bluuebunny/crossref_metadata_2025_split huggingface dataset:
Singing Mitigation in Corrugated Tubes With Liquid Injection
Authors: Belfroid S. P. C. , Golliard J. , Vijlbrief O. 
Published: January 2014

Pipes with a corrugated inner surface, as used in flexible pipes for gas production and transport, can generate a high amplitude tonal sound (singing). Small quantities of liquid can result in a significant amplitude reduction or total mitigation of this sound production. To evaluate different potential mechanisms, liquid injection tests were done in both a horizontal and vertical small scale (49 mm) setup including high speed camera recordings using a transparent corrugated section.
The singing amplitude decreased linearly with the liquid injection rate for both orientations, although the effect in the vertical setup was even faster. Liquid injection resulted also in higher onset velocities.
The video recordings showed partially filled corrugations. For horizontal corrugations, liquid crept upward in the corrugations. In the vertical test, liquid accumulated at the upward edge with intermitted liquid spill over to downstream corrugations. The liquid fill up did not change significantly with higher liquid loads. Taking the fill-up grade and additional damping into account, a match could be made between the measured singing amplitude and a predicted singing amplitude as function of liquid rate. However, no model has been found to predict the liquid fill-up yet.
Experimental and Numerical Investigation of Pressurized Pipe Elbows Under Strong Cyclic Loading
Authors: Varelis George E. , Ferino Jan , Karamanos Spyros A. , Lucci Antonio , Demofonti Giuseppe 
Published: January 2014

The present work examines the behavior of pipe elbows subjected to strong cyclic in-plane bending loading in the presence of internal pressure. In the first part of this work the experimental procedure is presented in detail. The tests are conducted in a constant amplitude displacement-controlled mode resulting to failures in the low-cycle fatigue range. The overall behavior of each tested specimen, as well as the evolution and concentration of local strains are monitored throughout the testing procedure. Different internal pressure levels are used in order to examine their effect on the fatigue life of the specimens.
The above experimental investigation is supported by rigorous finite element analysis. Using detailed dimensional measurements and material testing obtained prior to specimen testing, detailed numerical models are developed to simulate the conducted experiments. An advanced cyclic plasticity material model is employed for the simulation of the tests. Emphasis is given on the local strain development at the critical part of the elbow where cracking occurs. Finally, the results of the present investigation are compared with available design provisions in terms of both ultimate capacity and low-cycle fatigue.
Numerical and Experimental Testing of Composite Rings for Reciprocating Compressor Valves
Authors: Annicchiarico Claudio , Babbini Alberto , Capitani Renzo , Tozzi Pierluigi 
Published: January 2014

Valves are one of the most critical class of components for the reliability of reciprocating compressors. Many failures of reciprocating compressor valves are due to valve ring failure. Investigating the failure mode of rings is complicated because of the ring composite material properties, which randomly and locally range from orthotropic to anisotropic due to the random disposition of the reinforcement, usually consisting of short fibers.
In this paper, a cooperation between GE Oil & Gas and the University of Florence, the results of a numerical simulation campaign will be presented, along with its correlation with the experimental evidence arising from a purpose-built test rig. This work guided the design of a new material for rings, whose characteristics have been tailored based on the results of this experimental and numerical campaign.
Mesh Convergence Studies for Thick Shell Elements Developed by the ASME Special Working Group on Computational Modeling
Authors: Molitoris David P. , Bjorkman Gordon S. , Tso Chi-Fung , Yaksh Michael 
Published: January 2014

The ASME Special Working Group on Computational Modeling for Explicit Dynamics was founded in August 2008 for the purpose of creating a quantitative guidance document for the development of finite element models used to analyze energy-limited events using explicit dynamics software. This document will be referenced in the ASME Code Section III, Division 3 and the next revision of NRC Regulatory Guide 7.6 as a means by which the quality of a finite element model may be judged. One portion of the document will be devoted to a series of element convergence studies that can aid designers in establishing the mesh refinement requirements necessary to achieve accurate results for a variety of different element types in regions of high plastic strain. These convergence studies will also aid reviewers in evaluating the quality of a finite element model and the apparent accuracy of its results.
In this paper, the authors present the results of a convergence study for an impulsively loaded propped cantilever beam constructed of LS-DYNA thick shell elements using both reduced and selectively reduced integration. A large load is applied to produce large deformations and large plastic strains in the beam. The deformation and plastic strain results are then compared to similar results obtained using thin shell elements and hexahedral elements for the beam mesh.
Reduction of Stack Vortex Induced Vibrations
Authors: McGuffie Sean M. , Porter Michael A. 
Published: January 2014

A stack installation experienced vortex-induced vibrations (VIV) while in-service. The magnitude of the vibrations was severe enough that cracking in the welds at the stack bases was experienced shortly after their installation. Initially, straight strakes were placed on the stacks, based on field serviceability, per API 560. The strakes proved ineffective and it was determined that the stacks would be uninstalled for repair. During the repair process, design steps were required to reduce or eliminate the VIV experienced in-service. Due to a flaw in the initial design and the ineffectiveness of the straight strake solution, the end client required verification of any proposed design changes before their implementation. Additionally, little time was allotted for the investigation of solutions.
Tuned mass dampers were initially explored for the design modification. It was determined that they could not be constructed of materials suitable for the environmental operational characteristics of the stacks. It was then agreed that aerodynamic modifications of the stacks should be explored to reduce VIV. ASME STS I specifies the design and installation of helical strakes on stacks, but does not indicate the magnitude of vibration reduction that can be expected [3]. Therefore, numerical models were used to determine if the strakes would reduce or eliminate the service vibration.
A baseline analysis was first conducted to validate that the tools — a combination of computational fluid dynamics (CFD) and finite element (FE) methods — could capture the in-service behavior. To perform this analysis a CFD model was constructed of the as-built stack. Using DES methods, this model was analyzed at several wind speeds to determine the magnitude and frequency content of the VIV-forcing functions. This information was then used to perform a dynamic analysis using an FE model of the stack. This model accurately predicted the correct wind speed corresponding to VIV and the amplitude of the stack’s vibration. A second model was then constructed of a stack with helical strakes, using a novel modeling methodology. This model was analyzed over a variety of wind speeds using DES methodologies. The forcing functions predicted with the helical strake model were then used to determine the stack’s in-service response. This paper contains the complete methodologies and results associated with these analyses.
Design Considerations: Torque or Tension — Advantages and Disadvantages
Authors: Noble Robert 
Published: January 2014

To seal effectively gasketed bolted flanged joints require the application of bolt load in a controlled manner. There are two main methods of achieving this — application of bolt load by controlled torque and application of bolt load by controlled tension.
The paper considers the practical merits and limitations of each technique under criteria including:
Practicality, accuracy, scatter, bolt load or stress, bolt material, bolt length, tool access limitations, cost of tooling, time, safety and ease of understanding.
The paper does not seek to recommend one technique over the other but rather to give the joint designer, specifier or tool selector a set of guidelines to ensure the most effective and practical technique is chosen for each joint being designed.
Following the recommendations in the paper will allow a designer to recommend a technique that will deliver the best results for the joint based on the principle that long term integrity is more important that short term gain.
An Evaluation of the Protection Against Local Failure in ASME Section VIII, Division 2: Finite Element Model Considerations
Authors: Seipp Trevor G. 
Published: January 2014

The local failure criteria was a relatively new inclusion in the 2007 Edition of ASME Section VIII, Division 2. The elastic-plastic evaluation criteria for this failure mechanism was brand new to the Code. This failure mechanism introduced to the Code the concept of local strain limits based on the triaxial state of stress.
In implementing the evaluation of this failure mechanism, an interesting phenomenon was discovered. The triaxiality was to be calculated “everywhere” in the model, and used to create a limiting strain to be compared to the plastic strain at the point where said triaxiality was calculated.
As is well known, in the finite element method, stresses and strains are calculated at the Gauss Points, and extrapolated to the nodes. This uses the element shape function. One question that arises is: if the triaxiality is calculated at the Gauss Points, can it be extrapolated to the nodes using the same element shape functions? Another question that arises is: can the extrapolated values of stress and strain be adequately used to calculate the triaxiality at the nodes?
This paper discusses the validity of both approaches, and introduces a third option: a material property called Ductile Damage Initiation Criteria, and provides and example that demonstrate all three methods. Recommendations are provided about the best approach to be implemented.
Severe Accident Condition Modeling in PWR Environment: Creep Rupture Modeling
Authors: Brust Frederick W. , Iyengar R. , Benson M. , Rathbun Howard 
Published: January 2014

A problem of interest in the nuclear power industry involves the response of pressurized water reactor (PWR) pressure boundary components under long-term station blackout (SBO) conditions. SBO is a particularly challenging event to nuclear safety, since all alternating current power required for core cooling is lost. If unmitigated, such a scenario will eventually lead to the reactor core being uncovered. Thermal-hydraulic (T-H), computational fluid dynamics, and structural combined creep/plasticity analyses of this scenario have been conducted and are presented here.
In this severe accident scenario, high temperatures can occur, and impart this thermal energy to the surrounding structures, including the reactor vessel, nozzles, reactor coolant system (RCS) hot leg piping and S/G tubes. At such high temperatures and pressures, creep rupture of RCS piping and/or steam generator (S/G) tubes becomes possible. The intent of this paper is to present a finite element based analysis model that can be used to evaluate the time to failure of the nozzle-weld-pipe configuration.
Modeling of Weld Residual Plastic Strain and Stress in Dissimilar Metal Butt Weld in Nuclear Reactors
Authors: Qiao Dongxiao , Feng Zhili , Zhang Wei , Wang Yanli , Crooker Paul 
Published: January 2014

Primary water stress corrosion cracking (PWSCC) constitutes a major safety challenge for dissimilar metal welds (DMW) in pressurized water reactors. The reliability of structure integrity assessment of DMW is strongly dependent on the reliable determination of the weld residual stress (WRS) field, which is one of the primary driving forces for PWSCC. Recent studies have shown that today’s WRS models have varying degrees of success in determining the WRS in DMW that is highly dependent upon the strain-hardening models used in WRS simulation. The commonly used strain hardening model in WRS modeling (isotropic, kinematic, and mixed ones) appear to be inadequate in that they neglect the high-temperature time-dependent (viscous) deformation process during welding.
This work presents a new strain-hardening model derived from specially designed experiment that mimics the thermal-mechanical deformation process of a SS304L stainless steel under rapid heating and cooling conditions relevant to DMW. Compared to the time-independent strain hardening ones, the new strain hardening model, termed as Dynamic Strain Hardening model, takes into account the effect of time and temperature dependent dislocation annihilation and microstructure recrystallization processes at the elevated temperatures during welding. Moreover, a novel experimental approach based on micro-hardness testing is developed to quantify the residual equivalent plastic strain in a mock-up DMW. It is found that the new dynamic strain hardening model produces results that are more consistent with experimentally measured plastic strains and residual stresses. It is concluded that it is necessary to include the dynamic strain hardening recovery phenomenon to improve the accuracy of WRS predictions in DMW. Moreover, the newly developed micro-hardness based plastic strain measurement approach would be an effective means to quantify the plastic strain distributions which is another key factor for PWSCC in DMW in addition to the residual stresses.
Limit Loads for Circumferentially Cracked Pipes Under Combined Bending and Torsion With Tension
Authors: Ryu Ho-Wan , Han Jae-Jun , Kim Yun-Jae 
Published: January 2014

In power plants, piping installations with a circumferential crack can be operated under combined bending and torsion. ASME Boiler and Pressure Vessel code Section XI non-mandatory Appendix C provides the flaw evaluations for fully-plastic fracture using limit load criteria for the structural integrity of the cracked pipes. According to the recent version of Code, combined loading is provided only for membrane and bending. Even though actual operating conditions have torsion loading, the methodology for evaluating torsion load is not established, and assumed torsion is relatively small compared to membrane and bending and can be ignored in the evaluation.
This paper provides the results of limit load analyses by using finite element models for circumferentially cracked pipes under pure bending, pure torsion and combined bending and torsion with tension. Theoretical limit load solutions based on net-section fully-plastic criteria are compared with the results of finite element analyses. The validation of theoretical limit loads for combined bending and torsion with tension is discussed.
Comparison of J Resistance Curves From Toughness Testing Specimens With Those From Various Cracked Pipe Tests
Authors: Kim Jong-Hyun , Han Jae-Jun , Kim Yun-Jae , Shim Do-Jun 
Published: January 2014

J contour integral still has great importance to predict fracture of both small specimen and full-scaled pipes. However, it is difficult to obtain experimental J resistance curve of full-scaled pipes due to the differences of defect shape and complexity of loads. Due to the recent development of the FE damage analysis to predict fracture of full-scaled pipes, it is also possible to predict J resistance of full-scaled pipes. To use this FE damage model for fracture estimation, it is necessary to verify the validity of this model by compared with toughness testing specimens.
In this paper, J resistance curves of full-scaled pipes using FE damage analysis were compared with various toughness testing specimens from Pipe Fracture Encyclopedia performed by Battelle. And the J contour integral were calculated from FE analysis using the element-size-dependent damage model recently proposed by the authors. Compared results showed that J calculation using FE damage analysis could be used for J-estimation of full-scaled pipes by compared with fracture toughness testing specimens.
Factors Affecting Steam Generator Tube Bow
Authors: Cao Moli , Nelson Jennifer , Charkas Hasan , Wiger Timothy 
Published: January 2014

One of the challenges in straight shell-and-tube Steam Generator design is to avoid the tube to tube wear that can arise during operation due to higher than anticipated compressive tube loads and the resulting tube bow that can occur. Tube bow becomes significant when the compressive load in the tube exceeds its critical buckling capacity. This excessive load does not lead to unstable collapse of the tube as the axial load in the tube is displacement controlled. However, it does lead to significant lateral deformation for a very small increase in axial load/displacement. In this paper, several factors are investigated to determine their influence on the onset of tube bowing.
Based on the studies performed in this paper there are factors that play a significant role in the behavior of steam generator tubes that have not typically been addressed in associated design analyses. Failure to address these factors can lead to unexpected behavior, premature degradation of steam generator performance, and possibly pressure boundary failure. A thorough understanding of these factors is necessary to ensure that a given design will perform as expected.
Alternative Reference Temperature Based on Master Curve Approach in Japanese Reactor Pressure Vessel Steel
Authors: Hirota Takatoshi , Hirano Takashi , Onizawa Kunio 
Published: January 2014

Master Curve approach is the effective method to evaluate the fracture toughness of the ferritic steels accurately and statistically. The Japan Electric Association Code JEAC 4216-2011, “Test Method for Determination of Reference Temperature, To, of Ferritic Steels” was published based on the related standard ASTM E 1921-08 and the results of the investigation of the applicability of the Master Curve approach to Japanese reactor pressure vessel (RPV) steels. The reference temperature, To can be determined in accordance with this code in Japan.
In this study, using the existing fracture toughness data of Japanese RPV steels including base metals and weld metals, the method for determination of the alternative reference temperature RTTo based on Master Curve reference temperature To was statistically examined, so that RTTo has an equivalent safety margin to the conventional RTNDT. Through the statistical treatment, the alternative reference temperature RTTo was proposed as the following equation; RTTo = To + CMC + 2σTo. This method is applicable to the Japan Electric Association Code JEAC 4206, “Method of Verification Tests of the Fracture Toughness for Nuclear Power Plant Components” as an option item.
EM reconstruction of dual isotope PET using staggered injections and prompt gamma positron emitters
Authors: Andreyev Andriy , Sitek Arkadiusz , Celler Anna 
Published: January 2014

Purpose:The aim of dual isotope positron emission tomography (DIPET) is to create two separate images of two coinjected PET radiotracers. DIPET shortens the duration of the study, reduces patient discomfort, and produces perfectly coregistered images compared to the case when two radiotracers would be imaged independently (sequential PET studies). Reconstruction of data from such simultaneous acquisition of two PET radiotracers is difficult because positron decay of any isotope creates only 511 keV photons; therefore, the isotopes cannot be differentiated based on the detected energy.Methods:Recently, the authors have proposed a DIPET technique that uses a combination of radiotracer A which is a pure positron emitter (such as18F or 11C) and radiotracer B in which positron decay is accompanied by the emission of a high‐energy (HE) prompt gamma (such as 38K or 60 Cu). Events that are detected as triple coincidences of HE gammas with the corresponding two 511 keV photons allow the authors to identify the lines‐of‐response (LORs) of isotope B. These LORs are used to separate the two intertwined distributions, using a dedicated image reconstruction algorithm. In this work the authors propose a new version of the DIPET EM‐based reconstruction algorithm that allows the authors to include an additional, independent estimate of radiotracer A distribution which may be obtained if radioisotopes are administered using a staggered injections method. In this work the method is tested on simple simulations of static PET acquisitions.Results:The authors’ experiments performed using Monte‐Carlo simulations with static acquisitions demonstrate that the combined method provides better results (crosstalk errors decrease by up to 50%) than the positron‐gamma DIPET method or staggered injections alone.Conclusions:The authors demonstrate that the authors’ new EM algorithm which combines information from triple coincidences with prompt gammas and staggered injections improves the accuracy of DIPET reconstructions for static acquisitions so they reach almost the benchmark level calculated for perfectly separated tracers.
Bacterial Cellulose as a Substrate for Microbial Cell Culture
Authors: Yin Na , Santos Thiago M. A. , Auer George K. , Crooks John A. , Oliver Piercen M. , Weibel Douglas B. 
Published: January 2014

ABSTRACT

Bacterial cellulose (BC) has a range of structural and physicochemical properties that make it a particularly useful material for the culture of bacteria. We studied the growth of 14 genera of bacteria on BC substrates produced by
Acetobacter xylinum
and compared the results to growth on the commercially available biopolymers agar, gellan, and xanthan. We demonstrate that BC produces rates of bacterial cell growth that typically exceed those on the commercial biopolymers and yields cultures with higher titers of cells at stationary phase. The morphology of the cells did not change during growth on BC. The rates of nutrient diffusion in BC being higher than those in other biopolymers is likely a primary factor that leads to higher growth rates. Collectively, our results suggest that the use of BC may open new avenues in microbiology by facilitating bacterial cell culture and isolation.