In a recent study, an environment-friendly material, corrugated cardboard, was used as a building block for the vibration isolator with a preliminary study. The present thesis was motivated to advance technology for improving the design of such a corrugated cardboard vibration isolator with a focus on the modeling of its stiffness and damping. In particular, this study has performed the following works: (1) improving the FE (finite element) model of the stiffness of the corrugated cardboards by more accurately identifying the material parameters in the cardboard material constitutive equation; (2) analyzing the effect of the error in geometry of the corrugated cardboards in the FE model; (3) developing the Rayleigh damping model of the corrugated cardboards and evaluating its accuracy. Several conclusions were drawn from this study: (1) the parameter identification procedure based on the inverse analysis is feasible for improving the accuracy of the model of the stiffness of the cardboard. (2) The FE model of the cardboards with a greater in-plane geometrical deflection has less vertical compressive stiffness. The geometrical deflections of the corrugated cardboards also change the condition of the contact friction stress and the compressive deformation. (3) Rayleigh damping model is accurate enough for calculating the damping of the corrugated cardboards. The contributions of the thesis include: (1) provision of a more accurate model for the compressive stiffness the corrugated cardboards, (2) finding that the friction between the cardboard and the vibrator and the geometrical error of the cardboards have a significant influence over the accuracy of the FE model, (3) finding that in practice the foregoing influence can significantly degraded the performance of the cardboards as a vibrator isolator, and (4) provision of a model for the compressive damping of the corrugated cardboards.

Submitted by Willian Minnemann Kuhnert null (willian.kuhnert@feb.unesp.br) on 2016-08-29T20:53:53Z No. of bitstreams: 1 VERSAO_FINAL_WILLIANMK.pdf: 7510529 bytes, checksum: d0f36cb6fb5aeb748d7d26333a6c853c (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-08-31T12:32:11Z (GMT) No. of bitstreams: 1 kuhnert_wm_me_bauru.pdf: 7510529 bytes, checksum: d0f36cb6fb5aeb748d7d26333a6c853c (MD5) / Made available in DSpace on 2016-08-31T12:32:11Z (GMT). No. of bitstreams: 1 kuhnert_wm_me_bauru.pdf: 7510529 bytes, checksum: d0f36cb6fb5aeb748d7d26333a6c853c (MD5) Previous issue date: 2016-07-19 / Fundação para o Desenvolvimento da UNESP (FUNDUNESP) / O isolamento de vibração é a técnica mais utilizada atualmente para a proteção de mecanismos e estruturas que sofrem excitação, seja ela por choque/impacto, seja ela harmônica. Este trabalho adiciona ao isolador de vibração comum, composto por molas e amortecedores, um elemento conhecido como inerter, que recentemente tem chamado bastante a atenção da comunidade científica, e também, separadamente, adiciona amortecedores não lineares, com o intuito de avaliar a influência destes elementos no isolamento. As curvas de transmissibilidade obtidas, que indicam a performance do isolamento à excitação harmônica, para os isoladores com inerter são comparadas à de um isolador comum composto somente por uma mola, e entre elas, enquanto que as curvas obtidas para os isoladores com amortecedores não lineares são comparadas entre si e à de um isolador comum com amortecimento linear. Os resultados obtidos mostram que a adição do inerter aos isoladores de vibração pode ser muito benéfica para o isolamento em determinadas faixas de frequência, mas em outras não, e tais faixas dependem de como o isolador é construído. Além disso, os isoladores com inerter são benéficos principalmente para sistemas subamortecidos. Os isoladores subamortecidos com inerter apresentaram características de isolamento diferentes uns dos outros, o que os leva a serem aplicados em diferentes situações. Os resultados obtidos para os isoladores com amortecedores não lineares mostraram que tais sistemas também podem melhorar ou piorar o isolamento em determinadas faixas de frequência quando comparados à um isolador com amortecimento linear. / The vibration isolation is currently the most used technique for protecting mechanisms and structures which are under shock/impact or harmonic excitation. This work presents to the common vibration isolator, consisted by springs and dampers, an element known as inerter, which recently has took great attention in the scientific community, and also presents the use of non-linear dampers to analyze the influence of these elements on isolation. The transmissibility curves obtained, which indicate the performance of the isolation for systems under harmonic excitation, for the isolators with the inerter element are compared with the spring-damper isolator frequency response as well the isolators with non-linear damping. The results obtained show that the addition of the inerter element can be beneficial for the isolation performance in a frequency range, but degrades the high frequency isolation, and they depend on how the isolator is built. Besides, the isolators with inerter are beneficial mainly for underdamped systems. The different underdamped systems with inerter presented unique isolation characteristics. The results obtained for the isolators with non-linear dampers presented that such systems can also improve the isolation in certain frequency ranges when compared to an isolator with linear damping. / FUNDUNESP: 110/2013-CCp/PIB

Ground-borne vibration has existed ever since the development of urban road and rail networks. Vibration generated by the moving traffic propagates through the ground and into buildings, resulting in unacceptable levels of internal noise and vibration. A common solution to this increasingly significant problem is the base-isolation of buildings by incorporating vibration isolation bearings between the buildings and their foundations. This technique has been employed for over forty years but the exact performance of base isolation remains uncertain. This dissertation is concerned with the development of a generic computational model; generic in that it accounts for the essential dynamic behaviour of a typical base-isolated building in order to make predictions of isolation performance. The model is a linear one, formulated in the frequency domain, and consists of a two-dimensional portal-frame model of a building coupled to a three-dimensional boundary-element model of a piled-foundation. Both components of the model achieve computational efficiency by assuming they are infinitely long and using periodic structure theory. The development of the model is described systematically, from the modelling of a building and its isolation bearings to that of its foundation. The majority of the work is concerned with the piled-foundation model, which is comprehensive in that it accounts for the vertical, horizontal and rotational motion of the pile heads due to both direct pile-head loading and interaction through wave propagation in the surrounding soil. It is shown that this level of detail is important in the prediction of base isolation efficiency. A key question facing designers is not only how but on what basis base isolation should be assessed, since fundamental problems exist with the existing measures of isolation performance. Power flow analysis is explored and the concept of power flow insertion gain, based on the total mean vibrational power flow entering a building, is introduced as a useful measure of isolation performance. This is shown to offer clear benefits by providing a single measure of performance that is suitable for design purposes. Finally, the development of a prototype force-sensitive vibration isolation bearing is described as a contribution to verifying base-isolation theory with experiments.

No description available.

Vibrations resulting from earthquakes, machinery, or unanticipated shocks may be very damaging and costly to structures. To avoid such damage, designers need a structural system that can dissipate the energy caused by these vibrations. Using elastically buckled struts may be a viable means to reduce the harmful effects of unexpected vibrations. Post-buckled struts can support high axial loads and also act as springs in a passive vibration isolation system by absorbing or dissipating the energy caused by external excitation. When a base excitation is applied, the buckled strut may act to reduce the dynamic force transmitted to the system, thus reducing the structural damage to the system. Several models of buckled and pre-bent struts are examined with different combinations of parameters and end conditions. The models include pinned or fixed columns supporting loads above their buckling load, and columns with an initial curvature supporting various loads. The varying parameters include external damping, internal damping, and stiffness. The columns will be subjected to simple harmonic motion applied at the base or to a multi-frequency base excitation. The response of each model is measured by the deflection transmissibility of the supported load over a large range of frequencies. Effective models reduce the motion of the supported load over a large range of frequencies. / Master of Science

Sensitive devices are affected by extreme vibration excitations during operation so require isolation from high levels of vibration excitations. When these excitation characteristics of the devices are well known, the vibration isolation can be achieved accurately. However, it is possible to have expected profile information of the excitations with respect to frequency. Therefore, it is practical and useful to implement this information in the design process for vibration isolation. In this thesis, passive vibration isolation technique is examined and a computer code is developed which would assist the isolator selection process. Several sample cases in six degree of freedom are designed for a sample excitation and for sample assumptions defined for an inertial measurement unit. Different optimization methods for design optimizations are initially compared and then different designs are arranged according to the optimization results using isolators from catalogues for these sample cases. In the next step, the probable designs are compared according to their isolator characteristics. Finally, one of these designs are selected for each case, taking into account both the probable location deviations and property deviations of isolators.

In this work, we investigate the active vibration isolation and damping of sensitive equipment. Several single-axis isolation techniques are analyzed and tested. A comparison between the sky-hook damper, integral force feedback, inertial velocity feedback and LagLead control techniques is conducted using several practical examples. The study of single-axis systems has been developed and used to build a six-axis isolator. A six degrees of freedom active isolator based on Stewart platform has been designed manufactured and tested for the purpose of active vibration isolation of sensitive payloads in space applications. This six-axis hexapod is designed according to the cubic configuration; it consists of two triangular parallel plates connected to each other by six active legs orthogonal to each other; each leg consists of a voice coil actuator, a force sensor and two flexible joints. Two different control techniques have been tested to control this isolator : integral force feedback and Lag-Lead compensator, the two techniques are based on force feedback and are applied in a decentralized manner. A micro-gravity parabolic flight test has been clone to test the isolator in micro-gravity environment. ln the context of this research, another hexapod has been produced ; a generic active damping and precision painting interface based on Stewart platform. This hexapod consists of two parallel plates connected to each other by six active legs configured according to the cubic architecture. Each leg consists of an amplified piezoelectric actuator, a force sensor and two flexible joints. This Stewart platform is addressed to space applications where it aims at controlling the vibrations of space structures while connecting them rigidly. The control technique used here is the decentralized integral force feedback.

Vibration isolation is a common approach to reduce the undesired vibration of a dynamic system from its surrounding. The common material used for the vibration isolator is rubber (for example) which is known to be environmentally unfriendly. This thesis presents a study on the use of corrugated cardboard for the vibration isolator, which is known to be a highly environment-friendly material. The focus of the study is on understanding and modeling of stiffness and damping of cardboard when it or its system (several cardboards) is used for isolating the vibration coming from the vertical direction of cardboard. In this thesis, a study is presented of finite element modeling of stiffness of corrugated cardboard in its vertical direction with the aim of overcoming two major shortcomings in modeling in the current literature: (1) the width effect is neglected even for cardboard with its width greater than length and (2) the non-linear constitutive relation is not accurately determined. Indeed, it is likely that these shortcomings are responsible for inaccuracy with the models in the current literature to predict the stiffness and peak load. Further, a test bed was set up for the measurement of damping of cardboards in this study. This thesis also presents an application of the theoretic development in the stiffness and damping of corrugated cardboard to design an isolator for the vacuum pump at Canadian Light Source. Several conclusions are drawn from this study: (1) modeling with consideration of the width effect and non-linear constitutive relation is necessary to improve the accuracy of prediction of stiffness of cardboard; (2) set up for the measurement of damping of cardboard is accurate; and (3) cardboard systems are feasible for vibration isolation in terms of the reduction of amplitude of vibration. The contribution of this thesis includes: (1) providing a finite element method for modeling of corrugated cardboards which have a complex non-linear constitutive relation, variable contact configuration, and 3D geometrical effect and (2) providing the feasibility of proving that corrugated cardboard can be used for vibration isolation.

In future human spaceflight missions, with prolonged exposure to microgravity, resistive and aerobic exercises will be countermeasures for bone loss, muscle loss, and decreased aerobic capacity. Two of the exercises of interest are squats and rowing. The cyclic forces produced during these exercises are at relatively low frequencies which are likely to excite structural resonances of space vehicles. Vibration Isolation Systems (VIS) are being designed to be paired with future exploration exercise devices in order to prevent these cyclic exercise forces from impacting the space vehicle. The VIS may be configured such that a platform supports the human and exercise device. There is limited knowledge about the interaction between a human exercising and a dynamic platform. This research sought to fill part of the knowledge gap and study how the force inputs to the platform change as well as how exercise form was affected. For this research, a system which can produce dynamic responses similar to those of a prospective VIS platform was used. This system is the Computer Assisted Rehabilitation Environment (CAREN) (Motekforce Link, Amsterdam, Netherlands). Simplified sinusoidal responses were implemented in a single degree of freedom, vertical (heave) motion, and also in multi-degree of freedom, heave and pitch motion. Human subject testing was conducted using four subjects with exercise experience. The subjects completed squats and rows, while standing, in both static (platform not moving) and dynamic (with platform moving) conditions. Subjects aimed to synchronize with platform motion, at the appropriate phase. Kinetic and kinematic data were collected via force plate measurements and motion capture, respectively. Testing was completed with several predetermined frequencies for platform motion, but also at each subject’s baseline frequency, which was the measured, comfortable exercise rate for the subject. Data were processed and arranged in a presentable format. Results showed attenuation of the vertical component of forces between the comparable frequency static and dynamic platform conditions, as expected, for most subjects in the squat exercise. This was seen only in the heave with pitch condition during rows for most subjects. Results also showed increasing amplitude of forces as frequency increased, which was also expected. Knee angle range of motion was well maintained between static and dynamic conditions. These results suggest that conditions desirable for both VIS and exercise are possible. Further testing and extended analysis at additional amplitudes, frequencies, and degrees of freedom are of interest and warrant further study. This work contributed knowledge and data regarding the forces involved and human kinematics produced while exercising with platform motion. These data can further be used as inputs and requirements for VIS design work, VIS and human biomechanical modeling, and exercise countermeasure development. This work achieved the objectives of establishing an appropriate test environment and developing platform dynamics in which human-VIS interaction could be studied. It also acted as a proof-of-concept for future testing which can be conducted to answer new questions relating to dynamic platform motion effects on human activity.

Cette thèse s'inscrit dans le cadre de l'étude de la stabilisation de modules d'un futur collisionneur linéaire, CLIC (Compact Linear Collider). Afin d'assurer le fonctionnement et la collision des particules dans ce futur grand instrument de physique, il faut garantir l'alignement de modules guidant des faisceaux de dimensions nanométriques. Les travaux développés ont pour support expérimental deux dispositifs : un dispositif de micropositionnement, avec une résolution inférieur au 1µm, où les perturbations peuvent être simulées et un prototype de nanostabilisation active pour charges importantes (>50kg @300Hz), avec une résolution validée expérimentalement inférieur à 0,15 nm, permettant de démontrer la faisabilité du contrôle de la stabilisation subnanométrique en s'intéressant particulièrement au rejet des mouvements du sol. Les problématiques traitées lors de ces travaux portent sur la méthodologie de conception de tels systèmes, ce qui inclue la conception électromécanique et l'instrumentation, ; la mise en œuvre et la modélisation du comportement des prototypes ,; le contrôle avec notamment les aspects de non linéarité des actionneurs. Les performances obtenues de ces différents travaux et validées expérimentalement incluent notamment les points suivants: La bande passante de fonctionnement pour du micro-positionnement à l'aide d'actionneurs piézoélectriques a été augmentée grâce à la compensation d'hystérésis : Rejet de perturbation issue du support jusqu'à 100 Hz et positionnement jusqu'à 190 Hz. Il a été démontré la faisabilité du contrôle à l'aide de capteurs sismiques. L'isolation active réalisée présente une atténuation des nano-mouvement du sol dans une bande passante comprise entre 12 et 100Hz. Expérimentalement, cela conduit à une réduction des mouvements du sol de 0,6nm [rms] à 0,25nm [rms] à 50Hz et de 3,7nm [rms] à 0,9nm [rms] à 20Hz. / This thesis takes place in the framework of a general study about the stabilization of the mechanical modules of a future linear collider, CLIC (Compact Linear Collider). In order to guarantee the good operation and the particle collision, the nanometer sized beams need to be stabilized. The proposed approach was developed on two mock-ups: one dedicated to micropositioning with disturbances generation capabilities, and an active isolation system operating heavy load (up to 50kg at 300Hz) at the nanometer scale with an experimentally validated resolution of 0.15 nm. This work studies the electromechanical design and the instrumentation, the implementation of the two set-ups and their modeling,; the control scheme that takes into account the nonlinearities of the actuators. The experimental achievements include the increase of the bandwidth for piezoelectric micro-positioning thanks to an inverse hysteresis operator: the perturbation rejection is efficient until 100 Hz and the tracking control until 190 Hz. A control scheme using seismic sensors is developed to attenuate ground motion and to isolate a platform in a 12 Hz to 100 Hz frequency range. The experimental displacement is reduced from 0.6 nm to 0.25 nm at 50 Hz and from 3.7 to 0.9 at 20 Hz.