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Welding as high productive joining method is widely employed in automotive, aerospace and shipbuilding industries. In practice, welding distortion brings about undesirable effects on production accuracy, appearance and strength of welded components. Thus, in order to increase the productivity and decrease the cost of the product, prediction and analysis of welding deformation are key factors in industrial context. Distortion of a structure can be measured experimentally; whilst in case of large or complex structures it is expensive and also time consuming. Numerical analysis is then performed using finite element method (FEM) that reduces the cost; however, in case of large welded structure and considering extremely nonlinear mechanical behavior of welding the computational expense incurred which must be cut through elastic analysis. In this sense, the residual plastic strain, namely inherent strain as a source of residual stress and welding distortion should be analyzed. The purpose of this study is to detail the prediction procedure of deformation in welded structure by elastic finite element modeling using inherent strain method. As a matter of fact inherent strain as an inelastic permanent strain or residual plastic strain, which exists in vicinity of fusion zone, is responsible for welding deformation and residual stresses. Comparing with elastic plastic analysis, inherent strain method has less computing time however the state of welding may be not investigated in detail; Furthermore, appropriate assumption of inherent strain region and determining the accurate values of inherent deformations in each typical joint bring about some limitations. On the other hand, just the elastic modulus and Poisson’s ratio at room temperature is used in elastic FEM, and there is no need for temperature material properties. So, at the present time, thermal elastic plastic finite element method can be used to predict residual stresses and welding deformations in small or medium structures but for large components elastic FEM is promising method.

Extreme value behavior of a moored semi-submersible vessel is investigated. There is a need for alternative methods other than the Rayleigh peak model when investigating non-Gaussian processes. In this context the Rayleigh peak model will generally underestimate extreme values. Four methods are investigated in this study with data from 1000 seeds. They are; construction of an empirical cumulative distribution function, mean of maximas, a LF/WF spectral partition and peak distribution tail tting. In turn six peak distributions are investigated. It was found that global motions are more sensitive than point accelerations to estimation errors, and the more accurate methods should be applied to global motions. A tted Weibull peak distribution proved to be the most conservative for both MPM value and 90 th percentile estimations. It was also found that a mean of 10 maxima was a good estimation of a MPM value. Longer seeds than three hours are recommended in order to include higher maxima and lower minima. Further comparison studies are recommended.

The focus of today’s automotive industry is to reduce emissions and fuel consumption of all vehicles. Concentrating on the truck industry, the last 20 years have focused largely on cutting emissions of particulate matter and nitrogen oxides. For the future, attention will be focused on fuel consumption and emissions of carbon dioxide. Waste heat recovery appears to be a very promising concept for fuel economy on long haul heavy duty Diesel trucks. After a general introduction on the concept of waste heat recovery and the Rankine cycle, this thesis work shows how to model and calibrate a cooling system circuit for a heavy duty Diesel engine equipped with a waste heat recovery system. Then an overview of the current transmission systems that are suitable to transfer energy from the waste heat recovery expander to the engine shaft is presented. For all transmission architectures, input speed range, speed ratio range, transmission efficiency as well as weight and size are detailed and compared to each other. Finally, these systems are modeled and integrated to a complete vehicle Simulink simulation platform and simulations are run on two highway driving cycles. Resulting average recovered powers and fuel consumptions are compared and the analysis finally shows that a gear train transmission has the best performance for this kind of driving cycle.

It is the objective of this thesis project to understand the physics behind the different modes of bird flight and to do numerical two dimensional simulations of pure plunging, pure pitching and combined pitch-plunging motion of an aerofoil. First, the different physical models used to understand the generation of thrust are explained. Then the numerical model used for the simulation is explained briefly. Then the results and analysis of the numerical simulations are presented.

The student project Elba at KTH started in 2011 and is a project where a battery driven prototype car is developed. The vehicle competes in Eco Shell Marathon in Rotterdam, Holland. In this competition the vehicle that travels a certain distance including several starts and stops with the lowest energy consumption wins. To minimize the consumption is therefore very important, which requires knowledge of the vehicles energy losses. A vehicle's energy losses depends on several factors and can be divided into the powertrain efficiency and the driving resistance. The driving resistance can then be divided in to rolling and air resistance, if smaller losses like vibrations are ignored. This report seeks to develop, describe, and evaluate a couple of methods to measure these two parameters on behalf of KTH Transport Labs. The methods chosen are based on a literature study of earlier developed methods and a dialog with the clients. The measuring methods have been adapted to a low budget and simple measuring conditions such as a garage or a tarmac road. The methods are based on either pulling and free rolling, or only free rolling. The traveled distance, speed, acceleration and driving force are logged during the measurements. The measurements have been done at two different locations, in a garage at Stockholmsmässan in Älvjö and on a parking lot by Teknikringen 8 at KTH. To measure the different parameters an encoder, accelerometer and force transducer has been used. To computing the driving resistance a graphical user interface was developed in Matlab. The developed measuring methods compute both the rolling and air resistance coefficients which creates great demands on the environment for the measurement. This could make it hard to find a satisfying test track. The unreasonable results from the coast-down, were Elba were rolling freely, at Teknikringen 8 shows the difficulties when the measurement is unprotected from the wind. With small resistance, as in an energy efficient vehicle like Elba, the measurement is more sensitive to disturbances. This causes the need of preprocessing data before the calculations are done. The final finding is that a combination of the described methods is preferable. A measurement to calculate the rolling resistance coefficient is made by pulling the car. Then a coast-down is made according to any of the two suggested methods. This allows the cast down to be done on a different road surface than the one that the rolling resistance coefficient is calculated for. This means that the air resistance for instance could be measured indoors where there is no wind. The purpose of this project was to develop a method to measure rolling and air resistance for Elba or similar vehicles. Due to technical issues and poor measuring conditions no reliable values of the resistance have been resolved with the developed and chosen methods. If the measurements would be repeated with better equipment and better conditions, a good result would be possible to get. / Studentprojektet Elba på KTH startade 2011 och är ett projekt där en batteridriven prototypbil avsedd att tävla i Eco Shell Marathon i Rotterdam, Holland tas fram. I denna tävling vinner det fordon som på utsatt tid kör en viss sträcka inkluderande flera starter och stopp med en så låg energiförbrukning som möjligt. Att minimera energikonsumtionen är alltså mycket viktigt vilket ställer krav på kunskap om fordonets förluster. Ett fordons energiförluster beror av flera faktorer såsom drivlinans verkningsgrad och färdmotståndet. Om mindre förluster så som vibrationer försummas kan färdmotståndet i sin tur delas upp i rull- och luftmotstånd. Denna rapport syftar till att ta fram, beskriva och utvärdera några metoder för att mäta dessa två parametrar på uppdrag av KTH Transport Labs. Metoderna som har valts att studeras är baserade på en litteraturstudie av tidigare framtagna metoder och samtal med beställaren. Valen utgår från en låg budget och enkla testmiljöer så som garage eller asfaltsväg. Metoderna består av att antingen dra och frirulla, eller enbart frirulla fordonet. Tillryggalagd sträcka, hastighet, acceleration och drivande kraft loggas under mätningen. Mätningar har genomförts vid två olika platser, i ett garage vid Stockholmsmässan i Älvsjö och på en parkering vid Teknikringen 8 på KTH. För att mäta de olika storheterna har en pulsgivare, accelerometer och kraftgivare använts. För behandling av data och beräkning av färdmotstånden har ett grafiskt användargränssnitt tagits fram i Matlab. De framtagna mätmetoderna beräknar både rull- och luftmotståndskoefficienten vilket ställer stora krav på mätmiljön. Detta kan göra det svårt att hitta en tillfredställande testbana. De orimliga resultaten från utrullningen, där Elba frirullas, vid Teknikringen 8 visar på svårigheterna då mätningen görs utan skydd från vinden. Med små färdmotstånd, som hos ett energisnålt fordon som Elba, blir beräkningarna känsligare för störningar. Detta medför att viss förbehandling av data krävs innan beräkningarna kan genomföras. Slutsatsen är att en kombination av de beskrivna metoderna är att föredra. Ett dragtest görs separat för att bestämma rullmotståndskoefficienten. Sedan appliceras någon av de två metoderna för att beräkna luftmotståndskoefficienten. Detta gör att utrullningen inte behöver ske på det underlag som rullmotståndskoefficienten söks för. Det innebär att luftmotståndet är möjligt att mätas inomhus där det är vindstilla. Syftet med detta arbete var att ta fram en metod för beräkning av rull- och luftmotstånd hos Elba eller andra liknande fordon. På grund av tekniska problem och bristfälliga mätmiljöer har inga tillförlitliga värden för motstånden tagits fram med de utvecklade och valda metoderna. Om mätningarna skulle återupprepas med bättre utrustning och med bättre förhållanden skulle dock trovärdiga resultat kunna uppnås.

This thesis evaluates a proprietary interface developed by Scania that connects a third party developed autonomy solution to the electrical system of a Scania truck. The autonomy solution is developed for a mining application. While evaluating the interface the focus of the thesis narrows down to how to make the interface scalable and future proof. The content of this thesis is mainly based upon interviews and internal Scania documentation. In summary, the two main conclusions that could be drawn from this evaluation study are, that the interface needs to support a larger amount of requests from an external control to support that the interface is applicable in many areas. Secondly the idea of a modular electrical system must be carried on to autonomous applications as well and interface logic must be separated from core functionality of the electrical system.

What are the differences between two wheel steering and four wheel steering? The aim of this project is to compare these two in terms of advantages gained from four wheel steering. A simulation is conducted on ADAMS Cars platform based on the RCV (Research Concept Vehicle) model, developed at KTH in Stockholm.

Today's high oil prices and more stringent environmental requirements have led to that manufacturers of mobile construction equipment try to make their products more energy efficient. With this in mind a project about hybridization of hydraulic systems has been formed. The purpose of this project was to analyze the savings that can be achieved by hybridization of hydraulic systems. A reach stacker truck (Kalmar DRD450-80S4XS) were simulated in some load cases with conventional hydraulic systems and with three types of hybridized hydraulic systems. Different parts of the hydraulic systems were also analyzed separately. The analysis has shown that significant energy savings can be achieved by hybridizing hydraulic systems. The analysis showed that between 9-30% energy savings could be achieved by hybridizing the truck's various subsystems. / Med dagens höga oljepriser och samhällets allt strängare miljökrav, stävar tillverkare av mobila entreprenadmaskiner efter att energieffektivisera sina produkter. Med detta i tanke formades ett projekt om att regenerera hydraulisk energi på entreprenadmaskiner. Syftet med detta projekt var att analysera vilka besparingar som kan åstakommas genom att hydraulsystemet på entrprenadmaskiner hybridiseras. En reachstacker truck (Kalmar DRD450-80S4XS) simulerades i några lastfall med konventionellt hydraulsystem samt med tre typer av hybridiserade hydraulsystem. Olika delar av de hydrauliska systemen analyserades även var för sig. Analysen har visat att stora energibesparingar kan åstakommas genom att hybridisera hydraulsystem. Den genomförda analysen visade på att mellan 9-30% energibesparing kunde uppnås genom att hybridisera truckens olika delsystem.