bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatigue Performance of Austenitic Stainless Steel: Enforced Endurance Limit and Questionable Design Curve
Authors: Solin Jussi , Seppänen Tommi , Mayinger Wolfgang
Published: December 2020

Design codes and standards are used for new designs and also for management of operation and in service inspection of existing NPP primary circuit pressure boundaries. The current codes — ASME, KTA, RCC-M, PNAE-G and JSME — have been originally rooted to the ASME Boiler and Pressure Vessel Code, Section III, Nuclear Vessels, which was published in 1963. Article 4, N-415 “Analysis for cyclic operation” instructed calculation of stress intensities for fatigue transients and provided two design curves for basic material types — one for ferritic, the other for austenitic steels.

The design curves were based on strain-controlled LCF tests, which measured the allowable numbers of cycles as function of plastic strain. The obtained material performance was then processed to strain-life and design curves (Sa = Ex εa). This local strain fatigue approach was found applicable for both ferritic and austenitic steels though their elastic plastic cyclic responses are much different. Fatigue data for stainless steels extended to ¼ million cycles and the design curve was extrapolated to one million cycles. Later on — supported by load-controlled HCF tests — the original LCF approach has been extended even beyond HCF to VHCF regime.

Our strain-controlled HCF results for alloy types 347 and 304L are in conflict with the reference mean curve behind current ASME curve for stainless steels. We assume that this reflects a generic issue related to extrapolation of the LCF methodology by Coffin, Langer and other pioneers. Furthermore, analysis of cyclic responses and variable amplitude testing to millions of cycles give reasons to assume that the concept of an endurance limit (Se) is applicable also for variable amplitude straining. Variable amplitude HCF straining was not studied for ferritic steels and we propose the concept of enforced endurance limit to austenitic stainless steels only.

We propose a critical review on relevance of the current ASME III design curve for stainless steels.
Residual-Stress, Material Characterization in P22 HRSG-Pipeline Butt Joint
Authors: Grisolia Ottaviano , Scano Lorenzo , Piccini Francesco , Lo Conte Antonietta , De Agostinis Massimiliano , Fini Stefano
Published: December 2020

Previous study evaluated residual stress in a circumferential “V”-groove butt joint of a heat-recovery steam generator (HRSG) pipeline; the material was ASTM A-335-Grade P22. Aim had been to check on the influence over creep-relaxation previously found out for a tee made of the same material. The butt joint had been operating for the same period of 200,000 hours, same temperature of 528°C at almost a half pressure (0.46 Kg/mm2 vs. 1.06 Kg/mm2). X-ray diffraction (XRD) technique applied close to the weld highlighted anomalously high stress-level on the outer surface for all four butt-joint samples tested. Residual-stress over 400 MPa observed along the cylinder’s tangential direction was statically not acceptable. On the inner surface where deposited beads may have tempered adjacent base material, measurement via blind hole-drilling (BHD) technique showed a symmetrical plane-state residual-stress of 199 MPa. It was consistent with that observed via XRD on the outer surface in the cylinder’s longitudinal direction. Supposing a case of incomplete post heating planned for the weld may have explained the occurrence of being much higher than 40 MPa, value predicted after 200,000 hours. Similar influence over creep results found out for the tee and the butt joint had validated modeling welding simulation considered for both joints. A comprehensive new series of XRD tests aims now at measuring residual stress across the cylinder’s wall, both inner and outer sides. The shallow layer considered has thickness sufficient for building a map of measurements covering different depths and locations on the surface. The experimental plan includes also BHD tests supporting the XRD ones. Comparison with previous measurements roughly shows stress level increasing similarly across the cylinder’s wall from the inner side on: Average stress values, however, appear lower than previous measurements, showing better compatibility to the analysis results.
Predicting Pipe Rupture Frequencies Using xLPR
Authors: Rudland David L.
Published: December 2020

Over the last several years, the U.S. Nuclear Regulatory Commission (NRC), in cooperation with the Electric Power Research Institute (EPRI), conducted a multi-year project that focused on the development of a viable method and approach to address the effects of primary water stress corrosion cracking (PWSCC) in primary piping systems approved for leak-before-break (LBB). This project, called eXtremely Low Probability of Rupture (xLPR), defined the requirements necessary for a modular-based probabilistic fracture mechanics assessment tool to directly assess compliance with the regulations. Version 2.0 of this code has been completed and is currently awaiting public release.

Since the focus of xLPR Version 2.0 is investigating the impacts of active piping degradation on the leak-before-break behavior of reactor coolant piping, questions have been raised to whether xLPR can be used to confirm pipe rupture frequencies developed in other efforts, such as NUREG-1829, “Estimating Loss-of-Coolant Accident (LOCA) Frequencies Through the Elicitation Process.” This paper discusses an initial study focused on whether xLPR can be used to estimate pipe rupture frequencies.

A series of analyses were conducted, based on inputs developed by the xLPR program team, focused on the reactor pressure vessel outlet nozzle geometry of a typical pressurized water reactor. Additional analyses were conducted using the same radius-to-thickness ratio but decreasing the pipe diameter. Due to computer memory restrictions, it was difficult calculating low probability events when considering PWSCC initiation, typical residual stresses, leak detection and in-service inspection. Therefore, to bound the problem, an aggressive weld residual stress was assumed with multiple pre-existing defects. By modifying the size and number of these initial defects, results were generated that indicated the conditional probability of rupture was related to the percentage of the inner circumference cracked and the pipe diameter.

Using the PWSCC initiation model from xLPR Version 2, the yearly rupture frequency with leak detection and in-service inspection was calculated. The results indicate that the rupture frequencies in NUREG-1829 appear conservative relative to the results from this study.

Due to the limited scope of this study, the assumptions used in these analyses were limited or conservative; therefore, additional analyses are needed for a more robust comparison. However, the results suggest that conducting xLPR analyses with pre-existing defects may be useful in bounding LBB applicability with active degradation.
Introduction of the Technical Document in Japan for Safety Use of Type2 Pressure Vessels in Hydrogen Refueling Stations
Authors: Sato Shinya , Kobayashi Hiroshi , Fukimoto Hajime , Maeda Shigeru , Yoshikawa Nobuhiro , Arashima Hironobu
Published: December 2020

We considered the Type2 pressure vessel (hereinafter, Type2) used in hydrogen refueling stations (hereinafter, HRS), a stational Composite Reinforced Pressure Vessel (hereinafter, CRPV) in which a metal layer made of high-strength low-alloy steel is wrapped with a carbon fiber reinforced plastic (hereinafter, CFRP) layer in the circumferential direction. Because Type2 is lightweight and has a long life, installation in HRS is expected. However, since no technical standards concerning design for safe use of Type2 for HRS currently exist, few Type2 have been installed in HRS in Japan.

Based on these circumstances, we are developing a Technical Document on the safe use of Type2 (hereinafter, TD) to promote the installation of Type2 at HRS.

In this paper, we introduce the current discussion on issuance of the TD as an industrial standard, focusing especially on the following: Type2 shall be considered a two-layer pressure vessel in which the CFRP layer shares the circumferential stress of the metal layer. The wall thicknesses of the metal layer and CFRP layer of Type2 are calculated by Design by Rule approach, but when necessary, Design by Analysis (stress analysis and fatigue analysis) can be applied. Design specification tests such as the burst test and hydraulic pressure cycle test using an actual Type2 should not be required. The hydrogen compatibility and fatigue life of the low-alloy steel used in the metal layer are evaluated in accordance with our previously-proposed methods [1]. In the fatigue analysis, the effect of autofrettage can be considered.
Study on Numerical Simulation of Gas-Solid Erosion for Horizontal Feed Pipe
Authors: Hu Weiwei , Hu Lichen , Sun Li , Shen Chengye , Chen Hu
Published: December 2020

The gas-solid two phase flow was formed in the catalyst conveying pipeline with the catalyst particles coming from the top of the inclined pipes and air blowing from one side of the horizontal feed pipe. The upper side of horizontal pipe was seriously eroded. The erosion situation of feed pipe was simulated by the Discrete Phase Model (DPM) in Fluent software. The simulation result was compared with the field pipeline, and the gullies on the upper side of the horizontal pipe were formed by the particles concentrating on the upper side of the horizontal pipe with the excessive gas phase velocity. The reasonable distribution method of velocity was put forward by grouping numerical simulation of different particle velocities and blowing velocities. The particles were remained in the intermediate position of the horizontal pipe to reduce the collision between particles and the pipe wall. Therefore, the erosion rate of the pipe was slowed down; in addition, the service life of pipeline was prolonged. The research results of this paper could be used to provide reasonable feed speed for the actual petrochemical feed pipe. The protection methods was put forward for the horizontal feed pipe. The safety of petrochemical enterprises were guaranteed.
Post-Irradiation Evaluation of Eurofer97 Fracture Toughness Using Miniature Multinotch Bend Bar Specimens
Authors: Chen Xiang , Clowers Logan A. , Graening Tim , Bhattacharya Arunodaya , Campbell Anne A. , Robertson Janet , Geringer Josina W. , Sokolov Mikhail A. , Katoh Yutai , Rieth Michael
Published: December 2020

In this study, we performed fracture toughness characterization of ten neutron-irradiated Eurofer97 variants using precracked miniature multi-notch bend bar (M4CVN) specimens based on the Master Curve method in the ASTM E1921 standard. The neutron irradiation was performed in the flux trap position of the High Flux Isotope Reactor (HFIR) of the Oak Ridge National Laboratory (ORNL) with the nominal irradiation temperature of 300°C and irradiation dose of 2.5 displacements per atom (dpa). Depending on the irradiation temperature and materials, we observed different degrees of irradiation hardening and embrittlement for ten Eurofer97 variants. The upper shift in the Master Curve reference temperature T0Q vs. the increase in Vickers microhardness values showed a liner relationship for only a few materials indicating different irradiation responses of the Eurofer97 variants.
Current Situation and Prospect of Underground Gas Storage Well
Authors: Shi Kun , Duan Zhixiang
Published: December 2020

Gas storage well (GSW) is a sort of pressure vessel and a typical model of underground pressure vessel. Now the media of GSW is mainly compressed natural gas (CNG). The main advantages of GSW are analyzed, such as safety and economy are discussed. The current application field and the potential application field of GSW are also explained. Since the idea of GSW originated from oil-gas engineering, GSW has the absolute merit as well as connatural deficiency comparing to the conventional pressure vessel. The problems on material, design, manufacture, inspection, etc. of GSW based on current situation are discussed, forward analysis and expectation for its prospect are brought.

With the idea of GSW, some special type underground pressure vessel appeared, such as the underground cylinder type pressure vessel. The structure, design, manufacture of the underground cylinder type pressure vessel is discussed. With the development of new energy, the application field of the GSW is gradually expanded. The hydrogen storage GSW (HGSW) comes into being. The advantage such as safety and economy of HGSW, and the disadvantage are also analyzed. The key questions for the HGSW used in the hydrogenation fueling station are also summarized. The solution for material-hydrogen compatibility and tightness of high pressure HGSW is discussed finally.
A Historical Overview of Design Analyses and Experimental Observations of Ratcheting Phenomenon
Authors: Macedo Jean , Chapuliot Stéphane , Bergheau Jean-Michel , Feulvarch Eric , Ancelet Olivier , Martin Antoine
Published: December 2020

In order to investigate the ratcheting behavior and to determine new design rules, some experimental tests were conducted in many countries in the last decades. In France, some tests were carried out under mechanical or thermal cyclic loading to examine this risk. The first section of the current article is addressed to the state of the art concerning the ratcheting effects. The difference between Local and Global Ratcheting is clarified. The second section is dedicated to the experimental observations of ratcheting. The following section describes the constitutive models which are able to simulate material/structural ratcheting responses. The models presented are Linear Kinematic, Armstrong-Frederick, Chaboche, Ohno-Wang and Chen-Jiao-Kim. Finally, the ratcheting rules in design codes are exposed. Both simple and complex rules are presented.
Comparative Study on Different National Standards for Local Post Weld Heat Treatment of Pressure Vessels
Authors: Ji Fang , Deng Guide , Duan Linlin , Liu Cenfan , Zhao Xiaonan
Published: December 2020

In order to eliminate these welding residual stress which produced in the process of pressure vessel manufacturing and assembling, post-weld heat treatment is required for the weld structure. The Large size and complex structure pressure vessel which cannot integral post-welding heat treatment always implement local post-welding heat treatment. The reasonable heated band and insulated band are particularly important in the procedures of local post-welding heat treatment to meet the requirements of pressure vessel heat treatment. The recommended heated band and insulated band are given in different national standards. But the recommended width of heated band and insulated band are different in different national standards. In the paper, numerical simulation was carried out to compare and study the difference of temperature distribution in the holding temperature period when post-welding heat treatment of pressure vessel barrel butt weld. The result show that the temperature distribution on sock band is very closed when the barrel butt weld implements post weld heat treatment with the heated and insulated band recommended in ASME BPVC-VIII-2017 and EN 13445-4:2014. The axial temperature gradient on sock band is very small and the temperature difference almost comes from the temperature difference through the thickness. Compared with this, the axial temperature gradient is larger and the temperature difference through thickness is smaller when post weld heat treatment with the max recommended heated and insulated band given in GB/T 30583-2014.
Assessment of Flaw Interaction Under Combined Tensile and Bending Stresses: Suitability of ASME Code Case N877-1
Authors: Dulieu Pierre , Lacroix Valéry , Hasegawa Kunio
Published: December 2020

In the case of planar flaws detected in pressure components, flaw characterization plays a major role in the flaw acceptability assessment. When the detected flaws are in close proximity, proximity rules given in the Fitness-for-Service (FFS) Codes require to combine the interacting flaws into a single flaw. ASME Code Case N877-1 provides alternative proximity rules for multiple radially oriented planar flaws. These rules are applicable for large thickness components and account for the influence of flaw aspect ratio. They cover the interaction between surface flaws, between subsurface flaws and between a surface flaw and a subsurface flaw. The calculations of flaw interaction have been performed under pure membrane stress. However, actual loading conditions induce non-uniform stresses in the component thickness direction, such as thermal bending or welding residual stresses. Non-uniform stress fields can lead to variations in the Stress Intensity Factors of closely spaced flaws, affecting their mutual interaction. The objective of this paper is to assess the suitability of ASME Code Case N877-1 with regards to the presence of a bending part in the applied stress distribution. For that purpose, various applied stress profiles and flaw configurations are covered. The effect on flaw interaction is assessed through three-dimensional XFEM analyses.
A High Temperature Primary Load Design Method Based on Elastic Perfectly-Plastic and Simplified Inelastic Analysis
Authors: Messner M. C. , Jetter R. I. , Sham T.-L.
Published: December 2020

The current primary load design provisions of Section III, Division 5 of the ASME Boiler and Pressure Vessel Code, covering high temperature nuclear components, represent an allowable stress methodology using elastic analysis and stress classification procedures to approximate stress redistribution caused by creep and plasticity. This process is difficult to implement and automate in modern finite element frameworks. This paper describes an alternate primary load design approach that uses elastic perfectly-plastic analysis in conjunction with the reference stress concept to eliminate stress classification while retaining a link to the existing Section III, Division 5 allowable stresses. This global, structural allowable stress check is supplemented with a local check to guard against the initiation of creep damage at local stress discontinuities like headers, nozzles, and other stress concentrations. This check is based on a simple elastic-creep analysis with creep damage calculated with the time-fraction approach, using the current ASME minimum-stress-to-rupture values already provided in the current Code. Both the global and local checks are easily implemented in modern finite element analysis software and greatly simplify Section III, Division 5 primary load design when compared to the current design-by-elastic-analysis method. Several examples demonstrate the utility of the new approach and its potential to reduce over-conservatism.
Investigating the Correlation Between Different Effective Stress Measures and the Service Life of Actual High-Temperature Structural Components
Authors: Rovinelli Andrea , Messner Mark C. , Sham T.-L.
Published: December 2020

Effective stress measures are utilized by engineers to correlate uniaxial and biaxial experimental rupture data to creep failure in real components. Different effective stress formulations are used in various high temperature design codes, such as the Section III Division 5 of the ASME Boiler and Pressure Vessel code and the French RCC-MRx, and in different fitness for service provisions, such as the British R5 and the American FFS-1. Under uniaxial and biaxial stress states all the investigate metrics predict similar rupture times and provide similar safety margins, however there is no guarantee that when these metrics are extrapolated to predict the creep life for triaxial state they will remain conservative. In this work we use the real geometry of a Grade 91 end-plate that failed prematurely and finite element simulations to investigate the variability in creep life predictions obtained utilizing different effective stress as creep-damage driving force. Results show that for triaxial stress states the time to crack nucleation, the crack initiation site and the crack path are extremely sensitive to the effective stress measure.
Selection Criteria for Clad Materials to Use With a 316H Base Material for High Temperature Nuclear Reactor Cladded Components
Authors: Barua B. , Messner M. C. , Jetter R. I. , Sham T.-L.
Published: December 2020

The clad selection criteria proposed in this work supports a design approach provided in [PVP2020-21469] for cladded component for high temperature nuclear service. The proposed design method guards the clad material against the creep-fatigue failure and ratcheting strain accumulation in elevated temperature nuclear service without the requirement of long-term material properties. However, it limits the type of clad materials that can be used with the existing Class A materials qualified for ASME Section III, Division 5 rules. The analysis approach and design rules allow the use of two types of clad materials — soft clads that creep much faster than the base material and hard clads that creep much slower and have higher yield stress than the base material. This work proposes selection criteria for such soft and hard clad materials to use with a Class A metallic alloy — austenitic steel 316H. The criteria are developed based on the effect of relative elastic modulus and creep rate on the long term stress redistribution between the 316H base and the clad material. The proposed clad selection criteria are applicable up to a design temperature of 750°C and for 1% to 10% thick cladding. The selection criteria are evaluated on two materials — nickel and a molybdenum based alloy TZM — categorizing them as soft or hard clad for 316H base material.
Codes, Standards, Rules and Assumptions on Environment Assisted Fatigue for Fatigue Management of Primary Piping
Authors: Solin Jussi , Seppänen Tommi , Vanninen Rami , Pulkkinen Erkki , Lemettinen Petri , Faidy Claude
Published: December 2020

All international codes used for design, operation and inspection of NPP primary circuit pressure boundaries are rooted to the ASME Boiler and Pressure Vessel Code, Section III, Nuclear Vessels, 1963. Article 4, N-415 “Analysis for cyclic operation” instructed calculation of stress intensities for fatigue transients and provided two design curves for basic material types. Different codes such as ASME, RCC-M, KTA, PNAE and JSME have much in common, but partial deviations exist.

In 2007 the US NRC Regulatory Guide 1.207 endorsed a methodology for accounting the environmental effects. It was mainly based on extensive work in Japan and the Argonne National Laboratory. The final report of ANL, NUREG/CR-6909 became a major reference and subject of criticism. However, the first approach for environment assisted fatigue (EAF) written in ‘code language’ was published in Japan and a regulatory requirement for consideration of EAF both for operating reactors and new designs appeared first in Finland.

This paper discusses challenges in management of fatigue and the evolving state-of-the-art in different codes, standards, rules and assumptions. The roots and current status of fatigue curves and design criteria applied in Finnish NPP’s are explained.
Evaluation of Mean Stress Correction on Fatigue Curves of Grade 91 and Alloy 617 in ASME Section III Division 5
Authors: Wang Y. , McMurtrey M. D. , Jetter R. I. , Sham T.-L.
Published: December 2020

The current ASME Boiler and Pressure Vessel (B&PV) Code Section III, Division 5, Subsection HB, Subpart B has only one design fatigue curve for grade 91 steel (Gr. 91) at 540 °C (or 1000 °F). The ASME Section III Working Group on Creep-Fatigue and Negligible Creep (WG-CFNC) has taken an action to incorporate the temperature-dependent design fatigue curves for Gr. 91 developed by Japan Society of Mechanical Engineers (JSME) into ASME Section III Division 5. During the process, issues regarding the effect of mean stress on fatigue analysis, and how to consider the mean stress effect for elevated-temperature design, were brought up. To evaluate whether the design fatigue curves of Gr. 91 needed adjustment to account for mean stress, critical tests were designed and performed at 371 °C (700 °F) and 540 °C (1000 °F). This study is similar to the work performed on Alloy 617 when its fatigue design curves were established for temperature range of 538–704°C (1000–1300°F) as part of the Code Case package for Alloy 617 to be used as Class A construction material in Division 5. The effects of mean stress on Alloy 617 were evaluated at 550°C (1022°F). The results showed that the mean stresses introduced by the non-zero mean strain could not be maintained under strain-controlled fatigue and resulted in negligible effect on the fatigue life. Mean stress correction was not recommended for Alloy 617 fatigue design curves in Division 5. This study shows the same conclusion for Gr. 91.
The Impact of Geometric Discontinuities on Alloy 617 Creep-Rupture Behavior
Authors: Rupp Ryann E. , McMurtrey Michael D.
Published: December 2020

The Nuclear Regulatory Commission (NRC) is currently reviewing Section III, Division 5 of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code for potential endorsement. A prior NRC-sponsored review on the application of Section III, Division 5 design rules for elevated-temperature reactors have identified issues currently not in the code that need to be addressed. These include an insufficient knowledge of the effect of notches, structural discontinuities, and multiaxial stress. This work qualitatively evaluates Alloy 617 as notch strengthening or notch weakening and investigates the impact of multiaxial stress on Alloy 617 creep behavior.

Multiaxial stress does not degrade Alloy 617’s short-term creep-rupture properties. This was concluded from the following observations: 1) multiaxial creep resided on or to the right of the Larson-Miller curve for uniaxial creep-rupture data, 2) Alloy 617 exhibited notch strengthening, and 3) creep-rupture life increased with a stronger multiaxial stress. Long-term and intermediate creep-rupture tests are in progress in order to determine whether notch behavior will cross from strengthening to weakening at lower stresses and longer rupture lifetimes. A nondestructive characterization methodology using X-ray computed tomography is explored as a means to identify the failure location on the specimen prior to rupture.
Background on Low Temperature Overpressure Protection System Setpoints for Pressure-Temperature Curves
Authors: Poehler Jeffrey C. , Stevens Gary L. , Udyawar Anees A. , Freed Amy
Published: December 2020

ASME Code, Section XI, Nonmandatory Appendix G (ASME-G) provides a methodology for determining pressure and temperature (P-T) limits to prevent non-ductile failure of nuclear reactor pressure vessels (RPVs).

Low-Temperature Overpressure Protection (LTOP) refers to systems in nuclear power plants that are designed to prevent inadvertent challenges to the established P-T limits due to operational events such as unexpected mass or temperature additions to the reactor coolant system (RCS). These systems were generally added to commercial nuclear power plants in the 1970s and 1980s to address regulatory concerns related to LTOP events. LTOP systems typically limit the allowable system pressure to below a certain value during plant operation below the LTOP system enabling temperature.

Major overpressurization of the RCS, if combined with a critical size crack, could result in a brittle failure of the RPV. Failure of the RPV could make it impossible to provide adequate coolant to the reactor core and result in a major core damage or core melt accident. This issue affected the design and operation of all pressurized water reactors (PWRs).

This paper provides a description of an investigation and technical evaluation regarding LTOP setpoints that was performed to review the basis of ASME-G, Paragraph G-2215, “Allowable Pressure,” which includes provisions to address pressure and temperature limitations in the development of P-T curves that incorporate LTOP limits. First, high-level summaries of the LTOP issue and its resolution are provided. LTOP was a significant issue for pressurized water reactors (PWRs) starting in the 1970s, and there are many reports available within the U.S. Nuclear Regulatory Commission’s (NRC’s) documentation system for this topic, including Information Notices, Generic Letters, and NUREGs. Second, a particular aspect of LTOP as related to ASME-G requirements for LTOP is discussed. Lastly, a basis is provided to update Appendix G-2215 to state that LTOP setpoints are based on isothermal (steady-state) conditions.

This paper was developed as part of a larger effort to document the technical bases behind ASME-G.
Technical Basis for Revision to ASME Section XI Appendix C for Stress Corrosion Crack Growth Rate Equations for Alloy 600 and Associated Welds
Authors: Jenks Amanda , Bamford Warren H.
Published: December 2020

Alloy 600 and its associated weld metals (Alloys 82, 182, and 132) have been used extensively for nuclear power plant construction. These alloys are known to be susceptible to primary water stress corrosion cracking (PWSCC), and reference crack growth rate (CGR) equations for this degradation mechanism were first incorporated into the ASME Boiler and Pressure Vessel Code in the 2009 Addenda of the 2007 Edition via Section XI, Nonmandatory Appendix C. These original equations were developed from a large dataset to which numerous international laboratories contributed. It was reviewed and assessed by an Expert Panel. In 2015, another Expert Panel was organized, including members from the original Expert Panel. Publicly available data produced since the first equations were developed, and data that had not been part of the original model development process, were collected. The data were screened for testing quality and plant applicability by the Expert Panel, and new PWSCC equations were developed. This paper summarizes the development of the revised PWSCC equations for Alloy 600 and Alloy 82/182/132 to support revision of the equations previously incorporated into Appendix C of ASME B&PV Code Section XI.
Analysis of HDPE Failure Data in Support of Development of Flaw Acceptance Criteria for Butt Fusion Joints
Authors: Liu Cheng , Scarth Douglas , Munson Douglas P. , Wolfe Ryan
Published: December 2020

There is a need for ASME B&PV Code procedures and acceptance criteria for evaluation of flaws detected by inspection of high density polyethylene (HDPE) piping items in safety Class 3 systems. To support the development of flaw acceptance criteria for butt fusion joints in HDPE pipes, a series of coupon tests have been completed for specimens cut from butt fused HDPE pipes with surface or subsurface flaws placed in the joints prior to fusion process. Specimens containing known flaw sizes were tested under axial load at accelerated stresses and temperatures until failure; or until a prescribed number of test hours was reached. The failure time from the tests has been correlated to the net section stress and the stress intensity factor, and the results showed that the failure time can be better represented by the stress intensity factor. The test results were then used to fit the Brown and Lu formula that predicts the time to failure due to the slow crack growth of flaws as a function of stress intensity factor and temperature. With the developed Brown and Lu equation, the allowable stress intensity factors for a piping lifetime of 50 years at the maximum code allowable temperature of 60°C have been proposed for both surface and subsurface flaws in HDPE butt fusion joints. Examples of what might be corresponding allowable flaw sizes in the butt fusion joints of piping are also provided.
Fatigue Consideration of Layered Vessels
Authors: Xu Kang , Rana Mahendra , Jawad Maan
Published: December 2020

Layered pressure vessels provide a cost-effective solution for high pressure gas storage. Several types of designs and constructions of layered pressure vessels are included in ASME BPV Section VIII Division 1, Division 2 and Division 3. Compared with conventional pressure vessels, there are two unique features in layered construction that may affect the structural integrity of the layered vessels especially in cyclic service: (1) Gaps may exist between the layers due to fabrication tolerances and an excessive gap height introduces additional stresses in the shell that need to be considered in design. The ASME Codes provide rules on the maximum permissible number and size of these gaps. The fatigue life of the vessel may be governed by the gap height due to the additional bending stress. The rules on gap height requirements have been updated recently in Section VIII Division 2. (2) ASME code rules require vent holes in the layers to detect leaks from inner shell and to prevent pressure buildup between the layers. The fatigue life may be limited by the presence of stress concentration at vent holes. This paper reviews the background of the recent code update and presents the technical basis of the fatigue design and maximum permissible gap height calculations. Discussions are made in design and fabrication to improve the fatigue life of layered pressure vessels in cyclic service.
Flooring impact sound: An overview of the new test standard, its application for healthcare design, and potential updates to the standard
Authors: Raley Michael
Published: December 2020

Noise is a major concern in many healthcare environments, and the “Quietness of Hospital Environment” item on the Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS) consistently receives one of the lowest scores. A recent study showed that among many acoustic metrics, peak occurrence rates were one of the best correlated with HCAHPS scores for Quietness of Hospital Environment. Flooring impact sound from footsteps, rolling carts, and dropped items can be a significant source of noise in hospitals, and that impact sound is likely to contribute to peak occurrence rates. Flooring-generated noise is often a concern for healthcare designers, and is a primary consideration when picking flooring materials, but until recently there has been no standard for assessing the floor impact sound radiation of various floor coverings. A new standard, ASTM E3133, provides this assessment. In this presentation, data from recent testing to the ASTM E3133 standard will be given for various floor coverings. Additionally, the presentation will cover issues with the test methodology and potential solutions. Finally, preliminary results from a proposed field test standard will be discussed.
Restorative effect of interactive virtual reality natural environment experience on psychophysiological responses
Authors: Jeon Jin Yong , Jo Hyun In , Lee Kounseok
Published: December 2020

In this study, the restorative effect of a natural environment experience simulated with interactive virtual reality technology on the psychophysiological response was investigated. Three simulated virtual reality stimuli were selected: a green-dominated area, green and water combined area, and water-dominated area. Free movement was permitted to provide interaction in virtual reality, and an appropriate sound environment was provided in real time to each space through 3-D sound technology. Fifty subjects experiencing the normal levels of stress or depression participated in this study. The aim was to locate the most restorative point in the natural environment, and the physical properties at each point were quantified. In addition, to collect psychological responses, subjects were asked to respond to a restoration questionnaire based on the attention restoration and stress reduction theory and a questionnaire on soundscape and landscape perception. Concurrently, various physiological responses, such as heart rate, electroencephalogram, and eye tracking, were measured. Finally, the relationship between physical characteristics and psychophysiological responses was investigated. Based on this, guidelines were presented on how to create a virtual reality natural environment for stress recovery.
Shear wave elastography for skeletal muscle diagnostics
Authors: Krit Timofey , Ivanova Arina , Kamalov Yuly
Published: December 2020

Shear modulus in the biceps of volunteers was measured with standard ultrasound equipment, the at loads from 0 to 50 N. The measurements were carried out by shear wave elastography in the clinic according to the medical protocol. The volunteer held a sport weight of known mass to load the bicep. Shear wave was excited in the muscle at a given depth by an ultrasonic sensor. The shear wave velocity was recorded in the specific point, which was determined by the position of the sensor. The shear modulus of the muscle fibers measured by elastography increases from 10 to 60 kPa with the increase of the load and returns to 10 kPa 1 min after load is removed. The maps of the shear modulus distribution were measured in the areas around the points of the shear velocity measurements. Research was funded by the grant from the Russian Science Foundation (Project No. 19-72-00086).
A noninvasive method to estimate tissue stress-strain relationships using quasi-static and shear wave ultrasound elastography
Authors: Wang Yuqi , Urban Matthew W.
Published: December 2020

Current clinically used ultrasound elastography is obtained when tissue undergoes small deformation (<2% strain). However, small deformation may not be large enough to characterize tissues that exhibit similar elasticity properties to normal tissue at small deformation but behave differently from normal tissue at large deformation (>10% strain). Therefore, tissue elasticity properties measured at large deformation may provide better diagnostic differentiation. Combining the quasi-static and shear wave ultrasound elastography methods, we propose a noninvasive method to estimate the nonlinear elasticity property of tissue. To test this method, cubic tissue-mimicking phantoms were constructed. We progressively compressed the phantom to produce a series of stepwise stress states. At every stress state, we conducted shear wave measurements in which two acoustic radiation force pushes generated shear waves, which were measured using ultrafast imaging in order to estimate the local shear modulus. For every compression step, we tracked incremental tissue displacements between two successive frames and then accumulated these displacements for all steps to obtain the cumulative displacements and strains. Using the shear modulus and cumulative strain images we calculated the stress map under an incompressibility assumption. Finally, we obtained the local stress-strain curve that reflected the nonlinear elasticity of the tested material.
Spectrally resolved passive acoustic imaging
Authors: Arvanitis Costas
Published: December 2020

Ultrasound in combination with circulating microbubble contrast agents has emerged as a promising modality for therapy and imaging of brain diseases. Despite progress, the need for spatio-temporal mapping and control of the cerebrovascular microbubble dynamics necessitates the development of fast and spectrally resolved trans-skull imaging methods. In this talk, we will present our recent efforts towards establishing such methods. First, we will introduce a general methodology using the angular spectrum (AS) approach in a heterogeneous medium, which is based on a numerical marching scheme to approximate the full implicit solution, and reveal its functionality for trans-skull passive acoustic imaging (70% source localization error reduction from 2.89 ± 1.76 mm to 0.68 ± 52 mm). Then, we will demonstrate the ability of AS in combination with a nonlinear state controller that uses specific frequency bands of the microbubble acoustic emissions (harmonic, ultra-harmonic, etc.) to attain stable cavitation activity for tens of seconds. Finally, we will present our progress towards adapting the AS method for rapid visualization of vessel structures with diameters of a few hundreds of microns. The superior image quality and computation efficiency (>100-fold faster from time-domain delay-and-sum methods) of AS offers unique opportunities for spectrally resolved passive acoustic imaging and image guided therapy of human disease.
Guided wave inversion for arterial stiffness
Authors: Roy Tuhin , Urban Matthew W. , Greenleaf James , Guddati Murthy
Published: December 2020

Shear Wave Elastography (SWE) has been used to estimate arterial stiffness, an important biomarker for early cardiovascular diseases. In arterial SWE, the carotid artery is excited with acoustic radiation force and the observed wave propagation characteristics are used to estimate the arterial stiffness. We present an efficient guided wave inversion procedure, where the elastic modulus of the arterial wall is estimated by matching wave dispersion from experiments and simulation. Central to the proposed approach is an efficient forward model that computes the dispersion relation for the incompressible, immersed cylindrical tube; the model achieves high efficiency by combining semi-analytical finite element methods, selective reduced integration, and perfectly matched discrete layers. We utilize this forward model in an optimization framework to develop a streamlined methodology to estimate the modulus of the arterial wall. In this talk, we present the formulation of the method as well as validation using phantom experiments on 10 rubber tubes (VytaFlex-10), followed by preliminary work on inverting for the viscoelastic modulus.
Perfectly matched discrete layers for modeling unbounded domains
Authors: Guddati Murthy
Published: December 2020

The method of perfectly matched layers (PML) is based on the elegant idea of introducing attenuation while keeping impedance unaltered, thus resulting in effective absorption of waves without spurious reflections. Due to its simplicity and effectiveness, PML has been widely used over the past 25 years to model wave propagation in unbounded domains. However, an acknowledged challenge is that PML no longer preserves impedance once the domain and the PML region are discretized, leading to spurious reflection at the interface. This issue has been fixed with the help of so-called impedance preserving discretization, leading to the method of perfectly matched discrete layers (PMDL), developed more than a decade ago. The idea is based on the observation that midpoint integration completely eliminates the discretization error in impedance that arises from linear finite element discretization. Beyond eliminating reflections at the interface, impedance preserving discretization is shown to be crucial to achieving stability of absorbing boundary conditions in situations with differing signs of phase and group velocities, e.g., anisotropic media. This talk will be an exposition of the development of the PMDL by the author and his collaborators, staring with fundamental ideas impedance preserving discretization followed by more advanced ABCs for anisotropic and periodic media.
On an efficiency improvement of the sound fire extinguisher by the electro-magnet speaker
Authors: Kim Bong-young , Bae Myungjin
Published: December 2020

The Sound Fire Extinguisher is a device that suppresses flames by outputting loud sounds. In order for the sound fire extinguisher to be used in the fire fighting field, it must be compact and lightweight. In this paper, the electro-magnets were used instead of the permanent-magnets of speakers to maximize the output while minimizing the increase in the weight and volume size. A general dynamic speaker uses a permanent-magnet to generate power to the voice coil. The method applied in this study increased the magnetic flux acting on the voice coil by applying electro-magnet instead of permanent-magnet. An experiment was conducted to compare the output efficiency of the speaker with the permanent-magnet applied and the speaker modified with the electro-magnet. As a result of the comparative measurement through the experiment, the existing permanent-magnet applied speaker outputs 150 W at 1.5 kg, while the speaker applied by changing to electro-magnet outputs 500 W at 2 kg. In order to increase the output of the speaker, the weight is increased by 33% but the output is increased by 233% by applying electro-magnet instead of permanent-magnet. This enabled the Sound Fire Extinguisher to achieve high power, miniaturization and light weight.
On analysis of factors for retaliation psychology of the Klaxon sound
Authors: Tian Zhixing , bae myungjin
Published: December 2020

The number of cars is increasing, the road environment is more complicated, the traffic is congested, and klaxon sound is used more. At this time, driving retaliation caused by klaxon sound has become a serious social problem. Therefore, it is necessary to develop a new rhythm Klaxon sound that does not cause psychological stress and retaliation. In this paper, we developed the optimal rhythm Klaxon sound by finding the cause of stress, retaliation, and noise in acoustic and psychological aspects through comparison of existing Klaxon sound and rhythm sound. Retaliation in the brain waves of listeners was shown to be delta wave and beta wave, respectively, and the degree of surprise was obtained according to the listening distance and sound level. The sound was chosen to have a smaller value for retaliation compared to the simple sustaining and rhythmic repetition of the Clarkson sound. When the object test was performed, the rhythm Klaxon sound was reduced by −15 dB and the EEG was reduced by −10%. In conclusion, the simpler the klaxon sound, the more stress and surprises people felt. Using rhythm patten sound reduced noise and increased interest in sound.
3-D printed bulk absorbers
Authors: Sharma Bhisham , Wetter Kyle , Johnston Will
Published: December 2020

We present results from our recent efforts on the fabrication and acoustic characterization of 3-D printed porous absorbers. The acoustic properties of porous structures are dependent on their cellular microstructural architecture. Thus, controlling their local and global cellular architecture can allow a significant control over the acoustic properties of porous materials. Our focus here is on two different kinds of porous absorbers—open-celled absorbers with novel surface topologies and functional gradients, and bio-inspired fibrous absorbers. First, we apply stereolithographic printing to fabricate open-celled absorbers with novel surface topologies. The effect of parameters such as porosity, relative density, surface topology, and through-thickness porosity gradients on the sound absorption behavior is elucidated. Second, we explore the possibility of fabricating fibrous absorbers using fused deposition modeling. While 3-D printing allows fabrication of complex geometries, printing thin fibrous parts is significantly more challenging. Here, we compare two different techniques of printing such structures and present the effect of the fibrous architecture on the acoustic properties of the structure. The obtained results show that 3-D printing offers a promising new avenue of designing porous structures with tailored acoustic properties.