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  • 201.
    Barsoum, Zuheir
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Samuelsson, Jack
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Fatigue and Quality Analysis of Cruciform Joints Welded with Different Methods, XIII-2136-062006In: International Institute of Welding: IIW 59th Annual Assembly, 2006Conference paper (Other academic)
  • 202.
    Barsoum, Zuheir
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Samuelsson, Jack
    Volvo Articulated Haulers AB.
    Fatigue Assessment of Cruciform Joints Welded with Different Methods2006In: Steel Research International, ISSN 1611-3683, Vol. 77, no 12, p. 882-888Article in journal (Refereed)
    Abstract [en]

    The advantages of the relatively new laser welding method are low welding distortions and high productivity, and it opens new opportunities for welding of steel structures in the automotive and heavy machinery industries. There is a need for understanding the fatigue strength and to develop fatigue design curves for laser welded joints. In this paper fatigue testing and weld quality of Hybrid Nd: YAG laser/MAG and MAG welded non-load carrying cruciform joints is examined. Four batches were produced, tested and the results were compared. The local weld geometry of the cruciform welded joints was measured and analysed. The measured parameters were used to calculate the stress concentration factors by implementing FE-models, in order to anticipate the influence of size of weld geometrical parameters on the stress concentrations. Residual stress measurement was carried out close to the toe region using the X-ray diffraction method and weld defects (cold laps) in the cracked specimens was measured.

  • 203.
    Barsoum, Zuheir
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Samuelsson, Jack
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Residual Stress Prediction and Relaxation in Welded Tubular Joints2006In: IIW Doc. No. XIII-2135-06/XV-1225-06, 2006Conference paper (Other academic)
  • 204.
    Barsoum, Zuheir
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Samuelsson, Jack
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Torsion Fatigue and Residual Stresses in Multi-Pass Welded Tubular Joint2005In: IIW Doc. No. XIII-2073-05, 2005Conference paper (Other academic)
  • 205.
    Barsoum, Zuheir
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Samuelsson, Jack
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Jonsson, B.
    Björkblad, A.
    Fatigue design of lightweight welded vehicle structures: Influence of material and production procedures2012In: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture, ISSN 0954-4054, E-ISSN 2041-2975, Vol. 226, no 10, p. 1736-1744Article in journal (Refereed)
    Abstract [en]

    Structural details and components in many types of products are continuously subjected to variable amplitude loading during operation. Fatigue loading and fatigue damage is thus the most common failure mode for the mentioned equipment in operation. The influence of the material grade, weld quality and fabrication procedure have a major impact on the structural durability of welded vehicle structures. The comprehensive research work within the Nordic research and development community have contained development of finite element modelling of complex structures, including crack growth in two- and three-dimensional fatigue testing of welded small-scale specimen and full-scale components, investigations of weld defects and flaws (e.g. cold laps) and weld roots. An important part of these projects is related to simulation and measurements of formation and relaxation of residual stresses. Within these projects three new quality systems, for welded and cast components and for cut edges, have been developed based on a scientific ground and a fitness for purpose design philosophy. Volvos new weld class system, which is an open standard, is now a base for the revision of the international weld quality system ISO 5817. In this article the major findings in these research activities are briefly presented and discussed.

  • 206.
    Barsoum, Zuheir
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Sperle, Jan Olof
    Mentorprogram för forskning kan ge kommersiella fördelar för svensk industri2009In: Svetsen, ISSN 0039-7091, Vol. 68, no 2Article in journal (Other (popular science, discussion, etc.))
  • 207.
    Bartos, Elias
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Ahlberg, Kristian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Minimizing of Drain Leakage on a Scania Retarder2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    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.

  • 208. Battley, M.
    et al.
    Allen, T.
    Schierlink, J.
    Lake, S.
    Pehrson, Petter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Hydroelastic behaviour of slam loaded composite hull panels2008In: High Perform. Yacht Des. Conf., HPYD, 2008, p. 37-46Conference paper (Refereed)
    Abstract [en]

    The effects of stiffness on hydroelastic responses of composite marine hull panels subjected to water slamming loads have been experimentally characterised. Panels included a very flexible single skin laminate, a medium stiffness sandwich panel and a very stiff sandwich panel. Panels were tested at a deadrise angle of 10° for a range of water impact velocities from 0.5 to 7m/s in a Servo-hydraulic Slam Testing System. Results demonstrate that the panel stiffness has a significant effect on the responses of slam loaded composite panels. Flexible panels had reductions in the local velocity at the centre of the panel relative to the water, reducing peak pressures at the panel centre. Pressures increased near to the chine edge of the panel, possibly due to reductions in the local deadrise angle due to panel deformation. Such effects were particularly noticeable when the loading rate was of similar order to the first natural frequency of the panel. The implications of the effects of panel stiffness on effective pressure and panel structural response on composite structural design are discussed.

  • 209. Battley, Mark A.
    et al.
    Allen, Tom D.
    Pehrson, Petter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Stenius, Ivan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Rosén, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Effects of Panel Stiffness on Slamming Responses of Composite Hull Panels2009In: 17th International Conference on Composite Materials, ICCM17, 2009, p. 1-11Conference paper (Refereed)
    Abstract [en]

    Controlled water slam testing of composite hull panels was conducted to study the effect of hydroelasticity for three panels with different stiffnesses. The experimental methodology successfully characterised the hydroelastic behaviour, which included kinematic as well as inertial effects. Hydroelastic effects included changes in panel geometry, local velocity, fluid pressures, and panel structural responses.

  • 210. Battley, Mark
    et al.
    Burman, Magnus
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Characterization of Ductile Core Materials2010In: Journal of Sandwich Structures and Materials, ISSN 1099-6362, E-ISSN 1530-7972, Vol. 12, no 2, p. 237-252Article in journal (Refereed)
    Abstract [en]

    This article describes an experimental investigation of characterization methods for ductile core materials. Full-field optical strain measurement methods are used to determine the strain distributions in standard testing methods such as block shear and four-point beam testing, particularly for highly ductile cores subjected to large deformations. The results show that the stress and strain fields in both block shear and sandwich beam tests are very different to those assumed by the testing standards. The test methods result in complex post yield states of stress in the core materials, meaning the core shear strength and ultimate shear strain should not be calculated by classical methods in the post yield region.

  • 211.
    Battley, Mark
    et al.
    Centre for Advanced Composite Materials, University of Auckland, New Zealand.
    Stenius, Ivan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Dynamically Loaded Marine Composite Structures2003In: 14th International Conference on Composite Materials, 2003Conference paper (Other academic)
  • 212.
    Battley, Mark
    et al.
    Centre for Advanced Composite Materials, University of Auckland, New Zealand.
    Stenius, Ivan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Breder, Johan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Edinger, Susan
    High Modulus (NZ) Ltd, Auckland, New Zealand.
    Dynamic Characterization of Marine Sandwich Structures2005In: 7th International Conference on Sandwich Structures: Advancing with Sandwich Structures and Material, 2005, p. 537-546Conference paper (Other academic)
    Abstract [en]

    Dynamic experimental and theoretical methods for sandwich panel structures subjected to water slamming are described, including a unique servo-hydraulic controlled slam test system and a pressure based transient finite element technique. The pressure simulation method accurately represents the pressures observed in slamming tests, and the transient dynamic finite element modelling can simulate sandwich panel responses to a slamming load.

  • 213. Baumann, H. D.
    et al.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Valve-Induced Noise: Its Cause and Abatement2008In: Handbook of Noise and Vibration Control / [ed] Malcolm Crocker, John Wiley & Sons, 2008, p. 935-945Chapter in book (Refereed)
  • 214. Baumgartner, J.
    et al.
    Yıldırım, H. C.
    Barsoum, Zuheir
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Fatigue strength assessment of TIG-dressed welded steel joints by local approaches2019In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 126, p. 72-78Article in journal (Refereed)
    Abstract [en]

    Fatigue strength assessment methods by local approaches are widely used in the literature. This paper provides a comprehensive evaluation of published data for welded steel joints improved by TIG dressing methods. Fatigue classes for the local assessment methods with the available fatigue data are recommended. The available fatigue data extracted for transverse non-load carrying welds, cruciform joints as well as butt joints. In total, 17 published test series of weld details with various yield strengths and stress ratios are presented. Fatigue strength assessment is performed by considering the weld profile geometry within Finite Element models and taking the resulting stress gradients as basis for the evaluation. In addition, the influence of the steel grade is included. The most reliable results are derived by using the critical distance approach. Fatigue classes and critical distances are recommended as a result of the evaluations.

  • 215.
    Bayer, Johannes
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    THE DUCKLING PROJECT: Design and manufacturing of autonomous surface vehicles for various application areas2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the times of big data analyses and fast robotic evolution, collecting data is an important part of science. Today we have only explored 5 percent of the ocean, which is less than we have explored Mars. To collect more data of the ocean we need tools, vehicles and equipment, which are designed and used by scientists.  In this technical report, the design of an autonomous surface vehicle (ASV) is described. An ASV is a floating vehicle that can conduct manoeuvres and actions autonomously. The ocean environment is in many senses difficult for technically operated vehicles, with the main reasons being high pressure, no possibility of radio communication and of course water, which always is a challenge when combined with water. The concept of this work is to provide a system which consists of four equal ASV units, who can perform different operations. The system should be capable of conducting different kinds of experiments with varying testing equipment. Two ideas have been considered: autonomous depth mapping of inshore areas and locating and following an acoustic source. These two possible scopes are used to find fitting and flexible requirements for the ASV. In the future, the four units should be used by different projects realised by students and researchers, therefore robustness in operation and usability are a main point of focus when determining the requirements.

  • 216.
    Bayle, Lucas
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Energy Absorption & Improvement Of 1/3 Disc Fragment Model For Turbofan Fan Stage In The Rotor Burst Analysis2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The 1/3 disc fragment model for fan disc burst shall allow aircraft manufacturers to minimize the hazards to the aeroplane without unnecessarily constraining its design. This paper presents a finite energy approach, along with its benefit assessment on the electrical segregation height and rapid decompression rotor burst design constraints. The fan case energy absorption is estimated through the AGARD impact mechanics formula, considering its capability to withstand fan blade-off events. The results for a standardized single-aisle engine suggest 34% energy absorption, 95mm minimum electrical segregation height decrease and 83% rapid decompression maximum opening decrease. The first estimation of energy absorption shows that it is unlikely that the fan retention belt would retain the 1/3 disc fragment. Assumptions regarding material failure, ring shape effect, and blade deformation energy absorption could be refined.

  • 217. Bačkalov, I.
    et al.
    Bulian, G.
    Cichowicz, J.
    Eliopoulou, E.
    Konovessis, D.
    Leguen, J. -F
    Rosén, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Themelis, N.
    Ship stability, dynamics and safety: Status and perspectives from a review of recent STAB conferences and ISSW events2016In: Ocean Engineering, ISSN 0029-8018, E-ISSN 1873-5258, Vol. 116, p. 312-349Article, review/survey (Refereed)
    Abstract [en]

    In Naval Architecture, the concept of "stability" has a very wide meaning, embracing ship stability fundamentals with ship dynamics and ultimately ship safety. As such, the subject is of paramount importance for its wide implications on design and operation of ships and floating units. Research in this field has, therefore, an important impact on the fleet safety, and the International Conferences on Stability of Ships and Ocean Vehicles (STAB Conferences) and the International Ship Stability Workshops (ISSW) are certainly the venues where expertise and contemporary developments in this specific field tend to be collected and thoroughly debated. With the aim of analysing the current status and possible future perspectives of research in the field of ship stability, dynamics and safety, this paper provides an extensive review of the findings presented at STAB Conferences and ISSW events in the period 2009-2014. The reviewed material is organised according to a set of identified macro-topics of research. On the basis of the reviewed material, consolidated research topics as well as emerging subjects are laid out, and ideas for possible future research are also brought forward. Discussion is also provided regarding the link between research and educational aspects.

  • 218. Bačkalov, I.
    et al.
    Bulian, G.
    Rosén, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Shigunov, V.
    Themelis, N.
    Improvement of ship stability and safety in intact condition through operational measures: Challenges and opportunities2016In: Ocean Engineering, ISSN 0029-8018, E-ISSN 1873-5258, Vol. 120, p. 353-361Article in journal (Refereed)
    Abstract [en]

    Attaining a sufficient level of safety from the point of view of stability is typically considered to be a matter of design. However, it is impossible to ensure safety only by design measures, and operational measures can then represent a complementary tool for efficiently and cost-effectively increasing the overall safety of the vessel. Time could therefore be coming for systematically considering operational measures as a recognised and regulated integral part of a holistic approach to ship safety from the point of view of stability. This paper therefore aims at capturing recent trends of research targeting operational safety measures, with specific attention to the intact ship condition. Open challenges and opportunities for research are identified, potential benefits and shortcomings of different options are discussed, and needs and possibilities for further developments in this area are explored. As an overall goal, this paper aims at providing food for thoughts as well as a ground for further proceeding towards the target of implementing a virtuous integrated approach to intact ship safety, from the point of view of stability, which gives due credit to effective and robust operational risk control options.

  • 219. BECKENBAUER, THOMAS
    et al.
    JEAN, PHILIPPE
    KROPP, WOLFGANG
    STEINAUER, BERNHARD
    UECKERMANN, ANDREAS
    SCHULZE, CHRISTIAN
    MEYER, ANDRE
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Fahrbahnbelag und Verfahren zur Herstellung desselben2008Patent (Other (popular science, discussion, etc.))
  • 220.
    Beltran Gutierrez, Javier
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Yujiao, Song
    Chalmers.
    Methods for Verification of Post-Impact Control including Driver Interaction2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis project focuses on the verification method of a safety function called PICthat stands for Post-Impact Control which controls the vehicle motion of passengercars after being exposed to external disturbances produced by a 1st impact, aiming atavoiding or mitigating secondary events.The main objective was to select a promising method, among several candidates, todevelop further for testing the function and the interaction with the driver. To do thisis was first necessary to map the real destabilized states of motion that are targeted bythe function. These states are referred as Post-Impact problem space and are acombination of variables that describes the host vehicles motion at the instant thedestabilizing force has ceased. Knowing which states are requested by the solutioncandidates, it is possible to grade the rig candidates based on the capability ofcovering the problem space. Then, simulating the proposed rig solutions withMatlab/Simulink models to investigate which candidate fulfils best the problem space.The result of the simulations and other criteria is that a moving base simulator(Simulator SIM4) is most fitted to research verification. The second mostadvantageous solution is the rig alternative called Built-in Actuators.

  • 221.
    BENETHUILLERE, Quentin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Revision Of The Aircraft Engines Preliminary Design Platform Of First Level2014Independent thesis Advanced level (degree of Master (Two Years)), 20 HE creditsStudent thesis
    Abstract [en]

    In the highly competitive aerospace industry, engine manufacturers must react very quickly and precisely to any demand emerging from aircraft manufacturers if they want to be positioned on the offer. This is especially true when answering to Requests For Information (RFI) based on preliminary design investigations of first level. In order to reduce the time needed to perform these costly operations while improving the performances achieved, Snecma wishes to develop tools for dimensioning the engine and also for assessing key parameters such as mass, emissions, fuel burn, costs, etc. Unfortunately, the set of tools and the process used at the present time for preliminary design investigations of first level are not sufficient to meet the high standards sought-after by the company in terms of time and performances. As a consequence, efforts must be spent on redefining the whole process and the tools it is based on; here is the mission that has been conferred upon me.

     

    Multiple exchanges with performances engineers and specialists allowed to draw the current process for preliminary design investigations of first level and raise all the associated concerns. At the same time, a status of the existing tools (called modules in this report), mainly developed under Excel, has been realised in order to identify the range of action for today's investigations. A prototype has been developed under SDK Python with the aim of proving the feasibility of a solution to a difficulty that shows up in the process for each new investigation: the one of generating the workflow on the optimisation software Optimus. A target process has finally been discussed considering all the information collected, and would allow dividing by five the time needed to perform investigations compare to now. The prototype developed lead to interesting results and this solution could thus probably be integrated in the target process as it would allow saving one day of work for an engineer for each study to be carried out.

     

    Solutions have been proposed to all the concerns identified in the process and they will have to be discussed with many actors and investigated further in the near future in order to set the target process that will allow meeting the final objective of answering all types of RFIs emitted by aircraft manufacturer in a very short time with a high level of confidence in the results.

  • 222.
    BENETHUILLERE, Quentin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Revision Of The Aircraft Engines Preliminary Design Platform Of First Level2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the highly competitive aerospace industry, engine manufacturers must react very quickly and precisely to any demand emerging from aircraft manufacturers if they want to be positioned on the offer. This is especially true when answering to Requests For Information (RFI) based on preliminary design investigations of first level. In order to reduce the time needed to perform these costly operations while improving the performances achieved, Snecma wishes to develop tools for dimensioning the engine and also for assessing key parameters such as mass, emissions, fuel burn, costs, etc. Unfortunately, the set of tools and the process used at the present time for preliminary design investigations of first level are not sufficient to meet the high standards sought-after by the company in terms of time and performances. As a consequence, efforts must be spent on redefining the whole process and the tools it is based on; here is the mission that has been conferred upon me.

     

    Multiple exchanges with performances engineers and specialists allowed to draw the current process for preliminary design investigations of first level and raise all the associated concerns. At the same time, a status of the existing tools (called modules in this report), mainly developed under Excel, has been realised in order to identify the range of action for today's investigations. A prototype has been developed under SDK Python with the aim of proving the feasibility of a solution to a difficulty that shows up in the process for each new investigation: the one of generating the workflow on the optimisation software Optimus. A target process has finally been discussed considering all the information collected, and would allow dividing by five the time needed to perform investigations compare to now. The prototype developed lead to interesting results and this solution could thus probably be integrated in the target process as it would allow saving one day of work for an engineer for each study to be carried out.

     

    Solutions have been proposed to all the concerns identified in the process and they will have to be discussed with many actors and investigated further in the near future in order to set the target process that will allow meeting the final objective of answering all types of RFIs emitted by aircraft manufacturer in a very short time with a high level of confidence in the results.

  • 223.
    Bengtsson, Karl
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    ThermoacousticInstabilities in a Gas Turbine Combustor2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Stationary gas turbines are widely used today for power generation and mechanical drive applications. The introduction of new regulations on emissions in the last decades have led to extensive development and new technologies used within modern gas turbines. The majority of the gas turbines sold today have a so called DLE (Dry Low Emission) combustion system that mainly operates in the leanpremixed combustion regime. The lean-premixed regime is characterized by low emission capabilities but are more likely to exhibit stability issues compared to traditional non-premixed combustion systems.

    Thermoacoustic instabilities are a highly unwanted phenomena characterized by an interaction between an acoustic eld and a combustion process. This interaction may lead to self-sustained large amplitude oscillations which can cause severe structural damage to the gas turbine if it couples with a structural mode. However, since a coupled phenomena, prediction of thermoacoustic stability is a complex topic still under research.

    In this work, the mechanisms responsible for thermoacoustic instabilities are described and a 1- dimensional stability modelling approach is applied to the Siemens SGT-750 combustion system. The complete combustor is modelled by so called acoustic two-port elements in which a 1-dimensional ame model is incorporated. The simulations is done using a generalized network code developed by Siemens. The SGT-750 shows today excellent stability and combustion performance but a deeper knowledge in the thermoacoustic behaviour is highly valued for future development.

    In addition, measurement data from an engine test is evaluated, post-processed and compared with the results from the 1-dimensional network model. The results are found to be in good agreement and the thermoacoustic response of the SGT-750 is found to be dominated by both global modes including all cans as well as local modes within the individual cans.

  • 224.
    Berg, Johan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Better design of wheel-loaded decks2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This study treats the design of secondary structures for wheel-loaded decks. It concludes that significant savings in structural weight, overall cost and environmental impact can be obtained by an improved design. The rules of three classification societies are examined and their principle differences are discussed. Weight and cost optimal solutions of rule-based design are identified for a deck of a typical short-sea RoRo-vessel. The rule-optimal designs are assessed and further improved on the basis of FEcalculations and the economic and environmental benefits associated with the best solutions are approximated.

  • 225.
    Berg, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Preface to special issue on the Green Train programme2014In: International Journal of Rail transportation, ISSN 2324-8378, E-ISSN 2324-8386, Vol. 2, no 1Article in journal (Refereed)
  • 226.
    Berg, Mats
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Stensson Trigell, AnnikaKTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Selected and extended papers from the 21st symposium of the International Association of Vehicle System Dynamics: held at the Royal Institute of Technology (KTH), Stockholm, Sweden, August 17-21, 20092010Conference proceedings (editor) (Refereed)
  • 227.
    Berg, Mats
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Stensson Trigell, AnnikaKTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Special Issue: State of the Art Papers of the 21st IAVSD Symposium2009Conference proceedings (editor) (Refereed)
  • 228.
    Berggren, Axel
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Dagens sjöfart.2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Denna rapport är resultatet av kandidatexamenskursen inom marina system på KTH i Stockholm. Kursen

    såväl som rapporten är indelad i tre delar.

    Del ett går ut på att skaffa sig en inblick i hur dagens handelsflotta ser ut, med allt som hör därtill. Till

    exempel olika fartygstyper, olika drivmedel, internationella miljökrav och varvsverksamheter med mera.

    Detta redovisas med hjälp av en essä om den internationella sjöfarten.

    Del två går ut på att projektera ett eller flera fartyg utifrån ett givet transportscenario. I detta fall handlar

    det om att transportera etthundra trailers mellan Gdansk i polen och Nynäshamn på ostkusten en gång

    per dygn ifrån respektive hamn. I denna del behandlas alltifrån skeppsstabilitet och lastutrymmen till

    lagkrav för internationell sjöfart och propellerarrangemang. Resultatet av denna del är tre identiska rorofartyg

    med en längd på 175 meter, en bredd på 21 meter och ett djupgående på 5,63 meter.

    Del tre och sista delen är resultatet av kursens fördjupningsdel, som även är det sista momentet i kursen.

    Denna fördjupning behandlar vad en interceptor har för inverkar på det totala motståndet för ett planande

    skrov. Motståndsberäkningar har gjorts då interceptorn använts för att trimma ett prismatiskt skrov till ett

    mer gynnsamt gångläge. Denna del behandla Savitskys metod kombinerad med empiriskt framtagna

    uttryck (Steen, 2007). Resultaten för denna fördjupning visar att det med denna metod inte går att använda

    en interceptor för att minska motståndet genom att trimma om båten och att den motståndsminskning det

    nya trimmet ger upphov till är mindre till beloppet än den motståndsökning som interceptorn ger upphov

    till.

  • 229.
    Berggren, Axel
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Lindh, Ebba
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    ICE LOADS AND RESISTANCES ON A SMALL COMMUTER VESSEL: A comparative study of rule based design and analytical ice loads and resistances2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of the thesis is to investigate what the results are when applying DNV ice class design rules on a vessel that falls outside the validity range and how it does compare to direct calculations. The vessel to be investigated is a smaller ice going commuter ferry intended for freshwater Lake Mälaren in Stockholm.

    Due to increased need of public transport in the area, political decisions have been made to incorporate ferry lines in the public transport system. The number of commuters’ peak during January and February and it is thus necessary to design a ferry that works all year around, in all possible weather conditions, including the ice conditions that occur winter time (Rindeskär, 2014).

    In order to make a comparative study of the DNV ice class and direct calculations with regards to resistances and structural loads on the hull, a general arrangement of the ferry is developed. Icebreaking resistance models based on DNV ice class (Det Norske Veritas, 2014), Riska (Riska, Willhelmson, Englund, & Leiviskä, 1997) and Lindqvist (Lindqvist, 1989) can be compared based on the ferry’s main data. The bow section of the hull is designed to handle the DNV design pressure according to DNV ice class 1C. The structural response is investigated using a finite element model, applying different load cases given from DNV as well as from the studied semi empirical ice load models mentioned above.

    The bow design is of great importance for the icebreaking performance and the speed. The greater the stem angles the higher the resistance. A large variation in the results was also noted as only Lindqvist’s model took the freshwater ice properties into account. Further measurements have to be made in freshwater for smaller vessels to validate the results.

    In the FE-analysis it was seen that the hull structure coped well with the DNV design pressure of 1 MPa. However, the empirical design pressure of 1.5 MPa resulted in too high stresses in the structure. The result indicates that the design rules work well for the intended design pressure, but the minimum empirical design pressure is still higher than the DNV design pressure for the commuter vessel. It can be that the DNV design rules can be used in the case of the ferry, but further investigations has to be made with regards to minimum design pressure.

    In general, the results can be used as a basis for further investigations in the field of vessels operating in freshwater ice conditions.

  • 230.
    Berggren, Eric
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    A new approach to the analysis and presentation of vertical track geometry quality and rail roughness2008In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 265, p. 1400-1496Article in journal (Refereed)
    Abstract [en]

    A new approach on enhancing the assessment of track geometry quality and rail roughness by means of train–track interaction simulation and wavelength content analysis is presented. The dynamic model includes vehicle, track and linearized wheel–rail contact with moving irregularities and can be simulated either in the frequency domain by using FFT or in the time domain by constructing a filter function based on system identification technique. The system is suitable to calculate wheel–rail forces for very long track sections and for several vehicle types under a wide range of travelling speeds since the computational scheme is very efficient (300 km/s on a standard computer). With numerical results we demonstrate the potential benefits of improving conventional track geometry inspection methods and highlight short defects (0.5–2 m) as a cause of high dynamic wheel–rail interaction forces. By using a wavelength weighting of measured rail roughness a new improved way of analyzing rail roughness data is also presented. This improves condition assessment of tracks and rails and will enable the track engineer to monitor the track in a better way.

  • 231.
    Berggren, Eric
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    A Study of the Effect of Global Track Stiffness and its Variations on Track Performance: Simulation and Measurement2009In: International Heavy Haul Conference: Shanghai 2009, 2009Conference paper (Refereed)
    Abstract [en]

    This paper investigates the effect of vertical track stiffness, and its variations along the track, on track performance with focus on dynamic responses of track due to parametric excitations. Two approachesfor calculating global track stiffness, a static one based on Zimmermann’s theory, and a dynamic one basedon the track model used in the dynamic vehicle-track interaction program DIFF, are discussed. A RollingStiffness Measurement Vehicle (RSMV) has been developed at Banverket and measurements have been carried out over hundreds kilometre long tracks. This paper presents a statistical analysis of the collected results and provides information of track stiffness and its variation on typical Swedish tracks.

  • 232.
    Berggren, Eric
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Dynamic track stiffness measurement: a new tool for condition monitoring of track substructure2005Licentiate thesis, comprehensive summary (Other scientific)
  • 233.
    Berggren, Eric
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efficient Track Maintenance -Methodology for Combined Analysis of Condition Data2009In: International Heavy Houl Conference: Shanghai 2009, 2009Conference paper (Refereed)
    Abstract [en]

    Measured condition data may contain lots of information which is not efficiently used. By usingtechniques from the field of pattern recognition, this paper outlines a methodology for eliciting newinformation. The methodology is demonstrated on a large set of condition data originating from trackgeometry quality, dynamic stiffness and ground penetrating radar. The case study gives evidence for theimportance of dynamic stiffness measurements as to determine soil and embankment related track problems,while problems originating from the upper part or the track structure do not benefit significantly.

  • 234.
    Berggren, Eric
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Measurements of track stiffness and track irregularities todetect short waved support conditions2006In: International Conference on Railway Track Foundatons, 2006Conference paper (Refereed)
    Abstract [en]

    Short waved vertical irregularities of the track can cause high dynamic train-track interactionforces. These forces cause several problems, for example deterioration of track geometry anddamage of components. Since these short irregularities also could be an important source ofpropagating waves and environmental vibration, different measurement and evaluation techniques have been investigated to detect and quantify these irregularities. The RMSV(Rolling Stiffness Measurement Vehicle) developed by Banverket has been used to verify thephenomenon of track stiffness variability. Variations of 5 – 20 kN/mm (2 – 10 %) betweenadjacent sleepers are common, and variations even up to 60 kN/mm (30%) have been detectedon a modern ballasted track. Also a new way of analysing longitudinal level, measured with atrack recording car (TRC), by filtering out only short waved irregularities makes it possible toindicate problems with hanging sleepers, variable sleeper support and other possible shortwaved irregularities. Even though the amplitude of these irregularities is low (around 0.5 – 1mm), their impact can be considerable.

  • 235.
    Berggren, Eric
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Monitoring and Substructure Condition Assessment of Existing Railway Linesfor Upgrading to Higher Axle Loads and Speeds2006In: 7th World Congress on Railway Research, 2006Conference paper (Refereed)
    Abstract [en]

    Many of the European railways have been designed for completely different traffic conditions than thoserequired today. Upgrading of existing railway lines for higher axle loads and speeds requires new modernmethods for in situ investigation of the railway ballast and substructure. Combination of continuousmeasurements of track geometry quality and non-destructive methods like dynamic track stiffness and Ground Penetrating Radar (GPR) can be a good example of obtaining the important information about theconditions of existing railways. A new methodology for evaluation of all available measurementscompleted with results from geotechnical investigations is proposed to study problems dealing with railway structure and subgrade in case upgrading or maintenance work is required.

    Railway investigations using Banverket´s Rolling Stiffness Measurement Vehicle (RSMV) equipped withGPR, and a methodology of comprehensive evaluation of all relevant available information have beentested on a few railway lines in Sweden since 2002. Results from these investigations are used forassessment of the root cause of existing or possible future problems with repeated track maintenance,settlement and stability when upgrading a track for higher axle load and/or speed.

    The paper presents practical results of investigations and a new methodology to evaluate several types ofmeasurements in comparison with real track – substructure conditions. Suggestions on upgradingactivities are given for a case study of 25 km of track with a planned increase of axle load from 22.5 to 25metric tons. The goal is to minimize the upgrading and maintenance cost in a Life Cycle Cost (LCC)perspective.

  • 236.
    Berggren, Eric
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Railway Track Stiffness: Dynamic Measurements and Evaluation for Efficient Maintenance2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Railway track stiffness (vertical track load divided by track deflection) is a basic parameter oftrack design which influences the bearing capacity, the dynamic behaviour of passing vehiclesand, in particular, track geometry quality and the life of track components. Track stiffness is abroad topic and in this thesis some aspects are treated comprehensively. In the introductionpart of the thesis, track stiffness and track stiffness measurements are put in their propercontext of track maintenance and condition assessment.

    The first aspect is measurement of track stiffness. During the course of this project, Banverkethas developed a new device for measurement of dynamic track stiffness called RSMV(Rolling Stiffness Measurement Vehicle). The RSMV is capable of exciting the trackdynamically through two oscillating masses above one wheelset. The dynamic stiffness is acomplex-valued quantity where magnitude is the direct relation between applied load anddeflection (kN/mm) and phase is a measure of deflection-delay by comparison with force. Thephase has partial relationship with damping properties and ground vibration. The RSMVrepeatability is convincing and both overall measurements at higher speeds (up to 50 km/h)and detailed investigations (below 10 km/h) can be performed. The measurement systemdevelopment is described in Paper A and B.

    The second aspect is evaluation of track stiffness measurements along the track from a trackengineering perspective. Actual values of stiffness as well as variations along the track areimportant, but cannot always answer maintenance and design related questions alone. InPaper D track stiffness is studied in combination with measurements of track geometryquality (longitudinal level) and ground penetrating radar (GPR). The different measurementsare complementary and a more reliable condition assessment is possible by the combinedanalysis. The relation between soft soils and dynamic track stiffness measurements is studiedin Paper C. Soft soils are easily found and quantified by stiffness measurements, in particularif the soft layer is in the upper part of the substructure. There are also possibilities to directlyrelate substructure properties to track stiffness measurements. Environmental vibrations areoften related to soft soils and partly covered in Paper C. One explanation of the excitationmechanism of train induced environmental vibrations is short waved irregular supportconditions. This is described in Paper E, where track stiffness was evinced to have normalvariations of 2 – 10 % between adjacent sleepers and variations up to 30 % were found. Anindicative way of finding irregular support conditions is by means of filtering longitudinallevel, which is also described in the paper. Train-track interaction simulation is used in PaperH to study track stiffness influence on track performance. Various parameters of trackperformance are considered, e.g. rail sectional moment, rail displacement, forces at wheel-railinterface and on sleepers, and vehicle accelerations. Determining optimal track stiffness froman engineering perspective is an important task as it impacts all listed parameters.

    The third aspect, efficient maintenance, is only partially covered. As track stiffness relates toother condition data when studied from a maintenance perspective, vertical geometricaldefects (longitudinal level and corrugation/roughness) are studied in paper F. The generalmagnitude dependency of wavelength is revealed and ways of handling this in conditionassessment are proposed. Also a methodology for automated analysis of a large set ofcondition data is proposed in Paper G. A case study where dynamic track stiffness,longitudinal level and ground penetrating radar are considered manifests the importance oftrack stiffness measurements, particularly for soil/embankment related issues.

  • 237.
    Berggren, Eric
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Berg, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Simulation, Development and Field Testing of a Track StiffnessMeasurement Vehicle2005In: 8th Interntaional Heavy Haul Conference, Rio de Janeiro, 2005Conference paper (Refereed)
    Abstract [en]

    A new vehicle for continuous measurement of vertical track stiffness has been built by Banverket. Two oscillatingmasses of the vehicle excite the track dynamically and the track stiffness is calculated from measured axle box forces andaccelerations. The stiffness is given as a complex quantity and presents both the magnitude and the phase. The repeatability isvery good, and some promising results for soft subsoils are shown. Both overall measurements at higher speeds (up to 60km/h) and detailed investigations (below 10 km/h) can be performed.

  • 238.
    Berggren, Eric
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Kaynia, Amir
    Dehlbom, Björn
    Identification of Substructure Properties of Railway Tracks by Dynamic Stiffness Measurements and Simulations2010In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 329, no 19, p. 3999-4016Article in journal (Refereed)
    Abstract [en]

    A new vehicle has been developed to measure dynamic vertical track stiffness while in motion. This technique allows the resonance behaviour of the track below 50 Hz to be measured. Soft soils like clay and peat are the main causes of resonance below 20 Hz. By means of simulation studies with the software VibTrain, soft soil resonance behaviour may be characterized using a few key parameters originating from track stiffness measurements, such as the minimum phase delay and corresponding frequency of the receptance transfer function. Statistical models are built to relate these key parameters with substructure properties, such as embankment thickness, shear wave velocity and thickness of the soft soil layer using pattern recognition methods. Two case studies are used to show the methodology, and the results are verified using Ground Penetration Radar (GPR) measurements and borehole investigations. Models are also developed from the statistical relationship between GPR-data and stiffness measurements. It is shown that embankment thickness is the easiest quantity to estimate, but indicative results are also presented for the other quantities (shear wave velocity and thickness of soil layer).

     

  • 239.
    Berglund, Johan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Utvärdering av ny utrustning för modalprovning2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report evaluates new equipment for model testing, and also the design of an EXE program created using Labview. The existing equipment was a Dytran 3032A accelerometer, a Dytran 5800A2 impulse hammer, two Dytran 4105C ampli˝ers, a Microstar Laboratories MSXB 042 quick-connect card, and one Microstar Laboratories iDSC 1816 data acquisition card, connected to a computer using the operating system Windows 2000 where the program Matlab 6.1 was used for data collection and Fourier transformation.A feasibility study was carried out with a National Instruments 9201 cDAQ data acquisition module mounted into a National Instruments 9174 cDAQ chassis using the existing impulse hammer and accelerometer, where a simple prgram in Labview 2014 was made.Given the price and compatibility with the existing impulse hammer, accelerometer and other systems within the laboratory, a National Instruments 9234 cDAQ data acquisition module installed in a National Instruments 9171 cDAQ chassis was selected, combined with a PC using the operating system Windows 7 and running an EXE application created in Labview 2014 and 2011 for data collection and Fourier transforming. The older equipment was left intact as far as possible as a reserve.

  • 240.
    Berglund, Lars
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Ansari, Mohd Farhan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Cellulose nanocomposites with ductile mechanical behavior2015In: ICCM International Conferences on Composite Materials, International Committee on Composite Materials , 2015Conference paper (Refereed)
    Abstract [en]

    The limited ductility of plant fiber biocomposites is typically caused by interfacial debonding mechanisms at low strain. This leads to damage development and premature failure. The present paper discusses recent results on cellulose nanocomposites with thermoset and thermoplastic matrices, where substantial ductility is observed. The data are presented and reasons for the observed ductility are discussed. 

  • 241.
    Berglund, Per-Olof
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    An application of the noise synthesis technology (NST) to a system with an axial fan2002In: Forum Acustica 2002, Seville, Spain, 2002Conference paper (Refereed)
  • 242.
    Bergman, David
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Study of the coupled interaction between the wake’s transient behavior and pressure surfaces upstream using Detached Eddy Simulation2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aerodynamic sub-discipline of flow control has for many years been, and still is today, a very prominent subject of research. This field encompasses devices that produce a beneficial change in wall-bounded or free shear flows that may lead to, among many possibilities, reduced drag of ground vehicles and airplanes. The end result could have a substantial improved impact on fuel economy and also introduce new possible design options.

    Creo Dynamics AB recently started to venture into the field of active flow control with huge interest for the technology and its possible applications. One such application includes a system that reduces drag on ground vehicles via the use of active flow control. The system is composed of three components: actuators, controller and sensors. The work carried out in this thesis deals with a study into the sensory placement and control approach related to the system on a very conceptual level.

    According to Creo’s vision of the project the sensor shall record the pressure distribution and characteristics up-stream of the actuators. In turn the algorithm shall be capable of translating and correlating this data to the flow state downstream

    and in the wake. This data is then to be relayed to a control system producing the correct actuation response to achieve desired flow characteristics. For this system to work knowledge about the coupling between wake behavior and pressure distribution on surfaces upstream of the separated flow is necessary. This thesis is an initial investigation into the possible couplings that can be found. The scope also includes investigation of the coupling during cross-winds and gusts.

    Simulations of a simplified car geometry were carried out using the CFD package OpenFOAM and the DDES turbulence model. The initial investigation yielded promising results, showing that a link between the wake behavior and pressure distribution up-stream exists. But further work has to be carried out, as is discussed in the last chapter, before the algorithm according to Creo’s specifications can be constructed.

  • 243.
    Bergsek, Mattias
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    THRUST PREDICTION PROGRAM FOR MARINE JET POWER2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Marine Jet Power, MJP wishes to investigate the possibility of transforming their current Thrust Prediction Program, TPP written in C++ source code into a more up to date tool for their sales staff. The old TPP, though an accurate and precise tool, is not documented and lacks commentaries in the source code. Therefore the beginning of this master thesis was about documenting and investigates what methods were used to calculate the performance of the water jet system.The next step was splitting the long C++ source code in to smaller functions, this was done using MatLab where several m-files were created with the different functions in. C++ syntax and structure differs from MatLab so the source code must be translated in to MatLab syntax. Once the new TPP was translated and the calculation results were identical with the old TPP a Graphical User Interface, GUI was created and presented to MJP. The current MatLab TPP is not finished, only two of four calculation modes have been translated and MJP wants modifications in the GUI. The additional work needed in order to have the sales tool MJP wishes is currently discussed.

  • 244.
    Bergstedt, Robin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Aero-Design of Aerodynamically Lifting Struts for Intermediate Compressor Ducts2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Increasing demands on the performance and sustainability of modern turbofan engines put high requirements on each system component, and the limit of what is possible is expected to continue to extend. This thesis focuses on studies on the so-called turning struts concept which aims to shorten the compressor module of a future turbofan engine by introducing aerodynamically modified struts in the compressor mid-frame. Through CFD analysis and low-speed experimental evaluations, this concept is further developed with promising results attained in its early design stages. Important aerodynamic aspects related to this concept are highlighted, and appropriate conceptual design approaches are discussed. It was found that the length of the intermediate compressor duct could be reduced by up to 20% by eliminating the need for the last stator row in the upstream compressor, whilst providing comparable or improved performance compared to conventional designs.

  • 245.
    Bergstedt, Robin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    The Rocket SLS System - A Self Launch sailplane System Concept Analysis.2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 246.
    Bergström, Rasmus
    et al.
    KTH.
    Crimella, Matteo
    KTH.
    Ivchenko, Nickolay
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Karlsson, Alexander
    KTH.
    Lindberg, Hannah
    KTH.
    Persson, Linnea
    KTH.
    Schlatter, Nicola
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Tibert, Gunnar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Westerlund, Simon
    KTH.
    SCATTERING OF RADAR WAVES ON AEROSOLS IN PLASMAS2015In: EUROPEAN ROCKET AND BALLOON: PROGRAMMES AND RELATED RESEARCH, 2015, p. 87-94Conference paper (Refereed)
    Abstract [en]

    To study the physical mechanisms of phenomena such as polar mesospheric summer echoes, the SCRAP (Scattering of Radar waves on Aerosols in Plasmas) experiment aimed to validate theories on density fluctuations in dusty plasmas. The SCRAP team developed two identical free falling units (FFUs) designed to create a cloud of copper particles once they eject from the REXUS17 sounding rocket 124 seconds after launch. By using the EISCAT incoherent scatter radar system to observe the cloud, the SCRAP experiment proposed to relate theoretical predictions to a controlled object. The SCRAP experiment was launched from ESRANGE on March the 17th 2015. The FFUs GPS signal was lost during launch and the units were therefore not found. Moreover, no backscattering from the copper cloud was observed by the radar.

  • 247.
    Bergwall, Robert
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Sandwich design of a lift plate for tail lift platforms for cargo trucks2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis examines a sandwich lift plate for cargo trucks in order to propose an option for existing lift platforms in aluminium or steel. The wish is to make it lighter but not less stiff or weak. Two different cores in Divinycell with different density; H130 and H250 is examined. Calculations are made with respect to deflection and max stress in both core and faces for the whole plates. But also more local calculations are performed to see how the faces and core behaved on local point loads from pallet lift wheels.

    The analytical results successfully meet the deflection requirements causing only 30 mm deflection in the worst scenario with 33% overload on a lift plate built up by 3 mm aluminium faces and H130 Divinycell core measuring a total (incl. faces) 20 mm thickness in the top. Nor did the von Mises stresses exceed 50% of ultimate strength for the aluminium parts or the Divinycell core. The choice between the lighter (H130) and heavier (H250) core only appears to affect the deflection 1-2 mm and the von Mises face stress for point loads are in the order of 10 MPa.

    The objective regarding the mass of the lift plate was not met. This is however a matter of further optimisation and is considered to be solved.

  • 248.
    Berhane, Joel
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Emil, Godonou
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Analysis and modeling of child mortality.2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Child mortality has always been a strong indicator on the general wealth of a country therefore was decreasing it in the world one of the millennium goals. Since child mortality is such an important measure we have decided to make a structural model of it. This is an investigation regarding the causes of child mortality.

    The definition of child mortality is the number of children that died before the age of five. Not to be mixed with infant mortality which is a measure of those who died before the age of one. In contrast to infant mortality we think that child mortality strongly depends on other factors than just sickness, that’s why we chose to investigate child mortality among the two of them.

    We emanated from the assumption that it was possible to describe child mortality with the model:

    Y=Xβ+e

     

    With that in mind we collected data from the UN and the World Bank for child mortality and all possible factors that could affect child mortality.

    The analysis is made with the method "multiple linear regression". At the end it all came down to a structural model consisting of six explanatory variables which are:

    • U-nation

    • GNI in PPP-terms

    • Improved sanitation

    • Average precipitation

    • Help organization

    • Colony

    All of these variables got a positive coefficient in their effect on child mortality except for "GNI in PPP-terms" and "improved sanitation" which rationally got a negative sign. We also made a model which could be used for predicting child mortality. The difference between the prediction model and the structural model is the variable birthrate which is included in the prediction model but not in the structural model. In the prediction model birthrate got a positive sign.

  • 249.
    Bernebrant, Sarah
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Topologioptimering av skruvförband2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The software development for structural optimization has during the last decades been under constant development and improvement. The advantages of lighter structures with higher strength calls for better methods and tools for simulation and analysis in the design process.

    Topology optimization is a kind of structural optimization which focus on finding the optimal shape given a certain volume and design domain. This master thesis will deal with topology optimization of bolted joints. Bolts often carry high loads in a structure and it is crucial that they do not loosen or brake. At Scania, a method for simulation of bolted joints already exists using the software SIMULIA Tosca Structure 8.1.0. This year, Altair has launched a new application which also simulates bolts in their topology optimization software solidThinking Inspire which is also used at Scania.

    This new function is analysed and evaluated in order to see how it stands against the more established Tosca for a cylinder mount containing two bolts. After the topology and stresses in the structure and bolts have been analysed for both cases the conclusion is that the new function in solidThinking Inspire 2016 gave a trustworthy result.

    To solve remaining issues, such as even load distribution, the second part of this master thesis begins. Here, a new method for modelling bolts with constraints in solidThinking Inspire 2016 will be discussed. The study was proven to lessen the load distribution among the bolts and the magnitude of the forces in the bolts was reduced. The method can also be used in order to get an indication of how the bolts should be positioned, which bolts should be included in the design and which could be removed.

  • 250.
    Berquand, Audrey
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    EXPERIENCE FROM THE STUDENT PROGRAMME REXUS/BEXUS: A STEPPING STONE TO A SPACE CAREER2015In: EUROPEAN ROCKET AND BALLOON: PROGRAMMES AND RELATED RESEARCH, 2015, p. 63-67Conference paper (Refereed)
    Abstract [en]

    The aim of this paper is to give an inside view to the REXUS/BEXUS programme from the perspective of a student who has been involved in the project. Each year, the German Aerospace Center (DLR) and the Swedish National Space Board (SNSB), in cooperation with the European Space Agency (ESA), offer the opportunity to European University Students to fly an experiment on board sounding rockets or stratospheric balloons in the frame of the REXUS/BEXUS programme. From December 2012 to May 2014 a team of master students from KTH, the Royal Institute of Technology, worked on ISAAC project, an atmospheric experiment launched on board REXUS 15. The author was part of this student team and was involved in the whole process of the ISAAC project from design building and testing phases to the launch campaign and results analysis. The points raised in this article were presented on the occasion of a keynote speech during the 22nd ESA Symposium on European Rocket and Balloon Programmes and Related Research, in Tromso (Norway) from the 7th to the 12th of June 2015. The aim of this presentation was to demonstrate the benefits of hands-on Education programme at University level. In addition to the research opportunities, future space engineers and scientists can profit from a first practical experience under the supervision of experimented experts. The results of the ISAAC project were also presented in the frame of this conference [1].

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