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  • 301.
    Bergkvist, Fredrik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Industriell teknik.
    Ljunggren, Terje
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Industriell teknik.
    Design och optimering av lagertätning: Hos hydrodynamiska oljeglidlager med labyrinttätning2014Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [en]

    ABB Motors and Generators manufacture large AC machines with oil lubricated plainbearings. The machines have occasional problems with oil leakage from the bearings. aproblem that ABB wants to be solved.In this thesis the cause of this leakage were investigated, with focus on the bearingseals.The purpose of this work was also to suggest amndments for preventing thisproblem. , and to suggest improvements that can prevent this. The first step was todo a literature survey of earlier work on this problem, study the theory ofhydrodynamic bearings and different types of seals and their properties. Severalexperiments and pressure measurements were performed on machines in operation.The results were then analyzed to identify the causes of leakage and to confirm/oreliminate the hypotheses that had been stablished in the earlier stage of this work.Finally, recommendations for problem management was proposed. New designs werealso developed based on the experimental findings, interviews with the technicians inthe company, and observations on the manufacturing and repairing procedures madeduring this work.The experimental and analytical results suggests that the current design of the bearingsystmem is sensitive to oil leakage. It has been discovered that pressure is the mostrelevant parameter, while several other parameters also contribute to the problem.

    Fulltekst (pdf)
    Design och optimering av lagertätning
  • 302.
    Berglund, Linn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Jonoobi, Mehdi
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Wood and Paper Science and Technology, Faculty of Natural Resources, University of Tehran, Karaj, Iran.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Fibre and Particle Engineering, University of Oulu, Oulu, Finland.
    Promoted hydrogel formation of lignin-containing arabinoxylan aerogel using cellulose nanofibers as a functional biomaterial2018Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 8, nr 67, s. 38219-38228Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, three-dimensional (3D) aerogels and hydrogels based on lignin-containing arabinoxylan (AX) and cellulose nanofibers (CNF) were prepared. The effects of the CNF and the crosslinking with citric acid (CA) of various contents (1, 3, 5 wt%) were evaluated. All the aerogels possessed highly porous (above 98%) and lightweight structures. The AX-CNF hydrogel with a CA content of 1 wt% revealed a favorable network structure with respect to the swelling ratio; nanofiber addition resulted in a five-fold increase in the degree of swelling (68 g of water per g). The compressive properties were improved when the higher CA content (5 wt%) was used; when combined with CNF, there was a seven-fold enhancement in the compressive strength. The AX-CNF hydrogels were prepared using a green and straightforward method that utilizes sustainable resources efficiently. Therefore, such natural hydrogels could find application potential, for example in the field of soft tissue engineering.

  • 303.
    Berglund, Linn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Luleå university of technology.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Direct preparation of alginate/cellulose nanofiber hybrid-ink from brown seaweed for 3D biomimetic hydrogelsManuskript (preprint) (Annet vitenskapelig)
  • 304.
    Berglund, Pierre
    et al.
    Blekinge Tekniska Högskola, Institutionen för maskinteknik.
    Pettersson, Johan
    Blekinge Tekniska Högskola, Institutionen för maskinteknik.
    Dynamic Characteristics of Exhaust System Hangers1999Annet (Annet vitenskapelig)
    Abstract [en]

    Comfort in automobiles is greatly affected by vibrations and noise transmitted to the chassis from the engine. This is a study of the dynamic characteristics of exhaust system hangers, which is an important transfer path for vibrations. Theoretical and experimental modal analysis is used to suggest design parameters that increase the natural frequencies to above 450 Hz for two hanger types.

    Fulltekst (pdf)
    Dynamic Characteristics of Exhaust System Hangers
  • 305.
    Berglund, Simon
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Produktutveckling.
    Lennartsson, Joel
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Produktutveckling.
    Design of Power Off Brake: Utveckling av testutrustning2018Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    The goal with this thesis is to find together with Saab Avionics Systems the correlation between applied current, air gap and forces that a brake with an electromagnetic release function have. This is achieved through theoretical calculations and practical tests.  

    At the moment the brakes are used in electromechanical actuators that are applied in aircraft flap systems.

    These brakes have been in Saab’s collection of products since a decade and to keep on being a competitive supplier they need to optimize their design process. However, there are difficulties regarding calculating the force of the magnetic field of these brakes since it is very complicated. To better understand how the design can be altered the current product Power Off Brake needs to be tested and analyzed.  

    The test equipment that was developed is designed so that the brake dimension, air gap and current can vary alongside a change of surrounding temperature. After a test in room temperature it was found that the test equipment had a margin of error about 10%.

    By testing Power Off Brake with the selected measuring method and test equipment Saab will get one step closer to better understand the relationship between theoretical calculations and practical tests. This can be used to reduce the safety margins when new brakes are to be developed since the test results provide insight about what happens when saturation in the material occur and how the brake perform in environmental conditions of an aircraft.

    Furthermore, the authors leave recommendations for continued work and suggestions for improved design.

    Fulltekst (pdf)
    fulltext
  • 306.
    Bergman, Greger
    et al.
    SSAB HardTech.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    A finite element model for thermomechanical analysis of sheet metal forming2004Inngår i: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 59, nr 9, s. 1167-1186Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A thermal model based on explicit time integration is developed and implemented into the explicit finite element code DYNA3D to model simultaneous forming and quenching of thin-walled structures. A staggered approach is used for coupling the thermal and mechanical analysis, wherein each analysis is performed with different time step sizes. The implementation includes a thermal shell element with linear temperature approximation in the plane and quadratic in the thickness direction, and contact heat transfer. The material behaviour is described by a temperature-dependent elastic-plastic model with a non-linear isotropic hardening law. Transformation plasticity is included in the model. Examples are presented to validate and evaluate the proposed model. The model is evaluated by comparison with a one-sided forming and quenching experiment

  • 307. Bergman, Greger
    et al.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Thermo-mechanical analyses of forming and quenching of thin steel plates1999Inngår i: Proceedings of the 2nd ESAFORM Conference on Material Forming, 1999Konferansepaper (Fagfellevurdert)
  • 308. Bergman, Greger
    et al.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Verification of thermomechanical material models by thin-plate quenching simulations1997Inngår i: Journal of thermal stresses, ISSN 0149-5739, E-ISSN 1521-074X, Vol. 20, nr 7, s. 679-695Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A computational model for quenching simulations of thin plates has been developed. The model is examined by comparisons with experiments with one-sided water spray cooling. With this experiment, the thermomechanical behavior of the material can be monitored throughout the time history of the test. Experiments have been performed with a material that undergoes only martensitic transformation during quenching. For the conditions examined the plate exhibits permanent deformation after quenching. In the stress calculation, transformation plasticity is included in the effective-stress-function (ESF) algorithm as an additional strain component related to the stress and to the progress of transformation. Analyses of the present experiments show that the permanent deformation of the plate is exclusively due to transformation plasticity

  • 309. Bergman, Greger
    et al.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jeppsson, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Integration of a product design system and nonlinear finite element codes via a relational database1995Inngår i: Engineering computations, ISSN 0264-4401, E-ISSN 1758-7077, Vol. 12, nr 5, s. 439-449Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A database for finite element models and related data is developed and incorporated into a prototype system for integration of non-linear finite element codes with a product design system. In the prototype system, the database is used as a link for integrating commercial, public domain as well as in-house codes. In the present system, the public domain finite element codes NIKE2D, NIKE3D, DYNA2D, DYNA3D and TOPAZ2D are integrated with the CIM-system I-DEAS. The prototype system is primarily intended as a platform in research projects for development of integrated environments tuned for simulations of specific manufacturing processes such as quenching, welding, hot rolling, metal powder compaction and hot isostatic pressing

  • 310.
    Bergstedt, Joel
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Connecting casting simulations with strength analysis2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The finite element method and casting simulations have reached higher popularity and accuracy partly due to increase in computer power over the last couple of years. The increase in computer power has led to better simulations and hence a better reflection of reality. The development in simulations has made it possible to connect different kinds of physics and simulation tools, a type of multiphysics. In this work the connection between casting simulations and strength analysis (with finite element method) has been evaluated with focus on improving the computation accuracy at Scania.This work indicates that by implementing data from casting simulation into a strength analysis the result changes. These changes are local and often located in areas where the stress levels are large. This emphasise the importance of using casting simulation data in strength analyses. Furthermore there are a large room for improvement and some calibration should be executed before usage.A method has been developed on how to implement casting simulations into a strength analysis. This method requires a interdisciplinary connection between different groups at Scania. The result of this connection is not only a better simulation but also an exchange of knowledge regarding the product that is of interest for all involving groups.

    Fulltekst (pdf)
    fulltext
  • 311.
    Bergström, Joel
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Creep simulation of Kantal(R) APMT tubes using FEM2011Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The purpose with this thesis work is to simulate the deflection due to creep of Kanthal(R) APMT furnace tubes using the finite element method (FEM). Kanthal APMT is a material which shows a larger primary creep compared to other metals. Therefore the creep deformation must be described with a material model which takes both primary and secondary creep into consideration. In this thesis work a material model called time hardening has been used.

    *C2 is stress dependent. By modifying C2 so that the results from the simulations better corresponds with test data an equation for how C2 depends on the stress could be obtained.

    The value for C2 is then calculated for each tube dimension giving results which are close to the data from sagging tests. The results may be seen as an overestimation of the actual deflection. A sensitivity analysis showed that the model is very sensitive to changes in the material parameters. A few percent change in C2 for example will change the deflection by more than 100 percent. 

    * For equation see full text

     

     

  • 312.
    Bergström, Jonathan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Åhman, Christoffer
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Shear strain rate dependency of expanded polystyrene foam2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Fulltekst (pdf)
    fulltext
  • 313.
    Bergström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Fergusson, Michael
    Xtura AB, Kungsbacka.
    Folkesson, Patrik
    Xtura AB, Kungsbacka.
    Runnemalm, Anna
    University West, Department of Engineering Sciences, Trollhättan.
    Ottosson, Mattias
    University West, Department of Engineering Sciences, Trollhättan.
    Andersson, Alf
    Chalmers University of Technology, Department of Product and Production Development.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Automatic in-line inspection of shape based on photogrammetry2016Inngår i: SPS16, Lund: SPS16 , 2016, , s. 9Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We are describing a fully automatic in-line shape inspection system for controlling the shape of moving objects on a conveyor belt. The shapes of the objects are measured using a full-field optical shape measurement method based on photogrammetry. The photogrammetry system consists of four cameras, a flash, and a triggering device. When an object to be measured arrives at a given position relative to the system, the flash and cameras are synchronously triggered to capture images of the moving object. From the captured images a point-cloud representing the measured shape is created. The point-cloud is then aligned to a CAD-model, which defines the nominal shape of the measured object, using a best-fit method and a feature-based alignment method. Deviations between the point-cloud and the CAD-model are computed giving the output of the inspection process. The computational time to create a point-cloud from the captured images is about 30 seconds and the computational time for the comparison with the CAD-model is about ten milliseconds. We report on recent progress with the shape inspection system.

    Fulltekst (pdf)
    fulltext
  • 314.
    Bergström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Khodadad, Davood
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hällstig, Emil
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Dual-wavelength digital holography: single-shot shape evaluation using speckle displacements and regularization2014Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 53, nr 1, s. 123-131Artikkel i tidsskrift (Fagfellevurdert)
  • 315.
    Bergström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Khodadad, Davood
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hällstig, Emil
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Single shot shape evaluation using dual-wavelength holographic reconstructions and regularization2014Inngår i: Fringe 2013: 7th International Workshop on Advanced Optical Imaging and Metrology / [ed] Wolfgang Osten, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 2014, s. 103-108Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The aim of this work is to evaluate the shape of a free form object using single shot digital holography. The digital holography results in a gradient field and wrapped phase maps representing the shape of the object. The task is then to find a surface representation from this data which is an inverse problem. To solve this inverse problem we are using regularization with additional shape information from the CAD-model of the measured object.

  • 316.
    Bergström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Michael, Fergusson
    Viospatia AB.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Virtual projective shape matching in targetless CAD-based close-range photogrammetry for efficient estimation of specific deviations2018Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 57, nr 5, artikkel-id 053110Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A concept for targetless, computer-aided design (CAD)-based, close-range photogrammetry for online shape inspection is introduced. The shape of an object, which is arbitrarily located on a conveyor belt, is to be measured and compared with its nominal shape as defined by a CAD model. For most manufactured objects, deviations are only measured at a few given comparison points. These deviations can be estimated using local photogrammetry based on a priori geometrical information given by the CAD model and the comparison points. Our method results in faster output with higher precision, because we do not generate a shape representation of the entire measured object using typical photogrammetric methods. Images depicting the object from convergent angles are captured by an array of cameras in a precalibrated network, and the CAD model is matched and aligned, within the projective geometry of the camera network, to the depicted object in the images without the use of targets. An algorithm for solving this virtual projective targetless shape matching problem is presented.

  • 317.
    Bergström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Rosendahl, Sara
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Shape verification using dual-wavelength holographic interferometry2011Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 50, nr 10, artikkel-id 101503Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In automotive industry there is an interest of controlling the shape of a large number of identical components on-line in the manufacturing process. We propose a method to do this by capturing a digital hologram of the object and then using information from its computer aided design (CAD) model to calculate the shape and determine the agreement between the manufactured object and the CAD-model. The holographic recording of the object is done using dual wavelengths with a synthetic wavelength of approximately 400 μm. The optical measurement results in a wrapped phase map with the phase values in the interval [−π, π]. Each phase interval represents a depth distance on the object of about 0.2 mm. The phase unwrapping is done iteratively using information from the CADmodel. This implies that it is possible to measure large discontinuities on the surface of the measured object. The method also gives a point-to-point correspondence between the measurement and the CAD-model which is vital for tolerance control.

  • 318.
    Bergström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Rosendahl, Sara
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Shape verification aimed for manufacturing process control2011Inngår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 49, nr 3, s. 403-409Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We describe a method to verify the shape of manufactured objects by using their design model. A non-contact measuring method that consists of a stereo-camera system and a single projected fringe pattern is used. The method acquires one image from each camera. Additional shape information from the design model is also used. This surface-measurement method gives an accuracy of about 45 µm. Deviations from the design model within ±1.6 mm can be correctly detected. The measured surface representation is matched to the design model using the ICP-method. Fast performance has been considered adapting the method for on-line use.

  • 319.
    Bergvall, Hannah
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Produkt för rullstolsburnas minskande olycksrisk2019Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Fulltekst (pdf)
    fulltext
  • 320.
    Beronius, Alfred
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    An internal combustion engine intake system and its acoustic properties.2015Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Mufflers are a common measure for attenuation of noise in ducts, such as an intake system of an automotive vehicle. To compare different mufflers against each other it is vital to determine the acoustic properties of the system. There exist several approaches to determine the properties of muffler configurations, either analytical, numerical or by conducting measurements. Transmission loss predicts the properties of a muffler independent of source and termination and is a favorable choice when comparing different sets of muffler configurations against each other. Two methods, the decomposition method and the transfer matrix method are the two common approaches when evaluating the transmission loss of a muffler. In this thesis analytical, numerical and experimental approaches were applied to an expansion chamber and an internal intake system. The results were compared concluding that there was a great agreement between the numerical and analytical approach. The result from experimental measurements on the other hand deviated from the other two, indicating a dysfunctional test rig. The microphone spacing and microphone location was determined as the cause for the erroneous results. Further improvements of the test rig are needed to reassure a functional test setup. Only then can more complex analysis of mufflers, e.g. with an underlying mean flow, be utilized.

  • 321. Bertoni, Alessandro
    et al.
    Bertoni, Marco
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Isaksson, Ola
    Value visualization in Product Service Systems preliminary design2013Inngår i: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 53, s. 103-117Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Emerging from a study in the European aerospace industry, this paper identifies a gap in the way value-related information is communicated to designers of hardware in the preliminary stages of Product Service System (PSS) design. To fit this gap a Lifecycle Value Representation Approach, named LiVReA, that uses color-coded 3D CAD models to enable value information to be translated into visual features, is presented. Such approach aims at enhancing designers' awareness of the value contribution of an early design concept on the overall PSS offer by complementing requirements-based information with criteria reflecting the fulfillment of customers and system value. The paper details the development of the approach, its underlying rationale, the results of preliminary validation activities and the potential for industrial application in the light of the currently available PSS representation tools

    Fulltekst (pdf)
    fulltext
  • 322.
    Bertoni, Alessandro
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Bertoni, Marco
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Johansson, Christian
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Analysing the effects of value drivers and knowledge maturity in preliminary design decision-making.2015Inngår i: ICED 15, VOL 10: DESIGN INFORMATION AND KNOWLEDGE MANAGEMENT, Design Society , 2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The paper presents the results of a three-days experiment to test the use of informationfrom a value assessment model and from a knowledge maturity scale in decisionmakingin preliminary design. A visual analogue scale was used to collect individualinformation from designers through questionnaires. Bivariate statistical analysis wasapplied to study the correlations between both the use of value drivers and knowledgematurity and the designers' awareness of the design problem to be addressed. Resultsshow that value drivers and knowledge maturity information increase the decisionmakers’ awareness of (1) the different perceptions of design team members about theneeds to be satisfied and (2) the technical solution to be developed in the productconcept under consideration.

    Fulltekst (pdf)
    fulltext
  • 323.
    Bertoni, Marco
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Bertoni, Alessandro
    Broeze, Henk
    Dubourg, Gilles
    Sundhurst, Clive
    Using 3D CAD models for value visualization: an approach with SIEMENS NX HD3D Visual Reporting2014Inngår i: Computer-Aided Design and Applications, ISSN 1686-4360, Vol. 11, nr 3, s. 284-294Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recent literature in Systems Engineering has suggested the use of “value” to drive decision-making activities during preliminary design, in particular when choosing technologies and components for a complex system. However, to correctly evaluate design trade-offs, a visual link has to be established between the results of the value model and a product shape/geometry. This paper proposes the use of color-coded 3D CAD models to support the visualization of value analysis results in a Stage-Gate® process. The approach has been developed and exemplified within a case study related to the design of an aero-engine component, and has been demonstrated using SIEMENS NX HD3D Visual Reporting. The results of verification activities conducted in a laboratory setting show that the use of color-coded 3D CAD models increases the decision makers’ awareness of value-related information in a Stage-Gate process.

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  • 324.
    Bertoni, Marco
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Bertoni, Alessandro
    Isaksson, Ola
    Amnell, Henrik
    Johansson, Christian
    Value-oriented concept selection in aero-engine sub-systems design: the EVOKE approach2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Value Driven Design methodologies extend the Requirements Management and Systems Engineering processes to reduce time and costs needed to identify the right solution direction to be pursued in detailed design. Emerging from the findings of an EU FP7 research project, the paper describes an approach, named EVOKE, that uses value as a basis for preliminary concept selection in the design of system components. EVOKE takes as input a list of value dimensions and drivers communicated by the system integrators, together with information about the high-level engineering characteristics of a candidate design, to enable early stage value analysis to be executed the by sub-system manufacturers. The approach and its technological enablers are described in detail through the use of a case study related to the design of new intermediate compressor case for turbofan engines.

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  • 325.
    Bertoni, Marco
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Bertoni, Alessandro
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Johansson, Christian
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för maskinteknik.
    Knowledge Enabled Engineering2015Inngår i: International Workshop of Advanced Manufacturing and Automation, Trans Tech Publications Inc., 2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The development of complex product-service combinations challenges the existing practices for engineering knowledge management. The objective of the paper is to highlight how such practices need to change to meet the engineers’ demand for knowledge when developing “functions” instead of merely hardware. It further proposes Knowledge Enabled Engineering (KEE) as an umbrella term that collects engineering knowledge management methods and tools inspired by the second wave of knowledge management, and that are aimed to meet needs of today’s modern knowledge workers in engineering organizations. The current state of readiness of these approaches is eventually described together with results from verification and validation activities.

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  • 326.
    Bertoni, Marco
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Eres, Hakki
    Scanlan, Jim
    Co-creation in complex supply chains: the benefits of a Value driven Design approach2014Inngår i: Product Development in the Socio-sphere: Game Changing Paradigms for 21st Century Breakthrough Product Development and Innovation / [ed] Schaefer, Dirk, Switzerland: Springer International Publishing , 2014Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    In the last decade, as the manufacturing companies have reconsidered the overall concept of goods production, their focus shifted from developing ‘products’ to ‘solutions’. In complex supply chains, the combination of products and services that maximize customers’ and stakeholders’ value can be identified only if manufacturers improve their ability to co-create, establishing more interactive relationships with end users, clients and sub-contractors. Methodologies for Value Driven Design (VDD) are emerging as enablers for cross-functional and cross-organizational knowledge sharing, reinforcing early stages design iterations to emphasize the maturation of the requirements across supply chain levels. This chapter highlights the uptake of VDD in a traditionally protective domain, such as the aerospace sector. It describes methods and tools for value assessment, and points toward the most relevant initiatives in this domain. Eventually, it discusses areas of further research to promote the effective use of the VDD methodology while designing complex engineering systems.

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  • 327.
    Bertoni, Marco
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Hallstedt, Sophie
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för strategisk hållbar utveckling.
    Isaksson, Ola
    Value assessment of sustainability hotspots in conceptual design: an aerospace study.2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Nowadays, when designing structural aero-engine components, the engineering team does not only deal with aerodynamics and structural mechanics criteria. Rather, it needs to make more informed decisions based on the value and sustainability contribution of a design concept. This paper proposes a novel approach that combines qualitative sustainability assessment techniques, which are Environmental Impact Assessment (EIA) and Strategic Sustainability Assessment (SSA), with Net Present Value (NPV) analysis to facilitate early stage decision-making in design. A case study, related to the development of a new high-temperature aero-engine component, illustrates how EIA and SSA identify sustainability hotspots for a new product technology, and how NPV is used to assess alternative solution strategies within the hotspot. Within the studied case, the milling process was identified as a sustainability hotspot, therefore two process options - Electro-Chemical Milling (ECM) and Mechanical Milling (MM) - where benchmarked by calculating their NPV in alternative future scenarios, featuring different market and regulatory assumptions. The approach and its constituting models have been preliminarily verified with designers and process owners in co-located industrial workshops.

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  • 328. Bertoni, Marco
    et al.
    Johansson, Christian
    Larsson, Tobias
    Methods and Tools for Knowledge Sharing in Product Development2011Inngår i: Innovation in Product Design: From CAD to Virtual Prototyping / [ed] Bordegoni, Monica; Rizzi, Caterina, New York: Springer , 2011, s. 37-53Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    The emerging industrial business partnerships, which feature cross-functional and cross-company development efforts, raise the barrier for the establishment of effective knowledge sharing practices in the larger organization. This chapter aims to highlight the role of knowledge as a key enabler for effective engineering activities in the light of such emerging enterprise collaboration models. Knowledge Enabled Engineering (KEE) is presented as an approach to enhance the extended organization’s capability to establish effective collaboration among its parts, in spite of different organizational structures, technologies or processes. KEE is analysed in its constituent parts, highlighting areas, methods and tools that are particularly interesting for leveraging companies’ knowledge sharing capabilities.

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  • 329. Bertoni, Marco
    et al.
    Larsson, Andreas
    Ericson, Åsa
    Chirumalla, Koteshwar
    Larsson, Tobias
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för maskinteknik.
    Isaksson, Ola
    Randall, Dave
    The rise of social product development2012Inngår i: International Journal of Networking and Virtual Organisations, ISSN 1470-9503, Vol. 11, nr 2, s. 188-207Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of the paper is to discuss the rising potential of social software to increase the knowledge management capabilities of virtual product development teams. It presents six fundamental transitions, elaborated from the empirical findings, which justify the rise of a more bottom-up, social creation and sharing of engineering knowledge in the virtual organisation. The study suggests that traditional engineering knowledge management approaches alone are not sufficient to support development activities in the virtual organisation, and that such teams display an increasing demand for social, comparatively lightweight and remixable platforms for bottom-up, social creation and sharing of knowledge.

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  • 330.
    Bhaduri, Basanta
    et al.
    National University of Singapore.
    Quan, Chenggen
    National University of Singapore.
    Tay, Cho Jui
    National University of Singapore.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Simultaneous measurement of translation and tilt using digital speckle photography2010Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 49, nr 18, s. 3573-3579Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A Michelson-type digital speckle photographic system has been proposed in which one light beam produces a Fourier transform and another beam produces an image at a recording plane, without interfering between themselves. Because the optical Fourier transform is insensitive to translation and the imaging technique is insensitive to tilt, the proposed system is able to simultaneously and independently determine both surface tilt and translation by two separate recordings, one before and another after the surface motion, without the need to obtain solutions for simultaneous equations. Experimental results are presented to verify the theoretical analysis.

  • 331.
    Bhaduri, Basanta
    et al.
    National University of Singapore.
    Tay, C.J.
    National University of Singapore.
    Quan, C.
    National University of Singapore.
    Niu, H.
    National University of Singapore.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Two wavelength simultaneous DSPI and DSP for 3D displacement field measurements2011Inngår i: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 284, nr 10-11, s. 2437-2440Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel optical system is proposed that implements digital speckle pattern interferometry (DSPI) and digital speckle photography (DSP) simultaneously using two wavelength illumination of an object for simultaneous measurement of all three components of the displacement vector field. A collimated red light illuminates both the object and a reference surface in a DSPI configuration which is sensitive to out-of-plane displacement field while a blue light illuminates the object in a DSP configuration which is sensitive to in-plane displacement fields. A color 3-CCD camera records the red and blue lights individually through its red and blue channels, respectively. Two reference images and one image in the deformed state of the object are required for quantitative measurement. Experimental results are presented to validate the system.

  • 332.
    Bhuiyan, Iftekhar Uddin
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Forsmo, S.P.E.
    LKAB, Research & Development, 983 81 Malmberget.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Consideration of X-ray microtomography to quantitatively determine the size distribution of bubble cavities in iron ore pellets2013Inngår i: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 233, s. 312-318Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    X-ray microtomography data of iron ore green pellets of approx. 12 mm in diameter were recorded using a commercial instrument. The reconstructed volume after thresholding represented a unique dataset consisting of a three-dimensional distribution of equiaxed objects corresponding to bubble cavities. This dataset was used to successfully validate a stereological method to determine the size distribution of spherical objects dispersed in a volume. This was achieved by investigating only a few cross-sectional images of this volume and measuring the profiles left by these objects in the cross-sectional images. Excellent agreement was observed between the size distribution of the bubble cavities obtained by directly classifying their size in the reconstructed volume and that estimated by applying the aforementioned stereological method to eight cross-sectional images of the reconstructed volume. Subsequently, we discuss the possibility of calibrating X-ray tomography data quantitatively using the size distribution of the bubble cavities as a figure of merit and the results obtained by applying the stereological method to SEM images as reference data. This was justified by considering the validity of the stereological method demonstrated by tomography, the accurate thresholding made possible by back-scattered electron imaging and the solid reproducibility of the results obtained by SEM. Using different threshold values for binarization of the X-ray microtomography data and comparing the results to those obtained by SEM, we found that X-ray microtomography can be used after proper calibration against SEM data to measure the total porosity of the bubble cavities but can only provide a rough estimate of the median diameter because of the limited resolution achieved in this study.

  • 333.
    Biel, Anders
    et al.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Alfredsson, K. Svante
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Carlberger, Thomas
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Adhesive Tapes; Cohesive Laws for a Soft Layer2014Inngår i: Procedia Materials Science, ISSN 2211-8128, Vol. 3, s. 1389-1393Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    For adhesive tapes, the strain before fracture often exceeds 500%. Although the maximum stresses are quite modest the high strains to fracture result in impressive fracture energy. Due to hydrostatic stress the fracture process often starts by nucleation of microscopic cracks inside the layer. The final crack path is usually close to one of the adherends.

    Repeated experiments are performed both with DCB-specimens and butt-joints. The used adhesive tape is an acrylic foam tape with a thickness of 1.1 mm and a width of 19 mm. The geometry of the specimen is adapted to the properties of the soft layer. For the DCB-specimen this implies that the length of the specimen is about 1 m. The evaluated cohesive laws from the DCB- specimens give a fracture energy of 2 kN/m and a maximum stress about 0.5 MPa. For the butt-joints, the evaluated cohesive law corresponds well to the results from the DCB-experiments. However, the strain to fracture is slightly smaller. The stress in these specimens is distributed over a larger area and a nucleated crack rapidly crosses the load bearing area and fails the joint prematurely. For both kinds of experiments the evaluated cohesive laws show a small linear part. After this part there is an almost linear strain-hardening phase until fracture.

  • 334.
    Biel, Anders
    et al.
    Department of Wind Energy, Technical University of Denmark, Roskilde, Denmark.
    Stigh, Ulf
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Cohesive zone modelling of nucleation, growth and coalesce of cavities2017Inngår i: International Journal of Fracture, ISSN 0376-9429, E-ISSN 1573-2673, Vol. 204, nr 2, s. 159-174Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The stress-deformation relation i.e. cohesive law representing the fracture process in an almost incompressible adhesive tape is measured using the double cantilever beam specimen. As in many ductile materials, the fracture process of the tape involves nucleation, growth and coalesce of cavities. This process is studied carefully by exploiting the transparency of the used materials and the inherent stability of the specimen configuration. Utilising the path independence of the J -integral, the cohesive law is measured. The law is compared to the results of butt-joint tests. The law contains two stress peaks—the first is associated with nucleation of cavities at a stress level conforming to predictions of void nucleation in rubber elasticity. The second stress peak is associated with fracture of stretched walls between fully-grown cavities. After this second peak, a macroscopic crack is formed. The tape suffers at this stage an engineering strain of about 800%. A numerical analysis with the determined cohesive law recreates the global specimen behaviour.

  • 335.
    Biel, Anders
    et al.
    Karlstad University.
    Stigh, Ulf
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Comparison of J-integral methods to experimentally determine cohesive laws in shear for adhesives2019Inngår i: International Journal of Adhesion and Adhesives, ISSN 0143-7496, E-ISSN 1879-0127, Vol. 94, s. 64-75Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High-quality simulation methods demand accurate material models. In simulations an adhesive can be represented by a cohesive layer. A cohesive layer model utilizes a cohesive law to represent the homogenized mechanical behaviour of a layer with a thickness. In the current paper we use three experimental methods to measure the cohesive law in shear using the ENF-specimen; one of the methods is novel and is also useful for evaluation of experiments with the ELS-specimen. Two sets of experiments are performed, one with elastic substrates and one with plastically deforming substrates. Each experiment is evaluated using all three methods. The evaluation shows that all methods provide reasonable data; the results are similar if the substrates are elastic. With smaller specimens, the substrates deform plastically and one of the methods is identified as the most accurate.

  • 336.
    Biel, Anders
    et al.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Stigh, Ulf
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Strength and toughness in shear of constrained layers2018Inngår i: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 138, s. 50-63Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Confined layers may fracture in shear. This occurs, for example in adhesive joints and composite materials. A common mechanism for shear fracture is the formation of shear hackles associated with an expansion of the layer. This makes shear toughness and strength depend on the constraint of the expansion. By constraining the expansion using external loading in experiments, the expansion is reduced but not totally inhibited. The experiments are evaluated using the path independent properties of the J-integral. It is shown that the shear toughness increases for the more constrained case. Thus, from a strength analysis perspective, ignoring the expansion leads to a conservative estimate of the fracture properties. Extrapolation of the evaluated properties to totally inhibited expansions gives the traction separation relation and the fracture toughness for a layer in simple shear.

  • 337.
    Biju, Dona
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära.
    A parametric study of oil-jet lubrication in gear wheels2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    A parametric study of oil-jet lubrication in gear wheels is conducted using Computational Fluid Dynamics (CFD) to study the effect of the different design parameters on the cooling performance in a gearbox. Flow in oil jet lubrication is found to be complex with the formation of oil ligaments and droplets. Various hole radii of 1.5, 2 and 2.5 mm along with five oil velocities is analyzed and it is found that at lower volumetric rates, velocity has more effect on the cooling and at higher volumetric rates, hole size has more effect on the cooling. At higher velocities, the heat transfer is much greater than the actual heat production in the gear wheel, hence these velocity ratios are considered less suitable for jet lubrication. At low velocity ratios of below 2, the oil doesn’t fully impinge the gear bottom land and the sides leading to low cooling. Based on the cooling, impingement length and amount of oil lost to the casing surface, 2 mm hole with a velocity ratio of 2.225 is selected for a successful oil jet lubrication. Varying the inlet position in X, Y and Z directions (horizontal, vertical and lateral respectively) is found to have no improvement on the cooling. Making the oil jet hit the gear wheel surface at an angle is found to increase the cooling. Analysis with the use of a pipe to supply oil was conducted with circular and square inlet and it was found that the heat transfer decreases in both cases due to the splitting of oil jet caused by the combination of the effects of high pressure from the pipe and vorticity in the air field. A method has been developed for two gear analysis using overset meshes which can be used for further studies of jet lubrication in multi-gear systems. Single inlet is found to be better for cooling two gear wheels as it would require a reduced volumetric flow rate compared to double inlets. Oil system requirements for jet lubrication was studied and it was concluded that larger pumps have to be used to provide the high volumetric rates and highly pressurized oil required. On comparing the experimental losses from dip lubrication and the analytical losses for jet lubrication, dip lubrication is found to have lesser loses and more suitable for this case. Good quality lubrication would reduce the fuel consumption and also increase the longevity of gearboxes and hence more research into analyzing alternate lubrication systems can be carried out using the results from this thesis.

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  • 338.
    Bilen Oytun, Peksel
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Advanced Model of Acoustic Trim; Effect on NTF Accuracy2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
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  • 339. Birgersson, F.
    et al.
    Finnveden, Svante
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    A spectral super element for modelling of plate vibration. Part 2: turbulence excitation2005Inngår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 287, nr 02-jan, s. 315-328Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the accompanying paper, the suitability of a spectral super element to predict the response to point force excitation, was demonstrated. This paper expands the element formulation to also include distributed forces, which is useful when studying distributed excitation. First the sensitivity function, i.e. the structural response to a travelling pressure wave, is found. This sensitivity function and a wavenumber frequency description of the wall pressure are then used to predict the response of a turbulence excited panel in a numerically efficient way. The predictions were validated by a conventional finite element method and also compared to measurements.

  • 340. Birgersson, F.
    et al.
    Finnveden, Svante
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Nilsson, C. M.
    A spectral super element for modelling of plate vibration. Part 1: general theory2005Inngår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 287, nr 02-jan, s. 297-314Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The dynamic response of vibrating structures is studied with a proposed merger of the standard finite element method with the more computationally efficient spectral finite element method. First a plate structure is modelled with a newly developed spectral super element. Then this element is coupled to other parts that can have a more complex geometry and are modelled entirely with conventional finite elements. Some numerical examples are given to illustrate and validate the developed method and studies of numerical stability are also presented. In an accompanying paper the predicted and measured response of a turbulence excited aircraft panel are compared.

  • 341.
    Birgersson, Fredrik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Ferguson, Neil S
    Application of the spectral finite element method to turbulent boundary layer induced vibrations of plates2003Inngår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 259, s. 873-891Artikkel i tidsskrift (Fagfellevurdert)
  • 342.
    Bissal, Ara
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Salinas, Ener
    Magnusson, Jesper
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Engdahl, Göran
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    On the Design of a Linear Composite Magnetic Damper2015Inngår i: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 51, nr 11, artikkel-id 8003305Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High-voltage direct current (HVdc) breakers are the key components in the realization of multiterminal HVdc grids. In the presence of fault current, these breakers should be able to deliver impulsive forces to swiftly open the metallic contacts. After the acceleration phase, the moving armature should be decelerated using controllable forces to avoid plastically deforming fragile components integrated in the system. In this paper, finite-element method-based simulation models, complimented with small-scale and large-scale experimental prototypes, were utilized to benchmark different damping topologies. It was found that a Halbach-based configuration can deliver a damping force that is almost two and a half times larger than its sequel. Its sequel, composed of vertically stacked oppositely oriented magnets, is easier to assemble and is also capable of generating a considerable damping force. Finally, it has been shown that both these schemes, inserted in a composite tube, have a potential to be used as dampers in HVdc breakers.

  • 343.
    Bjerkén, Christina
    Malmö högskola, Teknik och samhälle.
    Branching of a dissolution driven stress corrosion crack2009Inngår i: Proceedings of the International Conference on Crack Paths 2009, European Structural Integrity Society , 2009Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Stress corrosion cracking occurs due to the synergistic interaction between mechanical load and corrosion reactions. Some types of stress corrosion crack branch heavily. Here, branching during dissolution driven crack growth is studied using an adaptive FE method. A strain-assisted evolution law is used for the inherently blunted crack. No criterion for crack growth is needed as for a sharp crack, neither for the growth direction. Several simulations are performed with different degrees of load biaxiality. It is found that large biaxiality promotes branching, but no conditions for when branching takes place is found. Instead, branching seems to occur rather randomly due to the perturbation sensitivity of a dissolution driven crack. Also crack growth rates for branched cracks are investigated, and it is found that both constant growth rates can be reached, as well as decreasing rates and eventual arrest. The cracks follow a mode I crack path, however local changes may occur due to the perturbation sensitivity.

  • 344.
    Bjerkén, Christina
    Malmö högskola, Teknik och samhälle.
    Spänningskorrosion - modellering av utveckling från ytojämnheter via gropar till sprickor2007Inngår i: Abstracts Svenska mekanikdagarna, Luleå, Sweden, 2007Konferansepaper (Annet vitenskapelig)
    Abstract [sv]

    Den kombinerade effekten av mekanisk belastning och en korrosiv miljö kan leda till spänningskorrosion. Vid anodisk spänningskorrosion löses materialet upp och bildar korrosionsprodukter. I vissa fall bildas en ytbeläggning, t ex en oxidfilm, som verkar skyddande och därmed bromsar korrosionsprocessen. Om en dylik film inte skapas, eller om den kontinuerligt bryts ned, kan korrosionsprocessen fortgå. I en plan yta kan gropar bildas, och någon eller några av dessa kan i sin tur utvecklas till en kritisk spricka. I denna studie undersöks utvecklingen av korrosionssprickor med hjälp av en modell där korrosionshastigheten är proportionell mot den elastiska töjningsenergin och kurvaturen i varje punkt på ytan. Det är känt sedan tidigare att kurvaturen påverkar benägenheten för atomer att lossna från eller binda vid en yta, vilket leder till att en obelastad yta planar ut vid t ex etsning. Om ytan däremot är belastad kommer en ytojämnhet med ett specifikt frekvensinnehåll att utvecklas. Vågor med längder kortare än en viss kritisk våglängd kommer att avklinga. På detta sätt leder korrosionen till att gropar bildas i ytan och vissa av dessa fördjupas allt mer tills de blir sprickliknande. Dessa spänningskorrosionssprickor kommer dock att ha en finit radie i spetsen som är given av det lokala spänningstillståndet. Simuleringar är gjorda med en adaptiv metod. För varje tidsinkrement beräknas töjningarna i ytan i en finita element-analys, därefter bestäms ytevolutionen och sedan genereras ett nytt elementnät för den uppdaterade geometrin. Resultat från simuleringarna visar utvecklingen från en plan yta, med en initiell pertubation, via gropbildning till sprickor.

  • 345. Bjerkén, Christina
    et al.
    Kao-Walter, Sharon
    Ståhle, Per
    Fracture Mechanisms of a Thin Elastic Plastic Laminate2006Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The fracture toughness of a polymer-metal laminate composite is obtained by mechanical testing of a specimen containing a pre-crack. The laminate is a material used for packaging. It consists of a thin aluminium foil and a polymer coating. A centre cracked panel test geometry is used. Each of the layers forming the laminate is also tested separately. The result is compared with the measured fracture strength of the individual layers. It is observed that the load carrying capacity increases dramatically for the laminate. At the strain when peak load is reached for the laminate only aluminium is expected to carry any substantial load because of the low stiffness of the LDPE. However, the strength of the laminate is almost twice the strength of the aluminium foil. The reason seems to be that the aluminium forces the polymer to absorb large quantities of energy at small nominal strain. The toughness compares well with the accumulated toughness of all involved layers. Possible fracture of the interface between the layers is discussed.

    Fulltekst (pdf)
    FULLTEXT01
  • 346.
    Bjerkén, Christina
    et al.
    Malmö högskola, Teknik och samhälle.
    Melin, Solveig
    Growth of a short fatigue crack - A long term simulation using a dislocation technique2009Inngår i: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 46, nr 5, s. 1196-1204Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, the growth of a short edge crack during more than 14 000 cycles of fatigue loading is investigated in detail. An edge crack, in a semi-infinite body with no pre-existing obstacles present, is modelled in a boundary element approach by a distribution of dislocation dipoles. The fatigue cycles are fully reversed (R = -1), and the load range is well below the threshold for long fatigue cracks. The developing local plasticity consists of discrete edge dislocations that are emitted from the crack tip. The movements of discrete dislocations are restricted to slip along preferred slip planes. The present model is restricted to a 2D plane strain problem with a through-thickness crack, assuming no 3D irregularities. A remote load is applied perpendicular to the crack extension line, and the material parameters are those of a BCC crystal structure. The competition between influence of the global loading on and local shielding of the crack tip governs the crack growth. The growth rate increases in discrete steps with short periods of retardation, from approximately the size of Burgers vector, b, up to 25 b per cycle as the length of the crack is tripled. The plastic zone changes from having an elongated, slender form to include a low angle grain boundary, which, eventually, divides into two parts. The crack growth is found to change from constant acceleration to constant growth rate as the event of the low-angle grain boundary split is approached. ; The results are compared to long crack characteristics, for which linear elastic fracture mechanics and Paris law can be used to predict fatigue crack growth. The exponent in Paris law varies between 1 and 0 in the present study, i.e. smaller than typical values for ductile BCC materials. The ratio between static and cyclic plastic zone sizes is found to increase during crack growth, and the angle of the general plastic zone direction increases, showing a tendency towards long crack values. The characteristics of the simulated crack growth, found in the present study, are typical for below-threshold growth, with slow acceleration, constant growth rate. and, eventually, either arrest or transition to long crack growth behaviour, as reported in the literature.

  • 347.
    Bjerkén, Christina
    et al.
    Malmö högskola, Teknik och samhälle.
    Ortiz, Michael
    Evolution of anodic stress corrosion cracking in a coated material2010Inngår i: International Journal of Fracture, ISSN 0376-9429, E-ISSN 1573-2673, Vol. 165, nr 2, s. 211-221Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present paper, we investigate the influence of corrosion driving forces and interfacial toughness for a coated material subjected to mechanical loading. If the protective coating is cracked, the substrate material may become exposed to a corrosive media. For a stress corrosion sensitive substrate material, this may lead to detrimental crack growth. A crack is assumed to grow by anodic dissolution, inherently leading to a blunt crack tip. The evolution of the crack surface is modelled as a moving boundary problem using an adaptive finite element method. The rate of dissolution along the crack surface in the substrate is assumed to be proportional to the chemical potential, which is function of the local surface energy density and elastic strain energy density. The surface energy tends to flatten the surface, whereas the strain energy due to stress concentration promotes material dissolution. The influence of the interface energy density parameter for the solid-fluid combination, interface corrosion resistance and stiffness ratios between coating and substrate is investigated. Three characteristic crack shapes are obtained; deepening and narrowing single cracks, branched cracks and sharp interface cracks. The crack shapes obtained by our simulations are similar to real sub-coating cracks reported in the literature.

    Fulltekst (pdf)
    FULLTEXT01
  • 348.
    Bjerkén, Christina
    et al.
    Malmö högskola, Teknik och samhälle.
    Rimoli, Julian
    Ortiz, Michael
    Stress corrosion crack growth beneath a stiff coating: influence of chemical potential and interface toughness2009Inngår i: Proceedings 12th International Conference on Fracture, Ottawa 2009, ICF12 , 2009Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In the present paper we investigate the influence of corrosion driving forces and interfacial toughness for a coated material subjected to mechanical loading. If the protecting coating is cracked, the substrate material may become exposed to a corrosive media. For a stress corrosion sensitive substrate material, this may lead to detrimental crack growth. A crack is assumed to grow by anodic dissolution, inherently leading to a blunted crack tip. The rate of dissolution along the crack surface is assumed to be proportional to the chemical potential, which is function of the local surface energy density and the elastic strain energy density. The surface energy tends to flatten the surface, whereas the strain energy due to stress concentration promotes material dissolution. The evolution of the crack surface is modelled as a moving boundary problem using an adaptive finite element method. The crack shapes obtained by our simulations are remarkably similar to real stress corrosion cracks reported in the literature.

  • 349.
    Bjerkén, Christina
    et al.
    Malmö högskola, Teknik och samhälle.
    Ståhle, Per
    Malmö högskola, Teknik och samhälle.
    Branching of growing corrosion fatigue cracks2005Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Strain-driven corrosion of branching cracks, initiated from a virtually plane surface, has been studied using a moving boundary technique. The material is assumed linear elastic and is subjected to fatigue loading under plain strain conditions. The surface of the material is covered by a protective film. During loading this film can be damaged if it is strained above a threshold value, thus revealing an unprotected surface. Corrosion advances by material dissolution, eventually evolving into cracks. The rate of surface evolution is a function of the degree of protective film damage. During unloading the protective film is assumed to develop and heal the surface. A low frequency cyclic loading is applied to ensure that total healing is assumed. The moving boundary technique, simulating corrosion, results in arc-shaped crack tips, rather than singular crack tip points, thus no crack growth criterion is needed in the analysis. For each load step, the strain distribution is found using the finite element method, followed by required the movement the boundary and then remeshing. The crack growth has been investigated for at least 2000 cycles. A more or less pronounced branching of the cracks is found to develop. The crack branches can be classified in three groups; main cracks that grows with maximum rate and branches further, branch cracks that initially retards and then find a steady state growth rate that is a fraction of maximum speed, and finally, arresting cracks that after a period of retardation stop growing. The crack patterns are realistic, showing a sort of self-similarity with tree-like structure, cf. the picture below that shows a typical finite element result. The width of a crack branch together with the shielding from the applied stresses, caused by the other branches and main cracks, seem to govern the evolution of the crack branch. A steady-state growth rate is achieved during parts of the evolution as the crack width and the strain field surrounding the crack tip is in balance, i.e. the crack widens while the crack grows longer. As the bluntness of the tip reaches an upper limit, branching results.

  • 350.
    Bjerkén, Christina
    et al.
    Malmö högskola, Teknik och samhälle.
    Ståhle, Per
    Malmö högskola, Teknik och samhälle.
    Simulation of corrosion fatigue crack growth under mixed-mode loading2008Inngår i: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 75, nr 3-4, s. 440-451Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The kinking of a corrosion crack due to mixed-mode fatigue loading is studied using an adaptive finite element procedure. The rate of material dissolution is assumed to be proportional to the stretching of the corroding surface. The dissolution of material is governed by a corrosion law, where no criterion is needed for neither crack growth nor growth direction. The problem is treated as a general moving boundary problem. The kink angles are found to be in very good agreement with results for sharp cracks using criteria reported in the literature.

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