Vehicle pull is an issue that occurs when the driver has to exert a discerniblesteering torque (pull) for the vehicle to run straight, otherwisea lateral drift takes place. This thesis deals with the straight motion ofroad vehicles, with particular focus on the role played by tire characteristics,road cross slope and interactions between tires and vehicle.A thorough theoretical approach has been adopted, adjusting thePacejka’s formulation for effective axle characteristics and extendingthe linear handling diagram theory. This has allowed to obtain innovativeanalytical expressions, describing the straight-driving slip anglesand steering torque offsets.The analytical expressions have been validated, together with asingle-track model, by means of quasi-static and dynamic simulationsof a full-vehicle model. Moreover, a relationship between tire characteristicsand on-center handling has been described, that relates objectivemetrics with subjective feedback.The obtained analytical expressions can be used by vehicle OriginalEquipment Manufacturers (OEMs) or Tire Suppliers for productdevelopment. / Däckinducerad fordonsavdrift är ett problem som medför att förarenmåste utöva ett märkbart-styrmoment för att fordonet ska köra rakt.Detta examensarbete handlar om bilens avdrift vid körning rakt fram,med särskild fokus på inverkan av däckegenskaper, vägens lateralalutning och samverkan mellan däck och fordon.Ett grundligt teoretiskt tillvägagångssätt har valts: Pacejkas formuleringav effektiva axelegenskaper har anpassats, och den linjära handlingdiagram teorin har expanderats. Detta har gjort det möjligt att erhållainnovativa analytiska ekvationer som beskriver de avdriftsvinklaroch styrmoment som krävs för att fordonet ska färdas rakt fram.De analytiska ekvationerna har validerats, med hjälp av en cykelmodellsamt med kvasi-statiska och dynamiska simuleringar av enhelfordonsmodell. Dessutom har ett samband mellan däckegenskaperoch kursstabilitet tagits fram, som relaterar objektiva parametrar medsubjektiv feedback.De erhållna analytiska ekvationerna kan användas av fordonstillverkareoch däckleverantörer för produktutveckling.

This master thesis investigates the possibility to rebuild heavy-duty trucks poweredby liquefied natural gas (LNG) to other fuel options such as compressednatural gas (CNG), diesel or ethanol. The background is that the second handvalue for a LNG truck is lower than a similar diesel truck due to an undevelopedinfrastructure with few refuelling stations. This results in a small market for secondhand LNG trucks.Both tractor and rigid trucks are evaluated from a technical perspective to determinewhich components that need to be changed when switching from LNG toanother type of fuel. When that is completed each fuel alternative is evaluatedbased on cost and market interest. Also certification and other legislations areinvestigated to determine if they will affect the rebuilding process.The result shows that the rebuild faces different technical complexity dependingon the target fuel alternative. It is concluded that a rebuild to diesel or ethanolis expensive due to many changes needed for the engine and aftertreatment andtherefore these alternatives are not a good choice for a rebuild. A rebuild to CNGis still expensive but can be of interest for rigid trucks, but not for tractor truckssince they usually have a demand for longer range. In order to get the final cost ofthe rebuild to CNG a commercial assessment has to be made and the rebuild willdepend on in which country the rebuild is performed due to different legislationsfor re-registration which may be a an obstacle. / Det här examensarbetet undersöker möjligheten att bygga om tunga lastbilarbyggda för LNG (Liquefied Natural Gas) till andra drivmedel så som CNG (CompressedNatural Gas), diesel eller etanol. Bakgrunden är att andrahandsvärdetför en LNG lastbil är lågt jämfört med en likvärdig modell som går på diesel pågrund av att infrastrukturen för LNG är dåligt utvecklad med få tankställen. Detleder till att marknaden för andrahandsbilar med LNG är liten.Både dragbilar och lastbilar undersöks ur ett tekniskt perspektiv för att se vilkakomponenter som behövs bytas ut när man går från LNG till ett annat drivmedel.Efter det genomförts utvärderas varje drivmedelsalternativ utifrån kostnad ochmarknadsintresse. Även certifiering och lagkrav undersöks för att få en bild avhur detta kan påverka ombyggnationen.Resultatet visar att en ombyggnation till diesel eller etanol är mycket kostsam eftersomstora förändringar måste göras för motorn och avgasreningen och därförär dessa inte ett rimligt alternativ för ombyggnation. Att bygga om till CNG ärden möjlighet som är mest intressant även om priset fortfarande är högt. Dennaombyggnation lämpar sig bäst för lastbilar eftersom dragbilar ofta har krav på enlängre räckvidd. Den slutgiltiga kostnaden för ombyggnationen måste tas framgenom en kommersiell bedömning och ombyggnationen kommer bero mycketpå vilka lagar och regler som gäller för omregistrering i det land där ombyggnationenska genomföras.

The thesis consists of building vehicle models for lateral dynamics that provide accurate results, while being simple enough to highlight clear relationships between vehicle properties and handling behaviours. The approach that characterizes the present work is built on the foundations provided by the bicycle, or single-track, model (STM). Nonetheless, its developments and improvements substantially differ from the usual sequence found in literature. Most studies based on this analytical vehicle model satisfy the quest for increased robustness by involving nonlinear description of the contact forces generated between tyres and ground. The presented analysis, instead, embraces the challenge of using completely linear models to describe vehicle lateral dynamics in a variety of driving situations. Hence, the aim of this thesis is to provide the reader with a deeper understanding of the effects of various physical properties on the actual dynamic behaviour, by complementing numerical correlations obtained from simulation outputs with analytical descriptions of their causes. The first step of the presented work deals with the selection and design of driving scenarios aiming at comprehensively evaluating vehicle handling, as well as defining the boundaries of the investigation. As in most engineering problems, a compromise has to be sought, since the set of maneuvers has to be broad enough to point out various dynamic characteristics, while limiting the time needed to perform evaluation of a real vehicle. Furthermore, the space occupation of each maneuver must allow execution in an actual testing facility. The design of suitable driving scenarios triggers an iterative process, in which the initial formulation of the single-track model is complemented with additional states and sources of complexity, based on the limitations that simulation outcomes point out. A complex model, previously built with the aid of Multi-Body Dynamics software, is initially accepted as a \black box", and adopted as a reference to estimate qualities and deficiencies of the results. The next step of the work deals with physical vehicle testing and correlation. After post-processing the data and comparing it to the analytical vehicle model, it is seen that the vehicle model represents the physical vehicle behaviour very well. The area where the model lacks is in transients, which in-turn can be explained by the lack of compliance in the system. The last part of the thesis brie y touches upon the vehicle behaviour in a dynamic driving simulator along with effects of motion cueing gains. / Det här arbetet består av att skapa lateraldynamiska fordonsmodeller som både ger noggranna resultat och är tillräckligt enkla för att förtydliga samband mellan fordons egenskaper och deras dynamiska beteende. Tillvägagångssättet som används i den här undersökningen baseras på den så kallade cykelmodellen, eller single-track modellen, dock skiljer sig vidareutvecklingarna av modellen från de typiska som beskrivs i litteraturen. De flesta studierna som baseras på samma analytiska fordonsmodell uppfyller kravet för robusthet genom att beskriva kontaktkrafter mellan däck och mark med hjälp av olinjära funktioner. Den här analysen grundas på utmaningen att enbart använda helt linjära modeller för att beskriva fordons lateraldynamik i olika kösituationer. Således, målet med detta arbete är att ge läsaren en fördjupad förståelse om effekter av många fordonsegenskaper med hänsyn till det dynamiska beteendet, genom att komplettera numeriska korrelationer från simuleringar med analytiska motiveringar om deras orsaker. Det första steget i denna analys handlar om valet och utformningen av manövrar som skall utföras för att få en omfattande överblick över fordons köregenskaper samt definiering av gränserna för undersökningen. Som i de flesta tekniska ämnen behöver en kompromiss åstadkommas: urvalet av konsekvenser skall vara tillräckligt brett för att beskriva många fordonsegenskaper, samtidigt som ett begränsat antal prover kan hjälpa till att minimera tiden och resurserna som behövs för att utföra utvärderingen i verkligheten. Dessutom måste ytan som behövs för att köra varje manöver rymmas på en verklig provbana. Utformningen av lämpliga konsekvenser ger uppslag till en iterativ process, där modellens ursprungliga formulering vidareutvecklas med ytterligare tillstånd och parametrar, som väljs enligt begränsningar i matematiska beskrivningen som identifierats tack vare simuleringarna. En avancerad modell, som byggts i förväg med hjälp av ett stelkroppssimuleringsprogram, betraktas som en ”svart låda”, och utgör en referens för att uppskatta resultatens noggrannhet eller otillräcklighet. Nästa steg i analysen fokuserar på fysisk fordonsprovning och egenskapers korrelation. Jämförelsen mellan experimentella data och resultat från den analytiska fordonsmodellen visar att den matematiska representationen återspeglar fordonets beteende noggrant. Det enda huvudsakliga området där den förenklade modellen avviker från verkligheten är vid transienterna, som kan motiveras av begränsningar i modellens elastiska egenskaper. Sista delen av arbetet berör kortfattat fordonets beteende i en dynamisk körsimulator samt effekter av motion cueing parametrar.

As the challenge grows in the vehicle industry, tightening the margins on financial and environmental costs of the vehicle development, computer aided engineering becomes more and more attractive. Extensive work is being invested in creating detailed models that can replicate vehicle behaviour accurately and efficiently. The work in this thesis starts with studying objective and subjective evaluations of vehicles as well as their counterparts in vehicle models and a simulator environment. Then, it continues to locate the weaknesses in the models, and investigate the possible improvements. The first part of the thesis focused on performing a literature study concerning the objective metrics and their use in the vehicle industry, as well as the use of simulators. This served as a foundation for the use of objective metrics in the validation of the CarRealTime models. The tools used in the thesis were also introduced. The work continued with the study of previously collected data concerning vehicle evaluation through subjective assessment and objective metrics, with different anti-roll bar configurations, to build trust in the ability of the drivers in evaluating these criteria. Similar data from the CarRealTime models and the simulator were also studied. The aim was to evaluate the simulator driving experience accuracy through the subjective assessment. The weaknesses of the model were identified, and an improved steering model was introduced, replacing the old lookup tables with a Pfeffer model from CarRealTime combined with the steering assist unit in Simulink. An extensive parameter study was performed to understand the effect of selected parameters on the driving experience. Using the same model, the simulator delays were studied in terms of replicating yaw and lateral movements, and how this can affect the driver’s perception of the driving experience. Finally, the results from the parameter study were used to assign the weight parameters in the optimization objective function where the goal was to study the possibility of improving the accuracy of the driving experience as well as counteracting the effects of simulator delays. The Matlab Optimization Toolkit was used in the process. As a conclusion, it was shown that the subjective assessment together with the objective metrics played a crucial role in identifying model and simulator weaknesses. The parameter study showed promising opportunities in solving the aforementioned issues, with the optimization tool and boundaries needing more elaborate work to reach conclusive results.

Arctic Trucks have been modifying vehicles such as the Toyota Hilux, Toyota Land Cruiser, Isuzu D-Max, Nissan Patrol and Nissan Navara for over 25 years for special projects as well as for recreational purposes both in Iceland and other countries. Arctic Trucks started up as a sub-division for Toyota Iceland but became an independent company in 2005. Their capability to make off-road vehicles is well known, the Toyota Hilux AT38 being their flagship. It has been driven to both the magnetic north pole, the South Pole and various other remote places and is widely used for logistics in Icelandic highlands as well as other places both during summer and winter time. This M.Sc. project in vehicle engineering covers measurements of energy consumption of a modified Toyota Hilux AT38 2017 in order to determine if some improvements are possible when it comes to fuel consumption and the vehicles environmental impact by hybridisation or full electrification of the vehicle. Fuel consumption is measured in various on-road and off-road conditions (gravel, snow and asphalt). Calculations are made to estimate the effect on fuel consumption of the climate control in the vehicle cabin. Air drag coefficient and friction coefficient are estimated based on coast-down tests in real-life conditions. These factors are necessary to evaluate the total running resistance of the vehicle. These fuel consumption measurements show that the fuel consumption for off-road driving is quite high and since this type of vehicle also needs to be light, the advantages of hybridisation or full electrification need to be examined further. For highway and city driving, hybridisation might be feasible but many factors need to be looked at for that case as well. As of now, battery technology and lack of infrastructure are standing in the way of this type of electric or plugin hybrid vehicles, since these vehicles are used in environments where electricity or even fossil fuel is hard and expensive to reach.

This document is a report of my thesis which deals with the transformation of a metallic frame into a composite frame. A composite frame would require less assembly time since it is composed of less components. The maintenance plan, required for metallic structures, would not be required anymore. Finally, the weight of the structure could be reduced.The resolution of this problematic is done in the following way. Once the pre-design of the frame settled, the finite element model is modified accordingly. The finite element outputs give the load per finite element and enable a sizing of the whole structure per section and per element. The design of the frame is then modified according to the results, the finite element model modified again and the sizing conducted another time until the design is in accordance with the design and sizing requirements.The results of this whole procedure give a structure that can withstand the critical loads but an increase in the weight by 1,65kg. When analyzing the results, the design of the frame, taken from a metallic frame and thus higher than a usual composite frame, appears to be unappropriated. Furthermore, the sizing of the skin for buckling failure is already at its limit. A modification in the shape of the frame, and especially the height, would be the most efficient way to adapt the design.Though possible, this modification would require a laborious and important change of the finite element model, which is not the aim of the thesis but could constitute another interesting topic to work on.

the FE analyses. Traditionally all parts are modeled with isotropic base material. Analyses are made on a part of the nozzle which includes both a butt weld and metal deposition and which is an interface to another part causing loads that has to be sustained by the weld and the MD. As a small part of this thesis was also a fatigue study made to a spot weld test specimen. In order to strengthen the nozzle to prevent structural damage, an outer layer is added to the already existing metal cone by material deposition, MD, or additive manufacturing. During the manufacturing process the material will indicate some degree of anisotropic properties. The key purpose of this thesis was to analyze how this anisotropic behaviour might affect the structural stiffener connected to this anisotropic material when exposed to a load at the end of the stiffener. Further analysis due to fatigue was also done to parts of the structure. The procedure was done by building a model and setting up the different anisotropic properties with help of a finite element program, Ansys. The material properties regarding the anisotropy of the material was changed and compared in order to see how it affected stresses and strains in the anisotropic material and it‘s surrounding materials. Further analysis was made to the properties of the weld such as the yield limit. The result would indicate that for loadings that did not generate plastic deformations, hence elastic deformations, there were no significant difference forthe different trial values of the yield ratios. However, the differences became parent when studying large plastic deformations. Variation of the Young’s modulus would show some differences in the monitored properties for both elastic and plastic deformations. Studies of degrading the welds yield limit would show no diffrences when elastic deformations were present, but would have a big impact when large plastic deformations were present. The J-values variations for the spotweld would indicate huge differences depending on the yield limits for the spotweld and base material. / Detta examensarbete undersöker hur strukturella marginaler påverkas av att inkludera anisotropiska egenskaper för delar av en struktur samt att inkludera en svets som har andra material egenskaper såsom sträckgräns jämfört med anliggande material. Tidigare beräkningar är gjorda med antagandet att ingående material delar i strukturen är isotropiska. Analyserna omfattar styvhets bracketter som svetsas mot den anisotropiska delen av raket mun- stycket som är utsatta för laster som uppstår genom anslutning via andra delar på munstycket. En mindre analys gjordes också av en test detalj där två metall plattor svetsas ihop med hjälp av en punktsvets som förekommer på munstycket. Analyser med hänsyn till utmattning har också varit en del i detta arbete.  För att styva upp raket munstyckets övre del så adderas ett yttre hölje genom additativ tillverkning. Denna tillverknings metod ger upphov till att det pålagda höljet uppvisar anisotropiska egenskaper. Inledningsvis så skapades en finit element model i programmet Ansys där det anisotropiska materialet definierades samt material egenskaper för svetsen. Beräkningar gjordes sedan utifrån att en last pålades i utkanten av styvhets bracketten och laster och töjningar noterades för varje beräknings cykel för dom olika delarna av strukturen.  Resultaten visade att för laster som inte genererade några plastiska töjningar, dvs elastiska töjningar, att det inte var några skillnader när olika värden påsträckgränserna för den anisotropiska delen av strukturen ändrades. Däremot var ändringarna mer påtagliga när töjningarna var plastiska, dvs för större pålagda laster som genererade stora kvarvarande töjningar i strukturen. Variationer av styvheterna i den anisotropiska delen i strukturen visade skillnader för både elastiska och plastiska töjningar. Analyser där svetsens sträckgräns var mindre än närliggande material visade inga direkta skillnader för elastiska töjningar men visade stora skillnader för plastiska töjningar.  J-integral värdena i punktsvetsen som funktion av pålagd last visade sig vara beroende av sträckgränsen för punktsvetsen samt för bas materialet.

This thesis investigates the possibilities of implementing thermal aspects in Topology Optimization (TO) of hot engine structures. Topology Optimization is an effective tool for conceptual design in numerous field of applications. At GKN, this optimization technique has previously only been successfully implemented for structures affected by mechanical loads. The aim with this study and the ongoing research at GKN, is to improve the in-house developed multi-disciplinary optimization procedure called Engineering WorkBench (EWB). By expanding the applicability of a more comprehensive TO which includes the thermal expansion. However, since there is no straight forward solution provided by the FE software’s, a better understanding of TO in general and for thermally loaded structures in particular, is needed before deciding on an application strategy.Two approaches for the thermal implementation in TO of the Turbine Rear Structure (TRS) have been studies and evaluated. The first is a stress constrained optimization procedure, based on requirements for the number of thermal load cycles, calculated in CUMFAT, an in-house developed program for life prediction. The second approach is a case trial study of the coupled thermal-mechanical structural optimization. The trials are performed systematically to illustrate what type of geometrical variations one can expect in the TO outcome when varying different factors in the optimization set up, such as the load type magnitude and optimization formulation. The evaluation of these to different approaches will increase the understanding of the challenges involved when performing TO of this type of structure.The complexity of this implementation is clearly demonstrated by the variation in optimization outcome. The results shows the importance of having substantial knowledge about the model, load cases and the optimization purpose before defining the optimization problem. Finally, suggestions for the continuation and implementation of thermal TO in the EWB, are presented. / Det här masterexamensarbetet undersöker möjligheterna för implementering av termiska aspekter i topologioptimering (TO) av strukturer belastade med höga temperaturer och stora temperaturvariationer. Topologioptimering är ett effektivt verktyg för konceptuell design som kan användas i en rad olika områden av strukturer. På GKN har denna typ av optimering endast implementerats för mekaniskt lastade komponenter. Det finns dock en stor efterfrågan efter en topologioptimeringsteknik som kan appliceras på även de varma strukturerna belastade med både mekaniska och termiska laster. Syftet med den här studien och det pågående utvecklingen på GKN Aerospace Sweden, är därför att utveckla och förbättra den in-house-utvecklade multidisciplinära optimeringsprocessen som kallas Engineering WorkBench (EWN). Genom att expandera tillämpningen av TO genom att inkludera den termiska expansionen i optimeringsprocessen. Idag finns det inga mogna lösningar för hur man ska hantera sådana problem i de kommersiella finita elementverktygen. En bättre stor förståelse för TO och termiskt lastade komponenter, krävs därför innan en metod för lastfallinkluderingen kan tas fram.Två olika metoder för termisk implementering i TO har utvecklats och evaluerats i denna studie. Båda metoderna har prövats genom FE modellering av en jet-motorkomponent kallad Turbine Rear Structure (TRS) som tillverkas av GKN. Den första metoden är en strukturoptimering med spänningsvillkor som bestäms genom krav på produktens termiska livslängd. Dessa krav beräknas genom CUMFAT, ett in-house-utvecklat program för livstidsberäkning. Den andra metoden är en fallstudie för termomekanisk strukturoptimering. Prövningar görs systematiskt för att illustrera vilken sorts geometrisk variation som kan förvändas efter TO när olika variabler, villkor och målfunktioner i optimeringen ändras. En utvärdering av dessa två metoder kommer att öka förståelsen utmaningarna anknutna till utförandet av TO av den här typen av strukturer.Utmaningarna och komplexiteten av den här typen av optimering visas tydligt genom variationen i optimeringsresultaten. Det visar också vikten i att ha en utbredd kunskap om modellen, lastfallen och syftet med optimeringen innan optimeringsproblemet formuleras. Slutligen presenteras förslag för hur denna typ av optimering ska implementeras i EWB och det framtida arbetet på GKN.

This report is a master thesis performed at The Royal Institute of Technology divisions of Lightweight Structures and Naval Architecture in collaboration with the Swedish defence material administration, FMV. There are several naval submarines used by the Swedish navy and more to be built. The existing submarines have stability problems due to a high centre of gravity. Most parts on the existing vessels are made of steel, despite a position far above the vertical centre of gravity. By replacing the current steel casing covering the top part of the submarines pressure hull and the rudders placed on the tower, to a lighter composite structure it is possible to lower the centre of gravity. In this report the composite structure of the rudder and the casing has been weight optimized to achieve a structure as light as possible, but still able to withstand the forces applied to the structure. An analysis of the applied loads shows that the dimensioning loads vary between 50 and 90 kPa depending on the specified part. The results show that it is possible to decrease the weight of the rudder and casing with over 80 %. This would also give the submarine an increase in initial stability with over 40 % compared to the existing steel construction.

Commonly, when calculating ship responses one uses idealized wave spectra to represent the sea. In the idealized model, the sea is frequently assumed to consist of swell and windwaves, which are usually represented by idealized 1D wave spectra, and the directionality of wind-waves is accounted for by multiplication with a standard spreading function. In operational response predictions these idealized spectra are typically generated by extracted parameters from real directional 2D wave spectra obtained from a weather forecast, i.e. spectra that reflects the sea state conditions for the particular place and time. It is generally not known in a statistical sense how large the errors become when idealized wave spectra are used to represent 2D wave spectra, especially not regarding the directionality. The objective with the study is hence to assess the errors that arise when adopting this simplification. The analysis compares three ship types that cover different combinations of hull form, load condition and operational conditions: a 153m RORO ship, a 219 m PCTC and a 240m bulk carrier. Chosen response parameters are roll motion, vertical acceleration and wave added resistance, which were calculated in 12240 sea states, for 10 speeds and 36 courses for each ship. The sea states are forecast 2D spectra from the North Atlantic 25th of September 2012. Transfer functions were generated from the hull geometry and realistic load conditions at speeds 2-20 knots. For each sea state-speed-course combination, responses were calculated for 2D wave spectra and corresponding generalized spectra. The error is taken as the difference in response between results obtained with 2D and idealized spectra, using 2D-results as reference. Several statistical measures were used to represent the errors for one sea state with only one number, and among them the root-mean-square error (RMSE) and the worst possible error (WPE) are regarded most relevant. The results show that the relative error decreases with increasing share of wind waves and decreasing share of swell. Multi-directionality of wind waves causes large errors only for small waves, and it is concluded that for higher sea states (for which the wind waves are predominant) the Bretschneider representation with spreading function leads to small relative errors. Absolute errors are considered the only relevant for investigating the effect of the error on seakeeping calculations. In general, the RMS acceleration levels are in the order of percentages of one g for all ships. For the bulker, WPE and RMSE for wave added resistance was found to be 8.3% and 3.8% of the total calm-water hull resistance in general, and almost 50% in worst case. The roll angle bias could reach up to 15. Also, the effect of ship speed was investigated, and it shows that the error increases in general with higher speed. It is concluded that it is necessary to use 2D spectra in order to avoid large errors, and to keep performance predictions correct on average.