La bauxite est un minerai utilisé pour l’élaboration de l’aluminium ou en tant que matière première pour les ciments techniques. Elle est employée, sous sa forme naturelle, en blocs. Ces blocs se font de nos jours de plus en plus rares et leur manutention peut entraîner des pertes sous formes de poussières non valorisées. L’objectif de ce projet est de recycler ces fines particules minérales sous forme de compactés afin d’améliorer l’usage des ressources naturelles minérales qui se raréfient. Ces compactés sont obtenus par compression directe puis avec un procédé innovant couplant vibration et compression. La poudre de bauxite est mélangée à du ciment et de l’eau, puis subit une phase de compaction. Ces compactés doivent avoir des propriétés spécifiques en termes de masse volumique, porosité et résistance mécanique. La micro-tomographie à rayons X est utilisée pour décrire le réarrangement granulaire et l’homogénéité 3D des porosités. La distribution poreuse est caractérisée par analyse d’image et comparée avec les résultats de porosimétrie mercure. Cette étude concernant l’évolution des paramètres texturaux des compactés amène une compréhension des phénomènes liés à la phase de compression. Le stockage et la maturation de ces compactés sous température et humidité contrôlées ont également été étudiés. L’optimisation des paramètres de compression et de formulation, comme la quantité d’eau ou de ciment dans le mélange et la pression de compression, a mené à l’amélioration des propriétés des compactés. Dans un second temps, la phase de compression et les propriétés des compactés ont été améliorées en utilisant une phase préliminaire de vibrations. Cette phase a été optimisée grâce à l’étude de plusieurs paramètres spécifiques comme le type, l’amplitude et la fréquence des vibrations. / The bauxite is used in aluminium elaboration or directly as a raw material for calcium aluminates in technical cements. It is used, as a raw material, as blocks. Recently bauxite blocks are rarer and rarer and their handling can lead to dust wastes that are not re-used. The objective of this project is to recycle the fine mineral particles in compacts to improve the use of natural mineral resources that are running out. These products are compacted by direct compaction and also with an innovative vibration and compaction process. The bauxite is mixed with cement and water, and then the mixture is compacted. They must have specific properties with higher density and mechanical resistance. X-Rays micro-tomography is used to describe the particle rearrangement and the 3D density homogeneity. The porous distribution is then characterized by image analysis and compared with the mercury intrusion porosimetry results. This study on textural parameters evolution of the compacts leads to improve an understanding about the phenomenon during the compaction stage. The storage with controlled temperature and humidity will also be studied. The optimization of the compression and mixture parameters, as amount of water or cement in the mixture and compression pressure, led us to get compacts with improved properties. In the final study, we improved the compression stage and the compacts properties by another stage using in-situ vibrations. The vibrations stage has been optimized studying several vibrational parameters especially the type, the duration, the amplitude and the frequency of the vibrations.

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.

This thesis deals with the measurement and evaluation of vibration on selected parts of car. Part of the work is devoted to the theory of vibration and noise, which includes, among others, presentations of common disorders of machine parts in terms of vibration. In the practical part of the work were performed out measurements described here and the results analyzed. Last part is in short devoted to the possibilities of using a similar measurement in forensic engineering.

Introduction: Very few studies have looked at the effect of vibration on flexibility, and no studies exist that have looked at stretching concurrently with whole body vibration (WBV) training. Therefore, the purpose of this study was to determine if whole-body-vibration training (WBV) done concurrently with static stretch (SV) is more effective than static stretching alone (SS), and to see if WBV training independently (SQ) improves hamstring flexibility without stretching. A secondary purpose of this study is to determine if retention of flexibility gains are maintained. Methods: Forty-four subjects (31 men, 13 women) completed this study (age 22.5 ± 1.8 years; body mass 75.54 ± 13.18 kg; height 176.7 ± 8.06 kg). All subjects were randomly assigned to 1 of 5 groups: SV group (8 males, 3 females), SQ group (8 m, 4 f), SS group (8 m, 3 f), and the C group (7 m, 3 f). All subjects were measured bilaterally for hamstring flexibility using the lying passive knee extension test (LPKE) prior to group assignment. Subjects from each treatment group reported to lab 5 times per week for treatment. Subjects stood on the WBV platform for 5 repetitions of 30-seconds at with 30-seconds in between bouts. The SV group stretched hamstrings while standing on the WBV during the vibration bouts (at 26 Hz and 4 mm amplitude). The SS group did the same thing except the unit was not turned on. The SQ group stood on the WBV platform in a semi-squat position similar to most WBV training studies, without stretching, but with vibration. The C group stood on the WBV platform in a semi-squat without vibration. Analysis and Results: A mixed models analysis of covariance (ANCOVA) was used while blocking on subjects to analyze data using the statistical program SAS (version 9.1). A Bonferroni correction was used for significance on all post hoc tests (p<.0001). At baseline there were no significant differences between groups for flexibility (see Table 1), showing that each group was similar in flexibility to start. Throughout the treatment period (3 weeks of stretching) both the SS and SV groups had significant increases in flexibility compared to SQ and C. Analysis of the slopes (rate of change) for the treatment period was significantly different between the SV group and all other groups (p<.0001 for all comparisons), showing that the SV group had a greater rate of change than all other groups. For the retention period there was no significant difference between the SV and SS group (p=0.0455), but there was a significant difference between both the SV and SS groups and all other groups (p<.0001 for all comparisons). Conclusion: Stretching during WBV improves flexibility more than static stretching alone and at a faster rate. WBV on its own without stretching does not significantly improve hamstring flexibility.

This dissertation is concerned with the responses of nonlinear systems to both deterministic and stochastic excitations. For a single-degree-of-freedom system, the response of a simply-supported buckled beam to parametric excitations is investigated. Two types of excitations are examined: deterministic and random. For the nonlinear response to a harmonic axial load, the method of multiple scales is used to determine to second order the amplitude-and phase-modulation equations. Floquet theory is used to analyze the stability of periodic responses. The perturbation results are verified by integrating the governing equation using both digital and analog computers. For small excitation amplitudes, the analytical results are in good agreement with the numerical solutions. The large-amplitude responses are investigated by using simulations on a digital computer and are compared with results obtained using an analog computer. For the stochastic response to a wide-band random excitation, the Gaussian and non-Gaussian closure schemes are used to determine the response statistics. The results are compared with those obtained from real-time analysis (analog-computer simulation). The normality assumption is examined. A comparison between the responses to deterministic and random excitations is presented. / Ph. D.

<p> The present investigation deals with Gas Turbine Blade Vibrations. Literature on the techniques employed for experimental investigation of gas turbine blade vibration characteristics has been summarised. Various steps have been explained by reviewing the different techniques. Several causes for possible excitation of blades as well as damping methods to suppress the resulting vibrations are also included. Attempts were made to determine experimentally the natural frequencies of cantilever plates of thin uniform rectangular cross section, with and without pretwist. First natural frequency_ -of the plate without twist was in good agreement with the one calculated from the plate formula. Free vibration analysis of cantilever plates of thin uniform rectangular cross section is made. Finite Element Technique is used to determine the elastic and inertial properties of a fully compatible triangular element. Computed values of natural freqencies and mode shapes are compared with other analytical results. </p> / Thesis / Master of Engineering (ME)

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<p dir="ltr">This thesis explores a low-cost method for accurately localizing ball impacts on tennis rackets using consumer-grade sensors. A combined approach leveraging the Newton/Euler method for X-axis estimation and vibration-based analysis for Y-axis estimation is proposed. The Newton/Euler method demonstrated an X-axis error of 17.51%, while the vibration method yielded a Y-axis error of 18%. When integrated, these methods achieved an XY localization error of just 11.44%, significantly outperforming current low-cost alternatives. The system is highly adaptable, requiring only basic racket parameters and a calibration phase to account for individual racket properties. While the study utilized low-velocity impacts, the results suggest that stronger signals in real-world conditions would improve accuracy. Despite challenges such as sensor noise and the influence of hand reaction forces, this work lays the groundwork for a practical, real-time impact localization system with potential applications in player performance enhancement and racket design.</p>

Exposure to severe levels of hand-arm vibration can lead to hand-arm vibration syndrome. Towards curbing the development of hand-arm vibration syndrome, studies have shown that anti-vibration gloves effectively reduce the transmission of unwanted vibration from vibrating equipment to the human hand. However, most of these studies have focused on the study of anti-vibration gloves for power tools such as chipping hammers, and not much work has been done to design anti-vibration gloves for steering wheels. Also, as most of these studies are based on experimental or modeling techniques, the level of effectiveness and optimum glove properties for better performance remains unclear. To fill this gap, the dynamics of the hand-arm system, with and without gloves, coupled to a steering wheel is studied analytically in this work. A lumped parameter model of the hand-arm system with hand-tool interaction is modeled as a linear spring-damper system. The model is validated by comparing transmissibility obtained numerically to transmissibility obtained from experiments. The resulting governing equations of motion are solved analytically using the method of undetermined coefficients. Parametric analysis is performed on the biomechanical model of the hand-arm system with and without a glove to identify key design parameters. It is observed that the effect of glove parameters on its performance varies based on the frequency range. This observation further motivates us to optimize the glove parameters, using multi-objective optimization, to minimize the overall transmissibility in different frequency ranges. / Master of Science / When the human hand is exposed for a long time to vibrations generated from hand-held tools, such as Jack-hammers, rock breakers and chipping hammers, humans are in danger of developing hand-arm vibration syndrome. Hand-arm vibration syndrome is dangerous as severe episodes of this syndrome could lead to gangrene and eventually amputation of the fingers. To prevent the occurrence of hand-arm vibration syndrome, some researchers have explored the effectiveness of anti-vibration gloves through experiments. However, no work has been performed to identify the optimal glove design that best optimizes an anti-vibration glove for steering wheel applications. To address this issue, this thesis studied a mathematical model of the human-hand, wearing an anti-vibration glove attached to a steering wheel system. To ensure this model could successfully replicate real life applications, measurements computed with the model were compared with measurements on the human-hand obtained from experiments. After successfully ensuring that the model closely replicated real-life measurements, the model was used to design an Anti-vibration glove with optimal values to protect the hand from hand-arm vibration syndrome.