bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aerodynamic Analysis of a Wind Turbine With Elevated Inflow Turbulence and Wake Using Harmonic Method
Authors: Win Naung Shine , Rahmati Mohammad , Farokhi Hamed 
Published: November 2019

Abstract
This paper presents aerodynamic simulation and analysis of a horizontal axis wind turbine using Computational Fluid Dynamics (CFD) method. The MEXICO (Model Rotor Experiments In Controlled Conditions) Experiment wind turbine is selected for simulation as the experimental data are available and can be used for validation of the CFD model used. CFD method has been used by a number of studies to predict aerodynamic behaviour of wind turbines. However, the majority of studies consider a steady wind flow at the inlet. Sometimes this is not the case when the wind flow is not steady or there are other wind turbines nearby. In this paper, the steady simulations are first conducted using different turbulence models without considering inflow wake at the inlet. Afterwards, a harmonic wake is generated at the inlet and unsteady CFD simulation is performed. Unsteady CFD simulation usually requires long runtime and therefore harmonic (frequency domain) method, which is an efficient computational method to study unsteady periodic flow at a computational cost in the order of steady-state solutions, is used for unsteady computation in this study. This paper first discusses the pressure coefficient distributions with and without harmonic wake at the inlet and compares them against the experiment. Afterwards the detailed analysis of flow around the blade subject to the unsteady harmonic wake is conducted in the meridional view and the blade-to-blade view. Next, the effect of pressure distribution on the blade structure is briefly discussed. Finally this paper concludes based on the results from the aerodynamic analysis as well as the analysis of the effect of aerodynamic loads on the blade structure.
Numerical Simulation of Damaged Ship’s Motion in Beam Waves
Authors: Wang Qing , Chen Xuanshu , Liu Liwei , Wang Xianzhou , Liu MingJing 
Published: November 2019

Abstract
The dangerous situation caused by the breakage of the ship will pose a serious threat to crew and ship safety. If the ship’s liquid cargo or fuel leaks, it will cause serious damage to the marine environment. If damage occurs accompanied by roll and other motions, it may cause more dangerous consequences. It is an important issue to study the damaged ship in time-domain. In this paper, the motions of the damaged DTMB 5512 in calm water and regular beam waves are studied numerically. The ship motions are analyzed through CFD methods, which are acknowledged as a reliable approach to simulate and analyze these complex physical phenomena. An in-house CFD (computational fluid dynamics) code HUST-Ship (Hydrodynamic Unsteady Simulation Technology for Ship) is used for solving RANS equations coupled with six degrees of freedom (6DOF) solid body motion equations. RANS equations discretized by finite difference method and solved by PISO algorithm. Level set was used for free surface simulation. The dynamic behavior of model was observed in both intact and damaged condition. The heave, roll and pitch amplitudes of the damaged ship were studied in calm water and beam wave of three wavelengths.
Research of Wind Resistance and Flow Field of Container Ship
Authors: Sun Zhiyuan , Li Ping , Sun Hanbing 
Published: November 2019

Abstract
In order to study the super large container ship characteristics of the wind resistance coefficient and the air flow field in the different angle of attack, wind tunnel test based on the 14000 containers ship is carried out on the state of the design draft. The wind resistance coefficient of superstructure is obtained through test. The CFD (Computational Fluid Dynamics) technology is introduced to simulate the wind resistance and yaw moment of the model. The numerical results are basically in agreement with the experimental data. The results indicates that with the increase of the wind direction angle, the longitudinal wind resistance coefficient curve shows a “sine curve” rule and exists opposite resistance extremums, whereas the lateral wind resistance coefficient curve presents a parabolic change rule. Numerical simulation method is proved has high accuracy for wind resistance prediction of container ship. The size of wind load on the ship is related to the form and size of the wake region.
Fatigue Behavior of Large, Rolled-After Heat-Treatment and Hot-Dip Galvanized HT Bolts
Authors: Unglaub Julian , Thiele Klaus 
Published: November 2019

Abstract
As a subproject in the framework of the DFG Research Training Group “Graduiertenkolleg 2075 - Modelling the constitutive evolution of building materials and structures with respect to aging” (GRK 2075), the fatigue behavior of rolled-after heat-treatment and hot-dipped galvanized HT-bolts is examined. Results of fatigue tests of M48x255 10.9 and M36x235 10.9 HT-bolts from different states of manufacturing processes (rolled-after heat-treatment, rolled-after heat-treatment and hot-dip galvanized) will be presented and discussed. If rolled-after heat-treatment HT-bolts are hot-dip galvanized, the fatigue life is significantly reduced. However, it is beyond the fatigue life of rolled-before heat-treatment HT-bolts and hot-dip galvanized HT-bolts.
Sweeplus®: An Integrated Solution to Pipe Vibration Failures
Authors: Liu Yuqing , Diwakar Philip , El Jaouhari Ismat , Lin Dan 
Published: November 2019

Abstract
This paper discusses our efforts to develop a robust branch fitting that can withstand AIV related to higher sound power levels than a standard contour fitting and accommodate FIV related vibration loads, without compromising project cost and schedule. Numerical simulation results and experimental test data are presented to substantiate our claims that a sweeplus® performs much better than any other contoured branch fittings available in the market with respect to any AIV, AR and FIV related risks. The aerodynamically shaped new fitting can withstand higher sound power level (PWL) limits in AIV, has smoother curvature to reduce flow separation, vortex formation and shedding thereby lowering peak stress concentrations and avoiding AR and FIV related risk, has an extended fatigue life, while adhering to ASME B16.9 Code requirements.
Thermal Analysis of the 9975 Package Used for Long Term Nuclear Material Storage
Authors: Tamburello David , Kesterson Matthew , Hensel Steven 
Published: November 2019

Abstract
The 9975 is a double containment shipping package used to transport plutonium bearing materials for the US Department of Energy. The 9975 is also used for long term storage of plutonium bearing materials at the Savannah River Site. The package utilizes a fiberboard overpack to protect against fire and impact events. The 9975 has been shown to maintain containment during a hypothetical facility accident fire even though the facility fire is hotter and longer than the regulatory transportation fire. Fiberboard aging and degradation has been investigated using both laboratory and field surveillance data. This information is used to evaluate an aged 9975 used for nuclear material storage. Variations in fiberboard thermal properties due to aging were shown to have modest effects on the maximum component temperatures, while the package geometry variations due to aging and degradation have a larger effect on the maximum component temperatures. Specifically, the air gap between the upper fiberboard assembly and the drum lid increases during storage due to the deterioration of the lower fiberboard assembly and slumping of the package containment vessel. A limiting air gap distance has been determined via thermal fire analysis, which may be used to estimate a storage life.
A Novel Methodology to Optimize the Tightening Sequence in Bolted Flange Joints
Authors: Zhu Linbo , Bouzid Abdel-Hakim , Hong Jun 
Published: November 2019

Abstract
Bolted flange joints are the most complex structural components of pressure vessels and piping equipment. Their assembly is a delicate task that determines their successful operation during the service life. During bolt tightening, it is very difficult to achieve uniformity of the target bolt preload due to elastic interaction and criss-cross talk. The risk of leakage failure under service loading is consequently increased because of the scatter of the bolt preload.
In previous work, an analytical model based on the theory of circular beams on linear elastic foundation was proposed to predict the bolt tension change due to elastic interaction. Based on this model, this paper presents a novel methodology for the optimization of the tightening sequence. The target preload and the load to be applied to each bolt in each pass can be calculated to achieve uniform final preload and avoid bolt tension reaching yield under a number of specified tightening passes. The validity of the approach is supported by experimental tests conducted on a NPS 4 class 900 welding neck flange joint and by finite element analysis on this bolted joint using the criss-cross tightening and sequential patterns. This study provides guidelines for bolted flange joints assembly and enhances its safety and reliability by minimizing bolt tension scatter due to elastic interaction.
Fatigue Performance of Welded Joints Under Variable Amplitude Loading Spectra
Authors: Liu Xu , Zhang Yan-Hui , Wang Bin 
Published: November 2019

Abstract
Offshore pipelines are generally subjected to variable amplitude (VA) loading in service due to waves or ocean currents. Welded joints often represent the most critical locations for fatigue cracking. Use of the current fatigue design guidance, for example, BS 7608, to assess fatigue performance of the welded joints in such structure may lead to inaccurate estimates depending on the nature of the VA loading spectrum. Further studies on the effect of VA loading spectra on fatigue performance of welded joints are needed. In this research, both uniaxial and 3-point bending fatigue tests were performed on non-load carrying fillet welded plates under VA loading spectra to investigate the effects of mean stress and the type of VA loading spectra. The influence of plate thickness was also investigated. Test results suggest that the spectrum with a high constant maximum tensile stress (cycling-down) could significantly degrade fatigue performance of welded joints, with the damage parameter D only at around 0.5. The severity of this type of loading spectrum depends on the mean stress level and the plate thickness. An analytical model has been developed to predict fatigue crack propagation (FCP) by considering the interaction of stresses in the loading spectrum. The model considers the impact of the mean stress generated by the preceding load on FCP in the subsequent cycles. FCP predicted by the model shows a good agreement with the experimental data.
Determination of Pipeline Yielding Occurred in Hydrostatic Pressure Testing
Authors: Zhu Xian-Kui 
Published: November 2019

Abstract
The pipeline industry has traditionally utilized the “double stroke” concept to define line pipe yielding for limiting plastic deformation of the pipeline during hydrostatic pressure testing. Practice showed that double stroke may define a nominal yield point lying between the elastic limit and the offset yield strength. Recently, a set of field hydrostatic tests were conducted on an X70 pipeline at Enterprise Products, and the test pressure at double stroke was as high as 129% of SMYS, but the von Mises stress was less than the actual yield strength. The entire pipeline was thought in the elastic conditions at double stroke during the hydrostatic testing.
It is well recognized that the classical Tresca and von Mises yield criteria determines a lower and an upper bound of the limit load at yielding, and a newly proposed Zhu-Leis yield criterion determines a medium result of the two classical solutions. Extensive full-scale tests have confirmed that the Zhu-Leis yield solution is the best prediction of experimental data on average. This paper attempts to use the more accurate Zhu-Leis yield criterion to reanalyze the real-world hydrostatic tests of the X70 pipeline to see if pipe yielding occurs and to determine pipe diameter expansion at double stroke during the hydrostatic pressure testing.
Lower Tail Estimation of Fatigue Life
Authors: Harlow D. Gary 
Published: November 2019

Abstract
Uncertainty in the prediction of lower tail fatigue life behavior is a combination of many causes, some of which are aleatoric and some of which are systemic. The error cannot be entirely eliminated or quantified due to microstructural variability, manufacturing processing, approximate scientific modeling, and experimental inconsistencies. The effect of uncertainty is exacerbated for extreme value estimation for fatigue life distributions because by necessity those events are rare. In addition, typically, there is a sparsity of data in the region of smaller stress levels in stress–life testing where the lives are considerably longer, extending to giga cycles for some applications. Furthermore, there is often over an order of magnitude difference in the fatigue lives in that region of the stress–life graph. Consequently, extreme value estimation is problematic using traditional analyses. Thus, uncertainty must be statistically characterized and appropriately managed. The primary purpose of this paper is to propose an empirically based methodology for estimating the lower tail behavior of fatigue life cumulative distribution functions, given the applied stress. The methodology incorporates available fatigue life data using a statistical transformation to estimate lower tail behavior at much smaller probabilities than can be estimated by traditional approaches. To assess the validity of the proposed methodology confidence bounds will be estimated for the stress–life data. The development of the methodology and its subsequent validation will be illustrated using extensive fatigue life data for 2024–T4 aluminum alloy specimens readily available in the open literature.
A Simplified Thermal Load Evaluation Method for Localized Lug Stresses Beyond Sec. III Appendix-Y
Authors: Matsumiya Tsubasa , Garcia-Rodriguez Daniel , Nebu Akira , Takamura Noriyuki 
Published: November 2019

Abstract
In this work an evaluation method for local thermal stresses on class 1 piping due to U-shaped lugs is presented.
First, a three-dimensional finite element analysis (3D-FEA) is used to perform a thermal transient evaluation, obtaining the time-dependent temperature distribution of a realistic range of pipe-lug systems. These results are then used as an input for both a structural 3D-FEA and the corresponding thermal stress term in Non-Mandatory Appendix Y [1]. It was seen that the formula in Appendix-Y cannot account for the thermal stresses obtained through the detailed FEA evaluation.
A parameter study using a simplified two-dimensional (2D) FEA approach, shows that the localized thermal stresses due to lugs are significantly affected by: (1) pipe-to-lug thickness ratio, (2) distance between adjacent lugs, and (3) lug height. A set of correction coefficients depending on these parameters is therefore proposed.
When applying the proposed correction coefficients to the Appendix Y method, adequately conservative (when compared with 3D FEA results) stresses can be obtained. Since these correction coefficients can be obtained from simple geometric considerations, the proposed method successfully accounts for the complex lug-to-lug interaction while retaining the simplicity of the original Appendix Y approach.
Coke Drum Bottom Head Flange Design Optimisation
Authors: Berry Alex , Brown Warren , Seijas Antonio , Cook Sarah 
Published: November 2019

Abstract
Bottom head flange leaks on coke drums are a too common occurrence for coke drum operators. This paper discusses why these complex joints leak, exploring phenomena such as bolt relaxation, flange rotation, bolt hole cracking, plastic deformation of a flange face due to cyclic thermal transients, as well as investigating the effects of gasket stress variation which can lead to gasket movement and distortion during successive drum cycles. The industry trend is to install automatic bottom un-heading devices (BUDs) to facilitate safe, reliable coke removal and to increase production through shortening un-heading operations. A case study is reviewed which shows how a new drum flange, coupled to a BUD, has been optimized using Finite Element Analysis (FEA). The findings show adequate flange thickness and optimized hub dimensions are required to combat plastic deformation of the flange ring and reduce gasket stress variation. Five designs are modelled, varying the flange thickness, outside diameter and hub geometry. Due to the close proximity of a new side nozzle, the full lower section of the drum has been modelled using quarter and half symmetry FEA with applied temperature distributions from each phase of a typical coke drum cycle; heating, coking and quench. This has allowed for nozzle loadings to be evaluated and the location of the flange weld to be optimized to give the greatest fatigue life. An explanation into why periodic re-tightening is required to keep these joints tight is provided along with recommendations on suitable joint assembly techniques using a combination of bolt load verification and alternative bolting patterns from ASME PCC-1.
Experimental Investigation of the Flow-Induced Vibrations of a Rod Cluster Control Assembly Inside Guides With Enlarged Gaps
Authors: Moussou Pierre , Fichet Vincent , Pastur Luc , Duhamel Constance , Tampango Yannick 
Published: November 2019

Abstract
In order to better understand the mechanisms of fretting wear damage of guide cards in some Pressurized Water Reactor (PWR) Nuclear Power Plant (NPP), an experimental investigation is undertaken at the Magaly facility in Le Creusot. The test rig consists of a complete Rod Cluster with eleven Guide Cards, submitted to axial flow inside a water tunnel. In order to mimic the effect of fretting wear, the four lower guide cards have enlarged gaps, so that the Control Rods are free to oscillate. The test rig is operated at ambient temperature and pressure, and Plexiglas walls can be arranged along its upper part, and a series of camera records the vibrations of the control rods above and below the guide cards. The vertical flow velocity is in the range of a few m/s. Beam-like pinned-pinned modes at about 5 Hz are observed, and oscillations of several mm of the central rods are measured, which come along with impacts at the higher flow velocities. A simple non-linear calculation reveals that the main effect of the impacts between Control Rods and Guide Cards is an increase of the natural frequency of the rods by about 10%. Furthermore, as the vibration spectra collapse remarkably well with the flow velocity, the experiments prove that turbulent forcing is responsible for the large oscillations of the control rods, no other mechanism being involved.
A Local Approach to Assess Temperature Effects on Fracture Toughness Incorporating the Measured Distribution of Microcracks
Authors: Ruggieri Claudio , Jivkov Andrey P. 
Published: November 2019

Abstract
This work describes a local approach to cleavage fracture (LAF) incorporating the statistics of microcracks to characterize the cleavage fracture toughness distribution in structural steels. Fracture toughness testing conducted on standard compact tension C(T) specimens for a 22NiMoCr37 pressure vessel steel provides the cleavage fracture resistance data needed to determine the measured toughness distribution. Metallographic examination of etched surfaces for the tested steel also provides the distribution of carbides, which are assumed as the Griffith fracture-initiating particles, dispersed in the material from which the cleavage fracture toughness distribution is predicted. Overall, the analyses conducted in the present work show that LAFs incorporating the statistics of microcracks are a viable engineering procedure to describe the dependence of fracture toughness on temperature in the DBT region for ferritic steels.
Development of a New Austenitic Stainless Steel (Low-C-18Cr-11Ni-3Cu-Mo-Nb-B-N) With High Sensitization Resistance and High Temperature Strength
Authors: Suzuki Yuhei , Aota Shogo , Dan Etsuo , Ueyama Masaki , Osuki Takahiro , Ono Toshihide , Otaki Nao , Okada Hirokazu 
Published: November 2019

Abstract
Austenitic materials with high sensitization resistance and high temperature strength are required for furnace and reaction tower of desulfurizing plants in the petroleum refinery industry. For these requirements, a new steel (LowC-18Cr-11Ni-3Cu-Mo-Nb-B-N) has been developed. The steel shows no intergranular stress corrosion cracking in polythionic acid environment after aging in the temperature range from 565 to 700 °C for up to 10,000 hours. This excellent PTA-SCC resistance is attributed to the prevention of M23C6 carbide precipitation along grain boundary due to extra low carbon content with high ratio of niobium to carbon. The maximum allowable tensile stress of this steel is estimated to be more than 30% higher than that of ASME SA213 Type347H. This excellent strength is based on the precipitation strengthening effect due to fine precipitates of a copper rich phase which are coherent with the austenite matrix in addition to Z-phase (NbCrN). Moreover, boron addition improves creep strength and creep ductility of the steel.
From these results, it is concluded that the newly developed steel is a promising material not only for refinery processes but also for other elevated temperature usages.
Analysis of Detection Quality for Ultrasonic Guided Wave With L(0,2) and T(0,1) in the Pressure Pipe
Authors: Liu Shu-Hong , Ding Ju , Tang Chen-huai , Song Pan , Tang Deng-chao , Zhang Ye , Yang Yu-qing 
Published: November 2019

Abstract
Torsion mode and longitudinal mode are used primarily in ultrasonic guided wave inspection, especially L (0, 2) mode and T (0, 1) mode. There are some differences between them, like excitation method, mode of particle vibration, inspection ability and impact factor. So, it is very important to select the appropriate mode between L (0,2) and T(0,1). In this paper, the detection ability of two guided wave modes are compared and analyzed with regard to four aspects in the pipe: fluid, liquid level, defects, the angle between defect and wave propagation direction. The experimental results show that L (0,2) mode is more suitable for defect detection in pressure pipe than T (0,1) mode, but L (0,2) mode is more sensitive to fluid in a pipe. This paper provides a basis for selecting the mode of guided waves in ultrasonic detection.