Dissertations / Theses: 'Dynamic damping'

1

Ting-Kong, Christopher. "Design of an adaptive dynamic vibration absorber." Title page, contents and abstract only, 1998. http://thesis.library.adelaide.edu.au/adt-SUA/public/adt-SUA20010220.212153.

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2

KONDEPUDI, RAMABALARAJENDRASESH. "NUMERICAL ANALYSIS OF LUMPED PARAMETER DYNAMIC SYSTEMS WITH FRICTION." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1083622496.

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3

Alagiyawanna, Krishanthi. "Evaluation of Nonlinear Damping Effects on Buildings." Scholarly Repository, 2007. http://scholarlyrepository.miami.edu/oa_theses/110.

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Analysis of the dynamic behavior on structures is one vital aspect of designing structures such as buildings and bridges. Determination of the correct damping factor is of critical importance as it is the governing factor of dynamic design. Damping on structures exhibits a very complex behavior. Different models are suggested in literature to explain damping behavior. The usefulness of a valid damping model depends on how easily it can be adopted to analyze the dynamic behavior. Ease of mathematically representing the model and ease of analyzing the dynamic behavior by using the mathematical representation are the two determining aspects of the utility of the selected model. This thesis presents a parametric representation of non-linear damping models of the form presented by [Jea86] and the mathematical techniques to use the parametrically represented damping model in dynamic behavior analysis. In the damping model used in this thesis, the damping factor is proportional to the amplitude of vibration of the structure. However, determination of the amplitude again depends on the damping of the structure for a given excitation. Also, the equations which explain the behavior of motion are differential equations in a matrix form that is generally linearly inseparable. This thesis addresses these challenges and presents a numerical method to solve the motion equations by using Runge-Kutta techniques. This enables one to use a given non-linear model of the form proposed by [Jea86] to analyze the actual response of the structure to a given excitation from wind, seismic or any other source. Several experiments were conducted for reinforced concrete and steel framed buildings to evaluate the proposed framework. The non-linear damping model proposed by [Sat03], which conforms to [Jea86] is used to demonstrate the use of the proposed techniques. Finally, a new damping model is proposed based on the actual behavior and the serviceability criteria, which better explains the damping behavior of structures.

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4

Lane, Jeffrey Scott. "Control of dynamic systems using semi-active friction damping." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/16020.

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Liu, Xueying. "Dynamic Response of Flexible Pipes Considering Different Damping Models." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26253.

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Flexible pipe is a layered structure composed of plastic and steel materials. Under a large bending moment, the pipe layers may slide relative to each other due to internal friction. The moment curvature relationship for the flexible pipe is a tri-linear curve. Under cyclic bending moment, a hysteresis loop will be formed in the moment curvature curve. The area of the loop is the energy loss due to the internal friction. This thesis is aimed to study the effects of hysteresis damping on the global analysis of the flexible riser. To begin with, a review on the flexible pipe technology and nonlinear finite element method is performed. Then a local analysis is carried out in BFLEX to obtain the cross sectional characteristics. Then the global analysis is conducted to study the responses of the flexible riser in terms of the curvature, moment and axial force. From the study, slip behavior only occurs at the hang off part of the riser. For the rest part, pipe layers stay in the stick regime, meaning there is no energy loss due to the internal friction. Therefore for the global analysis of the flexible riser, there is no need to further study the equivalent linear damping models. In addition, the influence of linear and nonlinear bending models on the global response of the riser is investigated. It is found that the current standard industrial practice, namely applying the linear bending model with the full slip bending stiffness, gives an over conservative response prediction. It is therefore recommended to use the physically correct nonlinear moment curvature relationship for the global analysis of flexible riser.

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Vachon, Maryse. "Dynamic response of 3D printed beams with damping layers." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99629.

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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 45).
3D printers are a relatively new technology and they could be used in the future to 3D print structural components in buildings or bridges. The main advantages of using 3D printing would be the optimization of the structures. Effectively, with 3D printers, it is possible to generate polymers with different strengths and stiffnesses in the same structure. It is also possible to print very complex shapes and forms. This thesis will focuses on the dynamic response of 3D printed beams with damping layers. More precisely, natural frequency and damping ratio will be analysed in order to find the optimal location of the damping layers. For this experiment, three methods are used, one with an accelerometer, one with a high speed camera and one with a piezoelectric actuator. Characterization of the 3D printed material has been made to predict results. For the results, it is possible to conclude that using softer material as damping layer reduces the beam frequencies but increases the damping ratio. Also, in order to get the most efficient beam in terms of damping properties, the damping layers need to be close to the top and bottom surfaces as strains are larger. Finally, it can be say that a high speed camera is the best device to investigate the dynamic response of 3D printed materials.
by Maryse Vachon.
M. Eng.

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7

Majid, W. M. W. A. "The dynamic analysis of offshore heavy lift operations." Thesis, City University London, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375821.

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8

Holk, Michael A. "A dynamic damping device for payload pendulations of construction cranes." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-05022009-040332/.

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9

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.

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Meng, Jiewu. "The influence of loading frequency on dynamic soil properties." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/19012.

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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.

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12

Iglesias, Angel Moises. "Investigating Various Modal Analysis Extraction Techniques to Estimate Damping Ratio." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/35890.

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Many researchers have devoted their work to the development of modal analysis extraction techniques in order to obtain more reliable identification of the modal parameters. Also, as a consequence of all this work, there are some other works devoted to the evaluation and comparison of these methods in order to find which one is the most reliable method with respect to certain characteristics. In this thesis the Rational Fraction Polynomial (RFP) Method, the Prony or Complex Exponential Method (CEM), the Ibrahim Time Domain (ITD) Method, and Hilbert Envelope Method are used to evaluate how the accuracy of the damping ratio is affected with respect to various parameters and conditions. The investigation focuses in the estimation of damping ratio because among the modal parameters, it is the most difficult to model. Each method is evaluated individually in order to understand how the damping ratio estimation is affected with respect to each method when the characteristics of the FRF are changed. Also, they are compared to show that, in general, the Rational Fraction Polynomial Method is a more reliable method than the other methods. To investigate this, a simulated analytical data and an experimental data are processed to estimate the modal parameters, but focusing in the damping ratio. For the simulated analytical data the damping ratio's percent of error were calculated. The highest damping ratio's percent of error of the RFP was 0.0073501%. In the other hand, for the CEM, ITD, and Hilbert Envelope Method their highest damping ratio's percent of error were 83.02%, 99.82%, and 4.077%, respectively.
Master of Science

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13

Cheng, Yi-Pen. "Frequency domain identification of structural dynamic systems with general damping matrices." Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/12494.

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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.

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Darrouj, Mtanos N. "Dynamic damping properties of elastomers and composite panels for low noise diesel engines." Thesis, Loughborough University, 1987. https://dspace.lboro.ac.uk/2134/7493.

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The most practical treatment for reducing the noise of present diesel engines is to replace the thin-section, noise-radiating components with constrained damping layers, where a viscoelastic layer is sandwiched between two elastic layers to give the composite panel high damping characteristics. The damping ability of such panels is highly dependent on dynamic shear properties of viscoelastic materials as well as on the selection of elastic materials. The damping shear properties of viscoelastic materials are highly dependent on frequency and temperature. Experimental data on the damping properties of viscoelastic materials are, so far, limited to a small low frequency range. The forced vibration non-resonant technique is adopted in the present investigation. Atest rig has been designed, built and developed to measure the dynamic shear properties of some visoelastic materials over a wide range of temperature (40 to 1000C). These properties are also measured over a wide range of frequency (50-1500 Hz), covering part of the audio frequency range, in which the severity of engine noise occurs. Polysulphide rubber and ethylene propylene rubber have been tested. Their dynamic shear properties have been obtained, tabulated and plotted as functions of frequency and temperature. The effect of strain amplitude has been investigated and discussed. A new approach for an easy, fast and direct measurement of the loss shear modulus has been proposed. It has been found that both viscoelastic materials possess considerable damping, especially over the frequency range of 900-1500 Hz. The effect of strain amplitude was found negligible. The optimum design and damping ability of three layer composite panels have been investigated. The effects of elastic and viscoelastic material on the damping of these panels has been examined. Magnesium has been found to be a superior elastic material of those investigated. Aluminium is the next most suitable elastic material, with steel as the least suitable elastic material. Polysulphide rubber and ethylene propylene rubber have been found suitable for use in composite damping panels, but their relative attractiveness is strongly dependent on frequency and temperature.

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16

Bleichner, Noah G. "A Comparative Study on Seismic Analysis Methods and the Response of Systems with Classical and Nonclassical Damping." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2219.

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This thesis investigated the application of seismic analysis methods and the response of idealized shear frames subjected to seismic loading. To complete this research, a Design Basis Earthquake (DBE) for a project site in San Luis Obispo, CA, and five past earthquake records were considered. The DBE was produced per the American Society of Civil Engineers’ Minimum Design Loads for Buildings and Other Structures (ASCE 7-10) and used for application of the Equivalent Lateral Force Procedure (ELFP) and Response Spectrum Analysis (RSA). When applying RSA, the modal peak responses were combined using the Absolute Sum (ABS), Square-Root-of-the-Sum-of-Squares (SRSS), and Complete Quadratic Combination (CQC) method. MATLAB scripts were developed to produce several displacement, velocity, and acceleration spectrums for each earthquake. Moreover, MATLAB scripts were written to yield both analytical and numerical solutions for each system through application of Linear Time History Analysis (THA). To obtain analytical solutions, two implicit forms of the Newmark-beta Method were employed: the Average Acceleration Method and the Linear Acceleration Method. To generate a comparison, the ELFP, RSA, and THA methods were applied to shear frames up to ten stories in height. The system parameters that impacted the accuracy of each method and the response of the systems were analyzed, including the effects of classical damping and nonclassical damping models. In addition to varying levels of Rayleigh damping, non-linear hysteric friction spring dampers (FSDs) were implemented into the systems. The design of the FSDs was based on target stiffness values, which were defined as portions of the system’s lateral stiffness. To perform the required Nonlinear Time History Analysis (NTHA), a SAP2000 model was developed. The efficiencies of the FSDs at each target stiffness, with and without the addition of low levels of viscous modal damping are analyzed. It was concluded that the ELFP should be supplemented by RSA when performing seismic response analysis. Regardless of system parameters, the ELFP yielded system responses 30% to 50% higher than RSA when combing responses with the SRSS or CQC method. When applying RSA, the ABS method produced inconsistent and inaccurate results, whereas the SRSS and CQC results were similar for regular, symmetric systems. Generally, the SRSS and CQC results were within 5% of the analytical solution yielded through THA. On the contrary, for irregular structures, the SRSS method significantly underestimated the response, and the CQC method was four to five times more accurate. Additionally, both the Average Acceleration Method and Linear Acceleration Method yielded numerical solutions with errors typically below 1% when compared with the analytical solution. When implemented into the systems, the FSDs proved to be most efficient when designed to have stiffnesses that were 50% of the lateral stiffness of each story. The addition of 1% modal damping to the FSDs resulted in quicker energy dissipation without significantly reducing the peak response of the system. At a stiffness of 50%, the FSDs reduced the displacement response by 40% to 60% when compared with 5% modal damping. Additionally, the FSDs at low stiffnesses exhibited the effects of negative lateral stiffness due to P-delta effects when the earthquake ground motions were too weak to induce sliding in the ring assemblies.

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17

Liu, Chih-Hsing. "A finite element based dynamic modeling method for design analysis of flexible multibody systems." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/39605.

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This thesis develops a finite element based dynamic modeling method for design and analysis of compliant mechanisms which transfer input force, displacement and energy through elastic deformations. Most published analyses have largely based on quasi-static and lump-parameter models neglecting the effects of damping, torsion, complex geometry, and nonlinearity of deformable contacts. For applications such as handling of objects by the robotic hands with multiple high-damped compliant fingers, there is a need for a dynamic model capable of analyzing the flexible multibody system. This research begins with the formulation of the explicit dynamic finite element method (FEM) which takes into account the effects of damping, complex geometry and contact nonlinearity. The numerical stability is considered by evaluating the critical time step in terms of material properties and mesh quality. A general framework incorporating explicit dynamic FEM, topology optimization, modal analysis, and damping identification has been developed. Unlike previous studies commonly focusing on geometry optimization, this research considers both geometric and operating parameters for evaluation where the dynamic performance and trajectory of the multibody motion are particularly interested. The dynamic response and contact behavior of the rotating fingers acting on the fixed and moving objects are validated by comparing against published experimental results. The effectiveness of the dynamic modeling method, which relaxes the quasi-static assumption, has been demonstrated in the analyses of developing an automated transfer system involved grasping and handling objects by the compliant robotic hands. This FEM based dynamic model offers a more realistic simulation and a better understanding of the multibody motion for improving future design. It is expected that the method presented here can be applied to a spectrum of engineering applications where flexible multibody dynamics plays a significant role.

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18

Smith, Tobias. "Post-tensioned Timber Frames with Supplemental Damping Devices." Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2014. http://hdl.handle.net/10092/9217.

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In recent years the public expectation of what is acceptable in seismic resisting construction has changed significantly. Engineers today live under demands which are far more intensive than their historical counterparts and recent seismic events have shown that preserving life is no longer sufficient, and a preservation of livelihood is now the minimum. This means that after a major seismic event a building should not only be intact but be usable with no or minimal post-quake intervention. In addition to this already high expectation these demands must be met in a green and sustainable fashion with minimal (or even negative) environmental impact. This doctoral project looks to further advance the research into a new and innovative method of timber construction which satisfies (and exceeds) these demands. In response to these higher expectations recent developments in the field of seismic design have led to the development of damage control design philosophies and innovative seismic resistant systems. Jointed ductile connections for precast concrete structures have been implemented and successfully validated. One of these systems, referred to as the hybrid system, combines the use of unbonded post-tensioned tendons with grouted longitudinal mild steel bars or any other form of dissipation reinforcing device. During the controlled rocking of the system under seismic loading the post-tensioning provides desirable recentering properties, while the devices allow adequate energy dissipation from the system as well as increased moment resistance at column bases and beam-column connections. The hybrid concept is material independent and in 2004 an extensive campaign was begun to investigate the performance of the hybrid system when applied to large engineered timber members. Numerous small and large scale tests on both subassemblies and full buildings were performed showing that post-tensioned timber meets the seismic resilience demands now imposed by society. Recently this technology has also been applied in practice with over ten structures now using post-tensioned timber walls or frames, or a combination of the two, in New Zealand. In-spite of the extensive research effort and the acceptance and adoption in practice of post-tensioned timber as a structural system, significant work was still required in the review and refinement of both the system itself and the analytical and numerical methods used to predict and analyse structural performance. The objectives of this research were to review and refine comprehension of the static and dynamic response, analytical and numerical modelling, and design of post-tensioned timber frames under lateral loading. In order to do this a three phase experimental testing campaign was devised and performed including quasi-static testing of an angle dissipative reinforcing device, quasi-static testing of a full-scale beam-column joint and the mono-directional dynamic testing of a 2/3rd scale three storey frame. All testing used glue laminated timber, which had not been previously used in post-tensioned timber structures. Insight gained from the experimental testing was used to analyse and refine existing analytical modelling techniques. These techniques were split into two categories: 1) modelling of the local behaviour of a post-tensioned timber beam-column joint, with particular focus on stiffness and energy dissipation capacity, and 2) evaluation of the seismic demand (in the form of design base shear) on post-tensioned timber frames looking at current Force Based (FBD) and Displacement Based (DBD) design methods. This analysis led to the development of recommended alterations in the existing beam-column joint analytical procedure enabling the procedure to provide better prediction of initial and post-yield stiffness. Analysis of the FBD and DBD procedures showed that both methods are capable of providing accurate prediction of seismic demand provided correct assumptions are made regarding system ductility and damping characteristics. Recommendations have been made on how designers can ensure that assumptions are either sufficiently accurate in the beginning of a design or require minimal iteration to be performed. Current numerical modelling techniques have also been compared against the quasi-static and dynamic testing results providing confidence in their accuracy when applied to post-tensioned timber frames. Modelling techniques were also extended to the widely used SAP2000 modelling programme which had not been previously used in post-tensioned timber research. Although many observations and conclusions were made, a common theme continued throughout this research. This was the importance of the deep understanding of displacements within a post-tensioned timber frame and the impact of these displacements on frame performance. Displacements occur throughout a frame in dissipative reinforcing devices, in the connection of these devices, in beams, columns and joint panels as well as at the interfaces between members. When these displacements are allowed for through proper design excellent seismic performance, possible using this innovative system, is obtained.

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19

Ramesh, Periyakulam S. "Experimental design and results of 2D dynamic damping of payload motion for cranes." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-07102009-040346/.

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20

So, Ping Lam. "The damping of inter-area oscillations in power systems with controllable phase shifters." Thesis, Imperial College London, 1997. http://hdl.handle.net/10044/1/7739.

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21

Aubuchon, Vanessa V. "Damping Effects of Drogue Parachutes on Orion Crew Module Dynamics." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23327.

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Currently, simulation predictions of the Orion Crew Module (CM) dynamics with drogue parachutes deployed are under-predicting the amount of damping as seen in free-flight tests. The Apollo Legacy Chute Damping model has been resurrected and applied to the Orion system. The legacy model has been applied to predict CM damping under drogue parachutes for both Vertical Spin Tunnel free flights and the Pad Abort-1 flight test. Comparisons between the legacy Apollo prediction method and test data are favorable. A key hypothesis in the Apollo legacy drogue damping analysis is that the drogue parachutes\' net load vector aligns with the CM drogue attachment point velocity vector. This assumption seems reasonable and produces good results, but has never been experimentally verified. The wake of the CM influences the drogue parachutes, which makes performance predictions of the parachutes difficult. Many of these effects are not currently modeled in the simulations.

A forced oscillation test of the CM with parachutes was conducted in the NASA LaRC 20-Ft Vertical Spin Tunnel (VST) to gather additional data to validate and refine the Apollo legacy drogue model. A second loads balance was added to the original Orion VST model to measure the drogue parachute loads independently of the CM. The objective of the test was to identify the contribution of the drogues to CM damping and provide additional information to quantify wake effects and the interactions between the CM and parachutes. The drogue parachute force vector was shown to be highly dependent on the CM wake characteristics. Based on these wind tunnel test data, the Apollo Legacy Chute Damping model was determined to be a sufficient approximation of the parachute dynamics in relationship to the CM dynamics for preliminary entry vehicle system design. More wake effects should be included to better model the system. These results are being used to improve simulation model fidelity of CM flight with drogues deployed, which has been identified by the project as key to a successful Orion Critical Design Review.
Master of Science

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22

Zweber, Jeffrey Vincent. "A method for structural dynamic model updating via the estimation of damping parameters." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/12447.

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Sareen, Ashish Kumar. "Rotorcraft airframe structural optimization for vibration and dynamic stress reduction including damping treatment." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/12951.

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Cordiner, Christopher. "An investigation of the static and dynamic characteristics of large turbo-generator bearings." Thesis, Northumbria University, 2000. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325377.

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Muluka, Venu. "Optimal suspension damping and axle vibration absorber for reduction of dynamic tire loads." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0005/MQ39479.pdf.

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Bose, Mrinal Kanti. "NON-CLASSICAL DAMPING PROPERTIES AND MODAL CORRELATION COEFFICIENT FOR DYNAMIC ANALYSIS OF STRUCTURES." NCSU, 2001. http://www.lib.ncsu.edu/theses/available/etd-20010305-150413.

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BOSE, MRINAL KANTI. Non-Classical Damping Properties and Modal Correlation Coefficient for Dynamic Analysis of Structures. (Under the direction of Abhinav Gupta and Ajaya Gupta.)The seismic response of secondary systems depends, in addition to their uncoupled dynamic characteristics, on the interaction with primary structures supporting them. This dissertation presents a verification study of the formulations to evaluate the seismic response of non-classically damped building-piping systems by modal synthesis approach. The existing studies consider only simple representative primary-secondary systems. No real-life like coupled system such as building-piping was used in these studies. Further, the majority of simple systems considered in these studies do not represent realistic coupled systems with significant effect of non-classical damping as they have either high values of mass ratios or systems with detuned modes.In this dissertation, different configurations of simple representative systems as well as real-life like building-piping systems are considered. Responses obtained from modal superposition time history analyses as well as response spectrum analyses are compared with the corresponding responses obtained by Brookhaven National Laboratory from the direct integration time history analyses. Modal superposition time history analyses results and direct integration time history analyses results are almost identical. The mean and standard deviation of responses from response spectrum analyses are close to the corresponding values evaluated using direct integration time history analysis. In addition to the verification results, a detailed discussion is also presented on the significance of non-classical damping. It is shown that the effect of non-classical damping is significant in systems that have nearly tuned modes and sufficiently small values of modal mass ratios. It is also illustrated that composite modal damping is an alternate form of classical damping that can result in incorrect responses in non-classically damped systems. Possible reasons for numerical and modeling differences that can occur in real-life like building-piping system are identified and their effect on the dynamic characteristics of the coupled system is illustrated.In the response spectrum method, the maximum modal responses are combined using an appropriate formulation for the modal correlation coefficient. This dissertation presents a new formulation which is based on the observation that the response spectrum method is a design method such that the statistical values of responses evaluated from multiple time history analyses should be close to the corresponding values obtained from the response spectrum method. Results from a numerical study using several real earthquake records are used to develop the new formulation. Different expressions are proposed for combining modal responses that have same algebraic sign and for those that have opposite algebraic signs.

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Shin, Hyunkyoung. "Numerical solution of the cable dynamic equations using the linearized equivalent damping force." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15280.

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Thesis (Ocean E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1985.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.
Bibliography: leaves 62-63.
by Hyunkyoung Shin.
Ocean E.

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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/.

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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.

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Ayoub, Ayoub, and Carl Martin Berg. "Design of a Dynamic Boom Suspension System in a Hybrid Wheel Loader." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-39740.

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Wheel loaders are under the influence of low frequency vibrations that may be harmful for the health of the operator, and for the productivity of the machine. The strong vibrations can significantly impact the operation of the machine since they are not equipped with wheel suspension systems and due to their work environment in rough terrains with uneven surfaces. The risk of spilling or dropping the load is also increased and they can introduce higher mechanical stress that can wear out parts faster. The focus of this thesis work is to develop an approach for damping these vibrations dynamically by improving the functionality of the electrohydraulic system in Volvo's prototype wheel loader LX1. The dynamic damping system controls the cylinder of the lift framework to make it behave as a damper. The system utilizes the lift cylinder pressure and piston position as feedback to adjust the oil flow in the cylinder using the proposed control system. Results indicate that the proposed technique is capable of attenuation that is comparable with the existing boom suspension system based on accumulators through simulations and experimental tests.

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30

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.

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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.

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31

Hornig, Klaus H. Flowers George T. "Heuristic optimization methods for the characterization of dynamic mechanical properties of composite materials." Auburn, Ala., 2007. http://repo.lib.auburn.edu/2006%20Fall/Dissertations/HORNIG_KLAUS_7.pdf.

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Lo, Kai Fung. "Small-strain shear modulus and damping ratio determination by bender element /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202005%20LOK.

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Vo, Van Olivier. "Introduction of variability into pantograph-catenary dynamic simulations." Thesis, Paris, ENSAM, 2016. http://www.theses.fr/2016ENAM0021/document.

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L’alimentation électrique des trains s’effectue en général par une interface pantographecaténairereprésentant un système mécanique couplé complexe. Les phénomènes dynamiques intervenantdans l’interaction entre le pantographe et la caténaire sont encore mal connus. Par ailleurs, le comportementdynamique du système est très variable car sensible à de nombreux paramètres. La premièrecontribution de cette thèse est de proposer une analyse détaillée de l’interaction dynamique pantographecaténaireen étudiant en particulier la réponse dynamique du pantographe à la géométrie de la caténaireainsi que les propagations, réflexions et transmissions des ondes dans cette dernière. Il a ainsi été démontréque la coïncidence spatiale, temporelle ou fréquentielle de ces différents phénomènes est à l’originede la majorité des variations des quantités d’intérêt. Par ailleurs, l’étude des ondes a montré que lespendules entourant le poteau avaient une importance particulière dans l’interaction dynamique et que lesparamètres tels que le rapport des impédances dynamiques et la somme des vitesses des ondes dans lescâbles étaient des variables dimensionnantes dans la caténaire. La seconde contribution a été de réduireles principales incertitudes épistémiques liées au modèle telles que l’amortissement dans la caténaire, laraideur de contact et la taille des éléments. La dernière contribution était d’implémenter des paramètresvariables dans le modèle en utilisant les mesures disponibles. À partir de ce modèle aléatoire, les incertitudesont été classées en utilisant les indices de Sobol sur des critères géométriques et dynamiques.L’absence de corrélation entre les critères géométriques et dynamique observée a des conséquences notablessur la politique de maintenance. Enfin, le grand nombre d’études de sensibilités réalisés a permisde souligner la maturité de l’outil de simulation et de proposer des orientations pour les travaux futurs pourla conception, maintenance ou homologation de pantographes ou de caténaires
In railways, electrical current is generally collected by the train through a complex coupledmechanical system composed of a pantograph and a catenary. Dynamic phenomena that occur duringtheir interaction are still not fully understood. Furthermore, the system behaviour is sensitive to numerousparameters and thus highly variable. The first contribution of this thesis is a detailed analysis of thepantograph-catenary dynamic interaction separating phenomena due to the dynamic response of the pantographto the catenary geometry from wave propagations, reflections and transmissions that occur in thecatenary. The coincidence of frequencies or characteristic times is then shown to explain most variationsin the quantities of interest. Moreover, droppers surrounding the mast have been shown to be particularlyimportant in dynamic interaction. Ratio of wire impedances and sum of wave velocities also appeared tobe dimensioning quantities for catenary design. The second contribution was to reduce epistemic uncertaintylinked with model parameters such as catenary damping, contact stiffness and element size. Thefinal contribution was to use the model in a configuration with random parameters. An initial step was tostatistically characterise physical catenary parameters using available measurements. From this randommodel, ranking of uncertainties using Sobol indices on static and dynamic criteria was shown to be possible.An absence of correlation between geometric and dynamic criteria was also found, which has notableimplications for maintenance policies. The high number of sensitivity studies also gave the occasion tohighlight the maturity of simulation tool and propose directions for further work on design, maintenance orcertification of pantographs and catenaries

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34

Zou, Xiaolan. "Frequency and Damping Characteristics of Generators in Power Systems." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/81937.

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A power system stability is essential for maintaining the power system oscillation frequency within a small and acceptable interval around its nominal frequency. Hence, it is necessary to study and control the frequency for stable operation of a power system by knowing the characteristics within a power system. One approach is to understand the effectiveness of frequency and damping characteristics of generators in power systems. Hence, the simulation analysis of IEEE 118-bus power system is used for this study. The analysis includes theoretical analysis with a mathematical approach and simulation studies of swing equation to determine the characteristics of damped single-machine infinite bus, which is represented as a generator connects to a large network system with a small signal disturbance by line losses. Additionally, mathematical derivation of Prony analysis is presented in order to estimate the frequency and damping ratio of the simulation results. In the end, the results demonstrate that the frequency and damping characteristics of generators are highly dependent on the system inertia constant. Therefore, the higher inertia constant is a critical factor to ensure the system is more stable.
Master of Science

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35

Nehr, Jonas Christian. "Damping and Thermomechanical behaviour of CFRP laminates modified with rubbery nanofibers." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21702/.

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Nanofibrous membranes are a promising material for tailoring the properties of laminated CFRP composites by embedding them into the structure. This project aimed to understand the effect of number, position and thickness of nanofibrous modifications specifically on the damping behaviour of the resulting nano-modified CFRP composite with an epoxy matrix. An improvement of damping capacity is expected to improve a composites lifetime and fatigue resistance by prohibiting the formation of microcracks and consequently hindering delamination, it also promises a rise in comfort for a range of final products by intermission of vibration propagation and therefore diminution of noise. Electrospinning was the technique employed to produce nanofibrous membranes from a blend of polymeric solutions. SEM, WAXS and DSC were utilised to evaluate the quality of the obtained membranes before they were introduced, following a specific stacking sequence, in the production process of the laminate. A suitable curing cycle in an autoclave was applied to mend the modifications together with the matrix material, ensuring full crosslinking of the matrix and therefore finalising the production process. DMA was exercised in order to gain an understanding about the effects of the different modifications on the properties of the composite. During this investigation it became apparent that a high number of modifications of laminate CFRP composites, with an epoxy matrix, with thick rubbery nanofibrous membranes has a positive effect on the damping capacity and the temperature range the effect applies in. A suggestion for subsequent studies as well as a recommendation for the production of nano-modified CFRP structures is included at the end of this document.

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Balupari, Raja Shekar. "VALIDATION OF FINITE ELEMENT PROGRAM FOR JOURNAL BEARINGS -- STATIC AND DYNAMIC PROPERTIES." UKnowledge, 2004. http://uknowledge.uky.edu/gradschool_theses/325.

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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.

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37

Moreira, Alfonso. "Characterization and dynamic analysis of damping effects in composite materials for high-speed flywheel applications." Auburn, Ala., 2007. http://repo.lib.auburn.edu/2007%20Spring%20Dissertations/MOREIRA_ALFONSO_55.pdf.

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38

Chin, Victor B. L. "The dynamic response of pile-soil interfaces during pile driving and dynamic testing events." Monash University, Dept. of Civil Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/9421.

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39

Ankouni, Mouhamad. "Modeling of damping in elastohydrodynamic lubricated contacts : Application to gear dynamics." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI089/document.

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Les principaux mécanismes d'amortissement présents dans les transmissions par engrenages sont étudiés, en se basant sur une analyse transitoire du problème de lubrification élasto-hydrodynamique dans les contacts linéiques. Plusieurs modèles linéaires sont proposés suite à de nombreuses simulations numériques, permettant de prédire l’amortissement du lubrifiant dans les différentes conditions de contact, y compris les situations des pertes de contact momentanées suivies d’impact. Un modèle dynamique d’engrenage à un seul degré de liberté est présenté qui combine les contributions diverses du lubrifiant à l'amortissement structurel représentatif de la dissipation interne des engrenages. Un certain nombre de comparaisons avec des résultats expérimentaux est présenté pour une gamme de conditions de fonctionnement et de géométries d'engrenages, qui prouve la capacité du modèle à reproduire proprement le comportement dynamique des engrenages droits. On montre que l'amortissement associé au lubrifiant contribue essentiellement lors des pertes de contact et des chocs entre dentures se produisant au voisinage des vitesses critiques. Le cas des engrenages hélicoïdaux est analysé différemment du fait de l’absence de perte de contact pour ce type d’engrenage. Un modèle tridimensionnel simple est ainsi développé qui prend en compte la dissipation des différents éléments de la transmission. Un nombre de résultats est présenté qui, d'abord, confirme la contribution majeure de l'engrènement à l'amortissement global des engrenages droits, et, dans un second lieu, montre que les paliers constituent la principale source d'amortissement dans les transmissions par engrenages hélicoïdaux
The primary damping mechanisms present in geared systems are investigated based on a transient analysis of the elasto-hydrodynamic lubrication problem for line contacts. Several linear models are derived from extensive numerical simulations, which make it possible to simulate the damping caused by the lubricant squeezing by the teeth with and without momentary contact losses and impacts. A one-degree-of-freedom gear dynamic model is set up which combines these lubricant damping sources along with structural damping that reproduces the internal dissipation in gear elements. A number of comparisons with benchmark experimental evidence are presented for a range of operating conditions and gear geometries, which prove that the proposed approach is sound in the case of spur gears. It is shown that the damping associated with lubricant squeezing contributes for the most part when contact losses and shocks between the teeth occur at critical speeds. The case of helical gears is analyzed differently since no contact loss occurs for such gears. A simple three-dimensional model is thus developed which accounts for the dissipation in the mechanical parts surrounding the gears. A number of results are presented which, first, confirm the primary contribution of the gear mesh to the overall damping in spur gears, and second, show that bearings constitute the main source of damping in helical gears transmissions

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Huang, He. "Large-Amplitude Vibration of Imperfect Rectangular, Circular and Laminated Plate with Viscous Damping." ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1924.

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Large-amplitude vibration of thin plates and shells has been critical design issues for many engineering structures. The increasingly more stringent safety requirements and the discovery of new materials with amazingly superior properties have further focused the attention of research on this area. This thesis deals with the vibration problem of rectangular, circular and angle-ply composite plates. This vibration can be triggered by an initial vibration amplitude, or an initial velocity, or both. Four types of boundary conditions including simply supported and clamped combined with in-plane movable/immovable are considered. To solve the differential equation generated from the vibration problem, Lindstedt's perturbation technique and Runge-Kutta method are applied. In previous works, this problem was solved by Lindstedt's Perturbation Technique. This technique can lead to a quick approximate solution. Yet based on mathematical assumptions, the solution will no longer be accurate for large amplitude vibration, especially when a significant amount of imperfection is considered. Thus Runge-Kutta method is introduced to solve this problem numerically. The comparison between both methods has shown the validity of the Lindstedt's Perturbation Technique is generally within half plate thickness. For a structure with a sufficiently large geometric imperfection, the vibration can be represented as a well-known backbone curve transforming from soften-spring to harden-spring. By parameter variation, the effects of imperfection, damping ratio, boundary conditions, wave numbers, young's modulus and a dozen more related properties are studied. Other interesting research results such as the dynamic failure caused by out-of-bound vibration and the change of vibration mode due to damping are also revealed.

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Kruep, Stephanie Jean. "Using Incremental Dynamic Analysis to Visualize the Effects of Viscous Fluid Dampers on Steel Moment Frame Drift." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/34122.

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This thesis presents the details of a study regarding both the use of linear viscous fluid dampers in controlling the interstory drift in steel moment frames, and the use of incremental dynamic analysis as a method of visualizing the behavior of these moment frames when subjected to seismic load effects. Models of three story and nine story steel moment frames were designed to meet typical strength requirements for office buildings in Seattle, Washington. These models were intentionally designed to violate seismic interstory drift restrictions to test the ability of the linear viscous fluid dampers to reduce these drifts to the point of code compliance. Dampers were included in one bay of every story in each model. These devices were used to produce total structural damping ratios of 5%, 10%, 20%, and 30% of critical. Undamped, traditional stiffness controlled models of both three stories and nine stories were also created for comparison purposes. Incremental dynamic analysis was used to subject these models to ten ground motions, each scaled to twenty incremental levels. Two new computer applications were written to facilitate this process. The results of these analyses were studied to determine if the linear viscous fluid dampers were able to cause compliance with codified drift limits. Also, incremental dynamic analysis plots were created to examine the effects of the dampers on structural behavior as damping increased from inherent to 30% of critical. It was found that including linear viscous fluid dampers in steel moment frame design can satisfactorily control interstory drift, and incremental dynamic analysis is a beneficial tool in visualizing dynamic structural behavior.
Master of Science

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42

Nyman, Timmy. "Experimental Investigation of Added Mass and Damping on a Model Kaplan Turbine for Rotor Dynamic Analysis." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-67573.

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The concept of added hydrodynamic properties such as added mass is of importance in modern hydropower development, mainly for rotor dynamic calculations. Added mass could result in reduced natural frequencies and altered mode compared to existing simulation models. It is of importance to quantify added mass but also added damping to make the simulation models more accurate. Experiments are conducted on a model Kaplan turbine, D = 0,5 m, and a steel cube, S = 0,2 m, for linear vibrations in still water confined in a cylindrical tank. The experiments are conducted in air and water for evaluation of added forces. The vibrations are generated with an electrodynamic vibration exciter with a frequency range of approximately 1-10 Hz with amplitudes 0,5-3 mm. The experiments were repeated to check test rig reliability. Each individual working point [frequency, amplitude] were in total tested 40 times in 15 s intervals. The added mass was found to be function of acceleration for the model Kaplan with an increase in added mass from 10 % at 4 m/s2 to 35 % at 0,5 m/s2. The damping forces was at best measured at ±30 %, making added damping calculations unreliable. The cube experiments resulted in small differences between water and air. Cube results must be interpreted with caution due to test rig uncertainties.

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Chinnakonda, Manoj Kumar M. "Exact solution of time history response for dynamic systems with coupled damping using complex mode superposition." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1202409818/.

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44

Davis, Roosevelt. "Determinig dynamic properties of elastic coupling using experimental data and finite element analysis." Master's thesis, Mississippi State : Mississippi State University, 2003. http://library.msstate.edu/etd/show.asp?etd=etd-07242003-163336.

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45

Choi, Jiduck. "Investigation of the dynamic behavior of a cable-harnessed structure." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/49114.

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To obtain predictive modeling of a spacecraft, the author investigates the effects of adding cables to a simple structure with the goal of developing an understanding of how cables interacting with a structure. In this research, the author presents predictive and accurate modeling of a cable-harnessed structure by means of the Spectral Element Method (SEM). A double beam model is used to emulate a cable-harnessed structure. SEM modeling can define the location and the number of connections between the two beams in a convenient fashion. The proposed modeling is applied and compared with the conventional FEM. The modeling approach was compared to and validated by measurement data. The validated modeling was implemented to investigate the effect of the number of connections, of the spring stiffness of interconnections, and of mass portion of an attached cable. Damping has an important role in structural design because it reduces the dynamic response, thereby avoiding excessive deflection or stress, fatigue loads, and settling times. Experimental results with some specimens indicate a clear change of damping on the main structure with the inclusion of cable dynamics. The author investigated the modification of the damping of the host structure induced by various attached cables. The identification of a damping matrix is performed using measured data. The effect of the flexibility of a cable harness on damping is observed through experiments with various types of cables. The effect of the number of connections on damping is also investigated by changing the number of connections. Moreover, to overcome the sensitivity to noise in measured data of damping matrix identification approach, various methods are compared with a simulated lumped model and real test results. An improved damping matrix identification approach is proposed and can generate the unique damping matrix over the full frequency range of interest.
Ph. D.

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46

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.

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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.

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47

Földhazy, Martin. "Variations in dynamic properties of a steel arch footbridge : An experimental study." Thesis, KTH, Bro- och stålbyggnad, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231348.

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This study separately investigates how temperature as well as two real load-situations affects the modal damping ratio and natural frequencies of a 64.9m span steel arch footbridge. Measurements of acceleration have been completed which covers a temperature span of to . The natural frequencies of the five investigated modes were observed to decrease 2-6% as the temperature increased. This effect was with the help of beam-theory and finite element modelling deduced to originate mostly from changes in Young’s modulus of the materials, but also geometrical changes in steel because of thermal expansion. Further investigation included a static mass in the form of packed snow that was estimated to weigh 14 tons. The natural frequencies were observed to remain unchanged while the modal damping ratios decreased. The second load-case was an uncontrolled mass-event where a large group of pedestrians travelled over the bridge as two cars stood stationary at the quarter-point of the span. A large increase (146%) of the damping ratio was observed while the natural frequency of the first mode decreased 4%. This change was suggested come from the human structure interaction (HSI) partially because the natural frequency of the human body is close to the first vertical frequency of the bridge thus making humans act like dampers on the bridge when close to resonance, and that the number of pedestrians contribute to the modal mass of the system, thus decreasing the natural frequency.
Denna studie undersöker separat hur temperaturen såväl som två verkliga belastningssituationer påverkar de modala dämpnings kvoterna och egenfrekvenserna hos en 64,9 meter lång stål-bågs gångbro. Mätningar av accelerationen i bron har genomförts som täcker en temperatur på -10°C till 10°C. De naturliga frekvenserna hos de fem undersökta moderna observerades minska 2–6% när temperaturen ökade. Denna minskning var med hjälp av balk-teori och finita element-modellering härled att troligen komma från förändringar i Youngs modul av materialen, men även geometriska förändringar i stålet på grund av termisk expansion. Vidare undersökning innefattade en statisk massa i form av packad snö som uppskattades att väga 14 ton. Egenfrekvenserna observerades förbli oförändrade medan de modala dämpnings kvoterna minskade. Det andra lastfallet var ett okontrollerat massevenemang där en stor grupp fotgängare gick över bron medan två bilar var stationära en fjärdedel in på brons längd. En stor ökning (146%) av dämpnings kvoten för den första vertikala moden observerades medan egenfrekvensen minskade 4%. Denna förändring föreslogs komma från interaktionen mellan människan och bron, delvis för att människokroppens egenfrekvens ligger nära brons första vertikala frekvens vilket gör att människan agerar som en dämpare när de är nära resonans med bron, och att antalet fotgängare bidrar till den modala massan av systemet vilket sänker frekvensen.

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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.

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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.

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49

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.

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50

Oesterle, Michael Gerhardt. "Use of Incremental Dynamic Analysis to Assess the Performance of Steel Moment-Resisting Frames with Fluid Viscous Dampers." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/31536.

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This thesis presents the results of a study that uses Incremental Dynamic Analysis to assess the seismic performance of steel moment-resisting frames with fluid viscous dampers subjected to earthquake ground motions. The study systematically investigated the effects of linear and nonlinear dampers on the response of steel moment-resisting frames to earthquakes that varied in intensity and type. Both near-field and far-field motions were considered. Two different types of nonlinear dampers were investigated; one had a hardening and the other had a softening force-velocity relationship. The nonlinear dampers were calibrated to the linear dampers so that there was a basis of comparison. Maximum damper displacement is one of the parameters of the calibration, and it was varied to investigate its effect on structural response. Several nonlinear inelastic time history analyses were performed to obtain responses, such as peak base shear, peak interstory drift, or residual displacement index, which were plotted versus earthquake intensity to create individual IDA curves. Sets of related IDA curves provide a useful summary of the structural behavior for a wide range of variables. IDA curves for the tests with different damping types are presented. The results show that for both near-field and far-field ground motions the nonlinear dampers with a hardening force-velocity relationship are best suited to reduce undesirable drifts and residual displacements; however, these reductions come at the cost of high base shear forces.
Master of Science

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Dissertations / Theses on the topic 'Dynamic damping'

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