bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultimate Compressive Strength of Eccentrically Loaded Stiffened Panels in Ship Structures: A Computational Study
Authors: Anyfantis Konstantinos 
Published: November 2019

Abstract
Ship scantlings are obtained through a linear elastic design framework. In relatively long ships, the mid-ship’s ultimate strength capacity must be checked whether it is below a certain level (given factor of safety). Smith’s method is based on an incremental-iterative approach where constitutive equations of idealized representative components are used to model the different involved buckling modes. The literature body neglects the local bending effect applied at the stiffener with the attached plating (considered here as the representative element). This work studies the eccentrically loaded representative element from its compressive resistance point of view. The eccentricity sources from the linear varying strain field produced as a result of pure bending of the ship’s mid-section and is relative to the location of the stiffened panel from the ship’s section Neutral Axis. Therefore, the representative element has been considered as a part of the ship’s structure and the inherent eccentricity is analytically calculated in terms of geometric and material properties. A computational study has been further performed in a non-linear finite element environment in order to figure out the effect of the eccentricity level to the ultimate compressive strength of the representative element. Geometric distortions have been also included in the FE models in order to allow for accurate strength calculations. Numerical results have shown that, in realistic proportions of large ships, the further the representative element is located from the mid-ship’s NA the smaller is the deviation from pure compressive load strength analysis results. However, for the element laying near the ship’s NA, idealized models overestimate the strength by 10% compared to realistic analytical / numerical results for the typical scantling case considered.
An Application of Fault Tree Analysis for Decommissioning of Subsea Flexible Pipeline in Brazil
Authors: Ramos Rafaela , Pasqualino Ilson , Souza Marcelo Igor L. , Nicolosi Eduardo Ribeiro 
Published: November 2019

Abstract
The decommissioning of underwater structures has expanded in recent years, as the number of facilities at the end of their useful lives is increasing and legislation becomes more severe. Unlike the production units which already have their decommissioning plans consolidated, subsea pipelines represent the greatest technological, environmental and financial challenge of this stage. Currently, there are few studies to evaluate failures in the decommissioning of flexible pipelines. In addition, these studies generally use simplified analyses. Therefore, this study aims to elaborate a failure analysis for a Reverse Reeling option, in order to contribute to the decision-making process and reduction of failures. For this, a Fault Tree Analysis will be developed followed by the subsequent elaboration of its minimum cut sets. The main results present a total of 13 first-order minimal cut set, 5 second-order minimal cut set and 7 third-order minimal cut set.
Hydrodynamic Model Tests With a Large Floating Hydrocarbon Storage Facility
Authors: Fonseca Nuno , Chi Zhang , Rodrigues José Miguel , Ren Nianxin , Hellan Øyvind , Magee Allan R. 
Published: November 2019

Abstract
The paper presents model tests with a floating hydrocarbon storage facility performed in SINTEF Ocean’s basin. The system may be considered a very large floating structure with a footprint of 300m × 310m. Hydrocarbons are stored into independent tanks, which are soft moored to a modular floating frame which is kept in station by dolphins. The system is composed of 14 tanks and 21 frame barge modules, therefore 35 connected floating bodies.
The objective of the model tests was twofold. First, to verify the feasibility of the global system, namely in terms of tank and frame motions, connection loads, station keeping loads and relative wave elevations. Second, to acquire data for tuning and validation of numerical models, i.e. to investigate effects that cannot be reliably established by simulations alone.
The model tests were performed in wave, current and wind conditions corresponding to 1 year and to 100 years return periods, in addition to a set a simplified wave conditions. The paper describes the model test setup, the experimental program, the procedures for analysis of test data, it presents representative results and discusses the main observations.
A Study on Motions and Connector Loads for a New Type of Two-Module Semi-Submersible
Authors: Ding Jun , Tian Chao , Miao Yuji , Zhang Zhengwei , Zhao Zhanhua , Ni Xinyun 
Published: November 2019

Abstract
The hydrodynamic model and three-dimensional finite element model of a new type of two-module marine platform were built for the subject of research. The motions and connector loads were predicted based on the COMPASS THAFTS software and the results were in agreement with the model tests. It shows that the new type platform has a good sea keeping performance. On the other hand, the short-term forecast results indicate that the connector loads, Fz, is larger than other two directions, approaching 200t. The connector loads, Fx and Fy, are usually in the order of magnitude of tens tons. Some useful conclusions obtained in this paper can provide an important reference for the optimal design and construction of the new type platform and its connector system.
Comparative Evaluation of Elastomer Seal Energization in Conventional and Expandable Hanger Assembly
Authors: Patel Harshkumar , Salehi Saeed 
Published: November 2019

Abstract
Elastomer seals are extensively used in various wellhead and casing/liner hanger equipment as barriers for isolating fluids. Seal assemblies have been identified as one of the major cause of well control incidents. Majority of hangers utilize conventional weight- or mechanical-set slip-and-seal assembly. The objective of this paper is to conduct detailed investigation of seal energization in conventional and relatively newer expandable type hanger seal assembly.
To achieve the objective, finite element modeling approach was employed. Three dimensional computer models consisting of concentric casings and annular elastomer seal element were constructed. Seal energization process was modelled by manipulating boundary conditions. Conventional seal energization was mimicked by applying rigid support at the bottom of elastomer element and compressing it from the top. Expandable hanger type seal energization was modelled by radially displacing the inner pipe to compress annular seal element. Seal quality was evaluated in terms of contact stress values and profile along the seal-pipe interface.
Different amount of seal energization were simulated. Both types of seal energization processes yielded different contact stress profiles. For the same amount of seal volumetric compression, contact stress profiles were compared. In case of conventional seal energization, contact stress profile decreases from the compression side towards support side. The seal in expandable hanger generates contact stress profile that peaks at the center of contact interface and reduces towards the ends. Convectional seal assembly has more moving parts, making it more prone to failure or under-energization. FEA Models were validated using analytical equations. Good match was obtained.
Majority of research related to elastomer seal is focused on material properties evaluation. Limited information is available in public domain on functional design and assessment of seal assembly. This paper adds novel information by providing detailed assessment of advantages and limitations of two different seal energization process. This opens doors for further research in functional failure modes in seal assembly.
Development of Offshore Structural Analysis Software X-SEA Coupled With FAST
Authors: Kim Ki-Du , Vachirapanyakun Sorrasak , Plodpradit Pasin , Dinh Van Nguyen , Park Jin-Ho 
Published: November 2019

Abstract
Coupled analysis of offshore structures is currently challenging. The 3D finite element analysis software X-SEA coupled with FAST 8 program is therefore developed and discussed in this paper. The current version of X-SEA includes the results of extensive research and development based on finite element program XFINAS, which was originally developed in Imperial College London. The solution of the X-SEA ranges from the simple static to highly advanced dynamic analysis applied to the offshore structures. GID is used as pre- and post processor of X-SEA. The brief theoretical background of X-SEA software is summarized. Numerical examples of offshore monopile, wind turbine jackets, pile super element and fatigue analysis verified with SACS software in terms of reactions, displacements and member forces are investigated.
“Three Sisters” Measured As a Triple Rogue Wave Group
Authors: Magnusson Anne Karin , Trulsen Karsten , Aarnes Ole Johan , Bitner-Gregersen Elzbieta M. , Malila Mika P. 
Published: November 2019

Abstract
On November 30, 2018, our attention was caught when analyzing wave profile time series measured by a platform mounted wave sensor (a SAAB REX radar) at Ekofisk, central North Sea. The 20-minute time series had not only one, but three consecutive waves with individual heights that all were more than twice the significant wave height, the two last of them being almost equally high with a factor 2.35 to the significant wave height of 4m (from 4σ(η), over 20 minutes).
Counting three rogue waves in one sequence seems to be very rare. In this study we analyze how the shape is evolving in space and time using linear and non-linear propagation methods developed by Mark Donelan [1,2] and Karsten Trulsen [3,4]. Weather conditions and characteristics of the sea state with the ‘Three Sisters’ (named the “Justine Three Sisters”) are presented. It is found that the Three Sisters occurred in a crossing sea condition, with wind sea and swell coming from directions 60 degrees apart, with about same frequency, but very different energy.
Prediction of Liquid and Gas Leak Rates in Packed Stuffing Boxes
Authors: Salah Omar Aweimer Ali , Bouzid Abdel-Hakim 
Published: November 2019

Abstract
The prediction of gas and liquid leak rate through packed stuffing boxes subjected to gas flow is a subject of very few studies in the literature. For better prediction of leakage, the change of porosity with length due to the non-uniform axial stress must be accounted for. There are few theoretical models on the prediction of leak rates in packing rings with capillary models. However, a model that incorporates the change of the capillary area with stress gives a better prediction.
In this paper, the first slip flow model is used to predict gas and liquid flow considering the straight capillaries and capillaries having an area dependent on the axial stress in the packing rings. An approach that uses an analytical-computational methodology based on the number and the size of pores obtained experimentally is adopted to predict gas and liquid leak rates in uniform and non-uniform compressed yarned packings. The Navier-Stokes equations associated with slip boundary condition at the wall are used to predict leakage. Experimental tests with helium, argon, nitrogen and air for gazes and water and kerosene for liquids will be used to validate the models. The porosity parameters characterization will be conducted experimentally with helium at a reference gas at different gland stresses and pressures.
Optimal Simplification for the Surface Process System in Oilfields
Authors: Liang Yongtu , Wang Bohong , Zheng Jianqin , Lei Tiantian , Zhang Xin , Zhang Haoran 
Published: November 2019

Abstract
Continuous development of oilfields fosters a growing need for the simplification of oilfield surface process systems (SPSs) to reduce operating and management costs. Wells, testing stations, transferring stations, and central processing facilities are the main facilities in an SPS; pipelines are used to connect these stations. In this system, production radius (PR) is an important index to determine which transferring station can a testing station be linked to. Different simplification plans will lead to different operating and management costs in the following production period. Therefore, the simplification plan should be carefully designed to minimize cost and facilitate management. This paper proposes an optimization method for the simplification of SPSs in oilfields. First, an evaluation model is developed based on fuzzy analytical hierarchy process (FAHP) to select the transferring stations that need to be decommissioned. Second, hydraulic and thermal calculations are performed to get the data for the calculation of PRs. Third, the PRs, including oil gathering radius, water flooding radius, and hot water washing radius are computed to determine the linkage between the transferring stations and the testing stations. Finally, a construction plan is obtained for new pipelines of the testing stations. A case study is conducted to verify the effectiveness of this method. The results show that this method is suitable for the simplification of SPSs in oilfields.
Burst Strength of Glass Fiber Reinforced Polyethylene Pipes With Delamination Defect
Authors: Ni Zhenlei , Shi Jianfeng , Zheng Jinyang 
Published: November 2019

Abstract
Glass fiber reinforced polyethylene pipes (GFRPs) are increasingly utilized in the oil and gas transportation industries because of their various benefits. Delamination is one of the most common defects in GFRPs during manufacturing and service, which can affect their mechanical properties. This paper focused on the influence of delamination on short-term burst strength of GFRPs. The GFRPs specimens were 100mm-inner diameter and reinforced by 12 layers of ± 55° cross winding glass fiber tapes. Firstly, artificial delamination of different widths were designed and put into the specimens. Then, the short-term burst tests were carried out. Meanwhile, finite element models were established to predict the burst pressures and the numerical results were in good agreement with that of test results. The results showed that the widths and axial locations of delamination defects had significant influence on the burst pressure and stress distribution, which could lead to a premature burst failure of GFRPs during service. The deformation of GFRPs close to the defect region was also analyzed and the failure mechanism of GFRPs containing defects was discussed in detail.
Decay of Excitation Load From Heat Recovery Steam Generators (HRSG) to Attached Piping System As a Function of Pipe Supports Locations
Authors: Appiah Emmanuel , Gawande Kshitij 
Published: November 2019

Abstract
Construction of combined cycle gas turbine (CCGT) plants, which are combination of a simple cycle gas turbine (Brayton cycle) and a steam power cycle (Rankine cycle), have increased in recent years due to their high efficiency, low emissions, relative compact size, and minimal delivery time, among other advantages. One key component of CCGT is a heat recovery steam generator (HRSG). The HRSG is basically a heat exchanger composed of a series of preheaters (economizers), evaporator, reheaters, and superheaters. Combustion gas from gas turbine is used as an energy source for steam generation in the HRSG. Due to high mass flowrate of combustion turbine exhausts gas and injection of water to reduce NOx contents, high vibration and severe noise are created. The noise induces acoustic resonance in the HRSG duct cavities. The high vibration together with the acoustic resonance creates large forces. These forces have been attributed to excitation mechanisms including fluid elastic instability, random turbulence excitation, and periodic wake shedding. Some of the forces are transmitted to the attached pipes. Integrity of the piping system to withstand the forces depends on rigid and variable pipe supports. It is therefore paramount to determine the load induced into the supports to design them adequately. The purpose of this paper is to provide relative magnitude of loads experienced at various pipe supports as a function of distance from the HRSG (load decay). This knowledge is expected to help support designers to optimize material allocation to ensure pipe system integrity at optimum cost.
Study of Thermal Distribution in the Shock Suppressors (Snubbers) due to Heat Induced by High Frequency Vibrations
Authors: Mayes Alex , Gawande Kshitij P. 
Published: November 2019

Abstract
Hydraulic shock suppressors (snubbers) are used in dynamic restraints to prevent piping systems and equipment from occasional loads such as turbine trips, sudden valve closures, and seismic events. An occasional load can be defined as an impact load where forces and moments are applied over very short periods of time. The current study is a continuation of a published study on snubbers experiencing high frequency vibrations. The previous study concluded that snubbers should not be used in high frequency vibratory environments due to deterioration in the quality of hydraulic fluid and an increase in wear on snubber components. The present study takes a closer look at heat energy added to the system due to such high frequency vibrations. The power delivered by a typical vibration observed in an industrial piping system is calculated and assumed to enter into the snubber fluid as heat. This is modeled using a thermal finite element simulation and the resulting thermal distribution pattern, within the snubber body, is produced. Also, a separate analysis is performed in order to get a thermal distribution pattern on a snubber due to an increase in the environmental temperature. This distribution pattern is then compared with the one obtained from an internal heat source. The study is performed using computational methods in conjunction with analytical methods to determine if heat energy is the main cause of snubber fluid deterioration.
Ductility and Fatigue Strength Loss of a Hydrogen-Charged 316L Austenitic Stainless Steel
Authors: Baek Un Bong , Nguyen Thanh Tuan , Nahm Seung Hoon , Ryu Kwon Sang 
Published: November 2019

Abstract
The susceptibility of 316L-type austenite stainless steel to hydrogen was quantified by means of SSRT results and low-cycle fatigue life measurement. Both tests were conducted in the air condition after being charged with high-pressure hydrogen gas of 10 MPa and a temperature of 300°C for 120 hours. In addition, SSRT tests in gaseous hydrogen at a pressure of 10 MPa were also performed and compared to the tests conducted in hydrogen pre-charged and as-received conditions. The 0.2% yield strength and tensile strength did not show there to be a considerable difference between hydrogen pre-charging and the as-received conditions, whereas the gaseous hydrogen condition revealed a remarkable degradation in tensile properties, especially in terms of fracture elongation. In the case of fatigue life test, a considerable influence of hydrogen pre-charging in fatigue life properties was observed in the high strain amplitude regime whereas the measured values in the low strain deformation region are consistently comparable to that in the as-received condition. Fatigue limit was not affected by hydrogen pre-charging.
Review of Tensile Strain Capacity Prediction Models for Strain-Based Design of Pipelines
Authors: Park Dong-Yeob , Gianetto James A. 
Published: November 2019

Abstract
In this paper, three tenile strain capacity (TSC) prediction models developed for strain-based design (SBD) of girth-welded pipelines were reviewed, together with a brief introduction of technical backgrounds of their development. Most TSC models rely on small-scale mechanical and fracture toughness measurements to estimate the TSC of pipelines. Hence, we surveyed published experimental and computational data to examine the transferability of small-scale fracture toughness measurements to large-scale pipe fractures. Lastly, some gaps and issues that were found from the review are proposed for improvement of TSC models for SBD. The critical issues found with current TSC models and SBD are (a) differences in strain measurement for full-scale pipe tests/simulations, (b) multiple crack tip opening displacement (CTOD) definitions, (c) no application of J-integral as a toughness parameter, (d) no consensus on failure criteria, and (e) inconsideration of thermal and natural strain aging effects.
Stress Intensity Factors for an Edge Crack Interacting With an Embedded Parallel Crack for a Finite Plate Under Pure Bending
Authors: Ma Qin , Perl Mordechai , Levy Cesar 
Published: November 2019

Abstract
Parallel cracks are often detected in components under various pressurized applications using non-destructive methods. For non-aligned parallel cracks, on-site service needs to decide whether they should be treated as coalesced cracks or separate multiple cracks for Fitness-for-Service Criteria. Such standards are very different from one another for the adjustment of multiple nonaligned cracks in existing sources. Furthermore, those criteria and standards are often derived from on-site service experience without rigorous and systematic verification. Based on this observation, in this study, we investigate stress intensity factors of an edge crack in a finite plate under pure bending when interacted by an imbedded parallel crack. Different criteria and standards are then used to correlate the present results in order to recommend the usage of those standards for the purpose of Fitness-for-Service and to classify the standards as either conservative or non-conservative. If H and S represent the vertical gap and horizontal separation distance between the cracks, respectively, and a2 is the length of the crack, a parametric study of parallel crack separation distance and gap on the crack stress intensity factor has been undertaken. The parallel cracks are practically located within the tensile bending stress regime only. Stress intensity factors (SIFs) have been acquired for a wide range of the normalized horizontal gap of S/a2 = 0.4∼2.0 and the normalized separation distance of H/a2 = −0.5∼2.0 between the two parallel cracks based on the principle of linear elastic fracture mechanics (LEFM). Our study indicates that certain existing standards/criteria provide results that are much more conservative than others while certain ones do not provide adequate information for application.
Effects of Welding Processes and Techniques on Mechanical and Metallurgical Properties of Dissimilar Metal Weld
Authors: Sun Dongmei (Donna) , Duan Xinjian 
Published: November 2019

Abstract
The dissimilar metal weld (DMW) is widely used in fabrication and manufacturing in various industries. Joining between nickel-based alloy and ferritic steel tubing and piping is commonly employed for ASME Code compliant welds for high-temperature and corrosion resistance applications.
A series of DMW samples between alloy 600 pipe and SA-106 Grade B pipe are fabricated using different welding processes, joint design and welding techniques. By detailed comparison, this paper provides insight into the effects of these different welding variables on mechanical properties (tensile properties and hardness of weld materials and heat affected zone), metallurgical properties (macro and microstructure examination) and chemistry (root pass alloying dilution etc.)
It has been shown that an asymmetric joint bevel design in consideration of different heat dissipation, melting temperature of the two materials will promote good weld bead formation during the root pass welding. Different joint designs (such as with or without consumable insert) will create variations on weld dilution and Cr/Ni recovery in the root area. Other welding variables such as tungsten electrode location for root pass welding for DMW, machine Gas Tungsten Arc Welding (GTAW) using hot wire and cold wire, etc. are also discussed.