Letteratura scientifica selezionata sul tema "Slow rotating bearings"
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Articoli di riviste sul tema "Slow rotating bearings"
1
Morales-Espejel, G. E., P. M. Lugt, H. R. Pasaribu e H. Cen. "Film thickness in grease lubricated slow rotating rolling bearings". Tribology International 74 (giugno 2014): 7–19. http://dx.doi.org/10.1016/j.triboint.2014.01.023.
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2
Jamaludin, N., D. Mba e R. H. Bannister. "Condition monitoring of slow-speed rolling element bearings using stress waves". Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 215, n. 4 (1 novembre 2001): 245–71. http://dx.doi.org/10.1177/095440890121500401.
Testo completoAbstract (sommario):
Condition monitoring of rolling element bearings through the use of vibration analysis is an established technique for detecting early stages of component degradation. However, this success is not mirrored at rotational speeds below 16r/min. At such speeds the energy generated from bearing defects might not show as an obvious change in signature and thus becomes undetectable using conventional vibration measuring equipment. This paper presents an investigation into the applicability of stress wave analysis for detecting early stages of bearing damage at a rotational speed of 1.12r/min (0.0187 Hz). Furthermore, it reviews work undertaken in monitoring bearings rotating at speeds below 16r/min.
3
Elforjani, Mohamed. "Diagnosis and prognosis of slow speed bearing behavior under grease starvation condition". Structural Health Monitoring 17, n. 3 (28 aprile 2017): 532–48. http://dx.doi.org/10.1177/1475921717704620.
Testo completoAbstract (sommario):
The monitoring and diagnosis of rolling element bearings with acoustic emission and vibration measurements has evolved as one of the much used techniques for condition monitoring and diagnosis of rotating machinery. Furthermore, recent developments indicate the drive toward integration of diagnosis and prognosis algorithms in future integrated machine health management systems. With this in mind, this article is an experimental study of slow speed bearings in a starved lubricated contact. It investigates the influence of grease starvation conditions on detection and monitoring natural defect initiation and propagation using acoustic emission approach. The experiments are also aimed at a comparison of results acquired by acoustic emission and vibration diagnosis on full-scale axial bearing. In addition to this, the article concentrates on the estimation of the remaining useful life for bearings while in operation. To implement this, a multilayer artificial neural network model has been proposed to correlate the selected acoustic emission features with corresponding bearing wear throughout laboratory experiments. Experiments confirm that the obtained results were promising and selecting this appropriate signal processing technique can significantly affect the defect identification.
4
Nienhaus, K., F. D. Boos, K. Garate e R. Baltes. "Development of Acoustic Emission (AE) based defect parameters for slow rotating roller bearings". Journal of Physics: Conference Series 364 (28 maggio 2012): 012034. http://dx.doi.org/10.1088/1742-6596/364/1/012034.
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Belfiore, Nicola Pio, Carlo Costa, Rosanna Pileggi, Fabio Botta e Claudio Guarnaschelli. "An accelerated test stand to assess wear in offshore wind turbines rolling bearings". Wind Engineering 42, n. 2 (16 febbraio 2018): 136–40. http://dx.doi.org/10.1177/0309524x18756963.
Testo completoAbstract (sommario):
Rolling bearings are universally adopted to serve as revolute joints in almost all mechanisms or machines, because they offer a convenient solution to the problem of minimizing friction and, simultaneously, providing a large load-carrying capacity at any kinematic regime, including slow or alternate rotations. However, in offshore wind turbines not only they reach large dimensions but also they move within strong electromagnetic fields created by the turbine generators. For example, considering the last amplification stadium epicyclic gearbox, they may serve to sustain elements rotating around floating shafts (planetary) which also move around a fixed principal shaft (solar). This article illustrates an original experimental test bench that simulates sliding and rolling contacts through which a test current is flowing. Unexpected and interesting results disclose how this particular field is challenging and how more investigations are still required to achieve an adequate and complete interpretation. The understanding of this phenomenon could give rise to modification to the composition and the microstructure of rollers and rings employed in offshore wind turbines.
6
Chiementin, Xavier, Fabrice Bolaers e Jean-Paul Dron. "Early Detection of Fatigue Damage on Rolling Element Bearings Using Adapted Wavelet". Journal of Vibration and Acoustics 129, n. 4 (19 marzo 2007): 495–506. http://dx.doi.org/10.1115/1.2748475.
Testo completoAbstract (sommario):
Among the advanced techniques of the predictive maintenance, the vibratory analysis proves to be very effective, in particular, for monitoring rotating components such as the bearings. Their damage creates cyclic efforts which are at the origin of the processing of vibratory measurements. This processing can be made by temporal methods, frequential methods, or by time-scale methods using the wavelets for 2 decades. The wavelet transform is a very effective processing, however, the difficulties of application and interpretation of the results slow down their employment. The determination of the parameters of the wavelets makes its use all the more difficult. Moreover, the use of these time-scale methods is very expensive in time computation. This paper proposes a wavelet adapted to the mechanical shock response of a structure with n degrees of freedom. In addition, we developed a procedure for analysis of signals by this wavelet which makes it possible to accelerate the process and to improve detection in the case of disturbed signals. This methodology is compared with the traditional time-scale methods and is implemented to detect defects of different sizes on outer rings and inner rings of ball bearings.
7
Qiu, Li Jun, Jia Yang e Su Ying Xu. "The Analysis and Design of Turbocharger Thrust Bearing". Advanced Materials Research 308-310 (agosto 2011): 1333–36. http://dx.doi.org/10.4028/www.scientific.net/amr.308-310.1333.
Testo completoAbstract (sommario):
Turbocharger turbine shaft thrust bearing is the role of high-speed rotating turbine to withstand the axial force generated by the turbine shaft and a part of the axial position. Fixed on the intermediate thrust bearing on the two sides and both sides of the ring, respectively, relative sliding. Sliding contact surface produces a condition of dynamic pressure oil film structure and shape of the oil wedge. Bearing the sides of the structural design of the oil wedge slot and forming a design to solve the main content. Bearing thrust bearing stiffness and rotation in the process of stress state and the smooth line is to improve the bearing life. Rotating turbine shaft to ensure the accuracy of key factors. Method of lubricating oil to the oil and oil Xie in the shape and precision bearings to ensure the prerequisite conditions and service life.
8
Liu, Jiao, Zheng Lin Liu, Xiang Kun Meng e Xing Xin Liang. "Study on the Performance of Water Lubricated Stern Tube Bearing Based on Fluent". Applied Mechanics and Materials 496-500 (gennaio 2014): 692–96. http://dx.doi.org/10.4028/www.scientific.net/amm.496-500.692.
Testo completoAbstract (sommario):
Apply FLUENT software to establish the water lubricated rubber stern tube bearing CFD model,study temperature and pressure distribution of the bearings at different speeds of rotation. It plays an important role in improving the performance of ship water lubricated stern tube bearing and security, reliability of propulsion system. The simulation results show that increasing the shaft speed in a certain range can reduce water film temperature, the effect is obvious especially at slow entrance velocity of bearings. Both high and low pressure ranges in the middle of bearings are enlarged with the increase of speed.
9
Gębura, Andrzej. "Investigation Of Tribologic Processes in Bearing Nodes with the Use of the Fam-C And Fdm-A Methods – The Model With Elevated Passive Resistance". Research Works of Air Force Institute of Technology 35, n. 1 (1 dicembre 2014): 115–25. http://dx.doi.org/10.1515/afit-2015-0008.
Testo completoAbstract (sommario):
Abstract The paper discloses selected results of application of the FAM-C (a.c. generator) and FDM-A (d.c. generator) methods for comprehensive troubleshooting of bearing nodes in single-spool turbojet engines. A.c. generators provide information about slow-changing processes and, consequently, that information makes it possible to monitor radial and axial clearance of bearings as well as misalignment of shafts. On the other hand, the information transmitted by d.c. generators refers to fast-changing processes and is suitable to monitor dynamic properties of antifriction bearings: variations in the Q factor of bearings, slip factor of mating antifriction surfaces, rates of bearing cage rotation against its journal, etc. Nearly ten years of observations and data collection from a numerous set of engines during their operation have made it possible to classify processes associated with wear of bearings and categorize them into four phenomenological models. This paper is devoted to the model of elevated passive resistance
10
Barkova, N. A., A. V. Barkov, V. V. Fedorishchev e D. V. Grishchenko. "Bearing diagnostics of slow speed industrial rotating equipment by shock pulses". IOP Conference Series: Materials Science and Engineering 643 (13 novembre 2019): 012026. http://dx.doi.org/10.1088/1757-899x/643/1/012026.
Testo completoTesi sul tema "Slow rotating bearings"
1
Aye, S. A. (Sylvester Aondolumun). "Acoustic emission-based diagnostics and prognostics of slow rotating bearings using Bayesian techniques". Thesis, 2014. http://hdl.handle.net/2263/43129.
Testo completoAbstract (sommario):
Diagnostics and prognostics in rotating machinery is a subject of much on-going
research. There are three approaches to diagnostics and prognostics. These include
experience-based approaches, data-driven techniques and model-based techniques.
Bayesian data-driven techniques are gaining widespread application in diagnostics
and prognostics of mechanical and allied systems including slow rotating bearings, as
a result of their ability to handle the stochastic nature of the measured data well. The
aim of the study is to detect incipient damage of slow rotating bearings and develop
diagnostics which will be robust under changing operating conditions. Further it is
required to explore and develop an optimal prognostic model for the prediction of
remaining useful life (RUL) of slow rotating bearings.
This research develops a novel integrated nonlinear method for the effective feature
extraction from acoustic emission (AE) signals and the construction of a degradation
assessment index (DAI), which is subsequently used for the fault diagnostics of slow
rotating bearings. A slow rotating bearing test rig was developed to measure AE data
under variable operational conditions. The proposed novel DAI obtained by the
integration of the PKPCA (polynomial kernel principal component analysis), a
Gaussian mixture model (GMM) and an exponentially weighted moving average
(EWMA) is shown to be effective and suitable for monitoring the degradation of slow
rotating bearings and is robust under variable operating conditions. Furthermore, this
study integrates the novel DAI into alternative Bayesian methods for the prediction of
RUL. The DAI is used as input in several Bayesian regression models such as the multi-layer perceptron (MLP), radial basis function (RBF), Bayesian linear regression
(BLR), Gaussian mixture regression (GMR) and the Gaussian process regression
(GPR) for RUL prediction. The combination of the DAI with the GPR model,
otherwise, known as the DAI-GPR gives the best prediction. The findings show that
the GPR model is suitable and effective in the prediction of RUL of slow rotating
bearings and robust to varying operating conditions. Further, the models are also
robust when the training and tests sets are obtained from dependent and independent
samples.
Finally, an optimal GPR for the prediction of RUL of slow rotating bearings based on
a DAI is developed. The model performance is evaluated for cases where the training
and test samples from cross validation approach are dependent as well as when they
are independent. The optimal GPR is obtained from the integration or combination of
existing simple mean and covariance functions in order to capture the observed trend
of the bearing degradation as well as the irregularities in the data. The resulting
integrated GPR model provides an excellent fit to the data and improvements over the
simple GPR models that are based on simple mean and covariance functions. In
addition, it achieves a near zero percentage error prediction of the RUL of slow
rotating bearings when the training and test sets are from dependent samples but
slightly different values when the estimation is based on independent samples. These
findings are robust under varying operating conditions such as loading and speed. The
proposed methodology can be applied to nonlinear and non-stationary machine
response signals and is useful for preventive machine maintenance purposes.
Keywords: acoustic emission, Bayesian linear regression, Bayesian techniques,
covariance function, data-driven, degradation assessment index, diagnostics,
experience-based, exponentially weighted moving average, Gaussian mixture model,
Gaussian mixture regression, Gaussian process regression, integration, mean function,
model-based, multi-layer perceptron, polynomial kernel principal component
analysis, prognostics, radial basis function, remaining useful life.Thesis (PhD)--University of Pretoria, 2014.
lk2014
Mechanical and Aeronautical Engineering
PhD
unrestricted
Capitoli di libri sul tema "Slow rotating bearings"
1
Aye, Sylvester A., P. Stephan Heyns e Coenie J. H. Thiart. "Diagnostics of Slow Rotating Bearings Using a Novel DAI Based on Acoustic Emission". In Applied Condition Monitoring, 321–33. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-20463-5_24.
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2
Adams, Maurice L. "Large Steam Turbine Generator Turning-Gear Slow-Roll Journal Bearing Load Capacity". In Rotating Machinery Research and Development Test Rigs, 37–48. Boca Raton : Taylor & Francis, CRC Press, [2017]: CRC Press, 2017. http://dx.doi.org/10.1201/9781315116723-3.
Testo completoAtti di convegni sul tema "Slow rotating bearings"
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Kallappa, Pattada, Carl Byington e Bryan Donovan. "Fault Detection and Lubricant Health Monitoring for Slow Bearings in Extreme Operating Conditions". In World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-64019.
Testo completoAbstract (sommario):
Slow rotating bearings are an integral part of aerospace and turbomachinery actuation systems. These actuation systems may be driven by electric, hydraulic or fueldraulic power and often operate under high loads and extreme temperatures. This makes these actuation systems and their slow rotating bearings highly susceptible to degradation and failure. Vibration monitoring techniques are not applicable to the PHM of these bearings, because their slow speeds are unable to produce a measureable vibration signature. Furthermore, the slow bearings are sealed and use grease lubrication, thus eliminating traditional oil debris monitoring. To address these problems, Impact Technologies, LLC has developed a PHM system that relies on system identification and uses available control system data and sensor measurements. This PHM system consists of algorithms and models that perform fault detection and identification for the bearings and its actuation train components like valves, pumps, motors, gears and bearings. The PHM process is divided into two stages — diagnostics and prognostics. Diagnostics is the process of detecting and isolating faults, while prognostics is the process of predicting remaining useful life (RUL) or time to failure. The authors demonstrate the PHM system through simulation on a dynamic model that is representative of hydraulic-mechanical actuation systems used in new and existing manned aircrafts, UAVs and Short Take-off and Vertical Landing aircrafts.
2
Chen, Fen, Quan Liu, Qin Wei, Deng Ting, Yan Ting, Su Wenqin, Peng Bingjie e Lei Zhao. "Fault Diagnosis of Rolling Bearings Based on Multi-Scale Entropy and Ensembled Artificial Neural Network". In ASME 2014 International Manufacturing Science and Engineering Conference collocated with the JSME 2014 International Conference on Materials and Processing and the 42nd North American Manufacturing Research Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/msec2014-4033.
Testo completoAbstract (sommario):
Rolling bearing is widely used in rotating mechanical system, and its operating state has great effects on availability, reliability and the life cycle of whole mechanical system. Therefore, fault diagnosis of rolling bearing is indispensable for the health monitoring in rotating machinery system. In this paper, a method based on multi-scale entropy (MSE) and ensembled artificial neural network (EANN) is proposed for feature extraction and fault recognition in rolling bearings respectively. MSE is mainly in charge for quantizing the complexity of the nonlinear time series in different scales. Then, EANN is employed to identify various faults of rolling bearing after overcoming the two disadvantages like local minimization and slow convergence speed in back propagation neural network (BPNN). The experimental results indicate that the method based on MSE and EANN is feasible and effective to classify different categories of faults and to identify the severity level of fault in the rolling bearings. Therefore, it is available for fault detection and diagnosis in rolling bearings with good performance.
3
Howard, Samuel A., e Luis San Andre´s. "A New Analysis Tool Assessment for Rotordynamic Modeling of Gas Foil Bearings". In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22508.
Testo completoAbstract (sommario):
Gas foil bearings offer several advantages over traditional bearing types that make them attractive for use in high-speed turbomachinery. They can operate at very high temperatures, require no lubrication supply (oil pumps, seals, etc), exhibit very long life with no maintenance, and once operating airborne, have very low power loss. The use of gas foil bearings in high-speed turbomachinery has been accelerating in recent years, although the pace has been slow. One of the contributing factors to the slow growth has been a lack of analysis tools, benchmarked to measurements, to predict gas foil bearing behavior in rotating machinery. To address this shortcoming, NASA Glenn Research Center (GRC) has supported the development of analytical tools to predict gas foil bearing performance. One of the codes has the capability to predict rotordynamic coefficients, power loss, film thickness, structural deformation, and more. The current paper presents an assessment of the predictive capability of the code, named XLGFBTH©. A test rig at GRC is used as a simulated case study to compare rotordynamic analysis using output from the code to actual rotor response as measured in the test rig. The test rig rotor is supported on two gas foil journal bearings manufactured at GRC, with all pertinent geometry disclosed. The resulting comparison shows that the rotordynamic coefficients calculated using XLGFBTH© represent the dynamics of the system reasonably well, especially as they pertain to predicting critical speeds.
4
San Andrés, Luis. "Extended Finite Element Analysis of Journal Bearing Dynamic Forced Performance to Include Fluid Inertia Force Coefficients". In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-87713.
Testo completoAbstract (sommario):
Reynolds equation governs the generation of hydrodynamic pressure in oil lubricated fluid film bearings. The static and dynamic forced response of a bearing is obtained from integration of the film pressure on the bearing surface. For small amplitude journal motions, a linear analysis represents the fluid film bearing reaction forces as proportional to the journal center displacements and velocity components through four stiffness and four damping coefficients. These force coefficients are integrated into rotor-bearing system structural analysis for prediction of the system stability and the synchronous response to imbalance. Fluid inertia force coefficients, those relating reaction forces to journal center accelerations, are routinely ignored because most oil lubricated bearings operate at relatively low Reynolds numbers, i.e., under slow flow conditions. Modern rotating machinery operates at ever increasing surface speeds to deliver more power in smaller size units. Under these operating conditions fluid inertia effects need to be accounted for in the forced response of oil lubricated bearings, as recent experimental test data also reveal. The paper presents a finite element formulation to predict added mass coefficients in oil lubricated bearings by extending a basic formulation that already calculates the bearing stiffness and damping force coefficients. That is, a small amplitude perturbation analysis of the lubrication flow equations keeps the temporal fluid inertia effects and develops a set of equations to obtain the bearing stiffness, damping and inertia force coefficients. The method does not impose on the cost of the original formulation which makes it very attractive for ready implementation in existing software. Predictions of the computational model are benchmarked against archival test data for an oil-lubricated pressure dam bearing supporting large compressors. The comparisons show fluid inertia effects cannot be ignored for operation at high rotor speeds and with small static loads.
5
Danieli, G. A., G. Fragomeni, D. Mundo e M. Vigna. "Proposal of a Bridge Deck Displacement Continuous Measuring Device and Periodical Realignment System Designed to Minimize Traffic Interruptions". In ASME 2002 Engineering Technology Conference on Energy. ASMEDC, 2002. http://dx.doi.org/10.1115/etce2002/struc-29004.
Testo completoAbstract (sommario):
The paper presents the most recent developments on electronic bridge control applied to a bridge located along a southern Italian Motorway in an area where a landslip is in slow yet continuous motion. A previous bridge was closed for beam misalignment caused by the landslip action. A new bridge was recently designed with much sturdier foundations, but even during the initial construction phases it was evident that a static solution was undesirable, if not impossible. Jet, based on the observations of the last twenty years, the foreseen movements are relatively small, 20 cm being the maximum horizontal measured displacement in that period. A further version of the bridge has thus been proposed, characterised by lighter and longer decks, in order to negotiate the section with fewer elements. Moreover, the monitoring and repositioning systems have been thoroughly redesigned, to allow an almost continuous adjustment of the bridge decks, severely limiting the realignment times, in order to reduce traffic interruptions. A reduced number of interferometric lasers have been used, using rotating drums with mirrors individually preset to sweep the entire measuring field. The lifters, in their present version, should substitute the props, being used as active connections between pillars and decks, thus being able to support all traffic induced dynamic stresses in the vertical direction. The lifters have also been made sturdier eliminating all ball bearings in favour of teflon sheets. In addition, computer controlled lateral supports have been added to the system, allowing to move the deck horizontally while transmitting traffic or hearth-quake shocks to the pillars. On the top of each lifter an elastic interface bearing strain gauges will enable the measurement of tangential stresses as well as uneven distribution of the load, providing further information on the need of beams realignment.
6
San Andre´s, Luis, e Keun Ryu. "On the Nonlinear Dynamics of Rotor-Foil Bearing Systems: Effects of Shaft Acceleration, Mass Imbalance and Bearing Mechanical Energy Dissipation". In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45763.
Testo completoAbstract (sommario):
Gas foil bearing (GFB) technology has reached great maturity as per engineered design and construction and its system integration into rotating machinery. Empirical research has gone beyond showing a few instances of acceptable mechanical performance, to demonstrate GFB multiple-cycle repeatable performance in spite of persistent large amplitude sub synchronous whirl motions. A GFB is a forgiving mechanical element whose engineered resilient underspring structure contains and ameliorates large rotor excursions. Analyses, however, fail to distinguish the hardening stiffness from the FB underspring structure, which under conditions of large force excitations due to imbalance, produces a complex rotordynamic behavior, rich in sub harmonic motions when operating at super critical speeds. This paper extends an earlier analysis of a rigid rotor-GFB system that dispenses with the gas film component to predict the effect of shaft rotation acceleration/deceleration on rotor amplitudes of motion and whirl frequency content. For operation above the system critical speed and as the rotor accelerates, large amplitude whirl motions appear with a main subsynchronous frequency tracking rotor speed, first at 50% speed and later bifurcating into at 33% whirl frequency. Rotor imbalance awakens and exacerbates the system nonlinear response. Slow rotor accelerations result in responses with more abundant subsynchronous whirl patterns, increased amplitudes of whirl, and accompanied by a pronounced mechanical hysteresis when the rotor decelerates. Large rotor imbalances produce both jump phenomenon and a stronger hysteresis during slow acceleration and deceleration cases. Material damping (dry friction) in the FB aids to reduce and delay the nonlinear response, eventually eliminating the multiple frequency behavior. The results bring to attention rotordynamic issues during start up and shut down events that can result from an inadequate FB technology or an unacceptable rotor imbalance grade condition.
7
Kim, Tae Ho, Jongsung Lee e Young Min Kim. "Static Structural Characterization of Multilayer Gas Foil Journal Bearings". In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-43959.
Testo completoAbstract (sommario):
The aim of this study was to evaluate the structural performance of multilayer gas foil bearings (GFBs). Three test GFBs and a dummy rotor with a diameter of 28 mm were manufactured for application to a series of structural tests. The test bearings were designed with an identical axial length of 22.5 mm, a radial clearance of 0.170 mm, and a mechanical preload of 0.050 mm at a 50% offset within the (machined) lobe bearing housings. All the bearings had multilayer (doublelayer) thin foils supported by an elastic bump strip layer, i.e., a configuration with a top foil, shim foil, and bump strip layer. Note that the shim foil is installed between the top foil and bump strip layer to enhance the dry-friction damping effect. The first bearing (Type A) had a single top foil, single shim foil, and single bump strip layer. All had an arc length of 360°. The second version (Type B) had a single top foil with an arc length of 360°, three shim foils with an arc length of 120°, and three bump strip layers with an arc length of 120°. The third version (Type C) had three top foils, three shim foils, and three bump strip layers. All had an arc length of 120°. The top foil is spot-welded to a key that is inserted into an axial key slot in the bearing housing. The shim foil and bump strip layer are inserted into an axial foil slot in the bearing housing. A series of static load-deflection tests were conducted on the test GFBs floating on the fixed, non-rotating test rotor. The measured results for the bearing deflection and structural stiffness were found to be in very good agreement with the model predictions for a GFB with a mechanical preload. In general, the test results were found to exhibit a similar radial sway space (or assembly radial clearance) and structural stiffness for all three test GFBs. Small local hysteresis loops appeared as the magnitudes of the load increased, thus determining the local structural stiffness and structural loss factor versus the displacement. The local stiffness was found to increase while the loss factor decreased as the magnitude of the displacement increased. The estimated structural loss factor can be as large as 0.9 within the radial sway space under low-load conditions.
8
Saiki, Kohei, Takeshi Watanabe e Terushige Sato. "Experimental Research on the Vibration and Noise Behavior of Helical Gearing System". In ASME 2003 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/detc2003/ptg-48028.
Testo completoAbstract (sommario):
Going with interior noise reduction in a vehicle, gear noise that is of pure frequency has been becoming a great influence on the comfortable driving. For decreasing the gear noise, it is important to predict precisely the gear noise behavior at the design stage before manufacturing. Therefore, it is necessary to clarify the physical mechanism of each resonance noise peak by actual measurement in the wide condition range of rotation speed and transmitting torque. In this research, a new 85kw oil-cooled motoring apparatus (Max speed: 6000rpm/135Nm, Max torque 400Nm/2000rpm) is developed for measuring the 3-dimensional (transverse, axial, rotational, and tilting) vibration of rotating gear blank. Also, the 3-directional (X, Y, and Z) vibration of the bearing’s holder, and the radiated gear noise are measured at the same time. As the result, the relationship between exciting vibration of rotating gear blank and the responding vibration of the bearing’s holder is carried out. The different effect upon the radiated gear noise of various vibration resonance modes is also investigated. Especially, some new interesting vibration modes, such as the drive and driven gears vibrate individually or synchronously, are found. Lastly, the mechanism of several resonance peaks which frequently causing the gear noise problems from slow city driving to fast highway operation, is conjectured concisely.
9
Dousti, Saeid, Jianming Cao, Amir Younan, Paul Allaire e Tim Dimond. "Temporal and Convective Inertia Effects in Plain Journal Bearings With Eccentricity, Velocity and Acceleration". In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45880.
Testo completoAbstract (sommario):
Fluid film bearings are commonly analyzed with the conventional Reynolds equation, without any temporal inertia effects, developed for oil or other high viscosity lubricants. In applications with rapidly time varying external loads, e.g. ships on wavy oceans, temporal inertia effect should be taken into account. As rotating speeds increase in industrial machines and the reduced Reynolds number increases above the turbulent threshold, a form of linearized turbulence model is often used to increase the effective viscosity to take the turbulence into account. Other than the turbulence effect, with high reduced Reynolds number, convective inertia effect gains importance. Water or other low viscosity fluid film bearings used in subsea machines and compressors are potential applications with a highly reduced Reynolds number.” This paper extends the theory originally developed by Tichy [1] for impulsive loads to high reduced Reynolds number lubrication in different bearing configurations. Both fluid shear and pressure gradient terms are included in the velocity profiles across the lubricant film. The incompressible continuity equation and Navier Stokes equations, including the temporal inertia term, are simplified using an averaged velocity approach to obtain an extended form of Reynolds equation which applies to both laminar and turbulent flow. All terms in the Navier Stokes equation, including both the convective and temporal inertia terms are included in the analysis. The inclusion of the temporal inertia term creates a fluid acceleration term in the extended Reynolds equation. A primary advantage of this formulation is that fluid film bearings lubricated with low viscosity lubricants which are subject to high force slew rates can be analyzed with this extended Reynolds equation. A short bearing form of the extended Reynolds equation is developed with appropriate boundary conditions. A full kinematic analysis of the short journal bearing is developed including time derivatives up to and including shaft accelerations. Linearized stiffness, damping and mass coefficients are developed for a plain short journal bearing. A time transient solution is developed for the pressure and bearing loads in plain journal bearings supporting a symmetric rigid rotor when the rotor is subjected to rapidly applied large forces. The change in the rotor displacements when subjected to unbalance forces is explored. Several comparisons between conventional Reynolds equation solutions and the extended Reynolds number form with temporal inertia effects will be presented and discussed.
10
Provenza, Andrew J., e Carlos R. Morrison. "Control of Fan Blade Vibrations Using Piezoelectrics and Bi-Directional Telemetry". In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-46714.
Testo completoAbstract (sommario):
A novel wireless device which transfers supply power through induction to rotating operational amplifiers and transmits low voltage AC signals to and from a rotating body by way of radio telemetry has been successfully demonstrated in the NASA Glenn Research Center (GRC) Dynamic Spin Test Facility. In the demonstration described herein, a rotating operational amplifier provides controllable AC power to a piezoelectric patch epoxied to the surface of a rotating Ti plate. The amplitude and phase of the sinusoidal voltage command signal, transmitted wirelessly to the amplifier, was tuned to completely suppress the 3rd bending resonant vibration of the plate. The plate’s 3rd bending resonance was excited using rotating magnetic bearing excitation while it spun at slow speed in a vacuum chamber. A second patch on the opposite side of the plate was used as a sensor. This paper discusses the characteristics of this novel device, the details of a spin test, results from a preliminary demonstration, and future plans.