To see the other types of publications on this topic, follow the link: Stiffness and damping coefficients.
Dissertations / Theses on the topic 'Stiffness and damping coefficients'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Stiffness and damping coefficients.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Mohammad, Zakariya Yahya. "The determination of a journal bearing's stiffness and damping coefficients using an extended Kalman filter." Thesis, University of Newcastle Upon Tyne, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315588.
Full text
2
Fang, Yuefa. "Calculation and measurement of the eight oil film stiffness and damping coefficients for a variable impedance hydrodynamic bearing." Thesis, Staffordshire University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359621.
Full text
3
Hoa, Pham Trong, and Nguyen Manh Hung. "Numerical calculation of dynamic stiffness and damping coefficients of oil lubrication film in internal gear motors and pumps." Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71107.
Full textAbstract:
Oil lubrication film plays an important role in analysis of dynamic behavior of the internal gear motors and pumps. During operation, the oil film is considered as the spring and damping system. Therefore, calculation of the dynamic stiffness and damping coefficients is necessary to build the mathematical model for studying of dynamic problem. In order to calculate these coefficients, the dynamic pressure and perturbing pressure distribution must be determined firstly. In this paper, the infinitesimal perturbation method (IFP) is used to calculate the dynamic pressure distribution. Based on that the dynamic stiffness and damping coefficients can be computed. The calculation results point out that the dynamic stiffness and damping coefficients are much dependent on the eccentricity ratio.
4
Breedlove, Anthony Wayne. "Experimental identification of structural force coefficients in a bump-type foil bearing." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1936.
Full text
5
Punna, Harshitha. "Impact of stiffness and damping capacity using two different rubbers on friction coefficient and noise levels of brake materials." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/theses/2773.
Full textAbstract:
Friction contact with both external and internal environments can significantly influence its efficiency, which could cause friction instabilities, vibration, and noise. Focusing on the effects that troubles brake pad, rotor, and friction-induced NVH, the main motivation for this study is to understand its drawbacks for some extent in a braking system. By proper study on applied statistics, an experimental design is planned. The design has friction tests that are performed by scaling down real test properties used in dynamometer to scaled-down properties in a subscale tester by using scaling law of physics. The test has two different types of rubbers with different humidity conditions with respect to two different brake pads in a small-scale tester, the Universal Mechanical Tester (UMT). This friction experiment helps in determining how different rubbers impact its stiffness on the coefficient of friction and noise levels, also to evaluate which scenario has the better damping capacity. The effect on the coefficient of friction and noise levels with and without rubbers is also compared. The results are subjected to the Design of Experiments analyses test know the statistical relationship between factors affecting the process and output of that process at different controllable variables namely humidity and temperature.
6
Harris, Joel Mark. "Static characteristics and rotordynamic coefficients of a four-pad tilting-pad journal bearing with ball-in-socket pivots in load-between-pad configuration." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3194.
Full text
7
Erickson, Darren Andrew. "Contact stiffness and damping estimation for constrained robotic systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq53042.pdf.
Full text
8
Kim, Sung-June 1972. "A simulation scheme for strategic distribution of damping coefficients." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/80948.
Full text
9
Hyung, Sang Su. "Nondestrutive damage detection by simultaneous identification of stiffness and damping." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2472.
Full text
10
Le, Guen Marie Joo. "Damping behaviour of plant-fibre composite materials." Thesis, University of Canterbury. Mechanical Engineering, 2014. http://hdl.handle.net/10092/9978.
Full textAbstract:
The vibration damping property of plant fibres composites is of practical interest for commercial applications of biobased and eco-composites. Damping behaviour has been observed by experimentation and exploited in the marketing of sporting equipment but the origins of this behaviour have so far been only based on conjectures. In this thesis, the damping capacity of plant fibre composites was attributed to their chemical composition and the reversible interactions enabled by the breaking and reforming of hydrogen bonds under stress. The approach to explaining the mechanisms started with the characterisation of different plant fibre types to search for correlations between their physical and chemical structure. The investigation continued with quantifying the effect of hydrogen bonding compounds such as water, glycerol and polyglycerol on the damping coefficient of fibres and reinforced composites.
The results of the polyol impregnation indicated that applying a pretreatment enhanced the vibration damping performance of
flax reinforced composites, validating the hypothesis of the essential role played by hydrogen bonds in the fibres. The improvement in the damping coefficient of the composites was shown to be to the detriment of their stiffness. The compromised between the two properties was investigated in the final part of this thesis by using hybrid flax-carbon fibre reinforced composites.
11
HYLOK, JEFFERY EDWARD. "EXPERIMENTAL IDENTIFICATION OF DISTRIBUTED DAMPING MATRICES USING THE DYNAMIC STIFFNESS MATRIX." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1029527404.
Full text
12
Issa, Jimmy. "Vibration suppression through stiffness variation and modal disparity." Diss., Connect to online resource - MSU authorized users, 2008.
Find full textAbstract:
Thesis (Ph.D.)--Michigan State University. Dept. of Mechanical Engineering, 2008.Title from PDF t.p. (viewed on July 7, 2009) Includes bibliographical references (p. 114-117). Also issued in print.
13
Wischt, Rachel Jeanne. "Variable Stiffness and Active Damping Technique for Turbomachinery using Shape Memory Alloys." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1447425764.
Full text
14
Merenda, Dario Giuseppe. "Seismic mitigation of existing masonry structures by means of added damping and stiffness." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3266/.
Full textAbstract:
In this work seismic upgrading of existing masonry structures by means of hysteretic ADAS dampers is treated.
ADAS are installed on external concrete walls, which are built parallel to the building, and then linked to the building's slab by means of steel rod connection system.
In order to assess the effectiveness of the intervention, a parametric study considering variation of damper main features has been conducted. To this aim, the concepts of equivalent linear system (ELS) or equivalent viscous damping are deepen. Simplified equivalent linear model results are then checked respect results of the yielding structures.
Two alternative displacement based methods for damper design are herein proposed. Both methods have been validated through non linear time history analyses with spectrum compatible accelerograms.
Finally ADAS arrangement for the non conventional implementation is proposed.
15
Kareaga, Laka Zorion. "Dynamic stiffness and damping prediction on rubber material parts, FEA and experimental correlation." Thesis, London Metropolitan University, 2016. http://repository.londonmet.ac.uk/1125/.
Full textAbstract:
The final objective of the present work is the accurate prediction of the dynamic stiffness behaviour of complex rubber parts using finite element simulation tools. For this purpose, it becomes necessary to perform a complex rubber compound material characterisation and modelling work; this needs two important previous steps. These steps are detailed in the present document together with a theoretical review of viscoelastic visco-elasto-plastic models for elastomers. Firstly, a new characterisation method is proposed to determine the degree of cure of rubber parts. It is known that the degree of cure of rubbers bears heavily on their mechanical properties. This method consists of the correlation of swelling results to rheometer data achieving a good agreement. Secondly, the influence of the strain rate used in static characterisation tests is studied. In this step, a new characterisation method is proposed. The latter characterisation method will be used to fit extended hyperelastic models in Finite Element Analysis (FEA) software like ANSYS. The proposed method improves the correlation of experimental data to simulation results obtained by the use of standard methods. Finally, the overlay method proposed by Austrell concerning frequency dependence of the dynamic modulus and loss angle that is known to increase more with frequency for small amplitudes than for large amplitudes is developed. The original version of the overlay method yields no difference in frequency dependence with respect to different load amplitudes. However, if the element in the viscoelastic layer of the finite element model are given different stiffness and loss properties depending on the loading amplitude level, frequency dependence is shown to be more accurate compared to experiments. The commercial finite element program Ansys is used to model an industrial metal rubber part using two layers of elements. One layer is a hyper viscoelastic layer and the other layer uses an elasto-plastic model with a multi-linear kinematic hardening rule. The model, being intended for stationary cyclic loading, shows good agreement with measurements on the harmonically loaded industrial rubber part.
16
Liu, Yanqing. "Variable damping and stiffness semi-active vibration isolation control using magnetorheological fluid dampers." 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/144553.
Full text
17
Kayabasi, Iskender. "Numerical Investigation Of Characteristics Of Pitch And Roll Damping Coefficients For Missile Models." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614917/index.pdf.
Full textAbstract:
In this thesis the characteristics of pitch and roll damping coefficients of missile models are investigated by using Computational Fluid Dynamics (CFD) techniques. Experimental data of NACA0012 airfoil, Basic Finner (BF) and Modified Basic Finner (MBF) models are used for validation and verification studies. Numerical computations are performed from subsonic to supersonic flow regimes. Grid refinement and turbulence model selection studies are conducted before starting the dynamic motion simulations. Numerical method of dynamic motion simulation is validated with a 2D NACA0012 airfoil. After the validation of numerical method, forced-oscillation motion is given to the BF and MBF models. In order to get deeper understandings about the characteristics of dynamic pitching and rolling motions, parametric studies are performed. The amplitude and frequency of forced-oscillation motions are investigated one by one. The effects of angle of attacks are also investigated for both pitching and rolling motions. The results of CFD simulations are compared with experimental data obtained from different wind tunnel and free flight tests. It is seen from these comparisons that experimental and numerical results are in good agreement throughout the whole flow regime. In conclusion, the numerical method presented in this study is validated and can be used for the prediction of pitch and roll damping coefficient of any missile configurations.
18
Baker, Jose Enrique. "Measurements of leakage, power loss and rotordynamic force coefficients in a hybrid brush seal." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2767.
Full text
19
El-Tayeb, Nabil Said Mohamed. "The dynamic properties of ball bearings." Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366386.
Full text
20
Rees, Emily V. L. "Methane gas hydrate morphology and its effect on the stiffness and damping of some sediments." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/79442/.
Full textAbstract:
Gas hydrates are ice–like compounds found in deep sea sediments and permafrosts. Concise detection and quantification of natural methane gas hydrate deposits, will allow for a more robust assessment of gas hydrate as a potential energy resource or natural geohazard. Current seismic methods, used to identify and quantify gas hydrates, have proved to be unreliable in providing accurate information on the extent of natural gas hydrate deposits, due to the lack of understanding on how gas hydrate affects the host sediment. Direct measurement of some hydrate bearing sediment properties has been made possible in recent years through advances in pressure coring techniques, but methods for dynamically testing these samples at in–situ pressures are still unavailable. Laboratory tests on synthetic hydrate bearing sediments have shown that factors such as formation technique, sediment type and use of hydrate former affects the form and structure of hydrate in the pore space and how it interacts with the sediment. The aim of this research was therefore to create methane hydrate in sediments under a variety of conditions, so that the influence of hydrate morphology could be investigated. A number of experiments were conducted using two distinct formation techniques. The first technique formed methane hydrate from the free gas phase in almost fully water saturated conditions. Five sand specimens, with a range of hydrate contents from 10% to 40% were formed and tested in the gas hydrate resonant column (GHRC). Results from these tests were compared with previous results from tests where methane hydrate had been formed from free gas in partially saturated conditions. It was found that formation method had a significant influence on the properties of the hydrate bearing sand, and therefore the morphology of the hydrate in the pore space. The second set of experiments formed methane hydrate from free gas within partially saturated sediments, but where the sediments were made up of coarse granular materials with a variety of particle size and shape. As it had been established that hydrate acts as a cement when formed under partially saturated conditions, the experiments aimed to observe the effect of particle size and shape on hydrate bonding mechanisms. The results showed that the influence of disseminated hydrate on the physical properties of the specimens was affected by both mean particle size and by particle shape, with the surface area of the sediment grains influencing the volume and distribution of hydrate throughout a material and therefore it’s bonding capabilities. In addition to the experiments on synthetic hydrate specimens, five core sections containing naturally occurring gas hydrate in fine grained sedimentsweremade available to the University of Southampton from the Indian National Gas Hydrate Program (NGHP) 01 expedition. High resolution CT imaging of the core sections observed large volumes of methane hydrate as a network of veins throughout the specimens. Due to sample disturbance caused during the depressurisation and subsequent freezing of the samples prior to delivery, dynamic testing in the gas hydrate resonant column apparatus was not feasible. Therefore, the hydrate was dissociated and a number of geotechnical tests were undertaken on the remaining host sediment. Results from these tests suggested that hydrate dissociation could affect host sediment properties, due to a change in water content, salinity and structure.
21
Pan, Fan. "Gilbert damping of doped permalloy from first principles calculations." Licentiate thesis, KTH, Materialfysik, MF, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-170344.
Full textAbstract:
The dynamic process of how fast a spintronic device can be switched from one state to another is characterized by the Gilbert damping parameter. It has been found that the Gilbert damping along with other intrinsic properties in permalloy, can be tuned by different dopants and doping concentration. Therefore, a study of intrinsic magnetic properties with emphasis on the dependence of the Gilbert damping parameter from first principles calculations is investigated. It is aimed at to give an insight of the microscopic understanding originated from electronic structure and to provide a guideline in the practical spintronic design. The topic of the present thesis is to investigate, by means of first principle calculations, how the variation of the Gilbert damping parameter depends upon the electronic structure of pure and doped permalloy. We show that the Gilbert damping has a monotonic increase with the doping concentration due to an increasing amount of scattering processes. The dopants of the 5d transition metal give rise to a much larger impact than the 4d, as the spin orbit coupling effect is more pronounced in the heavy elements. Our results are in satistying agreement with experiment.QC 20150629
22
Kadam, Ruthvik Dinesh. "Design and Additive Manufacturing of Carbon-Fiber Reinforced Polymer Microlattice with High Stiffness and High Damping." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/103009.
Full textAbstract:
Carbon fiber reinforced polymer (CFRP) composites are known for their high stiffness-to-weight and high strength-to-weight ratios and hence are of great interest in several engineering fields such as aerospace, automotive and defense. However, despite their light weight, high stiffness and high strength, their application in these fields is limited due to their poor energy dissipation and vibration damping capabilities. This thesis presents a two-phase microlattice design to overcome this problem. To realize this design, a novel tape casting integrated multi-material stereolithography system is developed and mechanical properties of samples fabricated using this system are evaluated. The design incorporating a stiff phase (CFRP) and a high loss phase, exhibiting high stiffness as well as high damping, is studied via analytical and experimental approaches. To investigate its damping performance, mechanical properties at small-strain and large-strain regimes are measured through dynamic material analysis (DMA) and quasi-static cyclic compression tests respectively. It is seen that both intrinsic (small-strain) and structural (large-strain) damping in terms of a figure of merit (FOM), E1/3tanδ/ρ, can be enhanced by a small addition of a high loss phase in Reuss configuration. Moreover, it is seen that structural damping is improved at low relative densities due to the presence of elastic buckling during deformation. For design usefulness, tunability maps, displaying FOM in terms of design parameters, are developed by curve fitting of experimental measurements. The microlattice design is also evaluated quantitatively by comparing it with existing families of materials in a stiffness-loss map, which shows that the design is as stiff as commercial CFRP composites and as dissipative as elastomers.Master of Science
23
Bowland, Adam Gregory. "Comparison and Analysis of the Strength, Stiffness, and Damping Characteristics of Concrete with Rubber, Latex, and Carbonate Additives." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/28229.
Full textAbstract:
This dissertation presents the results of a study performed to investigate methods for increasing the damping capacity of concrete. A variety of additives, both particle and latex based, were added to standard concrete mixtures by replacing up to 20% of the fine aggregate to measure their effects on strength, stiffness, damping, and air content. The additives included rubber particles from recycled tires, calcium carbonate particles, styrene butadiene rubber (SBR) latex, and a commercially available product named ConcreDamp which contains vegetable gum suspended in styrene butadiene latex.
An initial investigation resulted in the observation that all of the additives with the exception of the SBR latex would both increase air content and decrease compressive strength. As a result, combinations of additives were investigated to see if both the mechanical and dynamic properties could be improved. The addition of steel fibers to mixtures with ground rubber were found to significantly increase air content which offset any gains in compressive strength. The combination of ground rubber and latex was shown to improve both increase compressive strength and reduce air content.
The study advanced to investigate the effects of rubber size on air content, strength, and damping. It was found that for the same volume of rubber, a larger rubber particle would decrease air content, decrease compressive strength, and improve damping.
The results of this study show that the best performing additive was the vegetable gum latex which improved the concrete damping by a factor of 2 when added as 15% of the fine aggregate. Additionally, an equation is presented for calculating a strength reduction factor for concrete containing rubber particles of different sizes.
Finally, two full scale footbridge laboratory specimens were tested to investigate the effect of increased material damping at the structural level. One footbridge was constructed using a base concrete mixture without damping admixtures. The second was constructed with a concrete mixture that contained a replacement of 15% of the fine aggregate with ground rubber. The results were used to create a finite element model in SAP2000 that was used to predict the effects that high damping concretes would have on the footbridge specimen.Ph. D.
24
OZGEN, GOKHAN O. "THEORETICAL AND EXPERIMENTAL STUDY ON THE DIRECT DAMPING MATRIX IDENTIFICATION BASED ON THE DYNAMIC STIFFNESS MATRIX AND ITS APPLICATIONS TO DYNAMIC SYSTEMS MODELING." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1163790951.
Full text
25
Balupari, Raja Shekar. "VALIDATION OF FINITE ELEMENT PROGRAM FOR JOURNAL BEARINGS -- STATIC AND DYNAMIC PROPERTIES." UKnowledge, 2004. http://uknowledge.uky.edu/gradschool_theses/325.
Full textAbstract:
The analysis of bearing systems involves the prediction of their static and dynamic characteristics. The capability to compute the dynamic characteristics for hydrodynamic bearings has been added to Bearing Design System (BRGDS), a finite element program developed by Dr. R.W. Stephenson, and the results obtained were validated. In this software, a standard finite element implementation of the Reynolds equation is used to model the land region of the bearing with pressure degrees of freedom. The assumptions of incompressible flow, constant viscosity, and no fluid inertia terms are made. The pressure solution is integrated to give the bearing load, and the stiffness and damping characteristics were calculated by a perturbation method. The static and dynamic characteristics of 60, 120 and 180 partial bearings were verified and compared for a length to diameter (L/D) ratio of 0.5. A comparison has also been obtained for the 120 bearing with L/D ratios of 0.5, 0.75 and 1.0. A 360-journal bearing was verified for an L/D ratio of 0.5 and also compared to an L/D ratio of 1.0. The results are in good agreement with other verified results. The effect of providing lubricant to the recesses has been shown for a 120 hybrid hydrostatic bearing with a single and double recess.
26
Wolff, Andrew. "Mechanical Properties of Maturing Dystrophic Skeletal Muscle." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/37922.
Full textAbstract:
The main goal for my research was to challenge the long held belief that the mechanical properties of maturing dystrophic compared to control skeletal muscle membranes are weaker, leading to onset of Duchenne muscular dystrophy (DMD). We built on a previous report from our lab that suggested sarcolemmal membranes from dystrophic mice are not more susceptible to damage early in maturation (i.e., age 9-12 days) and determined if and when muscle mechanical properties change as the mice mature. Across four studies, I have helped define the role of dystrophin-deficient skeletal muscle membranes in the onset of DMD.
A linear viscoelastic muscle model was used to determine passive stiffness and damping in control and dystrophic muscles from maturing mice aged 14-35 days. Results confirmed my hypothesis that there are no differences in passive mechanical properties between normal and dystrophic mice.
Recognizing the limitations of the linear model, a nonlinear model was developed to determine the stiffness and damping of active and passive dystrophic muscles from maturing mice aged 21 and 35 days. The nonlinear model achieved a significantly better fit to experimental data than the linear model when muscles were stretched to 15% strain beyond resting length. Active and passive mechanical properties of dystrophic mice were not different than control at 14 and 28 days of age.
The previously developed nonlinear model was used to determine a more complete time-course (14-100 days of age) of dystrophic muscle mechanical properties. There was no difference in passive stiffness between mdx and control muscles at each age. However, the mdx:utrn-/- muscles showed increased stiffness compared to control and mdx muscles at 21 and 28 days, suggesting a temporary change within the muscle that only occurs with a lack of both utrophin and dystrophin.
Fast-twitch and slow-twitch muscle mechanical properties were compared in control and dystrophic mice aged 3, 5, and 9 weeks of age. Dystrophic and control slow-twitch muscles did not have different mechanical properties, suggesting that a lack of dystrophin does not affect slow-twitch muscles during maturation (3-5 weeks) or well after maturation (9 weeks).Ph. D.
27
Böswald, Marc. "Updating of local non linear stiffness- and damping parameters in large finite element models by using vibration test data /." Köln : DLR, Deutsches Zentrum für Luft- und Raumfahrt, 2005. http://www.gbv.de/dms/bs/toc/518690482.pdf.
Full text
28
Sprowl, Tony Brandon. "A study of the effects of inlet preswirl on the dynamic coefficients of a straight-bore honeycomb gas damper seal." Texas A&M University, 2003. http://hdl.handle.net/1969.1/1617.
Full textAbstract:
In high-pressure centrifugal compressors, honeycomb seals are often used as replacements for labyrinth seals to enhance dynamic stability. A concern exists with the loss of this enhanced stability if the honeycomb cavities become clogged with debris over time. So, as a first objective, static and dynamic tests were conducted on a constant-clearance honeycomb and a constant-clearance smooth-bore seal under three inlet preswirl conditions to determine the effects of inlet preswirl. The resulting leakage flowrate and dynamic parameters, effective stiffness and damping of the seal, were measured for each seal and then compared, with the smooth-bore seal representing the honeycomb seal with completely clogged cells. The second objective was to evaluate a two-control volume theory by Kleynhans and Childs with the measured data under the influence of preswirl.
Both seals have a 114.7mm bore with a radial clearance of 0.2mm from the test rotor. The honeycomb seal has a cell width of 0.79mm and cell depth of 3.2mm. The target test matrix for each preswirl setting consisted of three exit-to-inlet pressure ratios of 15%, 35%, and 50%, and three rotor speeds out to 20,200 rpm. The target inlet air pressure was 70 bar-a.
Experimental results show that, for a clean honeycomb seal, preswirl has little effect on effective stiffness, Keff*, and decreases effective damping, Ceff*, by about 20% at the high inlet preswirl ratio (~0.6). However, comparing smooth and honeycomb seal results at higher inlet preswirl shows a potential reduction in Keff* by up to 68%, and a large drop and shift in positive Ceff* values, which could cause an instability in the lower frequency range. Measured leakage shows a potential increase of about 80%, regardless of test conditions. A swirl brake at the seal entrance would fix this loss in stability by significantly reducing inlet preswirl.
The two-control-volume theory model by Kleynhans and Childs seems to follow the frequency-dependent experimental data well for the honeycomb seal. Theory predicts conservatively (under-predicts) for stability parameters such as k* and Ceff* and for leakage. Predictions for K and Keff may possibly be improved with better measured friction factor coefficients for each seal.
29
Clements, Joshua Ryan. "The Experimental Testing of an Active Magnetic Bearing/Rotor System Undergoing Base Excitation." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/35827.
Full textAbstract:
Active Magnetic Bearings (AMB) are a relatively recent innovation in bearing technology. Unlike conventional bearings, which rely on mechanical forces originating from fluid films or physical contact to support bearing loads, AMB systems utilize magnetic fields to levitate and support a shaft in an air-gap within the bearing stator. This design has many benefits over conventional bearings. The potential capabilities that AMB systems offer are allowing this new technology to be considered for use in state-of-the-art applications. For example, AMB systems are being considered for use in jet engines, submarine propulsion systems, energy storage flywheels, hybrid electric vehicles and a multitude of high performance space applications. Many of the benefits that AMB systems have over conventional bearings makes them ideal for use in these types of vehicular applications. However, these applications present a greater challenge to the AMB system designer because the AMB-rotor system may be subjected to external vibrations originating from the vehicle's motion and operation. Therefore these AMB systems must be designed to handle the aggregate vibration of both the internal rotor dynamic vibrations and the external vibrations that these applications will produce.
This paper will focus on the effects of direct base excitation to an AMB/rotor system because base excitation is highly possible to occur in vehicular applications. This type of excitation has been known to de-stabilize AMB/rotor systems therefore this aspect of AMB system operation needs to be examined. The goal of this research was to design, build and test a test rig that has the ability to excite an AMB system with large amplitude base excitation. Results obtained from this test rig will be compared to predictions obtained from linear models commonly used for AMB analysis and determine the limits of these models.Master of Science
30
Haberman, Michael Richard. "Design of High Loss Viscoelastic Composites through Micromechanical Modeling and Decision Based Materials Design." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14599.
Full textAbstract:
This thesis focuses on the micromechanical modeling of particulate viscoelastic composite materials in the quasi-static frequency domain to approximate macroscopic damping behavior and has two main objectives. The first objective is the development of a robust frequency dependent multiscale model. For this purpose, the self-consistent (SC) mean-field micromechanical model introduced by Cherkaoui et al [J. Eng. Mater. Technol. 116, 274-278 (1994)] is extended to include frequency dependence via the viscoelastic correspondence principal. The quasi-static model is then generalized using dilute strain concentration tensor formulation and validated by comparison with complex bounds from literature, acoustic and static experimental data, and established models. The second objective is SC model implementation as a tool for the design of high loss materials. This objective is met by integrating the SC model into a Compromise Decision Support Protocol (CDSP) to explore the microstructural design space of an automobile windshield. The integrated SC-CDSP design space exploration results definitively indicate that one microstructural variable dominates structure level acoustic isolation and rigidity: negative stiffness. The work concludes with a detailed description of the fundamental mechanisms leading to negative stiffness behavior and proposes two negative stiffness inclusion designs.
31
Oliveira, Fernando dos Santos. "Otimização topológica de dissipadores metálicos aplicados ao controle de vibrações em estruturas." reponame:Repositório Institucional da UnB, 2016. http://repositorio.unb.br/handle/10482/21963.
Full textAbstract:
Tese (doutorado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2016.Submitted by Fernanda Percia França (fernandafranca@bce.unb.br) on 2016-09-30T18:04:30Z No. of bitstreams: 1 2016_FernandodosSantosOliveira.pdf: 6646040 bytes, checksum: a918278b21da46660beef0d43415e2b7 (MD5)
Approved for entry into archive by Raquel Viana(raquelviana@bce.unb.br) on 2016-12-19T12:36:52Z (GMT) No. of bitstreams: 1 2016_FernandodosSantosOliveira.pdf: 6646040 bytes, checksum: a918278b21da46660beef0d43415e2b7 (MD5)
Made available in DSpace on 2016-12-19T12:36:52Z (GMT). No. of bitstreams: 1 2016_FernandodosSantosOliveira.pdf: 6646040 bytes, checksum: a918278b21da46660beef0d43415e2b7 (MD5)
A construção de edificações cada vez mais altas e esbeltas tem se tornado bastante comum nos grandes centros, desafiando assim os projetistas estruturais a elaborarem projetos cada vez mais eficientes de forma que o arranjo adotado possa utilizar da melhor forma as características dos materiais. O uso de dispositivos que adicionam rigidez e amortecimento às estruturas sujeitas a ações dinâmicas, como cargas de vento e terremotos, tem se tornado cada vez mais comum nas estruturas civis. Um desses dispositivos mecânicos que tem sido amplamente utilizado é o dissipador do tipo Added Damping and Stiffness (ADAS), que se corretamente instalado, pode aumentar significativamente a resistência, rigidez e capacidade de dissipação de energia das estruturas das edificações. Os dispositivos do tipo ADAS são basicamente dissipadores de energia instalados na estrutura com o objetivo de que a dissipação ocorra de forma concentrada nesses elementos, protegendo assim a estrutura principal de maiores danos. Uma vez ocorrida a ação dinâmica que danifique esses elementos, eles podem ser facilmente substituídos sem maiores dificuldades. Esses dissipadores de energia apresentam a vantagem de não precisarem de tecnologia avançada para sua produção e podem ser facilmente instalados na estrutura. Possuem ainda a vantagem de que fatores ambientais tais como temperatura e umidade, pouco ou nada afetam seu desempenho. No presente estudo, como uma alternativa ao ADAS, é realizada a otimização topológica de um dissipador metálico aplicado à redução de vibração em edificações sujeitas a terremotos, considerando através de análise numérica e experimental o formato adequado desse tipo de dispositivo. Em seguida busca-se a obtenção da probabilidade de falha desse sistema estrutural, levando-se em consideração as incertezas inerentes ao projeto, através da análise de confiabilidade. ________________________________________________________________________________________________ ABSTRACT
The construction of increasingly tall and slender buildings has become quite common in large cities, challenging the structural engineers to develop increasingly efficient designs so that the adopted arrangement can make best use of the characteristics of materials. The use of devices that add stiffness and damping to structures subjected to dynamic actions such as wind and earthquake loads, has become increasingly common in civil structures. One of the mechanical devices that have been widely used is the Added Damping and Stiffness (ADAS), which if correctly installed, can significantly increase the strength, stiffness and energy dissipation capacity of the structures. ADAS devices are basically energy dissipators installed in the structure in order that dissipation occurs in these elements in a concentrated way, thereby protecting the main structure from further damage. Once the dynamic action that damages these elements occurs, they can be easily replaced without major costs. These energy dissipators have the further advantage of not require advanced technology for its production and can be easily installed in the structure. They also have the advantage that environmental factors such as temperature and humidity, has little or no effect in their performance. In the present study, as an alternative to ADAS, is performed the topology optimization of a metallic dissipator applied to the reduction of vibration in buildings subject to earthquakes, raising through numerical and experimental analysis the appropriate device type format. Then is searched the probability of failure of this structural system, taking into consideration the uncertainty inherent in the design, through reliability analysis.
32
Alhujaili, Fahad Abdulrahman. "Semi-Active Control of Air-Suspended Tuned Mass Dampers." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1354480214.
Full text
33
KUROIWA, TATIANA. "Application of modal decomposition and random decrement technique to ambient vibration measurement for detection of stiffness and damping change of a full-scale frame structure." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/124509.
Full text
34
Gunduz, Aydin. "Multi-Dimensional Stiffness Characteristics of Double Row Angular Contact Ball Bearings and Their Role in Influencing Vibration Modes." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1326397623.
Full text
35
Hareer, Rahila Wardak. "Seismic response of building façade system with energy absorbing connections." Queensland University of Technology, 2007. http://eprints.qut.edu.au/16537/.
Full textAbstract:
Facades are popular in modern buildings and are made of different materials such as pre-cast concrete, glass, aluminium, granite or marble and steel. During recent times seismic activity in densely populated areas has resulted in damage and a consequent loss of life. There were many types of building failure, including failure of building facade systems. Facade systems are highly vulnerable and fail more frequently than the buildings themselves with significant devastating effects. During an earthquake building frames suffer large interstorey drifts, causing racking of the building facade systems. The facade systems may not be able to cater for such large deformations and this can result in either functional or total failure at the facade connections or damage by pounding (impact) with adjacent facade panels. Façade failure and collapse can cause serious damage to buildings and injury to people in the vicinity. Moreover, facade represent between 10- 20 % or more of the total building cost depending on the size and importance of the facility and facade material (Facades1980). Considering the cost and safety issues, the importance of a well designed facade system on a building needs to be emphasised. In modern buildings, energy absorbing passive damping devices are very commonly used for energy absorption in order to manage the vibration response of multistorey buildings in an earthquake event. A number of manufactured dampers such as Viscoelastic and viscous, friction and yielding dampers are available. These dampers use a range of materials and designs in order to achieve diverse levels of damping and stiffness. This thesis is an investigation of the seismic behaviour of building facade systems and studies the effects of facade and connection properties on this response. The objectives with energy absorbing connections of the study are to determine and control facade distortions and to establish the required connection properties. Finite Element techniques have been used for modelling and analysis of the building frame, facade and connections. Time history analyses under earthquake loadings were carried out to determine the system response in terms of inter-storey drifts, facade distortions, differential displacement between facades and frames and the axial force in horizontal connections. Connection properties with respect to stiffness and energy absorption capability (or damping) have been modelled and varied to obtain the desired response. Findings illustrate the influence of these connection properties on system response and show that it is possible to control facade distortions to within acceptable limits. They also demonstrate that energy absorbing connections are able to reduce inter-storey drifts and mitigate the detrimental seismic effects on the entire building facade system.
36
Icke, Kyle J. "Determination of the Compressive Response of the Pediatric Thorax Utilizing System Identification Techniques." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1417608406.
Full text
37
Rafique, Sajid. "Piezoelectric vibration energy harvesting and its application to vibration control." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/piezoelectric-vibration-energy-harvesting-and-its-application-to-vibration-control(d9edcedf-054e-4921-9ba3-5e015b9bbd8f).html.
Full textAbstract:
Vibration-based energy harvesting using piezoelectric materials have been investigated by several research groups with the aim of harvesting maximum energy and providing power to low-powered wireless electronic systems for their entire operational life. The electromechanical coupling effect introduced by the piezoelectric vibration energy harvesting (PVEH) mechanism presents modelling challenges. For this reason, there has been a continuous effort to develop different modelling techniques to describe the PVEH mechanism and its effects on the dynamics of the system. The overall aims of this thesis are twofold: (1) a thorough theoretical and experimental analysis of a PVEH beam or assembly of beams; (2) an in-depth analytical and experimental investigation of the novel concept of a dual function piezoelectric vibration energy harvester beam/tuned vibration absorber (PVEH/TVA) or 'electromechanical TVA' and its potential application to vibration control. The salient novel contributions of this thesis can be summarised as follows: (i) An in-depth experimental validation of a PVEH beam model based on the analytical modal analysis method (AMAM), with the investigations conducted over a wider frequency range than previously tested. (ii) The precise identification of the electrical loads that harvest maximum power and that induce maximum electrical damping. (iii) A thorough investigation of the influence of mechanical damping on PVEH beams. (iv) A procedure for the exact modelling of PVEH beams, and assemblies of such beams, using the dynamic stiffness matrix (DSM) method. (v) A procedure to enhance the power output from a PVEH beam through the application of a tip rotational restraint and the use of segmented electrodes. (vi) The theoretical basis for the novel concept of a dual function PVEH beam/TVA, and its realisation and experimental validation for a prototype device. A thorough experimental validation of a cantilever piezoelectric bimorph energy harvester without a tip mass is presented under random excitation. The study provided a deep insight into the effect of PVEH on the dynamics of the system for variations in electrical load. An alternative modelling technique to AMAM, based on the DSM, is introduced for PVEH beams. Unlike AMAM, the DSM is exact, since it is based on the exact solution to the bending wave equation. It also readily lends itself to the modelling of beams with different boundary conditions or assemblies of beams of different crosssections. AMAM is shown to converge to DSM if a sufficiency of modes is used. Finally, an in-depth theoretical and experimental investigation of a prototype PVEHbeam/TVA device is presented. This device comprises a pair of bimorphs shunted by R-L-C circuitry and can be used as a tuned mass damper (TMD) to attenuate a vibration mode of a generic structure. The optimal damping required by this TMD is generated by the PVEH effect of the bimorphs. Such a device combines the advantages of conventional mechanical and electrical TVAs, overcoming their relative disadvantages. The results demonstrate that the ideal degree of attenuation can be achieved by the proposed device through appropriate tuning of the circuitry, thereby presenting the prospect of a novel class of 'electromechanical' tuned vibration absorbers.
38
Ullberg, Mårten. "Development of a Parallel Finite-element Tool for Dynamic Soil-structure Interaction : A Preliminary Case Study on the Dynamic Stiffness of a Vertical Pile." Thesis, KTH, Bro- och stålbyggnad, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-99381.
Full textAbstract:
This thesis has two major goals; first to develop scalable scripts for steady-state analysis, then to perform a case study on the dynamic properties of a vertical pile. The scripts are based on the numerical library PETSc for parallel linear algebra. This opens up the opportunity to use the scripts to solve large-scale models on supercomputers. The performance of the scripts are verified against problems with analytical solutions and the commercial software ABAQUS. The case study compares the numerical results with those obtained from an approximate solution. The results from this thesis are verified scripts that can find a steady-state solution for linear-elastic isotropic solids on supercomputers. The case study has shown differences between numerical and semi-analytical solutions for a vertical pile. The dynamic stiffness show differences within reasonable limits but the equivalent viscous damping show larger differences. This is believed to come from the material damping in the soil that has been excluded from the approximate solution. These two results make it possible for further case studies on typical three-dimensional problems, that result in large-scale models, such as the dynamic properties of a slanted pile or pile-groups. The scripts can easily be expanded and used for other interesting research projects and this is the major outcome of from this thesis.
39
Kolouch, Martin. "Vývoj a přezkoušení nové metody pro měření tuhostních a tlumicích vlastností kloubů v paralelně kinematických strukturách." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-233839.
Full textAbstract:
In this dissertation is presented the development of a new measurement method for the stiffness and damping characteristics of a joint in a parallel kinematic machine tool. The main contribution of this method is specially for applications, that demand accurate information about stiffness and damping parameters from assembled parts of machines tool. Methods for compensation of deformations in machines tool, that are carried out by control, belong to these applications. Another contribution of this work is the technical implementation of the proposed principle of the new method. At this point the focus of the work was devoted to signal processing, that differs in a certain degree from other types of signal processing methods, that are used in other dynamic measurements, e.g. modal analysis. One of the main requirements was the possibility to consider the nonlinear behavior of the measured structure. In another chapter the modified signal processing method was used for measuring a joint in a test rig. The results were compared with results from other measurement methods. On account of this comparison the statement was made that the new method can be used for measuring the stiffness and damping parameters of machine parts. Finally the new method was applied to measure the properties of a joint, which was built in a machine tool. Moreover, the problems, that appeared during the measurement, were also described.
40
Noll, Scott A. "Dynamic Interactions Between Multidimensional Viscoelastic Joints and an Elastic Frame Structure." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1364809438.
Full text
41
Runnels, Immanuel Kaleoonalani. "Dynamic Full-Scale Testing of a Pile Cap with Loose Silty Sand Backfill." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1854.pdf.
Full text
42
C, Gopalakrishnan Srikumar. "Tribodynamics of Right Angled Geared System." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1540566189193567.
Full text
43
Broderick, Rick Davon. "Statnamic Lateral Loading Testing of Full-Scale 15 and 9 Group Piles in Clay." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/861.
Full textAbstract:
Studies of seismic and impact loading on foundation piles is an important and a focused interest in the engineering world today. Because of seismic and other natural events are unpredictable, uncontrollable and potentially unsafe it is a vital study to understand the behavior and relationship structures in motion have on there foundation. Statnamic Loading has become a popular method of studying this relationship in a controlled environment. Two groups of 9 and 15 driven hollow pipe piles were tested in saturated clay at the Salt Lake City Airport in July of 2002. The 9-pile group (3x3 configuration) was separated at 5.65 pile diameters and the 15-pile group (3x5 configuration) was separated at 3.92 pile diameters. The testing consisted of five target deflections. Each target deflection consisted of 15 cyclic lateral static loadings and a 16th lateral statnamic load. This study focuses on the statnamic loading. Damping ratios ranged from 23 to 50 percent for the 15-pile group and 29 to 49 percent for the 9-pile group. Both pile groups increased in damping as the deflections increased. The optimized mass in motion for the entire system was found to be roughly 21,000kg for the 15-pile group and 14,000 kg for the 9-pile group. Stiffness for the 15-pile group started at 50kN/mm and ended at 21kN/mm. The 9-pile group ranged from 28kN/mm to 12kN/mm.
44
Liu, Te-Wei, and 劉得偉. "An Inverse Vibration Problem of Estimating Coefficients of Stiffness and Damping for the Multiple Degrees of Freedom System with Non-linear External Forces." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/13939892173889638651.
Full textAbstract:
碩士國立高雄應用科技大學
模具工程系
99
In this study the Beck’s nonlinear estimation procedure coupled with Runge-Kutta method is applied to solve the reverse of multiple degrees of freedom with nonlinear external force vibration problems. The sensitivity coefficients of Beck’s nonlinear estimation procedure are modified by the fourth-order Runge-Kutta numerical method, improves the accuracy of the program to accelerate the iteration convergence rate, and so reverse forecast multiple unknown stiffness and damping coefficients. Baker's estimate of the original program is a non-linear first-order Taylor series of precision, and this research is an amendment to Baker's non-linear estimation procedures to enhance the accuracy of four-order Taylor series. Beck's nonlinear estimation procedure is applied with Runge-Kutta numerical method, reverse to solve sets of unknown spring and damping factor, is a major innovative features of this study. The convergence rate is better than the original Baker's non-linear estimation procedures, is a major focus of development in this study. The results showed that the inverse algorithm for solving the cases of three non-linear force able to effectively improve the original Beck's nonlinear estimation procedure, the best convergence rate can be increased to 33.3%. From the numerical computation of the elasticity and damping, compare with the exact solutions under the measurement errors on the assumption that 1%, 5% and 10% of the conditions, the real percentage of error are less than 0.9%, 4.5% and 9.2%, and the measurement error is proportional to the percentage of the real error.
45
Mehta, Naitik. "Comparison of a Slanted-Tooth See-Through Labyrinth Seal to a Straight-Tooth See-Through Labyrinth Seal for Rotordynamic Coefficients and Leakage." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-10825.
Full textAbstract:
This research compares the leakage and rotordynamic characteristics of a slanted-tooth labyrinth seal to a conventional straight-tooth labyrinth. Detailed results comparing the rotordynamic coefficients and leakage parameters of a slanted-tooth see-through labyrinth seal and a straight-tooth see-through labyrinth seal are presented. The straight-tooth labyrinth seal used in this research was originally tested by Arthur Picardo. The slanted-tooth labyrinth seal was designed and fabricated to be identical to the straight-tooth labyrinth seal in terms of pitch, depth, and the number of teeth. The angle of inclination of the teeth in the slanted-tooth labyrinth seal was chosen to be 65° from the normal axis. The seals were tested at an inlet pressure of 70 bar-a (1015 psi-a), pressure ratios of 0.4, 0.5, and 0.6, rotor speeds of 10,200, 15,350, and 20,200 rpm, and a radial clearance of 0.2 mm (8 mils). The experiments were carried out at zero, medium, and high inlet preswirl ratios.
The experimental results show only minute differences in the rotordynamic coefficients between the two seals. But, the slanted-tooth labyrinth seal leaked approximately 10% less than the straight-tooth labyrinth seal. A study of prediction versus experimental data was done. XLlaby was used for prediction. XLlaby was developed for a straight-tooth labyrinth seal design and did not do a good job in predicting the rotordynamic coefficients and the leakage rate.
46
Chih-chia, Chen, and 陳治嘉. "Interaction of Damping Eccentricity and Stiffness Eccentricity." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/72853418424083774623.
Full text
47
hu, Hsing-yi, and 胡興億. "Identification of Stiffness and Damping of Bolted Joints." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/09330910514651325923.
Full textAbstract:
碩士國立中興大學
機械工程學系
88
The correct modeling of the stiffness and the damping of bolted joints affects the accuracy of finite element analysis. As a result, a lot of researches have been done. Traditionally spring elements and dampers are inserted into the interface of the bolted surfaces to respresent the stiffness and the damping of the joint. The correct values of the stiffness and the damping are obtained by tuning the values to match experimental result. This paper tried to use interface element to replace the spring elements to model the stiffness of the joint. The young’s moduli of the interface elements are adjusted to correlate the analysis and expenimental results. The optimization theory is used to minimize the differences of experimental and analytical frequencies. The constraints are imposed to maintain the orthogonality condition of mode shapes. Anisotropic material is assumed for the interface elements. The tightening torque of the joint is varied to observe the effects on stiffness and damping of the joint.
48
Lee, Guan-Hsing, and 李冠興. "Earthquake Proof Efficiency of Longitudinal Added Damping and Stiffness." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/42245106142437106884.
Full textAbstract:
碩士逢甲大學
土木及水利工程所
92
The purpose of the traditional earthquake resistance design is able to only keep the strength and stiffness of the structure. Not only the effect of ductility design is limited and incapable of conforming the requirement of the ”functionality”, but the cost is increasing substantially following the traditional earthquake resistance design because of the degree of the standard is higher after revising the code. However, the structural passive control technology has been developed rapidly over the past ten years, and recognized as a feasible and promising way in mitigating the seismic response of a structure from theoretical studies, experimental results and experiences under actual earthquakes. In numerous passive control devices, the added damping and stiffness(ADAS) has been verified as an effective and economical energy-absorbing device to dissipate the seismic energy remarkably. It has the advantage of low manufacture costs and being easy to install. Successful applications have been achieved in Taiwan actually. The longitudinal added damping and stiffness (LADAS), a new type device, has been developed in this study. Under cyclic loading tests, the proposed LADAS device can sustain an extremely large number of yielding reversals without any sign of stiffness or strength degradation and has stable energy-dissipating capability. By modifying the Wen’s model, an advanced analytical model in an incremental form for the LADAS is also proposed to predict the nonlinear hysteresis behavior. After comparing the analytical and experimental results, it is illustrated that the proposed Wen’s model in an incremental form could successfully predict the hysteretic behavior of the LADAS device. Moreover, the quake-proof efficiency of the LADAS was carried out on a scaled-down three-story steel frame on an electronic shaking table in Feng Chia University. The experiment results demonstrate that a structure with LADASs can significantly reduce the seismic response. Comparing the experiment results with analytical results obtained from the nonlinear analysis program, NAST, we can well predict the nonlinear behavior of the structure with LADASs during earthquakes.
49
Chang, Shing-Ming, and 張欣閔. "Rectangular embeded foundation's stiffness and damping for layer soil." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/02073167563892008732.
Full text
50
Huang, Chih-Ching, and 黃志清. "Estimation and Verification of Stiffness Coefficients for Ball Bearings." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/03701733149316793805.
Full textAbstract:
博士中原大學
機械工程研究所
94
The Jones-Harris methods (JHM) is widely and generally used by designers and engineers to determine stiffness coefficients for ball bearings. The JHM, however, involves the determination of coupled and non-linear, simultaneous equations with complex inputs and iterative calculations. This causes the method to be difficult and time-consuming for designers and engineers. All ball bearings have the similar features in geometry, mechanism, and structure. The stiffness of this type of bearings can be related to geometry, dimension, and operating conditions by a very complex function. This study presents this stiffness function for all ball bearings by a back-propagation neural network method (BPNN), which is trained by using several (not all) samples. When this BPNN is utilized by a bearing designer, few input data are requested and a determination result can be accurately obtained with very short time. The JHM didn’t consider the actual mounting and operating condition of bearings in rotor bearing systems. The dynamic analysis of system would lead to the discrepancy between measurements and predictions. The technique of parameter identification is used to estimate bearing dynamic coefficients from input-output measurements of the system. The estimated results would satisfy the actual condition for the analysis and design of rotor machinery. This study also presents that a simple identified algorithm of bearing dynamic coefficients is developed in flexible rotor systems. In practical operation, the sensor of unbalance responses cannot be mounted at bearing position in systems. On basis of mechanical impedance technique, the measured unbalance responses on two nodes of shaft at adjacent bearing position are employed to determine the unbalance responses on the node of shaft at bearings position. It would overcome the limitation of sensors mounting and reduce the estimated error. Moreover, the experimental accuracy of bearing dynamic coefficients is also verified by the comparison between rotor kit and estimated system model of the frequency response functions. Additionally, the characteristic of dynamic parameters of ball bearing with frequency is also discussed by the case of SKF 6001 deep-groove ball bearing.