the CS of elastomers after long-term aging in a commercial finite element software with no need for extra subroutine codes or mesh superposition.

Ethylene propylene diene (EPDM) O-rings were aged in a compressed state at 75 °C, 100 °C, 125 °C and 150 °C for up to 183 days. Investigations of the experimental test results were used to identify material models and their parameters to develop a finite element model to simulate CS. The model was implemented in the finite element software ABAQUS/Standard® with a sequential temperature-displacement coupling.

Regarding the influence of temperature, the Arrhenius equation is adopted for the time-temperature relationship. The activation energy value that is required for the simulation is firstly determined from shifting the experimental CS results with the time-temperature superposition technique and plotting the shift factors in an Arrhenius diagram. The experiments were compared with the simulation results. Afterwards different activation energies were used in the simulation and discussed. A suitable choice of the activation energy value with regard to the reference temperature and the test temperature is presented. With the chosen activation energies, the match between numerical CS values after long-term aging and the experimental results was improved.