The Experts below are selected from a list of 18462 Experts worldwide ranked by ideXlab platform
Gao Zhen - One of the best experts on this subject based on the ideXlab platform.
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A comprehensive Numerical investigation of the impact behaviour of an offshore wind turbine blade due to impact loads during installation
Elsevier, 2019Co-Authors: Verma, Amrit Shankar, Vedvik, Nils Petter, Gao ZhenAbstract:For installing offshore wind turbines into deep waters, use of floating crane vessels is essential. One of the major challenges is their sensitivity to wave-induced vessel and crane tip motions, which can cause the impact of lifted components like blades and nacelle with nearby structures. The impact loads on fibre composite wind turbine blades are critical as several complex damage modes, capable of affecting the structural integrity, are developed. Planning of such installation tasks therefore requires response-based operational limits that consider impact loads on the blade along with their damage quantification. The research area considering the impact behaviour of the lifted blade is novel, and thus, the paper identifies vessel, blade and lifting parameters that determine impact/contact scenarios. Furthermore, for a case in which a lifted blade with its leading edge impacts the tower, a Numerical Modelling Technique is presented in Abaqus/Explicit, and a comprehensive damage assessment of the blade and an investigation of the impact dynamics and energy evolution are performed. Sensitivity studies for two distinct blade designs and two different impact locations are considered. The results show that 7–20% of the impact energy is absorbed as damage in the blade, whereas the majority dissipates as rigid-body motions of the blade after the impact. The findings of the study highlight the requirement for advanced installation equipment, such as active tugger lines, to prevent successive impacts of wind turbine blades during installation
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A comprehensive Numerical investigation of the impact behaviour of an offshore wind turbine blade due to impact loads during installation
Elsevier, 2019Co-Authors: Verma, Amrit Shankar, Vedvik, Nils Petter, Gao ZhenAbstract:For installing offshore wind turbines into deep waters, use of floating crane vessels is essential. One of the major challenges is their sensitivity to wave-induced vessel and crane tip motions, which can cause the impact of lifted components like blades and nacelle with nearby structures. The impact loads on fibre composite wind turbine blades are critical as several complex damage modes, capable of affecting the structural integrity, are developed. Planning of such installation tasks therefore requires response-based operational limits that consider impact loads on the blade along with their damage quantification. The research area considering the impact behaviour of the lifted blade is novel, and thus, the paper identifies vessel, blade and lifting parameters that determine impact/contact scenarios. Furthermore, for a case in which a lifted blade with its leading edge impacts the tower, a Numerical Modelling Technique is presented in Abaqus/Explicit, and a comprehensive damage assessment of the blade and an investigation of the impact dynamics and energy evolution are performed. Sensitivity studies for two distinct blade designs and two different impact locations are considered. The results show that 7–20% of the impact energy is absorbed as damage in the blade, whereas the majority dissipates as rigid-body motions of the blade after the impact. The findings of the study highlight the requirement for advanced installation equipment, such as active tugger lines, to prevent successive impacts of wind turbine blades during installation.submittedVersionThis is a submitted manuscript of an article published by Elsevier Ltd in Ocean Engneering, 4 December 201
Ee Hellstrom - One of the best experts on this subject based on the ideXlab platform.
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Numerical Modelling of iron-pnictide bulk superconductor magnetisation
'BioProcessing Journal', 2017Co-Authors: Yamamoto A, Fujishiro H, Jd Weiss, Ee HellstromAbstract:The iron-based superconductors exhibit a number of properties attractive for applications, including low anisotropy, high upper critical magnetic fields (Hc2) in excess of 90 T and intrinsic critical current densities above 1 MA/cm2 (0 T, 4.2 K). It was shown recently that bulk iron-pnictide superconducting magnets capable of trapping over 1 T (5 K) and 0.5 T (20 K) can be fabricated with fine-grain polycrystalline Ba0.6K0.4Fe2As2 (Ba122). These Ba122 magnets were processed by a scalable, versatile and low-cost method using common industrial ceramic processing Techniques. In this paper, a standard Numerical Modelling Technique, based on a 2D axisymmetric finite-element model implementing the H-formulation, is used to investigate the magnetisation properties of such iron-pnictide bulk superconductors. Using the measured Jc(B, T) characteristics of a small specimen taken from a bulk Ba122 sample, experimentally measured trapped fields are reproduced well for a single bulk, as well as a stack of bulks. Additionally, the influence of the geometric dimensions (thickness and diameter) on the trapped field is analysed, with a view of fabricating larger samples to increase the magnetic field available from such TFMs. It is shown that, with current state-of-the-art superconducting properties, surface trapped fields > 2 T could readily be achieved at 5 K (and > 1 T at 20 K) with a sample of diameter 50 mm. Finally, an aspect ratio of between 1-1.5 for R/H (radius/thickness) would be an appropriate compromise between the accessible, surface trapped field and volume of superconducting material for bulk Ba122 magnets
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Numerical Modelling of iron-pnictide bulk superconductor magnetisation
'Organisation for Economic Co-Operation and Development (OECD)', 2017Co-Authors: Ainslie Mark, Yamamoto A, Fujishiro H, Jd Weiss, Ee HellstromAbstract:The iron-based superconductors exhibit a number of properties attractive for applications, including low anisotropy, high upper critical magnetic fields (Hc2) in excess of 90 T and intrinsic critical current densities above 1 MA/cm2 (0 T, 4.2 K). It was shown recently that bulk iron-pnictide superconducting magnets capable of trapping over 1 T (5 K) and 0.5 T (20 K) can be fabricated with fine-grain polycrystalline Ba0.6K0.4Fe2As2 (Ba122). These Ba122 magnets were processed by a scalable, versatile and low-cost method using common industrial ceramic processing Techniques. In this paper, a standard Numerical Modelling Technique, based on a 2D axisymmetric finite-element model implementing the H-formulation, is used to investigate the magnetisation properties of such iron-pnictide bulk superconductors. Using the measured Jc(B, T) characteristics of a small specimen taken from a bulk Ba122 sample, experimentally measured trapped fields are reproduced well for a single bulk, as well as a stack of bulks. Additionally, the influence of the geometric dimensions (thickness and diameter) on the trapped field is analysed, with a view of fabricating larger samples to increase the magnetic field available from such TFMs. It is shown that, with current state-of-the-art superconducting properties, surface trapped fields > 2 T could readily be achieved at 5 K (and > 1 T at 20 K) with a sample of diameter 50 mm. Finally, an aspect ratio of between 1-1.5 for R/H (radius/thickness) would be an appropriate compromise between the accessible, surface trapped field and volume of superconducting material for bulk Ba122 magnets.Mark Ainslie would like to acknowledge financial support from a Royal Academy of Engineering Research Fellowship. Hiroyuki Fujishiro would like to acknowledge financial support from JSPS KAKENHI Grant No. 15K04646. The work at NHMFL was supported NSF DMR-1306785, by the National High Magnetic Field Laboratory, which is supported by the National Science Foundation under NSF/DMR-1157490, and by the State of Florida. The work at TUAT was supported by MEXT Elements Strategy Initiative to Form Core Research Center and by JSPS KAKENHI Grant No. JP15H05519
Mohamad Ngasri Dimon - One of the best experts on this subject based on the ideXlab platform.
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the study of normal incidence sound absorption coefficience sound absorption of wood circular perforated panel cpp using Numerical Modelling Technique
2006Co-Authors: Mohamad Ngasri DimonAbstract:Wood Circular Perforated Panel (WCPP) is the simple form of direct piercing carved wood panel (DPCWP) which has been widely used in traditional and modern mosques as part of wall partition. This DPCWP can act as sound absorption material. Normal incidence sound absorption coefficient (I±n) of WCPP can not be tested using conventional sound absorption measurement Techniques. Nowadays, Numerical modeling is a powerful Technique to solve these difficulties. Numerical modeling based on Boundary Element Method (BEM) has been widely used for engineering design and prediction. This thesis report on work that has been carried out to investigate normal incidence sound absorption coefficient, (I±n) characteristics of wood circular perforated panel (WCPP) using Boundary Element Method. The perforation ratios investigated are 20%, 30% and 40 %. The panel perforation ratio is ranging in number of apertures, diameter, and distance between apertures. Boundary Element Method simulation is done using Beasy Acoustics software. The simulation is done by creating WCPP geometric model, defining acoustics media properties and boundary conditions. Net sound intensity is simulated by creating point source 2 meter in front of the panel and 16 internal points 0.25I» in front of the panel. Incidence sound intensity is obtained by removing the panel. Comparison and analysis of I±n of WCPP modeled by BEM with I±n measured using sound intensity Technique and theoretical prediction were conducted. It was found out that there is a close correlation of I±n modeled using BEM and I±n measured using sound intensity and theoretical prediction. Statistical regression model for simulation result is developed using SPSS. Third order polynomial is applied to fit the curves of WCPP simulation result and multiple regression model with stepwise method is applied to fit the curve of over all result with perforation ratio and frequency band as independent variable.
J H Durrell - One of the best experts on this subject based on the ideXlab platform.
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flux jump assisted pulsed field magnetisation of high j c bulk high temperature superconductors
Superconductor Science and Technology, 2016Co-Authors: Mark D Ainslie, Difan Zhou, Hiroyuki Fujishiro, K Takahashi, Yunhua Shi, J H DurrellAbstract:Investigating, predicting and optimising practical magnetisation Techniques for charging bulk superconductors is a crucial prerequisite to their use as high performance ‘psuedo’ permanent magnets. The leading Technique for such magnetisation is the pulsed field magnetisation (PFM) Technique, in which a large magnetic field is applied via an external magnetic field pulse of duration of the order of milliseconds. Recently ‘giant field leaps’ have been observed during charging by PFM: this effect greatly aids magnetisation as flux jumps occur in the superconductor leading to magnetic flux suddenly intruding into the centre of the superconductor. This results in a large increase in the measured trapped field at the centre of the top surface of the bulk sample and full magnetisation. Due to the complex nature of the magnetic flux dynamics during the PFM process, simple analytical methods, such as those based on the Bean critical state model, are not applicable. Consequently, in order to successfully model this process, a multi-physical Numerical model is required, including both electromagnetic and thermal considerations over short time scales. In this paper, we show that a standard Numerical Modelling Technique, based on a 2D axisymmetric finite-element model implementing the $H$-formulation, can model this behaviour. In order to reproduce the observed behaviour in our model all that is required is the insertion of a bulk sample of high critical current density, $J_c$. We further explore the consequences of this observation by examining the applicability of the model to a range of previously reported experimental results. Our key conclusion is that the ‘giant field leaps’ reported by Weinstein $\textit{et al}$ and others need no new physical explanation in terms of the behaviour of bulk superconductors: it is clear the ‘giant field leap’ or flux jump-assisted magnetisation of bulk superconductors will be a key enabling technology for practical applications.
Verma, Amrit Shankar - One of the best experts on this subject based on the ideXlab platform.
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A comprehensive Numerical investigation of the impact behaviour of an offshore wind turbine blade due to impact loads during installation
Elsevier, 2019Co-Authors: Verma, Amrit Shankar, Vedvik, Nils Petter, Gao ZhenAbstract:For installing offshore wind turbines into deep waters, use of floating crane vessels is essential. One of the major challenges is their sensitivity to wave-induced vessel and crane tip motions, which can cause the impact of lifted components like blades and nacelle with nearby structures. The impact loads on fibre composite wind turbine blades are critical as several complex damage modes, capable of affecting the structural integrity, are developed. Planning of such installation tasks therefore requires response-based operational limits that consider impact loads on the blade along with their damage quantification. The research area considering the impact behaviour of the lifted blade is novel, and thus, the paper identifies vessel, blade and lifting parameters that determine impact/contact scenarios. Furthermore, for a case in which a lifted blade with its leading edge impacts the tower, a Numerical Modelling Technique is presented in Abaqus/Explicit, and a comprehensive damage assessment of the blade and an investigation of the impact dynamics and energy evolution are performed. Sensitivity studies for two distinct blade designs and two different impact locations are considered. The results show that 7–20% of the impact energy is absorbed as damage in the blade, whereas the majority dissipates as rigid-body motions of the blade after the impact. The findings of the study highlight the requirement for advanced installation equipment, such as active tugger lines, to prevent successive impacts of wind turbine blades during installation
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A comprehensive Numerical investigation of the impact behaviour of an offshore wind turbine blade due to impact loads during installation
Elsevier, 2019Co-Authors: Verma, Amrit Shankar, Vedvik, Nils Petter, Gao ZhenAbstract:For installing offshore wind turbines into deep waters, use of floating crane vessels is essential. One of the major challenges is their sensitivity to wave-induced vessel and crane tip motions, which can cause the impact of lifted components like blades and nacelle with nearby structures. The impact loads on fibre composite wind turbine blades are critical as several complex damage modes, capable of affecting the structural integrity, are developed. Planning of such installation tasks therefore requires response-based operational limits that consider impact loads on the blade along with their damage quantification. The research area considering the impact behaviour of the lifted blade is novel, and thus, the paper identifies vessel, blade and lifting parameters that determine impact/contact scenarios. Furthermore, for a case in which a lifted blade with its leading edge impacts the tower, a Numerical Modelling Technique is presented in Abaqus/Explicit, and a comprehensive damage assessment of the blade and an investigation of the impact dynamics and energy evolution are performed. Sensitivity studies for two distinct blade designs and two different impact locations are considered. The results show that 7–20% of the impact energy is absorbed as damage in the blade, whereas the majority dissipates as rigid-body motions of the blade after the impact. The findings of the study highlight the requirement for advanced installation equipment, such as active tugger lines, to prevent successive impacts of wind turbine blades during installation.submittedVersionThis is a submitted manuscript of an article published by Elsevier Ltd in Ocean Engneering, 4 December 201
