Este trabalho apresenta a medição e avaliação dos níveis de ruído e vibração que a tripulação de um navio, que transporta cargas perigosas na bacia do sul, está submetida e propor soluções para diminuir essa exposição. Levando em conta que a tripulação está exposta durante toda a viagem do navio a redução dos níveis de ruído e vibração é de suma importância para melhorar o conforto e a prevenção de moléstias e ou doenças decorrentes dessa exposição. Foram realizadas medições do nível de pressão sonora e aceleração nas três direções em camarotes e na praça de máquinas do navio em estudo. Foram comparadas com normas que regem os níveis de ruído e vibração adequados para embarcações marítimas. Através da análise do espectro de frequência e do espectro cruzado das medições realizadas foram definidos caminhos de propagação das ondas sonoras e vibratórias e identificadas as frequências que são transmitidas por eles. De posse desses dados são apresentadas propostas de soluções para a diminuição dos níveis de pressão sonora e vibração no navio. / This work presents the measurement and assessment a ships crew exposition to noise and vibration. The ship hauls hazardous cargo in the brazilian southern basin. Considering that the crew is exposed throughout the ship's journey reducing the levels of noise and vibration is critical for improved comfort and prevention of exposure aggravated diseases. Sound pressure levels and three dimensional acceleration measurements were performed on the studied vessel's cabins and engine room. The levels of noise and vibration were compared with standards suitable for marine vessels. Propagation paths of sound waves and vibration were defined by analyzing the frequency spectrum and cross spectrum of the measurements as well as their transmitted frequencies. Proposals for based on the data gathered of sound pressure level and vibration reduction are presented.

Este trabalho apresenta a medição e avaliação dos níveis de ruído e vibração que a tripulação de um navio, que transporta cargas perigosas na bacia do sul, está submetida e propor soluções para diminuir essa exposição. Levando em conta que a tripulação está exposta durante toda a viagem do navio a redução dos níveis de ruído e vibração é de suma importância para melhorar o conforto e a prevenção de moléstias e ou doenças decorrentes dessa exposição. Foram realizadas medições do nível de pressão sonora e aceleração nas três direções em camarotes e na praça de máquinas do navio em estudo. Foram comparadas com normas que regem os níveis de ruído e vibração adequados para embarcações marítimas. Através da análise do espectro de frequência e do espectro cruzado das medições realizadas foram definidos caminhos de propagação das ondas sonoras e vibratórias e identificadas as frequências que são transmitidas por eles. De posse desses dados são apresentadas propostas de soluções para a diminuição dos níveis de pressão sonora e vibração no navio. / This work presents the measurement and assessment a ships crew exposition to noise and vibration. The ship hauls hazardous cargo in the brazilian southern basin. Considering that the crew is exposed throughout the ship's journey reducing the levels of noise and vibration is critical for improved comfort and prevention of exposure aggravated diseases. Sound pressure levels and three dimensional acceleration measurements were performed on the studied vessel's cabins and engine room. The levels of noise and vibration were compared with standards suitable for marine vessels. Propagation paths of sound waves and vibration were defined by analyzing the frequency spectrum and cross spectrum of the measurements as well as their transmitted frequencies. Proposals for based on the data gathered of sound pressure level and vibration reduction are presented.

The prototypes vibration test carried out for obtaining reliable information concerning machine’s dynamic properties in development process. Analysis results should be able to correlate with FE model to determine if some underlying assumptions (material properties & boundary conditions) were correct. EMA used for extracting structure modal parameter under laboratory condition. However, EMA can generally not provide all required information concerning machine dynamic property. To simulate vibration in operating, it commonly requires the model based on dynamic properties of the machine under operating. Thus, vibration tests need carried out under operational condition. OMA is a useful tool for extracting information concerning dynamic properties of operating machine. This report concerns vibration test of part of mining machine under operating condition. Modal parameters extracted by two kinds of OMA methods. Results from OMA was compared with corresponding EMA results, illustrates reader the advantages of OMA.

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Electric propulsion motors have emerged as a promising solution to address greenhouse gas emissions from Internal Combustion Engines (ICEs). While electric propulsion motors offer numerous advantages over Internal Combustion Engines (ICEs), they also pose certain challenges. Electric motors are prone to high-frequency tonal noise, which can be annoying to customers and become a quality concern in noise-sensitive automotive applications. The ongoing effort to increase the speed of electric propulsion motors for enhanced power density can have an adverse impact on rotors. This is due to the fact that the stress induced in the rotor is quadratically proportional to its speed. This concern becomes particularly significant for motors that rely on air barriers and thin bridges to enhance their electromagnetic performance. The thesis makes a contribution to address these challenges. First, the acoustic noise mitigation methods at the transmission stage are investigated. Then, acoustical materials are experimentally validated for their capacity to mitigate acoustic noise at the transmission stage. Then, experimental modal analysis is conducted to find out the modal characteristics of a stator-housing assembly. The mode shapes and modal frequency are compared with finite element results to evaluate the fidelity of the finite element model. Then, an equivalent damage approach is used to employ accelerated fatigue analysis for a rotor using constant amplitude load cycles. Finally, a thermomechanical fatigue analysis workflow is developed for a rotor to overcome the limitations of the constant amplitude load cycle approach, with an additional computational cost. / Thesis / Doctor of Philosophy (PhD)

This thesis presents fundamental research in the field of laser vibrometry for the application to vibration measurements. A key concern for laser vibrometry is the effect of laser speckle which appears when a coherent laser beam scatters from an optically rough surface. The laser vibrometer is sensitive to changes in laser speckle which result from surface motions not in the direction of the incident beam. This adds speckle noise to the vibrometer output which can be indistinguishable from the genuine surface vibrations. This has been termed ‘pseudo-vibration' and requires careful data interpretation by the vibration engineer. This research has discovered that measurements from smooth surfaces, even when no identifiable speckle pattern is generated, can produce noise and therefore reference to speckle noise, in such circumstances, is inappropriate. This thesis has, therefore, adopted the more general term of pseudo-vibration to include noise generated from any surface roughness or treatment, i.e. including but not limited to speckle noise. This thesis develops and implements novel experimental methods to quantify pseudovibration sensitivities (transverse, tilt and rotation sensitivity) with attention focussed on commercially available laser vibrometers and consideration is given to a range of surface roughnesses and treatments. It investigates, experimentally, the fundamental behaviour of speckles and attempts to formulate, for the first time, a relationship between changes in intensity to pseudo-vibration sensitivity levels. The thesis also develops and implements models for computational simulation of pseudo-vibrations using the fundamental behaviour of speckles. The combination of experimentation and simulation improves current understanding of the pseudo-vibration mechanisms and provides the vibration engineer with a valuable resource to improve data interpretation. Two experimental methods of quantifying pseudo-vibration sensitivity are developed and successfully applied in the evaluation of transverse, tilt and rotation sensitivity for two models of commercial laser vibrometer. These evaluations cover both single beam (translational vibration measurement) and parallel beam (for angular vibration measurement) modes. The first method presented requires correction of the vibrometer measurement with an independent measurement of genuine velocity to produce an iii apparent velocity dominated by the required noise components. The second method requires a differential measurement using two vibrometers to cancel common components such as genuine velocity, leaving only uncorrelated noise from each measurement in the resulting apparent velocity. In each case, a third measurement is required of the surface motion component causing pseudo-vibration and this is used to normalise the apparent velocity. Pseudo-vibration sensitivity is then presented as a map showing the spectral shape of the noise, as a mean and standard deviation of harmonic peaks in the map and as a total rms level across a defined bandwidth. The simulations employ a novel and effective approach to modelling speckle evolution. Transverse and tilt sensitivity are predicted for the first time and are verified by the experimental study. They provide the vibration engineer with the potential to estimate pseudo-vibrations using a simple piece of software. The laser beam spot diameter has a large influence on the pseudo-vibration sensitivity. Transverse sensitivity has been quantified as around 0.03% and 0.01% (per order) of the transverse velocity of the surface for beam spot diameters of 100 μm and 600 μm respectively. Larger beam spots have been shown to significantly reduce transverse sensitivity and measurements from smoother surfaces have also shown a reduced level of transverse sensitivity. Tilt sensitivity has been quantified at about 0.1 μms-1/degs-1 and 0.3 μms-1/degs-1 (per order) of angular velocity of the surface for beam spot diameters of 100 μm and 600 μm respectively. Smaller beam spot diameters significantly reduce tilt sensitivity. The surface roughness or treatment has been shown to have little effect on the level of tilt sensitivity. Rotation sensitivity has been quantified at approximately 0.6 μms- 1/rads-1 and 1.9μms-1/rads-1 (per order) of rotation velocity of the rotor for 90 μm and 520 μm. Smaller beam spot diameters have shown a significant reduction in rotation sensitivity and measurements on smoother surfaces have shown a reduced rotation sensitivity. Focussing the laser beam approximately on the rotation axis has also shown a significant reduction in rotation sensitivity. Parallel beam rotation sensitivity has been quantified at 0.016 degs-1/rads-1 and it is demonstrated that this can adequately be estimated using the single beam rotation sensitivity.

This thesis presents the practical and novel work in the area of optimal placement of actuators and sensors for sound-structure interaction systems. The work has been done by the author during his PhD candidature. The research is concentrated in systems with non-ideal boundary conditions as in the case in practical engineering applications. An experimental acoustic cavity with five walls of timber and a thin aluminium sheet fixed tightly on the cavity mouth is chosen in this thesis as a good representation of general sound-structure interaction systems. The sheet is intentionally so fixed that it does not satisfy ideal boundary conditions. The existing methods for obtaining optimal sensor-actuator location using analytic models with ideal boundary conditions are of limited use for such problem with non-ideal boundary conditions. The method presented in this thesis for optimal placement of actuators and sensors is motivated by energy based approach and model uncertainty inclusion. The optimal placement of actuator and sensor for the experimental acoustic cavity is used to construct a robust feedback controller based on minimax LQG control design method. The controller is aimed to reduce acoustic potential energy in the cavity. This energy is due to the structure-borne sound inside the sound-structure interaction system. Practical aspects of the method for optimal placement of actuator and sensors are highlighted by experimental vibration and acoustic noise attenuation for arbitrary disturbance using feedback controllers with optimal placement of actuator and sensor. The disturbance is experimentally set to enter the system via a spatial location different from the controller input as would be in any practical applications of standard feedback disturbance rejections. Experimental demonstration of the novel methods presented in this thesis attenuate structural vibration up to 13 dB and acoustic noise up to 5 dB for broadband frequency range of interest. This attenuation is achieved without the explicit knowledge of the model of the disturbance.