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  • 1.
    Andersson, Andreas
    et al.
    KTH, Superseded Departments, Mechanics.
    Malm, Richard
    KTH, Superseded Departments, Mechanics.
    Measurement evaluation and FEM simulation of bridge dynamics2004Independent thesis Basic level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this thesis is to analyse the effects of train induced vibrations in a steel Langer beam bridge. A case study of a bridge over the river Ljungan in Ånge has been made by analysing measurements and comparing the results with a finite element model in ABAQUS. The critical details of the bridge are the hangers that are connected to the arches and the main beams. A stabilising system has been made in order to reduce the vibrations which would lead to increased life length of the bridge.

    Initially, the background to this thesis and a description of the studied bridge are presented. An introduction of the theories that has been applied is given and a description of the modelling procedure in ABAQUS is presented.

    The performed measurements investigated the induced strain and accelerations in the hangers. The natural frequency, the corresponding damping coefficients and the displacement these vibrations leads to has been evaluated. The vibration-induced stresses, which could lead to fatigue, have been evaluated. The measurement was made after the existing stabilising system has been dismantled and this results in that the risk of fatigue is excessive. The results were separated into two parts: train passage and free vibrations. This shows that the free vibrations contribute more and longer life expectancy could be achieved by introducing dampers, to reduce the amplitude of the amplitude of free vibrations.

    The finite element modelling is divided into four categories: general static analysis, eigenvalue analysis, dynamic analysis and detailed analysis of the turn buckle in the hangers. The deflection of the bridge and the initial stresses due to gravity load were evaluated in the static analysis. The eigenfrequencies were extracted in an eigenvalue analysis, both concerning eigenfrequencies in the hangers as well as global modes of the bridge. The main part of the finite element modelling involves the dynamic simulation of the train passing the bridge. The model shows that the longer hangers vibrate excessively during the train passage because of resonance. An analysis of a model with a stabilising system shows that the vibrations are damped in the direction along the bridge but are instead increased in the perpendicular direction. The results from the model agree with the measured data when dealing with stresses. When comparing the results concerning the displacement of the hangers, accurate filtering must be applied to obtain similar results.

  • 2.
    Bagampadde, Umaru
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Investigations on moisture damage-related behaviour of bituminous materials2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This doctoral thesis presents results of literature review on classical and contemporary aspects of stripping, as well as experimental investigations on moisture damage as influenced by bituminous materials.

    Previous research in the area of moisture damage was reviewed and synthesized into a state-of-the-art. Important parameters linked to moisture sensitivity, like bituminous material characteristics, dynamic loads from heavy vehicles, environmental factors, construction practice and nature of anti-stripping additives, are presented. The state-of-the-art in current test methods is summarized and given.

    The experimental work involved investigations of the influence of bitumen and aggregate composition on water susceptibility. The influence of aggregate mineralogy and chemistry was evaluated using eleven aggregates and one bitumen, followed by studying the interactive effect of four bitumens and four aggregates. Moisture sensitivity was evaluated in accordance with (EN 12697-12:2003) for conditioning, ASTM D 4123 for resilient modulus determination, and (EN 12697-23:2003) for indirect tensile strength testing. Furthermore, thermal stability of two liquid amine anti-stripping additives mixed with two bitumens of varied acidity was investigated using potentiometric titration and Fourier Transform Infrared (FTIR) Spectroscopy. Lastly, a technique based on Fourier Transform Infrared Spectroscopy-Attenuated Total Reflectance (FTIR-ATR) was developed and used for studying transport of water across thin bitumen films, as well as stripping at bitumen/substrate interfaces. Bitumens from different sources and three substrates (silicon, germanium and zinc selenide crystals) were used. Based on the results obtained, it was concluded that aggregates containing sodium and potassium in alkali feldspars generally showed high moisture sensitivity. In contrast, presence of calcium, magnesium and iron was associated with aggregates with low moisture sensitivity. Contrary to several previous findings, one aggregate with practically 100% quartz exhibited low moisture sensitivity. No linear relationship between moisture sensitivity and the contents of SiO2 and Al2O3 in the aggregates studied was established. Results of the interactive influence of bitumen and aggregate composition showed that high acid and low penetration bitumens exhibited high dry strength for all the aggregates studied. On the other hand, for a given bitumen, the wet strengths were found to be aggregate specific.

    The results of tests on thermal stability of amine additives showed that usefulness of these additives reduces considerably, when the more alkaline additive was mixed with the high acid bitumen, followed by storing the blends under pronounced conditions of time and temperature (24 hours and 140ºC, or more, in this study). Much less interaction occurred when the less alkaline additive was blended with the low acid bitumen. Even if a correlation was found between the results of potentiometric titration and Fourier Transform Infrared spectroscopy, the latter was not considered good enough at detecting amine additives, especially at low dosages.

    The technique based on FTIR-ATR developed in this study distinguished between good and bad bitumens with regard to stripping. The effectiveness of amine-based additives in reducing stripping was also shown by the method. Three likely processes occurred during the test, namely water diffusion, film break, and displacement (stripping) of bitumen from the substrate surface. The results also indicated that the diffusion process of water into the bitumen/substrate interface does not obey Fick’s law.

  • 3.
    Bagampadde, Umaru
    et al.
    Faculty of Technology, Makerere University, Kampala.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Characterization of chemical reactivity of liquid antistripping additives using potentiometric titration and FTIR spectroscopy2006In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 20, no 5, p. 2174-2180Article in journal (Refereed)
    Abstract [en]

    Chemical reactivity of two liquid antistripping additives mixed with two bitumens of diverse acid numbers was evaluated. Additives present in the blends were detected by use of potentiometric titration and infrared spectroscopy. Tests were done at dosages of 0, 0.5, 1.0, and 2.0%; storage temperatures of 25, 100, 140, and 150 degrees C; and storage times of 1, 24, and 72 h. At 0.5% dosage, close to typical field values, the more basic additive mixed with bitumen of high acid number almost ceased to be detected after 24 h of storage at 140 degrees C. The less basic additive could be detected beyond these conditions, irrespective of the bitumen used. At higher dosages, reactions with the bitumens were found to be more pronounced with the more basic additive. The reactions between the additives and bitumens studied seemed to be higher in the bitumen with higher acid number, irrespective of the dosage. Statistical analysis indicated that all the parameters studied significantly affected change in amount of additives detected in the blends. A correlation was established between potentiometric titration and infrared spectroscopy in detecting amine additives. This correlation notwithstanding, infrared spectroscopy was found to not be a good tool for measuring amines in the blends, especially at low concentrations.

  • 4.
    Bagampadde, Umaru
    et al.
    KTH, Superseded Departments, Civil and Architectural Engineering.
    Isacsson, Ulf
    KTH, Superseded Departments, Civil and Architectural Engineering.
    Kiggundu, Bob
    KTH, Superseded Departments, Civil and Architectural Engineering.
    Classical and contemporary aspects of stripping in bituminous mixtures2004In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 5, no 1, p. 7-45Article in journal (Refereed)
    Abstract [en]

    Stripping or removal of bitumen from an aggregate because of water penetrating into the interface causes many pavements to fail. Stripping has been existent since the advent of paving technology. It causes functional weakening of pavements leading to costly repairs. This state-of-the-art paper deals with important concepts of stripping as, bitumen chemistry and rheology, aggregate properties (chemical and mineralogical composition, surface texture, morphology, porosity, etc), traffic, water properties, construction practices (mixing, placement and in-service drainage) and nature of antistripping additives. Adhesion of bitumen onto aggregate is explained based on theories like mechanistic tenacity, molecular orientation, chemical reaction, and thermodynamic balance of interfacial forces. Stripping is elucidated using several mechanisms namely, displacement, detachment, spontaneous emulsification, bitumen film rupture, water pore pressure, hydraulic scouring, chemical disbanding, microbial activity, osmosis; and blistering and pitting. Attendant theories to the mechanisms are explained. Moisture sensitivity test methods emerged are described and discussed. The large number of tests that have evolved shows the importance of the phenomenon of stripping. Remedial measures which include use of antistripping additives, careful selection of hot mix component materials, good construction practice, and others have been proposed for use in practice.

  • 5.
    Bagampadde, Umaru
    et al.
    Makerere University, Kampala.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Kiggundu, Bob
    Makerere University, Kampala.
    Impact of bitumen and aggregate composition on stripping in bituminous mixtures2006In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 39, no 287, p. 303-315Article in journal (Refereed)
    Abstract [en]

    The impact of bitumen and aggregate composition on stripping was investigated using four bitumens and four aggregates. Moisture sensitivity was assessed based on retained resilient modulus and tensile strength ratio (MRR and TSR, respectively). The results indicate that mixtures from the bitumen with a high acid number exhibited high resilient modulus and tensile strength in the dry condition for all the aggregates. In wet condition, this conclusion did also hold except for one aggregate. Regarding penetration grade, mixtures made with lower penetration grade bitumen exhibited higher resilient modulus and tensile strength, in dry and wet conditions, than those of higher penetration grade. Bitumen characteristics like acid number, penetration grade and molecular size distribution did not influence moisture sensitivity. Mixtures with aggregates containing alkali metals (sodium and potassium) exhibited relatively high moisture sensitivity, regardless of the bitumen used. In contrast, indications of moisture sensitivity were not apparent in mixtures made with aggregates containing calcium, magnesium and iron. Data analysis revealed that variability in moisture sensitivity is attributed to aggregate rather than bitumen. No significant interaction effect between bitumen and aggregate was found on moisture sensitivity. The results indicated good correlation between MRR and TSR in ranking mixtures for stripping.

  • 6.
    Bagampadde, Umaru
    et al.
    Makerere University, Kampala.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Kiggundu, Bob
    Makerere University, Kampala.
    Influence of aggregate chemical and mineralogical composition on stripping in bituminous mixtures2005In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 6, no 4, p. 229-239Article in journal (Refereed)
    Abstract [en]

    The influence of aggregate chemical and mineralogical composition on moisture sensitivity was investigated using 11 aggregates from typical tropical and temperate climates and one bitumen. Mix design and compaction were based on Swedish Road 94 hot mix base specifications and moisture damage was determined using resilient modulus and tensile strength ratios. As much as practically possible, air voids, gradation, compaction level, bitumen content and curing were controlled. Mixtures from aggregates containing sodium and potassium exhibited relatively high moisture sensitivity. The converse was apparent for aggregates with calcium, magnesium and iron. No significant correlation was observed between the strength ratios and contents of Al2O3 and SiO2. Stripping was generally high for aggregates with quartz and alkali feldspars, although one aggregate with practically 100% quartz showed low moisture sensitivity. Statistical analysis showed good correlation between resilient modulus and tensile strength ratios.

  • 7.
    Barsoum, Zuheir
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. Khalifa University.
    Bhatti, Ayjwat
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Balawi, S.
    Computational Weld Mechanics - Towards a Simplified and Cost Effective Approach for Large Welded Structures2015In: Procedia Engineering, 2015, p. 62-69Conference paper (Refereed)
    Abstract [en]

    The current paper presents the development of a finite element analysis framework for computational weld mechanics, in order to carry out cost-effective predictions of welding induced residual stresses with good accuracy. Different approaches for describing the welding heat sources were investigated. The paper also investigates the influence of thermo-mechanical material properties of frequently used steel grades (S355-S960) on welding residual stresses and angular distortion. The predicted residual stresses were validated experimentally on several different small scale specimens with X-ray diffraction techniques. Finally, the developed simulation framework is demonstrated on complex welded structures in a construction equipment vehicle.

  • 8.
    Birkie, Seyoum Eshetu
    et al.
    KTH.
    Kurdve, M.
    Bellgran, Monica
    KTH.
    Korhonen, Jouni
    KTH.
    Implementation challenges affecting the environmental improvement performance in pharmaceutical production: Results of a green kaizen pilot2018In: IFIP WG 5.7 International Conference on Advances in Production Management Systems, APMS 2018, Springer-Verlag New York, 2018, Vol. 535, p. 58-66Conference paper (Refereed)
    Abstract [en]

    This paper reports on working findings in an action research-based project, implementing a green kaizen pilot in a European pharmaceutical manufacturing company. The aim of the study is to investigate how continuous improvement initiatives with focus on environment originally developed for the automotive manufacturing industry could apply to the pharmaceutical industry. It also aspires to understand the enabling and hindering issues are for such implementation. There are considerable similarities of implementing lean in general in the two sectors, however, some key differences and challenges were apparent when implementing this specific green kaizen method called Green Performance Map. An implication for pharma practitioners implementing the green kaizen method concerns how to improve working procedures and production equipment to become more environmentally friendly amid high regulatory demands on process quality. Implementation challenges are discussed in terms of fidelity, locus and extensiveness of lean practices implementation.

  • 9.
    Björkblad, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Conventional vs. closure free crack growth in nodular iron2005In: Competent Design by Castings: Improvements in a Nordic Project / [ed] Samuelsson J, Marquis G, Solin J, Valtion Teknillinen Tutkimuskeskus , 2005, p. 273-286Conference paper (Refereed)
    Abstract [en]

    This investigation deals with the fatigue properties and material parameters for a silicon alloyed nodular cast iron. The material follows the Swedish standard SS 140725. The objectives for this investigation where to evaluate properties of the material in a fracture mechanic sense of view. In this part, the attention was paid to the basic fracture mechanic properties, i.e. da/dN-curves and Pan's law parameters. It also include R-dependence behaviour evaluated for R-values from R= 0 and R= 0.8. The main incitement for using the closure free approach is that it produces the fastest crack propagation rate that can be found at given conditions and load levels. This investigation of nodular iron will be followed by subsequent parts. The investigation in total is a part of the nordic project "Cast Design 2005".

  • 10.
    Björkblad, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Fatigue assessment of cast components2005Licentiate thesis, comprehensive summary (Other scientific)
  • 11.
    Björkblad, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Fracture mechanics evaluation of a nodular cast iron component by 3d modelling2005In: Competent Design by Castings: Improvements in a Nordic Project / [ed] Samuelsson J; Marquis G; Solin J, 2005, Vol. 237, p. 351-374Conference paper (Refereed)
    Abstract [en]

    The object of this paper was fracture mechanic modelling of solids using finite element (FEM). The main tool that has been utilized was the software Mcrack which is a group of macros intended for use jointly with ANSYS finite element program. One major advantage of the Mcrack software is that it supports solid modelling with a crack located at an arbitrary location. This implies that it is possible to calculate also torsion and mixed mode cases within a most reasonable work effort. However, Mcrack was developed to cover complex weld geometries. Utilizing Mcrack for general solid modelling requires an analysis of the possibility of development for arbitrary crack paths. As test object a cast sleeve made of nodular iron has been used. Previous to this investigation the component was submitted to a test program and a subsequent evaluation according to S/N criteria's at ABB, Sweden. This paper is thus a continuation of the ABB work, and at the same time an extension of the field of application for the Mcrack software. For validation purposes the software AF-Grow as well as elementary cases has been used in parallel. The investigation is a part of the nordic project "Cast Design 2005".

  • 12.
    Björkblad, Anders
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    On the prediction of crack propagation in cast steel specimens2004In: 9th Portuguese Conference on Fracture, 2004Conference paper (Refereed)
    Abstract [en]

    This investigation deals with the fatigue behaviour of cast steel with respect to defects, crack initiation, crack growth and material parameters. It constitutes the initial part of a larger work in cast materials. The main objectives have been to validate calculations made by FEM and Paris law with data from fatigue tests and to confirm material parameters for Pan's law. Furthermore, the results where put against calculations obtained from the fracture mechanic software AF-GROW. During the accomplishment some difficulties was experienced concerning the initiation of the crack, with result that there where just a few specimens suitable for evaluation by LEFM. However, some conclusions concerning the crack growth behaviour could yet be done. The results in general showed good correspondence, the results from AF-GROW included. Most divergences could be explained by residual stresses and, to some extent, the initiation problems.

  • 13.
    Brännmark, Mikael
    et al.
    KTH, School of Technology and Health (STH), Ergonomics.
    Langstrand, Jostein
    Linköping University, Division of Quality Technology and Management, Linköping, Sweden.
    Johansson, Stina
    Luleå University of Technology, Dept. of Human Work Science, Luleå, Sweden.
    Halvarsson, Agneta
    Linköpings universitet, HELIX VINN Excellence Centre.
    Abrahamsson, Lena
    Luleå University of Technology, Dept. of Human Work Science, Luleå, Sweden.
    Winkel, Jörgen
    University of Gothenburg, Dept. of Sociology and Work Science, Gothenburg, Sweden.
    Researching lean: Methodological implications of loose definitions2012In: Quality Innovation Prosperity, ISSN 1335-1745, E-ISSN 1338-984X, Vol. 16, no 2, p. 35-48Article in journal (Refereed)
    Abstract [en]

    Recently, Lean Production (Lean) has become a prevailing management concept in Sweden. However, previous research seems to show that the Lean concept and the impact of Lean vary considerably between organizations.

    This paper illustrates some key methodological issues that need to be considered when researching loosely defined management concepts such as Lean. The paperis based on a review of the literature and five comparative Swedish cases studies.

    Our study indicates that Lean has changed over time and that operationalization and interpretations of the concept vary considerably

    This study concludes that future Lean studies should include a thorough assessment of the Lean interventions, study settings, and in particular non-Lean factors mediating the outcomes of Lean-inspired change programs.

  • 14.
    Cameron, Christopher John
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Design of Multifunctional Body Panels for Conflicting Structural and Acoustic Requirements in Automotive Applications2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Over the past century, the automobile has become an integral part of society, with vastincreases in safety, refinement, and complexity, but most unfortunately in mass. Thetrend of increasing mass cannot be maintained in the face of increasingly stringentregulations on fuel consumption and emissions.The body of work within this thesis exists to help the vehicle industry to take a stepforward in producing vehicles for the future in a sustainable manner in terms of botheconomic and ecological costs. In particular, the fundamentally conflicting requirementsof low weight and high stiffness in a structure which should have good acousticperformance is addressed.An iterative five step design method based on the concepts of multifunctionality andmultidisciplinary engineering is proposed to address the problem, and explained witha case study.In the first step of the process, the necessary functional requirements of the systemare evaluated. Focus is placed on the overall system behavior and diverted from subproblems.For the case study presented, the functional requirements included: structuralstiffness for various loading scenarios, mass efficiency, acoustic absorption, vibrationaldamping, protecting from the elements, durability of the external surfaces,and elements of styling.In the second step of the process, the performance requirements of the system wereestablished. This involved a thorough literature survey to establish the state of theart, a rigorous testing program, and an assessment of numerical models and tools toevaluate the performance metrics.In the third step of the process, a concept to fulfil requirements is proposed. Here, amulti-layered, multi-functional panel using composite materials, and polymer foamswith varying structural and acoustic properties was proposed.In the fourth step of the process, a method of refinement of the concept is proposed.Numerical tools and parameterized models were used to optimize the three dimensionaltopology of the panel,material properties, and dimensions of the layers in a stepwisemanner to simultaneously address the structural and acoustic performance.In the fifth and final step of the process, the final result and effectiveness of the methodused to achieve it is examined. Both the tools used and the final result in itself shouldbe examined. In the case study the process is repeated several times with increasingdegrees of complexity and success in achieving the overall design objectives.In addition to the design method, the concept of a multifunctional body panel is definedand developed and a considerable body of knowledge and understanding is presented.Variations in core topology, materials used, stacking sequence of layers, effects ofperforations, and air gaps within the structure are examined and their effects on performanceare explored and discussed. The concept shows promise in reducing vehicleweight while maintaining the structural and acoustic performance necessary in the contextof sustainable vehicle development.

  • 15.
    Casanueva, Carlos
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Dirks, Babette
    Bombardier Transportation.
    Enblom, Roger
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Hossein Nia, Saeed
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Rail Vehicles.
    Shazamanian Shichani, Matin
    MiW Rail Technilogy.
    Integrated simulation of damage: efficient contact modeling, wear-RCF interaction, and long-term evolution2016In: ICRI Workshop on Wear and RCF, 2016Conference paper (Other academic)
  • 16.
    Edgren, Fredrik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. SICOMP AB.
    Compressive failure of NCF composites2005In: Proceedings of the American Societyfor Composites Twentieth Technical Conference, 2005, DEStech Publications, Inc , 2005, p. 1629-1644Conference paper (Refereed)
    Abstract [en]

    This study concerns compression failure of impacted Non-Crimp Fabric (NCF) composite laminates. Panels with a barely visible impact damage (BVID) have been studied under compression after impact (CAI) conditions. Monolithic laminates have been tested in CAI and the failure mechanisms are identified and discussed. The study on monolithic laminates constitutes a complement to a previous study on NCF laminate face sheets of sandwich panels in a naval application. The results from the present study confirm the findings from the study on sandwich skins; the mechanism controlling failure of CAI loaded NCF laminates is formation of kink bands. It is also found that kink bands develop at loads substantially lower than the load at panel failure. The results also indicate that the typical NCF heterogeneous structure, with fibre bundles separated with resin rich regions and fibre waviness, prevent kink bands from growing unstable immediately after initiation.

  • 17.
    Edgren, Fredrik
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Physically Based Engineering Models for NCF Composites2006Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Non-Crimp Fabrics - NCF – are increasingly being used as reinforcements in high performance composite materials. NCF offer the manufacturing advantages from textile preforms in combination with excellent mechanical performance. This study concerns the mechanical performance of NCF composites. Through a combination of experimental work and theoretical studies the mechanisms controlling the mechanical behaviour are explained. Fractography is used as a tool to identify governing mechanisms and link these to the material internal structure. Based on the experimental findings, engineering models are suggested predicting the mechanical behaviour of NCF composite laminates.

    A simplified constitutive model is presented that accounts for the fibre tow out-of-plane waviness. The model is based on Timoshenko beam theory applied on curved beams representing wavy tows in a NCF composite lamina. The model calculates stiffness knock-down factors to be applied on lamina homogenised properties.

    Experiments show compressive failure of NCF composites to be governed by formation and growth of kink bands. For this reason, a failure criterion predicting kinking failure under multiaxial loading is proposed and validated for a NCF composite system. The criterion is to be used on lamina level in a multiaxial NCF laminate. A test method is proposed for extraction of strength parameters valid for the lamina material in a multiaxial laminate.

    Compression-after-impact (CAI) behaviour of NCF composite laminates, as monolithic skins and sandwich panel face sheets, is investigated. Fractographic studies show CAI failure to be controlled by formation of kink bands. The experimental studies reveal that kink bands form at relatively low loads and grow gradually during compressive loading. It is suggested that the notch effect from the gradually developing kink bands cause final catastrophic failure in sandwich panel skins. Finite element analyses, simplistically representing the damage with an idealised notch, are shown to predict panel residual strength with reasonable accuracy.

  • 18. Edgren, Fredrik
    et al.
    Asp, Lars E.
    Compression After Impact Strength of NCF Composite Sandwich PanelsArticle in journal (Other academic)
  • 19.
    Edgren, Fredrik
    et al.
    SICOMP AB.
    Asp, Lars E.
    Bull, Peter Hoaas
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Compressive failure of impacted NCF composite sandwich panels - Characterisation of the failure process2004In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 38, no 6, p. 495-514Article in journal (Refereed)
    Abstract [en]

    In the present study, non-crimp fabric (NCF) composite face sheet sandwich panels have been tested in compression after impact (CAI). Damage in the face sheets was characterised by fractography. Compression after impact loaded panels were found to fail by plastic fibre microbuckling (kinking) in the damaged face sheet. Studies of panels for which loading was interrupted prior to failure revealed extensive stable kink band formation at several positions and in numerous plies. Kink bands initiated and propagated within a wide region close to the point of impact. In addition, kink bands initiated in zones with high shear stresses, away from the impact centre line. Consequently, the fractographic results from this investigation do not support the assumption of modelling the impact damage as an equivalent hole. To achieve accurate predictions of kink band initiation, the stress field must be known. The results from this study imply that bending effects caused by remaining dent or material eccentricities in the damaged region must be considered.

  • 20. Edgren, Fredrik
    et al.
    Asp, Leif E.
    Approximate Analytical Constitutive Model for Non-Crimp Fabric Composites2005In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 36, no 2, p. 173-181Article in journal (Refereed)
    Abstract [en]

    In this paper, a study set on development and validation of constitutive models to account for out-of-plane fibre waviness in Non-crimp fabric (NCF) composites is presented. For this purpose, a mathematical model based on Timoshenko beam theory applied on curved beams, representing wavy tows in a NCF composite layer is employed. Stiffness knock-down factors operating at the ply level are established and introduced in laminate theory. The developed models are validated on laminates by comparison between predictions and experimental data as well as by comparison with numerical results for a cross-ply laminate. Application of the models on NCF composite laminates (cross-ply and quasi-isotropic) reveals that the models successfully predict laminate elastic properties.

  • 21.
    Edgren, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Asp, Leif E.
    Joffe, Roberts
    Failure of NCF Composites Subjected to Combined Compression and Shear Loading2006In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 66, no 15, p. 2865-2877Article in journal (Refereed)
    Abstract [en]

    Earlier studies have shown that formation of kink bands is the mechanism that is likely to govern failure of compression loaded non-crimp fabric (NCF) composite laminates. Because of this, a failure criterion for prediction of failure caused by kinking under multiaxial (axial compression and shear) loading has been adapted to a NCF composite system. The criterion has been validated for compression tests of quasi-isotropic laminates tested in uniaxial compression. By performing compression tests of the laminate at different off-axis angles, it was possible to vary the ratio of compressive axial stress/shear stress in the specimens. The test results proved that the criterion works well for predictions of kinking governed failure for the present material system. Detailed fractographic studies confirmed that formation of kink bands was the mechanism responsible for specimen failure. Kink bands were also found to develop at loads significantly lower than load at specimen failure.

  • 22.
    Ekberg, Lars Peter
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    Development of ultra-precision tools for metrology and lithography of large area photomasks and high definition displays2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Large area flat displays are nowadays considered being a commodity. After the era of bulky CRT TV technology, LCD and OLED have taken over as the most prevalent technologies for high quality image display devices. An important factor underlying the success of these technologies has been the development of high performance photomask writers in combination with a precise photomask process. Photomask manufacturing can be regarded as an art, highly dependent on qualified and skilled workers in a few companies located in Asia. The manufacturing yield in the photomask process depends to a great extent on several steps of measurements and inspections. Metrology, which is the focus of this thesis, is the science of measurement and is a prerequisite for maintaining high quality in all manufacturing processes. The details and challenges of performing critical measurements over large area photomasks of square meter sizes will be discussed. In particular the development of methods and algorithms related to the metrology system MMS15000, the world standard for large area photomask metrology today, will be presented.

    The most important quality of a metrology system is repeatability. Achieving good repeatability requires a stable environment, carefully selected materials, sophisticated mechanical solutions, precise optics and capable software. Attributes of the air including humidity, CO2 level, pressure and turbulence are other factors that can impact repeatability and accuracy if not handled properly. Besides the former qualities, there is also the behavior of the photomask itself that needs to be carefully handled in order to achieve a good correspondence to the Cartesian coordinate system. An uncertainty specification below 100 nm (3σ) over an area measured in square meters cannot be fulfilled unless special care is taken to compensate for gravity-induced errors from the photomask itself when it is resting on the metrology tool stage. Calibration is therefore a considerable challenge over these large areas. A novel method for self-calibration will be presented and discussed in the thesis. This is a general method that has proven to be highly robust even in cases when the self-calibration problem is close to being underdetermined.

    A random sampling method based on massive averaging in the time domain will be presented as the solution for achieving precise spatial measurements of the photomask patterns. This method has been used for detection of the position of chrome or glass edges on the photomask with a repeatability of 1.5 nm (3σ), using a measurement time of 250 ms. The method has also been used for verification of large area measurement repeatability of approximately 10 nm (3σ) when measuring several hundred measurement marks covering an area of 0.8 x 0.8 m2.

    The measurement of linewidths, referred to in the photomask industry as critical dimension (CD) measurements, is another important task for the MMS15000 system. A threshold-based inverse convolution method will be presented that enhances resolution down to 0.5 µm without requiring a change to the numerical aperture of the system.

    As already mentioned, metrology is very important for maintaining high quality in a manufacturing environment. In the mask manufacturing industry in particular, the cost of poor quality (CoPQ) is extremely high. Besides the high materials cost, there are also the stringent requirements placed on CD and mask overlay, along with the need for zero defects that make the photomask industry unique. This topic is discussed further, and is shown to be a strong motivation for the development of the ultra-precision metrology built into the MMS15000 system.

  • 23.
    Ekberg, Peter
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    Stiblert, Lars
    Micronic Laser Systems, Stockholm, Sweden.
    Mattsson, Lars
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    A new general approach for solving the self-calibration problem on large area 2D ultra-precision coordinate measurement machines2014In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 25, no 5, p. 055001-Article in journal (Refereed)
    Abstract [en]

    The manufacturing of flat panel displays requires a number of photomasks for the placement of pixel patterns and supporting transistor arrays. For large area photomasks, dedicated ultra-precision writers have been developed for the production of these chromium patterns on glass or quartz plates. The dimensional tolerances in X and Y for absolute pattern placement on these plates, with areas measured in square meters, are in the range of 200-300 nm (3 sigma). To verify these photomasks, 2D ultra-precision coordinate measurement machines are used having even tighter tolerance requirements. This paper will present how the world standard metrology tool used for verifying large masks, the Micronic Mydata MMS15000, is calibrated without any other references than the wavelength of the interferometers in an extremely well-controlled temperature environment. This process is called self-calibration and is the only way to calibrate the metrology tool, as no square-meter-sized large area 2D traceable artifact is available. The only parameter that cannot be found using self-calibration is the absolute length scale. To make the MMS15000 traceable, a 1D reference rod, calibrated at a national metrology lab, is used. The reference plates used in the calibration of the MMS15000 may have sizes up to 1 m(2) and a weight of 50 kg. Therefore, standard methods for self-calibration on a small scale with exact placements cannot be used in the large area case. A new, more general method had to be developed for the purpose of calibrating the MMS15000. Using this method, it is possible to calibrate the measurement tool down to an uncertainty level of <90 nm (3 sigma) over an area of (0.8 x 0.8) m(2). The method used, which is based on the concept of iteration, does not introduce any more noise than the random noise introduced by the measurements, resulting in the lowest possible noise level that can be achieved by any self-calibration method.

  • 24. El-Mekawy, M.
    et al.
    Shahzad, Kurram
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Ahmed, N.
    Modeling and managing business processes2010In: Handbook on Business Information Systems, World Scientific Publishing Co. Pte Ltd , 2010, p. 93-116Chapter in book (Other academic)
    Abstract [en]

    The purpose of this chapter is to present tools and techniques for modeling and managing business processes. For this, business process modeling is defined and classified according to two levels of detail. These categories are chained together with the help of a transformation technique, which is explained with the help of an example. As soon as the number of processes increases, they cannot be managed manually. This motivates the need for a software system called a business process management system (BPMS). The properties of a BPMS are explained, and the components of a BPMS, which support the necessary requirements of managing processes, are also presented with their advantages. Also, the major principles of business process management (BPM) are presented in this chapter.

  • 25.
    Garcia, Maria-José
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Engineering rubber bushing stiffness formulas including dynamic amplitude dependence2006Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Engineering design models for the torsion and axial dynamic stiffness of carbon black filled rubber bushings in the frequency domain including amplitude dependence are presented. They are founded on a developed material model which is the result of applying a separable elastic, viscoelastic and friction rubber component model to the material level. Moreover, the rubber model is applied to equivalent strains of the strain states inside the torsion or axial deformed bushing previously obtained by the classical linear theory of elasticity, thus yielding equivalent shear moduli which are inserted into analytical formulas for the stiffness. Therefore, unlike other simplified approaches, this procedure includes the Fletcher-Gent effect inside the bushing due to non-homogeneous strain states. The models are implemented in Matlab®. In addition, an experimental verification is carried out on a commercially available bushing thus confirming the accuracy of these models which become a fast engineering tool to design the most suitable rubber bushing to fulfil user requirements. Finally, they can be easily employed in multi-body and finite element simulations

  • 26. Harper, P.
    et al.
    Dwyer-Joyce, R.S.
    Sjödin, Ulf
    University of Sheffield, United Kingdom .
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Evaluation of an ultrasonic method for measurement of oil film thickness in a hydraulic motor piston ring2005In: Life Cycle Tribology, Elsevier, 2005, p. 305-312Chapter in book (Refereed)
    Abstract [en]

    The efficiency of a hydraulic motor depends on the lubrication performance of the piston ring. If the film is too thin then wear occurs quickly, if it is too thick then oil is lost into the cylinder and efficiency is reduced. In this paper a technique for oil film measurement based on ultrasonic reflection is investigated. This has the potential to be used non-invasively on real components. An ultrasonic pulse will reflect from a thin film interposed between two solids. The proportion of the pulse that is reflected depends on the stiffness of the intermediate layer. If the acoustic properties of the film material are known, then the stiffness can readily be used to determine the film thickness. This principle has been employed for the piston ring lubrication case. A piston/cylinder test bench has been used to evaluate the ultrasonic method. A focusing piezo-electric transducer is mounted outside the cylinder and ultrasonic pulses reflected back from the inner bore. The variation of these pulses as the piston ring passes underneath is investigated and used to determine oil film thickness. Films in the range 0.7 to 1.3 μm were measured; the thickness did not depend strongly on either ring speed or sealed pressure. Several practical aspects were investigated such as, attenuation in the cylinder material, response time, and transducer resolution. Whilst this study demonstrated that film thickness measurement is feasible, there are a number of practical considerations that require further work, principally the focusing and coupling of the ultrasonic transducer and the response time.

  • 27.
    Hyll, Caroline
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    Vomhoff, Hannes
    Innventia AB.
    Mattsson, Lars
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    A method for measurement of the directional emittance of paper in the infrared wavelength range2012In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 5, p. 958-967Article in journal (Refereed)
    Abstract [en]

    A method for measuring the directional emittance of paper and board samples was developed. The available literature showed that the influence of temperature and observation angle on the emittance of dry and moist paper had not been investigated in detail. Methods adapted for such investigations were not available. In the developed method, the emittance of a sample is determined by comparing its infrared radiation with the radiation emitted from a reference surface with known emittance. In order to investigate the influence of the wavelength range, two cameras, operating in the mid-wavelength and long-wavelength infrared range, respectively, were used. The method allows for the adjustment of the directional emission angle in a range from 0° down to 80°, and variation of the sample temperature between 30°C and 100°C. A study was performed to evaluate the method. Here, the directional emittance of handsheets made from thermo-mechanical pulp was measured at different wavelength ranges, sample temperatures and emission angles. The obtained emittance values and trends were in agreement with previous experimental work and theoretical predictions. The emittance of the samples was also measured using Fourier-Transform Infrared spectroscopy. Given the methodological differences between the two measurement approaches, the results were in good agreement.

  • 28.
    Hyll, Kari
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics. Innventia, Sweden.
    Image-based quantitative infrared analysis and microparticle characterisation for pulp and paper applications2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Measurements of process variations and particle morphology are widely employed in the pulp and paper industry. Two techniques with high potential, infrared thermography and microparticle characterisation, are mainly used qualitatively. Quantitative thermography requires knowledge of the emittance, a material property which has not been measured under many process-relevant conditions. Quantitative characterisation of microparticles, e.g. pulp fines and mineral fillers, requires the analysis of a large number of particles, which can be accomplished using flow microscopes. Flow microscopes for pulp analysis have had insufficient spatial resolution to resolve fines and fillers. Additionally, there has been a lack of methods which can differentiate between fines and fillers in a mixed suspension.

    State-of-the-art instruments for particle image analysis were evaluated and compared to laser diffractometry, a measurement method based on scattering by diffraction. Laser diffractometry was found to be highly sensitive to the complex refractive index of the particles, and especially to its change due to moisture absorption. A high-resolution imaging flow cytometer and a high-resolution fibre analyser were found to be complementary for characterisation of pure fines and fines/filler mixtures, and superior to laser diffractometry. A method for differentiating between fines and fillers in a suspension based on their autofluorescence and side-scattering was proposed and qualitatively evaluated.

    Furthermore, a method for measuring the directional and integrated emittance of paper was developed and its accuracy was determined. Measurements on a wide range of samples showed that the emittance of fibre-based materials vary significantly with wavelength, pulp type, observation angle, and moisture content. By applying measured quantitative values of the emittance, the thermal energy emitted by sack paper samples during mechanical deformation could be quantitatively calculated. The increase in thermal energy at the time of rupture was found to correlate well with the elastic share of the mechanical energy that was stored in the sample during its elongation.

    In summary, the results of this work have facilitated the use of quantitative microparticle analysis and infrared thermography for pulp and paper applications. 

  • 29.
    Janhager, Jenny
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    User Consideration in Early Stages of Product Development: Theories and Methods2005Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Traditional design theories have focused on technical functions and more or less disregard a product’s user involvement. The existing methods of ergonomic designare mostly intended for analysis activities. There is a need for new dynamic methods that focus on user-product interactions. The aim of this research work is to develop design methods for user-product interactions, which should support synthesis activities in early product development phases.

    An observation study and a questionnaire survey were carried out in order to investigate product developers’ work and relation to the users for providing background information about the research problem. Furthermore, student projects in product development were followed, giving essential input. After the theories and

    methods were developed, a retrospective interview study was carried out in order to confirm the need for the developed methods. The studies showed, for instance, that companies use few formal methods and almost none of these are directed towards the user. It is also indicated that the product developers’ contact with users decreases with increasing company size. Few companies have a defined procedure for defining their intended users.

    Six methods are developed. They embrace three ways of classifying the users and their relations to products and other users (User identification, Use profile and User relations), an analysis of the users’ Activities, goals and motives behind their use of the product, a scenario technique (User-technical process scenario, UTPS), which shows the user process in parallel with the technical process, and a hierarchical decomposition of technical functions and user actions, which is named the Functionaction tree (FAT).

    All the methods, apart from FAT, were tested in real product development teams. All the tested methods stimulate communication between the group members of various competencies in the design group. Most of the methods are easy to apply and are valuable for understanding the design problem. The UTPS is also useful for comparing design solutions and generates new ideas about the design task. The other

    tested methods did not generate many new ideas, but the reason is probably that they were mainly tested on products that are already on the market. Thus, the methods are most valuable in the early design stages, when trying out a product idea or a concept.

  • 30.
    Johnsson, Stefan
    et al.
    Mälardalen University.
    Malvius, Diana
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Integrated Product Development.
    Norell Bergendahl, Margareta
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Integrated Product Development.
    Performance evaluation of complex product development2009In: DS 58-6: Proceedings of ICED 09, the 17th International Conference on Engineering Design, 2009, p. 87-98Conference paper (Refereed)
    Abstract [en]

    In this paper a conceptual performance evaluation framework is proposed and discussed. The aim of the framework is to present a tool to stakeholders, involved in dynamic complex product development activities, that assists in developing a mutual understanding of performance relevancy. It is argued that a system perspective and the possibility to tailor performance criteria and measures according to contextual circumstances are needed for performance evaluation to improve work in product development. Companies need to consider what metrics that are relevant or applicable to measure or evaluate the product development process in their own business and context. From a performance evaluation perspective, a categorization of activities in product development is made into: Planning, Implementation, and Sales and Delivery. It is argued that the three activity categories have different objectives and need to be evaluated and managed accordingly if the overall development process is to be considered successful. Moreover, each activity category can be modeled using a generic activity model to derive relevant performance criteria, needed for identifying relevant performance indicators. It is argued that this will have implications on how performance, that is, efficiency and effectiveness, in product development is evaluated at a managerial and designer level, since the performance evaluation framework is based on the performed activities. Three different perspectives - integrated, information and learning - are used as basis for the discussion in this paper in order to accomplish an enhanced understanding of the value of the performance evaluation.

  • 31.
    Kande, Mallikarjun
    et al.
    KTH, School of Electrical Engineering (EES). ABB .
    Isaksson, Alf J.
    Thottappillil, Rajeev
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Rotating Electrical Machine Condition Monitoring Automation-A Review2017In: MACHINES, ISSN 2075-1702, Vol. 5, no 4, article id 24Article, review/survey (Refereed)
    Abstract [en]

    We review existing machine condition monitoring techniques and industrial automation for plant-wide condition monitoring of rotating electrical machines. Cost and complexity of a condition monitoring system increase with the number of measurements, so extensive condition monitoring is currently mainly restricted to the situations where the consequences of poor availability, yield or quality are so severe that they clearly justify the investment in monitoring. There are challenges to obtaining plant-wide monitoring that includes even small machines and non-critical applications. One of the major inhibiting factors is the ratio of condition monitoring cost to equipment cost, which is crucial to the acceptance of using monitoring to guide maintenance for a large fleet of electrical machinery. Ongoing developments in sensing, communication and computation for industrial automation may greatly extend the set of machines for which extensive monitoring is viable.

  • 32.
    Kari, Hyll
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics. Innventia AB.
    Farahani, Farnaz
    Innventia AB, Sweden .
    Mattsson, Lars
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    Optical methods for fines and filler size characterization: Evaluation and comparison2016Report (Other academic)
    Abstract [en]

    The pulp fines and mineral fillers in the fine fraction of a papermaking stock influence process conditions and sheet properties. The influence is largely dependent on the size and shape of the particles. Quantitative characterization of the size and shape of fines and fillers would aid in process control and prediction of product properties.  Thus, the aim of the study was to evaluate and compare optical instruments which can be used to quantitatively characterize the fine fraction of a papermaking stock. The compared instruments were the Mastersizer2000 from Malvern, based on diffraction scattering of a laser beam, the ImageStream from Amnis, and the Fiber Tester and Fiber Tester Plus from ABB Lorentzen & Wettre. The last three instruments are all based on imaging of the particles and have spatial resolutions ranging from 0.33 µm to about 10 µm per pixel.

    All instruments overestimated the size of calibration spheres with known sizes. In several cases, calibration particles that were smaller than the spatial resolution of the instrument were detected. In these cases, the relative measurement error was large, likely due to positioning and quantization errors. It is also suggested that the oversizing was partly due to dissimilar optical properties of the calibration particles, compared to the typical sample, and that better calibration materials for fines need to be developed.

    For the image-based instruments, the relative share of fines and filler particles increased with as the size of the measured particles decreased. Thus, with higher spatial resolution, more particles were detected. However, the shape of the particle size distribution depended on the resolution and the field-of-view. The ImageStream resolved single PCC particles, which has not previously been done using flow microscopy. Due to its limited field-of-view, the ImageStream could not measure the largest fines, which were detected by the Fiber Tester and Fiber Tester Plus. While the Fiber Tester Plus did not resolve single PCC particles, it detected, due to its higher resolution, a higher share of smaller particles than the Fiber Tester. Overall, the ImageStream and the Fiber Tester Plus were found to be complementary.

    The diffraction-based method struggled to measure small fines. It is proposed that small fines diffracted light insufficiently to be detected by the instrument. The obtained result was also highly sensitive to the choice of refractive index; a fact that some of the previous users apparently were not aware of.

    In summary, image-based methods were found to perform better than the diffraction-based method when measuring on fines and mixtures of fines and fillers, while the highest resolution image-based instrument and the diffraction-based method were best when measuring on pure fillers.

  • 33.
    Kerres, Bertrand
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Fischer, Katharina
    Fraunhofer Institute for Wind Energy and Energy System Technology IWES.
    Madlener, Reinhard
    Institute for Future Energy Consumer Needs and Behavior (FCN), School of Business and Economics/E.ON Energy Research Center, RWTH Aachen University.
    Economic evaluation of maintenance strategies for wind turbines: a stochastic analysis2015In: IET Renewable Power Generation, ISSN 1752-1416, E-ISSN 1752-1424, Vol. 9, no 7, p. 766-774Article in journal (Refereed)
    Abstract [en]

    The authors develop a stochastic model for assessing the life-cycle cost and availability of wind turbinesresulting from different maintenance scenarios, with the objective to identify the most cost-effective maintenancestrategy. Using field-data-based reliability models, the wind turbine – in terms of reliability – is modelled as a serialconnection of the most critical components. Both direct cost for spare parts, labour and access to the turbine, as wellas indirect cost from production losses are explicitly taken into account. The model is applied to the case of a VestasV44–600 kW wind turbine. Results of a reliability-centred maintenance analysis of this wind turbine are used to selectthe most critical wind turbine components and to identify possible maintenance scenarios. This study reveals thatcorrective maintenance is the most cost-effective maintenance strategy for the gearbox and the generator of the V44turbine, while the cost benefit of condition-based maintenance using online condition-monitoring systems increaseswith higher electricity price, turbine capacity and remoteness of sites.

  • 34.
    Kharazmi, Parastou
    KTH, School of Architecture and the Built Environment (ABE).
    Field investigation to assess performance of polymeric lining used in renewal of sewers in buildings - Dataset2019Data set
    Abstract [en]

    This dataset includes original data provided to support parts of the research findings stated in article: "Experimental assessment of the state of the lining materials used in the rehabilitation of sewers in residential buildings”.

  • 35.
    Larberg, Ylva
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Åkermo, Malin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Norrby, Monica
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    On the in-plane deformability of cross-plied unidirectional prepreg2011In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 46, no 8, p. 929-939Article in journal (Refereed)
    Abstract [en]

    The work presented herein aims to characterise the in-plane properties of cross-plied unidirectional prepreg using the bias extension method. The study is focusing on carbon fibre/epoxy material systems and testing is performed at elevated temperatures to enhance formability. Using digital image correlation (DIC), the specimen deformation and fibre rotation is captured during tests. The study shows that the cross-plied unidirectional material deforms at different characteristic length scales as deformation continues: first seemingly continuous and later in form of bands. Further, the different type of prepreg materials investigated behaves differently; for one type the pin-jointed net theory fit well, enabling simple estimation of resulting fibre angle, while for another not. Different loading speed, temperatures and layup methods are investigated in order to pin-point its influence on the deformability.

  • 36.
    Leander, John
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Friktionsförband under yttre dragkraft: En studie av kraftfördelning mellan skruv och plåtar2010Report (Other academic)
    Abstract [sv]

    Föreliggande studie omfattar en studie av ett förspänt skruvförband utsatt för dragkrafter.

    Enligt gällande Eurokod för dimensionering av knutpunkter och förband i stålkonstruktioner, EN 1993-1-8, beaktas en medverkande area av de sammanfogade plåtarna som är fyra gånger skruvens area. Förfarandet lämnas utan kommentarer i standarden. Med hjälp av olinjära FE-analyser studeras verkningssättet för ett förspänt skruvförband under dragning och kraftfördelningen mellan skruven och de sammanfogade plåtarna.

    Resultatet visar att den medverkande arean inte är konstant och att både de sammanfogade plåtarnas tjocklek och skruvens diameter har betydelse för sambandet. En funktion för beräkning av graden av samverkan i förbandet presenteras och är ett resultat av en statistisk utvärdering.

  • 37.
    Liljencrantz, Axel
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges (name changed 20110630).
    Monitoring railway traffic loads using bridge weight-in-motion2007Licentiate thesis, comprehensive summary (Other scientific)
  • 38.
    Liljencrantz, Axel
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Twim, A MATLAB toolbox for real-time evaluation and monitoring of traffic loads on railway bridges2009In: Structure and Infrastructure Engineering, ISSN 1573-2479, E-ISSN 1744-8980, Vol. 5, no 5, p. 407-417Article in journal (Refereed)
    Abstract [en]

    This paper describes Twim, a toolbox written in the MATLAB computer language. Twim is designed for monitoring bridge behaviour during train passages as well as for performing Bridge Weigh-In-Motion of railway traffic, both in real-time and offline. The algorithms calculate the static bogie loads and bogie distances, as well as the speed and acceleration of the train. Twim also includes visualization functions, automatic identification of known locomotives and an auto-calibration that uses locomotives with known bogie loads. The algorithms used place specific requirements on both the bridge type and the instrumentation of the bridge. These requirements are explained in the paper. The instrumentation of several bridges is described, and some of the interesting results gained through this instrumentation are presented.

  • 39.
    Liljencrantz, Axel
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Olofsson, Per
    Implementing bridge weigh-in-motion for railway traffic2007In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 85, no 02-jan, p. 80-88Article in journal (Refereed)
    Abstract [en]

    This paper focuses on implementing existing bridge weigh-in-motion technology on railways. Using only simple instrumentation with four concrete embedded sensors, a complete WIM system with axle detection, weighing, track detection and attempted identification of locomotives was implemented on a bridge with multiple railway tracks. The results and the effectiveness of this type of sensor setup is discussed.

  • 40.
    Lindbergson, Hans
    KTH, School of Architecture and the Built Environment (ABE), Philosophy and History of Technology, Philosophy.
    Granskning vid anläggningsändringar och dess påverkan på dammsäkerhet: - samt en beskrivning av säkerhetskultur hos Vattenfall Vattenkraft2009Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    There are approximately 250 dams in Sweden classified as 1A or 1B; the classification indicating the highest level of severity in case of a dam failure. Vattenfall owns about 50% of these dams, and is legally responsible for all consequences related to these dams.

    The majority of all existing water power stations were built in the 50, 60 or 70´s. Through the years they have functioned well and delivered vast amounts of energy to our community. In later years an extensive review of all sites has been performed, which in turn has led to the initiation of a number of major projects aiming to modernize and if possible increase the power output in existing power stations. In parallel, a new, more modern view on safety has been developed.

    A milestone was the development of RIDAS, the power stations guidelines for safety, introduced in 1997. Previously there were different guidelines in different companies. One area that needs to be improved in RIDAS is guidelines for handling existing dams, especially regarding dams that were built decades ago.

    The efforts to increase knowledge regarding dam structures and dam safety are continuously ongoing within Vattenfall. It covers purely technical aspects such as measurements, new models, restructuring etc as well as organizational aspects. This dissertation covers the latter.

    The subject for this assignment was investigating how dam safety is; i) affected by the plans for imminent implementation of structural changes in the stations and ii) how these changes can best be assessed. When any sort of structural change is made, the integrity of the dam is always affected, either directly or indirectly. In order to capture these affecting factors, it is vital that allsteps in the process are monitored from a safety perspective.

    During the process, the scope has expanded to include also the general safety culture within the organization.

    Conluscions:

    • There is a need to further develop quality and management systems and also formalize procedures and work processes within Vattenfall Vattenkraft. This is relevant for and affects the whole organization.
    • Dam safety needs to be viewed in a broader perspective, throughout the organization.
    • A modernized approach to safety culture is required, through e.g. followups, incident reports, realitychecks and education.
    • Two specific circumstances need to be managed from a safety perspective; i) Hydropower is an old discipline; i.e. most of all stations were built many years ago. ii) Division of functions & responsibilities such as ownership, maintenance and projects within the organization pose a risk due to lack of a comprehensive overall view.
  • 41.
    Lindfeldt, Olov
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Traffic and Logistics (closed 20110301). KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Influences of station length and inter-station distance on delays and delay propagation on single-track lines with regional rail traffic2006In: Computers in Railways X: Computer System Design and Operation in the Railway and Other Transit Systems / [ed] Allan, J; Brebbia, CA; Rumsey, AF; Sciutto, G; Sone, S; Goodman, CJ, Southampton: WIT Press , 2006, p. 511-520Conference paper (Refereed)
    Abstract [en]

    Train services on single-track lines suffer from time losses due to crossings, imposed by the bidirectional traffic. The time losses, in this paper denoted crossing time, are caused by constraints in the infrastructure and delay propagation, which give a stochastic contribution that varies from one crossing situation to another.

    Two examples of infrastructure improvements that decrease the crossing time are examined: partial double-track at the location of timetabled crossing and decreased inter-station distances. A mathematical model is used to evaluate these improvements.

    Partial double-tracks seem to be very efficient when traffic intensity and delay variances are moderate. Shortened inter-station distances give less effect but are less sensitive to delay variance and give valuable additional line capacity.

    The used model assumes independence between crossing trains, which imposes a moderate capacity utilisation. In more congested situations simulation methods are needed to make more complex crossing patterns possible.

  • 42.
    Lindén, Julia
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Scania CV AB.
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Söderberg, Anders
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    DSM-based Reliability Analysis of Modular Architectures2015In: Modeling and managing complex systems: Proceedings of the 17th International DSM Conference Fort Worth (Texas, USA), 4-6 November 2015 / [ed] Tyson R. Browning, Steven D. Eppinger, Danilo Marcello Schmidt, Udo Lindemann, München: Carl Hanser Verlag GmbH, 2015, p. 111-122Conference paper (Refereed)
    Abstract [en]

    The main function of a heavy truck is to transport goods. Furthermore,the truck is directly operated by a driver, who has several additional functionalrequirements, of both ergonomic and communicative characters. Transport is a trustbusiness and today’s just-in-time delivery systems rely on getting the goods on time.Product reliability, which is the ability of a system to perform according to itsfunctional targets, is consequently a crucially important property for a heavy truck.This paper proposes a structure for a system reliability model that integrates differentand complementary representations, such as Function-Means trees and DesignStructure Matrix. The novelty of the presented approach is that it treats andintegrates the technical and the human subsystems through the human-technicalsystem interfaces in an extended DSM. The proposed reliability systems approachis verified with a component analysis case study of a truck cab and driver system.

  • 43.
    Lindén, Julia
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Scania CV AB.
    Sellgren, Ulf
    Söderberg, Anders
    Modelling uncertainty of reliability forecasts with varying operating conditionsArticle in journal (Other academic)
    Abstract [en]

    Heavy truck customers attach great importance to reliability, which make reliability assessments essential in product development projects. Since changes are easier and less expensive in early project stages, early reliability assessments are valuable. At these early stages, complete vehicle testing cannot yet be made. System reliability assessments must be made based on test data from component and subsystem tests, sometimes performed with different operating conditions than the system will be used in. Test data must be translated to the new situation, which requires information about how various factors affect reliability. Furthermore, the uncertainty in the forecast increases when the assessment is made for new operating conditions. Therefore, we also need information about how uncertainty propagates. The question is how this translation can be made, when data is sparse and expert judgement must be used, and how the increasing uncertainty can be reasonably modelled. In this paper, current methods to take into account varying operating conditions have been reviewed, and four methods have been tested in a case study. These methods are one based on fuzzy logic, a first-order second-moment reliability method (VMEA), and two variants of the proportional hazards model. The study shows that several methods are capable of handling sparse data, but only VMEA can model how uncertainty increases when operating conditions vary. It has however the drawback of being quite sensitive to uncertainty in the input data.

  • 44.
    Löfgren, Björn
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Kinematic Control of Redundant Knuckle Booms with Automatic Path Following Functions2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    To stay competitive internationally, the Swedish forestry sector must increase its productivity by 2 to 3% annually. There are a variety of ways in which productivity can be increased. One option is to develop remote-controlled or unmanned machines, thus reducing the need for operator intervention. Another option—and one that could be achieved sooner than full automation—would be to make some functions semi-automatic. Semi-automatic operation of the knuckle boom and felling head in particular would create “mini-breaks” for the operators, thereby reducing mental and physiological stress. It would also reduce training time and increase the productivity of a large proportion of operators.

    The objective of this thesis work has been to develop and evaluate algorithms for simplified boom control on forest machines. Algorithms for so called boom tip control, as well as automatic boom functions have been introduced. The algorithms solve the inverse kinematics of kinematically redundant knuckle booms while maximizing lifting capacity. The boom tip control was evaluated – first by means of a kinematic simulation and then in a dynamic forest machine simulator. The results show that boom tip control is an easier system to learn in comparison to conventional control, leading to savings in production due to shorter learning times and operators being able to reach full production sooner. Boom tip control also creates less mental strain than conventional control, which in the long run will reduce mental stress on operators of forest machines. The maximum lifting capacity algorithm was then developed further to enable TCP path-tracking, which was also implemented and evaluated in the simulator.

    An evaluation of the fidelity of the dynamic forest machine simulator was performed to ensure validity of the results achieved with the simplified boom control. The results from the study show that there is good fidelity between the forest machine simulator and a real forest machine, and that the results from simulations are reliable. It is also concluded that the simulator was a useful research tool for the studies performed in the context of this thesis work.

    The thesis had two overall objectives. The first was to provide the industry and forestry sector with usable and verified ideas and results in the area of automation. This has been accomplished with the implementation of a simplified boom control and semi-automation on a forwarder in a recently started joint venture between a hydraulic manufacturer, a forest machine manufacturer and a forest enterprise. The second objective was to strengthen the research and development links between the forestry sector and technical university research. This has been accomplished through the thesis work itself and by a number of courses, projects and Masters theses over the last three years. About 150 students in total have been studying forest machine technology in one way or the other.

  • 45.
    Löfgren, Björn
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Ohlsson, K.
    Wikander, Jan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Egermark, T.
    An evaluation of boom tip control for forest machines in a real-time forest machine simulator2007In: Human Factors: The Journal of the Human Factors and Ergonomics Society, ISSN 0018-7208Article in journal (Other academic)
  • 46.
    Löfgren, Björn
    et al.
    Forestry Research Institute of Sweden, Sweden.
    Ohlsson, Kjell
    Wikander, Jan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    The fidelity of a real time forest machine simulator2007In: Fall Simulation Interoperability Workshop 2007, 2007, p. 377-398Conference paper (Refereed)
    Abstract [en]

    It is essential to reduce the mental and physical stress on forest machine operators. The operator in a harvester cuts down one tree each 47 second, makes 12 decisions per tree and uses on average 24 functions per tree. In Sweden, we are using the Cut To Length (CTL) method, which means that the tree is cut in pieces out in the stand. This is done 1000 times a day. The solutions that come into our mind, to help the operators, are full or semi automation and other ways to improve the Human Machine Interaction (HMI). It is not practical or cost effective to initially develop automation or HMI ideas on real machines. Instead, a better solution is to use simulators. Normally, the existing forest machine simulators are used in teaching future forest machine operators. In our case, we use the simulator as a research tool. To rely on the result coming from tests with the simulator we performed a fidelity test. We conducted a time study, where a harvester operator have cut down approximately 500 trees and we have also measured data from the stand such as tree diameter, height, position, height to first live branch and tree type. We have also measured the terrain. The same stand and terrain data was implemented into the simulator and the same operator performed the same work again. The results demonstrated that there is a good fidelity between a real forest machine and the simulator. The time difference between the reality and the simulator is just ± 5 % for different work operations. Qualitatively, the results were on par. Several aspects on simulator fidelity will be discussed in the paper.

  • 47.
    Löfgren, Björn
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Wikander, Jan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Kinematic control of redundant knuckle Booms with Path Tracking under Geometric, Velocity and Acceleration Constraints2009In: International Journal of Forest Engineering, ISSN 1494-2119, E-ISSN 1913-2220Article in journal (Other academic)
  • 48.
    Malvius, Diana
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Integrated Product Development.
    Integrated information management in complex product development2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Where do companies begin their efforts when trying to improve information management in product development? In large companies involving many people, multiple processes and highly technological products several factors have an impact on efficiency. Interdisciplinary integration and structured information are two overall proposed key factors that have been identified as important to obtain efficient information management.

    Measurement of satisfaction level among information systems users is proposed as an angle of approach to identify key improvement areas from an operative perspective that are argued to be strategic for management to address. However, the need for adjustments to contextual prerequisites and a changing environment makes evaluation necessary prior to measurement. An evaluation framework is proposed to identify metrics that are tailored and kept in line with business and development strategies to ensure their relevancy.

    This research has aimed at taking a holistic approach to information management in complex product development. The research focus has been on the integration between engineering disciplines where software and electrical R&D departments at automotive companies have been the main source of the analysis material.

    Integrated information management entails support for activities within the engineering domain. Several strategies are discussed to manage trade-offs in organizations in order to succeed with integrated information management. A needs-based balance is one important approach proposed to resolve changing and conflicting needs. Furthermore, it is argued that operative and strategic goals should be allowed to co-exist.

    Providing the right infrastructure to support designers in their everyday work does not necessarily mean additional functionality to existing information systems or automated work activities by improved document templates. Rather, it is suggested that a shift in focus (from addressing detailed requirements management to reflecting on interrelationships between information objects and system inter-dependencies) would be a strong mechanism to succeed with information management. The transition into model-based development is argued to be a much needed change for organizations to obtain integrated information management, since a model-based approach is considered an important basis for structured information. Anticipated benefits with integrated information management are increased information availability, reduced information overflow, and enhanced communication and understanding of critical system dependencies

  • 49.
    Mattsson, Lars
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    Schulze, Volker
    Institut für Produktionstechnik und Institut für Werkstoffkunde, Karlsruhe Institute of Technology, Karlsruhe, Germany .
    Schneider, Johannes
    Institut für Angewandte Materialien, Karlsruhe Institute of Technology, Karlsruhe, Germany .
    Quality assurance and metrology2009In: Ceramic Processing in Microtechnology / [ed] H-J Ritzhaupt-Kleissl, P. Johander, Dunbeath: Whittles Publishing, 2009, p. 305-325Chapter in book (Other academic)
    Abstract [en]

    The cost effective large scale production of reliable micro systems for mechanical and tribological applications requires a customized quality assurance. Equipment and procedures established for the characterization of materials and components on the macro scale very often cannot be successfully applied on the micro scale. Therefore in recent years customized techniques were developed for dimensional control, surface topography and roughness characterization as well as for microstructural analysis, mechanical and tribological testing. This chapter overviews the state-of-the-art of research and technological developments on these fields and thereby responds on the necessary fundamentals of metrology, the constraints of the used equipment and technologies as well as the particular problems arising from characterization of micro components made of ceramic materials.

  • 50.
    Mazidi, Peyman
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems. Comillas Pontifical University, Spain.
    Bobi, Miguel A. Sanz
    Shayesteh, Ebrahim
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Impact of health indicators on maintenance management and operation of power systems2017In: Journal of Risk and Reliability, ISSN 1748-006X, E-ISSN 1748-0078, Vol. 231, no 6, p. 716-731Article in journal (Refereed)
    Abstract [en]

    This article proposes a maintenance management and risk reduction approach. The approach introduces two reliability-based indexes called condition indicator and risk indicator. Condition indicator is a unit-less parameter that comes directly from monitored condition of a component and converts the categorical condition into a numerical value. Risk indicator in megawatt represents the risk imposed by the health of a component onto the system. To demonstrate application of the indicators, they are implemented through an hourly network constraint unit commitment problem and applied in a test system where the analysis of impact of condition of the generators to the operation is the new contribution. The results demonstrate how addition of such indicators will impact the operation of the grid and maintenance scheduling. The results show the benefit for the system operator as the overall failure risk in the system is taken into account, and the benefit for the asset owner as the direct impact of the maintenance to be carried out can be investigated. Two of the main outcomes of the maintenance management and risk reduction approach are as follows: asset owners can analyze their maintenance strategies and evaluate their impacts in the maintenance scheduling, and system operators can operate the grid with higher security and lower risk of failure.

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