bluuebunny/crossref_metadata_2025_split huggingface dataset:
Statistical and Lifetime Characterization of PTFE Materials for Extreme Environments
Authors: Shinde Sannmit , Devito Dominic , Kenny Meghan , Gordon Ali P. , Poust Zachary , Drago Jim , Yang Ming-Hang , Nichols Paul 
Published: October 2021

Abstract
Most industrial manufacturing or process plants use bolted connections to transfer media from one location to another. Gaskets are often used to seal these systems as they offer high levels of leak mitigation; however, despite their nearly universal usage, testing done on gaskets has been limited. Historically, while industrial applications use gaskets at various temperatures and pressures, load retention tests have been conducted at a set temperature, time duration and compressive stress and report the result as load lost or retained. They do not account for longer time periods, the characteristics of the load loss over time or internal pressure the gasket is sealing. This current study seeks to change that. Traditional flat gaskets at thicknesses of 1/16” and 1/8” are leveraged against novel textured PTFE gaskets to compare load retention behavior across a range of styles. Different filler materials are tested as well, from aluminosilicate microspheres to barium sulfate and silica. Some design of experiments (DOE) methods are applied to characterize the factors that are most responsible for the load relaxation response of any particular type of gasket. A parameter from a previous study, efficiency, is used as an overall metric to quantify gasket performance. Furthermore, overall gasket deformation is examined to validate the statistical findings. Lastly, an empirical equation is presented that may be able to characterize gasket behavior across multiple loading and environmental conditions, as well as estimate the residual load carrying capacity of a gasket.
Background of Addition of Fatigue Crack Growth Rate Factors for Intermediate Strength Ferritic Steels in KD-4 of ASME Section VIII Division 3
Authors: Terada Susumu , Yoshida Toshio 
Published: October 2021

Abstract
In Table KD-430 and KD-430M of ASME Section VIII Division 3 (hereinafter called ASME Div. 3), there were no fatigue crack growth rate factors and threshold value of stress intensity factor range for carbon and low alloy steels with yield strength less than or equal to 620 MPa. These fatigue crack growth rate factors and threshold value of stress intensity factor range for ferritic steels with intermediate strength were also necessary for designing ASME Div. 3 vessels. We investigated the fatigue crack growth rates given in various standards. Especially Bloom’s paper related to ASME Sec. XI was investigated in detail. The test results on fatigue crack growth rate under various stress intensity range ratio in Bloom’s paper were compared with test results in other references. An equation for fatigue crack growth corrected by the stress intensity factor ratio was developed based on our investigation. The equation developed for fatigue crack growth was confirmed to agree with the test data in Bloom’s paper for negative and positive R ratios. Hence this equation, which was appropriate for a wide range of positive and negative R ratios, was proposed for ASME Div. 3. The addition of the threshold value of the stress intensity factor range for intermediate strength ferritic steels was also proposed. The fatigue crack growth rate factors at room temperature were provided in Table KD-430 and KD-430M of ASME Div. 3. As the operating temperature is higher than room temperature, the temperature correction is necessary for calculating fatigue crack growth. The temperature correction method in KD-4 of ASME Div. 3 was also proposed. These proposed changes except minimum threshold value were approved by Board in 2018 and they were reflected in 2019 Edition. The minimum threshold value was approved by the Board in 2021. It will be reflected in 2021 Edition. The background of these proposed changes is shown in this paper.
Thick-Wall Cylinder Reference Stress Crack Solutions for API 579-1/ASME FFS-1 Annex 9C
Authors: Thorwald Greg , Parietti Lucie 
Published: October 2021

Abstract
A new set of reference stress solutions for cracks in thick-wall cylinders were computed for addition in the next edition of the API 579-1/ASME FFS-1 standard, and are described in this paper. The geometry cases used ratios for the cylinder radius, wall thickness, crack depth, and crack length. The crack locations included axial, circumferential, internal, and external cracks. 3-D crack meshes were generated for each case to compute J-integral versus pressure result trends, which were used to determine the reference stress.
The Failure Assessment Diagram (FAD) method uses reference stress solutions to compute the Lr ratio on the FAD x–axis to evaluate cracks for plastic collapse; the FAD y-axis Kr ratio evaluates fracture failure. The elastic-plastic J-integral reference stress method will be briefly reviewed using results from this project.
A stress-strain curve was selected to represent typical material used for high-pressure components. The computed reference stress was shown to depend on the yield strength to tensile strength ratio, and a ratio of 90% was selected for use in this project.
Some shallow internal cracks in the thicker cylinder cases showed unexpected behavior in the J-integral versus pressure results, which prevented the reference stress from being computed. An alternative method was developed to use the maximum converged pressure as the nominal load to obtain reference stress solutions for those cases.
Proposed Method to Map the Elastic Follow-Up 3D Distribution Time History Using Finite Element Methods
Authors: Breach Michael 
Published: October 2021

Abstract
Elastic follow-up (EFU) is a complex and influencing phenomenon in pressure vessels and piping systems. It affects the performance of structural components at elevated temperatures. Quantification of elastic follow-up is challenging since it’s still not clearly defined in the ASME Boiler & Pressure Vessel Code. Pressure vessels and piping under operating load over time can exhibit mixed elastic follow-up trajectories due to inelasticity. Typically, secondary, and primary load are present at the onset which can redistribute over time due to strain accumulation and stress relaxation during elastic-follow-up. ASME Boiler & Pressure Vessel Code Div. 5, limits strain accumulation via criteria in regions outside of the elastic core. However, a method that directly addresses Elastic follow-up, would be advantageous in establishing actual margins against elastic follow-up during the design phase. The phenomenon has been well studied with various assemblages of uniaxial models, showing load and displacement controlled and mixed responses.
This study will present a method of assessing elastic follow up in finite element models. The method is based on the R5 elastic follow-up factor (EFF) expression that has been readily derived in the uniaxial case and employed by authors. Essentially the Von Mises equivalent strains are obtained from both a linear elastic and inelastic 3D finite element models subject to thermal (secondary) and pressure (primary) loading. The linear elastic model establishes the hypothetical initial elastic stress and the inelastic model will map the inelastic response through time. The Von Mises equivalent strains are then substituted into R5 expression, which are obtained from the onset linear-elastic model and the time varying inelastic model to map the elastic follow up and through time. The results are benchmarked against uniaxial results having combined primary and secondary loading.
Accurate Evaluation of Bolt and Clamped Members Stiffnesses Of Bolted Joints
Authors: Rousseau Rashique Iftekhar , Bouzid Abdel-Hakim , Zhao Zijian 
Published: October 2021

Abstract
The axial stiffnesses of the bolt and clamped members of bolted joints are of great importance when considering their integrity and capacity to withstand external loads and resist relaxation due to creep. There are many techniques to calculate the stiffnesses of the joint elements using finite element (FE) modeling, but most of them are based on the displacement of nodes that are selected arbitrarily; therefore, leading to inaccurate values of joint stiffness. This work suggests a new method to estimate the stiffnesses of the bolt and clamped members using FE analysis and compares the results with the FE methods developed earlier and also with the existing analytical models. A new methodology including an axisymmetric finite element model of the bolted joint is proposed in which the bolts of different sizes ranging from M6 to M36 are considered for the analysis to generalize the proposed approach. The equivalent bolt length that includes the contribution of the thickness of the bolt head and the bolt nominal diameter to the bolt stiffness is carefully investigated. An equivalent bolt length that accounts for the flexibility of the bolt head is proposed in the calculation of the bolt stiffness and a new technique to accurately determine the stiffness of clamped members are detailed.
Application of Load Release Factor Method in Thermal Expansion Load Imposed on Vessel Nozzle
Authors: Zhang Xiangbing , Duan Chenghong , Lu Mingwan , Luo Xiangpeng 
Published: October 2021

Abstract
The pressure vessels are connected by pipelines to form a system. Thermal expansion of the pipeline imposes an additional load on the nozzle of the connected vessel. There are two methods to deal with the thermal expansion load of pipeline in the design of pressure vessel: the partition method and the integrated method. A new Load Release Factor Method (LRFM) is proposed in this paper based on theoretical derivation. A spherical head with central nozzle is taken as an FEM (Finite Element Method) analysis model. The results show that a conservative design will be obtained by the traditional partition method, and the integrated method is the closest to the actual situation in spite of the large amount of calculation. However, compared with the traditional two methods, the LRFM can not only ensure the design margin but also reduce the calculation. This paper could be a reference for the analysis of pipeline thermal expansion load in the vessel design.
Materials Compatibility Concerns for Hydrogen Blended Into Natural Gas
Authors: Ronevich Joseph A. , San Marchi Chris 
Published: October 2021

Abstract
Hydrogen additions to natural gas are being considered around the globe as a means to utilize existing infrastructure to distribute hydrogen. Hydrogen is known to enhance fatigue crack growth and reduce fracture resistance of structural steels used for pressure vessels, piping and pipelines. Most research has focused on high-pressure hydrogen environments for applications of storage (&gt;100 MPa) and delivery (10–20 MPa) in the context of hydrogen fuel cell vehicles, which typically store hydrogen onboard at pressure of 70 MPa. In applications of blending hydrogen into natural gas, a wide range of hydrogen contents are being considered, typically in the range of 2–20%. In natural gas infrastructure, the pressure differs depending on location in the system (i.e., transmission systems are relatively high pressure compared to low-pressure distribution systems), thus the anticipated partial pressure of hydrogen can be less than an atmosphere or more than 10 MPa. In this report, it is shown that low partial pressure hydrogen has a very strong effect on fatigue and fracture behavior of infrastructure steels. While it is acknowledged that materials compatibility with hydrogen will be important for systems operating with high stresses, the effects of hydrogen do not seem to be a significant threat for systems operating at low pressure as in distribution infrastructure. In any case, system operators considering the addition of hydrogen to their network must carefully consider the structural performance of their system and the significant effects of hydrogen on structural integrity, as fatigue and fracture properties of all steels in the natural gas infrastructure will be degraded by hydrogen, even for partial pressure of hydrogen less than 0.1 MPa.
Reducing the Cost of Fatigue Crack Growth Testing for Storage Vessel Steels in Hydrogen Gas
Authors: Nibur Kevin , Somerday Brian 
Published: October 2021

Abstract
The service life of high-pressure hydrogen storage vessels at fueling stations is dictated by fatigue crack growth. Standards such as the ASME Boiler and Pressure Vessel Code (BPVC) provide a methodology for calculating the fatigue-limited design life of high-pressure hydrogen storage vessels, in which one essential input is the fatigue crack growth rate (da/dN) vs. stress-intensity factor range (ΔK) relationship measured for the material of construction in the service environment, i.e. hydrogen gas. These measurements must also be conducted at sufficiently slow cyclic loading frequency since decreasing the frequency usually results in faster crack growth rates. Generation of complete fatigue crack growth data sets according to standard test methods becomes very time consuming and expensive when these environment and frequency criteria are met. Two modifications to standard test procedures may reduce the time and associated costs related to this testing. One approach is to accelerate the rate at which ΔK changes with respect to crack extension. This can be accomplished by controlling the normalized K-gradient, C, where C = 1/K·dK/da. In addition, by using negative values of C (i.e. decreasing ΔK), multiple da/dN vs ΔK segments can be generated from a single test specimen. This paper summarizes the status of a project designed to identify the limits to which these two strategies may be employed to measure fatigue crack growth relationships for pressure vessel steels in gaseous hydrogen environments. These limits are defined as the bounds where loading history effects begin to alter the measured da/dN vs ΔK relationships.
Influence of Resistor Wire on the Maximum Stress In Electrofusion Joint
Authors: Hu Yurui , Xiang Guangte , Shi Jianfeng , Zheng Jinyang 
Published: October 2021

Abstract
Polyethylene (PE) pipes are widely used in oil and gas transportation, municipal construction. Electrofusion (EF) welding is one of the most commonly used connection method for PE pipes. The welding quality of EF joints is crucial to the safety of PE pipeline. Resistor wire is an important part of pipe fittings, and has great influence in final welding quality and strength of EF joints. In this paper, we discussed the influence of resistor wire for EF fittings in the aspect of selection of resistor wire materials and determination of structural dimensions. Resistivity and temperature coefficient of resistance (TCR) are two factors for material selection. In addition, the influence of resistor wire structure, i.e., resistor wire spacing, resistor wire diameter, on the stress distribution of EF joint was discussed through finite element analysis. The results revealed that the maximum stress in EF joint increase with the diameter of resistor wire, and is barely affected by resistor wire spacing.
Modeling the Fracture Behavior of SEN(T) Specimens With Crack In Heat-Affected-Zone
Authors: Kalyanam S. , Hill L. , Wilkowski G. M. , Hioe Y. 
Published: October 2021

Abstract
Single-Edge-Notch Tension, SEN(T) specimens have been used for fracture toughness determinations of base, weld, and heat-affected-zone (HAZ) materials. While the experimental results and computational finite element analysis (FEA) of SENT specimens with cracks in base and weld metals are relatively straight-forward, the analysis of SENT specimens with cracks in the HAZ poses several complexities that are highlighted through computational FEA in this work. SENT specimens have been found to provide good similitude for surface cracks in pipes, where a surface-cracked structure has lower constraint condition than bend-bars, SEN(B) and compact tension, C(T), specimens. The lower constraint condition gives higher upper-shelf toughness values, and also a lower brittle-to-ductile transition temperature. Also, the SEN(T) specimen eliminates concern of material anisotropy since the crack growth direction in the SEN(T) specimen is the same as in a surface-cracked pipe. While traditional methods of evaluation allow for a direct interpretation and application of elastic-plastic fracture mechanics approaches such as those that have evolved over the last five decades, for SEN(T) specimens with a flaw/crack in base materials and to some extent in weld materials, the presence of cracking in the HAZ complicates such routine approaches.
This work initially highlights findings from an earlier published SEN(T) experiment that was investigated and reported in support of the development of recommended practices and worldwide standards. From that experiment the presence of mode-mixity in HAZ fracture experiments was identified, and their characterization and determination of how to account for them in the recommended practices are under development. This work supplements the earlier experimental findings through computational FEA that shows the effects of mode-mixity and also highlights the differences when the initial crack is located in different regions of the HAZ and is of different lengths so as to keep the initial crack and the crack growth within the HAZ region. Of particular interest is the extent of crack growth that can be used for J-R and CTOD-R curves depicting fracture resistance curves for HAZ material cracks. Towards such an end, this work starts with an experimental discussion, followed by computational FEA to provide initial guidelines and a framework for future discussions. The goal being to create a better procedural analysis and treatment of the elastic-plastic crack growth in HAZ materials which will benefit the industry. The effects of mode-mixity in HAZ testing is critical to the development of crack growth resistance, CTOD-R and J-R curves employed in Engineering Critical Assessment (ECA) of pipelines.
Full-Scale Hydrostatic Test of Internal CFRP Repair on a Degraded Pipe With a Postulated Flaw for Short-Term Loading in Safety Related Nuclear Applications
Authors: Uddin M. , Orth F. , Hioe Y. , Krishnaswamy P. , Smith L. , Basavaraju C. 
Published: October 2021

Abstract
The use of Carbon Fiber Reinforced Polymer (CFRP) in nuclear industry is very limited and has not been used for nuclear safety related application until recently. In 2019, a new ASME Boiler and Pressure Vessel (BPV) Code Case N-871 was approved for internal repair of buried Class 2 and 3 nuclear safety related piping using CFRP for Service Levels A, B, C and D for a service period of 50 years. However, US Nuclear Regulatory Commission (NRC) has not yet accepted the Code Case. This Code Case provides a very detail guidance on materials, fabrication, installation, and design of CFRP repair for Class 2 and 3 nuclear safety related piping.
There are two aspects in designing CFRP repair for nuclear safety related piping application in terms of service duration — short-term use condition and end-use (end of service life) condition. The final design must satisfy both conditions in terms of available safety margin for the entire period of service. In contrast to end-use condition, some of CFRP materials’ degradation phenomena such as time effect factor due to sustained loading, material adjustment factors due to environmental exposure do not affect design calculation for short-term use. However, while end-use condition design criteria may control the final CFRP repair design, it is equally important to understand the available safety margin for short-term use.
In this paper, the available safety margin in ASME BPV Code Case N-871 was evaluated for internal CFRP repair of nuclear safety related piping for short-term use by conducting a full-scale hydrostatic test. The full-scale hydrostatic test was conducted on 40” outside diameter steel pipe. The pipe contains a postulated flaw (cut-out) with an internal CFRP repair designed according to ASME BPV Code Case N-871. The internal CFRP repair consisted of three unidirectional CFRP layers applied over the flaw 360° around the circumference at the inside surface of the pipe. Two glass fiber reinforced polymer (GFRP) layers were also applied as dielectric barrier and watertightness layer. The design pressure and temperature for the hydrostatic test was 84 psi and 72F. The pipe with internal CFRP repair was pressurized until failure (leak) occurred. The details of CFRP repair installation and hydrostatic test are presented in this paper. Finally, the available safety margin for short-term use was evaluated. Detailed analysis of strain gage data, bulging measurements and the video revealed that potential failure mechanism in the full-scale hydrostatic test of pipe with an internal CFRP repair and a postulated flaw (cut out).
Calculation of Outer Crack Stress Intensity Factors for Nozzle Junctions in Cylindrical Pressure Vessels Using FCPAS
Authors: Bozkurt Murat , Nash David , Uzzaman Asraf 
Published: October 2021

Abstract
Pressure vessels can be subjected to various external local forces and moments acting in combination with main internal pressure. As a result of the stress system set up, and in the presence of attachment welds, surface cracks can occur on the interior and exterior walls. If these cracks cannot be detected at an early stage, there is a real potential for the vessel to rupture with obvious dangerous consequences. The behavior of fractured or geometric discontinuity structures can be investigated with linear elastic fracture mechanics (LEFM) parameters. The stress intensity factor (SIF) is the leading one, and with correct calculations, it can produce the stress intensity in the crack tip region. In cylinder-cylinder intersections subject to local loads, the maximum stress distribution occurs in and around these opening areas and failure in the system usually occurs in this region.
Using this approach, the present study develops three-dimensional mixed mode stress intensity factor solutions on for external cracks on nozzle joints in cylindrical pressure vessels nozzle junctions for a variety of geometrical configurations. This was undertaken using a finite element approach and employing a bespoke software tool and solver, FCPAS - Fracture and Crack Propagation Analysis System — to create the finite element mesh and propagation characteristics. From this, a parameter study examining the influence of the crack shape, size and position was carried out with a fixed pressure vessel nozzle cylinder intersection geometry configuration and the appropriate stress intensity factors identified and reported. The FCPAS tool is shown to be an effective approach to modelling and characterizing cracks in pressure vessel nozzles.
Control Strategy for the Open Loop Control of Piezo Actuators in High Frequency Machine Hammer Peening Processes
Authors: Hiekel Alexander , Fiedler Maik , Kolouch Martin 
Published: October 2021

Abstract
Machine hammer peening is a production technology for the surface finishing of metal parts. A hammer peening tool is utilized to smooth and harden the work piece surface by an incremental micro forming process. Due to the production requirements of a high process force and a working frequency, piezo actuators represent a feasible solution for the process. Achieving high surface quality also requires the implementation of control structures to avoid the resonance frequencies. This paper presents the system prototype of a piezo-based tool for machine hammer peening (“PiezoPeening”). By introducing the system components and identifying relevant parameters, the elements of the control structure are determined and the integration of smart material into the tool is illustrated. Due to the relation between the working frequency, system resonance frequency and surface quality, an analysis by using different working parameters is performed for properly setting the working frequency and actuator pre-load. Based on the results, a control sequence is proposed to deal with different positioning systems.