A caracterização da topografia de superfícies de engenharia é muito importante em aplicações envolvendo atrito, lubrificação e desgaste. Esta prática teve inicio na década de 30 e até os dias atuais vários esforços são desprendidos no sentido de desenvolver novos métodos para avaliação de superfícies. Embora a grande maioria das superfícies seja especificada por parâmetros 2D tais como Ra (rugosidade média) muitas vezes eles não são suficientes para controlar e caracterizar uma superfície. Novos parâmetros foram desenvolvidos onde engenheiros e processistas de manufatura não são somente capazes de ver as superfícies com muito mais detalhes, mas também são capazes de desenvolver e testar superfícies visando a sua funcionabilidade, ou seja, serem produzidas, controladas e testadas de acordo com a função que irão desempenhar na aplicação. O presente trabalho analisa os parâmetros atuais largamente utilizados pela indústria mostrando as suas vantagens e suas limitações. Testes experimentais foram realizados utilizando estes parâmetros na caracterização de superfícies de mancais após a sua fabricação bem como o seu desempenho em teste de vida acelerado. Foram utilizados um perfilômetro mecânico e um perfilômetro óptico para a medição dos parâmetros de superfície. É mostrado que os parâmetros de rugosidade Ra, Rsk, Rk, Sbi, Sci e Svi podem ser usados para caracterizar um processo de fabricação de uma superfície bem como a sua evolução topográfica num teste de vida acelerado. / The topographic characterization of engineering surfaces is very important in applications involving friction, wear and lubrication. This practice started in the 1930s and until now great efforts have been put to developing new methods for engineering surfaces. Although most of the surfaces are specified using 2D (two dimensions) parameters as Ra (average roughness), sometimes they are not enough to control and characterize the surface. A new group of parameters were developed which engineering and process designers are not only able to view their surfaces in much greater details, but they are also able to design and test surfaces with an eye toward functionality, i. e., to be produced, controlled and tested according to its application. The present work analyzes the present parameters widely used by the industry showing their advantages and their limitations. Experimental tests were carried out utilizing these parameters in the characterization of bearing surfaces after manufacturing as well its performance in the accelerated life test. Mechanical and optical profilers were used to make the measurements. It is shown that the parameters Ra, Rsk, Rk, Sbi, Sci and Svi can be used to characterize the surface manufacturing process as well its topographic evolution in an accelerated life test.

O presente trabalho propõe uma metodologia para o cálculo da vida e do coeficiente de segurança à fadiga, ou fatigue factor, para mancais hidrodinâmicos, mais comumente chamados de bronzinas. A metodologia proposta é confrontada com os resultados de um teste de fadiga dos referidos componentes, no qual se determina o limite de resistência à fadiga, ou endurance limit, pela análise estatística dos dados. Utilizou-se para tanto o método Staircase. Tal confrontação de resultados possibilita não só a validação experimental da metodologia proposta para a condição do teste efetuado, como também a proposição de futuros estudos com a finalidade de se estender o uso da metodologia não somente para bronzinas fabricadas com outros materiais, como também para a previsão da fadiga na condição de operação dos motores de combustão interna automotivos e também sua utilização em outros componentes mecânicos, como por exemplo molas de suspensão, desde que trabalhem em regime elástico. / The present work proposes a calculation methodology to predict the fatigue life as well as the fatigue safety factor, called fatigue factor, for the plain bearings. The proposed methodology is confronted with the results of a bearings fatigue test, performed to determine the endurance limit with the Staircase statistical analysis method. The results confrontation experimentally validates the proposed methodology, for the performed tests condition. Future studies are proposed to extend the methodology validation not only to bearings made with different materials, but also to predict fatigue on bearings under operation conditions of automotive internal combustion engines and its usage to other mechanical components under linear elastic behavior, such as suspension springs.

A caracterização da topografia de superfícies de engenharia é muito importante em aplicações envolvendo atrito, lubrificação e desgaste. Esta prática teve inicio na década de 30 e até os dias atuais vários esforços são desprendidos no sentido de desenvolver novos métodos para avaliação de superfícies. Embora a grande maioria das superfícies seja especificada por parâmetros 2D tais como Ra (rugosidade média) muitas vezes eles não são suficientes para controlar e caracterizar uma superfície. Novos parâmetros foram desenvolvidos onde engenheiros e processistas de manufatura não são somente capazes de ver as superfícies com muito mais detalhes, mas também são capazes de desenvolver e testar superfícies visando a sua funcionabilidade, ou seja, serem produzidas, controladas e testadas de acordo com a função que irão desempenhar na aplicação. O presente trabalho analisa os parâmetros atuais largamente utilizados pela indústria mostrando as suas vantagens e suas limitações. Testes experimentais foram realizados utilizando estes parâmetros na caracterização de superfícies de mancais após a sua fabricação bem como o seu desempenho em teste de vida acelerado. Foram utilizados um perfilômetro mecânico e um perfilômetro óptico para a medição dos parâmetros de superfície. É mostrado que os parâmetros de rugosidade Ra, Rsk, Rk, Sbi, Sci e Svi podem ser usados para caracterizar um processo de fabricação de uma superfície bem como a sua evolução topográfica num teste de vida acelerado. / The topographic characterization of engineering surfaces is very important in applications involving friction, wear and lubrication. This practice started in the 1930s and until now great efforts have been put to developing new methods for engineering surfaces. Although most of the surfaces are specified using 2D (two dimensions) parameters as Ra (average roughness), sometimes they are not enough to control and characterize the surface. A new group of parameters were developed which engineering and process designers are not only able to view their surfaces in much greater details, but they are also able to design and test surfaces with an eye toward functionality, i. e., to be produced, controlled and tested according to its application. The present work analyzes the present parameters widely used by the industry showing their advantages and their limitations. Experimental tests were carried out utilizing these parameters in the characterization of bearing surfaces after manufacturing as well its performance in the accelerated life test. Mechanical and optical profilers were used to make the measurements. It is shown that the parameters Ra, Rsk, Rk, Sbi, Sci and Svi can be used to characterize the surface manufacturing process as well its topographic evolution in an accelerated life test.

Active control constitutes the state of the art in vibration management in rotating machines. However, existing designs are impractical and costly, and hence not yet widely applied. The goal of the research reported here was to develop a design which would allow the implementation of active technology in a wider range of rotating machine applications. Thus, this study focuses on a novel active rotor topology, consisting of a hollow rotor with internally mounted sensors and actuators. This layout provides greater freedom to select the sensor and actuator positions along the rotor, and naturally protects the devices from harsh working environments. The research was structured according to four themes. Firstly, the concept feasibility was explored by constructing a fully functioning prototype. MEMS accelerometers and mass balancer actuators were mounted in an assembled rotor, together with a microcontroller and radio unit to enable wireless transmission of data. Secondly, the behaviour of MEMS accelerometers in a rotating frame of reference was studied. An output model was derived and applied to the study of whirl orbits and transient vibration. Further, techniques were developed to extract mean displacement and angular velocity information from the sensor signals. An analysis of potential sources of measurement error was conducted, and methods for their mitigation devised. The third theme focused on developing active vibration control techniques suitable for use with active rotors. The core of this work is the development and successful implementation of a non a priori method, Algorithmic Direct Search Control. This technique enables vibration to be minimised without knowledge of the system characteristics, by applying a direct search optimisation technique as a control law. Finally, the combination of active rotors and Active Magnetic Bearings was considered to tackle the problem of sensor/actuator non-collocation. The challenge of levitating a rotor on AMBs using only internal accelerometers was approached via integration-based displacement information extraction, to exploit existing PID controllers. This method proved unfeasible in practice, but valuable lessons were derived from the study. The key finding of this work is that active rotor technology is versatile, cost-effective, powerful and feasible. As such, it offers great potential as a route to achieving a more practical and generalised implementation of active control technology in rotating machinery.

No description available.

O presente trabalho propõe uma metodologia para o cálculo da vida e do coeficiente de segurança à fadiga, ou fatigue factor, para mancais hidrodinâmicos, mais comumente chamados de bronzinas. A metodologia proposta é confrontada com os resultados de um teste de fadiga dos referidos componentes, no qual se determina o limite de resistência à fadiga, ou endurance limit, pela análise estatística dos dados. Utilizou-se para tanto o método Staircase. Tal confrontação de resultados possibilita não só a validação experimental da metodologia proposta para a condição do teste efetuado, como também a proposição de futuros estudos com a finalidade de se estender o uso da metodologia não somente para bronzinas fabricadas com outros materiais, como também para a previsão da fadiga na condição de operação dos motores de combustão interna automotivos e também sua utilização em outros componentes mecânicos, como por exemplo molas de suspensão, desde que trabalhem em regime elástico. / The present work proposes a calculation methodology to predict the fatigue life as well as the fatigue safety factor, called fatigue factor, for the plain bearings. The proposed methodology is confronted with the results of a bearings fatigue test, performed to determine the endurance limit with the Staircase statistical analysis method. The results confrontation experimentally validates the proposed methodology, for the performed tests condition. Future studies are proposed to extend the methodology validation not only to bearings made with different materials, but also to predict fatigue on bearings under operation conditions of automotive internal combustion engines and its usage to other mechanical components under linear elastic behavior, such as suspension springs.

This master thesis investigates the performance of a car navigation system using lateral accelerometers, yaw rate and bearings relative three known radio beacons. Accelerometer, gyroscope and position data has been collected by an IMU combined with a GPS receiver, where the IMU was installed in the approximate motion center of a car. The bearing measurements are simulated using GPS data and the measurement noise model is derived from an experiment where the direction of arrival to one transmitter was estimated by an antenna array and the signal processing algorithm MUSIC. The measurements are fused in a multi-rate extended Kalman filter which assumes that all measurement noise is Gaussian distributed. This is not the case for the bearing measurement noise which contains outliers and therefore is modelled as a Gaussian uniform noise mixture. Different methods to deal with this have been investigated where the main focus is on the principle to use the Kalman filter’s innovation for each bearing measurement as an indication of its quality and discarding measurements with a quality above a certain threshold.

An objective in the design of high performance machinery is to minimize weight so magnetic bearings are often designed to operate slightly lower than the magnetic material saturation. Further weight reduction in the bearings requires operation in the nonlinear portion of the B-H curve. This necessitates a more sophisticated analysis at the bearing and rotordynamic system levels during the design stage. This dissertation addresses this problem in a unique manner by developing a fully nonlinear homopolar magnetic bearing model. The nonlinear dynamics of permanent magnet-biased homopolar magnetic bearing (PMB HoMB) system with 2-dof rigid and 4-dof flexible rotor is analyzed. The dynamic behavior of the rotor-bearing system is examined in the feedback control loop that includes low pass filter effects. An analytical magnetization curve model is proposed to predict the nonlinear magnetic force under the influence of the magnetic flux saturation more accurately. The modified Langmuir method with the novel correction terms for the weak flux region is used to curve-fit the experimental magnetization data of Hiperco 50. A new curve fit model of the B-H curve is shown to have significantly better agreement with the measured counterpart than conventional piecewise linear and other models. PMB HoMB characteristics with flux saturation, such as forces depending on the rotor position and bearing stiffness, are compared with these other models. Frequency response curve, bifurcation diagram, Poincare plot, and orbit plot are utilized to demonstrate the effects of the nonlinearities included in the 2-dof rotorbearing system. Due to heavy static loads applied to the rotor, it operates within the magnetic flux saturation region at the bearing clearance. The voltage saturation in the power amplifier of the magnetic bearing introduces lag in the control loop and the response of the heavily loaded 4-dof rotor-bearing system shows that limit cycle stability can be achieved due to the magnetic flux saturation or current saturation in the amplifier; otherwise the system would experience a destructive instability. These simulation results provide the first explanation of this commonly observed limit cycle which is referred to as ‘virtual catcher bearings’.

A general closed-form analytical solution is derived for the lapping tracks with its kinematics for the concentric V-groove lapping system. The lapping tracks on the ball surface for the three contact points are fixed circles, and their lengths of the lapping tracks are linearly proportional to , , and , respectively. In practice, if the orientation is randomized as the ball enters the lap again, then the distribution of the lapping tracks are dense after many cycles, and the larger the lapping length in each cycle, the smaller is the number of cycles required achieving the maximum lapped area ratio. In the geometry design of ball lapping, the V-groove half-angle should be larger than 45¢X, but to prevent the splash of abrasives, it should be less than 75¢X. Since the spin angular speed with its angle continuously varies with time for the eccentric lapping system, lapping tracks are not fixed circles. In practice, the lapped areas are complementary at the contact points of A and B. The total lapped area ratio is higher than 87% for a slip ratio less than 0.5. Hence, it is possible to lap all the surface of a ball by changing the slip ratio during the lapping process. Moreover, the larger the V-groove half-angle, the less is the eccentricity to achieve the optimum lapped area ratio. In order to understand the ball motion and ball lapping mechanism in the magnetic fluid lapping system, the forces and moments equilibrium equations are derived and numerical methods are analyzed. As the balls traveling in a train are assumed to be the same size, only one ball is considered in the dynamic analysis. Results show that as the ball separates from the shaft and the float, the spin angle increases quickly and approaches to 90¢X. Hence, the ball changes its attitude and thereby generates a new lapping tracks on the ball surface. Consequently, after repeating many cycles, lapping tracks would be scoping out more space and this is one of the spherical surface generation mechanisms. Surface waviness of ball causes a variation in the lapping load. When , it is possible to cause the ball separated from float and the lapping load is zero during the separation period. No matter how the ball separates from float, the spin angle always varies in a small range. Hence, only a very small region can be grounded due to the effect of the surface waviness. Therefore, it is not the main lapping mechanism of the spherical surface generation. In fact, during the lapping process, many balls with different diameters are lapped. To understand the ball¡¦s lapping mechanism of the spherical surface generation, it is necessary to consider a batch of balls. For a batch of balls with different diameters, the applied load on each should be different from each other. Generally, the larger the diameter of a ball, the larger is the friction force between the ball and shaft and the ball circulation speed. Therefore, it is possible to cause the collision between the larger and the smaller balls. To understand the interaction between balls traveling in a train, the dynamic analysis of multiple balls is developed. As the ball interacts with each other, it is possible to change the spin angle, and thereby to achieve the larger variation range of the lapping tracks. During the lapping process of a batch of balls, it is also possible to cause the separation between the shaft and the ball, and it causes the ball to change its attitude and to achieve more uniform lapping tracks.

Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2004. / Habetler, Thomas, Committee Member ; Sadegh Nader, Committee Member ; Taylor David, Committee Member ; Tsiotras Panagiotis, Committee Co-Chair ; Heck-Ferri Bonnie, Committee Co-Chair. Vita. Includes bibliographical references (leaves 319-326).