bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization and Modelling of Tensile Flow Behavior of Ni Base Alloy 690 at Various Temperatures and Strain Rates
Authors: Blaizot Jérôme , Chaise Thibaut , Nelias Daniel , Perez Michel
Published: November 2014

Pressurized Water Reactor components are welded by Gas Tungsten Arc Welding (GTAW). To achieve good corrosion resistance and mechanical properties, Ni base alloy 690 is used to manufacture these components. The understanding of physical phenomena involved during welding and the prediction of induced residual stresses are crucial to guarantee high quality of these components. Welding induces drastic changes in the microstructure of the molten zone and heat-affected zone of metallic alloys especially for multi-pass welding. These changes may deteriorate the mechanical properties of the assembly. In order to reproduce the complex thermo-mechanical loading occurring within the heat affect zone, experiments on a thermo-mechanical simulator Gleeble 3500 have been carried out. In order to characterize the base alloy, isothermal tensile tests have been performed at various strain rates and temperatures (from 25 to 1100°C). A constitutive law has been proposed to predict the mechanical properties under different strain rates and temperatures. Tensile tests have also been performed after several thermal cycles to understand the effect of welding on mechanical properties of Ni alloy 690. In parallel, grain size evolution and carbide precipitation have been characterized and correlated to measured mechanical properties.
Automated Ultrasonic Testing Optimizes Integrity Evaluations for Underground Piping Inspections
Authors: Cilluffo Graig
Published: November 2014

This paper will provide an overview of a recent buried piping inspection project leveraging automated ultrasonic testing methods to evaluate internal raw water corrosion at a reliably-operating, nuclear power plant. Discussion of current piping inspection practices for resolving non-planar flaws in raw water piping will be provided, emphasizing inspection performance requirements and a pilot project using automated scanning to optimize inspection value while minimizing field time and costs.

Contents include past buried piping integrity inspection scope / method selection, details on techniques and critical success factors for the project relative to integrity needs, lessons learned from field implementation, further experience from subsequent related inspections using automated and manual techniques for comparison, and recommended actions for future integrity assessments and mitigating actions. Results provided clear justification for this new approach above traditional evaluations performed in the past and may represent a best industry practice for buried pipe assessment.

While targeting buried piping applications, this method can be applied to many systems / locations vulnerable to corrosion. Guidance on applications, limitations, and areas for improvement are also provided from a project / field perspective.
Piping Corrosion Rate and Remaining Life Basis: Commercializing Conservatism in First Time Inspections
Authors: Cilluffo Graig
Published: November 2014

This paper sets forth guidance on how to establish a justifiable internal corrosion rate following a first time inspection to predict re-inspection or replacement timing for raw water piping. A novel approach leverages actual plant-wide piping inspection data, leak history, repair history, and corrosion monitoring results together to inform integrity decisions based on experience at a reliably-operating, nuclear power plant. Data is applied on a risk-conscious basis to piping systems based upon failure consequence and uncertainty and differs from the typical approach of reporting location-specific, time-averaged rates. Excavation and in-plant inspection results can now inform commercially-friendly conservatism that reduces leak risks while also minimizing total inspection and maintenance costs.

While directly applicable to buried piping, this method can be applied to any corrosive system / location. Information is presented in a format that readers can readily follow to develop similar justifications for their own sites / systems. Guidance on applications, limitations, and areas for improvement are also provided.
Flow-Excited Acoustic Resonance of Single Finned Cylinder in Cross-Flow
Authors: Arafa Nadim , Mohany Atef
Published: November 2014

The flow-excited acoustic resonance of single straight finned cylinder in cross-flow is investigated experimentally in this work. This phenomenon has been investigated in some detail for the case of bare cylinders; however, the effect of adding fins to the cylinders on the flow-sound interaction mechanism is not yet fully understood. During the experiments, the acoustic cross-modes of the duct housing the cylinder are self-excited due to the vortex shedding that emerges from the cylinder’s surface. In order to determine the effect of different fin parameters on the onset and intensity of acoustic resonance, fourteen different finned cylinders with fin thickness ranging from 0.35 to 1.5 mm and fin density ranging from 4 to 13.7 fin/inch are investigated for a Reynolds number ranging from 3.2×104 to 2.6×105. The onset and intensity of the acoustic resonance generated from each finned cylinder are compared to those generated from an equivalent bare cylinder with the same effective diameter. It is observed that the finned cylinders experience an earlier acoustic resonance and higher levels of acoustic pressure compared to their equivalent bare cylinders. This suggests that adding fins to the cylinder enhances the flow coherence along the cylinder’s span and thus makes the flow more susceptible to acoustic excitation. Moreover, it is observed that for constant fin spacing the acoustic pressure amplitude increases and the acoustic resonance occurs at earlier velocities as the fin thickness increases. On the other hand, for constant fin thickness, as the fin spacing increases the amplitude of the acoustic pressure decreases, while the onset of the resonance is delayed. Finally, the effect of the cylinder’s aspect ratio is investigated in three different test sections. It is observed that the amplitude of the excited acoustic resonance depends on the cylinder’s aspect ratio. The acoustic resonance amplitude is weaker for finned cylinders with aspect ratio less than 5 compared to their equivalent bare cylinders. However, finned cylinders with aspect ratio higher than 6 produces stronger acoustic resonance compared to their equivalent bare cylinders.
ASME Section III Flaw Tolerance Sample Problem for Fatigue Design of Nuclear System Components
Authors: Dewees David J. , Hirschberg Paul , Reinhardt Wolf , Stevens Gary L. , Roarty David H. , Gosselin Steve , Wright Keith , Damiani Thomas M.
Published: November 2014

An ASME Section III Task Group (TG) was formed in 2012 to develop alternate rules for the design assessment of Section III Class 1 nuclear components subject to fatigue service with environmental effects. Specifically, a flaw tolerance approach is being investigated based on similar methodology to that found in ASME Section XI Nonmandatory Appendix L. A key initial task of the TG (which reports to the Section III Working Group on Environmental Fatigue Evaluation Methods) was to develop and solve a detailed sample problem. The intent of the sample problem was to illustrate application of proposed rules, which will be documented as a Section III Code Case with a supporting technical basis document. Insights gained from round robin solution of the sample problem are presented and discussed in this paper. The objective of documenting the findings from the sample problem are to highlight the observed benefits and limitations of the proposed procedures, particularly how rules typically associated with in-service experience might be adapted into design methods.

The sample problem is based on a heavy-walled stainless steel nozzle that meets cumulative fatigue usage requirements in air (i.e., usage factor, U, without reactor water environment effects less than unity), but fails to meet usage factor requirements when environmental fatigue effects are applied.

The sample problem demonstrates that there is a class of problems dominated by severe thermal transients where fatigue initiation is predicted based on elastic methods including environmental effects, but fatigue crack propagation results are acceptable. Preliminary conclusions are drawn based on the results of the sample problem, and the next steps are also identified.
Review and Development of Primary Load Elevated Temperature Design Rules
Authors: Dewees David J. , Hantz Benjamin F.
Published: November 2014

A recent high temperature steam header case study is extended here to include alternate methods of review, including elastic stress and isochronous strain analysis and accompanying limits. The previous creep analysis was formulated to be exactly consistent with the allowable stress basis, such that alternate design analysis methods and criteria could be rigorously compared. In the current work, the selection of the appropriate limits for elastic results is investigated, as discussed in previous literature, which is motivated by stress redistribution characteristics of the primary (and secondary) loading in a typical header. Next, use of isochronous stress-strain curves generated from the same consistent (Omega) creep model are used for analysis and compared to candidate strain limits. The analyses show that both elastic and isochronous analysis have potential for effective creep design in the context of current high temperature design modernization activities. Finally, multiaxial creep behavior and its effect on detailed creep, elastic and isochronous stress-strain analyses and corresponding limits is also introduced.
Design and Analysis of Shipping Container for Big Rock Decommissioned Reactor Vessel
Authors: Slimp Bruce (Bart) , Papp Mick , Hoang Phuong H.
Published: November 2014

A major milestone in 2003 on the Big Rock Point (BRP) decommissioning project involved shipping the Reactor Vessel (RV) in a steel cask for burial. The Reactor Vessel Transport System (RVTS) cask was a sealed integral container, which provided necessary radiological shielding and containment of radioactive waste for shipping and disposal. The RVTS, using the provisions of the ASME BPVC Section III, Subsection NB, was designed as a Type B package in accordance with the requirements of 10 CFR Part 71. This included meeting Normal Condition of Transport (NCT) and the Hypothetical Accident Conditions (HAC) loading per 10 CFR 71, Regulatory Guide 7.6, “Design Criteria for the Structural Analysis of Shipping Cask Containment Vessels,” Regulatory Guide 7.8, “Load Combinations for the Structural Analysis of Shipping Casks for Radioactive Material” and Regulatory Guide 7.11, “Fracture Toughness Criteria of Base Material for Ferritic Steel Shipping Cask Containment Vessels with a Maximum Wall Thickness of 4 Inches.” The RVTS was designed to withstand accelerations and shocks postulated during highway and rail transit using guidelines from the Association of American Railroads (AAR) and ANSI N14.2. The design analysis methodology, fabrication process and transportation planning for the Big Rock RVTS Cask are presented in this paper.
Validation Approaches for Weld Residual Stress Simulation
Authors: Hill Michael R. , Tran Minh N. , Broussard John E.
Published: November 2014

In assessment of stress corrosion cracking behavior of susceptible welded materials, the contribution of weld residual stress is a key input for stress intensity factor calculations, which in turn are used to determine anticipated crack growth and to plan for inspection or repair. Without accurate weld residual stress information, it is challenging to develop an optimal plan for plant management. Weld residual stress simulations, based on non-linear finite element computations, provide a means to estimate residual stresses in components. However, there is no established, consensus approach for weld residual stress model validation, which could be used to judge model quality, specifically with respect to the influence of residual stress output on plant management decisions. A consensus model validation approach would benefit a broad range of stakeholders in pressure vessel technology.

The paper provides technical detail of example approaches for weld residual stress model validation, and applies these approaches to a set of weld residual stress model outputs that were developed in the context of an industry round robin. The set of outputs is from Phase 2a of the international round robin organized cooperatively by the U.S. Nuclear Regulatory Commission and the Electric Power Research Institute. Example validation approaches include comparisons of output from one model with output from other models, as well as comparisons of model output with data from residual stress measurements. The figures of merit used for comparisons range from simple (e.g., evaluation of mechanical section forces) to complex (e.g., comparison of predicted crack growth behavior). Applying a range of validation approaches provides information for use within the technical community, to support development of a consensus approach for weld residual stress model validation.
Time-Resolved Simultaneous Measurements of Flow Field and Surface Deformation of Turbulent Channel Flow Over a Compliant Wall
Authors: Zhang Cao , Miorini Rinaldo L. , Katz Joseph
Published: November 2014

As an initial step in our effort to investigate the interaction of a turbulent channel flow with a compliant wall, this paper focuses on the measurement techniques. Two noninvasive optical techniques, namely tomographic PIV (TPIV) and Mach-Zehnder Interferometry (MZI), are integrated to simultaneously measure the time-resolved, wall-normal deformation of the compliant transparent wall and the 3D velocity field of a turbulent channel flow above it. The two systems utilize the same laser, but different cameras. The paper provides a description of the optical setup, detailed information about calibration of the MZI system, as well as sample combined 3D velocity distributions and wall deformations. The measured wall deformation can be decomposed into low frequency structure modes, and higher frequency features that appear to advect with the flow.
Using Phased Array Ultrasonic Testing in Lieu of Radiography for Acceptance of Carbon Steel Plate Welds
Authors: Moran Traci L. , Anderson Michael T. , Cinson Anthony D. , Crawford Susan L. , Prowant Matthew S. , Nove Carol A.
Published: November 2014

The Pacific Northwest National Laboratory (PNNL) is conducting studies for the U.S. Nuclear Regulatory Commission (NRC) to assess the capability, effectiveness, and reliability of ultrasonic testing (UT) as a replacement method for radiographic testing (RT) for volumetric examination of nuclear power plant (NPP) components. This particular study focused on evaluating the use of phased-array (PA) UT on carbon steel plate welds. Welding fabrication flaws included a combination of planar and volumetric types; for example, incomplete fusion, lack of penetration, cracks, porosity, and slag inclusions. The examinations were conducted using PAUT techniques applied primarily for detection and flaw type characterization. This paper will discuss the results of using PAUT in lieu of RT for detection and classification of fabrication flaws in carbon steel plate welds.
Analyses of Profile Radial-Axial Ring Rolling Process Based on Explicit Finite Element Method
Authors: Feng Zhengkun , Champliaud Henri
Published: November 2014

Profile radial-axial ring rolling is a complex bulk forming used to produce seamless rings for critical structural components in many industries, such as machinery, aeronautics, energy and automotive. The process is characterized by high nonlinearity, unsteady three-dimensional deformation, dynamic contact boundary conditions caused by the rotations of ring and rolls. In this paper, a numerical model based on explicit finite element approach is proposed to simulate and analyze the process. An expanded ring with profile section has been obtained by numerical simulations with the dynamic model based on explicit finite element method.
Fabrication and Testing of Electron Beam Welded Alloy AA2219 Aluminum Pressure Vessels for High-Pressure Hydrogen Service
Authors: Balch Dorian K. , Goods Steve H. , San Marchi Chris
Published: November 2014

Aluminum alloys offer significant advantages for hydrogen service such as low weight, improved uniformity of properties relative to forged austenitic stainless steels, and immunity to embrittlement in the presence of dry hydrogen. For these reasons aluminum alloys are now being considered for high-pressure hydrogen isotope pressure vessel applications where forged stainless steels have been the standard materials of construction for decades. In particular, alloy AA2219 is being evaluated due to its excellent weldability, microstructural stability, and good mechanical and fracture toughness properties. Prototype AA2219 pressure vessels have been fabricated and tested, including electron beam weld development, weld hardness and tensile testing prior to and after post-weld heat treatment, and burst testing. The design, manufacture, and testing of AA2219 pressure vessels will be discussed, including an ongoing long-term shelf storage program where pressure vessels are loaded with gaseous hydrogen at pressure of 103 MPa (85% of the burst pressure for these vessels).
The Underlying Driving Forces of Multiple-Modal Statistical Behavior
Authors: Wei Zhigang , Harlow D. Gary , Nikbin Kamran
Published: November 2014

Multiple-modal statistical distributions, which are caused by multiple failure mechanisms and modes, have been observed in several materials for several types of physical entities such as micro-crack size and cycles to failure under fatigue loading. However, the underlying damage mechanisms related to these entities are still not well understood, and the associated modeling is still lacking. In this paper, the possible underlying driving forces of the multiple-modal distribution functions are investigated based on the concept of crack or damage evolution.
Implementation of the ASME Nondestructive Examination and Quality Control Central Qualification and Certification Program Standard ANDE-1-2013
Authors: Mullins Lawrence E.
Published: November 2014

Implementation and sustained support of this central certification program for nondestructive examination and quality control personnel under the auspices of ASME requires coordination between ASME as the certification body, codes and standards, regulators, training organizations and employers. This paper discusses factors critical to ANDE implementation.
Analytical Model of Nuclear Environmental Effects With Piezoelectric Wafer Active Sensors
Authors: Lin Bin , Yu Lingyu , Giurgiutiu Victor , Gresil Matthieu , Mendez Torres Adrian E.
Published: November 2014

The increasing number, size, and complexity of nuclear facilities deployed worldwide are increasing the need to maintain readiness and develop innovative sensing materials to monitor important to safety structures (ITS) for pipe and vessels (PVP) application. For example, nuclear dry cask storage system (DCSS) is a safety-critical facility in need of monitoring over prolonged periods of time. Technologies for the diagnosis and prognosis of PVP systems can improve verification of the health of the structure that can eventually reduce the likelihood of inadvertently failure of a component.

The past two decades have witnessed an extensive sensor technology development using permanently installed piezoelectric wafer active sensors (PWAS) for structural health monitoring (SHM). PWAS have emerged as one of the major SHM technologies developed particularly for generating and receiving acousto-ultrasonic waves for the purpose of continuous monitoring and diagnosis. Durability and survivability of PWAS under nuclear environmental exposures has been tested preliminarily. However, the analytical model of PWAS based sensor and sensing system has not been developed with adequate solutions and guideline. This paper presents a study on an analytical model of nuclear environmental effects with PWAS. Environmental variability of a Nuclear-SHM system includes changes in both the sensors and the sensing methodology including acoustic emission (AE), guided ultrasonic waves (GUW), and electro-mechanical impedance spectroscopy (EMIS). We considered the environmental variability considers the effects of temperature changes and radiation. We superposed these changes on the analytical models and determined how much the structural sensing signals change is due to these environment effects for the DCSS system. The analytical modeling of various structural sensing methods to environmental disturbances was studied and the potential of PWAS as irradiation sensors for PVP applications was explored. The paper ends with conclusions and suggestions for further work.
Using Explicit Finite Element Analysis to Simulate the Structural Damage Associated With an Internal Detonation in a Heat Exchanger
Authors: Prueter Phillip E.
Published: November 2014

Developing the realistic blast loading associated with an internal detonation occurring within a pressure vessel or heat exchanger is challenging. Unlike evaluation of external blast loading on structures due to far-field explosions, where typical overpressure-time histories can be reasonably defined based on empirical data, investigating confined detonations presents additional complications. The subsequent impulsive peak reflected overpressure from confined detonations acting on a structure can be extremely high due to the close proximity of the blast source to the vessel wall or pressure boundary. This establishes the possibility of significant structural damage for process equipment subjected to an internal detonation, even for relatively modest amounts of concentrated explosive products.

This paper discusses the underlying theory of blast analysis and examines the practical application of non-linear, finite element based, explicit computational techniques for simulating the load acting on a structure due to internal and external blasts. The investigation of a recent, real-life industry failure of a heat exchanger due to a suspected internal detonation is discussed. Explicit, three-dimensional blast analysis is performed on the heat exchanger in question, and an internal detonation is simulated to reasonably replicate the considerable damage actually observed in the field. This analysis permits the determination of an approximate amount of concentrated product that caused the accidental explosion; that is, the plausible equivalent amount of explosives is back-calculated based on the predicted damage to the finite element model of the equipment in question. Computational iterations of varying charge amounts are performed and the predicted amount of permanent damage is documented so sensitivity to the hypothesized charge amount can be quantified. Furthermore, explicit blast analysis of nearby equipment is performed.

In this investigation, computational results for both the heat exchanger (subjected to internal blast loading) and surrounding equipment (subjected to external blast loading) are in good agreement with the measured plastic deformations and failure modes that were actually observed in the field. Commentary on the likely detonation event that caused the significant damage observed is provided. Additionally, an advanced finite element failure criterion that is driven by plastic yielding is employed where portions of the computational model are removed from the simulation once a user-defined strain threshold is reached. This approach facilitates simulation of the gross heat exchanger pressure boundary failure actually observed in this case. The explicit finite element based analyses discussed in this study reasonably predict the structural response and damage characteristics corresponding to a recent, real-life industry failure.
Mechanical Study on Fixed Tubesheet Based on Finite Element Analysis
Authors: Yu Hongjie , Xiong Aobo , Qian Caifu , Mackenzie Donald , Zhou Xingguo
Published: November 2014

Mechanical study on a fixed tubesheet which are welded with tube bundles and equipment shell using finite element method is performed. Effects of number of tubes on the strength of tubesheet are studied. Variation of the distributions and magnitudes of the stress and deflection of the tubesheet with the size of the unpierced part of the tubesheet are investigated. Results show with support of tubes, the tubesheet does not behave as a flat solid plate in terms of the stress and deflection distribution features. Specifically, If the tubesheet is partly supported with the tubes in the center, the largest stress intensity occurs at the point which depends on the size of the unpierced region. The maximum deflection is near the unpierced region.
Creep Analysis and Constraint Effect in a Center-Cracked Plate Under Biaxial Loading
Authors: Wang Zhongxian , Zhang Yan-qing , Lam Poh-Sang , Chao Yuh J.
Published: November 2014

Typical pressure vessels are subject to biaxial loading. Creep analysis was conducted with two-dimensional finite element method for a center-cracked plate under a range of biaxial loading ratios (λ = −1, 0, and 0.5). The effects of crack size and the biaxial loading ratio on the crack tip field are reported. In addition, based on a two-parameter fracture theory, C(t)−A2(t), where C is a contour integral and is path-independent when the steady state creep is reached (denoted by C*), and A2 is a time dependent crack tip constraint parameter. The crack tip stress field calculated from the C(t)−A2(t) theory is shown to be more accurate than the Hutchinson–Rice–Rosengren (HRR) singularity solution, especially in the case of λ = 0.5. The loading level appears to have little effects on the constraint parameter A2(t). As creep time increases, the creep zone (based on the equivalent creep strain) increases rapidly but the yield zone (with respect to a reference stress) decreases. Meanwhile, the crack tip constraint is increasing with creep time, particularly for the small cracks. It was also found that the normalized relationship between the contour integral C(t)/C* and the creep time t/tT (where tT is the characteristic time for transition from small-scale creep to extensive creep) is insensitive to the biaxial loading. Therefore, the relationship previously provided for uniaxial loading can be used for biaxial loading.
A Statistical-Based Fatigue Crack Initiation Model for Axial Flaws in Zr-Nb Pressure Tubes
Authors: Liu Cheng , Scarth Douglas , Douchant Alain
Published: November 2014

Flaws found during in-service inspection of CANDU Zr-2.5Nb pressure tubes include fuel bundle scratches, debris fretting flaws, fuel bundle bearing pad fretting flaws, mechanical damage flaws and crevice corrosion marks. The CSA Standard N285.8 contains procedures and acceptance criteria for evaluation of the structural integrity of CANDU Zr-2.5Nb pressure tubes containing flaws. One of the requirements is to evaluate the flaws for fatigue crack initiation. There was a need to develop a statistical-based model of fatigue crack initiation at flaws for use in deterministic and probabilistic assessments of Zr-2.5Nb pressure tubes. A number of fatigue crack initiation experiments have been performed on notched specimens from irradiated and unirradiated Zr-2.5Nb pressure tube material with a range of hydrogen equivalent concentrations. These experiments were performed in an air environment and included temperature and load rise time as test parameters. The test data has been used to develop a statistical-based model of fatigue crack initiation at flaws that covers the effects of flaw root radius, load rise time and irradiation. This paper describes the development of the statistical-based model.
Development of an Engineering-Based Hydrogen-Assisted Fatigue Crack Growth Design Methodology for Code Implementation
Authors: Amaro Robert L. , Drexler Elizabeth S. , Slifka Andrew J.
Published: November 2014

A primary barrier to the widespread use of gaseous hydrogen as an energy carrier is the creation of a hydrogen-specific transportation network. Research performed at the National Institute of Standards and Technology, in conjunction with the U.S. Department of transportation and ASME committee B31.12 (Hydrogen Piping and Pipelines), has resulted in a phenomenological model to predict fatigue crack growth of API pipeline steels cyclically loaded in high-pressure gaseous hydrogen. The full model predicts hydrogen-assisted (HA) fatigue crack growth (FCG) as a function of applied load and hydrogen pressure. Implementation of the model into an engineering format is crucial for the realization of safe, cost-effective pipelines for the nation’s hydrogen infrastructure. Working closely with ASME B31.12, two simplified iterations of the model have been created for an engineering-based code implementation. The engineering-based iterations are detailed here and the benefits of both are discussed. A case study is then presented detailing the use of both versions. The work is concluded with a discussion of the potential impact that model implementation would have upon future hydrogen pipeline installations.
Extending Periodic Leakage Rate Testing of 9977 Packages With Elastomeric O-Rings
Authors: Han Zenghu , Shah Vikram N. , Liu Yung Y.
Published: November 2014

According to ANSI N14.5, the periodic leakage rate testing of Type B radioactive material transportation packages is performed within 12 months prior to each shipment. The purpose of performing periodic leakage rate testing is to confirm that packages built to an approved design can perform their containment function as required after a period of use. However, certain transportation packages, e.g., Model 9975 and 9977 Type B packages, have been used for interim storage for a period > 12 months, and it is desirable to extend the periodic leakage rate testing interval to reduce personnel radiation exposure and cost. Long-term leak performance tests on O-ring test fixtures have been conducted at 200°F (366K) and higher temperatures since 2004 for the purpose of interim storage of 9975 packages. The test data are adopted and evaluated in this paper by using the Arrhenius function and the Weibull statistics to establish the basis for extending the periodic leakage rate testing interval. The results show that the testing interval can be extended to 5 and 2 years for Model 9977 packages with Viton® GLT and GLT-S elastomeric O-rings (Parker Seals V0835-75 and VM835-75), respectively, if the O-ring service temperature is kept below 200°F (366K) and verified with continuous temperature monitoring.
Local vs. Global Ratcheting in Cracked Structures
Authors: Adibi-Asl R. , Reinhardt Wolf
Published: November 2014

The classical approaches in shakedown analysis are based on the assumption that the stresses are eventually within the elastic range of the material everywhere in a component (elastic shakedown). Therefore, these approaches are not very useful to predict the ratcheting limit (ratchet limit) of a cracked component/structure in which the magnitude of stress locally exceeds the elastic range at any load, although in reality the configuration will certainly permit plastic shakedown. The Non-Cyclic Method (NCM) has been proposed recently to determine both the elastic and the plastic ratchet boundary of a component or structure under cyclic loading by generalizing the static shakedown theorem (Melan’s theorem). The proposed method is based on decomposing the loading into mean (time invariant) and fully reversed components. When a cracked structure is subjected to cyclic loading, the crack and its vicinity behave differently (local) than the rest of the structure (global). The crack may propagate during the application of cyclic loading. This will affect both local and global behavior of the cracked structure.

This paper investigates global and local ratcheting of the cracked structures using the NCM and fracture mechanic parameters.
Skirt Splice Methods for Tall Pressure Vessel Towers
Authors: Seipp Trevor G. , Morrison Shawn W. , Avery Alicia C.
Published: November 2014

The design of tall pressure vessel towers may be affected by transportation limitations on the overall length of the vessel-plus-skirt. Additionally, process considerations set minimum elevations for the pressure vessel, and plant conditions may dictate whether the vessel needs to be set on a foundation or in a structure. Occasionally, these limitations collide, resulting in a requirement for a longer skirt than can be transported. To enable transportation, the vessel skirt may need to be spliced.

There are multiple methods for which the skirt can be spliced: welded or re-welded at site, sleeve-and-bolt, double-sleeve-and-bolt, and flanged. This paper presents these various methods, and presents an overview of the different design methodologies and considerations for the flanged approach. Design considerations and evaluations necessary for the design and consideration of fabrication tolerances are presented. A case study is introduced for context.
Application of Composite Materials in High Pressure Technology
Authors: Torab Hamid , Aggarwal Mahesh C.
Published: November 2014

In recent years, the application of composite materials for high pressure technology has been on the rise. The use of composites allows reducing the weight, improving shape optimization, promoting ease of handling, and also increasing the vessel’s mechanical, impact, and corrosion behavior. This paper provides an overview of the research work conducted in recent years on application of composite materials in design and development of pressure vessels. The research work on composite materials, especially on structural health monitoring and self-healing would contribute to a continued growth of the applications of composite pressure vessels.
Numerical Determination of Stress Intensity Factors Using ABAQUS
Authors: Zhu Xian-Kui
Published: November 2014

Crack assessments for pressure vessels often need to quantify the crack driving force — stress intensity factor K with the linear-elastic fracture mechanics methods. Different numerical methods have been developed to calculate the stress intensity factors for complex cracks. Of which, four typical methods, i.e., the displacement extrapolation method, the virtual crack closure technique (VCCT), the J-integral conversion method, and the direct K output method are selected and evaluated in this paper using the finite element analysis (FEA) and ABAQUS software. The evaluations are performed based on the benchmark FEA calculations in the linear-elastic conditions for the central-cracked panel (CCP) specimen in the two-dimensional (2D) plane strain conditions. The “best method” is then determined and used to calculate the stress intensity factor for the CCP specimen with a through-thickness crack in the three-dimensional (3D) conditions. The results show that ABAQUS can simply determine very accurate K values for both 2D and 3D cracks.
The Damage Development and Failure Description Under Multiaxial Creep of Materials Used in Power Plant
Authors: Chang Yuan , Xu Hong
Published: November 2014

With the increasing of the operation parameters, structural components in power plant are suffering from elevated temperatures and pressures, which are high enough for creep to occur. This may lead to failure and fracture in components. Over the past several decades, considerable efforts have been made to gain a fundamental understanding of the creep mechanism. Much attention has been paid to life prediction to ensure safety and reliability in plants. Based on the Norton-Bailey and Kachanov-Rabotnov constitutive models, a modified model was proposed to be able to describe the whole three stages of creep. Numerical calculations with the modified constitutive model were performed to simulate the damage development of both uniaxial and notched specimens. The emphasis was laid on the effect of notch dimensions and stress on the damage development. The results show a good agreement with the experiment data, and the notch dimensions and stress have remarkable effect on the creep behavior and damage development.
Other Factors Besides Anti-Seize That Affect Stud/Bolt Breakout and Assembly Torque (K-Factor)
Authors: Johnson Keith , Sidhu Aman
Published: November 2014

This paper presents information about break out torque and several key elements to consider when specifying joint and disassembly procedures. These key elements include: (1) hardened washer material used, (2) penetrant selection for disassembly, and (3) penetrant application method. This paper also presents experimental K-factor data, including variation recorded from several hardened washer configurations and information from additional K-factor testing.
Design of an Experimental Apparatus to Measure the Thermal Accommodation Coefficient Between Stainless Steel Surfaces and Rarefied Helium
Authors: Green Rachel , Manzo Ernesto T. , Nacer Mustafa Hadj , Greiner Miles
Published: November 2014

The objective of this work is to design an experimental apparatus that can acquire data to benchmark rarefied gas heat transfer simulations, and determine the thermal accommodation coefficient at the interface between the solid surfaces and the gas. The design consists of an aluminum cylinder with an electric heater at its centerline, and within a stainless-steel sheath, centered inside a cylindrical pressure vessel whose temperature is controlled using an external water jacket. There is 0.47-cm-wide helium-filled gap between the inner cylinder and vessel wall. For a given heat generation rate, the temperature difference across this gap will increase as the gas pressure decreases due to ratification. Thermocouples will be bonded to the vessel’s outer surface, and the inner surface of the sheath that surrounds the heated aluminum cylinder. Two, two-dimensional computational meshes of the apparatus (one cross sectional and the other cross sectional is offset) and one three-dimensional computational mesh are constructed. These models include heat generation within the electric heater, conduction within the solid and gas-filled regions, and radiation heat transfer across the gas, and rarefied gas thermal resistances at the solid/gas interfaces. These simulations show that the difference between the thermocouple temperatures and the surfaces of the helium filled gap are small compared to the temperature across the gap. This will allow this apparatus design to be used to effectively benchmark the ANSYS/Fluent simulations, and determine the thermal accommodation coefficient.
Coupling Vibration Investigation of Cyclone Separator Interacted With Unsteady Fluid
Authors: Li Qiang , Xu Weiwei , Wang Jianjun , Jin Youhai , Guo Ying , Wang Ying
Published: November 2014

Gas-structure coupling vibration is one kind of vibration caused by air pulsation. This coupling vibration causes widespread damage and deformation of three-stage cyclone separator used in Residue Fluid Catalytic Cracking (RFCC). After theoretically analyzing the mechanism of the generation of the gas-structure coupling vibration, the numerical simulation of three-dimensional swirling flow the cyclone separator was performed by using Reynolds Stress Model (RSM). The results showed the existence of processing vortex core (PVC) in the cyclone separator. The PVC phenomenon and motion of PVC were described in detail. Furthermore, the amplitude and frequency of gas fluctuation in the PVC region at different axial positions were quantitatively analyzed. The simulation results agreed with the experimental results of Laser Doppler Velocimetry (LDV). Finally, considering the characteristics of transient torsional pendulum of PVC in cyclone separator, the fluid-solid coupling dynamic characteristics of three-stage cyclone separator were analyzed by the finite element method, which provides references for the structure optimization design of new type cyclone separator.
Development of Simplified Empirical Phase Transformation Model for Use in Welding Residual Stress Simulations
Authors: O’Meara Nicholas , Francis John A. , Smith Simon D. , Withers Philip J.
Published: November 2014

The level and distribution of residual stresses in welds arises from the complex thermo-mechanical history of heat flow and thermal expansion at very high temperatures. It is not possible to make assessments of these with the methods that are used to determine service stresses. Simulation techniques have been developed over many years making it increasingly possible to predict residual stresses. These models need accurate materials data including, where applicable, the effect of phase transformations. In nuclear reactor pressure vessel welds, it is necessary to consider welding as a metallurgical problem as well as a thermo-mechanical one and FE simulations of these require a wide range of material data in order to create suitable input parameters.

It is crucial that models of ferritic steel welds simulate the effects of phase transformations because the different phases have different thermal expansion coefficients. Partly due to differences in thermal expansion coefficient attributed to the different phases, but more significantly because of the associated transformation strain and transformation plasticity. Further to this, predicting the distribution of the phase fractions enables structural simulations to account for the distribution of mechanical properties throughout a weld. In this work, a simplified approach to producing an empirical model to simulate phase transformations in SA-508 Gr3 pressure vessel steel is presented. A commercial finite element package is used to implement the model which calculates the volume fraction of bainite, martensite and austenite and the thermal strains that evolve over the thermal excursions. The results of these FE simulations are compared to experimental data.
Seismic Probabilistic Risk Assessment of Nuclear Power Plants Using Response-Based Fragility Curves
Authors: Shen Ying-Hsiu , Huang Yin-Nan , Yu Ching-Ching
Published: November 2014

Seismic probabilistic risk assessment (SPRA) has been widely used to compute the frequencies of core damage and release of radiation of a nuclear power plant (NPP). In 2011, Huang et al. (2011a, 2011b) published a SPRA methodology with the following characteristics different from the widely used Zion method: (a) seismic fragility curves are defined as a function of structural response parameters, such as floor spectral acceleration and story drift; (b) nonlinear response-history analysis is used to estimate statistical distributions of seismic demands for structural and non-structural components of NPPs; (c) Monte Carlo simulation is used to determine damage states of structural and non-structural components. In the study presented in this paper, the seismic risk of a sample NPP was evaluated using the methodology of Huang et al. (2011a, 2011b). The seismic risk was quantified using the annual frequency of unacceptable performance defined by a sample accident sequence for a sample NPP. The values of seismic risk computed using the methodology of Huang et al. (2011a, 2011b) and Boolean Algebra were compared to evaluate the accuracy and efficiency of the methodology of Huang et al. (2011a, 2011b). The two procedures generate similar risk values and the methodology of Huang et al. (2011a, 2011b) is more efficient than the procedure using Boolean Algebra.
Impact of resist shrinkage on the template release process in nanoimprint lithography
Authors: Tochino Takamitsu , Shiotsu Takahiro , Uemura Kimiaki , Yasuda Masaaki , Kawata Hiroaki , Hirai Yoshihiko
Published: November 2014

Template release in nanoimprint lithography was computationally studied. The impact of resist shrinkage on template release load is described. The resist shrinkage affects the state of the boundary status between resist and template, and is a factor that influences whether the resist adheres to or separates from the template. When the resist fully adheres to the template, the release load increases due to residual stress as the residual layer becomes thinner. This is because compressive stress at the residual layer is induced by resist shrinkage in the pattern cavity. In addition, the release load increases when the resist partially adheres to the template, a consequence of the decrease in interfacial area. This is because the decrement of interface area due to concentration of stress.
Profiling the Training Practices and Performance of Elite Rowers
Authors: Tran Jacqueline , Rice Anthony J. , Main Luana C. , Gastin Paul B.
Published: November 2014

Purpose:

To investigate changes in physiology, performance, and training practices of elite Australian rowers over 6 mo.

Methods:

Twenty-one elite rowers (14 male, 7 female) were monitored throughout 2 phases: phase 1 (specific preparation) and phase 2 (domestic competition). Incremental tests and rowing-ergometer time trials over 100, 500, 2000, and 6000 m were conducted at the start of the season, midseason, and late season. Weekly external (frequency, duration, distance rowed) and internal (T2minute method) loads are reported.

Results:

Heavyweight male rowers achieved moderate improvements in VO2max and power at VO2max. Most other changes in physiology and performance were small or unclear. External loads decreased from phase 1 to phase 2 (duration 19.3 to 18.0 h/wk, distance rowed 140 to 125 km/wk, respectively). Conversely, internal loads increased (phase 1 = 19.0 T2hours, phase 2 = 20.3 T2hours). Low-intensity training predominated (~80% of training hours at T1 and T2), and high-intensity training was greater in phase 2. Training was rowing-focused (68% of training duration), although 32% of training time was spent in nonspecific modes. The distribution of specificity was not different between phases.

Conclusion:

Physiology and performance results were stable over the 6-mo period. Training-load patterns differed depending on the measure, highlighting the importance of monitoring both external and internal loads. The distribution of intensity was somewhat polarized, and substantial volumes of nonspecific training were undertaken. Experimental studies should investigate the effects of different distributions of intensity and specificity on rowing performance.
Sensitivity of the Yo-Yo Intermittent Recovery Test and Cardiac Autonomic Responses to Training in Futsal Players
Authors: de Freitas Victor H. , Pereira Lucas A. , de Souza Eberton A. , Leicht Anthony S. , Bertollo Maurizio , Nakamura Fábio Y.
Published: November 2014

Purpose:

This study examined the sensitivity of maximal (Yo-Yo Intermittent Recovery [IR] 1 and 2) and submaximal (5’-5’) tests to identify training adaptations in futsal players along with the suitability of heart-rate (HR) and HR-variability (HRV) measures to identify these adaptations.

Methods:

Eleven male professional futsal players were assessed before (pretraining) and after (posttraining) a 5-wk period. Assessments included 5’-5’ and Yo-Yo IR1 and IR2 performances and HR and HRV at rest and during the IR and 5’-5’ tests. Magnitude-based-inference analyses examined the differences between pre- and posttraining, while relationships between changes in variables were determined via correlation.

Results:

Posttraining, Yo-Yo IR1 performance likely increased while Yo-Yo IR2 performance almost certainly increased. Submaximal HR during the Yo-Yo IR1 and Yo-Yo IR2 almost certainly and likely, respectively, decreased with training. HR during the 5’-5’ was very likely decreased, while HRV at rest and during the 5’-5’ was likely increased after training. Changes in both Yo-Yo IR performances were negatively correlated with changes in HR during the Yo-Yo IR1 test and positively correlated with the change in HRV during the 5’-5’.

Conclusions:

The current study has identified the Yo-Yo IR2 as more responsive for monitoring training-induced changes of futsal players than the Yo-Yo IR1. Changes in submaximal HR during the Yo-Yo IR and HRV during the 5’-5’ were highly sensitive to changes in maximal performance and are recommended for monitoring training. The 5’-5’ was recommended as a time-efficient method to assess training adaptations for futsal players.