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In recent years, there has been considerable interest in developing efficient machine diagnostics and prognostics tools for quantitative estimation of systems condition and remaining useful life. Often, it is beneficial to combine several measures into a single feature for machine condition monitoring purposes. Selection of appropriate features represents a key step to satisfy machine condition monitoring requirements. Gearboxes represent one of those complex systems where classification of fault stages and types (diagnostics) and remaining useful life prediction (prognostics) remain a challenging task. This thesis focuses on certain aspects of engineering tribology related to gearbox components diagnostics and prognostics based on multi-sensor measurements. A dynamic large-scale mechanical system test-bed has been designed, built, and commissioned. This apparatus is based on the accessory gearbox of the GE J85 turbojet engine, which operates in a number of aircrafts, such as the Canadair CT-114 Tutor. The test rig is equipped with a high speed data acquisition system along with a variety of sensing technologies such as vibration, sound, and acoustic emission transducers in addition to thermocouples, power cells and loading mechanisms. Various attributes are compared for detecting faulty gears and a non-parametric statistical method is used as a quantitative measure of transmission quality. The feature importance level is determined by the significant difference level; and the independent coefficient of the candidate feature is used to compare and rank different time and frequency features. An optimal feature set is then evaluated using the support vector machine classification method by considering a monotonically increasing classification rate. In addition, the selected feature subset has the potential to achieve a better recognition rate than those selected by other heuristic methods such as the mutual information method. This thesis also introduces two metrics which identify the appropriate prognostic feature: load stability ratio and degradation value. The two criteria can be used to compare candidate prognostic features to determine which are most useful for prognosis. An optimization-based method is then used to obtain the optimal feature. The optimized feature can be used with a degradation path modeling to estimate RUL (remaining useful life) for the specific gear system. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2013-04-27 16:51:19.654

This research studied the tractive performance of integrated steering-drive systems by investigating a two-wheel-drive vehicle having two independent rear drive wheels and non-driven steerable front wheels. The feasibility of integrating the steering and drive systems and the performance advantages that may be obtained was investigated. In order to demonstrate the feasibility of the concept, the steering system and the drive system of a test vehicle were integrated using a computer with a specially-developed program. The software algorithm developed for the program used the mathematical relationship between the rear drive wheel speeds and the steer angles of the non-driven front wheels to set the steer angles. A test-bed vehicle was fitted with instrumentation to implement the computer-integrated system. The circuitry of the hydraulic lines of the hydraulically-driven test vehicle was modified to allow changes in drive configuration. These changes are not possible with conventional vehicles. The test vehicle could be configured for the following steering-drive configurations: open differential rear drive with steerable front wheels, independent rear drive wheels with front castors, locked differential rear drive with steerable front wheels and the computer-integrated steering-drive system developed. The sensors on the vehicle allowed data collection for characterising the vehicle and wheels. omputer models were developed for the various steering-drive configurations from the force relationships, longitudinal slip relationships, vehicle geometry and turning geometry. Characteristics of the test vehicle's wheels for use in the models were measured experimentally. he models were used to simulate the behaviour, and calculate the tractive performance, of the four steering-drive configurations in various situations but actual tests were not able to be conducted with the available resources. Unlike previous models, the models of this research used force and longitudinal slip information rather than power input and power output to produce values for drawbar efficiency. theoretical analysis was conducted into the optimal slip conditions for maximum tractive efficiency. The analysis was conducted using a more rigorous mathematical analysis than previous researchers and used a thorough graphical analysis to substantiate the mathematical analysis. Previous studies concluded that under all traction conditions the efficiency of slip will be a maximum when the slip of each wheel is equal. This research revealed that, contrary to the previous literature, efficiency of slip will not be a maximum when the slip of each wheel is equal under non-uniform traction conditions. The simulations were focussed on turning situations, non-uniform traction conditions and traversing slopes. The optimal slip conditions and steer angles for turning situations were also investigated and analysed. The computer-integrated steering-drive system achieved a drawbar pull 50% higher than that for a conventional open differential when undertaking a 10 m radius turn with non-uniform traction conditions. Under these conditions, the drawbar efficiency of the computer-integrated steering-drive system was 5% greater than that for the open differential at the lower drawbar pull. It was concluded that it is feasible and beneficial to use a computer-integrated steering system. Vehicles using such a system would operate more effectively and efficiently when turning under load, moving across slopes and in non-uniform traction conditions. More effectiveness was provided through greater drawbar pull and higher drawbar efficiency. / thesis (PhD)--University of South Australia, 2005.

Abstract The interaction among the tooth wear, dynamic loads, and its corresponding frequency spectrum variation in a spur gear pair is investigated in the dissertation. A mathematical model for the dynamic responses of a profile shifting involute gear pair is derived. For simplicity, a two-step mesh stiffness model is proposed to approximate the load sharing and the time-varying stiffness effects in a mating gear pair. The analytic solutions for the dynamic responses of this simplified dynamic model are derived in both time and frequency domains. The effect of the tooth wear on the spectrum variation has been illustrated analytically. The amplitude and frequency modulations introduced from the periodic load fluctuation have also been discussed. In order to characterize the time-varying mesh stiffness, frictional coefficient, damping ratio, temperature rise and load sharing effects between engaged teeth, a computational algorithm with the quasi-linear iteration procedure is developed to include above instantaneous parameters in the teeth engagement process. The tooth wear equation proposed by Flodin and Andersson (1997) is employed to simulate the mild wear process for an engaging gear pairs. The interactions between the tooth wear and the dynamic loads for the Steel/Steel, POM/POM, Nylon/Nylon and Steel/Nylon gears pair have been studied numerically. Numerical examples indicate that the proposed models are valid for gear pairs with different materials.

The load distribution across the contact line(s) of spur gears is essential for the gear designer to be able to accurately stress gears for a given application. Existing gear standards (eg BS 436, AGMA 218 DIN 3990) use a thin slice (2D) model of the meshing gear teeth to estimate the contact line load distribution. This approach clearly fails to model properly teeth subjected to mal-distributed loads, since the buttressing effect of adjacent tooth sections tends to flatten the load distribution. Non-linear tooth modifications such as crowning and some forms of lead correction are also inadequately modelled. This thesis sets out the theory for a 3D elastic model of widefaced- spur gears that has been implemented on a micro-computer. The required 3D contact line influence coefficients for standard form zero modification spur gears with 18 to 100 teeth have been determined by Finite Element analysis. These theoretical values have been compared with results from experiments carried out on a complete large module (18. Omm) wide-faced spur gear. The effect of the various elemental gear errors (eg pitch, profile, lead) and profile modifications have been investigated using the 3D computer model; the results compared with results predicted by the existing gear design standards. The existing gear standards use 2D tooth compliance values up to 50% less than those obtained in this work, largely due to inadequate modelling of the gear body compliance, which is most significant in gear wheels. Comparison of 3D tooth compliance values shows a large discrepancy between author's results again due to inadequate modelling of the gear body.

No description available.

This research studied the tractive performance of integrated steering-drive systems by investigating a two-wheel-drive vehicle having two independent rear drive wheels and non-driven steerable front wheels. The feasibility of integrating the steering and drive systems and the performance advantages that may be obtained was investigated. In order to demonstrate the feasibility of the concept, the steering system and the drive system of a test vehicle were integrated using a computer with a specially-developed program. The software algorithm developed for the program used the mathematical relationship between the rear drive wheel speeds and the steer angles of the non-driven front wheels to set the steer angles. A test-bed vehicle was fitted with instrumentation to implement the computer-integrated system. The circuitry of the hydraulic lines of the hydraulically-driven test vehicle was modified to allow changes in drive configuration. These changes are not possible with conventional vehicles. The test vehicle could be configured for the following steering-drive configurations: open differential rear drive with steerable front wheels, independent rear drive wheels with front castors, locked differential rear drive with steerable front wheels and the computer-integrated steering-drive system developed. The sensors on the vehicle allowed data collection for characterising the vehicle and wheels. omputer models were developed for the various steering-drive configurations from the force relationships, longitudinal slip relationships, vehicle geometry and turning geometry. Characteristics of the test vehicle's wheels for use in the models were measured experimentally. he models were used to simulate the behaviour, and calculate the tractive performance, of the four steering-drive configurations in various situations but actual tests were not able to be conducted with the available resources. Unlike previous models, the models of this research used force and longitudinal slip information rather than power input and power output to produce values for drawbar efficiency. theoretical analysis was conducted into the optimal slip conditions for maximum tractive efficiency. The analysis was conducted using a more rigorous mathematical analysis than previous researchers and used a thorough graphical analysis to substantiate the mathematical analysis. Previous studies concluded that under all traction conditions the efficiency of slip will be a maximum when the slip of each wheel is equal. This research revealed that, contrary to the previous literature, efficiency of slip will not be a maximum when the slip of each wheel is equal under non-uniform traction conditions. The simulations were focussed on turning situations, non-uniform traction conditions and traversing slopes. The optimal slip conditions and steer angles for turning situations were also investigated and analysed. The computer-integrated steering-drive system achieved a drawbar pull 50% higher than that for a conventional open differential when undertaking a 10 m radius turn with non-uniform traction conditions. Under these conditions, the drawbar efficiency of the computer-integrated steering-drive system was 5% greater than that for the open differential at the lower drawbar pull. It was concluded that it is feasible and beneficial to use a computer-integrated steering system. Vehicles using such a system would operate more effectively and efficiently when turning under load, moving across slopes and in non-uniform traction conditions. More effectiveness was provided through greater drawbar pull and higher drawbar efficiency. / thesis (PhD)--University of South Australia, 2005.

No description available.

No description available.

No description available.