bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation on Carbon Emission Reduction of Non-Metallic Composite Pipeline for Hydrogen Transportation
Authors: Shi Jianfeng , Xia Ruoxi , Zheng Jinyang , Wang Zhongzhen , Zheng Xinyu , Yao Riwu
Published: November 2024

Non-metallic composite pipelines possess remarkable flexibility and exceptional resistance to corrosion. Compared to traditional metallic hydrogen pipelines, non-metallic composite hydrogen pipelines effectively mitigate the challenges of hydrogen corrosion and brittleness, positioning them as a promising alternative for large-scale, low-cost hydrogen transportation. Moreover, compared to traditional metal pipelines, non-metallic composite hydrogen pipelines exhibit lower wall roughness, effectively reducing hydraulic losses and offering carbon reduction advantages. Within the lifecycle of non-metallic composite pipelines, carbon emissions during the operational stage predominate. Consequently, this study proposes a method for calculating carbon emissions associated with the operational stage of non-metallic composite hydrogen pipelines. This method involves calculating the pipeline’s friction coefficient, followed by hydraulic loss calculations, and then analyzing carbon emissions based on the electricity consumption of the hydrogen pumps. The results obtained from this method were compared with standards, and a good agreement was demonstrated, confirming the method’s reliability. Subsequently, comparisons with metal pipelines revealed that utilizing non-metallic composite pipelines can effectively reduce carbon emissions. Additionally, the influence of pipeline diameter, hydrogen pressure, and flow velocity on friction losses and carbon emissions were analyzed in detail. The results of this study can guide the design of structural and operational parameters of non-metallic hydrogen pipelines, better leveraging the advantages of non-metallic composite pipelines in hydrogen transportation.
Investigation on Crack Propagation Failure Modes of Short Carbon Fiber Reinforced Polyethylene Electrofusion Joints
Authors: Zong Xinwei , Yao Riwu , Shi Jianfeng
Published: November 2024

Electrofusion joint is a principal connection method within non-metallic pipeline systems, and the mechanical strength of electrofusion joints is of great importance to achieve safe operation of pipeline systems. By manufacturing the electrofusion joints with short carbon fiber reinforced thermoplastic composites (SCFRTCs), the mechanical strength of electrofusion joints has been significantly improved, which shows great potential in mechanical enhancement of electrofusion joints. However, due to inherent stress concentrations within the joint structure and the limited ductility characteristic of SCFRTCs, SCFRTCs electrofusion joints are prone to crack propagation failure. Elucidating the failure mechanics of SCFRTCs electrofusion joints is vital for their continuous refinement and the secure operation of pipeline systems. In this study, SCFRTCs were first prepared and their fundamental mechanical properties were investigated. Subsequently, electrofusion joints were manufactured by SCFRTCs. A finite element models, combined with contour integral method, was developed to ascertain the crack propagation failure mode of SCFRTCs electrofusion joints. The influence of yield strength of SCFRTCs and wall thickness of joints on crack initiation of SCFRTCs electrofusion joints were systematically analyzed. The results demonstrated that the stress level in most areas along the wall thickness is low when the crack in the joint initiates. Increase in joint wall thickness and material yield strength can improve the internal pressure of crack initiation, but the utilization rate of materials strength decreases gradually. Additionally, short-term bursting tests of SCFRTCs electrofusion joints were conducted to determine the bursting pressures of electrofusion joints with varying wall thicknesses. By analyzing the crack morphology on the cross-sections of the bursting joints, it is found that after crack initiation, the crack is driven by internal pressure and gradually propagates until the joint fails. The results of this study can provide reference for the design and application of SCFRTCs electrofusion joints.
Mastering Critical Factors Affecting Toughness Degradation Is Key to Effective Use of Duplex Stainless Steel in Pressure Vessels
Authors: Tigerstrand Claes , Pilhagen Johan , Jonsson Jan Y.
Published: November 2024

Hence, the overall aim with the paper is to evaluate if leaner duplex stainless steels such as S32101 and S82441 justify a broader use as a cost-effective alternative to more established grades, i.e., S31803, S32205 and S32304 by including them in ASME Section VIII Division 2. This by considering their leaner alloying composition, and how it affects mechanical properties at both low and high temperatures of welded components for use in pressure vessels. The focus is on evaluating the potential allowable stresses in allowable temperature range using the stipulated design criteria for the different design routes. Moreover, to review and propose a method originating from the European pressure vessel standard EN 13445 on how to assess design against brittle fracture for both base and weld metal. Furthermore, discuss the risk for encountering embrittlement at the upper application temperature limit 316°C (600°F) in the ASME code which is strongly dependent on exposure time.
Inelastic Response Analysis of 2DOFs to Earthquake Motions Based on Superposition of Elastoplastic Response of Each Mode
Authors: Taniguchi Tomoyo , Shoji Yasumasa , Kimura Yukinobu
Published: November 2024

This paper develops the time history analysis of the elastoplastic response of the 2DOF, consisting of two masses and springs that exhibit bilinear hysteresis, being subjected to a base excitation, by superposing the time history of elastoplastic response of each mode. The essence of the proposed analysis is that the response of the 2DOF during the yielding of any springs consists of the mode frequencies, shapes and dampings that are readily specified by the eigenvalue problem employing the mass and the secondary stiffness of the spring yielded. First, the equations governing the response of each mode according to the state of spring and all quantities needed for them are described in detail. Next, the displacement history of each mode and that in the global coordinates system are numerically and simultaneously analyzed at every time step, because the yielding and turn-around points of each spring are only verifiable in the global coordinates system. Once the response exceeds the elastic limit or the turn-around points of each spring, the equations of motion of each mode are switched to those corresponding to the next state of springs. Finally, the accuracy of the proposed method is thoroughly discussed. Moreover, the force-displacement diagram of each mode is presented. The applicability of the SRSS method is also examined.
Method for Shape Imperfection Control in Buckling of Ellipsoidal Heads Using a 3D Laser Scanner
Authors: Shen Tao , Li Keming , Zheng Jinyang
Published: November 2024

Ellipsoidal heads are commonly used as components of pressure vessels. Shape imperfections such as out-of-roundness, deviations along the meridian, and bulges are caused by the manufacturing process of ellipsoidal heads, especially large-scale ellipsoidal heads assembled from formed segments. The shape imperfections significantly reduce buckling pressure of ellipsoidal heads, and thus it is essential to control shape imperfections. First, we measured the shapes of large-scale ellipsoidal heads using a 3D laser scanner that can provide the actual head shapes with more accuracy. The measured and perfect shapes were compared to determine the head shape imperfections. Based on the analysis results of head shape imperfections obtained from 3D laser scanning, a formula for characterizing shape imperfection of deviation along the meridian at head knuckle was proposed. Second, we established finite element models of ellipsoidal heads containing deviation along the meridian characterized by the above formula. Buckling of head models containing shape imperfections was simulated using the arc-length method, taking into account the effect of material and geometric nonlinearities. Third, we investigated the effects of shape imperfection magnitude and head wall thickness on buckling pressure of ellipsoidal heads under internal pressure. On this basis, limitation for the maximum allowable imperfection magnitude were determined. Finally, we proposed a new step-by-step procedure for shape imperfection control in buckling of ellipsoidal heads using a 3D laser scanner.
Plastic Collapse and Shakedown Analysis of PCHE Core with Channel Misalignment
Authors: Chen Xuanye , Shi Qianyu , Zhang Mingbao , Wang Fei , Liu Peng
Published: November 2024

Printed circuit heat exchanger (PCHE) has gained lots of attention from the academic and engineering fields for their high heat transfer efficiency with a surface-to-volume ratio up to 2500 m2/m3. Meanwhile, the diffusion bonding technique makes the PCHE suitable for high pressure and high temperature conditions. For some applications with high viscosity fluids, such as molten salt, liquid sodium, and liquid lead-bismuth alloys, large cross-section flow channels are often required to meet pressure loss requirements. And for that, two etching plates are often stacked with semi-circular channels face-to-face to get a larger cross-section flow channel, however, this may lead to channel misalignment in the diffusion bonding process due to the stacking accuracy and non-uniform temperature distribution. The channel misalignments will reduce the pressure boundary thickness of PCHE core and improve geometry discontinuity. Therefore, in this paper, a typical circular channel PCHE core with different misalignments is modeled to study its effect on plastic collapse and shakedown failure mode. Elastic-plastic stress analysis and shakedown analysis based on cyclic loadings are conducted considering pressure and temperature field. The results from this study can provide a reference for the design and manufacture of PCHE core in high viscosity fluid applications.
Some Challenges Regarding Qualification of Additive Manufacturing Components for a Nuclear Use – NUCOBAM Project
Authors: Bourgeois Myriam , Petesch Cecile , Verlet Romain , Misler Roxane
Published: November 2024

In the last decade, additive manufacturing (AM) technology has progressed significantly, and thus found its way into a number of industries. AM is particularly interesting for manufacturing components with complex geometries, which if produced via conventional manufacturing methods involve significantly more manufacturing steps and longer lead times for a limited number of pieces. The nuclear industry is no exception and has developed roadmaps that outline key steps that can potentially allow the usage of AM to produce nuclear reactor components. In this context, standardization can appear as a straightforward way to accelerate the qualification of these processes for a nuclear use. It is the overall goal of the project NUCOBAM (Nuclear Components based on Additive Manufacturing) to address the technical challenges associated with the production of reactor components via AM. The finality of the project is to develop a methodology for qualifying components produced via AM that complies with nuclear codes and standards. The AM method and alloy in scope of the project are Laser Powder Bed Fusion (L-PBF) and the stainless steel 316L. This paper presents the NUCOBAM project in more detail, including the challenges it reveals regarding standardization and the perspectives of qualification methodology.
Low Cycle Fatigue of Alloy 690 in the PWR Environment
Authors: Jayaram Kushal Gowda , Huret Joseph , Quibel Jonathan , Chitty Walter-John , Henaff Gilbert
Published: November 2024

Environmentally Assisted Fatigue (EAF) is one of the concerns for the extended operation of nuclear power plants. Over time, certain components experience thermal cycling while being exposed to the chemically active environment of Pressurized Water Reactors (PWRs). While many components in the primary loop are constructed from stainless steel, some critical parts are made from Alloy 690, a nickel-based alloy. Compared to the extensive research on EAF in stainless steels, only a limited focus has been placed so far on Alloy 690.

This study aims to assess the impact of the PWR environment on the fatigue life of Alloy 690. Low cycle fatigue tests were conducted in two different environments, namely air and PWR environments, at different strain amplitudes and strain rates. To investigate the mechanisms of EAF in Alloy 690, fracture surfaces were analyzed. In particular, fatigue crack growth rates as a function of crack depth were derived from striation spacing measurements. Additionally, microstructural changes, as influenced by Dynamic Strain Aging, in the air were examined using Transmission Electron Microscopy (TEM) on the specimens from interrupted tests at different stages of the fatigue life. A twofold ratio was expected according to the design rules, but the results indicate that there is minimal or almost no influence of the environment on the fatigue life of Alloy 690 in PWR conditions when compared to its behavior in an air environment. This observation is consistent with the crack growth rates, which demonstrate a constant growth in both the environments.
Design Margins of Fatigue Life of Carbon Steel Elbows and Tees Subjected to Reversing Dynamic Loads
Authors: Azuma Kisaburo , Fujiwara Keita , Kai Satoru , Otani Akihito , Furuya Osamu
Published: November 2024

Fatigue damage is a type of cumulative damage observed in piping systems. The fatigue damage is caused by various reversing dynamic loads including seismic loads. When the reversing dynamic loads produce plastic strain in each cycle, the loading cycles cause severe damage in the component, and thus the number of cycles to failure is relatively low. This type of failure due to the severe reversing load is called low-cycle fatigue. Past research revealed that some uncertainty is generally inevitable in predicting the number of cycles to low-cycle fatigue. Hence, it is of great importance to understand the mechanism of low-cycle fatigue and to ensure an ample margin in fatigue life evaluation in piping systems.

In this study, a series of shaking-table tests was carried out to study the mechanism of low-cycle fatigue and the design margin of pipe fittings. Three types of specimens were chosen as typical pipe fittings: elbows, equal tees, and reducing tees. All the specimens are made of JIS G3456 STPT370 seamless carbon steel pipe, equivalent to ASTM A106 Grade A. The response amplitudes of acceleration of each specimen were measured under the sinusoidal excitation of uniform frequency. We investigated the relation between input and output accelerations of the observed data, and then discussed the margin of pipe fittings based on the seismic design of nuclear piping systems.
Improved Analysis of Miniature Impact Toughness Tests
Authors: Arffman Pentti
Published: November 2024

A series of miniature impact tests was conducted. The analysis of instrumented impact curves was studied, and explicit procedures were sought to increase the consistency and reproducibility of results, as well as a decrease human influence on the analysis. These procedures are suggested for future considerations.

In order to smoothen noise and oscillations in the force-displacement curve, low-pass filtering of data is considered the most promising alternative. The method results in the most consistent elastic slopes and forces at onset of general yielding Fgy. A suitable cutoff frequency can be found by spectral analysis of the signal since it varies between test setups, but a phase shift in the resulting data needs to be addressed.

In the analysis, different characteristic points are identified on the force-displacement curve. When determining these points, the curve is sectioned into parts. Fitting Hooke’s line in the elastic region follows previously suggested methods. A polynomial of varying degree is fitted to the region following the elastic limit. Points of discontinuity reveal unstable fracture initiation and arrest locations, and a model consisting of linear and exponential terms is fitted to data beyond arrest. Once finalized, the points of interest in the instrumented impact curve are determined in accordance with ASTM and ISO standard guidance by searching the intersections of the fitted curves. Identification of the characteristic points in a consistent manner increases the confidence on material assessment from the data.
Proposed New Guidance for the Design of Fillet Welded Patches
Authors: Kummari Seetha Ramudu , Macejko Brian , Bifano Michael F. P. , Jones J. Ryan
Published: November 2024

Fillet welded lap patches may be applied to pressure vessels and piping that have suffered local wall thinning due to corrosion, erosion, and other damage mechanisms in the oil and gas, and petrochemical industries. This type of repair is considered temporary until there is an opportunity for permanent repair or replacement. The guidance provided in ASME PCC-2 Article 212 is widely used to design the fillet welded patches. The article provides a design procedure for determination of required thickness of the repair patches considering the bending stress due to eccentricity (thickness offset). However, ASME PCC-2 guidance results in significantly higher thickness for the fillet welded patches for most pressure vessels and piping applications, especially when the required thickness of the vessel shell is close to its nominal thickness. In this paper, conservatism associated with ASME PCC-2 guidance is discussed and an alternative, simplified, and less conservative procedure is proposed based on results from a parametric study of different design parameters using ASME Section VIII Division 2 Design By Analysis methodologies. Both two-dimensional (2D), and three-dimensional (3D) elastic-plastic finite element simulations were performed by varying lap patch-to-vessel shell thickness ratio, lap patch angle and length, etc. The differences between the trends from the 2D and 3D simulations is discussed along with a discussion of how the proposed methodology compares with the current ASME PCC-2 guidance.
Multi-Scale Failure Analysis Model for Cryogenic Pressure Vessel Under Combined Thermal Stress and Mechanical Stress
Authors: Cao Zhuangzhuang , Fu Bingjie , Bai Jiangkun , Wang Guoying , Zheng Jinyang , Shi Jianfeng
Published: November 2024

Cryogenic pressure vessels are promising types of containers, garnering significant attention due to their high energy storage density and low evaporative losses. These vessels are engineered with an outer shell, an insulation layer, and an inner vessel which is the fiber fully overwrapped metal liner. The core structural part, the fiber fully overwrapped metal liner, is designed to direct contact with cryogenic fluids, subjecting it to complex thermo-mechanical loads. Consequently, a comprehensive understanding of the thermodynamic responses of the vessels under cryogenic conditions is imperative to ensure their operational safety and reliability. Current analyses of the thermo-mechanical coupling in the liners primarily focus on the macroscopic thermal stresses caused by the mismatch in thermal expansion coefficients between the metal liner and the fiber wound layer, as well as the thermal stress between different fiber wound layers. However, the microscopic thermal stress caused by the difference in thermal expansion coefficients between the fiber and the matrix is not negligible. Therefore, this paper established a multi-scale model based on representative volume elements and conducts a thermo-mechanical coupled analysis of the fiber fully overwrapped metal liner. It predicts the distribution of thermal stresses within the fiber and matrix at various temperatures, as well as the failure pressure of the vessels.
Alternating Stress and Stress Linearization Analysis of Pipe Under High-Frequency Ultrasonics Cleaning Devices
Authors: Eslaminejad Ashkan , Crompton Andrew
Published: November 2024

This research explores ultrasonic vibration waveforms for cleaning nuclear power plant piping, aiming to improve flow dynamics and reduce radiation exposure. Various products using wide-frequency ultrasonic vibrations effectively remove particles from pipe interiors. Guided by American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants, this study monitors pipe vibrations, considering fatigue stress endurance limits and low-frequency bending mode stresses. Leveraging computational tools, particularly finite element analysis, enables precise assessments of piping responses to dynamic loads induced by ultrasonic transducers. Using linearization techniques, our analyses extract both bending and membrane stresses. External applications of ultrasonic transducers can induce high-frequency shell modes, leading to non-linear stress distributions within the pipe’s thickness. This paper advocates for utilizing linearized stress intensity derived from finite element linear dynamics analysis tools as a more conservative estimate of allowable alternating peak stress values, addressing the limitations of relying solely on bending stresses. Our research underscores the efficacy of linearized peak stress in evaluating stress-induced fatigue in high-frequency ultrasonic cleaning applications, contributing to optimizing maintenance practices and ensuring the structural integrity of piping systems in nuclear power plants.
Total Rotational Capacity of Threaded Connections in Pipe-Fitting Assemblies
Authors: Rusnak Cameron R. , Elfass Sherif A. , Rivas Allen J.
Published: November 2024

Fire suppression piping systems play a crucial role in minimizing the impact of unwanted fires. These systems primarily consist of welded or threaded connections at the pipe/fittings interface. Previous research conducted on threaded connections used the rotation at the pipe-fitting interface (about the face of the fitting) in order to calculate their rotational capacity, generating moment versus rotation response curves. While these methods are applicable in calculating the interface-rotational-capacity, the contribution of the fitting rotational capacity (bending of the fitting itself) has not been thoroughly explored.

Recent research conducted by the University of Nevada, Reno (UNR) has sought to address these gaps. The research team at UNR undertook a comprehensive experimental program involving threaded cast iron pipe-fitting assemblies to gain a deeper understanding of their total rotational capacity. This research has led to the development of a new procedure for calculating the total rotational capacity of threaded fittings.

Under UNR’s experimental program, 126 full-scale fitting assemblies were tested. The experiments included three fitting types (elbow, tee, and tee reducers), five (5) fitting sizes (1, 1.5, 2, 3, and 4 inches), and three configurations. All assemblies were filled with water and experiments were conducted at an internal operating water pressure of 140 ±5 psi.

UNR’s procedure goes beyond the conventional method by considering not only the rotation at the pipe-fitting interface (interface-rotational-capacity) but also the bending experienced by the fitting itself. This paper discusses the newly developed approach for evaluating the total-rotational-capacity of threaded assemblies. Given that this approach utilizes geometry to calculate total rotation, its applicability extends to both elastic and elastic-plastic regions providing there is no plastic hinging occurring in the pipe segment between the fitting and the sensor measuring the change in hypotenuse.
The Impact of FEA Modeling Techniques for Level 3 Dent Engineering Critical Assessment: Shell Vs. Solid Elements
Authors: Brust Alex , Xu Luyao , Kemp David
Published: November 2024

Engineering Critical Assessments (ECA) is crucial to evaluating the fitness for service of pipeline dents to comply with regulatory standards such as US CFR 49 part 192.712(c) and Canada CSA Z662 clause 10.10.4. For dents requiring a level 3 assessment, finite element analysis (FEA) is often employed to evaluate complex dent features categorized from in-line inspection (ILI) or direct examination of the pipeline. Various analysis techniques and element types exist within FEA for performing level 3 dent assessments. The appropriate analysis technique and corresponding element types (i.e., shell or solid elements) are often chosen by balancing the dent ECA’s complexity with computational accuracy and time. Shell elements are more computationally efficient than solid elements, however, the through-thickness stress distribution is more accurately captured with solid elements.

If computational time is of little concern, then solid elements are typically employed to obtain an accurate representation of the stress/strain distributions in and around the dent feature for further engineering assessment once FEA is completed. However, the nature of dent ECA rarely affords an assessment schedule with such a flexible time constraints. For instance, when the dent interacts with other complex deformation features such as metal loss, solid elements account for the local metal loss feature to achieve the most accurate results. As such, this study will compare the differences in using shell vs. solid elements for a dent ECA for plain dents using the same idealized indenter. Variations in the stress/strain results along with overall differences in the calculated remaining life of the feature will be assessed as a function of the solver time. The goal of the study is to provide guidance on how and to what extent the element type can affect the overall conclusions of two different element types of dent ECA.
Analytical and Numerical Solutions for the Elastoplastic Buckling Analysis of Shells of Revolution
Authors: Belone Gwladys , Le Grognec Philippe , Assaf Samir , Rohart Philippe
Published: November 2024

The buckling phenomenon is one of the main failure modes encountered in pressure vessels, due to the thin (shell-like) geometry of the structures involved and the predominant compressive stresses frequently observed under standard loads such as external pressure. This paper aims at presenting an analytical and numerical elastoplastic buckling analysis of classical shells of revolution usually encountered in pressure vessels. The purpose is first to provide new efficient (exact or approximate) closed-form solutions for the critical buckling loads of most usual components of pressure vessels under external pressure. Then, a finite element software is developed, which is dedicated to the buckling and post-buckling analysis of such shells, including arc-length and branch-switching methods. The analytical solutions and the numerical model are first validated thanks to finite element computations performed on a commercial software (Abaqus). Then, the numerical tool may provide reference bifurcation results so as to validate further analytical solutions in the idealized case of perfect shells. Finally, this home-made program will enable one to introduce easily both imperfections and (Bloch-)periodic boundary conditions in the model, for achieving parametric analyses of the imperfection sensitivity of the buckling problems in hand in a very efficient way.
Stress Relaxation Cracking (SRC) Susceptibility Comparison in UNS S34709 and UNS S34751 Stainless Steel Welds for Petrochemical Piping Applications
Authors: Pickle Tim , Fuenmayor Jean , Penso Jorge , Yu Zhenzhen
Published: November 2024

UNS S34751 and UNS S34709 austenitic stainless-steel alloys contain thermomechanical properties required for use in chemical processing pipe applications with 900–1200°F (482–665°C) operating temperatures. UNS S34751 alloy has demonstrated improved sensitization resistance compared to UNS S34709, a precursor for polythionic acid stress corrosion cracking (PA-SCC), due to lower carbon (C) content (0.01 wt.%) and higher niobium-to-carbon (Nb/C) ratio with lower overall niobium content. The addition of nitrogen (N) in UNS S34751 alloy provides similar thermomechanical properties compared to UNS 34709. Additionally, stress relaxation cracking (SRC) susceptibility in UNS 34709 welds has been documented thoroughly in literature and industry, which poses a problem for long term service life, while UNS S34751 welds have potential for improved SRC resistance without the need for post weld heat treatment (PWHT). In this paper, a literature review of S34751 is explored, and testing matrix of experimental SRC tests using a Gleeble 3500® thermomechanical simulator is developed for S34751 gas tungsten arc welded (GTAW) pipe samples in comparison to S34709 welds. Additionally, initial thermodynamic and kinetic CALPHAD calculations have been completed to analyze potential detrimental phases in S34751 in comparison to S34709, e.g., z-phase. SRC testing has been mostly completed in S34709 welds made with W34710 (E347-16) and S16880 (E16.8.2-15) weld filler, respectively, and SRC comparisons to S34751 are in progress. Current results show higher resistance to SRC in S34751 HAZ and FZ than S34709 FZ and W34710 FZ at 800°C. In the following year, a full comparative analysis between S34709 and S34751 HAZ and FZ, in addition to welds with alternative filler S16880, is planned, including SRC testing at 600–750°C temperatures, metallurgical characterization of intergranular and intragranular precipitates, and additional thermodynamic analyses to complement microstructural observations. Final conclusions on SRC susceptibility comparisons between S34751 and S34709 welds, including alternative fillers, will be made.
Pressure-Testing and Overpressure Protection Requirements for Section VIII Division 1 and Division 2 Pressure Vessels
Authors: Oland C. Barry , Lower Mark D.
Published: November 2024

Standards for boilers and pressure vessels are published in the Boiler and Pressure Vessels Code (BPVC) by the American Society of Mechanical Engineers (ASME). The intent of the design and fabrication rules specified in Section VIII, Division 1 and Division 2 of the ASME BPVC is to ensure safe and satisfactory performance for pressure vessels during their useful service lives. Design, pressure-testing, and pressure relief stress limits specified in Division 1 and Division 2 are consistent with the principles of limit state design theory, in which materials are assumed to have the minimum yield strength and exhibit an elastic-perfectly plastic stress-strain relationship with no strain hardening. These stress limits also provide a minimum design margin against plastic collapse (ductile rupture) equal to or greater than 1.5, where plastic collapse is the load at which overall structural instability occurs and excessive plastic deformation begins. Allowable stresses based on perfect plasticity and the principles of limit state design theory are considered by ASME to be a floor below which a pressure vessel constructed from any sufficiently ductile material will be safe. The actual yield strength and strain-hardening properties of materials permitted for pressure vessel construction give them an increased margin above this floor.
Thermal-Structural and Shock Event Evaluations of the Fueling Pellet Injection System for ITER
Authors: Martinez Oscar , Yaski Sumalatha , Smith Sarah , Godsey Kara , Rasmussen David , Lovett Gary
Published: November 2024

The United States is among seven partner nations in a collaborative effort to design, build, and demonstrate fusion’s ability to become a large-scale carbon-free energy source. Each country has its own domestic agencies that contribute directly to the ITER project. US ITER, which is a US Department of Energy Office of Science project managed by Oak Ridge National Laboratory, is developing world-class engineering solutions to the design, construction, and assembly of the burning plasma experiment that can demonstrate the scientific and technological feasibility of fusion. US ITER’s scope includes completing the preliminary and final design, qualifying materials and processes for manufacture and testing, executing manufacturing, and delivering the fueling pellet injection system (FPIS) to the ITER site for assembly. The US-ITER FPIS system is designed to inject cryogenically frozen pellets of deuterium-tritium into the plasma. The FPIS has two main functions: (1) providing a steady supply of deuterium and tritium fuel and (2) mitigating the impact of edge localized modes on the plasma-facing components.

The FPIS will have the capability to reside in three port cells within a tritium second barrier containment cask. Each pellet cask contains three flight tubes linking with penetrations on the torus cryopump housing and vacuum vessel: two for the magnetic high-field side pellet injection and one for the magnetic low-field side pellet injection. This paper presents the results of the thermal-structural analyses of the FPIS flight tube structural components when subjected to various loads such as electromagnetic loads; nuclear heating; and seismic, operational, and dynamic shock events. The resulting temperatures and stresses under combined conditions satisfied the design criteria to ensure the safe and reliable operation of the FPIS flight tubes within the vacuum vessel.
Safety Equivalency Evaluation of 1992 and 2023 Editions of the ASME Boiler and Pressure Vessel Code
Authors: Oland C. Barry , Lower Mark D.
Published: November 2024

Standards published by the American Society of Mechanical Engineers (ASME), including those for the construction of boilers and pressure vessels provided in the Boiler and Pressure Vessel Code (BPVC), are often incorporated into federal safety regulations. When a specific edition of the ASME BPVC, such as the 2015 edition, is incorporated by reference into a federal regulation, compliance with rules in this edition is mandatory. However, compliance is often not possible because new boilers and pressure vessels can be stamped only with the appropriate certification mark that corresponds to the edition of the ASME BPVC in effect when the boiler or pressure vessel was contracted for by the manufacturer.

This paper summarizes the technical rationale and engineering bases for explaining why rule changes to an obsolete edition of the ASME BPVC result in boilers and pressure vessels that are at least as safe as those constructed in accordance with rules specified in the 2023 edition, which is currently in effect. The process used to evaluate equivalent safety is based on a qualitative and quantitative comparative analysis approach in which the safety consequences and potential benefits of a rule change are assessed. Rule changes that result in boilers and pressure vessels with equal or greater safety are considered equivalent.
Environmental Fatigue – Early Results Revisited
Authors: Solin Jussi
Published: November 2024

VTT started in 1999 developing capability to conduct LCF tests in hot water environments and published first EAF results for 316NG in the 3rd Int. Conf. on Fatigue of Reactor Components (Seville 2004) and supplemented by results for titanium stabilized alloy 321 in paper PVP2006-93833.

This paper revisits these 20 years old experiments in aim to put their significance in perspective and to underline relevant findings on different performance of the stabilized and non-stabilized alloys. An interesting difference in secondary hardening was measured: alloy 321 hardens at RT air, but 316 NG rather in hot water. This finding was in line with the GE (Solomon & Amzallag) results at the time and with more recent research.

A warning on misinterpretation of the results is delivered. The tests were properly and reproducibly conducted, but — as most of the EAF facilities — the prototypical EAF devices were not able to provide compliance with the standard LCF test procedure of ASTM E606. The author recommends that the results presented in PVP2006-93833 should not be considered as quantitatively valid fatigue data, but comparison of the material responses within this set should be fine.
Fracture Mechanics Assessment of the Steam-Generator Tubesheet Plate Through a Modified Global Approach to Consider the Geometrical Effect on Fracture
Authors: Ancelet Olivier , Marie Stephane , Chapuliot Stephane , Parrot Aurore
Published: November 2024

Because of the carbon macro-segregation inherent to the large thickness flat component manufacturing, the Fracture Mechanics Assessment (FMA) of the Steam Generator Tube-Sheet (SG-TS) was required for flaws postulated close to the primary (and cladded) surface or the secondary (non-cladded) surface in France.

For those assessments, a flaw relying two holes is postulated, which represents a singular configuration compared to conventional FMA. Indeed the flaw is relatively small in comparison to the plate thickness and the crack length is limited by the distance between two holes. To take benefit of the geometry effect of this configuration, a methodology based on a modified global approach was proposed [1]. Applications of this methodology predict benefits of loss of constraint for several tubesheet configurations as underclad flaw or surface flaw with mechanical or thermomechanical loading. Significant constraint effect for underclad flaw and moderate effect for surface effect are estimated.

To validate the relevance of this approach, two actions are undertaken:

- In the first one, this methodology is applied on an experimental data base which different constraint effect. This data base contains numerous fracture tests performed by both EDF and Framatome on various specimen geometries extracted from a 18MND5 low alloy ferritic steel plate, in the brittle-to-ductile transition regime. C (T), SE(T), SE(B), and non-standard specimens.

- In the second one, this application rule is validated through the interpretation of fracture tests performed in the brittle to ductile transition temperature range of specimen representative of a flaw between two isthmuses.

The results obtained by this application appear accurate, providing very interesting perspectives for the assessment of the SG-TS, but also the assessment of other configurations such as small surface flaws configuration encountering constraint loss (loss of constraint called the small flaw effect).
Residual Stress Modelling in PWR Reactor Pressure Vessel Welded Joints
Authors: Robin Vincent , Breder Teixeira Lucas , Albrecht David , Hendili Sofiane , Hilal Sami , Pereira Alvarez Pablo , Delmas Josselin , Depradeux Lionel , Smith Mike C. , Vasileiou Anastasia
Published: November 2024

Residual stress and strain measurements were performed on a narrow gap weld mock-up consisting of a 130 mm thick low-alloy ferritic steel plate of type SA508 Grade 3 Class 1. A submerged arc welding (SAW) process with two beads per layer [1] was used. The thermal response during welding was recorded to provide information for numerical modelling of heat transfer. Detailed through-thickness measurements of residual stresses were made in the as-welded state using both incremental deep hole drilling and the contour method, and after post-weld heat treatment using deep hole drilling [2].

In this paper, a finite element model of the mockup is described as well as some recent modelling improvements achieved thanks to internal EDF R&D activities and within the framework of NeT Task Group 8 [3]. Comparison between measurements and simulations are in very good agreement. The results presented in this paper are useful for the validation of numerical models for the prediction of residual stress states, including the description of the material behavior which depends on phase fraction evolution and tempering effects. Post-weld heat treatment significantly relieves the welding residual stresses and a focus on its modelling is presented in this paper as it is seen as a key step of the manufacturing operation, reducing the level of residual stresses in reactor pressure vessel’s welded joints.
Experimental Validation of Theoretical Burst Strength Solution for Defect-Free Thick-Walled Pipes
Authors: Zhu Xian-Kui
Published: November 2024

The burst pressure of line pipes is an important strength property required in pipeline design and integrity management. Historically, the Barlow formula in conjunction with the ultimate tensile stress (UTS) of pipeline steels were utilized to estimate the burst strength of line pipes. However, the Barlow formula did not consider the plastic flow effect for ductile steels and is applicable only to thin-walled pipes (D/t ≥ 20). In 2006, this author proposed a new multiaxial plastic yield theory and obtained a theoretical Zhu-Leis solution of burst strength for defect-free thin-walled pipes in term of UTS and strain hardening exponent n of pipeline steels. The Zhu-Leis solution has been validated by various burst test data for thin-walled pipelines for a wide range of steel grades from Grade B to X120. Recently, this author extended the Zhu-Leis theory of plasticity to thick-walled pipes and obtained the Zhu-Leis solution of burst pressure for thick-walled pipes. The proposed burst pressure solution is applicable to both thin and thick-walled pipes.

To experimentally validate the proposed theoretical burst pressure solution, this paper obtains a set of burst test data for three thick-walled pipes in Grade B carbon steel with a nominal diameter of 2.375 inches and three nominal wall thicknesses, resulting in D/t = 15.4, 10.9, 6.9. Through comparisons, these burst data validate the theoretical burst pressure solution for thick-walled pipes. Moreover, two additional burst test datasets collected from literature for thin and thick-walled pipes further validate the proposed burst pressure solution for both thin and thick-walled pipes.
Comparison Between the Performance of Threaded Connections Versus Welded Connections in Pipe-Fitting Assemblies
Authors: Rusnak Cameron R. , Elfass Sherif A. , Rivas Allen J.
Published: November 2024

Fire suppression piping systems play a crucial role in minimizing the impact of unwanted fires. These systems primarily consist of welded or threaded connections at the pipe/fittings interface. While design codes, like the American Society of Mechanical Engineering (ASME) B31J, extensively address stress intensity/flexibility factors and rotational flexibility/stiffness in welded connections, threaded connections receive limited attention. Furthermore, ASME codes do not adequately address the failure modes of threaded fittings and their implications for system performance.

Recent research conducted at the University of Nevada, Reno (UNR) has sought to highlight these differences. The research team at UNR undertook a comprehensive experimental program involving cast iron threaded pipe-fitting assemblies to gain a deeper understanding of their performance. Under this program, 126 full-scale fitting assemblies were tested. The experiments included three fitting types (elbow, tee, and tee reducers), five (5) fitting sizes (1, 1.5, 2, 3, and 4 inches), and three configurations. All assemblies were filled with water and experiments were conducted at an internal operating water pressure of 140 ±5 psi. The experiments revealed three damage states, with leakage at the pipe-fitting interface being the predominant mode for small size fittings. This is typically different from welded connections. This paper discusses the performance of threaded fittings as compared to the published performance of welded fittings. It also discusses the pressing need to generate new stress and flexibility factors to accurately address the performance characteristics of threaded connections.
A Case Study for a Molten Salt Reactor Design
Authors: Rajasekaran Ramesh , Ching Hsu-Kuang , Bankston David , Deleo Francesco
Published: November 2024

The Molten Chloride Reactor Experiment (MCRE) is a pivotal design platform in developing TerraPower’s Molten Chloride Fast Reactor (MCFR) technology to validate some of its physics and operational principles. The Reactor Enclosure System (RXE) is a central component to this endeavour, serving as the primary containment for the reactor’s molten salt fuel and other internal parts. In adherence to the ASME Boiler and Pressure Vessel Code, specifically for Class A Metallic Pressure Boundary Components, the RXE is designed for various failure modes, including the critical assessment of combined creep and fatigue damage. Given the complex nature of the design process and the impracticality of conducting detailed evaluations of creep-fatigue life for each design iteration during the early stages, this study introduces a pragmatic approach. A comprehensive family of curves is generated to efficiently estimate the creep-fatigue life of one of the configurations of the RXE for a specific set of parameters. The first set of curves outlines allowable thickness concerning through-wall temperature difference and maximum wall temperature for three materials earmarked for RXE construction assuming a constant primary stress, for a fixed service life and load cycles. A second set of curves is introduced to elucidate the RXE’s sensitivity to variations in reactor service life and the number of load cycles within the fatigue damage evaluation. These curves, constituting a practical sizing approach, help designers to efficiently estimate the effects of incremental design modifications on creep-fatigue life, obviating the need for repetitive detailed evaluations. This paper delineates the methodology employed in generating both sets of curves, providing a comprehensive insight into the procedures undertaken. Additionally, the results of this work are presented, which will be a valuable contribution to the efficient design and evaluation of the RXE in the context of the MCRE and a similar procedure can be followed for other components.
Review of Shock Chilling Criteria in API 579-1/ASME FFS-1
Authors: Hay Clifford
Published: November 2024

Shock chilling can occur when a liquid or two-phase fluid comes into sudden contact with a warmer metal surface. Within operating facilities, there are multiple applications which warrant consideration, including pressure relief systems and equipment startup in light hydrocarbon services. The current screening criteria in API 579-1/ASME FFS-1 (2021) is based on an 8 ksi (55.2 MPa) limit for the maximum thermal stress occurring on the metal surface. In this study, an analytical method was utilized to determine transient temperature, stress, and crack-driving force profiles through the wall thickness for different cylinder geometries using postulated flaw sizes. Analytical results were compared against finite element models and show good agreement. Discussion is provided regarding the margin associated with the current API 579-1/ASME FFS-1 approach.

Example problem 3.10 of API 579-2/ASME FFS-2 (2009) (which involves assessment of a demethanizer tower in the cold end of an ethylene plant) is revisited using the updated calculation methodology.

Recommended updates to the assessment procedures in API 579-1/ASME FFS-1 are provided.