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  • Public defence: 2017-08-25 10:00 F3, Stockholm
    Wu, Qiong
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Biofoams and Biocomposites based on Wheat Gluten Proteins2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Novel uses of wheat gluten (WG) proteins, obtained e.g. as a coproduct from bio-ethanol production, are presented in this thesis. A flame-retardant foam was prepared via in-situ polymerization of hydrolyzed tetraethyl orthosilicate (TEOS) in a denatured WG matrix (Paper I). The TEOS formed a well-dispersed silica phase in the walls of the foam. With silica contents ≥ 6.7 wt%, the foams showed excellent fire resistance. An aspect of the bio-based foams was their high sensitivity to fungi and bacterial growth. This was addressed in Paper II using a natural antimicrobial agent Lanasol. In the same paper, a swelling of 32 times its initial weight in water was observed for the pristine WG foam and both capillary effects and cell wall absorption contributed to the high uptake. In Paper III, conductive and flexible foams were obtained using carbon-based nanofillers and plasticizer. It was found that the electrical resistance of the carbon nanotubes and carbon black filled foams were strain-independent, which makes them suitable for applications in electromagnetic shielding (EMI) and electrostatic discharge protection (ESD). Paper IV describes a ‘water-welding’ method where larger pieces of WG foams were made by wetting the sides of the smaller cubes before being assembled together. The flexural strength of welded foams was ca. 7 times higher than that of the same size WG foam prepared in one piece. The technique provides a strategy for using freeze-dried WG foams in applications where larger foams are required.

    Despite the versatile functionalities of the WG-based materials, the mechanical properties are often limited due to the brittleness of the dry solid WG. WG/flax composites were developed for improved mechanical properties of WG (Paper V). The results revealed that WG, reinforced with 19 wt% flax fibres, had a strength that was ca. 8 times higher than that of the pure WG matrix. Furthermore, the crack-resistance was also significantly improved in the presence of the flax.

  • Public defence: 2017-08-25 10:00 Lecture Hall T1, Huddinge
    Raghothama, Jayanth
    KTH, School of Technology and Health (STH), Health Systems Engineering, Health Care Logistics.
    Integrating Computational and Participatory Simulations for Design in Complex Systems2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The understanding and conceptualization of cities and its constituent systems such as transportation and healthcare as open and complex is shifting the debates around the technical and communicative rationales of planning. Viewing cities in a holistic manner presents methodological challenges, where our understanding of complexity is applied in a tangible fashion to planning processes. Bridging the two rationales in the tools and methodologies of planning is necessary for the emergence of a 'non-linear rationality' of planning, one that accounts for and is premised upon complexity. Simulations representing complex systems provide evidence and support for planning, and have the potential to serve as an interface between the more abstract and political decision making and the material city systems.

    Moving beyond current planning methods, this thesis explores the role of simulations in planning. Recognizing the need for holistic representations, the thesis integrates multiple disparate simulations into a holistic whole achieving complex representations of systems. These representations are then applied and studied in an interactive environment to address planning problems in different contexts. The thesis contributes an approach towards the development of complex representations of systems; improvements on participatory methods to integrate computational simulations; a nuanced understanding of the relative value of simulation constructs; technologies and frameworks that facilitate the easy development of integrated simulations that can support participatory planning processes.

    The thesis develops contributions through experiments which involved problems and stakeholders from real world systems. The approach towards development of integrated simulations is realized in an open source framework. The framework creates computationally efficient, scalable and interactive simulations of complex systems, which used in a participatory manner delivers tangible plans and designs.

  • Public defence: 2017-08-31 10:00 F3, Stockholm
    Carrander, Claes
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Magnetizing Currents in Power Transformers: Measurements, Simulations, and Diagnostic Methods2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This thesis demonstrates a method for transformer core diagnostics. The method uses the no-load current of the transformer as an indicator, and gives different characteristic signatures for different types of faults or defects. Using the no-load current for the diagnostic gives high sensitivity. The method is therefore able to detect defects that are too small to have an impact on the losses. In addition to different types of fault, the method can in some cases also distinguish between faults in different locations within the core.

    Both single-phase and three-phase transformers can be diagnosed using this method, and the measurements can be easily performed at any facility capable of measuring the no-load loss. There are, however, some phenomena that occur in large transformers, and in transformers with high rated voltages. Examples include capacitive resonance and magnetic remanence. This thesis proposes and demonstrates techniques for compensating for these phenomena. With these compensating techniques, the repeatability of the measurements is high. It is shown that units with the same core steel tend to have very similar no-load behavior.

    The diagnostics can then be performed either by comparing the transformer to another unit, or to simulations. The thesis presents one possible simulation method, and demonstrates the agreement with measurements.

    This topological simulation method includes both the electric circuit and an accurate model of the magnetic hysteresis. It is therefore also suitable for other, related, studies in addition to core diagnostics. Possible subjects include ferroresonance, inrush, DC magnetization of transformers, and transformer core optimization.

    The thesis also demonstrates that, for three-phase transformers, it is possible to compare the phases to each other. This technique makes it possible to diagnose a transformer even without a previous measurement to compare to, and without the data required to make a simulation.

  • Public defence: 2017-09-01 10:00 F3, Stockholm
    Everitt, Niklas
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Module identification in dynamic networks: parametric and empirical Bayes methods2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The purpose of system identification is to construct mathematical models of dynamical system from experimental data. With the current trend of dynamical systems encountered in engineering growing ever more complex, an important task is to efficiently build models of these systems. Modelling the complete dynamics of these systems is in general not possible or even desired. However, often, these systems can be modelled as simpler linear systems interconnected in a dynamic network. Then, the task of estimating the whole network or a subset of the network can be broken down into subproblems of estimating one simple system, called module, embedded within the dynamic network.

    The prediction error method (PEM) is a benchmark in parametric system identification. The main advantage with PEM is that for Gaussian noise, it corresponds to the so called maximum likelihood (ML) estimator and is asymptotically efficient. One drawback is that the cost function is in general nonconvex and a gradient based search over the parameters has to be carried out, rendering a good starting point crucial. Therefore, other methods such as subspace or instrumental variable methods are required to initialize the search. In this thesis, an alternative method, called model order reduction Steiglitz-McBride (MORSM) is proposed. As MORSM is also motivated by ML arguments, it may also be used on its own and will in some cases provide asymptotically efficient estimates. The method is computationally attractive since it is composed of a sequence of least squares steps. It also treats the part of the network of no direct interest nonparametrically, simplifying model order selection for the user.

    A different approach is taken in the second proposed method to identify a module embedded in a dynamic network. Here, the impulse response of the part of the network of no direct interest is modelled as a realization of a Gaussian process. The mean and covariance of the Gaussian process is parameterized by a set of parameters called hyperparameters that needs to be estimated together with the parameters of the module of interest. Using an empirical Bayes approach, all parameters are estimated by maximizing the marginal likelihood of the data. The maximization is carried out by using an iterative expectation/conditional-maximization scheme, which alternates so called expectation steps with a series of conditional-maximization steps. When only the module input and output sensors are used, the expectation step admits an analytical expression. The conditional-maximization steps reduces to solving smaller optimization problems, which either admit a closed form solution, or can be efficiently solved by using gradient descent strategies. Therefore, the overall optimization turns out computationally efficient. Using markov chain monte carlo techniques, the method is extended to incorporate additional sensors.

    Apart from the choice of identification method, the set of chosen signals to use in the identification will determine the covariance of the estimated modules. To chose these signals, well known expressions for the covariance matrix could, together with signal constraints, be formulated as an optimization problem and solved. However, this approach does neither tell us why a certain choice of signals is optimal nor what will happen if some properties change. The expressions developed in this part of the thesis have a different flavor in that they aim to reformulate the covariance expressions into a form amenable for interpretation. These expressions illustrate how different properties of the identification problem affects the achievable accuracy. In particular, how the power of the input and noise signals, as well as model structure, affect the covariance.

  • Public defence: 2017-09-01 10:00 Sal B, Kista
    Elahipanah, Hossein
    KTH, School of Information and Communication Technology (ICT), Electronics.
    Design Optimization and Realization of 4H-SiC Bipolar Junction Transistors2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    4H-SiC-based bipolar junction transistors (BJTs) are attractive devices for high-voltage and high-temperature operations due to their high current capability, low specific on-resistance, and process simplicity. To extend the potential of SiC BJTs to power electronic industrial applications, it is essential to realize high-efficient devices with high-current and low-loss by a reliable and wafer-scale fabrication process. In this thesis, we focus on the improvement of the 4H-SiC BJT performance, including the device optimization and process development.

    To optimize the 4H-SiC BJT design, a comprehensive study in terms of cell geometries, device scaling, and device layout is performed. The hexagon-cell geometry shows 42% higher current density and 21% lower specific on-resistance at a given maximum current gain compared to the interdigitated finger design. Also, a layout design, called intertwined, is used for 100% usage of the conducting area. A higher current is achieved by saving the inactive portion of the conducting area. Different multi-step etched edge termination techniques with an efficiency of >92% are realized.

    Regarding the process development, an improved surface passivation is used to reduce the surface recombination and improve the maximum current gain of 4H-SiC BJTs. Moreover, wafer-scale lift-off-free processes for the n- and p-Ohmic contact technologies to 4H-SiC are successfully developed. Both Ohmic metal technologies are based on a self-aligned Ni-silicide (Ni-SALICIDE) process.

    Regarding the device characterization, a maximum current gain of 40, a specific on-resistance of 20 mΩ·cm2, and a maximum breakdown voltage of 5.85 kV for the 4H-SiC BJTs are measured. By employing the enhanced surface passivation, a maximum current gain of 139 and a specific on-resistance of 579 mΩ·cm2 at the current density of 89 A/cm2 for the 15-kV class BJTs are obtained. Moreover, low-voltage 4H-SiC lateral BJTs and Darlington pair with output current of 1−15 A for high-temperature operations up to 500 °C were fabricated.

    This thesis focuses on the improvement of the 4H-SiC BJT performance in terms of the device optimization and process development for high-voltage and high-temperature applications. The epilayer design and the device structure and topology are optimized to realize high-efficient BJTs. Also, wafer-scale fabrication process steps are developed to enable realization of high-current devices for the real applications.

  • Public defence: 2017-09-08 09:00 Sal F3, Stockholm
    Timmer, Brian J.J.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Metals in Dynamic Chemistry: Selection & Catalysis2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the adaptation to the oxidative environment on earth, metals played a crucial role for the evolution of life. The presence of metals also allowed access to advanced functions due to their unique coordination sphere and reactivity. This thesis focused on exploiting these unique properties for further development of the field of dynamic chemistry – a field in which adaptation plays a central role as well.

    The first part of the thesis aimed to create a better understanding of multivalent effects in carbohydrate-lectin interactions. By reversible ligand coordination to zinc ions one of the nanoplatforms, the Borromean rings, could be selectively obtained. After carbohydrate functionalization the binding events were monitored by quartz crystal microbalance technology and compared to glycosylated fullerenes and dodecaamide cages. Overall, this investigation indicated that statistical and polyelectrolyte effects play a considerable role in the observed multivalent effects.

    The second part of the thesis aimed to design and synthesize a new catalyst for application in aqueous olefin metathesis. This afforded a ruthenium based catalyst that was applied in the self- and cross-metathesis of highly functionalized substrates, such as carbohydrates. In addition, it was shown that addition of a small amount of acetic acid prevented undesired double bond isomerization.

    The last part of the thesis aimed to explore new methods to discover transition metal catalysts. Dynamic exchange of directing groups generated a pool of potential substrates for C-H activation. Combining this pool of substrates with a pool of potential catalysts resulted in amplification of a reactive substrate/metal combination. By iterative deconvolution in combination with mass spectrometry, this “intermediate” could be identified from the mixture, proving applicability of this alternative approach to catalyst discovery.

  • Public defence: 2017-09-08 10:00 M3, Stockholm
    Topel, Monika
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Improving Concentrating Solar Power Plant Performance through Steam Turbine Flexibility2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The amount of incoming solar energy to earth is greater than any other source. Among existing technologies to harness solar energy there is concentrating solar power (CSP). One advantage of CSP is that is dispatchable, meaning that it can provide power even when the sun is not shining. However, CSP is undergoing challenges which hinder its development such as operating variabilities caused by the fluctuations of the sun or the fact that these systems are not yet cost competitive with respect to other technologies.  

    One way of improving the performance of CSP plants (CSPPs) is by increasing their operational flexibility, specifically their capability for fast starts. In this way it is possible for the CSPP to harness the solar energy as soon as possible, thus producing more energy and increasing its profitability. Over 90% of CSPPs use a steam turbine to generate electricity. Steam turbines are not currently designed with the flexibility required by the CSP application. Steam turbine start-up is limited by thermal stress and differential expansion. If not carefully controlled, these phenomena either consume lifetime or even result in machine failure.

    The aim of this work was to understand the improvement potential of steam turbine start-up and quantify this in terms of CSPP performance indicators. For this, a thermo-mechanical steam turbine model was developed and validated. The model was then used to analyze potential improvements and thermal constraints to steam turbine start-up operation. Furthermore, a CSP plant techno-economic model was developed including steam turbine details. This modeling approach including two levels of detail allowed for the particularities of the component to be included within the dynamics of the plant and thus be able to connect the perspectives of the equipment manufacturer with those of the plant operator. Reductions of up to 11.4% in the cost of electricity were found in the studies carried out.

  • Public defence: 2017-09-08 13:00 F3, Stockholm
    Heyman, Susanna
    KTH, School of Computer Science and Communication (CSC), Media Technology and Interaction Design, MID.
    Visualizing Financial Futures2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Research on financial decision aids, systems designed to help people make financial decisions, is sparse. Previous research has often focused on the theoretical soundness of the advice that the systems provide.The original contribution of this doctoral thesis is a set of empirical studies of how non-expert people understand the advice provided by financial decision aids. Since every piece of advice must be interpreted by a receiver, the accuracy of the advice can be corrupted along the way if the receiver does not understand complicated terminology, probabilistic reasoning, or abstract concepts.The design concept resulting from the studies visualizes a unique combination of short-term and long-term variables that are usually treated as separate and not interacting with each other; loans and amortizations, insurance, retirement saving, and consumption. The aim is to visualize the consequences of different decisions and possible adverse events in terms of their effect on the user’s future consumption, rather than abstract numbers detached from the user’s lived experience.The design concept was tested and evaluated by personal finance experts and professional financial advisors, as well as students and people without financial education, who represented the target users of the system. Results indicate that the system has a learning curve, but that once users understand how to read the graph, they find it more informative than conventional financial planning tools.

  • Public defence: 2017-09-08 14:00 Kollegiesalen, Stockholm
    Ebadat, Afrooz
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Experiment Design for Closed-loop System Identification with Applications in Model Predictive Control and Occupancy Estimation2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The objective of this thesis is to develop algorithms for application-oriented input design. This procedure takes the model application into account when designing experiments for system identification.

    This thesis is divided into two parts. The first part considers the theory of application-oriented input design, with special attention to Model Predictive Control (MPC). We start by studying how to find a convex approximation of the set of models that result in acceptable control performance using analytical methods when controllers with no closed-form control law, for e.g., MPC are employed. The application-oriented input design is formulated in time domain to enable handling of signals constraints. The framework is extended to closed-loop systems where two cases are considered i.e., when the plant is controlled by a general but known controller and for the case of MPC. To this end, an external stationary signal is designed via graph theory. Different sources of uncertainty in application-oriented input design are investigated and a robust application-oriented input design framework is proposed.

    The second part of this thesis is devoted to the problem of estimating the number of occupants based on the information available to HVAC systems in buildings. The occupancy estimation is first formulated as a two-tier problem. In the first tier, the room dynamic is identified using temporary measurements of occupancy. In the second tier, the identified model is employed to formulate the problem as a fused-lasso problem. The proposed method is further developed to be used as a multi-room estimator using a physics-based model. However, since it is not always possible to collect measurements of occupancy, we proceed by proposing a blind identification algorithm which estimates the room dynamic and occupancy, simultaneously. Finally, the application-oriented input design framework is employed to collect data that is informative enough for occupancy estimation purposes.

  • Public defence: 2017-09-12 13:00 F3, Stockholm
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH.
    Novel organic sensitizers and hole transport materials for efficient solid-state photovoltaic devices2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    State-of-art solid-state photovoltaic devices, such as solid-state dye sensitized solar cells (ssDSSCs) and perovskite solar cells have attracted significant attention due to their high efficiency and potential low-cost manufacture. However, there are still challenges that limit the application up-scaling..

     

    One important factor that limits the efficiency of ssDSSCs is associated with the sensitizers. In this thesis, we have developed several organic sensitizers for highly efficient and stable ssDSSCs. The compatibility between sensitizers and hole transport materials has also been investigated. Novel blue colored sensitizers have been studied with aesthetic applications in mind. By co-sensitization using two complementary sensitizing dyes, the efficiency of ssDSSCs can be increased significantly..

     

    For both PSCs and ssDSSCs, the hole transport materials (HTMs) represent one of the crucial factors for efficient charge collection as well as future cost of manufacturing. Here, we have studied organic triphenylamine based oligomers as HTMs for both ssDSSCs and PSCs. The influence of the molecular structure of the HTM building blocks on the photovoltaic performance has been studied in detail. In order to minimizing the cost of fabrication of photovoltaic devices, we have also developed sulfur-based cross-linked polymers as HTMs to replace the well-known, expensive HTM Spiro-OMeTAD. The cross-linked polymeric sulfur material work well in both ssDSSCs and PSCs with efficiencies around 2% and 10%, respectively. These results will provides important insights for the future design of inexpensive and efficient solid state photovoltaic devices.

    The full text will be freely available from 2018-09-12 15:44
  • Public defence: 2017-09-13 13:15 F3, Stockholm
    Li, Zuxing
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Privacy-by-Design for Cyber-Physical Systems2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    It is envisioned that future cyber-physical systems will provide a more convenient living and working environment. However, such systems need inevitably to collect and process privacy-sensitive information. That means the benefits come with potential privacy leakage risks. Nowadays, this privacy issue receives more attention as a legal requirement of the EU General Data Protection Regulation. In this thesis, privacy-by-design approaches are studied where privacy enhancement is realized through taking privacy into account in the physical layer design. This work focuses in particular on cyber-physical systems namely sensor networks and smart grids. Physical-layer performance and privacy leakage risk are assessed by hypothesis testing measures.

    First, a sensor network in the presence of an informed eavesdropper is considered. Extended from the traditional hypothesis testing problems, novel privacy-preserving distributed hypothesis testing problems are formulated. The optimality of deterministic likelihood-based test is discussed. It is shown that the optimality of deterministic likelihood-based test does not always hold for an intercepted remote decision maker and an optimal randomized decision strategy is completely characterized by the privacy-preserving condition. These characteristics are helpful to simplify the person-by-person optimization algorithms to design optimal privacy-preserving hypothesis testing networks.

    Smart meter privacy becomes a significant issue in the development of smart grid technology. An innovative scheme is to exploit renewable energy supplies or an energy storage at a consumer to manipulate meter readings from actual energy demands to enhance the privacy. Based on proposed asymptotic hypothesis testing measures of privacy leakage, it is shown that the optimal privacy-preserving performance can be characterized by a Kullback-Leibler divergence rate or a Chernoff information rate in the presence of renewable energy supplies. When an energy storage is used, its finite capacity introduces memory in the smart meter system. It is shown that the design of an optimal energy management policy can be cast to a belief state Markov decision process framework.

  • Public defence: 2017-09-19 14:59 F3, Stockholm
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Material migration in tokamaks: Erosion-deposition patterns and transport processes2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Controlled thermonuclear fusion may become an attractive future electrical power source. The most promising of all fusion machine concepts is called a tokamak. The fuel, a plasma made of deuterium and tritium, must be confined to enable the fusion process. It is also necessary to protect the wall of tokamaks from erosion by the hot plasma. To increase wall lifetime, the high-Z metal tungsten is foreseen as wall material in future fusion devices due to its very high melting point. This thesis focuses on the following consequences of plasma impact on a high-Z wall: (i) erosion, transport and deposition of high-Z wall materials; (ii) fuel retention in tokamak walls; (iii) long term effects of plasma impact on structural machine parts; (iv) dust production in tokamaks.

    An extensive study of wall components has been conducted with ion beam analysis after the final shutdown of the TEXTOR tokamak. This unique possibility offered by the shutdown combined with a tracer experiment led to the largest study of high-Z metal migration and fuel retention ever conducted. The most important results are:

     

    - transport is greatly affected by drifts and flows in the plasma edge;

    - stepwise transport along wall surfaces takes place mainly in the toroidal direction;

    - fuel retention is highest on slightly retracted wall elements;

    - fuel retention is highly inhomogeneous.

     

    A broad study on structural parts of a tokamak has been conducted on the TEXTOR liner. The plasma impact does neither degrade mechanical properties nor lead to fuel diffusion into the bulk after 26 years of duty time. Peeling deposition layers on the liner retain fuel in the order of 1g and represent a dust source. Only small amounts of dust are found in TEXTOR with overall low deuterium content. Security risks in future fusion devices due to dust explosions or fuel retention in dust are hence of lesser concern.

  • Public defence: 2017-09-22 14:00 F3, Stockholm
    Lokatt, Mikaela
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    On Aerodynamic and Aeroelastic Modeling for Aircraft Design2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work presented in this thesis was performed with the aim of developing improved prediction methods for aerodynamic and aeroelastic analysis to be used in aircraft design. The first part of the thesis concerns the development of a viscous-inviscid interaction model for steady aerodynamic predictions. Since an inviscid, potential flow, model already is available, the main focus is on the development of a viscous model consisting of a three-dimensional integral boundary layer model. The performance of the viscous-inviscid interaction model is evaluated and it is found that the accuracy of the predictions as well as the computational cost appear to be acceptable for the intended application. The presented work also includes an experimental study aimed at analyzing steady and unsteady aerodynamic characteristics of a laminar flow wing model. An enhanced understanding of these characteristics is presumed to be useful for the development of improved aerodynamic prediction models. A combination of nearly linear as well as clearly nonlinear aerodynamic variations are observed in the steady as well as in the unsteady experimental results and it is discussed how these may relate to boundary layer properties as well as to aeroelastic stability characteristics. Aeroelastic considerations are receiving additional attention in the thesis, as a method for prediction of how flutter characteristics are affected by modeling uncertainties is part of the presented material. The analysis method provides an efficient alternative for obtaining increased information about, as well as enhanced understanding of, aeroelastic stability characteristics.

  • Public defence: 2017-09-29 10:00 Gladan, Stockholm
    Alemani, Mattia
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Particle emissions from car brakes: The influence of contact conditions on the pad-to-rotor interface2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Due to their adverse health effects emissions have been regulated for over three decades. Brake wear particulate matter is the most important non-exhaust source, however current knowledge is mainly limited to observational studies. This thesis aims to investigate relations between the brake system contact conditions and the related emissions on a model scale; validate the results on a component level; and understand to what extent they are significant on a full-scale.

    Paper A investigates the influence of nominal contact pressure on a model scale. Results show that higher pressure corresponds to higher emissions

    Paper B investigates the influence of the nominal contact pressure, for different friction materials, on a model scale. A temperature threshold, responsible for a relevant emission increase, is identified.

    Paper C investigates particle characteristics and wear mechanisms for different nominal contact pressures, on a model scale. Results show an enhanced tribo-layer at higher pressure levels.

    Paper D investigates the influence of brake system conditions on emissions, on a model scale. Results show that frictional power is the most important parameter. A transition temperature independent of the contact condition is identified.

    Paper E investigates similarities occurring on a component scale and a model scale in terms of emissions. Results show a promising correlation, and the possibility of using a pin-on-disc tribometer for R&D activities.

    Paper F investigates analogies occurring on a component scale and a model scale, in terms of friction performance, fictional surface and chemical composition. Results show similar phenomena occurring for the two test stands.

    Paper G analyses real brake system working conditions in a urban environment defining, by means of an inertia dyno bench, the related emissions. Results reveal emission factors compliant to EURO6 and EURO2 regulations, in terms of number and mass, respectively.

    The full text will be freely available from 2017-09-08 15:43