bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress of Large Diameter Piping System Shoe Support
Authors: Ranjbaran Sadjad , Daneshvar Ghalelar Akbar
Published: October 2017

As codes and standards employ the beam theory to evaluate stress in piping systems, large diameter piping is therefore outside the domain of these codes and standards. To investigate any failure modes in these piping systems, more general codes such as ASME Sec. VIII Div.2 must be used. Research has shown that estimating local stress is important near the shoe support tip especially for large diameter piping systems and aboveground pipelines. To evaluate protection against local failure under an applied design load, a more accurate estimation method of ASME Sec. VIII Div.2, part 5 is applied by using elastic-plastic stress analysis procedures. For this purpose, finite element analysis is carried out along with distributed gravity loading and design pressure. Furthermore, parametric FEA studies are conducted on the effect of the ratio of pipe diameter to thickness, as well as the width and wrap angle of shoe support on the local stress of shoe support. The FEA results have been compared to semi-empirical formula for local stress in shoe support developed by AWWA standard.
Current Status of the ASME Materials Properties Database Development
Authors: Ren Weiju , Lin Lianshan
Published: October 2017

The ASME Materials Properties Database has been under development in the past few years to support the ASME Codes and Standards under the supervision of the Boiler and Pressure Vessel Code Committee on Materials. With the guidance of its Working Group on Materials Database, the project has completed the Phase I development for the Data File Warehouse that offers a depository for various files containing ASME Code Week records, materials test data from codification inquiries, and information associated with code rules development. While the database is in operation, the development has continued into Phase II to create a relational Digital Database that offers customized and relational schemas with advanced software functionalities and tools facilitating digital data processing and management. This paper discusses the current status of the project including its development management, database components and features, business operation, and future growth. Some issues and prospective resolutions for meeting the needs and requirements from Codes and Standards are also discussed.
Technical Basis for Characterization of Multiple Closely Separated Flaws Located in Different Planes
Authors: Blasset Sébastien , Nicak Tomas , Keim Elisabeth , Tiete Ralf , Obermeier Florian
Published: October 2017

Non-destructive inspection records have to be characterized before evaluation of acceptance if they are evaluated as material or fabrication flaws. When multiple flaws are detected by volumetric examination, the question of interacting flaws arises if they are close to each other: can the conventional approach based on individual flaw be applied?

Alternative flaw characterization requirements may be applied in lieu of using current codes by considering recent fracture mechanics research. In order to relax the conservatism of current interaction criteria, specific work was performed to describe interaction rules for flaws located in different planes. The proximity criteria are valid for linear elastic or limited elastic plastic material behavior : this is generally the case in large components.

This paper presents the technical basis including validation of the proximity criteria based on a specific component with several flaws and considering 3D numerical modeling using elastic-plastic material behavior in order to check if the plastic material behavior affects the selected proximity criteria. The component is submitted to uniform (pressure) and non-uniform loading (like thermal shock).
Characterization of Flow-Sound-Structure Coupling in Spring-Loaded Valves
Authors: El Bouzidi Salim , Hassan Marwan , Ziada Samir
Published: October 2017

The purpose of this study is to investigate the vibration mechanism of a spring-loaded valve placed in a “push-to-open” configuration in a piping system. A non-linear theoretical model of the valve vibration is developed to describe the interaction mechanisms between the unsteady flow through the valve, the acoustic field in the piping system, and the oscillation of the valve plate. The aim of this phenomenological model is to better understand the main system parameters causing the valve vibration. The model relies on a one-dimensional unsteady Bernoulli representation of the flow and a single degree of freedom model of the valve plate motion with impact conditions at the valve seat and lift limiter. Impact forces are determined through the means of a pseudo-force method. The model is cast in state-space form and solved using a fourth-order Runge-Kutta stencil. The predicted limit cycle amplitudes follow the same trends as experimental findings over the opening range of the valve. Modal characteristics are also consistent with experimental data.
Fracture Toughness and Deformation Behavior of Cast Austenitic Stainless Steels After Thermal Aging
Authors: Chen Yiren , Chen Wei-Ying , Xu Chi , Zhang Xuan , Li Zhangbo , Yang Yong , Rao Appajosula S. , Alexandreanu Bogdan , Natesan Krishnamurti
Published: October 2017

Cast austenitic stainless steels (CASSs) are used in the cooling system of light water reactors (LWRs) for components with complex shapes, such as pump casings, valve bodies, coolant piping, etc. The CF grades of CASS alloys are the cast equivalents of 300-series stainless steels (SSs) and show excellent mechanical properties and corrosion resistance. In contrast to the fully austenitic microstructure of wrought SSs, CASS alloys consist of a dual-phase microstructure of delta ferrite and austenite and are vulnerable to thermal aging embrittlement. The service performance of CASS alloys is of concern after long-term exposure to high-temperature coolant. In this work, we studied the effects of thermal aging and ferrite content on the fracture resistance of CASS alloys. Crack growth rate and fracture toughness J–R curve tests were performed on aged and unaged CASS alloys in simulated light water reactor environments. The impact of thermal aging on the cracking susceptibility was investigated and the effect of ferrite content was evaluated. Significant embrittlement was observed in the CASS alloys after aging at 400°C. To understand the embrittlement mechanism, microstructural characterizations were performed with transmission electron microscope. The thermal aging produced G-phase precipitates and phase separation in the ferrite, but did not affect the microstructure of austenite. Consequently, the ferrite was hardened considerably after thermal aging while the hardness of austenite phase remained unchanged. The difference in hardness created a high incompatible strain at the interface between ferrite and austenite, leading to fracture at phase boundaries.
Development of a Novel Test Method to Characterize Material Properties in Corrosive Environments for Subsea HPHT Design
Authors: Thodla Ramgopal , Holtam Colum , Saraswat Rajil
Published: October 2017

High pressure high temperature (HPHT) design is a significant new challenge facing the subsea sector, particularly in the Gulf of Mexico. API 17TR8 provides HPHT Design Guidelines, specifically for subsea applications. Fatigue endurance (i.e. S-N) and fracture mechanics design are both permitted, depending on the criticality of the component. Both design approaches require material properties generated in corrosive environments, such as seawater with cathodic protection and/or sour production fluids. In particular, it is necessary to understand sensitivity to cyclic loading frequency (for both design approaches), crack growth rates (for fracture mechanics approach) as well as fracture toughness performance.

For many subsea components, the primary source of fatigue loading is associated with the start-up and subsequent shutdown operation of the well, with long hold periods in-between, during which static crack growth could occur. These are the two damage modes of most interest when performing a fracture mechanics based analysis.

This paper presents the preliminary results of a novel single specimen test method that was developed to provide fatigue crack growth rate and fracture toughness data in corrosive environments, in a timeframe that is compatible with subsea HPHT development projects. Test data generated on alloy 625+ in seawater with cathodic protection is presented along with a description of how the test method was developed. A crack tip strain rate based formulation was applied to the data to rationalize the effect of frequency, stress intensity factor range (ΔK) and maximum stress intensity factor (Kmax).
A Comparison Study of Piping Loads Effect on Support/Foundation for Elastic and Rigid Vertical Vessels
Authors: Diaz-Barrie May , Szeto Edward , Stefanovic Radoslav , Chahal Ranbir
Published: October 2017

Modern petrochemical and chemical facilities consist of a significant number of pressure vessels. Adequate design of pressure vessels and their foundations have a significant impact on the safety and economics of such facilities. The design of pressure envelope components is well developed and specified in pressure vessel codes. A more less developed but significant aspect of the design of pressure vessels is the design of the vessel support and foundation. To adequately design the vessel support/foundation, engineers shall consider all the applicable loads on the vessel from attached piping and determine whether these loads could potentially entirely translate to the vessel base support/foundation. While methodology to determine these piping loads is well developed in literature and codes, there is a lack of guidance on how to determine the effect of these piping loads on the base support/foundation loading.

This paper is a continuation of the paper presented at the PVP2016 conference (63694 “Effects of Piping Loads on Vessel Supports and foundation” [1]), where the effect of piping loads on a vessel support/foundation was discussed. The paper demonstrated that when flexibility was introduced into a simple piping system, the loads transferred to the foundation/supports were reduced. This paper expands the study by evaluating piping loads from a more complex piping system attached to a tall vessel. To observe the differences, two different vessel heights and three different shell thicknesses are evaluated. The effect of piping loads (loading at the base) is calculated when the vessel and the nozzles are considered rigid and when flexibilities are introduced into the system. The more flexibility is introduced into the system, the more reduction in base loads is observed.
Effect of Hold Periods on the Corrosion Fatigue Crack Growth Rates of Austenitic Stainless Steels in LWR Coolant Environments
Authors: Platts Norman , Tice David R. , Panteli Alexandra , Cruchley Sam
Published: October 2017

Laboratory tests on austenitic stainless steel in simulated light water reactor (LWR) coolant environments have been shown to give rise to significant environmental enhancements of fatigue crack growth, especially at low cycling frequencies. The impact of LWR environments on fatigue crack growth has recently been codified in ASME code Case N-809 in terms of parameters such as rise time, stress intensity factor and load ratio. However, plant performance suggests that the application of these predicted environmental effects using current assessment procedures may be unduly pessimistic. This has led to significant number of studies of waveform shape (specifically hold periods) on the corrosion fatigue crack propagation in austenitic stainless steels in LWR environments. The main emphasis of this work addresses the ability of hold periods to cause retardation of environmental crack growth rates.

There has been substantial variability in results of these studies with some authors reporting significant retardation whilst others have failed to observe retardation, or even reported additional environmental enhancement of crack growth rates for nominally similar loading waveforms. Although some of the variability may be accounted for in terms of material composition, there remains a considerable uncertainty both on the impact of holds, especially at different positions in the waveform, and the manner in which hold periods should be taken into account in plant assessments (e.g. in assessment procedures such as N-809). The current paper provides a critical review of published data on the effect of hold periods on corrosion fatigue in LWR environments as well as presenting new targeted data generation and analysis in order to rationalise the reported observations.
Predictions of ICHAZ Cyclic Thermo-Mechanical Response in GTAW Process for 9Cr Steels
Authors: Mac Ardghail Padraig , Barrett Richard A. , Harrison Noel , Leen Sean B.
Published: October 2017

This work is concerned with the development of a modelling framework to predict the effects of tempered-untempered martensite heterogeneity on the thermo-mechanical performance of welded material. A physically-based visco-plasticity model for the inter-critical heat-affected zone (ICHAZ) for 9Cr steels (e.g. P91, P92) is presented in this work, with the ICHAZ represented as a mixture of tempered and untempered martensite. The constitutive model includes dislocation-based Taylor hardening and damage for different material phases. A sequentially-coupled thermal-mechanical welding simulation is conducted to predict the volume fraction compositions for the various weld-affected material zones in a cross-weld specimen. The out-of-phase cyclic thermo-mechanical (25°C to 600°C) performance of notched and plain samples is comparatively assessed for a range of different tempered-untempered martensitic material heterogeneities. It is shown that the heterogeneity in a simulated cross-weld material is highly detrimental to thermal cyclic performance.
Target Reliability Index for Load and Resistance Factor Design of Class 2 Carbon Steel Pipes
Authors: Avrithi Kleio , Mendoza Ramiro
Published: October 2017

The use of the Load and Resistance Factor Design (LRFD) for Class 2 nuclear piping can be an alternative of the traditional Allowable Stress Design (ASD) method currently used in the ASME Boiler Pressure Vessel Code, Section III, Div. 1 providing the benefit of a known and consistent reliability for the designed piping. The design uncertainties and the necessary safety margin are evaluated for each equation for all service levels by considering the applied loads (e.g., earthquake, deadweight, internal pressure, etc.) and the resistance of steel, in the form of either the yield or ultimate strength, as separate variables described by their mean value, distribution, and coefficient of variation. The procedure yields different partial safety factors for each load and the resistance in opposition to the one safety factor used in each of the ASD equations of the Code. Although LRFD equations have been developed in the past, a range of possible partial safety factors were assigned to the variables, corresponding to different levels of reliability. This paper discusses the method used, namely calibration, for achieving same reliability as in the Code equations, and the progress made to assess a minimum target reliability index or else acceptable probability of failure for the LRFD equations that consider the earthquake load for pressurized pipes as well as the design for internal pressure for Class 2 nuclear pipes made of carbon steel.
A Comparative Study of the Thermal-Mechanical Behavior and Fatigue Life Predictions of Different Coke Drum Support Skirt Designs
Authors: Prueter Phillip E. , Bifano Michael F. P. , Kummari Seetha Ramudu , Hantz Benjamin F.
Published: October 2017

It is well known that coke drums are subjected to severe operating conditions that can lead to progressive plastic strain accumulation and related fatigue damage and cracking. The difficulties of performing an insightful, useful coke drum analysis are numerous. There are a variety of uncertainties and randomness in temperature and stress during the heating and quench portions of the cycle that limits the value of conventional analysis for remaining life prediction. Further complicating the issue, the progression of damage in coke drums often involves gross plasticity, permanent dilation, and variable bulging in the pressure boundary. Since the accumulation of damage in the drum is a history (or path) dependent process, a snapshot of strain or even distortion data has limited value in quantifying damage or remaining life. Additionally, ASME Code elastic-based fatigue methods, with plasticity correction factors, that have been used for coke drum assessments in the past are technically invalid when ratcheting (incremental plastic strain accumulation) is occurring. More modern fatigue methods and damage models may be required to address the permanent irreversible damage and material degradation that is produced during cycling.

To date, there are no standard methodologies developed in the refining industry for coke drum life prediction, as is evidenced by the first edition of API Technical Report 934-G [1] (published in April 2016) as well as the limited analytical work typically performed to validate coke drums during the design phase. Simplified approaches have generally been used to attempt to define trends rather than developing more fundamental analytical insight into structural response. API 934-G [1] generally attributes cracking in the bottom cones and skirts of coke drums to cyclic thermal stresses introduced during the fill and water quench portions of the operating cycle, but indicates that weld misalignment can also be a contributor to crack initiation and propagation. In this study, the thermal-mechanical behavior of multiple coke drum skirt designs, including forged, welded, and sliding configurations is investigated using elastic and elastic-plastic finite element analysis (FEA), and corresponding fatigue life predictions are discussed for each type of design. Additionally, the effect of skirt slots is quantified. Finally, a cyclic plasticity material model is employed to establish shake-down, and a modern strain-based fatigue method is implemented, including a critical-plane approach as documented in Part 14 of API 579-1/ASME FFS-1, Fitness-For-Service, (API 579) [2], Welding Research Council (WRC) Bulletin 550 [3], and Reference [4]. These results are compared to more conventional base metal and welded fatigue predictions.
Enhanced Creep Life Evaluations for Grade 91 Circumferential Weldments
Authors: Cohn Marvin J.
Published: October 2017

The basic power piping creep life calculations consider the important variables of time, temperature and stress for the creep rupture properties of the unique material. Some engineering evaluations of remaining life estimate the applied stress as the design stress obtained from a conventional piping stress analysis. Other remaining life evaluations may assume that a conservative estimate of the applied stress is no greater than the hoop stress due to pressure. The creep rupture properties of the unique material are usually obtained from the base material creep rupture properties. The typical methodologies to estimate remaining life do not consider the actual applied stress due to malfunctioning supports, multiaxial stress effects, axial and through-wall creep redistribution, time-dependent material-specific weldment creep rupture properties, residual welding stresses, and actual operating temperatures and pressures.

It has been determined that the initiation and propagation of Grade 91 creep damage is a function of stress to about the power of 9 at higher applied stresses. There have been many examples of malfunctioning piping supports creating unintended high stresses. When the axial stress is nearly as high as the hoop stress, the applicable corresponding uniaxial stress for creep rupture life is increased about 30%. Multiaxial stress effects in circumferential weldments (e.g., when the axial stress is nearly as high as the hoop stress) can reduce the weldment creep life to less than 1/6th of the predicted life assuming a uniaxial stress or hoop stress due to pressure only.

Since 2012, the ASME B31.1 Code has required that significant piping displacement variations from the expected design displacements shall be considered to assess the piping system’s integrity [1]. This paper discusses a strategy for an enhanced creep life evaluation of power piping circumferential weldments. Piping stresses can vary by a factor greater than 2.0. Consequently, the range of circumferential weldment creep rupture lives for a single piping system may vary by a factor as high as 40.

Although there is uncertainty in the operating times at temperatures and pressures, all of the weldments within the piping system have the same time, temperatures, and pressures, so the corresponding uncertainties for these three attributes are normalized within the same piping system. Since the applied stresses are the most important weld-to-weld variable within a piping system, it is necessary to have an accurate evaluation of the applied stresses to properly rank the creep rupture lives of the circumferential weldments. This methodology has been successfully used to select the lead-the-fleet creep damage in circumferential weldments over the past 15 years.
Quality Assurance and Technology Qualification for Additive Manufacturing of Metallic Pressure Components
Authors: Mandeville Matthew K. , Brongers Michiel P. H. , Tang Fei
Published: October 2017

Additive manufacturing (AM), also known as three-dimensional (3D) printing of materials, has gained popularity in recent years. AM can be used to produce customized products with complicated geometries that are difficult to manufacture otherwise. While technology for plastic components has spread rapidly, production methods for metallic components are still in their infancy. The major area of concern is quality assurance to provide confidence in the reproducibility and reliability of the parts. This is of particular importance for critical service applications, such as in pressurized environments. While the details of the methods of AM vary, from laser sintering of powders to electron beam welding, there are key concepts that connect all the various AM methods and that should be capitalized on for Technology Qualification (TQ). This paper aims to review the needs for the quality assurance, applying the concepts of technology qualification, threat assessment, and risk based verification to the technology of additive manufacturing of metallic pressure retaining parts.
Unified Viscoplastic Model Coupled With Damage for Evaluation of Creep-Fatigue of Grade 91 Steel
Authors: Islam Nazrul , Dewees David J. , Hassan Tasnim
Published: October 2017

A continuum damage mechanics (CDM) coupled unified viscoplasticity model has been developed to predict the creep-fatigue life of modified Grade 91 steel. A tertiary creep model termed MPC-Omega codified in Part 10 of API (and also implemented in the ASME BP&V Code for Grade 22V and more recently Grade 91 Steel) is also employed for creep damage evaluation. As MPC-Omega has a direct relationship with Larson-Miller parameter (LMP) coefficients, creep damage coefficients in the unified constitutive model (UCM) are tied with MPC-Omega coefficients in order to utilize WRC and API 579-1 Grade 91 creep rupture database. The model is validated against long-term creep, LCF, creep-fatigue and TMF experimental responses at T = 20–600°C.
Hydrogen Isotope Permeation and Trapping in Additively Manufactured Steels
Authors: Karnesky Richard A. , Chao Paul , Buchenauer Dean A.
Published: October 2017

Additively manufactured (AM) austenitic stainless steels are intriguing candidates for the storage of gaseous hydrogen isotopes because complex vessel geometries can be built more easily than by using conventional machining options. Parts built with AM stainless steel tend to have excellent mechanical properties (with tensile strength, ductility, fatigue crack growth, and fracture toughness comparable to or exceeding that of wrought austenitic stainless steel). However, the solidification microstructures produced by AM processing differ substantially from the microstructures of wrought material. Some features may affect permeability, including some amount of porosity and a greater amount of ferrite. Because the diffusivity of hydrogen in ferrite is greater than in austenite (six orders of magnitude at ambient temperature), care must be taken to retain the performance that is taken for granted due to the base alloy chemistry. Furthermore, AM parts tend to have greater dislocation densities and greater amounts of carbon, nitrogen, and oxygen. These features, along with the austenite/ferrite interfaces, may contribute to greater hydrogen trapping.

We report the results of our studies of deuterium transport in various austenitic (304L, 316, and 316L) steels produced by AM. Manufacturing by Powder Bed Fusion (PBF) and two different blown powder methods are considered here (Laser Engineered Net Shaping® (LENS®) and a Direct Laser Powder Deposition (DLPD) method with a higher laser power)). The hydrogen permeability (an equilibrium property) changes negligibly (less than a factor of 2), regardless of chemistry and processing method, when tested between 150 and 500 °C. This is despite increases in ferrite content up to FN = 2.7. However, AM materials exhibit greater hydrogen isotope trapping, as measured by permeation transients, thermal desorption spectra, and inert gas fusion measurement. The trapping energies are likely modest (<10 kJ/mol), but may indicate a larger population of trap sites than in conventional 300-series stainless steels.
Commentary on Recent Changes in ASME B31.3 Post Weld Heat Treatment Requirements and the Effectiveness of Weld Preheat
Authors: Prueter Phillip E. , Smith Katelyn J. , Macejko Brian , Shipley Kraig S.
Published: October 2017

The 2014 Edition of ASME B31.3, Process Piping [1], introduced significant changes to the post weld heat treatment (PWHT) requirements for P-No. 1 carbon steel materials. In particular, PWHT is no longer a mandatory requirement for any wall thickness provided that multi-pass welding is employed for wall thicknesses greater than 5 mm (3/16 of an inch) and a minimum preheat of 95°C (200°F) is implemented for wall thicknesses greater than 25 mm (1 inch). Detailed fracture mechanics analyses have shown that the lack of a mandatory PWHT requirement for thicker P-No. 1 components may result in a significant increase in risk for brittle fracture failures due to near-yield level weld residual stresses. Given the concern throughout the pressure vessel and piping community regarding potential brittle fracture failures, this updated PWHT guidance is examined.

Impact testing requirements and exemption curves were introduced in the 1987 Addenda [2] of ASME Section VIII Division 1 (VIII-1) [3] in Paragraph UCS-66 and extended into ASME Section VIII Division 2 (VIII-2) [4]. During the VIII-2 rewrite in 2007 [5], the available technical and historical basis for the UCS-66 exemption curves was examined and improved to reflect modern fracture mechanics standards. The result of that effort was a systematic approach that can be modified for particular geometries and assumed flaws, if desired. The method used the most modern, fracture mechanics approach for welds in API 579-1/ASME FFS-1, Fitness-For-Service, (API 579) [6] based on the failure assessment diagram (FAD). As a result of explicitly accounting for weld residual stress, two separate sets of exemption curves are provided in VIII-2 [4]; one set for as-welded components and another set for PWHT components. In this paper, a similar approach is summarized to generate exemption curves by establishing newer as-welded and PWHT curves using the Fracture Toughness Master Curve (Master Curve) as documented in upcoming Welding Research Council (WRC) Bulletin 562 [7]. The increased propensity for brittle fracture in as-welded components versus PWHT components is clearly highlighted using this approach. The Master Curve, in conjunction with the elastic-plastic fracture mechanics employed in API 579 [6] provides a means to develop exemptions curves anchored in state-of-the-art fracture toughness technology that can be directly tied to different reference flaw sizes. Additionally, commentary on the appropriateness of the current ASME B31.3 [1] PWHT requirements is offered and the effectiveness of using weld preheat in lieu of PWHT as permitted in the National Board Inspection Code (NBIC) [8] is examined using simplified computational weld analysis.
Crack Growth Rates for Evaluating PWSCC of Thick-Wall Alloy 690 Material and Alloy 52, 152, and Variant Welds
Authors: Jenks Amanda R. , White Glenn A. , Crooker Paul
Published: October 2017

Due to the widespread use of thick-wall Alloy 690 and its corresponding weld metals Alloys 52 and 152 in various replacement, repair, mitigation, and new plant pressurized water reactor (PWR) applications, there is a need in the industry for an equation or methodology for predicting crack growth rates (CGRs) for primary water stress corrosion cracking (PWSCC) of these materials. Although there have been no indications of PWSCC reported in these materials in PWRs to date, there is the possibility that such an indication could be reported in the future or the possibility that a manufacturing defect could be conservatively interpreted as PWSCC. Crack growth rates are thus needed to support leaving such an indication in service for a justified period of time. In addition, safety assessments of hypothetical PWSCC flaws require prediction of PWSCC crack growth rates for these materials, so as to set appropriate inspection intervals. Current inspection intervals were selected to be conservative pending a consensus CGR model.

Example applications for which PWSCC CGRs are needed to determine appropriate reexamination intervals include Alloy 690 penetration nozzles attached to the inside of the reactor pressure vessel top head with Alloy 52/152/variant welds, and Alloy 52/152/variant weld inlays and onlays used to mitigate Alloy 82/182 piping butt welds.

An international PWSCC CGR Expert Panel was organized by EPRI, with the participation of national laboratories sponsored by the US Nuclear Regulatory Commission (NRC),1 to support the development of such PWSCC CGR equations. A database of over 500 Alloy 690 CGR data points and over 130 Alloy 52/152 CGR data points using thick-wall compact tension specimens from seven research laboratories was compiled, scored for data quality, and assessed to determine the effects of numerous parameters such as temperature, crack-tip stress intensity factor, yield strength, and crack orientation. The methodology and results of these statistical analyses are presented in this paper. It should be noted that this paper provides a status of the ongoing work, which is planned for completion in late 2017.
A Detailed Proposal for an Oxidation Test for Flexible Graphite
Authors: Bond Stephen
Published: October 2017

While the oxidation of graphite in gaskets is a well known phenomenon it is often poorly quantified and the factors affecting it not always well known. There are some standard tests that can be used to determine graphite quality. While many of these material standards concentrate on the compositional impurities (sulfur, chlorides etc.) and the ash content; these are indicative of other properties and they are no real indication of oxidation performance. Recently, some test methods have been published that suggest a method for measuring oxidation performance; however, they have some shortcomings or constraints.

Using modern, standard TGA (ThermoGravimetric Analysis), the work presented in this paper aims to provide a more detailed standard test that can be used to measure the oxidation rate of graphite in flowing air for a given set of time and temperature conditions. The paper will show what other conditions are critical and which are less significant in specifying a standard test. This will lead to the presentation of a suggestion for an improved standard test that builds on and further codifies the tests currently published.

Finally, this paper will show the oxidation rates of a variety of different commercial graphite grades to illustrate the vast range of oxidation rates that are possible from the various grades of graphite.
Additive Manufacturing of Pressure Vessels (With Plating)
Authors: McNelly Brendan P. , Hooks Richard L. , Setzler William R. , Hughes Craig S.
Published: October 2017

Additive manufacturing (AM) allows for product development with light weight, fewer machining constraints, and reduced costs depending on the application. While AM is an emerging field, there is limited research on the use of AM for pressure vessels or implementation in high stress environments. Depending on the design approach and limitations of traditional material-removal fabrication techniques, AM parts can achieve high strength-to-weight ratios with reduced manufacturing efforts. Coupling AM with alternative metal and composite materials allows for unique designs that have high strength-to-weight ratios for pressure-based applications. The Johns Hopkins University Applied Physics Laboratory (JHU/APL) has conducted research on a number of these composite designs, focusing on the use of carbon fiber or metal plating with the AM materials.

Before implementing AM in field tested prototypes, JHU/APL performed strength limitation tests on AM pressure vessels (PVs) in the laboratory to prove their effectiveness. PVs constructed with varying thicknesses and coating techniques were divided into three groups, each with a uniform wall thickness that provided a congruent surface area to withstand higher pressures. These PVs were then paired with one of three coating/plating technologies, forming a trade matrix of varying AM thicknesses and plating techniques. Once fabricated and plated, these test PVs were hydro-statically tested at increasing pressure levels. This pressure testing demonstrates that the use of AM to create PVs, when paired with specific plating techniques, can result in structures with significant strength capabilities at lighter than normal PV weights.

Furthermore, JHU/APL has begun to test the AM PVs in a number of research projects. Such testing is desired because these unique parts can be easily manufactured in shapes and volumes that were previously unattainable through common manufacturing techniques. AM parts are now commonly used in air-frames; however, in higher pressure underwater scenarios AM’s capabilities are unproven. JHU/APL has begun to apply this new and emergent field to the effective design of AM PVs, which can play a significant role in the field of underwater vehicles and similar projects.
Fatigue Crack Growth Behavior of Autofrettaged Hydrogen Pressure Vessel Made of Low Alloy Steel
Authors: Wada Yoru , Yanagisawa Yusuke
Published: October 2017

Autofrettage is used to known as an effective method to prevent fatigue crack propagation of thick-walled cylinder vessels operating under high pressure. Since low-alloy steel shows an enhanced crack growth rate in high-pressure gaseous hydrogen, this paper aims to validate the effect of autofrettage on crack growth behavior in high-pressure gaseous hydrogen utilizing 4%NiCrMoV steel (SA723 Gr3 Class2). An autofrettaged cylindrical specimen with a 70mm inside diameter and 111mm outside diameter was prepared with an axial EDM (depth of 1mm) notched on the inside surface. The measured residual stress profile coincides well with the calculated results. The fatigue crack growth test was conducted by pressurizing the cylinder and varying the external water pressure. Crack propagation from the EDM notch was observed in the non-autofrettaged cylindrical specimen while no crack propagation was observed when the initial EDM notch size was within the compressive residual stress field. When the initial EDM notch size was increased, the fatigue crack growth showed a narrow, groove-like fracture surface for the autofrettaged specimen. In order to qualitatively analyze those results, fatigue crack growth rates were examined under various load ratios including a negative load ratio using a fracture mechanics specimen. From the information obtained, crack growth analysis of an autofrettaged cylinder in a high-pressure hydrogen environment was successfully demonstrated with a fracture mechanics approach.
Guideline on Probabilistic Fracture Mechanics Analysis for Japanese Reactor Pressure Vessels
Authors: Katsuyama Jinya , Osakabe Kazuya , Uno Shumpei , Li Yinsheng , Yoshimura Shinobu
Published: October 2017

In Japan, to prevent nil-ductile fracture of reactor pressure vessels (RPVs) due to neutron irradiation embrittlement, deterministic fracture mechanics evaluation in accordance with the standards developed by the Japan Electric Association is performed for assessing the structural integrity of RPVs under pressurized thermal shock (PTS) events considering neutron irradiation embrittlement. In recent years, a structural integrity assessment methodology based on probabilistic fracture mechanics (PFM) has been introduced into the regulations in the United States and a few European countries. PFM is a rational methodology for evaluating the failure frequency of important pressure boundary components by considering the statistical distributions of various influence factors related to ageing due to the long-term operation. At Japan Atomic Energy Agency (JAEA), a PFM analysis code called PASCAL has been developed to evaluate the failure frequency of RPVs considering neutron irradiation embrittlement and PTS events. In addition, JAEA has developed a guideline for the PFM based structural integrity assessment of RPVs to promote the applicability of PFM in Japan and achieve the objective that an engineer/analyst who familiar with the fracture mechanics to perform PFM analyses and evaluate through-wall cracking frequency (TWCF) of RPVs easily. The guideline consists of a main body (general requirements), explanation (guidance), and several supplements. The technical basis for PFM analysis is also provided, and the new information and better fracture mechanics models are included in the guideline. In this paper, an overview of the guideline and some typical analysis results obtained based on the guideline and the Japanese database related to PTS evaluation are presented.
Electromagnetic Acoustic Transducer (EMAT) Development for Nondestructive Inspection of Spent Nuclear Fuel Storage Canisters
Authors: Cho H. , Choi S. , Lissenden C. J. , Lindsey M. S.
Published: October 2017

Stress corrosion cracking (SCC) is a potential degradation mode that could undermine the long-term integrity of stainless steel canisters for spent nuclear fuel storage. Due to limited accessibility and harsh environments, ultrasonic nondestructive inspection for the canisters demands robot deliverable and environmentally tolerant transducers. Development of electromagnetic acoustic transducers (EMATs) for remote ultrasonic guided wave SCC inspection of stainless steel canisters is described. These noncontact EMATs use transduction based on the Lorentz force. Among the infinite possibilities of guided wave modes and frequencies to select from, shear horizontal (SH) waves are chosen due to their favorable sensitivity to cracks oriented both parallel and perpendicular to the wave vector. The EMAT components (i.e., magnets, electrical coils, connectors, casing, and cables) are carefully selected and tested under high temperature and gamma radiation dosage. The performance of the constructed compact EMATs is evaluated by experiments on a 304 stainless steel plate containing machined notches. Specifically, the distances from which the EMATs can detect surface-breaking defects of minimal size are determined.
On-Line Condition Monitoring of Friction Stir Spot Welding Tool Using Vibration Measurements
Authors: Al-Badour Fadi , Mahgoub Ahmed , Bazoune Abdelaziz , Shuaib Abdelrahman , Merah Necar
Published: October 2017

Friction stir welding and spot welding (FSW/FSSW) tool condition plays a vital role on joint quality and successful completion of welding process. Detecting FSW tool pin cracking or fracture during welding is not possible by visual monitoring of the weld, as the tool pin is submerged in the butted or lapped joints. Even if the pin is fractured, the tool shoulder can still process the surface of the workpiece, giving false indication about the progress of the weld. Monitoring systems that can detect the condition of the tool can help operators or automated FSW machines in taking corrective actions to avoid continuation of the welding process with a damaged pin. These systems can also alert the operators to the necessity of replacing the tool. Researchers in the past have developed several methodologies in monitoring manufacturing processes (e.g. machining) utilizing force, temperature measurements, acoustic emission and vibration monitoring. Vibration is directly related to a machine’s structural dynamics and its working health conditions giving it an advantage over other techniques in detecting structural related problems such as cracking.
Simulation of the Interaction Between a Slender Flexible Cylinder and an Axial High-Speed Air Flow
Authors: Degroote Joris , Hertens Ine , Osman Akil , Vierendeels Jan
Published: October 2017

This research analyzes the interaction between fibers and the air jets that are used to accelerate them in fiber processing industries. Typically, supersonic flow is used to achieve sufficiently high thread speeds. However, this flow contains shocks and expansions, resulting in large longitudinal variations in force on the thin and flexible thread. Consequently, a complex fluid-structure interaction (FSI) occurs between the supersonic air flow and the thread.

In this research, the fluid-structure interaction between a supersonic air flow and a thread is studied numerically using three-dimensional simulations. The thread is represented by a smooth and flexible cylindrical body. The displacement of the thread is calculated for a given traction on its surface using a finite element structural dynamics code. The compressible flow around the thread is calculated using a finite volume computational fluid dynamics (CFD) code, using the arbitrary Lagrangian-Eulerian (ALE) framework to account for the thread deformation.

In these partitioned simulations, the kinematic and dynamic equilibrium conditions on the fluid-structure interface are satisfied using a coupling algorithm. Two coupling algorithms are compared and the influence of numerical parameters is investigated. The fluid-structure interaction simulations reveal transversal running waves in the thread. By comparing the speed of these waves with the propagation speed of the shock waves in the tube, it can be concluded that these phenomena are not related.
Nozzle Load Considerations and Misconceptions Introduced by Piping Support Friction
Authors: Antaal Bikramjit Singh , Williams Dennis K.
Published: October 2017

This paper discusses the prescribed requirements contained within the various ASME B31 Piping Codes and ASME B&PV Code, Section III that specifically address the need to recognize the restraint introduced by piping support friction. In addition, the requirement for the design of sliding supports (pipe shoes) and brackets to resist the forces due to friction in addition to the loads induced by bearing is also reviewed and discussed. As part of the required piping analysis, the questions surrounding the inclusion of the maximum coefficients of static friction and the impact of these often excessively large values on equipment nozzle loadings is reviewed in considerable detail, especially in light of the qualitative guidelines contained within WRC Bulletin 449. Included in the discussions of the considerations associated with the assumed restraint provided by support friction is the mathematical treatment of extrema (i.e., maxima and minima) with respect to calculated nozzle loads based upon the analyst’s choice of the largest published coefficients of static friction. Example problems taken from the authors’ decades of experience in the field are reviewed in light of the time dependent heat up and cooldown rates for the piping systems discussed herein. In most cases, the analyses show that not only is it highly improbable that the choice of only maximum values of coefficients of friction at each support will exist, but rather it is impossible that this often abusive practice by the unsuspecting analyst for the “worst case” frictional coefficients to exist simultaneously in a piping installation. Finally, recommendations for the considerations of the potential restraint induced by piping support friction in the rigorous piping analyses are tendered.
Advantages of Air Blow Cleaning of Steam Pipes for Cost and Schedule Savings
Authors: Jarvis Julie M. , Brenner Matthew J. , Hall Michael I. , Babel Paul J.
Published: October 2017

The use of steam as the fluid to clean steam lines in large commercial steam power plants is the most common and widely used method in the industry. The advantages of using air as the cleaning fluid can be significant and have positive impacts on both overall costs and schedule. While the general methodology for analyzing the air blow cleaning of process piping is very similar to steam blow cleaning, there are some additional computations and considerations needed.