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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Partial loudness assesment of windturbine sound through continuousjudgment by category-ratio scaling

Johansson, Anders January 2015 (has links)
The periodic and determinist nature of wind turbine sound is believed to be a key factor for the high degreeof audibility. The present study investigated how alterations in fluctuating frequency affect the loudnessperception and detectability of wind turbine sound with and without background noise. The instantaneousloudness was judged for wind turbine sounds of different sonic character and altered fluctuating frequenciesusing the method of continuous judgment by category-ratio (CJCR) scaling. The obtained results showedlimited effects on the audibility despite altered fluctuating frequencies, rather it was found that the spectralcues dominate the loudness perception. These results was consistent for both measurements situation ofloudness and partial loudness.
32

Light weight car seat

Mei, Tiina, Larsson, Marcus, Kruppa, Alexander January 2015 (has links)
Den här rapporten handlar om framtagningen av en bilstoldesign inom lättkonstruktioner. Stolen i fråga är anpassad efter ett steer-by-wire system, vilket innebär en datoriserad koppling mellan ratt, pedaler, motor och hjul. Rapporten behandlar vår arbetsgång med beräkningar, kravspecifikationer, labborationsresultat och materialforskning som ledde oss fram till vår slutliga produkt. Längst bak i rapporten finns alla bilagor. T.ex. den fullständiga kravspecifikationen, uppdraget som var givet från början samt beräkningar och koder. Stolen ska installeras i KTHs RCV och förhoppningen är att den även kommer användas i framtida koncept där hela störtbågen och chassit är anpassat utifrån viktoptimering.
33

Automotive Body Structure Assembly : Mass & Cost Saving Potential of Laser Welding Compared to Spot Welding

Klinger, Julius January 2012 (has links)
Due to the continuously increasing demands on the efficiency of road passenger vehicles the National Highway  Safety Traffic Administration (NHTSA)  commissioned a project to determine the achievable mass savings on an average, mass produced passenger car which are obtainable with today’s or within close reach technology. The major part of this project is conducted at EDAG, Inc. One of the approaches made within this program is to reduce the weight of a vehicle’s body struc- ture by replacing the commonly on a mass production vehicle applied joining technology resistance spot welding with laser beam welding. The main advantage is the possibility to bisect the size of the flanges since laser welding requires less flange width compared to spot welding. A sample structure is remodeled twice to create one almost solely spot welded and one almost solely laser welded body structure of the same vehicle. Those body structures are represented by two FEM models. Proper representation of the joining technology is applied to both FEM models in preparation of NVH com- putation runs, ensuring the comparability of the two body structures regarding their performance. In cooperation with experienced production engineers two assembly layouts for the spot welded and the laser welded structures are developed. For those assembly layouts cost calculations are done to oppose the attained mass savings to the increase in production costs. The weight difference between the two versions is determined to a remarkable 12.2 kg for the ana- lyzed sample structure. The laser welded structure thereby displays a slightly improved NVH perfor- mance compared to the spot welded structure. Taking the exemplary cost increase for the assembly of certain parts of the lower body structure into account gave a weight saving efficiency of 4.58 $ per saved kg. For the field of automotive engineering this is a rather high value, mainly caused by the still very extensive costs for laser welding equipment. With laser welding technology being more and more  adopted in mass production applications and most probably due technical improvements those costs are likely to decrease within the next few years. Even more mass savings could be achieved by adapting the design of the body structure more to the usage of laser beam welding.
34

Hybrid Electric PowertrainComparative Study

Laporte, Rémy January 2012 (has links)
New trends for environmentally-friendly mobility are rising and expectations derived from customers are significant. Urban areas such as London or even Stockholm are starting to build urban tolls by charging conventional vehicles while full‐electric powered vehicles are exempted. Carbon taxes will be certainly introduced at the EU scale in the next decade, which will strengthen those expectations of   transportation  changes  especially  regarding  private  vehicles.  High  electrification  degree  of conventional  vehicles  has  to  be  performed  to  answer  to  those  expectations.  To  avoid  range restriction mainly related to the energy content limitations in battery electric vehicles (BEV), fuel tank has to be kept in conjunction with internal combustion engine. Thereby, according to this statement, the design of either a plug‐in hybrid electric vehicle (PHEV) or a range extender (REX) in a second extent with an extensive full‐electric range is relevant in the next decade.
35

A new method for robust route optimization in ensembleweather forecasts

Skoglund, Lukas January 2012 (has links)
Denna artikel presenterar en ny metod för optimering av fartygsrutter där  era olika målfunktioner betraktas. Metoden bygger på en dynamisk programerings algoritm som påminner om Dijkstras grafsöknings algoritm, men som använder sig av Pareto-optimalitet för att hantera optimeringen av era målfunktioner. Metoden kan användas med både deterministiska och ensemble-väderprognoser. Fördelarna med att använda metoden tillsamans med deterministiska väderprognoser demonstreras i en jämförelse med en metod som baseras på Dijkstras algoritm. Jämförelsen visar, som väntat, att båda metoderna hittar samma rutt för minimal restid, men bara den metod som presenteras här hittar den rutt som minimerar bränsleförbrukningen, med en besparing på ungefär 15%. Utvärderingen av metoden tillsammans med ensemble-väderprognoser visar att det nns en stor fördel jämfört med att använda deterministiska väderprognoser om målet för optimeringen är minimerad bränsleförbrukning.
36

Energy balance of a vehicle

Gourdeau, Sarah January 2012 (has links)
Simulation has become a very useful tool to predict the characteristics of a system and perform analysis of parameters without having to run too many tests. The advanced system engineering team of Continental Automotive uses a 0D simulation program, AMESim, to realize simulations of vehicle models. These simulations are used e.g. to predict the fuel consumption and CO2 emissions. A tool has been developed over the course of previous internships to realize the energy balance of AMESim vehicle models, which goal is to check the consistency of the models (no creation or loss of energy) and simplify their analysis. In this thesis, this tool has been further improved and developed through a comprehensive analysis. The computations have been checked and corrected to fit best with the AMESim results and obtain a consistent energy balance. The program has been adapted to hybrid vehicles and combustion losses computations were introduced. The program is coded in Matlab for the computations and in HMTL and JavaScript for the display. After the program was validated, it was used to realize a study on CO2 emissions. Three vehicle models were used. The influence of some parameters on the CO2 emissions was analyzed: the mass, aerodynamic resistance, rolling resistance, frictions and electric load. The aim of the study was to assess which parameters had the most influence on the CO2 emissions reduction in the perspective of the 95 g/km goal by 2020 set by the European Union. It was shown that the parameters have different effects on the vehicles CO2 emissions and that this effect varied from one vehicle to another. Substantial CO2 reduction can be achieved by improving some parameters, which makes it possible for the diesel vehicles to reach the 95 g/km in 2020 target set by the European Union. However, to achieve this goal with gasoline vehicles, the resort to hybridization will probably be needed. To assess the possible benefits of hybridization, a fourth vehicle model featuring mild hybridization was used. However, the decrease of CO2 emissions enabled by this type of hybrid vehicle would still not be sufficient to meet the 95 g/km target with gasoline vehicles.
37

SANDWICH VERSUS SINGLE SKIN : Material Concept of a Patrol Boat in a Life Cycle Cost Perspective

Djurberg, Ebba January 2012 (has links)
This report describes the Master Thesis Project "Single Skin Versus Sandwich: Material Concept of a Patrol Boat in a Life Cycle Cost Perspective" performed at Kockums AB, Karlskrona, and reviewed and graded at the Royal Institute of Technology, Stockholm. There are both economic and environmental gains of developing fuel-efficient (light) vessels. Kockums have successfully produced ships in sandwich composite material, which is a light and stiff but expensive material concept. Building a vessel in single skin composite might result in a lower total life cycle cost due to several factors. Kockums wish to acquire more information of the affecting factors thus they have initiated this project. The project includes analyzing the accumulated cost of a concept patrol vessel while changing five variables: class notation ("Patrol" or "Passenger"), operational profile (10 or 35 knots), material concept (sandwich or single skin), material (carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP)) and choice of propulsion system (controllable pitch propeller (CPP), Inboard Performance System (IPS) or water jet) resulting in 48 versions of the vessel. First, the structural arrangement was adapted to the design loads of each version by iteratively seeking the maximal structural utilization of the elements. This was done by using a computational tool (RSTRUCT) that allows for effective scantling calculation. Then, the material, production and operational cost were determined for each version and the break-even points in terms of years of operation were found. The results gave insights concerning the characteristics of the different material concepts. The single skin versions were found to be both heavier (70 %) and more costly in terms of material and production cost (17 %) in relation to their sandwich equivalents. The break-even points between CFRP versions and GFRP versions were ranging between 4 and 14 years, depending on operational profile. For example, for a very low speed profile passenger vessel the break-even point was 40 years, implying that the GFRP version was the most beneficial choice. Regarding propulsion choices, the IPS system was the best choice for every version due to its high overall propulsive coefficient in a broad speed range.
38

Modelling and simulation of the three-wheeled urban concept vehicle Smite

Kovacevic, Igor January 2012 (has links)
This thesis treats the handling analysis of the Vehiconomic's three wheeled prototype vehicle "Smite". This is a light weight low emission vehicle intended for urban traffic but with sufficient power supply to manage highway driving as well. The purpose of this thesis is to evaluate the vehicle's stability and handling characteristics using the multibody simulation software ADAMS/Car, and also to try to find a more optimum configuration of the vehicle. The software in an excellent tool that allows you to examine different driving scenarios and easily make vehicle modifications, both quicker and safer than in real life. In order to obtain reliable results the simulations have to be as close to the reality as possible. The ADAMS/Car model was validated with the help of logged data, derived while performing physical test runs on an air strip. Maneuvers preformed were; Severe lane change, Slalom maneuver and a J-turn maneuver. Due to simplifications made in the virtual model, the validation did not generate satisfying results for all driving scenarios, but the model is considered good enough to help draw general conclusions about the vehicle's behavior. The largest simplification made was regarding the propelling of the vehicle, which was made front wheel driven instead of rear wheel driven. Due to the simple construction of the vehicle, very little room for modifications is available. The possibilities to affect the position of the center of gravity are very limited. The only room for modification available is in the front suspension system. Due to multiple mounting points for the spring/damper component, 12 different combinations of the front suspension system were generated. Additionally two more setups were made by changing the track width with the implementation of spacers. A suspension configuration was found that reduced the roll angle with approximately 10%.
39

Vibration mitigation for High Speed Craft

Olausson, Katrin January 2012 (has links)
The crew of small, high-speed marine craft (HSC) is exposed to high levels of vibrations and shocks that can imply risks for adverse health effects. The working environment needs to be improved by appropriately isolating the crew from the severe, non-linear accelerations that characterise the motions of small HSCs. This thesis presents a brief overview of the vibration mitigation techniques flexible hull design, active vibration control and suspension seats. The suspension seat is analysed further. A boat-seat interaction model describing the seat motions when excited by non-linear, vertical accelerations is established. The seat model is used to investigate how the seat characteristics influence the seat response motion, that is, the crew vibration exposure. Published experiment data in terms of accelerations at the seat base measured on a 10 meters HSC unit of the Swedish Coast Guard is used as exciting motion of the seat. By systematically varying the spring stiffness and damping coefficients of the seat, the response motion for 10 different seats are calculated and evaluated according to existing standards regarding whole body vibration exposure, ISO 2631-1 and ISO 2631-5. The thesis concludes that the mitigating effect of the seat can be improved radically by reducing the spring stiffness coefficients and increasing the damping coefficients of the seat. The spring stiffness is however limited downwards by the seat motion stroke, since bottoming out events have to be avoided and the motion stroke for practical reasons cannot be too large. Further, the relation between crew weight and resulting vibration exposure is investigated by varying the crew weight for two different seats. Slightly higher vibration levels are found for the lower crew weigths, although the distinction between the seat reponse motions is small compared to the variations found when comparing different seats. However, it is concluded that the crew weight is an important parameter when studying the vibration exposure, since it influence the motion stroke of the seat.
40

CONCEPTUAL DESIGN OF A HIGH-SPEED SUPERYACHT TENDER : HULL FORM ANALYSIS AND STRUCTURAL OPTIMIZATION

Jonas, Danielsson, Strømquist, Jørgen January 2012 (has links)
The focus of this thesis is to create a new conceptual design for a Superyacht Tender. This type of boat is usually primarily focused on aesthetical and practical aspects. However there are costumers requesting performance, which will be the main focus here. A supplementary task is to find ways to apply an engineering approach in the design of a recreational craft, in order to help small craft manufacturers optimize their products’ performance. The resulting design is intended to fill up the void of large, high- performance superyacht tenders, with its lightweight hull and powerful engines. In order to succeed in this, an analytical model for performance prediction will be created and structural optimization based on available methods will be performed. The motivation for this is that the industry today is dominated by a trial-and-error approach based on experience and testing, and most manufacturers of recreational powerboats apply little or no analytical methods in their designs. Predicting resistance on twin stepped hulls is a great challenge and it has not been possible to find any established methods suitable. For this reason, a model for estimating power requirement and running trim of such hulls has been developed. The model is based on Savitsky (Savitsky 1964) theory and a single step performance method developed by David Svahn (Svahn, 2009). The new developed model in this project has been benchmarked to an existing powerboat, with good results. The boat used as benchmarking is the Hydrolift C-31, where all the parameters needed was received from Hydrolift. The new method has been used to design and position steps for the superyacht tender. The required power has been used to select engines and drives, and the installation of these has been looked into closer. In order to minimize weight and lower resistance, structural optimization has been performed. A method for optimization of sandwich and single-skin panels with stiffeners has been extended to take face, core and stiffener strength as well as stiffener and plate stiffness into account. Also, various structural layouts have been designed and compared to find the most efficient setup. The results from the optimization model showed that the best choice was a carbon fiber sandwich as material in the panels when considering weight. The carbon fiber construction saved approximately 25% weight compared to fiberglass in the hull, and by introducing a sandwich, additional weight could be saved and the complexity of the structure could be reduced. High-speed small craft are subject to ISO rules, which only apply up to speeds of 50 knots. The ISO rules are sometimes viewed to lack in margins which is why DNV’s HSLC rules has been used in this project. The results from the structural part showed lower weight than expected, about 3900 kg dry weight. With 8 passengers including luggage and semi-filled tanks, the resistance model showed that the new design should be able to travel at 65 knots with 1250 horsepower installed.

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