<p>Su&scaron;tina istraživanja u doktorskoj disertaciji je konkretna<br />upotreba matematičkog modela matrica u fazama<br />dijagnostike kao i izbor optimalnih parametara stanja ma&scaron;ina<br />pri radu i otkazu sastavnih komponenata ma&scaron;inskih sistema<br />(robota-manipulator, kompresora i pumpe). Takođe,<br />posredstvom matrica izvr&scaron;en je izbor održavanja sve u cilju<br />određivanja sigurnosti i funkcionisanja sastavnih<br />komponenti ma&scaron;inskih sistema.<br />Krajni cilj uspe&scaron;nosti modela matrica pri pocesu analize<br />dijagnostike i održavanja jeste da se izvr&scaron;i izbor najboljeg<br />re&scaron;enja ili najpoželjnije varijante koja će povisiti nivo<br />pouzdanosti čime će uticati na budući proces eksploatacije<br />ma&scaron;ine. Dati model matrica, kao i softverskih alata,<br />predstavljeni su kao modeli proračuna, dijagnostike,<br />održavanja i pouzdanosti ma&scaron;inskih sistema. Predstavljene<br />matrice su univerzalnog karaktera iz razloga &scaron;to se mogu<br />primeniti kako na jednostavne, tako i na složene ma&scaron;inske<br />sisteme, bez obzira na dimenzije komponenti ma&scaron;inskih<br />sistema i njihova kretanja.</p> / <p>The essence of research in his doctoral dissertation is the use<br />of a concrete mathematical model matrix phases of<br />diagnostics as the choice of optimal parameters of the state<br />machines at work and cancellation of the constituent<br />components of mechanical systems (robot-manipulator,<br />compressor and pumps). Also, through the matrix have been<br />selected maintenance of everything in order to determine the<br />security and functioning of the components of the mechanical<br />systems.<br />Final goal of model performance matrix analysis underway in<br />of diagnostics and maintenance is to make the selection of the<br />best solutions and most preferably variants that will increase<br />the level of reliability which will affect the future process of<br />exploitation of machines. Give a model matrix, as well as the<br />software tools are presented as models of the calculation,<br />diagnostics, maintenance and reliability of mechanical<br />systems. The presented matrices are universal character for<br />the reason that can be applied both on the simple and on<br />complex mechanical systems, regardless of the dimensions of<br />the components of mechanical systems and their movements.</p>

As the cost of land in cities increases, the need to build multistory buildings in close proximity to each other also increases. Sometimes, construction materials, other objects and any projections from a building may also decrease the spacing provided between the buildings. This leads to the problem of pounding of these closely placed buildings when responding to earthquake ground motion. The recent advent of base isolation systems and their use as an efficient earthquake force resisting mechanism has led to their increased use in civil engineering structures. At the same time, building codes that reflect best design practice are also evolving. The movement of these base isolated buildings can also result in building pounding. Since base isolation is itself a relatively new technique, pounding phenomenon in base isolated buildings have not been adequately investigated to date. This study looks at the base isolated response of a single two story building and adjacent two story building systems. Four earthquakes with increasing intensity were used in this study. It was found that it is difficult to anticipate the response of the adjacent buildings due to non- linear behavior of pounding and base isolation. The worst case for pounding was found to occur when a fixed base and base isolated buildings were adjacent to each other.

During the flight of missiles, depending on the flight conditions, rotation of missiles around its centerline can cause instabilities. To override this issue, missile generally is designed in 2 sections. In the missile, the rear tail section and the front section are to rotate freely by means of bearings. Tail section on which bearings are mounted is designed according to thermal loads due to flow of hot gasses through the nozzle and mechanical loads due to inertial load, interference fit and thread preload which appear during flight of missile. The purpose of this thesis is to determine the most suitable structural parameters according to the flight conditions of missile. The geometrical and load parameters which have effect on the results were determined. Finite element model is formed by using FEA software. After that, transient nonlinear thermo-mechanical analyses are performed and the most effective parameter on VM (Von-Mises) stress and force is determined. DOE (Design of Experiments) method was used to determine the most suitable values for the structural parameters. Totally 27 different configurations are studied to achieve to the most suitable values for variable set. It is observed that VM stress and force results for all configurations are within the &plusmn / %5 ranges. So this means parameters don&rsquo / t affect the systems response very much. By taking manufacturing processes into consideration, configuration with the highest bearing inner/outer ring interference is taken. From the comparison of the results, the most suitable configuration is obtained after checking forces and VM stress on the bearings.

ABSTRACT EFFECTS OF VERTICAL EXCITATION ON SEISMIC PERFORMANCE OF HIGHWAY BRIDGES AND HOLD-DOWN DEVICE REQUIREMENT Domani&ccedil / , Kemal Arman M.S., Department of Civil Engineering Supervisor: Assist. Prof. Dr. Alp Caner February 2008, 152 pages Most bridge specifications ignore the contribution of vertical motion in earthquake analyses. However, vertical excitation can develop significant damage, especially at bearing locations as indeed was the case in the recent 1999 izmit Earthquake. These observations, combined with recent developments in the same direction, supplied the motivation to investigate the effects of vertical component of strong ground motion on standard highway bridges in this study. Reliability checks of hold-down device requirements per AASHTO Bridge Specifications have been conducted in this context. Six spectrum compatible accelerograms were generated and time history analyses were performed to observe the uplift at bearings. Selected case studies included precast pre-stressed I-girders with concrete slab, composite steel I-girders, post-tensioned concrete box section, and composite double steel box section. According to AASHTO specifications, hold-down devices were required in two cases, for which actual forces obtained from time history analyses have been compared with those suggested per AASHTO. The only non-linearity introduced to the analyses was at the bearing level. A discussion of effects on substructure response as well as compressive bearing forces resulting from vertical excitation is also included. The results of the study confirmed that the provisions of AASHTO governing hold-down devices are essential and reasonably accurate. On the other hand, they might be interpreted as well to be suggesting that vertical ground motion components could also be included in the load combinations supplied by AASHTO, especially to be able to estimate pier axial forces and cap beam moments accurately under combined vertical and horizontal excitations.

The basic problem with angle-only or bearings-only tracking is to estimate the trajectory of a target (i.e., position and velocity) by using noise corrupted sensor angle data. In this thesis, the tracking platform is an Aerial Vehicle and the target is simulated as another Aerial Vehicle. Therefore, the problem can be defined as a single-sensor bearings only tracking. The state consists of relative position and velocity between the target and the platform. In the case where both the target and the platform travel at constant velocity, the angle measurements do not provide any information about the range between the target and the platform. The platform has to maneuver to be able to estimate the range of the target. Two problems are investigated and tested on simulated data. The first problem is tracking non-maneuvering targets. Extended Kalman Filter (EKF), Range Parameterized Kalman Filter and particle filter are implemented in order to track non-maneuvering targets. As the second problem, tracking maneuvering targets are investigated. An interacting multiple model (IMM) filter and different particle filter solutions are designed for this purpose. Kalman filter covariance matrix initialization and regularization step of the regularized particle filter are discussed in detail.

As the cost of land in cities increases, the need to build multistory buildings in close proximity to each other also increases. Sometimes, construction materials, other objects and any projections from a building may also decrease the spacing provided between the buildings. This leads to the problem of pounding of these closely placed buildings when responding to earthquake ground motion. The recent advent of base isolation systems and their use as an efficient earthquake force resisting mechanism has led to their increased use in civil engineering structures. At the same time, building codes that reflect best design practice are also evolving. The movement of these base isolated buildings can also result in building pounding. Since base isolation is itself a relatively new technique, pounding phenomenon in base isolated buildings have not been adequately investigated to date. This study looks at the base isolated response of a single two story building and adjacent two story building systems. Four earthquakes with increasing intensity were used in this study. It was found that it is difficult to anticipate the response of the adjacent buildings due to non- linear behavior of pounding and base isolation. The worst case for pounding was found to occur when a fixed base and base isolated buildings were adjacent to each other.

Advanced material handling systems' impact on flexible manufacturing systems (FMS) have increased the efficiency and work rate over conventional manufacturing assemblies. The interaction of automated guided vehicles (AGVs), roller conveyors and conveyor belts with robots and machine tools forms highly sophisticated assembly operations. Whilst material handling in FMS today is conventionally used to transport assembly units from one work station to another, it does not take an active role in the manufacturing process. With manufacturers implementing more advanced manufacturing principles to perform agile manufacturing, there is a growing need to implement "smarter" material handling systems that would perform essential, integral roles in the assembly process. This research outlines the development of a cordless linear synchronous motor (CLSM) material handling system. The CLSM incorporates a permanent magnet courier that moves without tether restrictions on an integrated reverse air bearing system which eliminates friction. The CLSM provides a material handling system with enhanced travel, flexibility and accuracy. The CLSM material handling system is designed to integrate with overhead manipulators and part feeders to form a comprehensive flexible manufacturing system. This research covers the 2-D finite element modeling (FEM) used to determine the CLSM's optimal parameters. The development of the motor windings design and construction, together with the control system for the CLSM, is also covered. The CLSM novel air bearing system is outlined and compared to other conventional linear bearing systems. The possible impact of the CLSM on current manufacturing systems is explored to determine the validity of the research project and possible further research opportunities. / Thesis (M.Sc.Eng)-University of Natal, Durban, 2000.

As a consequence of increasing wind power installations in the Nordic grid the last years, the need for regulating power has become larger. In the Nordic grid, regulating power is mainly provided by hydro power. One part of the regulating power is called frequency control, which ensures that the grid frequency is stable and close to 50 Hz. However, setting the turbine into frequency controlled operation may cause stress and wear of the components in the mechanical control system. Frequency controlling implies large and frequent servo forces and longer travelling distance of the sliding bearings in the Kaplan turbine. Based on one selected Kaplan turbine, Selsfors G1, measurements and MATLAB calculations have been performed in order to determine forces and movements of the linkage system. With these forces and movements as input, stresses and fatigue have been determined as well as sliding distances, bearing pressures and wear of bearings during a typical lifetime of 40 years. The results indicate that no severe wear exists on the bearings during 40 years of service. This is valid for Selsfors G1, where self-lubricating greaseless Orkot bearings are installed. The wear is much smaller than the largest allowed bearing clearance, as long as the bearings are mounted correctly and free from dirt and oil. For turbines with grease or oil lubricated bearings, the result might differ. The highest average stresses have been recorded in the links in the runner. A very simple Finite Element Analysis has been made for the links, to estimate risk of fatigue. The stresses are much lower compared to the fatigue limit, and thus the risk of fatigue is considered very small. In situations where wear and large load changes after all are problems, a change in the turbine regulator settings is recommended. A dead band reduces the sliding distances of the bearings and the amount of load changes remarkably, but causes on the other hand lower turbine efficiency and worse quality of the frequency control.

The use of bearings can be found in virtually all aspects of mechanical systems today. Reliability of these critical components is an important issue. Fatigue performance of bearings is a function of many factors, including service conditions, loading, material properties, environmental factors, and manufacturing processes. Crack nucleation, first spall generation and spall growth in rolling contact fatigue are known to be highly sensitive to the heterogeneity of the microstructure. Yet the current state-of-the-art in the design of high performance bearing materials and microstructures is highly empirical requiring substantial lengthy experimental testing to validate the reliability and performance of these new materials and processes. The approach presented here is designed to determine relative rolling contact fatigue performance as a function of microstructural attributes. A fully three-dimensional finite element modeling allows for end effects to be captured that were not previously possible with two-dimensional plane-strain models, providing for a more realistic assessment of inclusion morphology and arbitrary orientations. The scaling of the finite element models has been optimized to capture the cyclic microplasticity around a modeled inclusion accurately and efficiently. To achieve this, two scales of geometric models were developed to incorporate different sized microstructural phenomena, with both models using traction boundary conditions derived from Hertzian contact stresses. A microstructure-sensitive material model adds additional capability. A hybrid model that includes both martensite and austenite phases with additional internal state variable to track the volume fraction of retained austenite due to stress-assisted transformation were developed. This represents an advance over previous models where transform plasticity and crystal plasticity were not simultaneously accounted for in a homogenized element containing both phases. Important links between microstructural features and fatigue indicator parameters (and relative fatigue performance) were determined. Demonstration cases show the relationship between inclusion orientation and relative fatigue performance, allowing for the identification of critical angles which maximize fatigue and reduce performance. An additional case study showed that increasing initial volume fraction of retained austenite reduces relative fatigue life. The tools developed allow for investigations of the influence of many microstructural aspects on relative fatigue performance with a numerical model that were not previously possible.

Machines operating in dusty environments, such as mining and civil works, are prone to premature failure, leading to production losses. To address this problem, this research project examines the interaction between solid contaminants and the bearing micro-geometry, in lubricated surface contacts. In particular, it seeks to identify anti-wear additives that are effective in reducing wear under abrasive conditions, making machine elements more dirt tolerant. In general, the influence of antiwear additive is so small that it is difficult to isolate it. Manufactures often make claims about their antiwear products, which are difficult to verify. Hence, there is a need to characterising the antiwear additives available with a well-defined parameter, making it easier for consumers to compare the efficacy of various additives, and be able to select the most suitable additive for a given environment. Effect of micro-geometry parameters such as radial clearance, out-of-roughness and surface roughness was examined and a Film Shape Factor (FSF) – also termed gamma ratio – has been proposed for ensuring adequate separation of journal bearings operating in hydrodynamic lubrication regime, where the out-of-roundness values are higher than the surface roughness values. In this research, an experimental study has been conducted on journal bearings, to examine the influence of five antiwear additives on the bearing wear and micro-geometry. The test additives were provided by the industry partner without revealing their chemical identity or composition; however, these included some of the most commonly used antiwear additives. The tests were performed under three conditions: pure base oil, base oil containing contaminants, and base oil containing contaminants treated with five different additives. The experiments were aimed at choosing one wear measuring technique that evaluates the performance of an individual additive reliably, and based on this technique the additives were characterised. To achieve these objectives, a multi-wear parameter approach (MWPA) was developed, which employed three main wear measurement methodologies, i.e. weight loss, micro-geometry and particle counts –to examine the effect of the antiwear additives. Minimum oil film thickness was also measured to study the lubrication status in the bearing contacts. The MWPA helped in comparing different wear measuring methods, and in selecting the most reliable one. This approach also helped in developing short duration wear tests, thereby saving time, while still getting reliable results without repeating these. Wear experiments were performed on seven sets of bronze bearings and steel sleeve shafts. The test contaminant was 16 micron Aluminium oxide Al2O3 powder mixed in oil with 4% concentration by weight. These solid contaminants were treated with five different antiwear additives to study their influence on the bearings. Bearings were operated such that the minimum oil film thickness in the bearing was equal to the size of the contaminants. These tests were run for a constant sliding distance of 7536m. The results showed that most of the wear measuring techniques do not suit heavily contaminated test conditions. However, the out-of-roundness technique proved to be the most reliable and practical. Based on this technique a methodology was developed which gave a wear characteristic number (N). A unique value of N can be derived for each additive, thereby ranking the additives for their efficacy. The finding of this research provides a better understanding of the methodologies used for measuring wear in journal bearings subjected to dusty environments, and examines the efficacy of each one of these. The wear characteristic number (N) can be used by manufacturers with support from international standards organisations, so that the users can confidently choose the most appropriate antiwear additive for their application. Machines operating in a dusty environment, such as mining industry and civil works are prone to premature failure with subsequent production losses. In response to this problem, this research project examines the interaction between solid contaminant particles and the lubricant film micro-geometry in lubricated surface contacts. In particular, it seeks to identify lubricant anti-wear additives, which are effective in reducing wear under abrasive conditions and thus making machine elements more dirt tolerant.