A presente dissertação descreve o desenvolvimento e análise de um experimento concebido para avaliar a contribuição de materiais de fricção sobre vibrações induzidas na superfície de um disco de freio. O aparato proposto é equipado com um excitador modal (shaker), utilizado para promover e controlar o sinal de excitação que foi aplicado sobre os materiais de fricção avaliados. A resposta dessa excitação na superfície do disco de freio foi mensurada através de acelerômetros. Além da aplicação sobre o experimento proposto, foram avaliados o coeficiente de atrito e a distribuição de asperezas da superfície das oito amostras utilizadas. A característica modal do disco utilizado foi descrita através das suas frequências naturais, amortecimento e formas modais, parâmetros identificados através da aplicação de análise modal experimental. O experimento proposto foi utilizado para identificar as principais características de resposta do disco quando a excitação é realizada através do material de fricção. Essa condição também foi comparada com aquela em que a excitação foi aplicada diretamente no disco A métrica mais adequada para avaliação desse experimento foi identificada como o valor médio da magnitude da Função Resposta em Frequência (FRF), calculado através do estimador H3. O aparato proposto se mostrou capaz de identificar diferenças nas amostras avaliadas quanto à propensão dessas à produção de vibrações na superfície do disco. As amostras foram avaliadas no experimento proposto nas condições sem e com filme tribológico sobre a sua superfície, as quais correspondem ao estado das amostras antes e depois, respectivamente, do processo de caracterização do coeficiente de atrito destas, utilizando o tribômetro do LATRIB/UFRGS. Foi observado que as amostras com filme produziram maior vibração do que as amostras sem filme. Os resultados obtidos demonstraram uma forte correlação entre a propensão das amostras à produção de vibrações e a distribuição de asperezas da superfície das amostras. Esses resultados indicam que materiais de fricção com superfícies planas são capazes de transmitir mais vibração à superfície do disco do que aqueles com superfícies mais rugosas. / The present work describes the development and analysis of an experimental apparatus designed to evaluate the contribution of friction materials in vibrations induced on the surface of a brake disc. The proposed apparatus is equipped with a modal exciter (shaker), which was used to promote and control the excitation signal applied in the evaluated friction material. The response of this excitation in the disc surface was measured with accelerometers. The eight samples evaluated in this study was also characterized in terms of its friction coefficient and the asperity distribution of its surface. The modal characteristic of the disc was described in terms of its natural frequencies, damping and modal shapes, whose parameters were obtained by application of experimental modal analysis. The proposed apparatus was used to identify the main characteristics of the disc response when the excitation is applied throw the friction material. This case was also compared to the condition in which the disc was excited directly by the shaker. The most adequate metric to evaluate this experiment was selected as the mean value of the Frequency Response Function (FRF) spectrum, calculated by the H3 estimator The proposed apparatus showed being capable of identifying differences between the evaluated samples, regarding its propensity to produce vibrations on the disc surface. The samples were evaluated in with and without tribological film deposited on its surface. It was shown that the analyzed samples had the vibration increased with tribological film compared to the condition without the film. The obtained results demonstrated a strong correlation between the samples propensity to the production of vibration and the asperity distribution of the samples surfaces. These results indicate that friction materials with flat surfaces are capable to transmit more vibrations to the disc surface than those samples with rough asperity distribution.

The modern engineering design process includes computer software packages that require approximations to be made when representing geometries. These approximations lead to inherent discrepancies between the design geometry of a part or assembly and the corresponding manufactured geometry. Further approximations are made during the analysis portion of the design process. Manufacturing defects can also occur, which increase the discrepancies between the design and manufactured geometry. These approximations combined with manufacturing defects lead to discrepancies which, for high precision parts, such as jet engine compressor blades, can affect the modal analysis results. In order to account for the manufacturing defects during analysis, mesh morphing is used to morph a structural finite element analysis mesh to match the geometry of compressor blades with simulated manufacturing defects. The mesh morphing process is improved by providing a novel method to convert heteromorphic shape matching within Sculptor to homeomorphic shape matching. This novel method is automated using Java and the NX API. The heteromorphic to homeomorphic conversion method is determined to be valid due to its post-mesh morphing maximum deviations being on the same order as the post-mesh morphing maximum deviations of the ideal homeomorphic case. The usefulness of the automated heteromorphic to homeomorphic conversion method is demonstrated by simulating manufacturing defects on the pressure surface of a compressor blade model, morphing a structural finite element analysis mesh to match the geometry of compressor blades with simulated manufacturing defects, performing a modal analysis, and making observations on the effect of the simulated manufacturing defects on the modal characteristics of the compressor blade.

Methods for comprehensive structural dynamic analysis generally employ input-output modal analysis with a mathematical model of structural vibration using excitation and response data. Recently operational modal analysis methods using only vibration response data have been developed. In this thesis, both input-output and operational modal analysis, in the presence of significant unmeasured excitations, is considered. This situation arises when a test structure cannot be effectively isolated from ambient excitations or where the operating environment imposes dynamically-important boundary conditions. The limitations of existing deterministic frequency-domain methods are assessed. A novel time-domain estimation algorithm, based on the estimation of a discrete-time autoregressive moving average with exogenous excitation (ARMAX) model, is proposed. It includes a stochastic component to explicitly account for unmeasured excitations and measurement noise. A criterion, based on the sign of modal damping, is incorporated to distinguish vibration modes from spurious modes due to unmeasured excitations and measurement noise, and to identify the most complete set of modal parameters from a group of estimated models. Numerical tests demonstrate that the proposed algorithm effectively identifies vibration modes even with significant unmeasured random and periodic excitations. Random noise is superimposed on response measurements in all tests. Simulated systems with low modal damping, closely spaced modes and high modal damping are considered independently. The accuracy of estimated modal parameters is good except for degreesof- freedom with a low response level but this could be overcome by appropriate placement of excitation and response measurement points. These observations are reflected in experimental tests that include unmeasured periodic excitations over 200% the level of measured excitations, unmeasured random excitations at 90% the level of measured excitations, and the superposition of periodic and random unmeasured excitations. Results indicate advantages of the proposed algorithm over a deterministic frequency domain algorithm. Piezoceramic plates are used for structural excitation in one experimental case and the limitations of distributed excitation for broadband analysis are observed and characterised in terms of actuator geometry and modal deformation. The ARMAX algorithm is extended for use with response measurements exclusively. Numerical and experimental tests demonstrate its performance using time series data and correlation functions calculated from response measurements.

This thesis considers the design of a beamformer which can enhance desired signals in an environment consisting of broadband nearfield and/or farfield sources. The thesis contains: a formulation of a set of analysis tools which can provide insight into the intrinsic structure of array processing problems; a methodology for nearfield beamforming; theory and design of a general broadband beamformer; and a consideration of a coherent nearfield broadband adaptive beamforming problem. To a lesser extent, the source localization problem and background noise modeling are also treated. ¶: A set of analysis tools called modal analysis techniques which can be used to a solve wider class of array signal processing problems, is first formulated. The solution to the classical wave equation is studied in detail and exploited in order to develop these techniques. ¶: Three novel methods of designing a beamformer having a desired nearfield broadband beampattern are presented. The first method uses the modal analysis techniques to transform the desired nearfield beampattern to an equivalent farfield beampattern. A farfield beamformer is then designed for a transformed farfield beampattern which, if achieved, gives the desired nearfield pattern exactly. The second method establishes an asymptotic equivalence, up to complex conjugation, of two problems: (i) determining the nearfield performance of a farfield beampattern specification, and (ii) determining the equivalent farfield beampattern corresponding to a nearfield beampattern specification. Using this reciprocity relationship a computationally simple nearfield beamforming procedure is developed. The third method uses the modal analysis techniques to find a linear transformation between the array weights required to have the desired beampattern for farfield and nearfield, respectively. ¶: An efficient parameterization for the general broadband beamforming problem is introduced with a single parameter to focus the beamformer to a desired operating radius and another set of parameters to control the actual broadband beampattern shape. This parameterization is derived using the modal analysis techniques and the concept of the theoretical continuous aperture. ¶: A design of an adaptive beamformer to operate in a signal environment consisting of broadband nearfield sources, where some of interfering signals may be correlated with desired signal is also considered. Application of modal analysis techniques to noise modeling and broadband coherent source localization conclude the thesis.

Integral abutment bridges are jointless bridges in which the deck is continuous and connected monolithically with the abutment walls supported typically by a single row of piles. This thesis focuses on the effects of two major parameters on the seismic behavior of an integral abutment bridge in Tennessee by considering soil-structure interaction around the piles and in back of the abutments: (1) clay stiffness (medium vs. hard) around the piles, and (2) level of sand compaction (loose vs. dense) of the abutment wall backfilling. Modal and nonlinear time history analyses are performed on a three dimensional detailed bridge model using the commercial software SAP2000, which clearly show that (1) compacting the backfilling of the abutment wall will increase the bridge dominant longitudinal natural frequency considerably more than increasing the clay stiffness around the piles; (2) the maximum deflection and bending moment in the piles under seismic loading will happen at the pile-abutment interface; (3) under seismic loading, densely-compacted backfilling of the abutment wall is generally recommended since it will reduce the pile deflection, the abutment displacement, the moments in the steel girder, and particularly the pile moments; (4) under seismic loading, when the piles are located in firmer clay, although the pile deflection, the abutment displacement, and the maximum girder moment at the pier and the mid-span will decrease, the maximum pile moment and the maximum girder moment at the abutment will increase.

Theoretical and experimental modal analysis, i.e., the computation of vibration modes from a mathematical model and from experimental data, respectively, is quite sophisticated and advanced in linear structural dynamics. However, nonlinearity is a frequent occurrence in real-world engineering structures, and the existing linear methodologies fail dramatically in the presence of nonlinear dynamical phenomena. Therefore, the present thesis focuses on the development of a practical nonlinear analog of modal analysis for properly accounting for nonlinearity in mechanical systems. The concept of nonlinear normal mode (NNM) provides solid mathematical and theoretical foundations for a rigorous, yet understandable by the practicing engineer, analysis of nonlinear dynamical behaviors. In this context, a useful framework for nonlinear modal analysis of vibrating structures, which includes the computation of NNMs from finite element models and their identification from experimental data, is proposed in this dissertation. In view of the still limited use of NNMs in structural dynamics, special attention is devoted to progress toward a practical tool that has the potential to deal with large-scale, real-world structures. Targeting an effective and exact computation of NNMs, even in strongly nonlinear regimes of motion, one original contribution of this work is to resort to numerical methods. An algorithm combining a shooting procedure and the so-called pseudo-arclength continuation method is developed. On the other hand, a nonlinear extension of phase resonance testing (also known as force appropriation) is introduced for the experimental identification of NNMs, which is another innovative aspect of the doctoral thesis. In particular, the phase lag quadrature criterion, which is used for linear experimental modal analysis, is generalized in the presence of nonlinear dynamical behavior. Academic examples are first considered to illustrate, in a simple manner, that the proposed methods form an effective and adequate framework for nonlinear modal analysis. Furthermore, more realistic structures, including a full-scale aircraft, are studied to demonstrate the potential applicability of the approach to large-scale, real-life applications.

Complex systems can be divided into simpler substructures. Determining the properties of each subcomponent by experimental procedures is practical and can serve to verify or calibrate finite element models. In this work, an existing model of a wind turbine blade was improved by use of experimental data. Such a blade is a subpart of a complete wind turbine. For calibration purpose, several material tests were made in order to determine the stiffness and mass properties. Later on, vibration tests of the blades were conducted and compared with simulation results of the improved model. Geometry variability within sets of blades was also studied. The blade twist angles and the center of gravity positions were found to vary moderately, which accounts for differences in blades’ dynamic behavior. Correlations between experimental data and analytical model results were very high for the first eight modeshapes. That is, according to the Model Assurance Criterion the calibrated model achieves a high-quality representation of reality. However, torsional modes in the computer model occur at a higher frequency than the experimental ones. Substructuring of the turbine allows the blades to be modeled and validated independently of the other substructures and can later be incorporated into a complete model of the turbine.

Constructing multi floor buildings by light weight material have increased recently. There are many advantages of using light weight material, such as wood, for the environment. However, one of the deficiencies of lightweight material is the acoustic performance. Transmission of sound and vibration through floors in multi floor buildings in wood is a drawback to be considered. There are many studies that have addressed this issue. It is most common to make a finite element models well as experiments in laboratory. In these studies the material properties in the FE model are probably often adjusted to correlate to the laboratory experiments, since there is a large spread in material properties found in literature. This thesis however tries to elaborate on the actual material properties of the included wooden elements. Dynamic testing is done to determine the spread (here spread means gap between material properties) in material properties of wooden elements. The materials tested are chipboards and two types of wooden beams. The examined beams are both normal wooden beams and laminated veneer lumber beams. When the dynamic behaviour is known for the wooden parts, they are assembled to two small floor systems. The floor systems consist of four beams and one wooden board. The assembly is dynamically tested in laboratory and in FE software. The FE model used the known material properties for each individual building part. The results from the FE model correlate well with the laboratory tests. This shows that when material properties are known a FE model can predict the real behaviour. However, the examined material properties show a large spread from beam to beam, etc and a better knowledge about the material properties of used wooden parts is needed. / Att bygga flervåningshus med lätta byggmaterial har blivit allt vanligare. Det finns många fördelar med att använda lätta material, såsom trä. En av fördelarna är att det är skonsamt för miljön. Emellertid är en av bristerna i lättviktsmaterial den akustiska prestandan. Överföring av ljud och vibrationer genom golv i flervåningshus i trä är en nackdel att överväga. Det finns flera studier som har behandlat denna fråga. Ofta görs finita element modeller samt tester i laboratorium. I dessa studier justerar man materialegenskaperna i FE-modellen för att korrelera mot laboratorieexperiment. Detta eftersom det finns en stor spridning i materialegenskaperna för trä i litteraturen. Med detta examensarbete, undersöks de faktiska materialegenskaperna hos träelementen genom försök. Dynamiska tester utförs för att bestämma spridningen i materialegenskaper. De testade materialen är spånskivor och två typer av träbalkar. De undersökta balkarna är både normala träreglar och laminerade faner balkar. När det dynamiska beteendet är känt för trädelarna, monteras de ihop till två små golvsystem. Golvsystemen består av fyra balkar och en träskiva. Den assemblerade modellen testas både dynamiskt i ett praktiskt försök och i ett FE program. I FEmodellen används de tidigare framtagna faktiska materialegenskaper för varje ingående enskild byggnadsdel. Resultaten från FE-modellen korrelerar väl med de praktiska experimenten. Med detta examensarbete visas att när materialegenskaperna är kända kan FE-modellen förutsäga det verkliga beteendet. De undersökta materialegenskaperna visar dock en stor spridning från balk till balk, etc. och mer kunskap om materialegenskaper hos trädelar behövs.

Diffraction Enhanced X-ray Imaging (DEI) uses synchrotron X-ray beams prepared and analyzed by perfect single crystals to achieve imaging contrast from a number of phenomena taking place in an object under investigation. The crystals used in DEI for imaging requires high precision positioning due to a narrow rocking curve. Typically, the angular precision required should be on the order of tens of nanoradians.<p>One of the problems associated with DEI is the inability to control, set, and fix the angle of the analyzer crystal in relation to the beam exiting the monochromator in the system. This angle is used to interpret the images acquired with an object present and the usual approach is to determine where the image was taken after the fact. If the angle is not correct, then the image is wasted and has to be retaken. If time or dose is not an issue, then retaking the image is not a serious problem. However, since the technique is to be developed for live animal or eventually human imaging, the lost images are no longer acceptable from either X-ray exposure or time perspectives.<p>Therefore, a mechanical positioning system for the DEI system should be developed that allows a precise setting and measurement of the analyzer crystal angles. In this thesis, the fundamental principles of the DEI method, the DEI system at the National Synchrotron Light Source (NSLS) and the sensitivity of the DEI system to vibration and temperature has been briefly studied to gain a better understanding of the problem. The DEI design at the NSLS was analyzed using finite element analysis software (ANSYS) to determine the defects in the current design which were making the system dimensionally unstable. Using the results of this analysis, the new analyzer support was designed aiming to eliminate the problems with the current design. The new design is much stiffer with the natural frequency spectrum raised about eight times. <p> This new design will improve the performance of the system at the National Synchrotron Light Source (NSLS) of Brookhaven National Laboratory, New York, USA and should assist in the development of a new DEI system for the Bio-Medical Imaging and Therapy (BMIT) beamline at the Canadian Light Source (CLS), Saskatoon, CANADA.

This thesis describes the development of microfluidic (MF) platforms for the study of biological and chemical processes. In particular the thesis is divided into two distinct parts: (i) development of a MF methodology to generate tunable cell-laden microenvironments for detailed studies of cell behavior, and (ii) the design and fabrication of MF reactors for studies of chemical reactions. First, this thesis presented the generation of biopolymer microenvironments for cell studies. In the first project we demonstrated a high-throughput MF system for generating cell-laden agarose microgels with a controllable ratio of two different types of cells. The MF co-encapsulation system was shown to be a robust method for identifying autocrine and/or paracrine dependence of specific cell subpopulations. In the second project we studied the effect of the mechanical properties on the behavior of acute myeloid leukemia (AML2) cancer cells. Cell-laden macroscopic agarose gels were prepared at varying agarose concentrations. A modest range of the elastic modulus of the agarose gels were achieved, ranging from 0.62 kPa to 20.21 kPa at room temperature. We observed a pronounced decrease in cell proliferation in stiffer gels when compared to the gels with lower elastic moduli. The second part of the thesis focuses on the development of MF platforms for studying chemical reactions. In the third project presented in this thesis, we exploited the temperature dependent solubility of CO2 in order to: (i) study the temperature mediated CO2 transfer between the gas and the various liquid phases on short time scales, and (ii) to generate bubbles with a dense layer of colloid particles (armoured bubbles). The fourth project involved the fabrication of a multi-modal MF device with integrated analytical probes. The MF device comprised a pH, temperature, and ATR-FTIR probes for in-situ analysis of chemical reactions in real-time. Furthermore, the MF reactor featured a temperature controlled feedback system capable of maintaining on-chip temperatures at flow rates up to 50 mL/hr.