<p>This master’s thesis work was performed at Volvo Powertrain in Köping, Sweden, which manufactures gearboxes and integrated transmission systems for heavy vehicles. The thesis is a continuation of a previous master’s thesis performed at the Köping factory in 2009. After manufacturing and assembly, each gearbox is manually validated to ensure the gearbox quality and functionality. When validating the gearbox gears, the operator shifts the gearbox in a predefined manner and listens for irregularities. If an error sound is heard the operator must then locate the source of error. With numerous of cog wheels rotating at the same time this task requires extensive knowledge and experience of the operator. The main objective is to develop an automatic diagnostic system for detection of cog errors and assist the operator in the process of locating the faulty component.</p><p>The work consists of two parts. In the first part the automatic diagnostic system is developed and a database of gearbox recordings is stored. The amounts of logged non-faulty gearboxes are significantly much larger (50) than the logged faulty gearboxes (1). Therefore, when determining thresholds needed for the diagnosis, the data obtained from the non-faulty gearboxes are used. Two statistical methods are presented to extract the thresholds. The first method uses an extremevalue distribution and the other method a Gaussian distribution. When validated, both methods did successfully detect on cog faults. In the second part an investigation is made of how shaft imbalance can be detected and implemented in the developed system.</p><p>Volvo Powertrain continually follows-up all faults found at the validation station to ensure the quality of their work and eliminate the sources of error. During system testing one logged gearbox was found faulty. The automatic diagnostic system did successfully detect and locate the faulty component which later also was confirmed when the gearbox was dismounted. With only one detected error it is difficult to conclude the system performance and further testing is required. However, during the testing no false detections were made.</p>

The five appended papers all deal with gearbox noise and vibration. The first paper presents a review of previously published literature on gearbox noise and vibration. The second paper describes a test rig that was specially designed and built for noise testing of gears. Finite element analysis was used to predict the dynamic properties of the test rig, and experimental modal analysis of the gearbox housing was used to verify the theoretical predictions of natural frequencies. In the third paper, the influence of gear finishing method and gear deviations on gearbox noise is investigated in what is primarily an experimental study. Eleven test gear pairs were manufactured using three different finishing methods. Transmission error, which is considered to be an important excitation mechanism for gear noise, was measured as well as predicted. The test rig was used to measure gearbox noise and vibration for the different test gear pairs. The measured noise and vibration levels were compared with the predicted and measured transmission error. Most of the experimental results can be interpreted in terms of measured and predicted transmission error. However, it does not seem possible to identify one single parameter, such as measured peak-to-peak transmission error, that can be directly related to measured noise and vibration. The measurements also show that disassembly and reassembly of the gearbox with the same gear pair can change the levels of measured noise and vibration considerably. This finding indicates that other factors besides the gears affect gear noise. In the fourth paper, the influence of bearing endplay or preload on gearbox noise and vibration is investigated. Vibration measurements were carried out at torque levels of 140 Nm and 400 Nm, with 0.15 mm and 0 mm bearing endplay, and with 0.15 mm bearing preload. The results show that the bearing endplay and preload influence the gearbox vibrations. With preloaded bearings, the vibrations increase at speeds over 2000 rpm and decrease at speeds below 2000 rpm, compared with bearings with endplay. Finite element simulations show the same tendencies as the measurements. The fifth paper describes how gearbox noise is reduced by optimizing the gear geometry for decreased transmission error. Robustness with respect to gear deviations and varying torque is considered in order to find a gear geometry giving low noise in an appropriate torque range despite deviations from the nominal geometry due to manufacturing tolerances. Static and dynamic transmission error, noise, and housing vibrations were measured. The correlation between dynamic transmission error, housing vibrations and noise was investigated in speed sweeps from 500 to 2500 rpm at constant torque. No correlation was found between dynamic transmission error and noise. Static loaded transmission error seems to be correlated with the ability of the gear pair to excite vibration in the gearbox dynamic system. / QC 20100923

This master’s thesis work was performed at Volvo Powertrain in Köping, Sweden, which manufactures gearboxes and integrated transmission systems for heavy vehicles. The thesis is a continuation of a previous master’s thesis performed at the Köping factory in 2009. After manufacturing and assembly, each gearbox is manually validated to ensure the gearbox quality and functionality. When validating the gearbox gears, the operator shifts the gearbox in a predefined manner and listens for irregularities. If an error sound is heard the operator must then locate the source of error. With numerous of cog wheels rotating at the same time this task requires extensive knowledge and experience of the operator. The main objective is to develop an automatic diagnostic system for detection of cog errors and assist the operator in the process of locating the faulty component. The work consists of two parts. In the first part the automatic diagnostic system is developed and a database of gearbox recordings is stored. The amounts of logged non-faulty gearboxes are significantly much larger (50) than the logged faulty gearboxes (1). Therefore, when determining thresholds needed for the diagnosis, the data obtained from the non-faulty gearboxes are used. Two statistical methods are presented to extract the thresholds. The first method uses an extremevalue distribution and the other method a Gaussian distribution. When validated, both methods did successfully detect on cog faults. In the second part an investigation is made of how shaft imbalance can be detected and implemented in the developed system. Volvo Powertrain continually follows-up all faults found at the validation station to ensure the quality of their work and eliminate the sources of error. During system testing one logged gearbox was found faulty. The automatic diagnostic system did successfully detect and locate the faulty component which later also was confirmed when the gearbox was dismounted. With only one detected error it is difficult to conclude the system performance and further testing is required. However, during the testing no false detections were made.

Wind energy accounts for 9.1% of the total energy capacity in Europe. Recent studies have raised critical questions regarding the dependability of current wind turbines. The statistical data reveals that gear box is the most critical component reducing dependability caused by increased failure rate, downtime, and high repair cost (J. Ribrant and L. Bertling, 2007). Gear box failures in wind farms reveal a staggering 19.4 % of downtime of operation (J. Ribrant and L. Bertling, 2007). A significant reduction in the failure rate has been observed in the recent years, but downtime of operation and high repair investment still remains a bottleneck. Wear is the most critical failure mode and a number of theories have been proposed in order to understand the system behavior of wear mechanism. The empirical and historical incident data shows that the lubrication system has the largest share of contribution of gearbox failures and wear rate. On other hand, a number of commercial lubrication system have developed to cope with wear mechanism, however, these systems have different capabilities and characteristics and needed to be assessed in a new life cycle perspective. The purpose of the thesis is to analyze the influence of lubrication system on the current problem of wear in Wind Turbine Gearbox and improve the existing lubrication system architecture. The research methodology adopted is System Engineering approach with architecture assessment tools. The expected result of the thesis is effective and efficient wind turbine gearbox lubrication system architecture and an efficient contractual process between lubrication system provider and purchaser.

Diese Arbeit beschäftigt sich mit den in konventionellen Handschaltgetrieben als auch in automatisierten Schaltgetrieben für die Funktion &amp;quot;Schalten/Leistungsfluss herstellen&amp;quot; verwendeten Zahnkupplungen. Einmal eingelegt soll der gewählte Gang bis zur Herausnahme durch den Fahrer den Leistungsfluss gewährleisten. Es gibt aber Getriebe, bei denen sich eine korrekt betätigte Schalteinrichtung während der Fahrt selbsttätig wieder entkoppelt. Mit der vorliegenden Arbeit wird dieses Problem, als „Gangspringen“ bezeichnet, erklärt und analysiert. Das Ergebnis dieser Arbeit sind Vorschläge und Möglichkeiten zur Vermeidung dieser Fehlfunktion.

Optimum design of multistep gearbox, since many high-performance power transmission applications (e.g., automotive, space industry) require compact volume, has become an important interest area. This design application includes more complicated problems that are not taken into account while designing single stage gear drives. Design applications are generally made by trial and error methods depending on the experience and the intuition of the designer. In this study, using Visual Basic 6.0, an interactive program is developed for designing multistep involute standard and nonstandard spur gearbox according to the American Gear Manufacturers Association (AGMA) Standards 218.01 and 2001- B88. All the equations for calculating the pitting resistance geometry factor I, and the bending strength geometry factor J, are valid for external spur gears that are generated by rack-type tools (rack cutters or hobs). The program is made for twostage to six-stage gear drives, which are commonly used in the industry. Compactness of gear pairs and gearbox, and equality of factor of safety against bending failure is taken as the design objective. By considering the total required gear ratio, the number of reduction stages is input by the user. Gear ratios of every stage is distributed to the stages according to the total gear ratio that satisfies the required precision (from &plusmn / 0.1 to &plusmn / 0.00001 on overall gear ratio) depending on the user selected constraints (unequal gear ratio for every stage, noninteger gear ratio e.g.). Dimensional design is determined by considering bending stress, pitting stress, and involute interference constraints. These steps are carried out iteratively until a desirable solution is acquired. The necessary parameters for configuration design such as number of teeth, module, addendum modification coefficient, are selected from previously determined gear pairs that satisfies the constraints by user interaction considering the performance criterion from the developed program. The positions of gears and shafts are determined automatically in order to keep the volume of gearbox as minimum while satisfying the nonlinear spatial constraints (center distance constraint for proper meshing of gear pairs, face distance constraint for proper assembly of pinion and gear having same shaft, gear interference constraint for preventing interferences between gears, shaft interference constraint for preventing interferences between gears and shafts) by using DLL (Dynamic Link Library) technology of Lingo 8.0 optimization software together with Visual Basic 6.0. If shaft interference constraint is removed then cantilevered mounting of gear pairs would also be possible, otherwise the gears should be mounted between bearings. Visual output of assembly is made by using Autodesk Inventor 7.0, automatically by the program.

Main goal of this master thesis is designing of a part of electric vehicle driving unit for mixed traffic. The drive purpose is to replace main drive of a utility van. First part of the thesis contains description of methodology used for energy consumption evaluation. In the next part there is description of current electric drive used in the van, design of a new one, best variant selection to suit company needs, energy consumption calculation, design and realization of the drive holder and final comparison of current and new drive design.

A crescente implementação pela indústria de técnicas de manutenção preditiva exige cada vez mais o aprimoramento dos procedimentos capazes de fornecer informações sobre o estado de um equipamento. Dentre os procedimentos de análise existentes para máquinas rotativas, a análise de vibração é um dos mais utilizados sendo, atualmente inclusive, presente em larga parcela de setores industriais importantes no Brasil (como o setor de celulose e papel, por exemplo). Isto faz, portanto, cada vez mais importante explorar todas as possibilidades desta técnica. Este trabalho inicia uma investigação sobre as relações entre vibração (assinatura mecânica) e lubrificação de máquinas rotativas e assim, como ponto de partida deste estudo, procura avaliar o efeito da variação da viscosidade do lubrificante no sinal de vibração de caixas de engrenagem. O trabalho apresenta um grande banco de dados experimental, discute diversos métodos de processamento de sinais e apresenta uma característica do sinal de vibração que foi capaz de identificar alterações na viscosidade do óleo lubrificante no caso apresentado. / The crescent implementation, by brazilian industry, of predictive maintenance techniques demands, from vibration analyses processes, more capability for supplying information on the state of equipment. Among the existent analysis procedures for rotative machines, the vibration analysis is one of the more used, being nowadays, present in a wide portion of important industrial sections in Brazil (as the cellulose pulp and paper for instance). This makes, therefore, more and more important to explore all of the possibilities of this method. This work begins an investigation about the relation between vibration (mechanical signature) and lubrication of rotative machines. As a starting point of this study, it tries to evaluate the effect of the variation of the viscosity of the lubricant on the vibration signature of a gear box. The work presents a large experimental database, discusses several methods of signal processing and presents a characteristic of the vibration signal capable to identify alterations in the viscosity of the lubricating oil in the tested equipment.

La boite de vitesses est un des principaux organes d’une automobile et son développement est complexe. De nombreuses contraintes doivent être prises en compte et notamment son comportement acoustique et vibratoire. Cet aspect de la conception est de nos jours assez mal maitrisé et les nuisances acoustiques des boites de vitesses, telle que le bruit de grenaille, sont bien souvent découvertes tardivement. L’objectif de ces travaux était le développement d’un modèle numérique de dynamique des engrenages applicable aux boites de vitesses et permettant de prédire les conditions d’apparition du bruit de grenaille. La modélisation proposée dans cette thèse repose sur une association originale de différentes modélisations et est applicable à la grande majorité des boites de vitesses. Les éléments flexibles tels que les arbres et les carters sont modélisés par la méthode des éléments-finis. Un modèle d’engrenage basé sur le modèle de contact de Kelvin-Voigt est développé. Ce dernier permet la prise en compte des pertes de contact et des chocs sur les flancs avants et arrières. Pour compléter la modélisation, des modèles de pertes mécaniques sont implémentés afin de prendre en compte l’influence des roulements, des paliers lisses, des synchroniseurs et du barbotage des pignons dans l’huile. Le modèle développé, couplé à un indicateur de bruit de grenaille, permet de réaliser des études de sensibilités afin d’identifier les paramètres influents sur le bruit de grenaille mais aussi de comparer les comportements vibratoires de différentes configurations. Pour finir, une campagne d’essais sur une boite de vitesse industrielle est réalisée et des résultats de simulations lui sont confrontés. / The gearbox is an important component of an automobile and its development is complex. Numerous constraints must be taken into account, particularly its noise and vibration behavior. This aspect of the conception is nowadays poorly mastered and the noise pollution of gearboxes, such as the rattle noise, are often discovered late. The aim of this work was the development of a numerical model of gear dynamics adapted to gearboxes’ modelling and allowing to predict the conditions of gear rattle noise appearance. The model proposed in this thesis is based on an original combination of different models and is applicable to the vast majority of gearboxes. Flexible components, such as shafts and housings are modeled by the finite element method. A gear model based on Kelvin-Voigt contact model is developed. It allows to take into account the contact losses and the back side contacts. To complete this model, mechanical loss models are implemented in order to take into account the influence of the bearings, plain bearings, synchronizers and gears’ immersion in oil. This model coupled with a noise indicator allows for sensitivity analyzes to identify influential parameters on the rattle noise but also to compare the dynamic behavior of different configurations. Finally, a test campaign on an industrial gerbox is conducted and simulation results are confronted to measurements.

Vibration monitoring is widely used to determine the condition of various mechanical systems. Traditionally a transducer is attached to the structure under investigation and the vibration signal recorded. This signal is then processed and the required information extracted from the signal. With epicyclic gearboxes this traditional approach is not advisable. This is in part due to the fact that the planet gears rotate internally on a planet carrier. Special techniques are therefore required to extract a viable data signal from the measured vibration signal. These techniques require an additional post-processing step in which a compiled data signal is extracted from the measured data signal. This work investigates the possibility of mounting transducers internally on the rotating planet carrier. Mounting transducers at this location removes the relative motion seen in traditional measurement techniques. An epicyclic gearbox is modified to facilitate the internal mounting of the accelerometers. A number of implementation problems are highlighted and solutions to these problems are discussed. A large portion of the work is dedicated to implementing and qualifying the epicyclic time synchronous averaging technique which is traditionally used to evaluate epicyclic gearboxes. As this technique forms the basis to evaluate the data obtained from internal measurements, it is of fundamental importance that the technique is implemented correctly. It is shown that vibration data can be reliably measured internally, by means of accelerometers mounted on the planet carrier. The internally measured data is compared to data obtained by traditional techniques and shown to be equally adept in detecting deterioration of a planet gear tooth. Simple condition indicators were used to compare the vibration data of the two techniques. It was seen that the data obtained from the internally mounted accelerometers was equally, and in certain cases, slightly more sensitive to planet gear damage. This implies that the technique can be used successfully to evaluate epicyclic gearbox damage. There are a number of practical implementation problems that will limit the use of this technique. As the technology becomes available to transmit measured vibration signals wirelessly, the application of the internal measurement technique will become more viable. A preliminary investigation was also launched into the relationship between a planetary gearbox with a single planet gear and one with multiple planet gears. It is illustrated that vibration data, measured from a gearbox containing a single planet gear, shows an increased sensitivity to planet gear damage. Although a special test rig might be required, the increased sensitivity to damage can provide a method to test planet gears in critical applications such as aircraft gearboxes. Copyright / Dissertation (MEng)--University of Pretoria, 2010. / Mechanical and Aeronautical Engineering / unrestricted