bluuebunny/crossref_metadata_2025 huggingface dataset:
Wide Range Compliance Solutions for Various Fracture Test Specimens Using Crack Mouth Opening Displacement
Authors: Ruggieri Claudio , Souza Rodolfo F. de
Published: October 2017

This work addresses the development of wide range compliance solutions for tensile-loaded and bend specimens based on CMOD. The study covers selected standard and non-standard fracture test specimens, including the compact tension C(T) configuration, the single edge notch tension SE(T) specimen with fixed-grip loading (clamped ends) and the single edge notch bend SE(B) geometry with varying specimen spam over width ratio and loaded under 3-point and 4-point flexural configuration. Very detailed elastic finite element analysis in 2-D setting are conducted on fracture models with varying crack sizes to generate the evolution of load with displacement for those configurations from which the dependence of specimen compliance on crack length, specimen geometry and loading mode is determined. The extensive numerical analyses conducted here provide a larger set of solutions upon which more accurate experimental evaluations of crack size changes in fracture toughness and fatigue crack growth testing can be made.
Oxidation Inhibited Graphite: What Is It?
Authors: Hantz Benjamin F.
Published: October 2017

When exposed to air at elevated temperatures, graphite oxidizes by a reaction between carbon and oxygen forming carbon monoxide and carbon dioxide. Using graphite as a sealing material and exposing it to the aforementioned environment, the reaction consumes graphite which degrades the sealing performance leading to leakage and seal unreliability. As a response to industry needs, graphite and sealing element manufacturers offer “oxidation inhibited” or more simply “inhibited” grades of graphite that show improved resistance to oxidation, however, there is no industry accepted definition that assures the purchaser that these grades of graphite do in fact have sufficient oxidation resistance for their specific application. This paper proposes a performance based definition for oxidation inhibited graphite and a protocol to convert test results to index any graphite resistance to oxidation. Furthermore, the paper provides a methodology to determine temperature limits and/or service life expectations for any graphite grade.
On-Site Vibration Test for Measuring Damping Ratio of PWR Reactor Coolant Loop
Authors: Ishiguro Takami , Numata Takeshi , Goshima Nobuyoshi , Monde Masatsugu , Fuyama Hiroyuki
Published: October 2017

In the Application for Construction Plan License after the Great East Japan Earthquake, it was needed to revalidate the damping ratio to apply 3% for seismic analyses of Reactor Coolant Loop (RCL) with two-point-support Steam Generators (SGs) which was normally 0.5% or 1% in the past Applications. For the revalidation, vibration tests of SGs were carried out at Unit 2 and Unit 3 in Mihama Power Station of the Kansai Electric Power Co., Inc.

In the test at Mihama Unit 2, SG top was hit horizontally by the pendulum type hammering device. As a result, in the hot leg (HL) direction, 9% damping ratio has been obtained. In the test at Mihama Unit 3, electro-hydraulic actuators were installed at the top of reinforced concrete wall surrounding SG and SG upper manhole was excited. In the excitation test, frequency response curves were obtained by changing the frequency stepwise in sinusoidal wave at constant amplitude. The damping ratio has been confirmed as more than 3%, specified in JEAG 4601-1991 as standard value, in the HL perpendicular direction which provided smaller damping ratio compared to the HL direction.

Dissipation energy of snubber was measured and it has been confirmed that snubbers themselves do not contribute damping effect for small SG displacement like tests in Mihama Unit 2 and Unit 3. Large dissipation energy of snubbers would be expected in earthquake. It has been realized that conservative large responses are computed in RCL seismic analysis if the damping ratios obtained are used.
Online Creep-Fatigue Monitoring of Cyclic Operation in a Coal-Fired Power Plant
Authors: Rosinski Stan T. , Coleman Kent , Berasi Mario , Carney Curt , Woerz Ulrich , Sanchez Andres , Sigali Stefano , Rossi Nicola
Published: October 2017

Coal-fired power plants are often required to cycle extensively and operate relatively infrequently due to power market conditions and an increasingly broad deployment of renewable energy. This cyclic (start-stop and/or fast ramp rate) operation can result in accumulation of fatigue damage, particularly in thick-walled components such as high temperature headers that experience the greatest thermal transients. In addition, components exposed to high temperature and pressure experience creep damage over time. Tracking the accumulation of creep and fatigue damage can aid in life management of these components. EPRI developed the Creep-FatiguePro™ system to monitor the accumulation of creep and fatigue damage in plant components while considering component geometry and the ongoing changes in operating conditions (temperatures, pressures and flow rates). The software requires a configuration process to define stress transfer functions for damage analysis and often involves performing a finite element analysis for each component geometry. Although accurate, this process can be time-consuming, especially if a large number of components are to be monitored. In a recent application of this system at the As Pontes power plant in Spain, a simple closed form analytical solution was used in the configuration process in order to more rapidly obtain the stress transfer functions. For direct interaction with the plant’s data historian, the software was also modified to support connection to the plant data system. Results using the two configuration approaches will be compared and recommendations made for future use in monitoring creep and fatigue damage in power plant components.
Technical Basis for ASME Code Section XI Nonmandatory Appendix C Update
Authors: Guzman-Leong Consuelo E. , Udyawar Anees
Published: October 2017

The ASME Boiler and Pressure Vessel (B&PV) Code Section XI Appendix C provides analytical procedures, criteria, and evaluation methodologies used to determine acceptability for continued service for a specified evaluation time period of flawed pipe. However, Appendix C applicability to subsurface flaws and flaws located on external pipe surfaces is unclear. Appendix C as currently written suggests surface flaws are (only) on the inner pipe diameter. It is recognized that flaw solutions specific to different combinations of the type of flaw, location on component, and failure mode may not be currently available. There are also inconsistencies in the equations for determining fracture toughness for ferritic piping between circumferential and axial-oriented flaws, and the allowable applied hoop stress definitions. Furthermore, there is recent work on several topics in Appendix C that necessitate updating Appendix C. Topics include stress intensity factor (SIF) solutions for circumferential and axial through-wall flaws in cylinders, and the method of combination of bending moments and torsion for elastic-plastic fracture mode and limit load analyses when the torsion stress does not exceed 0.2 times the flow stress. This paper summarizes the proposed ASME Code Section XI Appendix C revisions that will be incorporated in the 2017 edition of the Code. The impact of revising stress intensity factor solutions for circumferential and axial through-wall cracks in cylinders is also presented. In addition to technical changes, several errata are also suggested to be corrected.
A Successful Strategy for Managing the Mechanical Integrity of Coke Drums
Authors: Du Plessis Pierre , Samman Mahmod
Published: October 2017

A novel approach to mechanical integrity was utilized for addressing failures in an old set of coke drums. Using a rigorous routine of inspections, assessments, and long-term repairs, drums which had suffered accelerated deterioration, unpredicted cracks, and loss of containment were transformed to a reliable set of vessels. Despite old age and thin walls, due to the success of this strategy and results of a fatigue test program, plans to replace these vessels were canceled and the time between turnarounds is being considered for an increase. In this paper, we describe the approach that was used and compare results from this set of drums to another set at the same facility that was managed differently.
Direct Method on Creep Fatigue Damage Assessment Considering Full Creep-Cyclic Plasticity Interaction
Authors: Barbera Daniele , Chen Haofeng , Luan Weiling
Published: October 2017

This paper introduces the latest research and development of the Linear Matching Method (LMM) on the creep fatigue damage assessment of components subjected to high temperature and cyclic load conditions. The method varies from existing rule-based approaches in both the ASME Boiler and Pressure Vessel Code (NH) and the UK R5 high temperature assessment procedure, where the creep behavior/creep damage and cyclic plastic response /fatigue damage are analyzed separately. In support to these the extended Direct Steady Cycle Analysis (eDSCA) has been proposed to provide a more accurate description of the potentially dangerous interaction between creep and cyclic plasticity during the load cycle, and hence is able to accurately address creep enhanced plasticity and cyclically enhanced creep.

The applications of the LMM eDSCA method for creep fatigue damage assessment to three practical problems are then outlined to demonstrate that the proposed direct method is capable of predicting an accurate component life due to creep fatigue and creep ratcheting damages by modeling cyclic plasticity and creep interaction using this new simplified direct method, providing a degree of accuracy and convenience in creep fatigue assessment hitherto unavailable and without the restrictions inherent in other methodologies.
Study on Numerical Simulation of Gas-Solid Erosion for Feed Type Tee
Authors: Fang Zhou , Hu Weiwei , Liu Deyu , Li Guanghai
Published: October 2017

A series of numerical simulation about gas-solid erosion for feed type tee have been taken out. The gas-solid two phase flow was formed in the tee with the solid particles coming from the top of the tee pipes and air blowing from the left side. Tee pipes erosion situation was simulated by DPM model in Fluent software. The serious erosion location in the tee pipes was analyzed with different speeds of solid and air. The reasonable distribution method of the particle velocity and gas velocity was put forward and the particles were remained in the intermediate position of the pipes. So the collision with the wall was reduced, and the pipeline erosion rate was slowed down, in addition, the service life of pipes was prolonged.
Steam Generator Grade P91 Steel Components Creep-Assessment Through a Procedure for the Italian Code Application and Comparison With the ECCC Recommendations, American Standard
Authors: Grisolia Ottaviano , Scano Lorenzo
Published: October 2017

ASTM A 335-Grade P91 components of steam generators may be critical because of possible steel microstructure changes and/or embrittlement due to the FATT increase during service at high temperature: both phenomena may worsen the material creep behavior globally. Operation temperatures below 600°C such as in the worked case considered herein should be less critical; nevertheless, the worked case plan has included additional controls on microstructure also to have a reference for the future. Present study considers for the worked case steam generator the creep analysis of high-temperature-section (superheater / reheater) two components, outflow tubing and manifold: they may be critical because of the long continued service (110,000 hours or twelve years) and loading conditions (maximum operation temperature and applied stress at the intersection). Aim of the work is to compare life results from the Italian creep code with those predicted by the API 579-1; it also checks compatibility of results from the polynomial models in Italian, ECCC and API 579-1 procedures. Life results based on the Italian-code polynomial function are consistent with those based on the polynomial function proposed in ECCC: With preliminary stresses from pressure formulas, life estimates are a bit more conservative than the ECCC model’s. Finally, life results obtained through the API 579-1 Level 3 assessment appear consistent with those predicted by the Italian creep code, ECCC recommendations application.
Introduction of Scenario for Safe Use of Welded Joints Under High Pressure Hydrogen Gas
Authors: Fukumoto Hajime , Kobayashi Hiroshi , Oshima Shinji , Kawamata Kazunori
Published: October 2017

Japan began constructing and upgrading HRS (Hydrogen Refueling Stations) for its FCV (Fuel Cell Vehicle) demonstration program in 2002, as shown in Fig. 1. In 2013, Japanese energy providers started constructing commercial HRS for refueling FCV with 70 MPa hydrogen, and almost 100 HRS are now in service. Maintaining the reliability of refueling equipment is essential for safe, stable operation of commercial HRS. However, as a result of experience with commercial HRS operation during the past few years, Japanese energy providers have recognized that maintenance for small leaks from cone and thread mechanical joints involves a significant loss of resources.
Multiaxial Fatigue in Drill Pipes Under Non-Proportional Loading
Authors: Helmy Nahla A. , Younan Maher Y. A.
Published: October 2017

The scope of this research is to estimate the fatigue life and crack initiation direction in components subjected to multiaxial, nonproportional loading. Two critical plane approaches — Fatemi-Socie and McDiarmid — were used to estimate low cycle and high cycle fatigue lives, respectively. A software program (Elrond) was constructed to estimate the fatigue life and crack initiation plane. The code was validated using experimental fatigue data sets from previous research, then was applied to a real-life drilling problem. Drill pipe operating in the “Build and Hold” drilling job condition was analyzed using the developed software. Results were compared with the API RP7G fatigue design guidelines. Fatigue life charts were prepared using fatigue lives estimated by Elrond at several axial loadings, dogleg severities and torque amplitudes. Also, maximum allowable torque under high cycle fatigue conditions was estimated.
Blast Wall Shielding Effectiveness
Authors: Geng Jihui , Thomas J. Kelly
Published: October 2017

Blast walls are frequently considered as a potential mitigation option to reduce the applied blast loading on a building or structure in cases where unacceptably high levels of blast damage are predicted. There are three general explosion types of interest with respect to blast loading: High Explosive (HE), Pressure Vessel Burst (PVB), and Vapor Cloud Explosion (VCE). The blast waves resulting from these explosion types can differ significantly in terms of blast wave shape and duration. The effectiveness of a blast wall depends on these blast wave parameters (shape and duration), as well as the blast wall parameters (e.g., height, width and standoff distance from the protected structure). The effectiveness of a blast wall in terms of mitigating the blast loading on a protected structure depends on the combination of the blast wave and blast wall parameters. However, little guidance is available on the effectiveness of blast walls as a mitigation option for non-HE explosion sources. The purpose of this paper is to characterize the effect of blast wave parameters on the effectiveness of a blast wall and to provide guidance on how to determine whether a blast wall is an effective and practical blast damage mitigation option for a given blast loading.
Seismic Qualification of Piping System by Detailed Inelastic Response Analysis: Part 2 — A Guideline for Piping Seismic Inelastic Response Analysis
Authors: Otani Akihito , Shibutani Tadahiro , Morishita Masaki , Nakamura Izumi , Watakabe Tomoyoshi , Shiratori Masaki
Published: October 2017

A Code Case in the framework of JSME Nuclear Codes and Standards is currently being developed to incorporate seismic design evaluation of piping by detailed elastic-plastic response analysis and strain-based fatigue criteria as an alternative design rule to the current rule, in order to provide a more rational seismic design evaluation. The Code Case provides two strain-based criteria; one is a limit to maximum amplitude of equivalent strain amplitude derived from detailed analysis and the other is a limit to the fatigue usage factor also based on the equivalent strain amplitude.

A guideline for piping seismic analysis based on inelastic response analysis is also being developed as a mandatory appendix for the code case. The guideline provides the methodology to obtain the elastic and plastic strains in seismic response and contains descriptions for analysis code, FE modeling including material property definition, time history analysis method, damping, seismic input condition and verification and validation method. This paper introduces the outlines of them.
Blast Resilient Design of Infrastructure Subjected to Ground Threats
Authors: Salem Shady , Campidelli Manuel , El-Dakhakhni Wael , Tait Michael
Published: October 2017

The growing number of terrorist attacks in the past decade has focused the public’s attention on the severity of such a man–made hazard. The rising threat of improvised explosive devices — one of the most successful attack strategies — has significantly increased the number of threats on the ground, in the form of suicide–bombs, vehicle–bombs, etc., thereby requiring the development of more effective blast risk mitigation measures. However, the modern proliferation of such measures poses the problem of evaluating their cost–effectiveness, which prompts the need for a comprehensive optimization methodology — capable of maximizing the resilience of the built environment. The aim of this paper is to lay out the foundations of a resilience–based framework for quantifying the performance of different infrastructure elements incurring blast threats, by means of functionality and resilience indicators. The proposed framework can quantify the consequences of multiple outdoor explosions typified by the emblematic car–bomb scenario. The level of localized damage is evaluated via pressure–impulse diagrams; local failures are then aggregated into the definition of resilience and functionality indicators, designed to provide the analyst with a comprehensive picture of global damage, residual functionality, and downtime of the structural system.
Research on Two-Phase Flow Induced Vibration Characteristics of U-Tube Bundles
Authors: Nai-bin Jiang , Li-xia Gao , Xuan Huang , Feng-gang Zang , Fu-rui Xiong
Published: October 2017

In steam generators and other heat exchangers, there are a lot of tube bundles subjected to two-phase cross-flow. The fluctuating pressure on tube bundle caused by turbulence can induce structural vibration. The experimental data from a U-tube bundle of steam generator in air-water flow loop are analyzed in this work. The different upper bounds of buffeting force are used to calculate the turbulence buffeting response of U-tubes, and the calculation results are compared with the experimental results. The upper bounds of buffeting force include one upper bound based on single-phase flow, and two upper bounds based on two-phase flow. It is shown that the upper bound based on single-phase flow seriously underestimated the turbulence excitation, the calculated vibration response is much less than the experimental measurement. On the other hand, the vibration response results calculated with the upper bounds based on two-phase flow are closer to the measured results under most circumstances.
A Method for Field Evaluation of Heat Treatment to Identify Vessels That Are Susceptible to Sulfide Stress Cracking
Authors: Ramirez Guillermo , Kenady Kollin , Jackson Joshua E.
Published: October 2017

Inadequate heat treatment in the head and head-to-shell weld areas of a low-pressure separator vessel was determined to have led to conditions which allowed for the development of sulfide stress cracks, and ultimately resulted in rupture of the vessel. This determination was made through the use of destructive testing and failure analysis of the ruptured vessel. Generally, verification of vessel heat treatment is done through review of temperature recordings from manufacturing documentation or third party verification at the time of fabrication. Unfortunately, heat treatment records of pressure vessels are often misplaced, lost during acquisitions/mergers, or simply never existed.

Under the assumption that these vessels were adequately heat treated, the vessel’s owners do not normally take into consideration the high residual stresses which create favorable conditions for sulfide stress cracking (SSC) and other stress corrosion cracking type damage mechanisms. In this case, cold formation of the head resulted in high residual stresses in the flange and knuckle regions. The welds, which had not been properly post-weld heat treated, similarly had high residual stresses. These high stresses resulted in favorable conditions for the SSC to occur when exposed to a corrosive environment such as oil and gas operations.

In an effort to prevent similar events from occurring in the future, it was determined to be necessary to evaluate other vessels for inadequate heat treatment that may result in SSC. A non-destructive approach was investigated to evaluate vessels, especially in the absence of the aforementioned heat treatment records, to determine if the formed heads and heat affected zones after welding had adequate heat treatment. A method was developed to identify vessels without adequate heat treatment utilizing standard non-destructive testing techniques. There is the potential that many other low pressure vessels in lethal service could have received inadequate heat treatment. This methodology can therefore be used to determine the heat treatment state for these pressure vessels without destructive testing.
Shock Waves, Vibrations, and Resonance in Linearly Elastic Beams
Authors: Leishear Robert A.
Published: October 2017

Equations can describe the stresses in linearly elastic simple beams, subjected to different types of suddenly applied, or dynamic, incident loads. The assumption of linearly elasticity simplifies the nonlinear aspects of structural vibrations. Simplified linear models are applicable to many vibration analyses, and provide significant insights into vibration behavior.

When a load impacts a beam, there are two different stresses created. The primary bending stress is the bending stress of the beam due to perpendicular loading. The secondary bending stress is a much higher frequency bending stress that travels along the surface of the beam relative to the moving load front. In general, the primary bending stress has a much larger magnitude than the secondary bending stress. The maximum stress values for the primary and secondary bending stresses may be described by dynamic load factors (DLF’s); where the maximum stress caused by an applied load equals the DLF multiplied by the static stress; and the static stress is the equilibrium stress for the load in question applied to the beam.

For example, consider the primary stresses due to a sudden pressure increase, which is applied perpendicular to a beam’s axis. The maximum stress in that beam is double the static stress, and deflection, that would be caused if that incident pressure is statically applied. That is, the DLF < 2 for a pressure that is suddenly applied over the incident surface of a beam: the maximum possible stress is twice the static stress.

Now consider the secondary stress. A localized bending stress occurs when a pressure wave travels parallel to the axis of a beam, and this bending stress has a DLF < 4. That is, a high frequency bending stress travels along the beam with a maximum magnitude equal to four times the applied pressure; the maximum stress is four times the static stress.

As other examples, stresses due to different types of loads may be evaluated. A gradually increasing pressure yields 1< DLF < 2, depending on the loading rates. A harmonically applied load may yield a DLF theoretically equal to infinity, but damping greatly reduces the maximum DLF. Also, these harmonic loads can significantly excite higher mode frequencies, i.e., the applied load may excite any one of a number of a structure’s natural frequencies. New theory is presented here to describe shock waves, suddenly applied loads, and resultant vibrations to coherently relate these complex quantities.
Influence of Defect Distribution on Dynamic Elastic Buckling of Rings Under Internal Uniformly-Distributed Pressure Pulse
Authors: Dong Qi , Yang Sha , Zhang Liucheng
Published: October 2017

In our previous papers, it has been reported that when rings and shells are subjected to an internal uniformly-distributed pressure pulse, dynamic elastic buckling due to the nonlinear coupling between the breathing mode and bending modes may occur and further cause the strain growth phenomenon in explosion containment vessels. In this study, the influence of defect distribution on dynamic buckling of plane-strain rings under internal uniformly-distributed pressure pulse is studied, in which three cases with one defect, six defects and twelve defects are employed in the finite element model. It is found that defects influence the initial buckling response shapes and occurrence of dynamic buckling. However, the excited bending mode is the same for the different defects distribution cases.
Investigation on the Loading Characteristics in Proof Units
Authors: Zhang Liucheng , Dong Qi , Yang Sha
Published: October 2017

Blast-proof unit is designed to alleviate the shock wave transmitting to the other unit, in which the damage of accidental explosion is mainly caused by the transmission wave through the wall and diffraction wave over the upper edge. Investigation on the blast flow field in blast-proof units subjected to internal blast loading is studied by numerical simulation in the current paper. The influence of the height of the proof unit is analyzed and on the cap situation is studied. The result shows that it may not have a positive effect on reducing the diffraction wave by increasing the height of units, because it may enhance the reflection wave, which might have a greater effect than the diffraction wave. We can reduce the shock wave in the next unit by adding a cap, which is very effective. The study may contribute to further understanding on the experiment results and the design of blast-proof units.
Microstructural Evaluation of 9Cr-3W-3Co-Nd-B Heat-Resistant Steel (SAVE12AD) After Long-Term Creep Deformation
Authors: Hamaguchi Tomoaki , Okada Hirokazu , Kurihara Shinnosuke , Hirata Hiroyuki , Yoshizawa Mitsuru , Iseda Atsuro
Published: October 2017

The new ferritic heat-resistant steel composed of 9Cr-3W-3Co-Nd-B, registered as ASME Code Case 2839, has been developed for large diameter and heavy wall thickness pipes and forgings of fossil-fired power boilers. The steel, which contains 0.01 mass% boron, a small amount of neodymium, and optimized amounts of nitrogen, is characterized by the superior long-term creep strengths of both the base metal and welded joint. P92 had equiaxed subgrain structures changed from martensite lath structures and coarsened M23C6 type carbides after long-term creep. In contrast, the developed steel, SAVE12AD, maintained martensite lath structures with fine M23C6 along the boundaries even after the long-term creep stage. The addition of high amounts of boron suppressed the coarsening of M23C6 along the boundaries, thereby stabilizing the martensite lath structure in the base metal of the steel. Consequently, SAVE12AD had higher creep rupture strength than other high chromium ferritic steels.

To investigate the creep rupture strength of welded joints, two welded joints with Ni-based alloy and Grade 92 welding filler wires were prepared by automatic gas tungsten arc welding. The creep rupture strength of each welded joint showed small degradation compared with the base metal in the long-term creep stage over 10,000 hours. These were ruptured 1.5 mm away from the fusion line, which was the same area as Type IV cracking. Microstructural observations were carried out by electron back scatter diffraction analysis using simulated heat-affected zone samples at different peak temperatures from 750 °C to 1350 °C in order to clarify the microstructure in the heat-affected zone. No fine grain area was observed in the microstructure after the simulated heat-affected zone at 910 °C just above AC3 transformation temperature, although there were fine grains along prior austenite grain boundaries, which seemed to form with the diffusion transformation. The creep cracks seemed to have initiated from the fine grain structures, resulting in the rupture at the same area as Type IV cracking. However, the creep rupture strength degradation of the welded joints against the base metal was significantly smaller than that of conventional steel welded joints owing to the suppression of fine grains found in the heat-affected zone heated around AC3 temperature.

The developed 9Cr-3W-3Co-Nd-B steel (SAVE12AD) will be used for large diameter and heavy wall thickness pipes and forgings in 600 °C ultra super critical power plants.
Computational Investigation of Composite Repair Materials Preventive Effects on Wrinkle Bends Fatigue Failure
Authors: Kiani Mahdi , Mally Timothy , Walker Roger , Locke Eric
Published: October 2017

Wrinkle bending was a vintage technique in pipeline construction for aligning pipe sections. However, this process causes severe geometry changes over the pipeline structure and thus stress concentrations are developed. These stress concentrations have the potential to cause catastrophic pipeline failure due to internal pressure cycles, seismic effects and temperature changes. Different techniques have been studied and examined to mitigate the destructive effects that wrinkle bends pose to pipeline integrity. Composite repair methods and materials have been proven as one of the most reliable and efficient technologies to repair different pipeline defects. Designing an economical composite repair for a wrinkled pipe with proper performance requires precise design considerations. Finding an economical balance can be achieved multiple ways, such as performing experimental tests or applying analytical formulas and procedures. Each of these two methods has its own drawbacks: cost, errors and time can prevent accurate experimental tests and poor accuracy. Applicability of suggested analytical design equations can render certain analyses useless. To technically and economically improve the design and application processes of composite repair systems for wrinkle bends, elastic finite element analysis (FEA) was performed. The FEA analysis was conducted to study the effects of applying composite repairs on the elastic stress concentration factor of the wrinkle section of a Grade X52 carbon steel pipe. Moreover, a nonlinear kinematic hardening material model was developed and calibrated for this same steel. An elastic-plastic FEA was implemented to evaluate the stress-strain response of a wrinkled pipe subjected to a cyclic bending loading and constant internal pressure. Different strain based fatigue life estimation approaches were used to estimate the fatigue life enhancement achieved by utilizing a proprietary composite repair installation method.
Low-Damage Design Philosophy for Future Earthquake-Resistant Structures
Authors: Chouw Nawawi
Published: October 2017

Current seismic design philosophy used worldwide tolerates a degree of damage at locations predefined by the designer, as long as a complete structural collapse is precluded. By accepting plastic deformations, the maximum acceptable forces can be controlled and construction costs can be reduced. Major earthquakes, e.g. the Canterbury earthquakes, showed that well-designed structures behave as anticipated. The joints suffered plastic deformation as the designer intended, while the occupants remained alive. Repair costs, however, were often high. Costs also accrue because, post-earthquake, the infrastructure is no longer fit for purpose. These costs are very difficult to predict.

Low-damage seismic design, in contrast, can be achieved by activating rigid-like body movement of structural members. Development of forces resulting from structural local deformation can then be prevented. Consequently, associated damage to structural members can be avoided. Recent research outcomes at the University of Auckland Centre for Earthquake Engineering Research will be presented.
The Research of the Fitness-for-Service Assessment on Steels for Pressure Vessel Subjected to Fire Damage: Metallurgical Analysis and the Influence on Performance Degradation
Authors: Li Bo , Zuo Yantian , Shu Wenhua , Tang Xiaoying
Published: October 2017

The fitness-for-service assessment to fire damage for pressure vessels was considered to be based on the material deterioration and performance degradation associated with heat exposure. The identification of thermal damage zones after exposure to fire was proposed and provided in the API 579-1/ASME FFS-1 Standard. However, the more explicit quantitative relationships between the heat exposure conditions and the performance degradation degree of the pressure vessels suffering fire were not reported in detail with the thermal damage zone metallurgical analysis, which was not available in the Standard. Therefore, the present research was conducted on the influences of fire suffering test and heat exposure, under different thermal conditions, on the micro-structure evolution and mechanical performance of austenitic stainless steels and carbon steels for pressure vessel equipment. And the metallurgical analysis results described some typical appearances in micro-structure observed in the materials experienced to fire and heat exposure. Moreover, the quantitative degradation of mechanical properties was investigated via multiple testing means such as mechanical tensile test at room temperature and low temperature, the Charpy impact testing, the torsion testing, and the hardness measurement. The present research provided data accumulation of material deterioration and performance degradation was believed to be benefited to the fitness-for-service assessment of pressure vessel after exposure to fire. The material thermal degradation mechanism and the fitness-for-service assessment process of fire damage behavior was further discussed.
A Spectrum-to-Spectrum Method for Calculating Uniform Hazard Floor Response Spectra
Authors: Lucchini Andrea , Franchin Paolo , Mollaioli Fabrizio
Published: October 2017

In codes’ provisions and design procedures for acceleration-sensitive nonstructural components, seismic demand is commonly defined by means of floor response spectra expressed in terms of pseudo-acceleration. Depending on the considered analysis method, floor response spectra may be derived from floors’ acceleration histories, based on structural response-history analysis, or calculated using a predictive equation from a given input ground motion spectrum. Methods for estimating floor response spectra that are based on the second alternative are commonly called spectrum-to-spectrum methods. The objective of this paper is to briefly review these methods, and to discuss the main assumptions they are based on. Both predictive equations from selected seismic codes and proposals from the literature are included in the review. A new probability-based method, recently developed by the Authors for generating uniform hazard floor response spectra, namely, floor response spectra whose ordinates are characterized by a given target value of the mean annual frequency of being exceeded, is also described. By using this method floor spectra are determined through closed-form equations, given the mean annual frequency of interest, the damping ratio of the spectra, the modal properties of the structure, and three uniform hazard ground spectra. The method is built on a proposal for a probabilistic seismic demand model that relates the ground spectral acceleration with the floor spectral acceleration, and is able to explicitly account for the ground motion variability of the nonstructural response. Results for a case study consisting of a service frame of a visbreaking unit in an oil refinery are presented to show the good predictive accuracy of the method with respect to exact uniform hazard floor response spectra obtained through a standard probabilistic analysis.
Selection of Representative Stress Function Under Multiaxial Stress State Condition for Creep
Authors: Haque Mohammad Shafinul , Stewart Calvin M.
Published: October 2017

Drives to develop more efficient pressure vessel and piping systems has led to complex geometry containing discontinuities such as holes, grooves, gaskets, crevices, notches etc. A multiaxial state of stress often develops in complex engineering components subject to creep conditions. Under multiaxial creep, the rupture life and creep ductility are not consistent with uniaxial creep experiments. A common practice to account for multiaxial creep is to introduce a scalar representative stress or strain that describes the multiaxial state within the materials enabling accurate predictions of rupture and creep ductility. Many functions have been proposed in literature and international pressure vessel and piping codes and standards. The ASME B&PV III, French RCC-MR, and British R5 recommends different phenomenological approaches to multiaxial creep. In this study, seven representative stress and eight representative strain functions are evaluated. The skeletal point approach to calibrating these functions is discussed. The incompressibility of the representative stress functions is analyzed. Rupture surfaces of the representative stress functions under biaxial stress conditions are generated to compare the advantages and limitations of the functions. Several functions are found to exhibit divide by zero errors and/or imaginary number errors leading to unstable and discontinuous rupture surfaces. It is observed that the selection of an appropriate representative function is dependent on loading condition, geometry, and material properties. The Hayhurst and Huddleston representative stress functions are found as the most suitable functions to predict multiaxial rupture for a general multiaxial stress states. Finally, a guideline to the selection of the appropriate representative stress function and the associated incompressibility condition is presented.
Aeroacoustic Source of Multiple Cavities and Prediction of Self-Excited Oscillations
Authors: Shaaban Ayman A. , Ziada Samir
Published: October 2017

Self-sustaining oscillations of flow over ducted cavities and corrugated pipes proved to be a potential source of tonal noise and possible failure in industrial applications. Most of the recent studies focused on the flow over a single cavity to simplify the problem and establish basic understanding of the phenomenon. This paper investigates experimentally the flow over multiple cavities, specifically two and three-cavity configurations, and the results are compared with those of a single cavity. Two different categories of experiments were performed in this study. The first category of measurements quantified the aeroacoustic source of various cavity configurations as a function of Strouhal numbers and acoustic velocity of the resonant pipe mode. The cavities are situated at the acoustic pressure node of a piping system which was sufficiently long to maintain the acoustic velocity fairly constant along the test section. The second category involved self-excited oscillations where the cavities were tested in a short piping system. The flow velocity was gradually increased and the acoustic pressure amplitude and frequency were measured and the lock-in ranges for different shear layer modes were identified. A semi-empirical model is then developed to use the measured source to predict the self-excited oscillation amplitude.
The EPRI PWR Supplemental Surveillance Program (PSSP) Final Design and Implementation
Authors: Server William , Burgos Brian , Hardin Tim , Hall J. Brian
Published: October 2017

There is a lack of pressurized water reactor (PWR) surveillance program transition temperature shift and upper shelf toughness decrease data due to neutron irradiation exposure especially at high fluences indicative of 60 to 80 years of plant operation. The Electric Power Research Institute (EPRI) has funded the development of a supplemental reactor pressure vessel (RPV) surveillance program to allow testing of additionally irradiated specimens in two new capsules being installed in two different commercial reactor surveillance capsule positions. The previously irradiated materials were strategically selected and will be further irradiated to give final fluence levels equal to or above those for PWRs operating up to 80 years. This paper describes the final design of the capsules and selection of the key previously irradiated RPV materials reconstituted into new Charpy-size specimens being irradiated in the two PWR Supplemental Surveillance Program (PSSP) capsules.
Fundamental Study on Evaluation Method of Nonlinear Sloshing Wave Height of Cylindrical Tanks
Authors: Morita Hideyuki , Takata Tomosige , Madokoro Hideki , Sago Hiromi , Murakami Hisatomo , Yokoi Shinobu , Yamamoto Tomohiko
Published: October 2017

When cylindrical tanks installed in the ground, such as oil tanks and liquid storage tanks, receive strong seismic waves, including the long-period component, motion of the free liquid surface inside the tank called sloshing may occur. If high-amplitude sloshing occurs and the waves collide with the tank roof, it may lead to accidents such as damage to the tank roof or outflow of internal liquid. Therefore, it is important to predict the wave height of sloshing generated by an earthquake input.

Sloshing is vibration of the free liquid surface, and when the sloshing wave height is small, it can be approximated with a linear vibration model. In that case, the velocity-response-spectrum method using velocity potential can estimate the sloshing wave height under an earthquake input. However, when the sloshing wave height increases and the sloshing becomes nonlinear, it is necessary to evaluate the wave height using other methods such as numerical analysis.

Taking into consideration that design earthquake levels tend to increase and the use of seismic isolation mechanisms has continued to spread in recent years, it is possible that the long-period components of an earthquake input which act on cylindrical tanks will also increase. Therefore, although it is thought that the evaluation of nonlinear sloshing wave height is important, there are few examples which quantitatively evaluate the wave height of nonlinear sloshing.

In this study, as a simple evaluation technique of a nonlinear sloshing wave height, the applicability of the correction coefficient proposed by Shimada et al. was examined based on the flow analysis which used Volume of Fluid (VOF) method. Moreover, it was studied that the VOF method can be used to evaluate nonlinear sloshing wave height and sloshing wave crest impact pressure acting on the fixed roof of a tank.

Shaking table tests will continue to be carried out in order to verify the applicability of the simple evaluation technique of nonlinear sloshing wave height. Results from flow analysis code will also be validated against these test results.
Core Seismic Experiment and Analysis of Full Scale Single Model for Fast Reactor
Authors: Iwasaki Akihisa , Matsubara Shinichiro , Yamamoto Tomohiko , Kitamura Seiji , Harada Hidenori
Published: October 2017

To design fast reactor (FR) core components, seismic response must be evaluated in order to ensure structural integrity. Generally, the fast reactor core is made of several hundred core elements in hexagonal arrangement. When a big earthquake occurs, large horizontal displacement, vertical displacement (raising) and impact force of each core element may cause a trouble for control rod insertability, reactivity insertion and core element intensity. Therefore, a seismic analysis method of a fast reactor core considering three-dimensional nonlinear behavior, such as bouncing, impact, fluid-structure interaction, etc. was developed. This paper presents a validation of the core element vibration analysis code in three dimensions (REVIAN-3D) for a full scale model. In this validation, the vertical behavior (rising displacement) and horizontal behavior (Impact force, horizontal response) as a single core element of the analysis result agreed very well with the experiments.
Effect of Postweld Heat Treatment Conditions on Microstructure of 9Cr-1Mo-V Steel Welds for Pressure Vessel
Authors: Terasaki Hidenori , Tanaka Tomohiro , Abe Masamitsu , Nakatani Mitsuyoshi
Published: October 2017

We investigated the effects of post-weld heat treatment conditions on the microstructure of the multi-pass submerged arc weld metal of 9Cr-1Mo-V steel used in pressure vessels. The microstructural properties were analyzed under three conditions (as-weld, Larson-Miller parameter (LMP) = 21.38 × 103, and LMP = 21.99 × 103). The precipitation behavior was observed using scanning electron microscopy, and the difference in precipitation behavior in the “as-welded” and “reheated” regions of the prepared multi-pass weld metal was clarified at the different LMP values. The precipitate was analyzed using scanning transmission electron microscopy. An oxide and two types of precipitates were identified, and a dislocation network pinned by MX-type carbides was visualized under the low-LMP condition. The effects of LMP on the effective grain size and dislocation amount were also evaluated using electron back-scattering diffraction. All microstructural change along the LMP had a positive effect on the toughness of weld metal.
Self-Excited Vibration of a Plate Supported by Air Pressure in a Floating Conveying Machine
Authors: Takeda Masakazu , Watanabe Masahiro
Published: October 2017

This paper presents experiments and an analysis on self-excited vibration of a plate supported by air pressure in a floating conveying machine. In this study, the instability conditions are examined by theoretical analysis in consideration of the effect of compressibility of air in a chamber. The system’s characteristic equation is derived from the plate motion coupled with equations of the gap flow between the plate and the chamber surface. The vibration characteristics and the instability conditions of the self-excited vibration are examined through experiments. The stability of the plate is affected by an air flow rate, a mass of the plate, a spring stiffness of the plate. We clarified those influences on the instability conditions of the self-excited vibration. The unsteady fluid force acting on the plate (bottom surface) is investigated by measuring the unsteady pressure. The local work done by the unsteady fluid force is also clarified. Lastly, the instability mechanism and important parameters of the self-excited vibration are discussed based on the theoretical model and experimental results.