http://hdl.handle.net/10197/3156 2013-06-18T05:47:40Z http://hdl.handle.net/10197/4014 Boundary-controlled travelling and standing waves in cascaded lumped systems O'Connor, William; Zhu, Ming This paper describes how pure travelling waves in cascaded, lumped, uniform, mass-spring systems can be defined, established, and maintained, by controlling two boundary actuators, one at each end. In most cases the control system for each actuator requires identifying and measuring notional component waves, propagating in opposite directions, through the actuator-system interfaces. These measured component waves are then used to form the control inputs to the actuators. The paper also shows how the boundaries can be actively controlled to establish and maintain standing waves of arbitrary standing wave ratio, including those corresponding to classical modes of vibration with textbook boundary conditions. The proposed control systems are also robust to system disturbances: they react quickly to overcome external transient disturbances to re-establish the desired steady motion. The 2nd Joint International Conference on Multibody System Dynamics , Stuttgart, Germany, May, 2012 2012-03-15T00:00:00Z http://hdl.handle.net/10197/4013 Wave-based control of under-actuated flexible structures with strong external disturbing forces O'Connor, William; Habibi, Hossein Wave-based control (WBC) of underactuated, flexible systems considers actuator motion as launching a mechanical wave into the flexible system which it then absorbs on its return to the actuator. The launching and absorbing proceed simultaneously. This simple, intuitive idea leads to robust, generic, highly efficient, precise, adaptable controllers, allowing rapid and almost vibrationless re-positioning of the system, using only sensors colocated at the actuator-system interface. These wave-based ideas have already been shown to work on simple systems such as mass-spring strings, systems of Euler-Bernoulli beams, and flexible space structures undergoing slewing motion (rotation with lateral translation). The current work extends this strategy to systems experiencing external disturbing forces, whether body forces which endure over time, such as gravitational effects which change with system orientation, or transient forces such as from impacts or external viscous damping. The revised strategy additionally provides robustness to some sensor errors.  The strategy has the controller learn about the disturbances and compensate for them, yet without needing new sensors or measurements beyond those of standard WBC. The 2nd Joint International Conference on Multibody System Dynamics, Stuttgart, Germany, May, 2012 2012-05-01T00:00:00Z http://hdl.handle.net/10197/4012 Travelling waves in boundary-controlled, non-uniform, cascaded lumped systems O'Connor, William; Zhu, Ming A companion paper in this conference considers travelling and standing waves in cascaded, lumped, mass-spring systems, controlled by two boundary actuators, one at each end, when the system is uniform. It first proposes definitions of waves in finite lumped systems. It then shows how to control the actuators to establish desired waves from rest, and maintain them despite disturbances. The present paper extends this work to the more general, non-uniform case, when mass and spring values are arbitrary. A special "bi-uniform" case is first studied, consisting of two different uniform cascaded systems in series, with an obvious, uncontrolled, impedance mismatch where they meet. The paper shows how boundary actuator control systems can be designed to establish, and robustly maintain, apparently pure travelling waves of constant amplitude in either the first or the second uniform section, in each case with an appropriate standing wave pattern in the other section. Then a more general non-uniform case is studied. A definition of a "pure travelling wave" in non-uniform systems is proposed. Curiously, it does not imply constant amplitude motion. It does however yield maximum power transfer between boundary actuators. The definition, and its implementation in a control system, involves extending the notions of "pure" travelling waves, standing waves, and input and output impedances of sources and loads, when applied to non-uniform lumped systems. Practical, robust control strategies are presented for all cases. The 2nd Joint International Conference on Multibody System Dynamics, Stuttgart, Germany, May, 2012 2012-10-12T00:00:00Z http://hdl.handle.net/10197/4011 Multibody domain decomposition for parallel processing: a wave-based approach to handling interface dynamics Smoothey, Craig; O'Connor, William For many good reasons there is growing interest in ways to allow parallel processing of multibody dynamics problems. Some recent approaches include “Domain Decomposition” and “Divide and Conquer”. This paper explores a new approach, reported as work in progress, with initial, promising results. The strategy is an extension of work done on wave analysis of lumped systems in another context. In the approach, a larger system is subdivided into smaller subsystems, which are solved in parallel. Interconnection points are boundaries for each. Dynamic coupling across boundaries is handled in terms of transmitted and reflected motion components (or "waves"), in both directions, across the boundaries. The 2nd Joint International Conference on Multibody System Dynamics, Stuttgart, Germany, May, 2012 2012-05-01T00:00:00Z http://hdl.handle.net/10197/4010 Wave-Based Analysis and Control of Lump-Modeled Flexible Robots O'Connor, W.J.; O'Connor, William Flexible robots are frequently represented by lumped models. In the mechanics of lumped systems, wave concepts have been avoided, for good reasons, generally. In the control of lumped flexible systems, however, wave concepts prove very fruitful. This paper provides a foundation for the wave-based control application by exploring the validity and nature of wave concepts in lumped robotic systems. A new wave-based model of uniform mass-spring systems is proposed and verified. The model is exact but not unique. Useful simplifications and approximations are also presented. The model leads to control strategies for flexible robotic systems that are simple, powerful, robust, and generic. The wave approach also provides a new analysis tool and conceptual framework for lumped dynamic systems. 2007-04-01T00:00:00Z http://hdl.handle.net/10197/4009 Wave-Echo Control of Lumped Flexible Systems O'Connor, William An elegant, generic solution is presented to the problem of point-to-point control by a single actuator of a remote load through an intermediate flexible system, modelled by a system of lumped masses and springs. It is based on new ways of looking at the problem that respect and exploit the underlying dynamics. Under wide-ranging conditions the strategy allows rapid, almost-vibrationless, precise position control of the load, independently of the order of the system, without the need for a detailed system model or ideal actuator. During the start-up, the system itself reveals to the controller how to terminate the motion, so that the real system also acts as the model for the controller. The scheme is very robust to modelling, actuator and sensor errors. The strategy is presented, with some of the motivating ideas reviewed. 2006-12-22T00:00:00Z http://hdl.handle.net/10197/4008 Wave-based control of non-linear flexible mechanical systems O'Connor, William; Ramos de la Flor, Francisco; McKeown, David; Feliu, Vicente The need to achieve rapid and accurate position control of a system end-point by an actuator working through a flexible system arises frequently, in cases from space structures to disk drive heads, from medical mechanisms to long-arm manipulators, from cranes to special robots. The system’s actuator must then attempt to reconcile two, potentially conflicting, demands: position control and active vibration damping. Somehow each must be achieved while respecting the other’s requirements. Wave-based control is a powerful solution with many advantages over previous techniques. The central idea is to consider the actuator motion as launching mechanical waves into the flexible system while simultaneously absorbing returning waves. This simple, intuitive idea leads to robust, generic, highly efficient, adaptable controllers, allowing rapid and almost vibrationless re-positioning of the remote load (tip mass). This gives a generic, high-performance solution to this important problem that does not depend on an accurate system model or near-ideal actuator behaviour. At first sight wave-based control assumes superposition and therefore linearity. This paper shows that wave-based control is also robust (or can easily be made robust) to non-linear behaviour associated with non-linear elasticity and with large-deflection effects. 2009-07-01T00:00:00Z http://hdl.handle.net/10197/4006 Boundary-controlled travelling and standing waves in cascaded lumped systems O'Connor, William; Zhu, Ming This paper shows how pure travelling waves in cascaded, lumped, uniform, mass-spring systems can be defined, established, and maintained, by controlling two boundary actuators, one at each end. In most cases the control system for each actuator requires identifying and measuring the notional component waves propagating in opposite directions at the actuator-system interfaces. These measured component waves are then used to form the control inputs to the actuators. The paper also shows how the boundaries can be actively controlled to establish and maintain standing waves of arbitrary standing wave ratio, including those corresponding to the classical modes of vibration of such systems with textbook boundary conditions. These vibration modes are achieved and maintained by controlled reflection of the pure travelling wave components. The proposed control systems are also robust to system disturbances: they react to overcome external disturbances quickly and so to re-establish the desired steady motion. The Second Joint International Conference on Multibody System Dynamics: Stuttgart, Germany, May 29 - June 1, 2012 2012-05-01T00:00:00Z http://hdl.handle.net/10197/4005 Travelling waves in boundary-controlled, non-uniform, cascaded lumped systems O'Connor, William; Zhu, Ming A companion paper considers travelling and standing waves in cascaded, lumped, mass-spring systems, controlled by two boundary actuators, one at each end, when the system is uniform. It first proposes definitions of waves in finite lumped systems. It then shows how to control the actuators to establish desired waves from rest, and to maintain them despite disturbances. The present paper extends this work to the more general, non-uniform case, when mass and spring values can be arbitrary. A special ¿bi-uniform¿ case is first studied, consisting of two different uniform cascaded systems in series, with an obvious, uncontrolled, impedance mismatch where they meet. The paper shows how boundary actuator control systems can be designed to establish, and robustly maintain, apparently pure travelling waves of constant amplitude in either the first or the second uniform section, in each case with an appropriate, partial, standing wave pattern in the other section. Then a more general non-uniform case is studied. A definition of a ¿pure travelling wave¿ in non-uniform systems is proposed. Curiously, it does not imply constant amplitude motion. It does however yield maximum power transfer between boundary actuators. The definition, and its implementation in a control system, involves extending the notions of ¿pure¿ travelling waves, of standing waves, and of input and output impedances of sources and loads, when applied to non-uniform lumped systems. Practical, robust control strategies are presented for all cases. The Second Joint International Conference on Multibody System Dynamics; Stuttgart, Germany, May 29 - June 1, 2012 2012-05-01T00:00:00Z http://hdl.handle.net/10197/4004 A new approach to modal analysis of uniform chain systems O'Connor, William; McKeown, David A new method is presented to determine the mode shapes and frequencies of uniform systems consisting of chains of masses and springs of arbitrary number with arbitrary boundary conditions. Instead of the classical eigenproblem approach, the system is analysed in terms of circulating waves and associated phase lags. The phasor conditions for the establishment of standing waves determine the vibration modes. The conditions fully specify their shapes and frequencies, and lead to simple, explicit expressions for the components of the modal vectors and the associated natural frequencies. In addition, the form of the phasor diagrams of the modes gives insight into the modal behaviour. The orthogonality of mode shapes also readily emerges. Examples are presented for different boundary conditions. Although not presented, it is possible to extend the approach to non-uniform lumped systems and to forced frequency responses. 2008-04-08T00:00:00Z http://hdl.handle.net/10197/3744 Evaluation of microwave plasma oxidation treatments for the fabrication of photoactive un-doped and carbon-doped TiO2 coatings Dang, Binh H.Q.; Rahman, Mahfujur; MacElroy, J. M. Don; Dowling, Denis P. The photoactivity of both un-doped and carbon-doped titanium dioxide (TiO2) coatings has been widely reported. In this paper, the use of a microwave plasma as a novel oxidation treatment for the fabrication of these coatings is evaluated. The photoactivity performance of the microwave plasma-formed coatings is benchmarked against those fabricated through air furnace oxidation as well as those deposited using reactive magnetron sputtering. The un-doped and carbon-doped TiO2 coatings were prepared respectively by microwave plasma-oxidizing titanium metal sheets and sputter deposited titanium carbide thin films. The resulting oxides were characterized using XPS, XRD, FEG-SEM, and optical profilometry. The oxide layer thicknesses achieved over the 15 to 45 minute oxidation times were in the range of 0.15 to 3.44 µm. These coatings were considerably thicker than those obtained by air furnace oxidation. The microwave plasma-formed oxides also exhibited significantly higher surface roughness values compared with the magnetron-sputtered coatings. The photoactivity performance of both un-doped and carbon-doped coatings was assessed using photocurrent density measurements. Comparing the un-doped TiO2 coatings, it was observed that those obtained using the microwave plasma oxidation route yielded photocurrent density measurements that were 4.3 times higher than the TiO2 coatings of the same thickness that were deposited by sputtering. The microwave plasma-oxidized titanium carbide coatings did not perform as well as the un-doped TiO2 probably due to the presence of un-oxidized carbide in the coatings, which reduced their photoactivity. 2012-05-25T00:00:00Z http://hdl.handle.net/10197/3531 Quantitative MRI analysis of brain volume changes due to controlled cortical impact Colgan, Niall C.; Cronin, Michelle M.; Gobbo, Olivier L.; O'Mara, S. M. (Shane M.); O'Connor, William; Gilchrist, M. D. More than 85% of reported brain traumas are classified clinically as “mild” using GCS; qualitative MRI findings are scarce and provide little correspondence to clinical symptoms. Our goal, therefore, was to establish in-vivo sequellae of traumatic brain injury following lower and higher levels of impact to the frontal lobe using quantitative MRI analysis and a mechanical model of penetrating impact injury. To investigate time-based morphological and physiological changes of living tissue requires a surrogate for the human central nervous system. The present model for TBI was a systematically varied and controlled cortical impact on deeply-anaesthetized Sprague Dawley rats designed to mimic different injury severities. Whole-brain MRI scans were performed on each rat prior to either a lower or a higher level of impact and then at hourly intervals for five hours post-impact. Both brain volume and specific anatomical structures were segmented from MR images for inter-subject comparisons post-registration. Animals subjected to lower and higher impact levels exhibited elevated intracranial pressure (ICP) in the low compensatory reserve (i.e., nearly exhausted) and terminal disturbance (i.e., exhausted) ranges, respectively. There was a statistically-significant drop in cerebrospinal fluid of 35% in the lower impacts and 65% in the higher impacts at Hr5 in comparison to the sham control. There was a corresponding increase in corpus callosum volume starting from Hr1 of 60-110% and 30-40% following the lower and higher impact levels, respectively. A statistically significant change in the abnormal tissue from Hr2 to Hr5 was observed for both impact levels, with greater significance for higher impacts. Furthermore, a statistically significant difference between the lower impacts and the sham controls occurred at Hr3. These results are statistically substantiated by a fluctuation in the physical size of the corpus callosum, a decrease in the volume of CSF, and elevated levels of atrophy in the cerebral cortex. 2010-07-26T00:00:00Z http://hdl.handle.net/10197/3201 Economic and technical criteria for designing future off-shore HVDC grids Bell, Keith; Cirio, Diego; Denis, Anne-Marie; He, Lina; Liu, Chen-Ching; Migliavacca, Gianluigi; Moreira, Carlos; Panciatici, Patrick In the scope of a recently launched European Research Project, a team of experts from public laboratories and TSO is in charge of defining the concepts and methodological approaches to design and analyse the technical and economic feasibility of future HVDC grids. This work aims at identifying, assessing and comparing several possible HVDC network topologies, with appropriate control and protection schemes, able to collect wind energy on large areas, transmit it at the best points to the AC grid and provide the necessary ancillary services for optimising the DC / AC interconnection in normal and disturbed conditions. The methodology adopted for the study and presented in this paper will focus on three main items: 1. identify and assess the economic drivers for the development of off-shore HVDC networks 2. identify the requirements for an optimal operation of the AC / DC interconnected power systems under normal and emergency conditions 3. conceptualise the coordinated control / command and protection plans for HVDC networks This paper gives a comprehensive view of the issues and tasks to be addressed during the run of the project. Paper presented at the IEEE PES Conference on Innovative Smart Grid Technologies Europe October 11-13, 2010, Lindholmen Science Park, Gothenburg, Sweden 2010-10-11T00:00:00Z http://hdl.handle.net/10197/3190 Modelling the quasi-static behaviour of bituminous material using a cohesive zone model Tabakovic, Amir; Karac, Aleksandar; Ivankovic, Alojz; Gibney, Amanda; McNally, Ciaran; Gilchrist, M. D. This paper investigates the applicability of a cohesive zone model for simulating the performance of bituminous material subjected to quasistatic loading. The Dugdale traction law was implemented within a finite volume code in order to simulate the binder course mortar material response when subjected to indirect tensile loading. A uniaxial tensile test and a threepoint bend test were employed to determine initial stress-strain curves at different test rates and the cohesive zone parameters (specifically, fracture energy and cohesive strength). Numerical results agree well with the experimental data up to the peak load and onset of fracture, demonstrating the value of the cohesive zone modelling technique in successfully predicting fracture initiation and maximum material strength. 2010-09-01T00:00:00Z http://hdl.handle.net/10197/3189 The influence of recycled asphalt pavement on the fatigue performance of asphalt concrete base courses Tabakovic, Amir; Gibney, Amanda; McNally, Ciaran; Gilchrist, M. D. This paper presents the physical properties of Recycled Asphalt Pavement (RAP) and its influence on the mechanical performance of a binder course asphalt pavement mix. A series of binder course mixes were designed containing varying percentages of RAP. A mix made from only virgin material was selected as the control mix for the investigation. The effect of introducing RAP into the binder course mix was evaluated through a series of laboratory tests including the Marshall test, the indirect tensile stiffness modulus Test, the indirect tensile fatigue test and the water sensitivity test. A Circular Wheel Track (CWT) was developed in order to study the dynamic effects of a rolling wheel travelling over an asphalt pavement. The CWT was commissioned within a temperature controlled room along with a customised data acquisition system. The system involves the testing of rectangular slabs and allows for the investigation of dynamic tensile strain. The laboratory tests have shown that the introduction of RAP to the binder course mix resulted in an improvement in all mechanical properties. In particular, it was found that the mix containing up to 30% RAP, displayed improved fatigue resistance relative to the control mix manufactured from virgin materials. 2010-06-01T00:00:00Z http://hdl.handle.net/10197/2896 Conversion of amorphous TiO2 coatings into their crystalline form using a novel microwave plasma treatment Dang, Binh H.Q.; Rahman, Mahfujur; MacElroy, J. M. Don; Dowling, Denis P. Crystalline titanium dioxide (TiO2) coatings have been widely used in photo-electrochemical solar cell applications. In this study, TiO2 and carbon-doped TiO2 coatings were deposited onto unheated titanium and silicon wafer substrates using a DC closed-field magnetron sputtering system. The resultant coatings had an amorphous structure and a post-deposition heat treatment is required to convert this amorphous structure into the photoactive crystalline phase(s) of TiO2. This study investigates the use of a microwave plasma heat treatment as a means of achieving this crystalline conversion. The treatment involved placing the sputtered coatings into a 2.45 GHz microwave-induced nitrogen plasma where they were heated to approximately 550°C. It was observed that for treatment times as short as 1 minute, the 0.25-µm thick coatings were converted into the anatase crystalline phase of TiO2. The coatings were further transformed into the rutile crystalline phase after treatments at higher temperatures. The doping of TiO2 with carbon was found to result in a reduction in this phase transformation temperature, with higher level of doping (up to 5.8% in this study) leading to lower anatase-to-rutile transition temperature. The photoactivity performance of both doped and un-doped coatings heat-treated using both furnace and microwave plasma was compared. The carbon-doped TiO2 exhibited a 29% increase in photocurrent density compared to that observed for the un-doped coating. Comparing carbon-doped coatings heat-treated using the furnace and microwave plasma, it was observed that the latter yielded a 19% increase in photocurrent density. This enhanced performance may be correlated to the differences in the coatings’ surface morphology and band gap energy, both of which influence the coatings’ photoabsorption efficiency. 2011-07-25T00:00:00Z http://hdl.handle.net/10197/2885 Wave-like modelling of cascaded, lumped, flexible systems with an arbitrarily moving boundary O'Connor, William This paper considers cascaded, lumped, flexible systems, which may be short and non-uniform, which are driven by an arbitrarily moving boundary. Such systems exhibit vaguely wavelike behaviour yet defy classical wave analysis. The paper proposes novel ways to analyse and model such systems in terms of waves. It presents two new wave models for non-uniform systems, one series and one shunt, defining their component wave transfer functions, and thereby providing a way to define, identify and measure component waves. Features of the models are compared. The series and shunt configurations are mutually consistent and can be combined into a single composite wave model. The models are exact, but elements within them remain arbitrary to some degree, implying slight differences in the wave decomposition of the system. Some good model choices are proposed and explored. Wave speed and wave impedance are briefly considered, as are ways to measure component waves. Implications are discussed. 2011-06-20T00:00:00Z http://hdl.handle.net/10197/2730 Application of a novel microwave plasma treatment for the sintering of nickel oxide coatings for use in dye-sensitized solar cells Awais, Muhammad; Rahman, Mahfujur; MacElroy, J. M. Don; Dini, Danilo; Vos, Johannes G.; Dowling, Denis P. In this study the use of microwave plasma sintering of nickel oxide (NiOx) particles for use as p-type photoelectrode coatings in dye-sensitized solar cells (DSSCs) is investigated. NiOx was chosen as the photocathode for this application due to its stability, wide band gap and p-type nature. For high light conversion efficiency DSSCs require a mesoporous structure exhibiting a high surface area. This can be achieved by sintering particles of NiOx onto a conductive substrate. In this study the use of both 2.45 GHz microwave plasma and conventional furnace sintering were compared for the sintering of the NiOx particles. Coatings 1 to 2.5 μm thick were obtained from the sintered particles (mean particle size of 50 nm) on 3 mm thick fluorine-doped tin oxide (FTO) coated glass substrates. Both the furnace and microwave plasma sintering treatments were carried out at ~ 450 °C over a 5 minute period. Dye sensitization was carried out using Erythrosin B and the UV-vis absorption spectra of the NiOx coatings were compared. A 44% increase in the level of dye adsorption was obtained for the microwave plasma sintered samples as compared to that obtained through furnace treatments. While the photovoltaic performance of the DSSC fabricated using the microwave plasma treated NiOx coatings exhibited a tenfold increase in the conversion efficiency in comparison to the furnace treated samples. This enhanced performance was associated with the difference in the mesoporous structure of the sintered NiOx coatings. 2011-07-25T00:00:00Z http://hdl.handle.net/10197/2454 Deposition and characterization of NiOx coatings by magnetron sputtering for application in dye-sensitized solar cells Awais, Muhammad; Rahman, Mahfujur; MacElroy, J. M. Don; Coburn, Nadia; Dini, Danilo; Vos, Johannes G.; Dowling, Denis P. Nickel oxide (NiOx) due to its p-type nature has considerable potential as a photocathodic material in energy conversion devices such as dye-sensitized solar cells (DSSCs). However,NiOx has not been extensively used for this application mainly because of low light harvesting efficiency due to limited dye loading on the coatings. In this study NiOx coatings were deposited using the dc- magnetron sputtering technique from a nickel target in an argon/oxygen plasma. One of the advantages of magnetron sputtering is the ability to control coating properties such as mechanical performance and chemical stoichiometry. It is anticipated that by enhancing the interconnectivity between NiOx particles and by optimizing surface roughness, it may be possible to enhance dye adsorption and increase its ability to absorb visible light. NiOx coatings were deposited onto both silicon wafer and indium tin oxide (ITO) covered glass substrates. The influence of deposition parameters such as pressure, nickel target current and substrate bias voltage were correlated with the coating properties of surface roughness, thickness, crystallographic structure and surface energy. This evaluation was carried out using optical profilometry, spectroscopic ellipsometry, XRD and contact angle measurements respectively. It was observed that deposited coating morphology and roughness were significantly influenced by the deposition parameters. For example increasing the deposition pressure from 0.20 to 0.40 Pa led to an increase in surface roughness (Ra) from 1.6 to 3 nm. Associated with this increase in roughness the surface energy increased from 36 to 61 mN/mm. The NiOx coatings were spectrally sensitized with Rucomplex dye containing -COOH groups as anchoring moieties. The dye adsorptions on NiOx coatings, deposited on ITO substrates, were investigated in transmission mode using UV-vis spectroscopy in the range of 400 – 800 nm. It was observed that for the coatings with the highest surface energy, there was an increase of up to 60 % in the level of dye adsorption. The electroactivity of the NiOx thin films deposited on Ni substrate at 0.4 Pa has been verified through the occurrence of redox processes of reduction and lithium intercalation within the oxide film. 2010-05-01T00:00:00Z http://hdl.handle.net/10197/2328 The influence of recycled asphalt pavement on 20mm binder course mix performance Tabakovic, Amir; Gibney, Amanda; Gilchrist, M. D.; McNally, Ciaran This paper presents the results of ongoing research on the mechanical performance of a 20mm binder course asphalt pavement mix incorporating recycled asphalt pavement (RAP). A series of binder course mixes were designed containing varying percentages of RAP. A mix made only from virgin material was selected as the control mix for the investigation. The effect of introducing RAP into the binder course mix was evaluated through a series of laboratory tests including the Marshall Test, Indirect Tensile Stiffness Modulus Test, Indirect Tensile Fatigue Test and Water Sensitivity Test. A Circular Wheel Track (CWT) was developed in order to study the dynamic effects of a rolling wheel travelling over an asphalt pavement. The CWT was commissioned within a temperature controlled room along with a customised Data Acquisition (DAQ) system. The system involves the testing of rectangular slabs and allows for the investigation of the dynamic tensile strain. The dynamic tensile strain is digitally recorded and the loading effect assessed. The laboratory tests have shown that the introduction of RAP to the binder course mix resulted in an improvement in all mechanical properties. This was also observed in the dynamic tensile strain test. Paper presented at the 3rd National Symposium on Bridge and Infrastructure Research in Ireland, Dublin, 2006 and at ICAP (International Conference on Asphalt Pavements) conference Quebec, Canada, 2006 2006-10-01T00:00:00Z http://hdl.handle.net/10197/2311 Fatigue resistance of bituminous layers incorporating reclaimed asphalt pavement Tabakovic, Amir; Gibney, Amanda; Gilchrist, M. D.; McNally, Ciaran This paper presents the results of an investigation into the fatigue performance of a 20mm Binder Course Asphalt Pavement Mix incorporating Recycled Asphalt Pavement (RAP). For the study, a series of binder course mixes were designed containing varying percentages of RAP. A mix made only from virgin material, was selected as the control mix for the investigation. A Circular Wheel Tracker (CWT) was developed in order to simulate the dynamic loading conditions of a rolling wheel and to study the initiation and growth of fatigue cracks in an asphalt pavement mix. The CWT was commissioned within a temperature-controlled room with a customised data acquisition system. The test specimens were subjected to dynamic loading in the CWT and the dynamic strain on the underside of the slab was monitored throughout the test. A digital image processing technique was also used to measure the crack area and crack length at the underside of the test specimen. Parallel to this a separate testing programme was undertaken, whereby the fatigue resistance of bituminous mixtures incorporating same RAP contents was assessed using the indirect tensile fatigue test as described in BS DD ABF:1997. The results from these parallel strands are compared, and the performance of the various mixes incorporating RAP is assessed. 5th International Conference on Research & Practical Applications Using Wastes & Secondary Materials in Pavement Engineering, Liverpool, U. K., 22nd and 23rd February 2006 2006-02-01T00:00:00Z http://hdl.handle.net/10197/2303 Development of a combined micromechanics & damage mechanics model for the design of asphalt pavements Tabakovic, Amir; McNally, Ciaran; Sorelli, L. G.; Gibney, Amanda; Gilchrist, M. D. Asphalt is a complex, heterogeneous material that is composed of differently sized aggregates, binder and air voids: in other words, it is a particulate reinforced composite. The focus of the present work is to investigate the structural effectiveness of this material composition following the introduction of recycled asphalt pavement (RAP) into the mix. The virgin mortar mix (i.e., matrix) consists of an asphalt binder, sand and crushed rock fines (CRF), while the RAP-containing mix additionally includes fine aggregates ranging in size from fine dust (< 75μm diameter) up to small particles (< 3.35mm diameter). The stress distribution throughout such a material and the resulting mechanical response is strongly related to the interaction between the mix constituents. Previous work has shown that this performance is less influenced by the presence of larger aggregate than it is by the mortar composition and it is for this reason that the present work attempts to model damage evolution in various mortar mixes. Joint Conference of the Association for Computational Mechanics in Engineering (UK) and the Irish Society for Scientific and Engineering Computation, 19-20 April 2006, QUB, Belfast 2006-04-01T00:00:00Z http://hdl.handle.net/10197/2275 Development of a recycled polymer modified binder for use in stone mastic asphalt Casey, Donnchadh; McNally, Ciaran; Gibney, Amanda; Gilchrist, M. D. The number of commercial vehicles using Irish roads has increased considerably in recent years, leading to higher demands being placed on pavement materials and increased use of polymer modified bitumens. This has also coincided with significant changes in Governmental policy which has produced large increases in Irish recycling rates. Improved recycling levels are set to provide Ireland with a new challenge: to find potential uses for the large quantities of recycled polymer that are becoming available. Towards this end, the potential of developing a recycled polymer modified binder was investigated. The polymers most commonly recycled in Ireland were identified and sourced from industry. Fundamental bitumen tests were conducted to assess the effect of the recycled polymer and a mixing methodology developed. It was found that the addition of 4% recycled HDPE into a pen grade binder produced the most promising results, and the mixing process was then optimised with respect to mixing parameters and binder additives. A developmental recycled binder was produced and compared in performance tests to binders currently used in road construction practice. Results obtained from wheel track and fatigue tests show that although the binder does not deliver equivalent performance levels to a proprietary polymer modified binder, it does out-perform traditional binders used in stone mastic asphalt. Recommendations are offered on the further development of the recycled polymer modified binder to achieve the standards currently required. 2008-08-01T00:00:00Z