Paul Meehan

Control of Chaotic Flutter in a Wind Turbine Airfoil

The primary aim of this project is to develop and verify a method of control of the occurrence of chaotic flutter in a wind turbine blade section to provide more efficient insight into its occurrence and avoidance in wind energy farms.

Investigation of the problem of rail corrugation

A widespread and apparently increasing phenomenon which has persisted in the railway industry for more than a century is the problem of rail corrugation. Rail corrugation is characterised by the formation of periodic light and dark bands along the tracks and is highly undesirable as it induces severe vibrations in the bogie. Much research has been performed in this area over the past decade however a cure remains elusive. The phenomenon involves the interaction between the dynamics of the vehicle (bogie), the contact mechanics occurring in the wheel/track interface and wear mechanics.

This thesis involves the advancement and testing of existing numerical models for rail corrugation via testrig and field measurement data.

Investigation and mathematical modelling of deep brain stimulation

Deep brain stimulation DBS is surgical technique used to mitigate the symptoms of a range of neurological disorders such as Parkinsons disease. The procedure involves insertion of an electrode into the brain and then application of pulsed voltage for stimulation. The purpose of this project is to develop a mathematical understanding of deep brain under DBS and investigate optimal conditions for DBS and/or interesting nonlinear phenomena.

Investigation and modelling of nonlinear phenomena in the cardiovascular system

A relatively new cross-disciplinary field of research is the identification and modelling of dynamic phenomena in biological systems. In particular, evidence of chaotic dynamics has been identified in the heart and brain and has surprisingly been associated with normal healthy functioning. In fact recent evidence suggests that abnormalities such as heart attacks and epileptic seizure are associated with linear periodic behaviour. It is of interest that pacemakers, in general, are designed to provide periodic behaviour, however, a better performance may be achieved if they can be designed to mimic the natural chaotic behaviour of a natural heart.

This project will involve an analytical and experimental investigation of nonlinear phenomena in the human cardiovascular system. In particular, a nonlinear controller will be developed and investigated using analytical, numerical and existing experimental models of the human cardiovascular system for use as a pacemaker.

Models to demonstrate nonlinear phenomena

The purpose of this project is to design and build physical models to demonstrate nonlinear phenomena in dynamics.

In particular, it is firstly aimed to develop one or more simple but demonstration sized models for demonstrating stability and conservation concepts in 3D rigid body motion. Possible models include the tippetop (a spinning top that inverts itself), the rattleback stone (a rigid body of unidirectional spin) and Chalygin's ball (a spherical but inertially asymmetric spinning ball).

Secondly, it is aimed to develop a simple demonstration model for showing chaotic instabilities in a spacecraft, dragline or another rotating multibody system.

The design parameters will be based upon theoretical predictions of phenomena in available literature. The thesis will be expected to contain a thorough review of this literature and theoretical calculations predicting the phenomena in the physical models.

Modelling and suppression of instabilities in tethered spacecraft

A number of investigations of spacecraft stability have been performed in the recent past, motivated by the observation of abnormalities occurring in the attitude dynamics of satellites. Attitude instabilities are highly detrimental to the high pointing accuracy required by communication satellites for antennas to provide the desired coverage. These observed instabilities have usually been found to arise the inherent nonlinearity of the system dynamics.

This project will investigate the occurrence and suppression of attitude instabilities in tethered spacecraft via analytical and numerical techniques. Tethered spacecraft systems are used to reduce fuel consumption and increase mission efficiency and safety. It is expected that this project will involve a significant amount of dynamic modelling, analysis, simulation and application of novel design/control techniques.

Investigation of the problem of wheel squeal

Wheel squeal is a highly undesirable high pitched noise that is emitted as a railway vehicle traverses a corner. A similar phenomena occurs in braking. Much research has been performed in this area to determine the causes and conditions of the phenomena to find a cure. The phenomenon involves the interaction between the dynamics of the vehicle (wheel) and the contact mechanics occurring in the wheel/track interface.

This thesis involves development and or upgrade of an existing analytical, simulation and laboratory modelling of wheel squeal under dry and friction modiofied conditions. Further or alternative investigation could be focused on a control method to suppress the phenomena to higher critical angle of attacks.

Modelling the dynamics of the inner ear

The inner ear is an extremely sophisticated instrument for converting mechanical vibrational energy to neural energy that our brain interprets as sound. The operation of this system has been shown to rely on highly nonlinear dynamics. This project will investigate simple nonlinear models for the dynamics of the inner ear and identify important phenomena associated with it.

Modelling fuel slosh in spacecraft

Typical spacecraft have a lifetime determined almost solely dependent on the amount of fuel (used during attitude manoeuvres) remaining in its tanks. The existing system of estimating the fuel remaining onboard is via recording a theoretical value of the amount of fuel used in each manoeuvre and summing this over the spacecraft's lifetime. This process allows for the propagation of significant errors in the estimate of the fuel remaining at the end of life.

This project will continue previous research that has proposed that has proposed a method by which a better estimate of fuel remaining may be obtained. The aim of this project is to further develop and tune analytical and numerical models of the spacecraft fuel slosh behaviour in order to accurately predict the amount of fuel remaining. The project has major interest from Cable & Wireless Optus and the satellite communications industry in general.

Investigation of dragline bucket swing instabilities

The occurrence of nonlinear instabilities is investigated in the swing motion of a dragline bucket during normal operation cycles. A simplified representative model of the dragline is developed in the form of a fundamental rotating multibody system with energy dissipation.An analytical predictive criterion for the onset of chaotic instability has been obtained using Melnikov’s method in terms of critical system parameters. These chaotic instabilities could introduce irregularities into the motion of the dragline system rendering the system difficult to control by the operator and/or would have undesirable affects on dragline productivity and fatigue lifetime. The sufficient analytical criterion for the onset of chaotic instability is shown to be a useful predictor of the phenomenon under steady and unsteady slewing conditions via comparisons with numerical results. It is aimed to validate these preliminary results by the development of a more realistic numerical model and/or experimental model.

Predictive Modelling and Control of the Incremental Forming Process

Incremental sheet forming (ISF) is a new flexible manufacturing process in which complex 3D shapes are formed from a sheet of metal using a simple moving tool (stylus). The non-specialised tool may be used to form an infinite variety of highly complex shapes in the same manner an artist is unrestricted with a simple brush. The project aim is to investigate and develop mechanics based predictive models or controllers for the nonlinear contact mechanics, localised plastic strain dynamics and tool trajectory to facilitate product design & optimisation.

Topics in dynamics and nonlinear mechanics

Various projects on modelling, simulation and control of dynamic nonlinear phenomena in railways, spacecraft, mining and biomechanical systems (deep brain, hearing, heart) systems.

Investigation of Brake Squeal

Brake squeal is an undesirable tonal noise that results from slowing of a vehicle with disk brakes. Unfortunately it remains it remains one of the most important issues for the automotive industry causing high levels of cutomer concerns and warranty costs. The phenomenon involves an unstable interaction between the modal dynamics of the brake system and the pad contact mechanics which can be due to different feedback mechanisms. Electric and hybrid vehicles still suffer from the problem as they require friction brake disks for heavy braking which they blend with regenerative braking.

This thesis involves the numerical and experimental investigation of the occurence of the phenomenon under different mechanisms to identify conditions to avoid brake squeal with a particular focus on controlling it under brake blending in electric and hybrid vehicles.

Control of an Advanced Flexible Chain-die Forming Process

Flexible Chain-die forming is a novel UQ patented advanced sheet metal forming technology which aims at manufacturing stronger, lighter and cheaper advanced high strength steel (AHSS) parts with improved quality and substantially lower energy consumption for many industries such automotive and clean energy systems.

The purpose of this research is to design, manufacture and optimize the advanced forming approach and the corresponding control system through analytical, numerical and experimental approaches. Flexible Chain-die forming is a highly non-linear complex deformation mechanism, where the deformation history of the sheet metal can be carefully designed due to the constraints provided by the tooling. These will result in significantly lowered longitudinal strain development, leading to a range of new products, lower cost of manufacturing by using fewer forming stands and smaller footprint.

The research will involve the development of an elasto-plastic finite element simulation model, analytical design of the transitional surface, the development of the control system, and experimental work to validate the performance of the designed system.

The PhD will focus on the design and validation of the control system.

Investigation of Railway Studs and Squats (advertised now)

The research seeks to develop a generalised validated mathematical model for rail studs, and in particular to examine how this mechanism differs from that for rail squats. Railway studs and squats are track defects that grow via dynamic loading over successive train wheel passages. The model would be used to predict growth of studs and to evaluate and determine optimum railway vehicle and track conditions to mitigate this rail defect. An extensive experimental and field study would be used to validate the results.

Preventing Offshore Wind-Turbine Dynamic Failures (advertised now)

Vortices shed in the wake of a subsea power cable, apply fluctuating hydrodynamic forces, causing the cable to vibrate. If the vortex shedding frequency approaches the natural frequency of the cable, high amplitude vibration known as ‘Vortex-Induced Vibration’ or VIV occurs. VIV induces bending of the cable and sliding between the layers of the cable structure, often resulting in fatigue failure. While the research body on the modelling of the dynamic response and fatigue behaviour of power cables is mature, simultaneous modelling of these phenomena is still in its infancy.

The project aims to develop an analytical, simulation and experimental framework that can model the multibody dynamic response and resulting fatigue damage accumulation in a unified manner. The analytical approach supported by more complex simulation and experimentation is preferred for the modelling of complex nonlinear phenomena.

A multibody simulation model will be developed using FE and multibody simulation models in conjunction with a widely used global hydrodynamic model, Orcaflex. The analytical reduced order model, known as the wake oscillator model, will be utilised to predict VIV conditions efficiently in a wider range investigation. In this modelling approach, the fluctuating forces generated by vortex shedding are idealised by a nonlinear oscillator with a limit cycle. The structural motion interacts with the wake oscillator through a forcing term, forming a coupled system. The team at UQ have used a similar approach for prediction of Aeolian vibration in power lines, wind turbine flutter, brake squeal and railway wheel squeal. The developed modelling approach will advance previous studies by considering the nonlinear bending response of the helically wound power cable armour and conductors, which may improve the accuracy of fatigue damage calculations. A range of cable configurations will be considered, aimed at developing preventative guidelines against premature fatigue failures.

Modelling and control of vibration instabilities in contact mechanical systems

Vibration Instabilities in Contact mechanical systems occur across a range of applications in railways systems.

Typical examples include false brinelling in railway bearings; a phenomenon that causes marks on bearing contact surfaces during transportation of new trains and subsequently leads to bearing failure, wheel squeal that is an undesirable tonal noise resulting from transverse sliding in the wheel/rail contact exciting vibrations of the wheel as a train negotiates a corner/curve; and similarly brake squeal that occurs typically when a train slows causes disk contact sliding energy to pass into the brake dynamics under undesirable conditions.

The purpose of this project is to mathematically model and experimentally test one or more of these phenomena before developing model-based predictive control techniques for avoidance or suppression of the instability.

Passive control of wind turbine tower vibration

The project will investigate novel vibration control techniques for wind turbines. The research will focus on refined modelling of aerodynamic loads and aeroelastic excitations. The outcomes are expected to widen the range of safe operating conditions, i.e., increase availability, of wind turbines.

Control of Chaotic Flutter in a Wind Turbine Airfoil

The primary aim of this project is to develop and verify a method of control of the occurrence of chaotic flutter in a wind turbine blade section to provide more efficient insight into its occurrence and avoidance in wind energy farms.

Investigation of the problem of rail corrugation

A widespread and apparently increasing phenomenon which has persisted in the railway industry for more than a century is the problem of rail corrugation. Rail corrugation is characterised by the formation of periodic light and dark bands along the tracks and is highly undesirable as it induces severe vibrations in the bogie. Much research has been performed in this area over the past decade however a cure remains elusive. The phenomenon involves the interaction between the dynamics of the vehicle (bogie), the contact mechanics occurring in the wheel/track interface and wear mechanics.

This thesis involves the advancement and testing of existing numerical models for rail corrugation via testrig and field measurement data.

Investigation and mathematical modelling of deep brain stimulation

Deep brain stimulation DBS is surgical technique used to mitigate the symptoms of a range of neurological disorders such as Parkinsons disease. The procedure involves insertion of an electrode into the brain and then application of pulsed voltage for stimulation. The purpose of this project is to develop a mathematical understanding of deep brain under DBS and investigate optimal conditions for DBS and/or interesting nonlinear phenomena.

Investigation and modelling of nonlinear phenomena in the cardiovascular system

A relatively new cross-disciplinary field of research is the identification and modelling of dynamic phenomena in biological systems. In particular, evidence of chaotic dynamics has been identified in the heart and brain and has surprisingly been associated with normal healthy functioning. In fact recent evidence suggests that abnormalities such as heart attacks and epileptic seizure are associated with linear periodic behaviour. It is of interest that pacemakers, in general, are designed to provide periodic behaviour, however, a better performance may be achieved if they can be designed to mimic the natural chaotic behaviour of a natural heart.

This project will involve an analytical and experimental investigation of nonlinear phenomena in the human cardiovascular system. In particular, a nonlinear controller will be developed and investigated using analytical, numerical and existing experimental models of the human cardiovascular system for use as a pacemaker.

Models to demonstrate nonlinear phenomena

The purpose of this project is to design and build physical models to demonstrate nonlinear phenomena in dynamics.

In particular, it is firstly aimed to develop one or more simple but demonstration sized models for demonstrating stability and conservation concepts in 3D rigid body motion. Possible models include the tippetop (a spinning top that inverts itself), the rattleback stone (a rigid body of unidirectional spin) and Chalygin's ball (a spherical but inertially asymmetric spinning ball).

Secondly, it is aimed to develop a simple demonstration model for showing chaotic instabilities in a spacecraft, dragline or another rotating multibody system.

The design parameters will be based upon theoretical predictions of phenomena in available literature. The thesis will be expected to contain a thorough review of this literature and theoretical calculations predicting the phenomena in the physical models.

Modelling and suppression of instabilities in tethered spacecraft

A number of investigations of spacecraft stability have been performed in the recent past, motivated by the observation of abnormalities occurring in the attitude dynamics of satellites. Attitude instabilities are highly detrimental to the high pointing accuracy required by communication satellites for antennas to provide the desired coverage. These observed instabilities have usually been found to arise the inherent nonlinearity of the system dynamics.

This project will investigate the occurrence and suppression of attitude instabilities in tethered spacecraft via analytical and numerical techniques. Tethered spacecraft systems are used to reduce fuel consumption and increase mission efficiency and safety. It is expected that this project will involve a significant amount of dynamic modelling, analysis, simulation and application of novel design/control techniques.

Investigation of the problem of wheel squeal

Wheel squeal is a highly undesirable high pitched noise that is emitted as a railway vehicle traverses a corner. A similar phenomena occurs in braking. Much research has been performed in this area to determine the causes and conditions of the phenomena to find a cure. The phenomenon involves the interaction between the dynamics of the vehicle (wheel) and the contact mechanics occurring in the wheel/track interface.

This thesis involves development and or upgrade of an existing analytical, simulation and laboratory modelling of wheel squeal under dry and friction modiofied conditions. Further or alternative investigation could be focused on a control method to suppress the phenomena to higher critical angle of attacks.

Modelling the dynamics of the inner ear

The inner ear is an extremely sophisticated instrument for converting mechanical vibrational energy to neural energy that our brain interprets as sound. The operation of this system has been shown to rely on highly nonlinear dynamics. This project will investigate simple nonlinear models for the dynamics of the inner ear and identify important phenomena associated with it.

Modelling fuel slosh in spacecraft

Typical spacecraft have a lifetime determined almost solely dependent on the amount of fuel (used during attitude manoeuvres) remaining in its tanks. The existing system of estimating the fuel remaining onboard is via recording a theoretical value of the amount of fuel used in each manoeuvre and summing this over the spacecraft's lifetime. This process allows for the propagation of significant errors in the estimate of the fuel remaining at the end of life.

This project will continue previous research that has proposed that has proposed a method by which a better estimate of fuel remaining may be obtained. The aim of this project is to further develop and tune analytical and numerical models of the spacecraft fuel slosh behaviour in order to accurately predict the amount of fuel remaining. The project has major interest from Cable & Wireless Optus and the satellite communications industry in general.

Investigation of dragline bucket swing instabilities

The occurrence of nonlinear instabilities is investigated in the swing motion of a dragline bucket during normal operation cycles. A simplified representative model of the dragline is developed in the form of a fundamental rotating multibody system with energy dissipation.An analytical predictive criterion for the onset of chaotic instability has been obtained using Melnikov’s method in terms of critical system parameters. These chaotic instabilities could introduce irregularities into the motion of the dragline system rendering the system difficult to control by the operator and/or would have undesirable affects on dragline productivity and fatigue lifetime. The sufficient analytical criterion for the onset of chaotic instability is shown to be a useful predictor of the phenomenon under steady and unsteady slewing conditions via comparisons with numerical results. It is aimed to validate these preliminary results by the development of a more realistic numerical model and/or experimental model.

Predictive Modelling and Control of the Incremental Forming Process

Incremental sheet forming (ISF) is a new flexible manufacturing process in which complex 3D shapes are formed from a sheet of metal using a simple moving tool (stylus). The non-specialised tool may be used to form an infinite variety of highly complex shapes in the same manner an artist is unrestricted with a simple brush. The project aim is to investigate and develop mechanics based predictive models or controllers for the nonlinear contact mechanics, localised plastic strain dynamics and tool trajectory to facilitate product design & optimisation.

Topics in dynamics and nonlinear mechanics

Various projects on modelling, simulation and control of dynamic nonlinear phenomena in railways, spacecraft, mining and biomechanical systems (deep brain, hearing, heart) systems.

Investigation of Brake Squeal

Brake squeal is an undesirable tonal noise that results from slowing of a vehicle with disk brakes. Unfortunately it remains it remains one of the most important issues for the automotive industry causing high levels of cutomer concerns and warranty costs. The phenomenon involves an unstable interaction between the modal dynamics of the brake system and the pad contact mechanics which can be due to different feedback mechanisms. Electric and hybrid vehicles still suffer from the problem as they require friction brake disks for heavy braking which they blend with regenerative braking.

This thesis involves the numerical and experimental investigation of the occurence of the phenomenon under different mechanisms to identify conditions to avoid brake squeal with a particular focus on controlling it under brake blending in electric and hybrid vehicles.

Development and Investigation of an Advanced Flexible Chain-die Forming Process

Flexible Chain-die forming is a novel UQ patented advanced sheet metal forming technology which aims at manufacturing new families of lighter, stronger, cheaper and greener advanced high strength steel (AHSS) parts. 2 PhDs are required for: a) mechanical design and realization of the former and b) optimization of the tooling and process.

Control of an Advanced Flexible Chain-die Forming Process

Flexible Chain-die forming is a novel UQ patented advanced sheet metal forming technology which aims at manufacturing stronger, lighter and cheaper advanced high strength steel (AHSS) parts with improved quality and substantially lower energy consumption for many industries such automotive and clean energy systems.

The purpose of this research is to design, manufacture and optimize the advanced forming approach and the corresponding control system through analytical, numerical and experimental approaches. Flexible Chain-die forming is a highly non-linear complex deformation mechanism, where the deformation history of the sheet metal can be carefully designed due to the constraints provided by the tooling. These will result in significantly lowered longitudinal strain development, leading to a range of new products, lower cost of manufacturing by using fewer forming stands and smaller footprint.

The research will involve the development of an elasto-plastic finite element simulation model, analytical design of the transitional surface, the development of the control system, and experimental work to validate the performance of the designed system.

The PhD will focus on the design and validation of the control system.

Investigation and modelling of nonlinear phenomena in the cardiovascular system

A relatively new cross-disciplinary field of research is the identification and modelling of dynamic phenomena in biological systems. In particular, evidence of chaotic dynamics has been identified in the heart and brain and has surprisingly been associated with normal healthy functioning. In fact recent evidence suggests that abnormalities such as heart attacks and epileptic seizure are associated with linear periodic behaviour. It is of interest that pacemakers, in general, are designed to provide periodic behaviour, however, a better performance may be achieved if they can be designed to mimic the natural chaotic behaviour of a natural heart.

This project will involve an analytical and experimental investigation of nonlinear phenomena in the human cardiovascular system. In particular, a nonlinear controller will be developed and investigated using analytical, numerical and existing experimental models of the human cardiovascular system for use as a pacemaker.

Models to demonstrate nonlinear phenomena

The purpose of this project is to design and build physical models to demonstrate nonlinear phenomena in dynamics.

In particular, it is firstly aimed to develop one or more simple but demonstration sized models for demonstrating stability and conservation concepts in 3D rigid body motion. Possible models include the tippetop (a spinning top that inverts itself), the rattleback stone (a rigid body of unidirectional spin) and Chalygin's ball (a spherical but inertially asymmetric spinning ball).

Secondly, it is aimed to develop a simple demonstration model for showing chaotic instabilities in a spacecraft, dragline or another rotating multibody system.

The design parameters will be based upon theoretical predictions of phenomena in available literature. The thesis will be expected to contain a thorough review of this literature and theoretical calculations predicting the phenomena in the physical models.

Modelling and suppression of instabilities in tethered spacecraft

A number of investigations of spacecraft stability have been performed in the recent past, motivated by the observation of abnormalities occurring in the attitude dynamics of satellites. Attitude instabilities are highly detrimental to the high pointing accuracy required by communication satellites for antennas to provide the desired coverage. These observed instabilities have usually been found to arise the inherent nonlinearity of the system dynamics.

This project will investigate the occurrence and suppression of attitude instabilities in tethered spacecraft via analytical and numerical techniques. Tethered spacecraft systems are used to reduce fuel consumption and increase mission efficiency and safety. It is expected that this project will involve a significant amount of dynamic modelling, analysis, simulation and application of novel design/control techniques.

Investigation of the problem of wheel squeal

Wheel squeal is a highly undesirable high pitched noise that is emitted as a railway vehicle traverses a corner. A similar phenomena occurs in braking. Much research has been performed in this area to determine the causes and conditions of the phenomena to find a cure. The phenomenon involves the interaction between the dynamics of the vehicle (wheel) and the contact mechanics occurring in the wheel/track interface.

This thesis involves development and or upgrade of an existing analytical, simulation and laboratory modelling of wheel squeal under dry and friction modiofied conditions. Further or alternative investigation could be focused on a control method to suppress the phenomena to higher critical angle of attacks.

Modelling the dynamics of the inner ear

The inner ear is an extremely sophisticated instrument for converting mechanical vibrational energy to neural energy that our brain interprets as sound. The operation of this system has been shown to rely on highly nonlinear dynamics. This project will investigate simple nonlinear models for the dynamics of the inner ear and identify important phenomena associated with it.

Modelling fuel slosh in spacecraft

Typical spacecraft have a lifetime determined almost solely dependent on the amount of fuel (used during attitude manoeuvres) remaining in its tanks. The existing system of estimating the fuel remaining onboard is via recording a theoretical value of the amount of fuel used in each manoeuvre and summing this over the spacecraft's lifetime. This process allows for the propagation of significant errors in the estimate of the fuel remaining at the end of life.

This project will continue previous research that has proposed that has proposed a method by which a better estimate of fuel remaining may be obtained. The aim of this project is to further develop and tune analytical and numerical models of the spacecraft fuel slosh behaviour in order to accurately predict the amount of fuel remaining. The project has major interest from Cable & Wireless Optus and the satellite communications industry in general.

Investigation of dragline bucket swing instabilities

The occurrence of nonlinear instabilities is investigated in the swing motion of a dragline bucket during normal operation cycles. A simplified representative model of the dragline is developed in the form of a fundamental rotating multibody system with energy dissipation.An analytical predictive criterion for the onset of chaotic instability has been obtained using Melnikov’s method in terms of critical system parameters. These chaotic instabilities could introduce irregularities into the motion of the dragline system rendering the system difficult to control by the operator and/or would have undesirable affects on dragline productivity and fatigue lifetime. The sufficient analytical criterion for the onset of chaotic instability is shown to be a useful predictor of the phenomenon under steady and unsteady slewing conditions via comparisons with numerical results. It is aimed to validate these preliminary results by the development of a more realistic numerical model and/or experimental model.

Predictive Modelling and Control of the Incremental Forming Process

Incremental sheet forming (ISF) is a new flexible manufacturing process in which complex 3D shapes are formed from a sheet of metal using a simple moving tool (stylus). The non-specialised tool may be used to form an infinite variety of highly complex shapes in the same manner an artist is unrestricted with a simple brush. The project aim is to investigate and develop mechanics based predictive models or controllers for the nonlinear contact mechanics, localised plastic strain dynamics and tool trajectory to facilitate product design & optimisation.

Topics in dynamics and nonlinear mechanics

Various projects on modelling, simulation and control of dynamic nonlinear phenomena in railways, spacecraft, mining and biomechanical systems (deep brain, hearing, heart) systems.

Investigation of Brake Squeal

Brake squeal is an undesirable tonal noise that results from slowing of a vehicle with disk brakes. Unfortunately it remains it remains one of the most important issues for the automotive industry causing high levels of cutomer concerns and warranty costs. The phenomenon involves an unstable interaction between the modal dynamics of the brake system and the pad contact mechanics which can be due to different feedback mechanisms. Electric and hybrid vehicles still suffer from the problem as they require friction brake disks for heavy braking which they blend with regenerative braking.

This thesis involves the numerical and experimental investigation of the occurence of the phenomenon under different mechanisms to identify conditions to avoid brake squeal with a particular focus on controlling it under brake blending in electric and hybrid vehicles.

Investigation of Railway Studs and Squats (advertised now)

The research seeks to develop a generalised validated mathematical model for rail studs, and in particular to examine how this mechanism differs from that for rail squats. Railway studs and squats are track defects that grow via dynamic loading over successive train wheel passages. The model would be used to predict growth of studs and to evaluate and determine optimum railway vehicle and track conditions to mitigate this rail defect. An extensive experimental and field study would be used to validate the results.

Modelling and control of vibration instabilities in contact mechanical systems

Vibration Instabilities in Contact mechanical systems occur across a range of applications in railways systems.

Typical examples include false brinelling in railway bearings; a phenomenon that causes marks on bearing contact surfaces during transportation of new trains and subsequently leads to bearing failure, wheel squeal that is an undesirable tonal noise resulting from transverse sliding in the wheel/rail contact exciting vibrations of the wheel as a train negotiates a corner/curve; and similarly brake squeal that occurs typically when a train slows causes disk contact sliding energy to pass into the brake dynamics under undesirable conditions.

The purpose of this project is to mathematically model and experimentally test one or more of these phenomena before developing model-based predictive control techniques for avoidance or suppression of the instability.

Passive control of wind turbine tower vibration

The project will investigate novel vibration control techniques for wind turbines. The research will focus on refined modelling of aerodynamic loads and aeroelastic excitations. The outcomes are expected to widen the range of safe operating conditions, i.e., increase availability, of wind turbines.

Control of Chaotic Flutter in a Wind Turbine Airfoil

The primary aim of this project is to develop and verify a method of control of the occurrence of chaotic flutter in a wind turbine blade section to provide more efficient insight into its occurrence and avoidance in wind energy farms.

Preventing Offshore Wind-Turbine Dynamic Failures (advertised now)

Vortices shed in the wake of a subsea power cable, apply fluctuating hydrodynamic forces, causing the cable to vibrate. If the vortex shedding frequency approaches the natural frequency of the cable, high amplitude vibration known as ‘Vortex-Induced Vibration’ or VIV occurs. VIV induces bending of the cable and sliding between the layers of the cable structure, often resulting in fatigue failure. While the research body on the modelling of the dynamic response and fatigue behaviour of power cables is mature, simultaneous modelling of these phenomena is still in its infancy.

The project aims to develop an analytical, simulation and experimental framework that can model the multibody dynamic response and resulting fatigue damage accumulation in a unified manner. The analytical approach supported by more complex simulation and experimentation is preferred for the modelling of complex nonlinear phenomena.

A multibody simulation model will be developed using FE and multibody simulation models in conjunction with a widely used global hydrodynamic model, Orcaflex. The analytical reduced order model, known as the wake oscillator model, will be utilised to predict VIV conditions efficiently in a wider range investigation. In this modelling approach, the fluctuating forces generated by vortex shedding are idealised by a nonlinear oscillator with a limit cycle. The structural motion interacts with the wake oscillator through a forcing term, forming a coupled system. The team at UQ have used a similar approach for prediction of Aeolian vibration in power lines, wind turbine flutter, brake squeal and railway wheel squeal. The developed modelling approach will advance previous studies by considering the nonlinear bending response of the helically wound power cable armour and conductors, which may improve the accuracy of fatigue damage calculations. A range of cable configurations will be considered, aimed at developing preventative guidelines against premature fatigue failures.

Investigation of the problem of rail corrugation

A widespread and apparently increasing phenomenon which has persisted in the railway industry for more than a century is the problem of rail corrugation. Rail corrugation is characterised by the formation of periodic light and dark bands along the tracks and is highly undesirable as it induces severe vibrations in the bogie. Much research has been performed in this area over the past decade however a cure remains elusive. The phenomenon involves the interaction between the dynamics of the vehicle (bogie), the contact mechanics occurring in the wheel/track interface and wear mechanics.

This thesis involves the advancement and testing of existing numerical models for rail corrugation via testrig and field measurement data.

Investigation and mathematical modelling of deep brain stimulation

Deep brain stimulation DBS is surgical technique used to mitigate the symptoms of a range of neurological disorders such as Parkinsons disease. The procedure involves insertion of an electrode into the brain and then application of pulsed voltage for stimulation. The purpose of this project is to develop a mathematical understanding of deep brain under DBS and investigate optimal conditions for DBS and/or interesting nonlinear phenomena.

Control of an Advanced Flexible Chain-die Forming Process (Advertised now)

Flexible Chain-die forming is a novel UQ patented advanced sheet metal forming technology which aims at manufacturing stronger, lighter and cheaper advanced high strength steel (AHSS) parts with improved quality and substantially lower energy consumption for many industries such automotive and clean energy systems.

The purpose of this research is to design, manufacture and optimize the advanced forming approach and the corresponding control system through analytical, numerical and experimental approaches. Flexible Chain-die forming is a highly non-linear complex deformation mechanism, where the deformation history of the sheet metal can be carefully designed due to the constraints provided by the tooling. These will result in significantly lowered longitudinal strain development, leading to a range of new products, lower cost of manufacturing by using fewer forming stands and smaller footprint.

The research will involve the development of an elasto-plastic finite element simulation model, analytical design of the transitional surface, the development of the control system, and experimental work to validate the performance of the designed system.

The PhD will focus on the design and validation of the control system.

Investigation of an Advanced Flexible Chain-die Forming Process (Advertised now)

Flexible Chain-die forming is a novel UQ patented advanced sheet metal forming technology which aims at manufacturing new families of lighter, stronger, cheaper and greener advanced high strength steel (AHSS) parts. 2 PhDs are required for: a) mechanical design and realization of the former and b) optimization of the tooling and process.

Investigation of Railway Studs and Squats (advertised now)

The research seeks to develop a generalised validated mathematical model for rail studs, and in particular to examine how this mechanism differs from that for rail squats. Railway studs and squats are track defects that grow via dynamic loading over successive train wheel passages. The model would be used to predict growth of studs and to evaluate and determine optimum railway vehicle and track conditions to mitigate this rail defect. An extensive experimental and field study would be used to validate the results.

Investigation of dragline bucket swing instabilities

The occurrence of nonlinear instabilities is investigated in the swing motion of a dragline bucket during normal operation cycles. A simplified representative model of the dragline is developed in the form of a fundamental rotating multibody system with energy dissipation.An analytical predictive criterion for the onset of chaotic instability has been obtained using Melnikov’s method in terms of critical system parameters. These chaotic instabilities could introduce irregularities into the motion of the dragline system rendering the system difficult to control by the operator and/or would have undesirable affects on dragline productivity and fatigue lifetime. The sufficient analytical criterion for the onset of chaotic instability is shown to be a useful predictor of the phenomenon under steady and unsteady slewing conditions via comparisons with numerical results. It is aimed to validate these preliminary results by the development of a more realistic numerical model and/or experimental model.

Modelling and control of vibration instabilities in contact mechanical systems

Vibration Instabilities in Contact mechanical systems occur across a range of applications in railways systems.

Typical examples include false brinelling in railway bearings; a phenomenon that causes marks on bearing contact surfaces during transportation of new trains and subsequently leads to bearing failure, wheel squeal that is an undesirable tonal noise resulting from transverse sliding in the wheel/rail contact exciting vibrations of the wheel as a train negotiates a corner/curve; and similarly brake squeal that occurs typically when a train slows causes disk contact sliding energy to pass into the brake dynamics under undesirable conditions.

The purpose of this project is to mathematically model and experimentally test one or more of these phenomena before developing model-based predictive control techniques for avoidance or suppression of the instability.

Preventing Offshore Wind-Turbine Dynamic Failures (advertised now)

Vortices shed in the wake of a subsea power cable, apply fluctuating hydrodynamic forces, causing the cable to vibrate. If the vortex shedding frequency approaches the natural frequency of the cable, high amplitude vibration known as ‘Vortex-Induced Vibration’ or VIV occurs. VIV induces bending of the cable and sliding between the layers of the cable structure, often resulting in fatigue failure. While the research body on the modelling of the dynamic response and fatigue behaviour of power cables is mature, simultaneous modelling of these phenomena is still in its infancy.

The project aims to develop an analytical, simulation and experimental framework that can model the multibody dynamic response and resulting fatigue damage accumulation in a unified manner. The analytical approach supported by more complex simulation and experimentation is preferred for the modelling of complex nonlinear phenomena.

A multibody simulation model will be developed using FE and multibody simulation models in conjunction with a widely used global hydrodynamic model, Orcaflex. The analytical reduced order model, known as the wake oscillator model, will be utilised to predict VIV conditions efficiently in a wider range investigation. In this modelling approach, the fluctuating forces generated by vortex shedding are idealised by a nonlinear oscillator with a limit cycle. The structural motion interacts with the wake oscillator through a forcing term, forming a coupled system. The team at UQ have used a similar approach for prediction of Aeolian vibration in power lines, wind turbine flutter, brake squeal and railway wheel squeal. The developed modelling approach will advance previous studies by considering the nonlinear bending response of the helically wound power cable armour and conductors, which may improve the accuracy of fatigue damage calculations. A range of cable configurations will be considered, aimed at developing preventative guidelines against premature fatigue failures.

Investigation of the problem of rail corrugation

A widespread and apparently increasing phenomenon which has persisted in the railway industry for more than a century is the problem of rail corrugation. Rail corrugation is characterised by the formation of periodic light and dark bands along the tracks and is highly undesirable as it induces severe vibrations in the bogie. Much research has been performed in this area over the past decade however a cure remains elusive. The phenomenon involves the interaction between the dynamics of the vehicle (bogie), the contact mechanics occurring in the wheel/track interface and wear mechanics.

This thesis involves the advancement and testing of existing numerical models for rail corrugation via testrig and field measurement data.

Investigation and modelling of nonlinear phenomena in the cardiovascular system

A relatively new cross-disciplinary field of research is the identification and modelling of dynamic phenomena in biological systems. In particular, evidence of chaotic dynamics has been identified in the heart and brain and has surprisingly been associated with normal healthy functioning. In fact recent evidence suggests that abnormalities such as heart attacks and epileptic seizure are associated with linear periodic behaviour. It is of interest that pacemakers, in general, are designed to provide periodic behaviour, however, a better performance may be achieved if they can be designed to mimic the natural chaotic behaviour of a natural heart.

This project will involve an analytical and experimental investigation of nonlinear phenomena in the human cardiovascular system. In particular, a nonlinear controller will be developed and investigated using analytical, numerical and existing experimental models of the human cardiovascular system for use as a pacemaker.

Topics in dynamics and nonlinear mechanics

Various projects on modelling, simulation and control of dynamic nonlinear phenomena in railways, spacecraft, mining and biomechanical systems (deep brain, hearing, heart) systems.

Modelling fuel slosh in spacecraft

Typical spacecraft have a lifetime determined almost solely dependent on the amount of fuel (used during attitude manoeuvres) remaining in its tanks. The existing system of estimating the fuel remaining onboard is via recording a theoretical value of the amount of fuel used in each manoeuvre and summing this over the spacecraft's lifetime. This process allows for the propagation of significant errors in the estimate of the fuel remaining at the end of life.

This project will continue previous research that has proposed that has proposed a method by which a better estimate of fuel remaining may be obtained. The aim of this project is to further develop and tune analytical and numerical models of the spacecraft fuel slosh behaviour in order to accurately predict the amount of fuel remaining. The project has major interest from Cable & Wireless Optus and the satellite communications industry in general.

Predictive Modelling and Control of the Incremental Forming Process (Advertised now)

Incremental sheet forming (ISF) is a new flexible manufacturing process in which complex 3D shapes are formed from a sheet of metal using a simple moving tool (stylus). The non-specialised tool may be used to form an infinite variety of highly complex shapes in the same manner an artist is unrestricted with a simple brush. The project aim is to investigate and develop mechanics based predictive models or controllers for the nonlinear contact mechanics, localised plastic strain dynamics and tool trajectory to facilitate product design & optimisation.

Investigation and mathematical modelling of deep brain stimulation

Deep brain stimulation DBS is surgical technique used to mitigate the symptoms of a range of neurological disorders such as Parkinsons disease. The procedure involves insertion of an electrode into the brain and then application of pulsed voltage for stimulation. The purpose of this project is to develop a mathematical understanding of deep brain under DBS and investigate optimal conditions for DBS and/or interesting nonlinear phenomena.

Control of Chaotic Flutter in a Wind Turbine Airfoil (Advertised now)

The primary aim of this project is to develop and verify a method of control of the occurrence of chaotic flutter in a wind turbine blade section to provide more efficient insight into its occurrence and avoidance in wind energy farms.

Investigation of Brake Squeal

Brake squeal is an undesirable tonal noise that results from slowing of a vehicle with disk brakes. Unfortunately it remains it remains one of the most important issues for the automotive industry causing high levels of cutomer concerns and warranty costs. The phenomenon involves an unstable interaction between the modal dynamics of the brake system and the pad contact mechanics which can be due to different feedback mechanisms. Electric and hybrid vehicles still suffer from the problem as they require friction brake disks for heavy braking which they blend with regenerative braking.

This thesis involves the numerical and experimental investigation of the occurence of the phenomenon under different mechanisms to identify conditions to avoid brake squeal with a particular focus on controlling it under brake blending in electric and hybrid vehicles.

Investigation of the problem of wheel squeal

Wheel squeal is a highly undesirable high pitched noise that is emitted as a railway vehicle traverses a corner. A similar phenomena occurs in braking. Much research has been performed in this area to determine the causes and conditions of the phenomena to find a cure. The phenomenon involves the interaction between the dynamics of the vehicle (wheel) and the contact mechanics occurring in the wheel/track interface.

This thesis involves development and or upgrade of an existing analytical, simulation and laboratory modelling of wheel squeal under dry and friction modiofied conditions. Further or alternative investigation could be focused on a control method to suppress the phenomena to higher critical angle of attacks.

Models to demonstrate nonlinear phenomena

The purpose of this project is to design and build physical models to demonstrate nonlinear phenomena in dynamics.

In particular, it is firstly aimed to develop one or more simple but demonstration sized models for demonstrating stability and conservation concepts in 3D rigid body motion. Possible models include the tippetop (a spinning top that inverts itself), the rattleback stone (a rigid body of unidirectional spin) and Chalygin's ball (a spherical but inertially asymmetric spinning ball).

Secondly, it is aimed to develop a simple demonstration model for showing chaotic instabilities in a spacecraft, dragline or another rotating multibody system.

The design parameters will be based upon theoretical predictions of phenomena in available literature. The thesis will be expected to contain a thorough review of this literature and theoretical calculations predicting the phenomena in the physical models.

Passive control of wind turbine tower vibration

The project will investigate novel vibration control techniques for wind turbines. The research will focus on refined modelling of aerodynamic loads and aeroelastic excitations. The outcomes are expected to widen the range of safe operating conditions, i.e., increase availability, of wind turbines.

Modelling and suppression of instabilities in tethered spacecraft

A number of investigations of spacecraft stability have been performed in the recent past, motivated by the observation of abnormalities occurring in the attitude dynamics of satellites. Attitude instabilities are highly detrimental to the high pointing accuracy required by communication satellites for antennas to provide the desired coverage. These observed instabilities have usually been found to arise the inherent nonlinearity of the system dynamics.

This project will investigate the occurrence and suppression of attitude instabilities in tethered spacecraft via analytical and numerical techniques. Tethered spacecraft systems are used to reduce fuel consumption and increase mission efficiency and safety. It is expected that this project will involve a significant amount of dynamic modelling, analysis, simulation and application of novel design/control techniques.

Modelling the dynamics of the inner ear

The inner ear is an extremely sophisticated instrument for converting mechanical vibrational energy to neural energy that our brain interprets as sound. The operation of this system has been shown to rely on highly nonlinear dynamics. This project will investigate simple nonlinear models for the dynamics of the inner ear and identify important phenomena associated with it.