Traffic is a major source of green house gases. The transport field stands for 32 % of the energy consumption and 28 % of the total CO2 emissions, where road transports alone causes 84 % of these figures. The energy consumed by a car travelling at constant speed, is due to engine inefficiency, internal friction, and the energy needed to overcome resisting forces such as aerodynamic drag and rolling resistance. Rolling resistance plays a rather large role when it comes to fuel economy. An improvement in rolling resistance of 10 % can yield fuel consumption improvements ranging from 0.5 to 1.5 % for passenger cars and light trucks and 1.5 to 3 % for heavy trucks. The objective of this thesis is to estimate the power consumption in the tyres. To do this a car tyre is modelled with waveguide finite elements. A non-linear contact model is used to calculate the contact forces as the tyre is rolling on a rough road. The contact forces combined with the response of the tyre is used to estimate the input power to the tyre structure, which determines a significant part of the rolling resistance. This is the first rolling resistance model based on physical principles and design data. The elements used in the waveguide finite elements tyre model are derived and validated. The motion of the tyre belt and side wall is described with quadratic anisotropic curved deep shell elements that includes pre-stress and the motion of the tread on top of the belt by curved quadratic, Lagrange type, homogenous, isotropic two dimensional solid elements. The tyre model accounts for: the curvature, the geometry of the cross-section, the pre-stress due to inflation pressure, the anisotropic material properties and the rigid body properties of the rim and is based on data provided by Goodyear. To validate the tyre model, mobility measurements and an experimental modal analysis have been made. The model agrees very well with point mobility measurements up to roughly 250 Hz. The eigenfrequency prediction is within five percent for most of the identified modes. The estimated damping is a bit too low especially for the anti-symmetric modes. The non-proportional damping used in the model is based on an ad hoc curve fitting procedure against measured mobilities. The non-linear contact force prediction, made by the division of applied acoustics, Chalmers University of Technology takes the tyre, the road texture and the tread pattern into account. The dissipated power is calculated through the injected power and the power dissipated within each element. It is shown that a rough road leads to more dissipation than a smooth road. A demonstration on real existing motor ways, for which rolling resistance measurements also have been made, show the potential of the method. The damping is very important for the rolling resistance prediction. The damping properties of the tyremodel are therefore updated based on measurement, equivalent structure modelling and viscoelastic material models. This updated model is slightly better at the point mobility prediction and is far better at predicting the damping level of the identified modes from the experimental modal analysis. / QC 20100722

Vibration induced High Cycle Fatigue (HCF) is a major consideration in designing gas turbines. Indeed, the Gas Turbine manufacturer must demonstrate that the vibration level of the turbomachinery blading is acceptably low, usually by using an engine strain gauge test. If the test shows unacceptable vibration levels then a redesign is required which adds cost and time to the engine development programme. It is highly desirable, therefore to develop a capability which can predict the vibration level of the blade to ensure that it will be robust. The High-Pressure Turbine is of particular interest because of the harshness of the environment in which it operates (high mechanical speed and high air temperatures and pressures) so friction dampers are routinely introduced to control the vibration level. The friction dampers can introduce a degree of non-linearity into the structure which affects not only the vibration amplitude, but also the resonant frequency. The resonant frequency, amplitude, damper behaviour and aerodynamic forcing are all inter-related such that they must be considered as a single system. This thesis describes the development of two new approaches to predict the vibration behaviour of a High-Pressure Turbine blade including the effect of friction dampers. The first utilises existing prediction tools for modelling of the fluid, the structure and the friction behaviour, but uses a novel method for coupling the various aspects together. This approach is based on modelling an ‘engine acceleration’ across a wide speed range and prescribing the variation of all the relevant parameters with shaft speed. For example, both the excitation force on the blade and the centrifugal load of the damper vary strongly with rotor speed so these effects must be included in the analysis. The second approach extends the first approach by using a new iterative ‘resonance tracking’ methodology in which the aerodynamic boundary conditions are adjusted based on the shaft speed at resonance until convergence is reached. Both methodologies calculate the resonant frequency, amplitude and operating condition of each mode of interest as an output of the analysis. The engine acceleration methodology has been investigated in detail and has been validated against several High-Pressure Turbine cases. It has been found to be reliable: the amplitude predictions were in broad agreement with the available engine strain gauge results and the frequency shift introduced by the damper was in very good agreement. The methodology captures some important features of the physical system such as (a) the amplitude dependence of the damper, (b) the sudden drop in frequency when approaching the second flap resonance because the damper starts to slide, and (c) the effect of the damper on the ratio between stress and tip displacement. One rather surprising result was that in certain cases, where the forcing level was low, the damper increased the blade response because it moved the resonance to a higher shaft speed where the forcing level was larger. The main advantage of the method is its speed, which allows optimisation of key parameters within design timescales. The resonance tracking methodology has been compared directly with the engine acceleration approach on one of the test cases and it produced very similar results. Convergence was achieved quickly, in two or three iterations for the chosen test case, mainly because the blade surface pressure distribution was consistent across a broad speed range. The method showed that the first torsion resonance was more sensitive to aerodynamic conditions than the second flap mode, and may offer an explanation for the scatter seen in engine test results. The approach offers the advantage that it is more generally applicable, because it can deal with cases where the pressure distribution is sensitive to shaft speed, but it can only converge to a single mode and requires significantly more computational effort. The methodologies have been used to explore vibration reduction strategies such as wake shaping, damper optimisation and defining acceptance limits for the orientation of the single crystal material used in turbine manufacture. Overall these provided almost an order of magnitude reduction in blade response. / QC 20100824

Engine research and development is to a large extent driven by the quest of lowering exhaust emissions and fuel consumption. The combination of low emissions and low fuel consumption is not the simultaneous characteristic of the world’s primary engine concepts, the diesel and the spark-ignited (SI) engine. However, such a concept do exist, it is commonly called Homogeneous Charge Compression Ignition (HCCI). The HCCI combustion concept is when a premixed air and fuel mixture is ignited by the heat of compression. The operation is unthrottled, like the diesel engine, which is advantageous for its efficiency. The premixed air / fuel mixture preclude soot formation, like the SI engine. An exclusive feature of HCCI combustion is extremely low NOX production due to low-temperature combustion. The mixture preparation of the typical gasoline HCCI engine is similar to the SI engine, via port-injection, which results in a well homogenized mixture. Port injection of diesel fuel is however very difficult since the environment is too cold for the fuel to vaporise. A better alternative is therefore direct-injection. However, injection must occur in a way where a homogeneous mixture is formed, while contact of the liquid fuel with cold walls is avoided. There are many approaches to direct-injected mixture formation. This thesis focuses on exploring the concept of impinging sprays; its characteristics and its impact on combustion and emissions. The work comprises unique information regarding impinging sprays, as well as results regarding engine performance. It is concluded that impinging sprays are well suited for early direct-injection. / QC 20100824

Forging ingots are hot worked to consolidate structural imperfections and refine the microstructure. Possible imperfections are segregations, porosities, cracks, and inclusions. In this thesis, techniques and methods for the characterisation of behaviour and properties of ingots and forgings. The root causes for quality issues in open-die forgings are shown to be numerous. Ingot structure in cast tool steel was analyzed, and the main imperfections were centre macrosegregation, and mid radius A-segregations.For overheated steel forgings and low reductions after reheating, a high ultrasonic attenuation and low Charpy-V toughness was found. It could be related to the coarse grain structure found. Only a high forging reduction after reheating will break down the coarse structure. Shorter reheating times and lower forging temperatures gave higher toughness and lower ultrasonic attenuation. Some reduction in toughness was also found from the inclusion field from the bottom of the ingot. Accurate attenuation measurements require a lathe turned surface, complicating in-between-measurements in heat treatment sequences. But on carefully surface prepared forgings, attenuation measurement can be used to determine the success of grain refinement in the heat treatment. A new method for ultrasonic macrography of cast ingot samples is presented. In addition, a new method for hot compression testing of cylindrical metal samples is presented. / QC 20100809

Mechatronics development requires the close collaboration of various specialist teams and engineering disciplines. Developers from the different disciplines use domain-specific tools to specify and analyse the system of interest. This leads to different views of the system, each targeting a specific audience, using that audience’s familiar language, and concentrating on that audience’s concerns. Successful system development requires that the views of all developers produced by the different tools are well integrated into a whole, reducing any risks of inconsistencies and conflicts in the design information specified. This thesis discusses techniques of managing and integrating the views from various disciplines, taking better advantage of multidisciplinary, model-based, development. A Model Data Management (MDM) platform that generically manages models from the various domain-specific tools used in development is presented. The platform is viewed as a unification of the management functionalities typically provided by the discipline-specific PDM and SCM systems. The unification is achieved by unifying the kind of objects it manages – models. View integration is considered as an integral functionality of this platform. In demonstrating the platform’s feasibility, a generic version management functionality of models is implemented. In addition, model integration is investigated for the allocation of system functions onto the implementing hardware architecture. The proposed approach promotes the independent development of the views, allowing developers from each discipline to work concurrently, yet ensuring the completeness, correctness and analysis of any inter-view design decisions made. The prototype MDM platform builds on existing technologies from each of the mechanical and software disciplines. The proposed MDM system is built based on a configurable PDM system, given its maturity and ability to manage model contents appropriately. At the same time, the version control functionality borrows ideas from the fine-grained version control algorithms in the software discipline. The platform is argued to be feasible given the move towards model-based development in software engineering, bringing the discipline’s needs closer to those of the hardware discipline. This leads the way for an easier and more effective integrated management platform satisfying the needs of both disciplines using a common set of mechanisms. / QC 20110124

Electroacoustic technology has in many ways revolutionised the wireless telecommunication industry. The IC compatible fabrication technique of thin film electroacoustic devices has so far provided a considerable increase in device performance and reduction in size. At the moment, new areas where this technology can be of use is under investigation. In particular, thin film bulk acoustic wave resonators are promising candidates for biochemical and gravimetric sensor applications. For bulk acoustic waves, the thesis addresses a number of aspects in the design, fabrication, characterisation, and integration of thin film electroacoustic devices. The object of the studies conducted in the thesis has been to improve on design and thereby optimise the performance of the device to fit a particular application of interest. For high frequency and high power applications, a conceptually new design of the solidly mounted resonator has been investigated. A 1 GHz plate wave resonator with a much higher Q factor than its surface acoustic counterpart have also been fabricated. A multi-chip-module 2 GHz microwave oscillator featuring a monolithically integrated solidly mounted resonator and a flip chip transistor have been fabricated and characterised with a phase noise of -125 dBc/Hz at 100 kHz. For sensor applications, the fabrication of shear mode solidly mounted resonators featuring c-axis inclined AlN films has been studied. A process for the bonding of a microfluidic system on top of the resonator has been realised. Further, the effect of conductive liquids on the resonator performance has been investigated.For surface acoustic wave devices, acoustic manipulation of particles in microfluidic channels has been studied. Two functional devices have been fabricated by bonding piezoelectric substrates to glass or fused silica superstrates. By generating an interface acoustic wave, that propagates along the bonded interface, manipulation of sub-micrometer particles was realised. / wisenet

Biogas mainly consists of methane and carbon dioxide, where methane is theenergy-rich gas, and is naturally created when organic matter breaks down in absenceof oxygen, also known as anaerobic digestion. A biogas plant re-creates the anaerobicconditions inside a digester where the organic substrate is fed into and digests toproduce biogas. The gas is then used to produce energy by combustion and can beseen as a completely renewable fuel.Today, energy from biogas is used primarily by major stakeholders such asmunicipalities and thus the plants become very large with high investment- andconstruction costs. There are currently few small plants in Sweden, even though thepotential for agriculture and medium-sized to smaller farms to become self-sufficientin terms of electricity and heat is great. Farms have a natural stock of digestibleorganic material in form of manure or crops for example, which are constantlyavailable. A reason that only a few small plants exists are the large investment costs.A study focusing on the actors who supply these smaller plants today was made withthe intention to find out where the large investment costs are and what techniquesare most profitable and efficient to use. The survey was conducted through field visits,interviews and contact by phone and internet with active companies and peoplefamiliar with the modern production of biogas.The survey was compiled and the various techniques and concepts were presented,evaluated and discussed to give the client a good basis for further development ofsmall-scale biogas plants.The investigation revealed that there are no barriers for biogas production in smallerfacilities, given that the same conditions in terms of temperature, acidity and nutrientis created just like in the larger facilities. It also showed that active heating and stirringof the substrate in the digester is of utmost importance to have a functioning processand maximum gas exchange.

The royal warship Vasa sank on its maiden voyage outside Stockholm and was salvaged more than 300 years later in 1961. Nowadays the vessel lies in its eponymous museum in Stockholm on a dry dock. However, it was determined that the ship cannot handle its own weight in a satisfactory manner with the current support system. Measurements during the past ten years have ascertained that the upper structure components of the hull are slowly deforming, mostly due to creep behavior.   A new support system for the ship needs to be designed in the near future and therefore, the mechanical behavior of its structural members and the stresses they are subjected to have to be determined. Factors that complicate a stress analysis include both inhomogeneity of the oak’s mechanical properties and limited opportunities for experimental testing. Furthermore, contamination, microbial degradation and preservation agents have significantly changed the integrity of the oak.   In this project a section of the Vasa’s bottom structure is studied through Finite Element Analysis in order to determine the stresses and deformations originated by the support system and to have a better understanding of these effects on the ship’s structure. Due to the considerable deterioration of the oak, especially on the external structural members, several assumptions are considered in order to perform analytical calculations to determine appropriate material properties for the FE-Models.    After performing the computational simulations, the obtained results indicate that the bottom structure exhibits sufficient mechanical integrity to endure the stresses generated by the support system. Even by assuming the possibility of several damaged structural connections, only a minor difference of the effects of the reaction forces on the structure members was determined.   The thesis work ends with further conclusions from the performed analysis and suggested future work.

No description available.

<p>Mechatronics development requires the close collaboration of various specialist teams and engineering disciplines. Developers from the different disciplines use domain-specific tools to specify and analyse the system of interest. This leads to different views of the system, each targeting a specific audience, using that audience’s familiar language, and concentrating on that audience’s concerns. Successful system development requires that the views of all developers produced by the different tools are well integrated into a whole, reducing any risks of inconsistencies and conflicts in the design information specified.</p><p>This thesis discusses techniques of managing and integrating the views from various disciplines, taking better advantage of multidisciplinary, model-based, development. A Model Data Management (MDM) platform that generically manages models from the various domain-specific tools used in development is presented. The platform is viewed as a unification of the management functionalities typically provided by the discipline-specific PDM and SCM systems. The unification is achieved by unifying the kind of objects it manages – models. View integration is considered as an integral functionality of this platform.</p><p>In demonstrating the platform’s feasibility, a generic version management functionality of models is implemented. In addition, model integration is investigated for the allocation of system functions onto the implementing hardware architecture. The proposed approach promotes the independent development of the views, allowing developers from each discipline to work concurrently, yet ensuring the completeness, correctness and analysis of any inter-view design decisions made.</p><p>The prototype MDM platform builds on existing technologies from each of the mechanical and software disciplines. The proposed MDM system is built based on a configurable PDM system, given its maturity and ability to manage model contents appropriately. At the same time, the version control functionality borrows ideas from the fine-grained version control algorithms in the software discipline.</p><p>The platform is argued to be feasible given the move towards model-based development in software engineering, bringing the discipline’s needs closer to those of the hardware discipline. This leads the way for an easier and more effective integrated management platform satisfying the needs of both disciplines using a common set of mechanisms.</p>