Letteratura scientifica selezionata sul tema "BLADE STRUCTURAL CHARACTERISTICS"
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Articoli di riviste sul tema "BLADE STRUCTURAL CHARACTERISTICS"
1
Li, Chaofeng, Shihua Zhou, Shuhua Yang, Xiang Ren e Bangchun Wen. "Dynamic Characteristics of Blade-Disk-Rotor System with Structural Mistuned Features". Open Mechanical Engineering Journal 8, n. 1 (18 aprile 2014): 138–43. http://dx.doi.org/10.2174/1874155x20140501008.
Testo completoAbstract (sommario):
The finite element method is adopted to establish the dynamical models of blade, bladed disk and blades-diskshaft assemblies. Based on the analysis of mistuned structure and the dynamic characteristics of model in different levels, it gives the vibration mode distribution of different models. The research shows that the characteristics of the bladed disk and shaft have a huge difference, where some modes are caused by the strongly split and coupled vibration. The mistuned effects are likely to cause different coupled vibrations of blades between the blades-disk model and the blades-disk-shaft model. Meanwhile, it shows the frequency separation and concentration, and misses the system mode and the local vibration, which bring some difficulties for designing the blade-rotor system. In this paper, the results may provide a certain reference for blade-rotor system design and diagnosis.
2
Xing, Zhitai, Yan Jia, Lei Zhang, Xiaowen Song, Yanfeng Zhang, Jianxin Wu, Zekun Wang, Jicai Guo e Qingan Li. "Research on Wind Turbine Blade Damage Fault Diagnosis Based on GH Bladed". Journal of Marine Science and Engineering 11, n. 6 (26 maggio 2023): 1126. http://dx.doi.org/10.3390/jmse11061126.
Testo completoAbstract (sommario):
With the increasing installed capacity of wind turbines, ensuring the safe operation of wind turbines is of great significance. However, the failure of wind turbines is still a severe problem, especially as blade damage can cause serious harm. To detect blade damage in time and prevent the accumulation of microdamage of blades evolving into severe injury, a damage dataset based on GH Bladed simulation of blade damage is proposed. Then, based on the wavelet packet analysis theory method, the MATLAB software can automatically analyze and extract the energy characteristics of the signal to identify the damage. Finally, the GH Bladed simulation software and MATLAB software are combined for fault diagnosis analysis. The results show that the proposed method based on GH Bladed to simulate blade damage and wavelet packet analysis can extract damage characteristics and identify single-unit damage, multiple-unit damage, and different degrees of damage. This method can quickly and effectively judge the damage to wind turbine blades; it provides a basis for further research on wind turbine blade damage fault diagnosis.
3
Xu, Lin, Wen Lei Sun e An Wu. "Structural Properties Analysis of Composite Wind Turbine Blade". Key Engineering Materials 522 (agosto 2012): 602–5. http://dx.doi.org/10.4028/www.scientific.net/kem.522.602.
Testo completoAbstract (sommario):
In the process of wind turbine operation, the blade needs to withstand various kinds of loads. With wind turbine power kept getting bigger, the strength requirement of the blades become higher. In order to improve the strength of the blade, lots of new composite materials are use in blade material component parts. This paper studies the geometry laminated structure, external and structural characteristics of composite blade.
4
Chetan, Mayank, Shulong Yao e D. Todd Griffith. "Flutter behavior of highly flexible blades for two- and three-bladed wind turbines". Wind Energy Science 7, n. 4 (22 agosto 2022): 1731–51. http://dx.doi.org/10.5194/wes-7-1731-2022.
Testo completoAbstract (sommario):
Abstract. With the progression of novel design, material, and manufacturing technologies, the wind energy industry has successfully produced larger and larger wind turbine rotor blades while driving down the levelized cost of energy (LCOE). Though the benefits of larger turbine blades are appealing, larger blades are prone to aeroelastic instabilities due to their long, slender, highly flexible nature, and this effect is accentuated as rotors further grow in size. In addition to the trend of larger rotors, non-traditional rotor concepts are emerging including two-bladed rotors and downwind configurations. In this work, we introduce a comprehensive evaluation of flutter behavior including classical flutter, edgewise vibration, and flutter mode characteristics for two-bladed, downwind rotors. Flutter speed trends and characteristics for a series of both two- and three-bladed rotors are analyzed and compared in order to illustrate the flutter behavior of two-bladed rotors relative to more well-known flutter characteristics of three-bladed rotors. In addition, we examine the important problem of blade design to mitigate flutter and present a solution to mitigate flutter in the structural design process. A study is carried out evaluating the effect of leading edge and trailing edge reinforcement on flutter speed and hence demonstrates the ability to increase the flutter speed and satisfy structural design requirements (such as fatigue) while maintaining or even reducing blade mass.
5
Rogge, Timo, Ricarda Berger, Linus Pohle, Raimund Rolfes e Jörg Wallaschek. "Efficient structural analysis of gas turbine blades". Aircraft Engineering and Aerospace Technology 90, n. 9 (14 novembre 2018): 1305–16. http://dx.doi.org/10.1108/aeat-05-2016-0085.
Testo completoAbstract (sommario):
Purpose The purpose of this study a fast procedure for the structural analysis of gas turbine blades in aircraft engines. In this connection, investigations on the behavior of gas turbine blades concentrate on the analysis and evaluation of starting dynamics and fatigue strength. Besides, the influence of structural mistuning on the vibration characteristics of the single blade is analyzed and discussed. Design/methodology/approach A basic computation cycle is generated from a flight profile to describe the operating history of the gas turbine blade properly. Within an approximation approach for high-frequency vibrations, maximum vibration amplitudes are computed by superposition of stationary frequency responses by means of weighting functions. In addition, a two-way coupling approach determines the influence of structural mistuning on the vibration of a single blade. Fatigue strength of gas turbine blades is analyzed with a semi-analytical approach. The progressive damage analysis is based on MINER’s damage accumulation assuming a quasi-stable behavior of the structure. Findings The application to a gas turbine blade shows the computational capabilities of the approach presented. Structural characteristics are obtained by robust and stable computations using a detailed finite element model considering different load conditions. A high quality of results is realized while reducing the numerical costs significantly. Research limitations/implications The method used for analyzing the starting dynamics is based on the assumption of a quasi-static state. For structures with a sufficiently high stiffness, such as the gas turbine blades in the present work, this procedure is justified. The fatigue damage approach relies on the existence of a quasi-stable cyclic stress condition, which in general occurs for isotropic materials, as is the case for gas turbine blades. Practical implications Owing to the use of efficient analysis methods, a fast evaluation of the gas turbine blade within a stochastic analysis is feasible. Originality/value The fast numerical methods and the use of the full finite element model enable performing a structural analysis of any blade structure with a high quality of results.
6
Liang, Zhi Chao, Jie Hong, Yan Hong Ma e Tian Yuan He. "FEM Modeling Technology and Vibration Analysis of Flexible Rotor System". Applied Mechanics and Materials 226-228 (novembre 2012): 257–61. http://dx.doi.org/10.4028/www.scientific.net/amm.226-228.257.
Testo completoAbstract (sommario):
The low-pressure spool in a high-bypass ratio turbofan engine has its unique characteristics. The slightness rotor and the large lumped mass in blade and disk are the structural characteristics while the dynamic coupling between bladed-disk and shaft is the mechanical characteristic. This paper studies on the modeling technology of a flexible rotor system based on the finite element method (FEM). The equivalent-disk method, an equivalent principle of finite element modeling, is put forward. The blades are equivalent to a disk which can not only retain the structural and mechanical characteristics but also control the scale of the model and convert the periodic geometry into axisymmetric geometry. The results show that the equivalent-disk method is helpful to improve the modeling techniques of rotor system and can be used in engineering.
7
Mignolet, M. P., A. J. Rivas-Guerra e J. P. Delor. "Identification of Mistuning Characteristics of Bladed Disks From Free Response Data—Part I". Journal of Engineering for Gas Turbines and Power 123, n. 2 (9 giugno 1999): 395–403. http://dx.doi.org/10.1115/1.1338949.
Testo completoAbstract (sommario):
The focus of the present two-part investigation is on the estimation of the dynamic properties, i.e., masses, stiffnesses, natural frequencies, mode shapes and their statistical distributions, of turbomachine blades to be used in the accurate prediction of the forced response of mistuned bladed disks. As input to this process, it is assumed that the lowest natural frequencies of the blades alone have been experimentally measured, for example, in a broach block test. Since the number of measurements is always less than the number of unknowns, this problem is indeterminate in nature. In this first part of the investigation, two distinct approaches will be investigated to resolve the shortfall of data. The first one relies on the imposition of as many constraints as needed to ensure a unique solution to this identification problem. Specifically, the mode shapes and modal masses of the blades are set to their design/tuned counterparts while the modal stiffnesses are varied from blade to blade to match the measured natural frequencies. The second approach, based on the maximum likelihood principle, yields estimates of all the structural parameters of the blades through the minimization of a specified “cost function.” The accuracy of these two techniques in predicting the forced response of mistuned bladed disks will be assessed on simple dynamic models of the blades.
8
Aleshin, Mikhail, Aleksandr Smirnov, Margarita Murzina e Yuri Boldyrev. "On Structural Optimization of The Propeller Blade". International Journal of Engineering & Technology 7, n. 4.36 (1 dicembre 2018): 1203. http://dx.doi.org/10.14419/ijet.v7i4.36.28189.
Testo completoAbstract (sommario):
The results of the structural optimization of propeller blades are presented taking into account its composite structure and pitch change mechanism of the propeller and using FSI (Fluid-Structure Interaction) approaches. The optimality criterion of the problem is the propeller thrust with optimization parameters being the characteristics of the internal structure of the propeller blade made from a composite. Together with the optimization of the blade shape, the problem is considered which concerns the reduction of the deformations caused by loads occurring during the operation of the propeller, since significant deformations of the blades lead to decreased thrust.Thus, the following optimization problem can be formulated: to find the optimal configuration of the composite material and its micro-geometrical parameters along the height of the blade to minimize deformations and increase the thrust of the propeller. At the same time, the optimization parameters are limited by the weight of the propeller and the strength characteristics.The technique presented in the paper allows us to obtain the reliable values of thrust and reduce the estimated computational time. The influence of the structure of the composite material on the mechanical properties of the blades is shown; the values of deformation of the blades under the action of centrifugal and aerodynamic loads are given.
9
Aleshin, Mikhail, Aleksandr Smirnov, Margarita Murzina e Yuri Boldyrev. "On Structural Optimization of the Propeller Blade". International Journal of Engineering & Technology 7, n. 4.36 (9 dicembre 2018): 1203. http://dx.doi.org/10.14419/ijet.v7i4.36.28212.
Testo completoAbstract (sommario):
The results of the structural optimization of propeller blades are presented taking into account its composite structure and pitch change mechanism of the propeller and using FSI (Fluid-Structure Interaction) approaches. The optimality criterion of the problem is the propeller thrust with optimization parameters being the characteristics of the internal structure of the propeller blade made from a composite. Together with the optimization of the blade shape, the problem is considered which concerns the reduction of the deformations caused by loads occurring during the operation of the propeller, since significant deformations of the blades lead to decreased thrust.Thus, the following optimization problem can be formulated: to find the optimal configuration of the composite material and its micro-geometrical parameters along the height of the blade to minimize deformations and increase the thrust of the propeller. At the same time, the optimization parameters are limited by the weight of the propeller and the strength characteristics.The technique presented in the paper allows us to obtain the reliable values of thrust and reduce the estimated computational time. The influence of the structure of the composite material on the mechanical properties of the blades is shown; the values of deformation of the blades under the action of centrifugal and aerodynamic loads are given.
10
Petukhov, A. N., e F. D. Kiselev. "THE IMPACT OF STRESS CONCENTRATORS ON THE STRUCTURAL STRENGTH OF CAST TURBINE BLADES OF AIRCRAFT ENGINES". Industrial laboratory. Diagnostics of materials 85, n. 5 (5 giugno 2019): 52–66. http://dx.doi.org/10.26896/1028-6861-2019-85-5-52-66.
Testo completoAbstract (sommario):
Assessing of the quality parameters of the blade manufacture, which can affect their operational performance, is an important step in determining the causes of turbine blade destruction. Manufacturing defects, despite their great diversity, tend to be stress concentrators. Apart from the defects listed in the specifications to be avoided upon blade manufacturing, we mean also various kinds of defects identified as concentrators that contribute to the destruction of the blades in operation. Assessment of the blade quality suggests identification and analysis of the defects, as well as determination of the technological stage at which they have been formed. For cooled turbine blades this is the foundry stage of their manufacture. Studies of the blades damaged in operation, revealed that despite the control and rejection of blades in the manufacture, the materials of the turbine blades installed on aircraft engines, contain casting defects. The revealed casting defects are shown to affect the strength characteristics and durability of turbine blades and contribute to their destruction through fatigue fracture in operation. The special features of the quality characteristics of the single-crystal turbine blades, affecting their performance, and defects that contribute to their destruction in operation are highlighted. The necessity of improving the valuation, standardization and quality control both at the stages of design and manufacture of blades is shown.
Tesi sul tema "BLADE STRUCTURAL CHARACTERISTICS"
1
Heath, Steven. "A study of tip-timing measurement techniques for the determination of bladed-disk vibration characteristics". Thesis, Imperial College London, 1997. http://hdl.handle.net/10044/1/44221.
Testo completoAbstract (sommario):
All turbomachinery blades experience vibration under operating conditions. Given that theoretical tools are often limited in producing reliable quantitative predictions, most engine development certification programs still rely on contacting vibration measurements. The main objective of this research work is the development of robust and validated real-time data analysis procedures for vibration signals captured on rotating assemblies using non-contacting optical probes. This process is referred to as blade tip-timing and was broken down into two distinct steps, first, vibration parameter derivation from blade passing times at the optical probes and second, processing of this parameter to characterise the blade vibration, the second step forming the main part of the work reported. It was decided to focus on synchronous assembly response, though a chapter has been dedicated to asynchronous response. There are established procedures for the characterisation of the latter whilst the accurate identification of the former is a long-standing problem. A multi-degree-of-freedom numerical simulator, which includes the bladed-disk assembly properties, the external forcing terms and the characteristics of the optical probe, was developed to assess the reliability of the various data processing techniques to identify the vibration characteristics of bladed-disk assemblies. The inherent limitations of the existing data analysis techniques were discussed and new approaches were suggested. A method for identifying the resonance frequency using two probes was introduced. The proposed method was shown to be easy to use and its robustness was discussed for a range of cases, including relatively high resonance amplitudes, the presence of close modes and blade mistuning. Further direct and indirect analysis methods were developed by considering up to four probes. The real-time implementation of the four-probe algorithm was performed using a transputer network and it was concluded that dual processor TRAMs are required for the benefits of parallel processing architectures and fast floating point calculations to be achieved. The work reported in this thesis has led to development of three new robust synchronous response analysis techniques and it has been shown that blade vibration characteristics can be satisfactorily identified using a minimum of four measurements at the same axial position.
2
Marsh, PJ. "The hydrodynamic and structural loading characteristics of straight and helical-bladed vertical axis tidal and current flow turbines". Thesis, 2015. https://eprints.utas.edu.au/23169/2/Marsh_whole_thesis_ex_pub_mat.pdf.
Testo completoAbstract (sommario):
Vertical axis cross flow tidal and current flow turbines are proposed to generate electrical
energy from the ocean's kinetic energy, however little is known of their performance and
loading characteristics. In this work, fixed pitch straight and helical-bladed vertical axis
turbines were investigated using numerical simulation models to perform examinations of
the influence of geometrical layout and rotational rate on power output, torque fluctuations,
mounting forces, structural stress, and deflection magnitudes. These studies were conducted
to establish the relative merits of various turbine configurations, including variations in strut
section, strut-blade mounting tab design, strut location, as well as varying degrees of blade
helicity and section angle inclination. To establish performance and loading parameters,
transient Computational Fluid Dynamics (CFD) and Double Multiple Streamtube (DMS)
hydrodynamic simulation models were developed, which were then coupled with structural
models using beam theory and Finite Element Analysis (FEA) techniques. Extensive verification and validation of the hydrodynamic results against Experimental Fluid Dynamics
(EFD) results from literature for turbines of differing geometrical layouts was performed to
ensure simulation accuracy.
Simulation results show that numerical models can accurately simulate performance when
compared to EFD results if suitable modelling techniques are utilised. The results show
that significant differences in performance characteristics such as power output and mount-
ing force magnitudes occur for turbines with differing geometrical layouts. Straight-bladed
turbines were found to generate higher power output, torque fluctuation levels, mounting
forces, structural stress, and defection magnitudes than helical turbines of the same frontal
area, as a result of the blade inclination of the helical turbine to the inflow. The influence of
strut design on power output was also significant, with low-drag struts located at the blade
tips generating the highest power output when compared to turbines with high-drag struts
located at the quarter-span location. For both straight and helical turbines the highest
stress magnitudes were found at the blade-strut joints. Overall these results demonstrate
that straight-bladed turbines are better suited for harnessing tidal and current flow ocean
energy than helical-bladed turbines, as they generate higher power outputs whilst not incurring any significantly adverse structural penalties. These results are significant as previous numerical simulation and EFD works have concentrated on each configuration individually, with little known of their respective merits.
The numerical models developed as part of this work are capable of accurately capturing
the complex behaviour of vertical axis turbines for differing geometrical layouts, allowing for
future design investigations to be conducted without the need for EFD. The development of
these models, and the inclusion of suggested simulation guidelines in this work, has created
a useful design toolbox for future use that is suitable for turbine optimisation studies as well
as coupling with fatigue evaluations to ensure turbine longevity.
3
Chen, Jyun-Yu, e 陳俊羽. "Combined Experimental and Numerical Study on the Flow Structure and Aerodynamic Characteristics of the Wavy Leading-edge Blade Applied on the VAWT". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/92sdgs.
Testo completoAbstract (sommario):
碩士國立虎尾科技大學
飛機工程系航空與電子科技碩士班
105
Humpback whales utilize extremely mobile, wing-like flipper for banking and turning. The tubercles on the leading edge act as passive-flow control devices that improve performance and maneuverability of flipper. Theexperiment and 3-D numerical simulation are performed in this study to thoroughly investigate the flow structure and aerodynamic characteristics of 3-blade VAWT applyingthe designed wavy wing with different amplitude, wave lengthand aspect ratio, which is simulated from the tubercles flipper on humpback whales. For the static single blade cases withV∞=12m/s, the flow separation is stronger at the wave trough than at the wave crest due to the counter-rotating vortex induced by the flow pass through the wavy leading edge. Comparing with the smooth leading edge, the lift coefficient of wavy wing is lower in low angle of attack, but is superior at higher angle of attack. The effect of the wavy wing strongly depends on the wave length and amplitude of the wavy leading edge. For higher wave length cases, the average lift is rise as amplitude isincreased. Similarly, the improvement is more obvious for lower wave length case as amplitude is decreased. For the three blades vertical axis wind turbine cases withV∞=6m/s, R/c=1.726, 0.05c ≦ A ≦to 0.3c, 0.5c≦ WL ≦ to 3c and tip speed ratio 0.095≦ TSR≦1,the wind turbineperformance of wavy wing is obviouslyimproved.Comparing with the smooth leading edge, the maximum average torque coefficient CQ enhancement of wavy wing with amplitude variationare20.02%, 22.66%, 26.05%, 19.15%, 16.72%, 6.91% as TSR=0.095, 0.191, 0.287, 0.383, 0.5, 1 respectively.The maximum average torque coefficient CQ enhancement of wavy wing with wave length variationare23.89%, 22.23%, 13.52%, 12.71%, 12.56%, -0.29% as TSR=0.095, 0.191, 0.287, 0.383, 0.5, 1 respectively. The wind turbine power analysis also implemented with numerical simulation and wind tunnel measurement. Comparing with the smooth leading edge, the maximum power enhancement of wavy wing with amplitude variationare40.05%, 39.63%, 24.91%, 22.02% as TSR=0.05, 0.06, 0.07, 0.08 respectively with numericalsimulation; and the enhancements are40.31%, 44.65%, 37.34%, 48.88% as TSR=0.05, 0.06, 0.07, 0.08 respectivelywith wind tunnel measurement.
Libri sul tema "BLADE STRUCTURAL CHARACTERISTICS"
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Lake, Renee C. Experimental and analytical investigation of dynamic characteristics of extension-twist-coupled composite tubular spars. Hampton, Va: Langley Research Center, 1993.
Cerca il testo completoCapitoli di libri sul tema "BLADE STRUCTURAL CHARACTERISTICS"
1
Sydorenko, Ihor, Vladimir Tonkonogyi, Yuliia Babych, Yuliia Barchanova e Zhang Yiheng. "Operating Characteristics of Lever-Blade Shock Absorbers with the Extended Mechanical Structure". In Advances in Design, Simulation and Manufacturing III, 95–104. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-50491-5_10.
Testo completo
2
Lu, Xuxiang, Wenjun Huang, Luping Li e Shuhong Huang. "Damping Vibration Characteristics of Frictional Damping Structure in Steam Turbine Integrally Shrouded Blades". In Challenges of Power Engineering and Environment, 320–23. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-76694-0_57.
Testo completo
3
Hu, Shan Shan, Ying Ning Hu, Cheng Yong Wang e Chang Xiong Chen. "Vibration Characteristic Analysis of Diamond Saw Blade with Multitude Holes Structure for Vibration and Noise Reduction". In Advances in Grinding and Abrasive Technology XIV, 78–84. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-459-6.78.
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Li, Lu, Chenhao Li, Xingqi Luo, Jianjun Feng e Guojun Zhu. "Effect of Radial Guide Vane Optimization on the Performance of Multistage Centrifugal Pump". In Advances in Transdisciplinary Engineering. IOS Press, 2022. http://dx.doi.org/10.3233/atde220951.
Testo completoAbstract (sommario):
The optimization of radial guide vane structure is the key measure to reduce the hydraulic loss of the component. The research model for this paper is a multistage centrifugal pump with a radial guide vane. Based on the SST k–ω turbulence model and using CFD numerical simulation technology to imitate and forecast multistage pump performance. The influences of radial guide vane blade numbers and return guide vane circumferential distribution position optimization on the multistage pump transportability are studied. The internal fluidity characteristics and transport performance of multistage centrifugal pumps with different guide vane structures are obtained. The results show that the hydraulic efficiency increases by 1.11% when the number of return guide blades is 9. When the return guide vane rotated 8° axially, had best performance optimization result, the efficiency and head of centrifugal pump are increased by 0.54% and 1.54% respectively. The change of circumferential distribution position will increase the ratio of hydraulic loss of radial guide vane, while the ratio of hydraulic loss of volute decreases. The research results can provide reference for radial guide vane optimal design of multistage centrifugal pump.
5
Yamashita, Y., K. Shiohata, T. Kudo e H. Yoda. "Vibration characteristics of a continuous cover blade structure with friction contact surfaces of a steam turbine". In 10th International Conference on Vibrations in Rotating Machinery, 323–32. Elsevier, 2012. http://dx.doi.org/10.1533/9780857094537.4.323.
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Del Percio, Enrique. "Argentina: The Philosophical Resistance to the Conquest of the Soul1". In A Post-Neoliberal Era in Latin America?, 159–76. Policy Press, 2019. http://dx.doi.org/10.1332/policypress/9781529200997.003.0008.
Testo completoAbstract (sommario):
In 1976, a terrible dictatorship was established in Argentina, even before Foucault claimed with crystal clarity that the fundamental difference between classical liberalism and neoliberalism was the substitution of the homo economicus −related to the exchange− by the homo economicus as entrepreneur of himself (lecture delivered on 14 March 1979); and also before Margaret Thatcher (in Ronald Butt’s interview, Sunday Times, 3 May 1981) confirmed Foucault´s analysis stating that: “Economics are the method; the object is to change the heart and soul”. In the same year, Milton Friedman received the Nobel Prize in Economics. The explicit purpose of the Military Junta was to promote a profound cultural transformation, based on the premise that the causes of the alleged “underdevelopment” were not so much economical but cultural and political. Nevertheless, as García Delgado and Molina (2006) pointed out, the problem is not related to a sort of inevitable structural poverty, due to the culture of our people. It is a matter of a decline in society, produced by the policy orientation of the dictatorship. Until then, the income distribution was similar to that of the countries from the Southern Europe with an almost frictional unemployment. Until the coup d’état, Argentina had a poverty rate of 8% and the best distributive structure of income in Latin America. However, 1976 was a turning point; the surge of the neoliberal model promoted a process of over-indebtedness, wealth concentration, unrestricted opening of markets with an unfavourable exchange rate for national industry, labour flexibilization, with the insertion in a competitive globalization of “savage capitalism” that “strengthened the asymmetries and transfers of resources from the periphery to the centre. This concept differs from thinking about inequality as a problem related to culture, corruption and poor institutional quality” (García Delgado, 2006).Despite the overwhelming adverse evidence, it is still a commonplace to blame all the ills of our society on that culture, the maximum expression of which would be Peronism. In fact, the great majority of disappeared people during the dictatorship were Peronist political, trade union and social leaders. The motto of the Ministry of Economics during the dictatorship was “towards a change of mentality”. The current Argentine situation, in terms of advances of neoliberalism as well as resistances to it, cannot be understood without referring to the dictatorship. In Poratti words, “the coup d’état of 1976 does not only put an end to a government, a political system and project, but also to a 'world' in which Argentinians were living at least from the independence project of 1810. In those days, there was not an abrupt differentiation between generations and, in many aspects, people could identify themselves, diachronically, with a historical line beyond the particular generational characteristics” (Various Authors, 2009).These aspects go along with others that appeared in other areas, such as the implementation of new computer and communication technologies and, as a consequence, individual and social fragmentation. The impact of these technologies on daily life was decisive to the emergence of what some authors, like Sloterdijk (2002), called “mass individualism.” No doubt, this is a necessary aspect to explain the rise of the neoliberal subjectivity in developed countries. Yet, in Argentina, the existence of political, social, trade-union and ecclesiastical movements based on popular roots, with solidarity as a fundamental value, hampered the conquest of the “heart and soul” in 1976; and they are still now an obstacle to be overcome by sectors interested in imposing a neoliberal model. It is impossible to explain any isolated phenomenon of popular resistance to the hegemonic attempts from neoliberalism without analysing the common conceptions and understandings found in Argentina. Indeed, the popular culture substrate in Argentina is made up, mainly, by the confluence of different cultures: Andean, Guaraní Indians, Afro and Criollo (native). All of them are characterized by their relational and solidarity conceptions, intrinsically opposed to a subjectivity that conceives the individual as an entrepreneur of himself/herself.
Atti di convegni sul tema "BLADE STRUCTURAL CHARACTERISTICS"
1
PIERRE, CHRISTOPHE, e DURBHA MURTHY. "Aeroelastic modal characteristics of mistuned blade assemblies - Mode localization and loss of eigenstructure". In 32nd Structures, Structural Dynamics, and Materials Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1991. http://dx.doi.org/10.2514/6.1991-1218.
Testo completo
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Desmond, Michael, e Darris White. "Predictions of Structural Testing Characteristics for Wind Turbine Blades". In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12288.
Testo completoAbstract (sommario):
Static and fatigue structural testing of wind turbine blades provides manufacturers with quantitative details in order to improve designs and meet certification requirements. Static testing entails applying extreme load cases through a combination of winches and weights to determine the ultimate strength of the blade while fatigue testing entails applying the operating design loads through forced hydraulics or resonant excitation systems over the life cycle of the blade to determine durability. Recently, considerable efforts have been put forth to characterize the reactions of wind turbine blades during structural testing in order to develop load and deflection predictions for the next generation of blade test facilities. Incorporating years of testing experience with historical test data from several wind turbine blades, curve fits were developed to extrapolate properties for blades up to one hundred meters in length. Furthermore, conservative assumptions were employed to account for blade variations due to inconsistent manufacturing processes. In short, this paper will outline the predictions of wind turbine blade loads and deflections during static and fatigue structural testing.
3
Min, James, Donald Harris e Joseph Ting. "Advances in Ceramic Matrix Composite Blade Damping Characteristics for Aerospace Turbomachinery Applications". In 52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2011. http://dx.doi.org/10.2514/6.2011-1784.
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Satish Kumar, Subramani, Ranjan Ganguli, Siddanagouda Basanagouda Kandagal e Soumendu Jana. "Structural Dynamic Behavior of Axial Compressor Rotor". In ASME 2017 Gas Turbine India Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gtindia2017-4715.
Testo completoAbstract (sommario):
The vibrations involved in a typical axial compressor rotor in an aircraft engine are complex. Generally, the compressor blades are arranged in a cantilever type configuration. It is also known that the amplitude of vibration is highest near the tip section of the shroudless blade. Compressors are limited by aerodynamic instabilities such as rotating stall and surge. Rotating stall generally initiates near the tip region of the compressor. Blade vibrations coupled with aerodynamic instabilities will lead to a catastrophic scenario of flutter that is asynchronous to the rotor speed. This aeroelastic interaction is detrimental if not taken into consideration. Knowledge of vibration characteristics of the compressor rotor will help in mapping the flutter zone for safe operation. The modal characteristics of the transonic axial compressor rotor available at the Axial Flow Compressor Research (AFCR) facility of National Aerospace Laboratories (NAL) are established in this study. A cyclic-symmetric pre-stressed modal analysis is performed on a single sector of the compressor rotor consisting of a shroudless blade connected to the disk with a pin type dovetail arrangement for different speeds. The main diagnostic charts for turbomachinery vibration i.e., Campbell and Interference diagrams are generated for various speeds and harmonic indices/ nodal diameters of the compressor rotor. The critical crossings of the engine order excitation lines over the natural frequencies of the blade are highlighted. Experimental modal investigations and analysis are carried out on the compressor rotor at the stationary condition and for two different boundary conditions. First, the blade alone modal characteristics under the free-free condition are established. Later, the complete blade-disk assembly mounted on a base test-stand is used to investigate the cantilever fixed-free boundary condition of the chosen blade. The modal characteristics are established by performing impact hammer experiments. Blade excitation is provided by a calibrated Dytran make impact hammer and the response is measured using a calibrated accelerometer. The structural dynamic data acquisition hardware and software from OROS is used for determining the natural frequencies, mode shapes and structural damping for each mode of the compressor rotor. There is a good agreement in the natural frequencies and mode shapes established using experiment and numerical methods for the first three modes investigated. Modal Assurance Criteria (MAC) analysis is carried out for two different modal identification algorithms to compare the mode shapes.
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Akiyama, Ryou, Koki Shiohata, Tomomi Nakajima e Yutaka Yamashita. "Damping Characteristics of Non-Synchronous Turbine Blade Vibration". In ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/detc2015-46416.
Testo completoAbstract (sommario):
In order to analyze turbine blades vibration caused by flutter, it is necessary to understand both aerodynamic damping and structural damping of high vibration stress. Flutter Vibration mode occurring in rated speed is non-synchronous mode. For measuring non-synchronous mode damping ratio of turbine blades, AC-type electromagnet which can generate high frequency excitation force was developed. Damping ratio characteristics of non-synchronous mode of nodal diameter 12,4 was measured in rotational test. For comparison, synchronous mode of nodal diameter 4 was measured, too. It was concluded as follows. (1) It is possible to excite non-synchronous mode by high frequency excitation electromagnet and calculate damping ratio from measurement resonance curve. (2) Damping ratio of non-synchronous mode ND12,4 was increased by increasing the excitation force. Synchronous mode ND4 is also a similar trend. (3) Nodal diameter 4 damping ratio of non-synchronous mode (Resonant speed=100%) was lower than synchronous mode (Resonant speed=75%).
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Liang, Daosen, Rui Zhang, Yulin Wu, Zichu Jia, Zhifu Cao e Jianyao Yao. "High fidelity finite element model updating and deviation characterization method for geometric mistuned bladed disks". In GPPS Xi'an21. GPPS, 2022. http://dx.doi.org/10.33737/gpps21-tc-360.
Testo completoAbstract (sommario):
To accurately obtain the influence of geometric deviation on the vibration characters of the bladed disk. It is necessary to count the deviation characteristics of a large number of real bladed disks and establish the highfidelity structural analysis model. An automatic finite element model updating method of mistuned blade disks and characterization method of blade geometric deviation is proposed in this paper. The geometric mistuning blade finite element model is obtained by moving the finite element structured mesh nodes to the measured point cloud data. The proposed finite element model updating method includes bladed disk cloud processing, blade surface classification, blade node movement. The method can be applied to large deformed blades and damaged blades. The obtained geometric deviation can accurately distinguish the abnormal blade model. The surface measurement data of the blade is obtained by a blue light optical scanner. Compare with the blade modal experiments result, the updated highfidelity finite element calculation result error was less than 8‰.
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Försching, H. "A Parametric Study of the Flutter Stability Characteristics of Turbomachine Cascades". In ASME 1996 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-gt-260.
Testo completoAbstract (sommario):
A parametric study of the unstalled flutter stability characteristics of compressor and turbine cascades in subsonic and supersonic flow is carried out. Based on typical section two-dimensional cascade models, stability boundaries and dominant trends in flutter behaviour are outlined with emphasis on the effects of (a) single mode structural coupling in bending and torsion, (b) coupling among multiple blade degrees of freedom, (c) mass ratio and structural damping, (d) compressibility, (e) cascade solidity and stagger, and (f) steady aerodynamic blade loading. Practical design aspects are in the foreground of all of these investigations.
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Zhang, Mingming, Anping Hou, Sheng Zhou e Xiaodong Yang. "Analysis on Flutter Characteristics of Transonic Compressor Blade Row by a Fluid-Structure Coupled Method". In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-69439.
Testo completoAbstract (sommario):
A time domain numerical approach is carried out to enhance the understanding of three dimensional blade row aeroelastic characteristics under the parallel computation. The vibration energy of unsteady aerodynamic force on the entire blade row is investigated using numerical solution of 3-D Navier-Stokes equations, coupled with structure finite element models for the blades to identify modal shapes and the structural deformations simultaneously. Interactions between fluid and structure are dealt with in a coupled manner, based on the interface information exchange until convergence in each time step. With this approach good agreement between the numerical results and the experimental data is observed. The flutter mechanism is analyzed according to deformation of the blades. The effect of inter-blade phase angle (IBPA) is included in the analysis by releasing the hypothesis of constant phase angle between adjacent blades in the traveling wave model. The results illustrate fully three dimensional unsteady nonlinear behaviors, such as limit-cycle oscillation. It is shown that all blades flutter at the same mode and frequency, but not at the same amplitude and IBPA. The analysis of the influence of different tip clearance gaps on the flutter characteristics of the blade row is also performed.
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Heath, Steve, e Mehmet Imregun. "Determination of Rotating Assembly Synchronous Response Characteristics Using Blade Tip-Timing Techniques". In ASME 1995 Design Engineering Technical Conferences collocated with the ASME 1995 15th International Computers in Engineering Conference and the ASME 1995 9th Annual Engineering Database Symposium. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/detc1995-0534.
Testo completoAbstract (sommario):
Abstract This paper presents an improved analysis method for the interpretation of the vibration data measured at turbomachinery blade tips using optical laser probes. A multi-degree-of-freedom numerical simulator, which includes the structural and geometric properties of the bladed-disk assembly, the external forcing terms and the characteristics of the optical probe, has been developed to assess the reliability of the various data processing techniques to identify the natural frequencies and mode shapes of bladed-disk assemblies. It has been demonstrated that the Zablotsky-Korostelev single parameter technique, which is a de-facto standard in the aerospace industries, has inherent limitations associated with it. An improved and more rigorous method is presented for deriving the blade arrival times and a non-linear solution technique is suggested for their numerical determination. Finally, the effect of blade mistuning on the accuracy of the proposed method is also investigated.
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Mignolet, Marc P., e Alejandro Rivas-Guerra. "Identification of Mistuning Characteristics of Bladed Disks From Free Response Data". In ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/98-gt-583.
Testo completoAbstract (sommario):
The focus of the present investigation is on the estimation of the dynamic properties, i.e. masses, stiffnesses, natural frequencies, mode shapes and their statistical distributions, of turbomachine blades to be used in the accurate prediction of the forced response of mistuned bladed disks. As input to this process, it is assumed that the lowest natural frequencies of the blades alone have been experimentally measured, for example in a broach block test. Since the number of measurements is always less than the number of unknowns, this problem is indeterminate in nature. Two distinct approaches will be investigated to resolve the shortfall of data. The first one relies on the imposition of as many constraints as needed to insure a unique solution to this identification problem. Specifically, the mode shapes and modal masses of the blades are set to their design/tuned counterparts while the modal stiffnesses are varied from blade-to-blade to match the measured natural frequencies. The second approach, based on the maximum likelihood principle, yields estimates of all the structural parameters of the blades through the minimization of a specified “cost function”. The accuracy of these two techniques in predicting the forced response of mistuned bladed disks will be assessed on simple dynamic models of the blades.