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  • 1.
    Casselgren, Johan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Rosendahl, Sara
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Engström, Niclas
    LKAB, SE-981-86 Kiruna, Sweden.
    Grönlund, Ulrika
    Autoliv Sverige AB, Active Saftey Tech Center, Linköping, Sweden.
    Evaluation of velocity and curvature dependence for roadgrip measured by low lateral slip2017In: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, E-ISSN 1745-6444, Vol. 12, no 1/2, p. 1-16Article in journal (Refereed)
    Abstract [en]

    Roadgrip is an important parameter for vehicle testing and road maintenance. Therefore, an evaluation of the velocity and curvature effects on roadgrip measurement was performed on asphalt roads and on two ice tracks using the continuous roadgrip apparatus RT3 Curve. The aim was to find suitable driving patterns for measurements on public roads and test tracks to ensure the repeatability of roadgrip measurements. During the evaluation, it was concluded that in order to achieve a reliable roadgrip value, regardless of road conditions, the radius of curvature should not be less than 20 m. The velocity dependency of the RT3 Curve is different for the two road conditions, with the measurements on ice being much more sensitive to velocity changes than the measurements on the dry asphalt.

  • 2.
    Christoffersson, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Safe Configurable Maps for Off-Road Sites: Proposed methods for safe and efficient map updates for autonomous trucks2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Autonomous vehicle technology is advancing at a very high pace and self-driving trucks on control-tower operated work sites is already a reality. These autonomous trucks need a highly accurate map of the surroundings for operation and navigation, and it is of great importance to be able to update that map with the ever-changing off-road work site. The autonomous fleet examined have to stop for every update of the site map, which induces unnecessary downtime when updating the site map frequently. The purpose of this work is to contribute to the development of safe configurable maps for autonomous vehicles on off-road sites by identifying and analyzing different map updating methods, proposing the best one, and suggesting how to implement it for this project's case. The result was five different map updating methods, which were evaluated with respect to efficiency and safety. Efficiency was evaluated by comparing total fleet downtime of the proposed solutions with the existing situation. Safety was evaluated by doing a fault tree analysis (FTA) for each proposed solution and comparing the relative size of the fault trees. Proposed Solution III using map tiles was chosen as the most appropriate method to implement for this project's case because it is both efficient and relatively simple. It divides the site map with a grid into smaller rectangular maps and only needs to stop vehicles which are inside the updated tile. The rest of the fleet is able to replace that tile parallel to operation and, therefore, total fleet downtime is significantly reduced. By reaching the stated goal, this work is in line with its original purpose and has contributed to the development of safe configurable maps for autonomous vehicles on off-road sites.

  • 3.
    Falk, Mathias
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Almgren, Stiven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Active Cooling Unit for Electrical Storage System2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Electro mobility is developing in a rapid pace. Volvo Penta and The Volvo Group are developing hybrid and fully electric solutions for a more sustainable future. One of the biggest limitations can be found in the batteries and its capacity affecting both power and range. Temperature management for batteries is important for a sustainable battery usage, if they are not used within the correct operating temperatures there will be both a performance and lifetime decrease. This report will handle a product development project, from idea to prototype build and final production proposition. Finding the best and most compatible cooling solution for Volvo and keeping the battery operating temperature within the boundaries given from the battery suppliers. The cooling solution includes the Active Cooling Unit, system layouts for combined cab climate and Electrical Storage System temperature management, including heating possibilities. The system is dimensioned of cooling 8 kW at 48°C ambient or coolant at 52°C with a fully operating system.

    The full text will be freely available from 2028-06-27 12:54
  • 4.
    Lidgren, Albin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Concept Study and Design of a New Torque Calibration Rig2017Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    When buying a new car today, the customer often expects to get a vehiclewith high quality. Each vehicle or engine should therefore be checked toassure quality. The same goes for clutches and couplings. A powerful enginebecomes useless when a clutch slips. Reliable torque measurement istherefore essential to the automotive industry. The herewith Bachelor thesisproposes a new torque calibration rig for online torque measurement in couplingapplications.The concept encompasses a servo motor with its associated electronics, agearbox to create the high torques (3 kNm), a reference torque transducer,and mounting elements or adapters. From the concept generation phase, thethesis includes CAD-models of the torque calibration rig with mathematicalmodels leading to the calculation of the measurement uncertainty of the calibrationsystem.This work was performed at BorgWarner PowerDrive Systems AB in Landskronaduring eight weeks; the two remaining weeks were completed in Lulea.

  • 5.
    Ludwell, William
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Quality Assurance of Saab Aftermarket Replacement Parts2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Saab Automobile AB went into bankruptcy in 2011 ending the production of the iconic Saab cars. There are still many Saab cars on the roads today that continue to need service and repairs. Orio AB has the exclusive rights of the Saab brand to provide the remaining cars with the parts, and technical know-how, to keep the remaining vehicles alive. This thesis will investigate five potentially problematic parts from Orio's Saab catalogue and determine technical solutions to the problems found, either availability issues or copied parts being sold in the general automotive aftermarket, referred to here as aftermarket threat. The parts chosen will be tested in real-life driving conditions and proposed solutions will be found.

    Three of the five parts are classified under aftermarket threat and will be tested against the equivalent available through the general aftermarket, and the remaining two are common failing parts that are unavailable from the OEM supplier. Aftermarket threat parts studied are: Ignition coils for the 2003-2011 Saab 9-3, ignition cassette for the 1998-2010 Saab 9-5 and the jalousie for the automatic gear selector fitting numerous Saabs. No longer available parts studied are: rear lights for the 2010-2011 Saab 9-5 and headlights for the Saab 9-4X.

    The OE and aftermarket ignition coils, and ignition cassette will be tested in various driving situations simulating real life driving conditions, misfires will be logged and compared. The OE jalousie's physical properties will be compared to the aftermarket equivalent to evaluate durability. The rear lights for the 9-5 have an issue with the halogen bulb generating too much heat and melting the socket and housing causing the light to fail. An investigation will be made to evaluate if an LED light could be a viable solution. The last part for testing was to investigate if the EU specification 9-4X headlight could possibly replace the unavailable original US market 9-4X Headlight.

    Results for the ignition coil were inconclusive due to unforeseen problems during testing. The aftermarket ignition cassette tested proved to be inferior to the OE part with initial results showing the the aftermarket cassette caused nearly three times as many misfires compared to the OE part. The aftermarket jalousie was however superior to the OE with the material being softer and more flexible. The rear light problem was resolved by replacing the halogen bulb with an LED and a load resistor. After numerous tests, the 9-4X headlight problem was solved by replacing the headlights with the European equivalent.

    The unforeseen problems that occurred with the ignitions coils was the difficulty of finding actual aftermarket coils. A similar problem was observed with the ignition cassette, but sourcing an actual aftermarket part did not prove to be as much of a challenge. Finding information about the material used for the jalousie proved to be challenging, even the service representative could not provide a more exact material than just TPE. Lack of parts availability for the 9-5 rear light, lead to the LED replacement only being theoretically tested. Calibration of the measuring equipment used on the 9-4X headlights was time consuming. After replacing the equipment testing proved more successful.

  • 6.
    Marth, Stefan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Häggblad, Hans-åke
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Oldenburg, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    A comparison between Stepwise Modelling and Inverse Modelling methods for characterization of press hardened sheet metals2017In: 6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2: June 4-7 2017, Atlanta, Georgia, USA : proceedings / [ed] Mats Oldenburg, Braham Prakash, Kurt Steinhoff, Warrendale, PA: Association for Iron & Steel Technology, AIST , 2017, p. 281-288Conference paper (Refereed)
    Abstract [en]

    The demand for weight reduction of cars has increased the number of press hardened sheet metal parts used in the automotive industry. This leads to an increased demand on the precision of simulations of press hardened sheet metals. An accurate prediction of the post-necking behaviour of materials is therefore needed to increase the precision of computer simulations with large deformations, as for example in forming simulations and crash simulations. Especially fracture simulations of press hardened steel parts with tailored properties have a huge demand on precise material models.

    Inverse modelling is a common engineering tool to characterize the elasto-plastic behaviour of materials.  Taking experimental data, such as force and displacement data, the material model parameters are optimised until the simulated output reaches a target function.  Then inverse modelling is highly time demanding and needs nonlinear hardening material models. 

    Lately a new fast method for post necking characterisation of sheet metals, called the Stepwise Modelling Method (SMM), was presented. This method uses full field measurements to obtain the strain field on the surface of sheet metal tensile specimens.  Furthermore, the stepwise modelling method models an experimental hardening curve in a stepwise process.  This hardening curve is a piecewise linear curve and not restricted to any specific material model.

    In this paper SMM is used to characterize the hardening behaviour for thermally treated boron steel.  These results are compared with the results of inverse modelling. Three different material models are used. The comparison shows a minor deviation in the resulting hardening relations between stepwise modelling and inverse modelling. Since the efficiency is an important factor in product development calculation times are taken into account.  Comparing calculation time using SMM is considerably more efficient than using inverse modelling. Furthermore another advantage of SMM is shown in the fact that the piecewise linear hardening curves can be fitted to almost any material model without computational costs.

  • 7.
    Nordin, David
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Design and Evaluatoin of a Carbon Fibre Bus Body2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The automotive industry is in constant development and in recent years the environmental legislations have been getting tougher. The need for lighter and stronger materials has increased according to these changes and composite materials such as carbon fibre reinforced polymers is showing potential of being a solution due to their high specific properties. This thesis is an investigation and design proposal for one way of making a carbon fibre bus body wall structure by the use of pultruded beam elements and a certain number of standardised node elements. This is done to increase the possibility of mass production and possibly lower the manufacturing cost for a carbon fibre structure. The methodology is based on a product development process where a market research as well as a literary study was conducted initially to see what work had been done in the area. Needs were investigated and formulated to a product specification from which concepts was generated using brainstorming methods as well as discussions with bus design engineers at Scania. A number of materials and manufacturing methods was analysed for the node elements and after comparing and scoring different concepts, a carbon fibre node element was chosen. Dimensioning calculations were made based on standardised tests which simulates different driving scenarios. The concept was then designed in 3D-cad and the final weight of the concept was measured to 194 kg. A comparison of the concept with a steel bus was made by the use of the life cycle analysis tool in CES Edupack 2017 which resulted in a difference of 47 tonnes carbon dioxide released for a diesel driven light goods vehicle during the first six years of the lifetime. The overall results show that a carbon fibre bus body might be economically beneficial during the entire lifetime of a bus even though the purchase price is higher.

  • 8.
    Woldu, Yared
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Fritz, Anton
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Using CFD to analyze thermal and optical influence on a zero pressure balloon at floating condition2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The ability to control the trajectory and understanding the atmospheric effects on the flight performance of a scientific high altitude balloon has long been an aspiring ambition. This thesis work analyses the thermal and optical environments at float using the simulation software, ANSYS FLUENT. The objectives for this thesis were to evaluate how the solar angle, sunshine factor and the ground emissivity altered the altitude for the balloon during floating condition in Steady-state simulations. A transient simulation was conducted to evaluate the diurnal cycle effects on the altitude of the balloon. The understanding of how the parameters influence the altitude will make it possible to autonomously route the balloon to desired altitudes where you have a favorable wind direction.

    Performing steady-state simulations showcased the significance of certain parameters. Different solar angles greatly influenced the temperature gradient on the balloon and hence a larger lifting force acted on the balloon when the sun was at its highest point. Varying the cloudiness mostly affected the maximum temperature distribution and did not affect the minimum temperature distribution. The steady-state simulations also indicated a limited but noticeable dependence on the ground emissivity. From the transient simulations it was further enhanced how great of influence the solar angle have, which was illustrated by running diurnal cycles. It was also apparent that there are great differences depending on the seasons. For future applications, it would be of interest to investigate the effects caused by wind velocities in the steady-state case. A comparative analytic solution should be performed in order to validate the simulation results.

1 - 8 of 8
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