Globalization is reaching the furthest corners of the world and with globalizations comes a rising demand on transportation. In shipping; a significant cost both to the ship owners and the environment are the fossil fuels used for propulsion, even a small reduction in the wave resistance can bring considerable reductions both in operating costs and emissions for such ships. When designing a ship it is important to be able to make fast and accurate predictions of its resistance so that more efficient hull forms can be selected early in the design process. A panel method based on potential flow is a fast scheme to determine the wave resistance and is therefore suitable to be used early on in the design process. Here it is shown that potential flow can be improved by including Rayleigh damping, added viscous effects that will make the flow dissipative. Dissipative Green functions are employed in the proposed technique with the resulting velocity potential determined from a combination of a source distribution and a modified distribution of vortices on submerged 2D bodies. NACA hydrofoils, Joukowski hydrofoils and cylinders are used to test the model. The pressure distribution is more in line with experimental results than previous numerical methods without added viscosity for the NACA hydrofoils. The surface profile has very good comparison with existing numerical results for a NACA hydrofoil in subcritical speeds. However the results are very poor for the Joukowski hydrofoil. There is therefore reason to develop this method further in both 2D and 3D.

Detta examensarbete är en konceptuell fartygsprojektering av en ny serie fartyg åt Sjöräddningssällskapet. Rapporten presenterar ett förslag till en ny sjöräddningsbåt som kan ersätta två äldre fartygstyper, i storleksordningen tio meter, och det behov som täcks av dem. Fartygets huvuduppgifter fastställs vara bogsering och sjuktransport och det opererar mestadels i skyddade vatten under sommarhalvåret. Examensarbetet är handlett av Thore Hagman, Sjöräddningssällskapet och examinator Karl Garme, KTH,Marina System. Mycket arbete har lagts på att skapa ett kostnadseffektivt förslag vilket gav att en befintlig skrovform anpassades för att passa den kravställning som togs fram tillsammans med Sjöräddningssällskapets ledning och räddningsbesättningar. Huvuddata: Loa 9,95 m Boa 4,2 m T 0,65 m Deplacement 5,65 ton fullastat Motorer 2x350 hk utombordare Fart 42 knop Bunker 1,5 m2 bensin Räckvidd +280 Nm i 35 knop Fartyget har ett fristående däckshus som, om det dimensioneras och byggs vattentätt, gör fartyget självrätande. Däckshuset rymmer fyra besättningsmedlemmar och tre passagerare alternativt en patient på bår. Båten har utrustning för brandbekämpning, länspumpning, bogsering, sjuktransport, ”On-scenecoordination”-kommunikation och räddning av nödställda i vattnet.

Rubber is a highly complicated material. Its properties are strongly dependent of temperature, preload, frequency, amplitude and filling materials. In order to have better knowledge about how rubber reacts for these different parameters, a number of different papers that treats these parameters have been reviewed. Main focus is on dynamic properties of carbon-black filled rubber. Mechanical models of rubber isolator with different kinds of possible solution have been suggested. A basic mathematical equation is derived to estimate the static and dynamic stiffness of a rubber isolator depending on the preload for a geometry that is commonly used by Atlas Copco Rock Drills AB. Tests of a rubber isolator with the same geometry is also conducted to validate the model. It is shown that the model corresponds very well to measurement data.

To enhance the drivability and increase safety a major part of Scania’svehicles is fitted with a retarder. The retarder is a complementary brake system that assists the vehicles mechanical brakes. When running a retarder some oil leakage can occur. The main source to the leakage is oil sump ventilation but there is also some contribution from the solenoid valve block that controls the retarder. Test results from the test rig shows that with rather simple methods the oil leakage in form of oil mist can be captured. The efficiency of for instance concept 1 with half the volume and a chicane interior was as high as 99 to 100 %. For the concept 2 with the expanded metal filter the efficiency was in the order of 96 to 100 %. From testing it has also become clear that there is a problem to feed the oil back into the oil sump. Initial tests shows that the retarder is rather sensitive regarding the placing of the feedback channel. It is considered that the best option is to only use the feedback channel that enters the internal drain of the retarder. Measurements show that the airflow in the tube from the accumulator could reach velocities up to 67 m/s. It is considered that the best solution is to have two separate chambers, one for the accumulator and one for the oil sump ventilation, the safety valve and the proportion valve. The reason for this is that the combination of oil in a chamber together with high airflow from the accumulator is disastrous and the retarder leaks far worse compared to original. The conclusion is therefore that it is important to separate air from the accumulator from places where oil can occur. Tests also revealed that the size of an external volume is not of any great importance when it comes to colleting oil. There was no significant difference in between of using a volume of 0.64 l or 0.19 l. However regarding overfilling it is favorable to have a larger volume since this increases the retarder’s capability to withstand oil leakage when it is overfilled.

In a world of fierce competition that is the reality for heavy truck manufacturers, it is important to optimize every step of production to the greatest extent. The Swedish truck manufacturer SCANIA early adopted such ideas and has put great efforts to implement a concept called lean production. As a part of the company’s strive for continuous improvement, all parts of the value adding chain shall be as efficient as possible.  Previously this work has been focused inside the SCANIA organization but as demands on production volume and profit margin increases, focus turns outside the factory premises. A bodywork is fitted as a last step in the completion of many trucks. This is done by external companies called bodybuilders, outside the control of the factory. In this thesis, the bodybuilder induced waste is addressed from a global perspective. The report is entirely based on interviews with people inside SCANIA, SCANIA’s Swedish business unit, bodybuilders in both Sweden and Poland and a Swedish employer’s organization. Through these interviews, the difficulties surrounding the subject have been mapped from different perspectives. As a complement to the interviews, a program that calculates the annual waste related to shortened chassis frames has been developed. The main waste inducing problem areas found in this thesis is: -        Poor communication between seller and bodybuilder before specifying and ordering the chassis. -        Poor communication between factory and bodybuilder regarding existing chassis preparations. -        A high degree of customer involvement in the bodybuilder process on the Swedish market. -        High price sensitivity on the Polish market makes chassis specified without preparations more attractive. -        Highly diverse customer demands on the Swedish market. -        Insufficient ordering tools to meet the customer demands of individually customized vehicles. -        Discrepancies between the global focus at factory and the local nature of the market on which the sellers exist. The costs related to shortened chassis frames alone is estimated to cost SCANIA 5 000 000 SEK annually in terms of reduced chassis frame waste and decreased costs for bound investments when chassis are standing at bodybuilders. In order to go from today’s annual production of 70 000 vehicles to the long-term goal of 150 000 vehicles/year, it will be crucial to reduce waste throughout the whole production chain. This will require better prepared vehicles from factory, better ordering software for the sellers and less rigid customer behaviour on certain markets. The increased communication between seller, bodybuilder and factory will be necessary and could be implemented through cooperation between selected bodybuilders and sellers in a preferred program.

No description available.

Crosswind stability of rail vehicles has been a research area for several decades,mainly motivated by vehicle overturning accidents and higher speeds, but in recenttimes also by issues of lower energy consumption and track maintenance costsdemanding lower vehicle weights. During everyday operation, rail vehicles are subjectedto large lateral influences from track irregularities, track curves and crosswind,leading to large suspension deflections and increased crosswind sensitivity.Also unsteady crosswind like gusts calls for attention. Simulations of possible vehicleoverturning are necessary, but need to take large deflections and high shear inthe suspension into account. If delivering reasonable results, simulations representan important tool for overturning prediction of the vehicle. In the present work, multibody simulations of a high-speed vehicle at large lateralinfluences from track curves and track irregularities have been carried out, using ahalf-vehicle model in 2D and a model of a whole vehicle in 3D. The vehicle modelsalso include different suspension models. Corresponding field measurements ofthe relative lateral and vertical deflections in the secondary suspension have beenperformed on a fast train and used for validation of the multibody simulations,resulting in good agreement between measurements and simulations. The 3D vehicle model was further used to study the vehicle response to unsteadycrosswind during curve negotiation where aerodynamic loads obtained by unsteadyComputational Fluid Dynamics, namely Detached Eddy Simulations, representingthree types of gusts were used. In addition, the method of Quasi Transient GustModelling was evaluated in terms of overturning risk. Strong lateral and roll responsesof the vehicle and influences of the gust duration and the relative differencebetween mean and maximum wind speed were observed. Further, variations of suspensionand mass properties of the vehicle were performed to study the influenceon crosswind sensitivity. The position of the centre of mass of the carbody and thelateral bumpstop clearance showed significant influence on the crosswind stability.

Michelin develops and manufactures tires. To check their tire, different tires tests are used. During the testing process of agricultural tires, some endurance tests are performed on a circular test track where a convoy, made of a truck pulling two single-axle trailers without suspension system, is driven at a constant speed. Depending on the tested tires, it has been observed that the convoy may become severely instable. This instability is a large problem for the test team since the tires undertake too much overload which makes test results unexploitable. This is time consuming and expensive for the company. The aim of this thesis is two-folded. The first aim is to identify the phenomenon causing the instability from experimental data and also the parameters which influence the phenomenon. The second aim is to model the phenomenon from technical data in order to predict instability behaviors in advance. Models have been developed and the behavior have been analyzed and compared with experiments. The main result of this work is that the instable behavior is due to the excitation of natural modes of the convoy by the tires frequencies. Natural modes are identified as the natural bouncing mode of the trailers. The bouncing natural mode of a trailer depends on tires stiffnesses and the load on the trailer. Tires excitation frequencies are related to the test speed, the trailer track width and the rolling circumference of the tires. To get a good prediction tires stiffness and tires rolling circumference under operation require to be better characterized. Thanks to this work the test teams have a better understanding of the phenomenon and a tool which can be used to give a rough indication about problematic configurations. This tool cannot totally predict instable behaviors with the technical data at our disposal since some more parameters, which are not quantified for now, might influence the phenomenon. Nevertheless, these parameters have been highlighted by this study and if explored by the test team, a working predicting tool could be achieved.

No description available.

Planning vessels can reach high operational speeds thanks to their hull design. Some hull forms will develop large volumes of spray attached to the hull surface. The whisker spray is a thin layer consisting in droplets of water which can ac-count for a large proportion of the total resistance. A new concept to redirect the spray, called de°ectors, has been developed by the Swedish company Petestep. These de°ectors indicate higher e˝ciency than the time-proven spray rails tech-nology by removing a bigger portion of the spray area. The spray is re°ected back-wards rather than to the sides, which allows kinetic energy contained in the spray sheet to be converted to additional forward thrust. However, there have only been a few studies conducted on the e˛ects of de°ectors and there is no precise method to analyze their e˝ciency over the full range of operating speeds. For the above-mentioned reason, experimental testing is needed to have a more complete under-standing of the phenomenon in calm water and waves. In this study, model scale tests of a modular planning hull are carried out at the Davidson Laboratory towing tank. The goal is to verify the beneÿts of the spray de°ectors by direct comparison with the bare hull conÿguration at the same trim angle.