Hydrodynamic journal bearings are applied in a wide range of both old and new, advanced rotating machinery designs. To maintain existing machinery, as well as to design new, state of the art machines, validated analytical models for these bearings are needed. This work documents the development and evaluation of an automated test rig for the evaluation of hydrodynamic journal bearings to provide some of the needed experimental data. This work describes the test rig in detail, including the results of experimental characterization of many of the test rig subsystems. Experimental data for a two axial groove bearing and a pressure dam bearing under steady load conditions are presented for a range of loads at two different shaft speeds. Experimental data and analytical results for dynamic loading are also discussed. The work concludes with a summary of the state of the test rig and recommendations for further work. / Ph. D.

A novel tilting pad journal bearing model including pivot flexibility as well as temporal fluid inertia effects on the thin film fluid flow aims to accurately predict the bearing forced performance. The predictive model also accounts for the thermal energy transport effects in a TPJB. A Fortran program with an Excel GUI models TPJBs and delivers predictions of the bearing static and dynamic forced performance. The calculation algorithm uses a Newton-Raphson procedure for successful iterations on the equilibrium pad radial and transverse displacements and journal center displacements, even for bearings pads with very soft pivots. The predictive model accounts for the effect of film temperature on the operating bearing and pad clearances by calculating the thermal expansion of the journal and pad surfaces. The pad inlet thermal mixing coefficient (lambda) influences moderately the predicted fluid film temperature field. Pad pivot flexibility decreases significantly and dominates the bearing stiffness and damping coefficients when the pivot stiffness is lower than 10% of the fluid film stiffness coefficients (with rigid pivots). Pivot flexibility has a more pronounced effect on reducing the bearing damping coefficients than the stiffness coefficients. Pad pivot flexibility may still affect the bearing behavior at a light load condition for a bearing with a large pad preload. Pad pivot flexibility, as well as the fluid inertia and the pads’ mass and mass moment of inertia, could influence the bearing impedance coefficients, in particular at high whirl frequencies. The stiffness and damping coefficients of a TPJB increase with a reduction in the operating bearing and pad clearances. The work delivers a predictive tool benchmarked against a number of experimental results for test bearings available in the recent literature. The static and dynamic forced performance characteristics of actual TPJBs can not be accurately predicted unless their pad flexibility and pivot flexibility, fluid film temperature, pad inlet thermal mixing coefficient, operating bearing and pad clearances, among others are well known in advance. However, the extensive archival literature showcasing test procedures and experimental results for TPJBs does not report the above parameters. Thus, reasonable assumptions on the magnitude of certain elusive parameters for use in the predictive TPJB model are necessary.

The master’s thesis deals with a design of a radial journal bearing simulator, which is ready to implement a transparent sapphire journal bearing to an optical observation of the oil film. The first part of this thesis contains a short review of a few currently used journal bearing test rigs. The next part of the work deals with a discussion of concept variants and a definition of important parameters. The last part contains a detailed description of the designed radial journal bearing simulator. Limitations of the designed simulator and recommendations for future improvements are also discussed. The result of the presented work is the designed journal bearing simulator which will allow observing of the oil film. The work also consists a complete design documentation.

<p>This thesis work is an evaluation of journal bearings in manual transmissions in automobiles. Today both journal- and needle bearings can be positioned into the gearboxes and in order to reduce the power loss developed by friction when a relative angular velocity arises, the right type of bearing must be chosen.</p><p>In order to succeed, this work is aimed to develop a Matlab simulation model, which should be used as a tool in the design process of manual transmissions. The program development is later supposed to be followed by real tests of journal bearings, partly to cover things that can not be covered in the model but also to confirm how well the model reflects the reality. The absence of resources resulted in no performed real test and therefore was a comparison between theoretical-  and practical results not possible.</p><p>Here the plain journal bearings in full film lubrication will have an disadvantage compared to the needle bearings regarding the power lost. To reduce the drag below the values of the needle bearings a modified journal bearing in the area of boundary lubrication with a very low coefficient of friction may be an option. But problems with wear under this condition could most certainly be devastating and must be further investigated with real tests.</p><p>Out of a efficiency point of view the most suitable bearing position is the gear in the most frequently used area. Here it is assumed to be the 4^th gear.</p><p>A suitable journal bearing design should have a small sliding surface area in order to minimize the viscous drag. To achieve low friction the boundary lubricated area could be a good idea in cases when wear is not a critical factor. To longer the useful life nitrocarburizing is recommended, which both reduces wear and lower the coefficient of friction, in cases of asperites in contact. In order to work under the full film lubricated condition, with neglected wear, the sliding area needs to be large enough to create the required oil pressure.</p>

This thesis work is an evaluation of journal bearings in manual transmissions in automobiles. Today both journal- and needle bearings can be positioned into the gearboxes and in order to reduce the power loss developed by friction when a relative angular velocity arises, the right type of bearing must be chosen. In order to succeed, this work is aimed to develop a Matlab simulation model, which should be used as a tool in the design process of manual transmissions. The program development is later supposed to be followed by real tests of journal bearings, partly to cover things that can not be covered in the model but also to confirm how well the model reflects the reality. The absence of resources resulted in no performed real test and therefore was a comparison between theoretical-  and practical results not possible. Here the plain journal bearings in full film lubrication will have an disadvantage compared to the needle bearings regarding the power lost. To reduce the drag below the values of the needle bearings a modified journal bearing in the area of boundary lubrication with a very low coefficient of friction may be an option. But problems with wear under this condition could most certainly be devastating and must be further investigated with real tests. Out of a efficiency point of view the most suitable bearing position is the gear in the most frequently used area. Here it is assumed to be the 4th gear. A suitable journal bearing design should have a small sliding surface area in order to minimize the viscous drag. To achieve low friction the boundary lubricated area could be a good idea in cases when wear is not a critical factor. To longer the useful life nitrocarburizing is recommended, which both reduces wear and lower the coefficient of friction, in cases of asperites in contact. In order to work under the full film lubricated condition, with neglected wear, the sliding area needs to be large enough to create the required oil pressure.

Health condition monitoring, commonly referred as Integrated Vehicle Health Management (IVHM) for fleets or vehicles, studies the current and future health state of a system. Health monitoring techniques based on data driven approaches have proven successful in several areas and are easily scalable; however they do not rely on the understating of the physics of failure; whereas Physics-based Model (PbM) approaches require expert knowledge of the failure modes and are based on the understanding of the component behaviour and degradation mechanisms. The development of IVHM is particularly challenging for legacy aircraft due to the restrictive regulations of the aerospace industry. This thesis proposes a novel PbM technique to detect metal-metal contact in hydrodynamic bearings. The planetary transmission of an aircraft’s Integrated Drive Generator (IDG) is used as a case study. Research on the detection of metal-metal contact in hydrodynamic bearings has focused on data driven approaches using vibration or acoustic emissions rather than on PbMs. The proposed technique estimates metal-metal contact by modelling the physical phenomena involved in the failure mechanism and only the speed, load and temperature are required as inputs, all of them available in the IDG and not requiring any additional sensors. The study of metal-metal in hydrodynamic bearings in the field of tribology has focused on mixed lubrication models of the whole bearing, or computational models accounting for local effect under the hydrodynamic lubrication region. In addition to the IVHM technique, this thesis contributes to the field of tribology by proposing a computational mixed lubrication model capable of studying metal-metal contact locally along the lubricated surface of the bearing. Experimental results of a plain journal bearing have been used to validate the PbM and a replica of the transmission of the IDG has been tested to evaluate the effectiveness of the proposed technique at detecting metal-metal contact.

In this dissertation, the mechanical models of 2-DOF and 4-DOF nonlinear journal bearing rotor systems are established. A more accurate model of oil film forces is derived from Reynolds equations. The periodic motions in such nonlinear journal bearing systems are obtained through discrete mapping method. Such a semi-analytical method constructs an implicit discrete mapping structure for periodic motions by discretization of the continuous journal bearing rotor differential equations. Stable and unstable periodic solutions of periodic motions are obtained with prescribed accuracy. The bifurcation tree of periodic motions in rotor system without oil film forces is demonstrated through the route from period-1 motion to period-8 motion. Stable period-2 and unstable period-1 motion are presented for 2 DOF journal bearing rotor system. Possibly infinite periodic solutions are found in 4 DOF journal bearing rotor system. For the rotor systems, the stability and bifurcations of periodic motions are analyzed through eigenvalue analysis of the corresponding Jacobian matrix of the discretized nonlinear systems. The frequency amplitude characteristics of periodic motions in 2 DOF journal bearing system are presented for a good understanding of the nonlinear dynamics of journal bearing rotor system in frequency domain . The rich dynamics of the journal bearing systems are discovered. The numerical illustrations of stable periodic motions are brought out with the initial conditions from analytical prediction.

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