bluuebunny/crossref_metadata_2025_split huggingface dataset:
Finite Element Verification of Engineering Equations for Prediction of Structural Strength of Annulus Spacers in CANDU Nuclear Reactors
Authors: Doddihal Preeti , Kawa Dennis , Scarth Douglas , Chen Yu 
Published: November 2019

Abstract
The core of a CANDU (CANada Deuterium Uranium) pressurized heavy water reactor includes several hundred horizontal fuel channels that pass through a calandria vessel containing the heavy water moderator. In each fuel channel, annulus spacers are used to maintain the gap between the cold calandria tube and the hot pressure tube, a pressurized vessel containing the nuclear fuel in contact with heavy water coolant. In order to carry the loads between the pressure tube and calandria tube, the annulus spacers are required to possess adequate structural strength throughout the operating life of the reactor. The Inconel X-750 spacers used in some reactor units are susceptible to irradiation induced degradation. As irradiation fluence increases with operating time, material embrittlement has been observed due to helium bubble formation in the X-750 spacer material. An engineering approach for assessing the structural strength of CANDU annulus spacers has been recently developed. When the ductility of the material is relatively low, the region susceptible to fracture under applied tensile stress may be adequately idealized as a strip-yield process zone surrounded by elastic material and associated with restraining stress. The engineering approach is based on applying the strip-yield process zone methodology to fracture at a nominally smooth surface. Finite element modeling was undertaken to simulate the strip-yield based fracture process zone. The finite element analyses and results are presented in this paper. The finite element results verify the engineering equations developed to assess the structural strength of annulus spacers.
A Method to Estimate Deformation Strains in the Context of Coke Drum Life Assessments: Part 1
Authors: Huang John , Subramanian Kannan , Boster Patrick , Bedoya Julian J. 
Published: November 2019

Abstract
In this paper, an analytical method to estimate the deformation strains that can quantify the severity of bulges, as it applies to coke drums, is presented. The proposed method is based on classical shell theory and API 579-1/ASME FFS-1 (2016) procedures involving triaxiality limits. In this first part of the work, only the theoretical development is presented along with the comparison of the results from this theoretical approach with two case studies that emulate the bulging due to different loading scenarios. The developed approach is then applied to a deformed coke drum. In the next part of this paper, the application of this approach on selected in-service coke drums that are equipped with strain gages will be presented. The authors would like to emphasize the well-known fact that the coke drum is a complex pressure vessel for which any single simplified assessment technique may not be sufficient to quantify the life or fitness-for-service (FFS) of a coke drum due to the complexities associated with the various parameters that affect the mechanical integrity of the coke drum. This paper is an attempt to advance the assessment techniques that are currently utilized in the industry.
The Design and Analysis of a Containment Vacuum and Pressure Vessel System
Authors: Bernardin John , Hathcoat David , Sattler David , Spernjak Dusan , Swensen Erik , Llobet Megias Anna 
Published: November 2019

Abstract
A nested confinement (inner) and containment (outer) vessel system is under development to conduct small shock-physics experiments in a high-speed proton imaging facility at Los Alamos National Laboratory. The dual vessel system is necessary to serve as a qualified confinement system and containment buffer boundary between a high explosives experiment and the environment.
The paper describes the preliminary engineering design and analyses that have been performed on the outer containment pressure vessel, following ASME BPVC Sect. VIII Div. 1, for both pressure and vacuum conditions. Other engineering attributes which will be presented include an internal support structure for a nested inner vessel, an external integrated support and alignment structure for the complete vessel system, and the vacuum and gas handling equipment.
Method B Fatigue Screening in ASME BPV Code, Section VIII, Division 2, Part 5
Authors: Kirkpatrick Kenneth , Johnson Christopher R. , Mann J. Adin 
Published: November 2019

Abstract
ASME Boiler and Pressure Vessel Code (BPVC), Section VIII, Division 2, Part 5 Method B fatigue screening is intended to be a quick and simple method that is sufficiently conservative to screen components in cyclic service thus not requiring detailed fatigue analysis. The method assesses pressure, thermal, and mechanical loads separately. The basis for each portion of the method is discussed along with an alternative bases for the assessments. Each assessment is reformulated as a fatigue damage factor and all variables are provided so that the intent of each equation is clearly identifiable. A penalty factor will be included in each equation rather than assuming one penalty for all designs, the reformulation creates penalty for non-fatigue resistant designs and reduces the penalty for fatigue resistant designs. Examples are given showing the potentially non-conservative results if a summed damage is not used.
Experimental Determination of the Ratcheting of the Porosity for the Study of Ductile Rupture Under Cyclic Loading Conditions
Authors: Remmal Al Mahdi , Marie Stéphane , Leblond Jean-Baptiste 
Published: November 2019

Abstract
It is known that for ductile porous materials, cyclic loadings lead to lower fracture strains than monotone ones. This reduction of ductility probably arises from an effect called “ratcheting of the porosity” that consists of a continued increase of the mean porosity during each cycle with the number of cycles. Finite element based micromechanical simulations confirmed this interpretation. Recently the authors proposed a Gurson-type “layer model” better fit that Gurson’s original one which does not predict the ratcheting of the porosity, for the description of the ductile behavior under cyclic loading conditions. A very good agreement was obtained between the results of the micromechanical simulations and the model predictions for a rigid-hardenable material. Yet, the ratcheting of the porosity is a consequence of both hardening and elasticity; and the theory of sequential limit analysis used in order to get the “layer model” is strictly applicable in the absence of elasticity. Based on an expression of the porosity rate accounting for elasticity, a proposal was made to improve the new model with regard to elasticity. Simultaneously to this theoretical work, an experimental program was conducted on a model material in order to assess experimentally this new model. The material is a HIPed 316L stainless steel, with Al2O3 almost spherical inclusions acting like porosities, complying with the hypothesis made to derive the theoretical model. Notched tensile specimens, with a center section of 4mm, were cyclically loaded. Several tomographies were performed at ESRF, using a 120 keV beamline and 3x3 microns detector, in order to prove experimentally the ratcheting effect of the porosity. The void growth through the cycles is precisely described and the experimental results could then be processed and compared to the numerical porosities predictions of the model. This paper presents the experimental activity of this PhD program.
Recent Developments in the R5 Procedures for Assessing the High Temperature Response of Structures
Authors: Hughes Daniel G. J. , Chevalier Marc , Dean David W. 
Published: November 2019

Abstract
The R5 procedures have been developed within the UK power generation industry to assess the integrity of nuclear and conventional plant operating at high temperatures. Within R5, there are specific procedures for assessing creep-fatigue crack initiation in initially defect-free components (Volume 2/3), components containing defects (Volume 4/5), dissimilar metal weldments (Volume 6) and similar metal ferritic weldments under steady loading (Volume 7).
A key driver for continued developments in the R5 Procedure is the operational feedback from thirty years of operation of the UK Advanced Gas-Cooled Reactor (AGR) fleet. This experience from operation of the UK AGR fleet can be used to inform the design and operation of future high temperature reactors. Some of the lessons learnt from long-term operation of austenitic stainless steels at high temperatures are detailed briefly within this paper.
Further, this paper briefly outlines the current R5 procedures and then focuses on two significant recent developments in these procedures: treatment of carburisation and its impact on creep-fatigue crack initiation and improved methods for predicting creep-fatigue crack growth under combined primary and secondary loads.
Impact of the Harsh Environment on E-Glass Epoxy Composite
Authors: Idrisi Amir Hussain , Ismail Mourad Abdel-Hamid , Abdel-Magid Beckry , Mozumder Mohammad , Afifi Yaser 
Published: November 2019

Abstract
Composite materials are being used in many industrial applications such as automobile, aerospace, marine, oil and gas industries due to their high strength to weight ratio. The long-term effect of sustained loads and environmental factors that include exposure to UV light, temperature, and moisture have been under investigation by many researchers. The major objective of this study is to evaluate the effects of harsh environment (e.g. seawater and high temperature) on the structural properties of E-glass epoxy composite materials. These effects were studied in terms of seawater absorption, permeation of salt and contaminants, chemical and physical bonds at the interface and degradation in mechanical properties. Samples were immersed in seawater at room temperature (23°C), 65°C and 90°C for the duration of 6 months. Results show that seawater absorption increased with immersion time at 23°C and 65°C, whereas the weight of the specimens decreased at 90°C. The moisture causes swelling at 23°C and 65°C and breakdown of chemical bonds between fiber and matrix at 90°C. It is observed that high temperature accelerates the degradation of the E-glass epoxy composite. At 90°C, the tensile strength of E-glass epoxy sharply decreased by 72.92% but no significant change was observed in modulus of elasticity of the composite.
Modeling of Cracked Pipe System: Effect of Boundary Conditions on Displacement-Controlled and Load-Controlled Leak-Before-Break
Authors: Uddin M. , Wilkowski G. , Kurth E. , Hill L. , Bagnoli K. 
Published: November 2019

Abstract
In recent years, there has been a growing interest of using Leak-Before-Break (LBB) concept in the refining industry. LBB methodology has been applied in the nuclear industry for decades, but generally for elimination of hardware for dynamic rupture control at the design stage. However, in the refining industry the purpose of the LBB application could be quite different than for the nuclear industry. In the refining industry the purpose of LBB is to show in-service leakage can be detected well ahead the potential for rupture allowing for ample time for safe replacement of piping.
This paper explores conditions in which LBB can be applied to refinery piping. Initially, the analysis was conducted using a finite element model of a typical pipe system with its design boundary conditions under operating loadings, i.e., gravity, pressure, thermal and hanger loadings. The results with various circumferential crack sizes show a displacement-controlled manner (LBB is easy to satisfy) for the pipe system mainly due to higher secondary stresses, i.e., thermal loadings. However, the pipe system behaved in a load-controlled manner (LBB is harder to satisfy) when some of the boundary conditions were changed simulating a possible support failure and/or hanger failure. This paper investigates how boundary conditions can change a displacement-controlled LBB behavior to load-controlled LBB for a representative pipe system and the implications regarding leak rate detection capability. The effect of material’s toughness reduction due to high-temperature hydrogen-attack (HTHA) damage was also included in these analyses. The procedure outlined here can be applied to a piping system to identify piping supports that are critical for inspection to demonstrate LBB, and the anticipated leak rate before reaching critical flaw size.
Inspection Optimization Justification for PWR Main Steam and Feedwater Nozzles Using Probabilistic Fracture Mechanics
Authors: Lohse C. , Shim D. J. , Somasundaram D. , Grizzi R. , Stevens G. L. , Cinson T. 
Published: November 2019

Abstract
Pressurized water reactor (PWR) steam generator (SG) main steam and feedwater nozzles are classified as ASME Code, Section XI, Class 2, Category C-B, pressure retaining welds in pressure vessels. Current ASME Code requirements specify that the nozzle-to-shell welds (Item No. C2.21 & C2.32) and nozzle inner radius sections (Item C2.22) are to be examined very 10 years. An evaluation was performed to establish a technical basis for optimized inspection frequencies for these items. The work included a review of inspection history and results, a survey of components in the PWR fleet (which included both U.S. and overseas plants), selection of representative main steam and feedwater nozzle configurations and operating transients for stress analysis, evaluation of potential degradation mechanisms, and flaw tolerance evaluations consisting of probabilistic and deterministic fracture mechanics analyses. The results of multiple inspection scenarios and sensitivity studies were compared to the U.S. Nuclear Regulatory Commission (NRC) safety goal of 10−6 failures per year.
Does the Biaxial Loading Affect the Apparent Fracture Toughness (Kc)?
Authors: Chen Chentong , Xiao Hanbin , Chao Yuh J. , Lam Poh-Sang 
Published: November 2019

Abstract
From linear elastic fracture mechanics (LEFM), it is well accepted that only the singular stress near the crack tip contributes to the fracture event through the crack tip stress intensity factor K. In the biaxial loading, the stress component that adds to the T-stress at the crack tip, affects only the second term in the Williams’ series solution around the crack tip. Therefore, it is generally believed that biaxial load does not change the apparent fracture toughness or the critical stress intensity factor (Kc). This paper revisited several specimen geometries under biaxial loading with finite element method. The sources of discrepancy between the theory and the test data were identified. It was found that the ideal biaxial loading would not be achieved for typical fracture specimens with finite geometry. Comparison to available test data shows that, while the biaxial load could affect the apparent fracture toughness, the contribution is relatively small.
A Novel Approach to Account for Weld Residual Stresses in Pressure Vessel Flaw Assessments
Authors: Brust F. W. , Hill L. , Wilkowski G. , Hioe Y. , Bagnoli K. 
Published: November 2019

Abstract
A periodic inspection of a reactor pressure vessel in refinery was scheduled. Prior to that inspection, criteria need to be established to determine what flaw indication would be tolerable so that the vessel can safely be put back in to service in a timely manner, or in the worst case, identify what flaw indication would create a very strong case for repair or replacement criteria for the vessel. A flaw tolerance criterion that can be applied to the refinery inspection process was developed for numerous potential flaw locations in this vessel. The finite element alternating method was used to determine the appropriate fracture parameters to assist in this flaw assessment procedure. These computational efforts involved examining the fracture response of the system in preparation for planned inspections.
Stress intensity factors were evaluated for a total of ten (10) cracks inserted into the refinery pressure vessel at several locations and crack orientations. Most of the cracks had depth to thickness ratios of 0.25 and a half width 3 times this depth. The crack sizes are chosen based on the assumed maximum initial flaw sizes expected to be found from NDI. The stress intensity factor for residual stress loading was conservatively estimated by placing a unit tensile pressure on the crack face for all 10 cracks. The approximation of crack face pressure loading to simulate residual stress is also shown to be accurate. Therefore, one can estimate the contribution to stress intensity factor by multiplying the residual stress value of K by the estimated residual stress ratio. The final estimate of crack driving force for a crack, KI, is obtained by adding the contributions of the pressure loading with the residual stress contribution. Internal pressure loading of this vessel is the only significant source of loading in this vessel.
An Optimized Start-Up Mode of Tower Solar Turbines With Heat Transfer Coefficient Model Based on Experiment Data
Authors: Xiaoxiao Li , Gang Chen , Peng Wang 
Published: November 2019

Abstract
Lifetime assessment of steam turbine components has become more and more important for the past years. Tower solar turbines experience a greater number of start-ups than those operating in base-load plants and high levels of thermal stress occurs during fast start-up, which both have a significant impact on lifetime. To achieve the fastest start-up time without reducing the lifetime of solar turbine it is essential to fully understand the thermal behavior of the turbine components during start-up. A series of experiments have been carried on a combined cycle steam turbine. The operation mode and inlet parameters of experiment unit are similar to tower solar turbine, so the new thermal model of heat transfer coefficient based on these experiment data can be used for the start-up research of tower solar turbine. A Finite Element (FE) turbine model is created and analyzed with the new thermal model in many start-up cases such as warm start, hot start to seek for an optimized start-up mode.
Fractography Study of the Mixed Mode Fatigue Crack Growth Process in Pressure Vessel P355NL1 Steel
Authors: Lesiuk Grzegorz , Correia Jose A. F. O. , Smolnicki Michał , Błażejewski Wojciech , El Amine Ben Seghier Mohamed , Jesus Abilio , Calcada R. A. B. 
Published: November 2019

Abstract
The aim of the paper is to present a fatigue crack growth analysis thru a fractography study of different crack paths obtained in different operating conditions of the pressure vessel P355NL1 steel. All experiments were performed on CTS (Compact Tension Shear) specimens under the mixed mode (I+II) loading conditions. These stress states aim to reflect simple biaxiality stress states in a pressurized cylinder. In the experiments, different operating conditions were considered. Two different kinetic fatigue fracture diagrams were proposed for mixed mode fatigue crack growth rate estimation. The obtained results suggested a fact that energy approach describes synonymously the kinetics of fatigue crack growth under mixed mode loading conditions with respect to the mean stress effect – R-ratio. Finally, the fractography analysis sugessted that the fatigue fracture surface topography changes with the mixity level.
Implementing B31J-2017 SIF and Flexibility Factor Changes for B31 Piping Systems
Authors: Paulin Anthony W. , Carpenter Lorna , Becht Charles 
Published: November 2019

Abstract
This paper discusses when new SIF and k-Factors from ASME B31J-2017 should be used for operating and new piping systems. Screening guidelines are provided to help plant owners know when current operating facilities may be subject to through-wall leaks as they approach given life milestones. The paper also shows when these same guidelines can be used in new system designs to require the use of more applicable SIF data, of qualified vendor lists and additional inspections.
Assessing small airway disease in GLI versus NHANES III based spirometry using area under the expiratory flow-volume curve
Authors: Ioachimescu Octavian C , Stoller James K 
Published: November 2019

BackgroundSpirometry interpretation is influenced by the predictive equations defining lower limit of normal (LLN), while ‘distal’ expiratory flows such as forced expiratory flow at 50% FVC (FEF50) are important functional parameters for diagnosing small airway disease (SAD). Area under expiratory flow-volume curve (AEX) or its approximations have been proposed as supplemental spirometric assessment tools. We compare here the performance of AEX in differentiating between normal, obstruction, restriction, mixed defects and SAD, as defined by Global Lung Initiative (GLI) or National Health and Nutrition Examination Survey (NHANES) III reference values, and using various predictive equations for FEF50.MethodsWe analysed 15 308 spirometry-lung volume tests. Using GLI versus NHANES III LLNs, and diagnosing SAD by the eight most common equation sets for forced expiratory flow at 50% of vital capacity lower limits of normal (FEF50 LLN), we assessed the degree of diagnostic concordance and the ability of AEX to differentiate between various definition-dependent patterns.ResultsConcordance rates between NHANES III and GLI-based classifications were 93.7%, 78.6%, 86.8%, 88.0%, 93.8% and 98.8% in those without, with mild, moderate, moderately severe, severe and very severe obstruction, respectively (agreement coefficient 0.81 (0.80–0.82)). The prevalence of SAD was 0.6%–6.9% of the cohort, depending on the definition used. The AEX differentiated well between normal, obstruction, restriction, mixed pattern and SAD, as defined by most equations.ConclusionsIf the SAD diagnosis is established by using mean FEF50 LLNor a set number of predictive equations, AEX is able to differentiate well between various spirometric patterns. Using the most common predictive equations (NHANES III and GLI), the diagnostic concordance for functional type and obstruction severity is high.
Growth differentiation factor 11 attenuates liver fibrosis via expansion of liver progenitor cells
Authors: Dai Zhen , Song Guangqi , Balakrishnan Asha , Yang Taihua , Yuan Qinggong , Möbus Selina , Weiss Anna-Carina , Bentler Martin , Zhu Jimin , Jiang Xuemei , Shen Xizhong , Bantel Heike , Jaeckel Elmar , Kispert Andreas , Vogel Arndt , Saborowski Anna , Büning Hildegard , Manns Michael , Cantz Tobias , Ott Michael , Sharma Amar Deep 
Published: November 2019

ObjectiveLiver fibrosis and cirrhosis resulting from chronic liver injury represent a major healthcare burden worldwide. Growth differentiation factor (GDF) 11 has been recently investigated for its role in rejuvenation of ageing organs, but its role in chronic liver diseases has remained unknown. Here, we investigated the expression and function of GDF11 in liver fibrosis, a common feature of most chronic liver diseases.DesignWe analysed the expression of GDF11 in patients with liver fibrosis, in a mouse model of liver fibrosis and in hepatic stellate cells (HSCs) as well as in other liver cell types. The functional relevance of GDF11 in toxin-induced and cholestasis-induced mouse models of liver fibrosis was examined by in vivo modulation ofGdf11expression using adeno-associated virus (AAV) vectors. The effect of GDF11 on leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5)+ liver progenitor cells was studied in mouse and human liver organoid culture. Furthermore, in vivo depletion of LGR5+ cells was induced by injecting AAV vectors expressing diptheria toxin A under the transcriptional control ofLgr5promoter.ResultsWe showed that the expression of GDF11 is upregulated in patients with liver fibrosis and in experimentally induced murine liver fibrosis models. Furthermore, we found that therapeutic application of GDF11 mounts a protective response against fibrosis by increasing the number of LGR5+ progenitor cells in the liver.ConclusionCollectively, our findings uncover a protective role of GDF11 during liver fibrosis and suggest a potential application of GDF11 for the treatment of chronic liver disease.