bluuebunny/crossref_metadata_2025_split huggingface dataset:
Failure Estimation of Offshore Renewable Energy Devices Based on Hierarchical Bayesian Approach
Authors: Abaei Mohammad Mahdi , Arini Nu Rhahida , Thies Philipp R. , Lars Johanning 
Published: November 2019

Abstract
Improving the reliability of marine renewable energy devices such as wave and tidal energy convertors is an important task, primarily to minimize the perceived risks and reduce the associated cost for operation and maintenance. Marine systems involve a wide range of uncertainties, due to the complexity of failure mechanism of the marine components, scarcity of data, human interactions and randomness of the sea environment. The fundamental element of a probabilistic risk analysis necessarily needs to rely on operational information and observation data to quantify the performance of the system. However, in reality it is difficult to ascertain observation of the precursor data according to the number of component failures that have occurred, mainly as a result of imprecision in the failure criterion, record keeping, or experimental and physical modelling of the process. Traditional reliability estimation approaches such as Fault Tree, Event Tree and Reliability Block Diagram analysis offer simplified, rarely realistic models of this complex reliability problem. The main reason is that they all rely on accurate prior information as a perquisite for performing reliability assessment. In this paper, a hierarchical Bayesian framework is developed for modelling marine renewable component failures encountered the uncertainty. The proposed approach is capable to incorporate the conditions, which lack reliable observation data (e.g. unknown/uncertain failure rate of a component). The hierarchical Bayesian framework provides a platform for the propagation of uncertainties through the reliability assessment of the system, via Markov Chain Monte Carlo (MCMC) sampling. The advantages of using MCMC sampling has proliferated Bayesian inference for conducting risk and reliability assessment of engineering system. It is able to use hyper-priors to represent prior parameters as a subjective observations for probability estimation of the failure events and enable an updating process for quantitative reasoning of interdependence between parameters. The developed framework will be an assistive tool for a better monitoring of the operation in terms of evaluating performance of marine renewable system under the risk of failure. The paper illustrates the approach using a tidal energy convertor as a case study for estimating components failure rates and representing the uncertainties of system reliability. The paper will be of interest to reliability practitioners and researchers, as well as tidal energy technology and project developers, seeking a more accurate reliability estimation framework.
CTOD Fracture Toughness Assessment Under Different Notch Type (Fatigue Pre-Cracking and EDM)
Authors: Marines-Garcia Israel , Aguilar Aaron , Carreon Kristian , Darcis Philippe 
Published: November 2019

Abstract
The standardization of any mechanical material characterization is aiming to get homogenization on the testing physical execution by independent laboratories and to drive for accurate material evaluation between different entities. However, from time to time, standard tests may be reconsidered in order to improve their efficacy, execution time and incorporate new testing techniques or technologies without compromising the testing results and consistency. In the present work, fracture toughness crack tip opening displacement (CTOD) testing is addressed and particularly the need to perform fatigue pre-cracking prior monotonic testing. Without the fatigue pre-cracking, CTOD testing time can be significantly reduced during the preparation of specimens, meaning that specimens can be tested as soon as they are machined.
Wire electro-discharge machining (EDM) technique allows generating sharp tip notches, and presents a good alternative to the standards specified fatigue pre-cracking [1–2]. In addition, this machining technology reduces the risk of rejecting the specimen testing, particularly when targeting weld heat affected zone/fusion line (HAZ/FL) microstructure on specimens with surface notch DNV-ST-F101 Figure B-9 [3], where it is specified that the crack tip shall be within a narrow distance (0.5 mm) from the fusion line (FL) or assess grain coarsened heat affected zone (GCHAZ) microstructure as indicated in DNV-ST-F101 section B.2.8.7 [3]. Herein, it is presented an assessment carried out in order to identify the notch type effect over the fracture toughness (CTOD) considering notches conditions as standard fatigue pre-crack and wire electro-discharge machining (EDM).
Fifteen (15) CTOD specimens were manufactured from plain pipe material (same pipe), 251.3 mm OD × 20.9 mm WT, SMLS 450PD and tested according to ISO 12135 recommendations [1], they were distributed as follow; five (5) specimens according to standard recommendations with fatigue pre-cracking length ≥ 1.3 mm or 2.5%W (whichever is bigger), five (5) specimens with a fatigue pre-cracking length &lt; 1.3 mm (between 0.5 mm to 1 mm), and five (5) specimens without fatigue pre-cracking (EDM notch), additionally, results from five (5) specimens previously tested in a round robin (RR) testing performed internally by Tenaris using the same LP material and standard fatigue pre-crack length. The crack length target (a/W) was kept 0.5 for all cases.
Even if the sampling population is relatively small considering the three notch conditions, it seems that EDM might be an alternative to the standard specified fatigue pre-cracking. Thus, this experimental assessment aims to open the discussion on the use of EDM notch as alternative.
Application of Phase Decomposition to the Analysis of Random Time Series From Wave Basin Tests
Authors: Adcock Thomas A. A. , Feng Xingya , Tang Tianning , van den Bremer Ton S. , Day Sandy , Dai Saishuai , Li Ye , Lin Zhiliang , Xu Wentao , Taylor Paul H. 
Published: November 2019

Abstract
Many ocean engineering problems involve bound harmonics which are slaved to some underlying assumed close to linear time series. When analyzing signals we often want to remove the bound harmonics so as to “linearise” the data or to extract individual bound harmonic components so that they may be studied. For even moderately broadbanded systems filtering in the frequency domain is not sufficient to separate components as they overlap in frequency. One way to overcome this difficulty is to use input signals with the same linear envelope but with different phases and then use simple addition and subtraction of the resulting signals to extract different harmonics. This approach has been established for the analysis of wave groups. In this paper we examine whether this approach can be used on random time series as well. We analyse random wave time series of wave elevation from the towing tank in Shanghai Jiao Tong University and force measurements on a cylinder taken in the Kelvin tank at the University of Strathclyde.
Protection of Pipelines and Cables With a Combination of Soil and Rock Cover
Authors: Morrow Damian R. , Small Andrew A. 
Published: November 2019

Abstract
Soil cover, rock cover and a combination of soil and rock cover are common approaches to protecting pipelines, cables and umbilicals associated with offshore energy infrastructure. However, with the exception of a simplified rock cover case or a simplified sand cover case, there is limited published guidance with respect to this design consideration.
Based on a bearing capacity approach, geotechnical numerical analysis techniques have been used to investigate the protection provided by a range uniform and mixed cover scenario. Effects related to rock placement in a slot-shaped trench have also been investigated.
Relatively standard observations were noted with respect to the protection provided by uniform soil or rock cover cases, including noting the different behaviours associated with granular drained cover materials and cohesive undrained cover materials. Some significant observations were made concerning the mixed cover cases. Of particular note was the impact of very soft clay as a limitation on the protection provided by the rock material. The influence of adjacent soil conditions on the protection provided by a rock infilled slot-shaped trench was also noted from analysis results.
A Monte Carlo Based Simulation Method for Damage Stability Problems
Authors: Krüger Stefan , Dankowski Hendrik 
Published: November 2019

Abstract
To cope with future developments of the SOLAS 2009 B1, damage stability investigations must become a central part of the initial design phase. If damage stability calculations are performed in the classical way, they are very time consuming with respect to both modelling and computational time. To overcome this problem, damage stability can be treated as a stochastic process, where the probability of a damage case and the survivability of that particular damage case need to be determined. This task can be solved by direct numerical simulations based on the Monte Carlo principle. If statistical damage distributions are once known, the Monte Carlo simulation delivers a population of damages which can be automatically related to certain damage cases. These damage cases can then be investigated with respect to their survivability.
Applying this principle to SOLAS 2009 damage stability calculations leads to a number of implementation problems which must be solved to guarantee that the MC simulation delivers exactly the same results as the manual, zone based damaged stability calculation. If these problems are solved, the MC based damage stability calculations can be used during the initial design phase until the damage stability approval. The proposed method reduces the computational effort drastically which supports the initial design phase of the ship’s compartmentation. The method further leads to higher attained indices and consequently to a safer and more efficient design.
An Investigation Into the Effect of Biofouling on Full-Scale Propeller Performance Using CFD
Authors: Song Soonseok , Demirel Yigit Kemal , Atlar Mehmet 
Published: November 2019

Abstract
The negative effect of biofouling on ship resistance has been investigated since the early days of naval architecture. However, for more precise prediction of fuel consumption of ships, understanding the effect of biofouling on ship propulsion performance is also important. In this study, CFD simulations for the full-scale performance of KP505 propeller in open water, including the presence of marine biofouling, were conducted. To predict the effect of barnacle fouling on the propeller performance, experimentally obtained roughness functions of barnacle fouling were employed in the wall-function of the CFD software. The roughness effect of barnacles of varying sizes and coverages on the propeller open water performance was predicted for advance coefficients ranging from 0.2 to 0.8. From the simulations, drastic effects of barnacle fouling on the propeller open water performance were found. The result suggests that the thrust coefficient decreases while the torque coefficient increases with increasing level of surface fouling, which leads to a reduction of the open water efficiency of the propeller. Further investigations into the roughness effect on the pressure and velocity field, surface pressure and wall shear stress, and propeller vortices were examined.
Improved Fatigue Design of SCR Modified Miner’s Rule
Authors: Knagenhjelm Hans Olav , Hauge Mons , Nyhus Bård 
Published: November 2019

Abstract
The Aasta Hansteen floating production system is the first SPAR platform with steel catenary risers (SCR) at the Norwegian Continental Shelf (NCS). The water depth is 1300 msw. The weather conditions with respect to wave loading are more severe than any offshore installation completed so far. Under such environmental conditions, it is vital to verify the design of the SCR’s with respect to extreme loading and fatigue life.
A fatigue verification program has been executed for ground OD welds of both clad and carbon steel riser materials. The objective was to determine the effect of weld defects in combination with the effect of variable amplitude loading using the actual fatigue stress distribution experienced by critical parts of the SCR. The stress distribution is based on the local wave spectrum and estimated from hydrodynamic analysis of the riser and the long-term wave statistics.
Two clad pipes and one carbon steel pipe was exposed to rotation bending fatigue testing with artificially imposed defects. One clad pipes gave fracture after more than 1.0 × 109 cycles. The carbon steel pipe gave fracture after 4.56 × 108 cycles.
A modified Miner’s summation rule is proposed for variable amplitude fatigue design. The procedure is based on a verification of variable amplitude testing against constant amplitude testing. The results indicate that load amplitudes below a fatigue limit defined at 107 cycles are not contributing significantly to fatigue crack initiation and growth from a weld defect. The proposed method suggests an engineering approach to this by a modification of the Miner’s rule for VA loading.
Design Methodology and Development of an Independently Rotating Multi-Hull Vessel
Authors: Nihei Yasunori , Srinivasamurthy Sharath , Sakamoto Hiroshi , Masuda Norikazu , Hara Naoyuki 
Published: November 2019

Abstract
Aquaculture farms play a vital role for food security in Japan. The cultivation potential is directly related to the quality of the marine environment. Water quality parameters such as dissolved oxygen and temperature need to be measured and monitored regularly throughout the cultivation period. Energy efficiency and ease of navigation are the prime requirements for environmental survey vessels. In this paper, a new and novel automated vessel is introduced and design methodology is explained. Multi-hull innovative vessel is named as ‘Quadmaran’ and developed particularly for carrying out environmental surveys. The vessel consists of four hulls each capable of rotating independently thereby leading to better sailing performance and excellent stability. It is equipped with devices to measure quality parameters at various water depths and includes a dynamic positioning system aiding for the environment data collection. The basic design criteria of the Quadmaran is derived and understood in this study. Scaled model (1/3 scale) is fabricated for tank tests and resistance tests are carried out in a circulating water tank at Osaka Prefecture University, Osaka, Japan. With the knowledge gained from tank tests, multi-hull phenomenon of the Quadmaran is studied and interaction between the hulls is investigated. It is found that wave interference due to hull orientation becomes significant for Froude number greater than 0.5 and resistance of Quadmaran is found to be less than two times the twin hull resistance for same water draft. Further, an attempt is made to understand how the configuration arrangement affects the resistance of the vessel.
Prediction of Internal Pressure of Flexible Pipe
Authors: Shao Qiangqiang , Liu Ting , Yuan Shuai , Han Peihua , Bai Yong 
Published: November 2019

Abstract
The flexible pipes are widely used in the oil and gas industry to transport petroleum products. The pipe might burst fails when a large internal fluid pressure acts on the pipe, and the consequences are disastrous. In order to ensure the security and reliability of flexible pipes in the application, the mechanical responses of the pipe subjected to high pressure loads should be carefully estimated. The main purpose of this paper is to investigate the burst pressure of the pipe. Based on the principle of virtual work, a theoretical model for stress and deformations of the pipe is established, which takes the material plasticity into consideration. In addition, a finite element model is developed by ABAQUS to verify the feasibility of the theoretical model. According to the verified model, it is efficient to predict the burst pressure and design its cross-section economically with its serving conditions.
Irregular Frequency Removal and Convergence in Higher-Order BEM for Wave Diffraction/Radiation Analysis
Authors: Utsunomiya Tomoaki 
Published: November 2019

Abstract
Higher-order boundary element method (HOBEM) for wave diffraction/radiation analysis is a powerful tool for its applicability to a general (curved) geometry. Inspired by the paper which examined the convergence of BIE code with constant panels (Martic, et al., 2018; OMAE2018-77999), the convergence characteristics of HOBEM with quadrilateral panels have been examined. Here, the effect of removal of irregular frequencies is particularly focused as discussed by Martic, et al. (2018). The irregular frequency removal has been made by the rigid-lid method which is applicable to HOBEM, where the intersection line between the body-surface and the free-surface should be carefully handled. The results show that for first order quantities the convergence is quite good for both cases with/without irregular frequency removal (except where the irregular frequencies affect for the case without irregular frequency removal). For mean drift forces, the convergence becomes poor particularly for the case without irregular frequency removal. The convergence characteristics are examined and some discussions are made.
Four-Point Bending of Metallic I-Core Sandwich Beams With Longitudinal Girder
Authors: Hu Wenwei , Liu Jun , Zhang Pan , Cheng Yuansheng 
Published: November 2019

Abstract
I-core sandwich structure has great potential in the application of hull structure construction due to its high specific strength and relatively simple manufacturing process. The topic on the study of mechanical properties of I-core sandwich structure under bending loads is of interest to structural designers since the structure is often subjected to bending loads in engineering applications. In this paper, a metallic I-core sandwich beam with longitudinal girder was designed and manufactured using laser welding technique, and finally tested under four-point bend loading. The elastic-plastic behaviors and the ultimate load carrying capacity of this novel beam structure were obtained. A numerical model was developed to investigate the mechanical properties of this novel beam structure by finite element method. The results of the numerical model were compared with experimental data. Stress components of the front face and back face in the failure process were analyzed and discussed to investigate the failure of them. Results showed that the huge local bending stresses of plate caused the failure of the front face and back face. Finally, an improved scheme for the test was proposed to provide a pure bending load, which was proved by finite element simulation. All the findings aim to guide the engineering application of this structure.
CFD Modelling of an Electrically Trace Heated Blanket
Authors: Le Toux Vincent , Harchambois Stéphanie , Guindeuil Geoffrey , Vivet Romain , Pasquet François-Xavier , Tosi Guillaume , Palermo Thierry , Herrera Gilbert , T'Joen Christophe 
Published: November 2019

Abstract
The Electrically Trace Heated Blanket (ETH-Blanket) is a new offshore intervention/remediation system currently in development by TechnipFMC for the efficient remediation of plugs due to hydrates or wax in subsea production and injection flowlines. The ETH-Blanket consists of a network of heating cables placed underneath an insulation layer which is laid onto the seabed above the plugged flowline. By applying electrical power to the cables, heat is generated by Joule effect which warms up the flowline content until hydrate dissociation or wax plug remediation through softening or complete melting.
As part of a Joint Industry Project (JIP) between TechnipFMC, Shell and Total, full-scale thermal testing of an ETH-Blanket prototype was carried out in Artelia facilities (Grenoble, France). This testing was performed to verify the capability of the ETH-Blanket system to increase the temperature of the fluid inside a pipe sample above a target temperature (hydrate dissociation temperature or wax disappearance temperature) for various conditions. The impact of lateral misalignment of the ETH-blanket on the pipe and of the pipe burial depth were studied. Moreover, the tests were carried out on two pipe samples, with different designs and insulation properties.
CFD models of the test set-up have been built to replicate the thermal behaviour of the ETH-Blanket prototype. Once validated against the test results, the final aim of CFD modelling is to be able to calculate the performances of the system in real subsea conditions. The modelling of the prototype includes a 3D geometry of the system including the soil, natural convection of water between the ETH-blanket and the pipe sample and natural convection of fluid in the pipe sample.
The present paper focuses on the CFD work performed to match the full-scale thermal test results and to predict the ETH-Blanket performances for real subsea operating conditions. It will describe the various CFD models used, the sensitivities and findings in terms of local and global heat transfer and flow effects and the comparison to the experimental data.
Subsea Rigid Jumper Design Optimization for Sour Service Application
Authors: Toleman Benjamin , Huang Chaojun , Sonawane Mahesh , Shankaran Rohit , Foster Danny 
Published: November 2019

Abstract
Subsea rigid jumpers are designed to meet numerous criteria including thermal and pressure effects, environmental and riser / pipeline interaction loads, slugging, and other field specific requirements. Jumper VIV can be a concern in fields with strong bottom currents. Without the benefit of detailed VIV fatigue analysis, designers must rely on experience and engineering judgement on placement of strakes if VIV is identified as a concern. VIV mitigation is even more challenging because the jumpers can contain numerous long and short design options to accommodate tolerances for subsea well locations and installation tolerances of subsea PLETS and manifolds.
This paper will discuss a case study on optimization of 12 M-shaped jumpers designed for a sour service application in Gulf of Mexico. VIV fatigue assessment of the preliminary jumper design and the methodology adopted to optimize the jumper design and placement of VIV suppression will be discussed. Challenges in meeting high target fatigue life due to sour service application will be discussed. The key challenges whilst optimizing an acceptable VIV suppression solution are the assumed effectiveness of strakes, cost / available inventory of strakes, and physical limitations for placement of strakes.
This paper will highlight the trade-offs that are required to strike a balance between strength and fatigue design requirements when using straked buoyancy modules vs. regular strakes. The paper will also highlight the current limitations in design code that relies on standards developed for pipeline application. An alternative method / modification to the DNV F105 approach used to calculate the cross-flow induced in-line VIV fatigue damage is also discussed.