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  • 51.
    Aidanpää, Jan-Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lindkvist, Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Dynamics of a rubbing Jeffcott rotor with three blades2011Inngår i: Chaos Theory: Modeling, Simulation and Applications: Selected Papers from the 3rd Chaotic Modeling and Simulation International Conference (CHAOS2010) / [ed] Christos H. Skiadas; Ioannis Dimotikalis; Charilaos Skiadas, Singapore: World Scientific Publishing Co Pte Ltd , 2011, Vol. Part II. Invited and Contributed Papers, s. 97-104Konferansepaper (Fagfellevurdert)
  • 52.
    Aidanpää, Jan-Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Lundström, Niklas L. P.
    Umeå university.
    Complex dynamic responses due to deviations of generator shape2009Inngår i: 10th Conference on Dynamical Systems - Theory and Applications: DSTA-2009, December 7-10, Łódź, Poland, 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Earlier measurements in large synchronous generators indicate the existence of complex whirling motion, and also deviations of shape in both the rotor and the stator. These non-symmetric geometries produce an attraction force between the rotor and the stator, called Unbalanced Magnetic Pull (UMP). The target of this paper is to analyse responses due to certain deviations of shape in the rotor and the stator. In particular, the perturbation on the rotor is considered to be of oval character, and the perturbations of the stator are considered triangular and eccentric. It is concluded that harmful conditions can occur due to high amplitudes especially when the whirling of the rotor changes from forward to backward. During maintenance of hydro power generators the shapes of the rotor and stator are frequently measured. The results from this paper can be used to evaluate such measurements and to explain the existence of complex whirling motion.

  • 53.
    Aidanpää, Jan-Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Shen, Hayley
    Clarkson University, Potsdam, NY.
    Onset of transition for cohesive and viscous granular flows1998Inngår i: Journal of engineering mechanics, ISSN 0733-9399, E-ISSN 1943-7889, Vol. 124, nr 10, s. 1073-1079Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A theory for determining the onset of rapid flow or termination of quasi-static flow in a cohesive granular material mixed in a viscous interstitial fluid is presented. This theory is based on a one-dimensional model introduced in an earlier paper. Linear stability analysis is used to find the combination of material properties and flow rate for which a quasi-static flow becomes unstable, indicating the onset of rapid flow. This theory yields a quantitative criterion to select appropriate constitutive laws for viscous and cohesive granular material. This criterion is a linear approximation of the theoretical result. While it provides the critical condition for quasi-static flow to terminate, it does not give the transitional constitutive law before a rapid flow is fully developed, for which a second power law dependence on the strain rate applies. Nonetheless, the analysis and modeling effort presented in this work are necessary first steps toward a general quantification of how granular materials, with identical physical composition, can behave in drastically different ways.

  • 54.
    Aidanpää, Jan-Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Shen, Hayley H.
    Gupta, Ram B.
    Uppsala universitet.
    Experimental and numerical studies of shear layers in granular shear cell1996Inngår i: Journal of engineering mechanics, ISSN 0733-9399, E-ISSN 1943-7889, Vol. 122, nr 3, s. 187-196Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The stability of a shear layer inside a granular material in a gravity field is studied experimentally and numerically. A shear cell is built of transparent acrylic to visualize the motion of the granular material. This shear cell consists of two concentric cylinders containing layers of uniform spheres in the annular space between the cylinders. The shearing motion of the spheres is produced by rotating the bottom boundary of the cell. Friction of the cylinder walls resists the shear motion, thus creating a single shear layer adjacent to the bottom boundary, while the rest of the layers above move with constant speed as a solid body. As the rotation speed of the bottom boundary increases, two layers adjacent to the bottom boundary begin to shear. This shearing zone quickly thickens and dilates as the rotational speed increases. The transition of this shear motion from a single layer to many layers of shearing is studied by video recording. The initiation of this transition is observed to depend on the material properties and the number of layers overlaying the shear layer. A one-dimensional numerical model is constructed to bring insight into this transitional phenomenon.

  • 55.
    Aidanpää, Jan-Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Shen, Hayley H.
    Department of Civil and Environmental Engineering, Clarkson university.
    Gupta, Ram B.
    Division of Solid Mechanics, School of Engineering, Uppsala University.
    Stability and bifurcations of a stationary state for an impact oscillator1994Inngår i: Chaos, ISSN 1054-1500, E-ISSN 1089-7682, Vol. 4, nr 4, s. 621-630Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The motion of a vibroimpacting one-degree-of-freedom model is analyzed. This model is motivated by the behavior of a shearing granular material, in which a transitional phenomenon is observed as the concentration of the grains decreases. This transition changes the motion of a granular assembly from an orderly shearing between two blocks sandwiching a single layer of grains to a chaotic shear flow of the whole granular mass. The model consists of a mass-spring-dashpot assembly that bounces between two rigid walls. The walls are prescribed to move harmonically in opposite phases. For low wall frequencies or small amplitudes, the motion of the mass is damped out, and it approaches a stationary state with zero velocity and displacement. In this paper, the stability of such a state and the transition into chaos are analyzed. It is shown that the state is always changed into a saddle point after a bifurcation. For some parameter combinations, horseshoe-like structures can be observed in the Poincare sections. Analyzing the stable and unstable manifolds of the saddle point, transversal homoclinic points are found to exist for some of these parameter combinations

  • 56.
    Aidanpää, Jan-Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Shen, H.H.
    Clarkson University, Potsdam, NY.
    Gupta, R.
    Luleå tekniska universitet.
    Babic, M.
    University of Notre Dame, Notre Dame, IN.
    A model for the transitional behavior of simple shear flows of disks1992Inngår i: Studies in Applied Mechanics, ISSN 0922-5382, Vol. 31, s. 301-310Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A simple one-dimensional model is suggested to simulate some aspects of the dynamics of granular shear flows. The model consists of a viscoelastic packet bouncing between two harmonically oscillating walls. The amplitude and frequency of the wall motion are related to the concentration and shear rate respectively. The dynamics of the system is studied and it is shown that periodic as well as chaotic motions are possible for different parameters and initial conditions. Results are presented in the form of time histories, power spectral densities, phase diagrams, Poincaré maps and bifurcation diagrams. Some of the characteristics present in the two-dimensional granular shear flows are present in this simple model. It is promising that such analysis can provide better understanding of the transitional behavior of the constitutive relation between the rapid shear and the quasi-static flows.

  • 57.
    Aidanpää, Jan-Olov
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Shen, H.H.
    Gupta, R.B.
    Babic, M.
    One-dimensional model for the transition from periodic to chaotic motions in granular shear flows1993Inngår i: Mechanics of materials (Print), ISSN 0167-6636, E-ISSN 1872-7743, Vol. 16, nr 1-2, s. 153-161Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A simple one-dimensional mechanical model to simulate some aspects of the dynamics of granular flow is suggested. The model consists of a visco-elastic packet bouncing between two oscillating walls. The motion of the walls is prescribed to be harmonic. The amplitude and frequency of the wall motion are related to the concentration and shear rate, respectively. The dynamics of the system is studied for various parameter combinations and it is shown that periodic as well as chaotic motions are possible for different parameters and initial conditions. Results are presented in the form of time histories, power spectral densities, phase diagrams, Poincare plots and bifurcation diagrams. This simple one-dimensional model presents many features that are analogous to those observed in the two-dimensional simple shear flow of disks.

  • 58.
    Alam, Md. Minhaj
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Barsoum, Z
    Royal Institute of Technology, Department of Aeronautical and Vehicle Engineering, Stockholm.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Influence of defects on fatigue crack propagation in laser hybrid welded eccentric fillet joint2011Inngår i: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 78, nr 10, s. 2246-2258Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fatigue cracking of laser hybrid welded eccentric fillet joints has been studied for stainless steel. Two-dimensional linear elastic fracture mechanics analysis was carried out for this joint geometry for four point bending load. The numerical simulations explain for the experimental observations why the crack propagates from the lower weld toe and why the crack gradually bends towards the root. Lack of fusion turned out to be uncritical for the initiation of cracks due to its compressive stress conditions. The linear elastic fracture mechanics analysis has demonstrated in good qualitative agreement with fatigue test results that lack of fusion slightly (<10%) reduces the fatigue life by accelerating the crack propagation. For the geometrical conditions studied here improved understanding of the crack propagation was obtained and in turn illustrated. The elaborated design curves turned out to be above the standard recommendations

  • 59.
    Alam, Md. Minhaj
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Barsoum, Z.
    Royal Institute of Technology.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Kaplan, Alexander
    Häggblad, Hans-Åke
    The influence of surface geometry and topography on the fatigue cracking behaviour of laser hybrid welded eccentric fillet joints2010Inngår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 265, nr 6, s. 1936-1945Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Laser hybrid welding of an eccentric fillet joint causes a complex geometry for fatigue load by four point bending. The weld surface geometry and topography were measured and studied in order to understand the crack initiation mechanisms. The crack initiation location and the crack propagation path were studied and compared to Finite Element stress analysis, taking into account the surface macro- and micro-geometry. It can be explained why the root and the upper weld toe are uncritical for cracking. The cracks that initiate from the weld bead show higher fatigue strength than the samples failing at the lower weld toe, as can be explained by a critical radius for the toe below which surface ripples instead determine the main stress raiser location for cracking. The location of maximum surface stress is related to a combination of throat depth, toe radius and sharp surface ripples along which the cracks preferably propagate.

  • 60.
    Alam, Md. Minhaj
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Barsoum, Zuheir
    Kungliga tekniska högskolan, KTH.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-Åke
    Kaplan, Alexander
    Fatigue behaviour study of laser hybrid welded eccentric fillet joints: Part I2009Inngår i: 12th NOLAMP proceeding 2009: Nordic Laser Materials Processing Conference ; 24th - 26th August 2009 in Copenhagen / [ed] Erling Dam Mortensen, Kgs. Lyngby: ATV-SEMAPP , 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Welded joints are a major component that is often responsible for causing a structure failure or for being the point at which fatigue cracking initiates and propagates. Despite tremendous research efforts, the understanding of fatigue behaviour is still limited, particularly for new techniques like laser hybrid welding. Beside a comprehensive state-of-the-art study, the paper presents a fatigue study of laser hybrid welded eccentric fillet joint of stainless steel of 10 mm thickness, with 5 mm displacement. Motivation is to study the influence of the surface geometry shape on fatigue performance under a four point bending test. 13 samples were produced, measuring the toe radii and testing under constant amplitude loading with stress ratio R=0. Different techniques have been used to measure local weld geometry, like plastic replica, a 3D optical profiler and a 3D-digitizer. The influence of the local weld geometry, like the toe radii, on the stress concentration was studied by FE-analysis. Occasionally lack of fusion was observed, which was taken into account in the FE-analysis. Based on the nominal stress approach, SN-curves were designed for laser hybrid welded eccentric fillet joints. Macro hardness tests were carried out and the crack surfaces were observed in order to detect crack initiation and propagation. Correlations between the toe radii, the corresponding stress maxima and crack initiation locations were studied between the different samples and even along the welds.

  • 61.
    Alam, Md. Minhaj
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Barsoum, Zuheir
    Kungliga tekniska högskolan, KTH.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Fatigue behaviour study of laser hybrid welded eccentric fillet joints: Part II: State-of-the-art of fracture mechanics and fatigue analysis of welded joints2009Inngår i: 12th NOLAMP proceeding 2009: Nordic Laser Materials Processing Conference ; 24th - 26th August 2009 in Copenhagen / [ed] Erling Dam Mortensen, Kgs. Lyngby: ATV-SEMAPP , 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Simplified fatigue and fracture mechanics based assessment methods are widely used by the industry to determine the structural integrity significance of postulated cracks, manufacturing flaws, service-induced cracking or suspected degradation of engineering components under normal and abnormal service loads. In many cases, welded joints are the regions most likely to contain original fabrication defects or cracks initiating and growing during service operation. The welded joints are a major component that is often blamed for causing a structure failure or for being the point at which fatigue or fracture problems initiate and propagate. Various mathematical models/techniques for various classes of welded joints are developed by analytically or by simulation software's that can be used in fatigue and fracture assessments. This literature survey compiled useful information on fracture and fatigue analysis of various welded joints. The present review is divided into two major sections- fracture mechanics and fatigue analysis with widely used models. A survey table is also introduced to get the outlook of research trend on fatigue and fracture over last 3 decades. Although tremendous research effort has been implemented on fatigue and fracture analysis of conventional welding, research on relatively new welding technology (laser welding, hybrid laser welding) is still limited and unsatisfactory. In order to give guarantee or make welding standard for new welding technology, further research is required in the field of fatigue and fracture mechanics including FEM and multi-scale modeling.

  • 62.
    Alam, Md. Minhaj
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Barsoum, Zuheir
    Royal Institute of Technology.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-Åke
    Kaplan, Alexander
    Geometrical aspects of the fatigue behaviour of laser hybrid fillet welds2009Inngår i: Proceedings of the Fatigue Design Conference, Cetim , 2009Konferansepaper (Fagfellevurdert)
  • 63.
    Alam, Md. Minhaj
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Barsoum, Zuheir
    Royal Institute of Technology.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Kaplan, Alexander
    Häggblad, Hans-Åke
    The effects of surface topography and lack of fusion on the fatigue strength of laser hybrid welds2009Inngår i: Congress proceedings: ICALEO, 28th International Congress on Applications of Lasers & Electro-Optics : November 2 - 5, 2009 - Orlando, FL : Laser Materials Processing Conference, Laser Microprocessing Conference, Nanomanufacturing Conference, poster presentation, gallery, Orlando, Fla: Laser institute of America , 2009, s. 38-46Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The geometrical aspects of laser hybrid welding before, during and after the process differ from autonomous laser welding and from arc welding. When studying the fatigue behaviour of laser hybrid welded fillet joints we identified that the microgeometry, i.e. the surface ripples can be more critical than the macrogeometry of the weld surface and even than lack of fusion (LOF), which frequently was detected. The plastic replica method was applied to measure the toe radii at the weld edges while the topography was identified by interferometric profilometry. From metallurgical analysis of the joint interface the tendency to LOF can be explained. Stress analysis was carried out by FEA for the complex joint geometry and bending load situation, showing maximum stress on the weld toes, even when including LOF. It was shown that the position and value of the maximum stress depends on a non-trivial combination of the weld geometry, including possible LOF, and the surface topography. Thus it can be explained that at compressive stress conditions LOF does not contribute significantly to the fatigue strength of laser hybrid welds while the surface topography does. Recommendations for defining and in turn avoiding critical geometrical aspects during the welding process are discussed.

  • 64. Alam, Minhaj M
    et al.
    Barsoum, Zuheir
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Jonsén, Pär
    Häggblad, Hans Åke
    Kaplan, Alexander
    Geometrical Aspects of The Fatigue Behaviour of Laser Hybrid Fillet Welds2009Inngår i: Proceedings of the Fatigue Design Conference, 2009Konferansepaper (Fagfellevurdert)
  • 65.
    Alaniz, Monica
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Belyayev, Serhiy
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Bergman, David
    Casselbrant, Gustav
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Honeth, Mark
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Huang, Jiangwei
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Ivchenko, Nickolay
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Laukkanen, Mikko
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Michelsen, Jacob
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Pronenko, Vira
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Paulson, Malin
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Schlick, Georg
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Tibert, Gunnar
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Valle, Mario
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    The SQUID sounding rocket experiment2011Inngår i: Proceedings of the 20th ESA Symposium on European Rocket and Balloon Programmes and Related Research, European Space Agency, 2011, s. 159-166Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The objective of the SQUID project is to develop and in flight verify a miniature version of a wire boom deployment mechanism to be used for electric field measurements in the ionosphere. In February 2011 a small ejectable payload, built by a team of students from The Royal Institute of Technology (KTH), was launched from Esrange on-board the REXUS-10 sounding rocket. The payload separated from the rocket, deployed and retracted the wire booms, landed with a parachute and was subsequently recovered. Here the design of the experiment and post fight analysis are presented.

  • 66. Alberdi, A.
    et al.
    Gil-Negrete, N.
    Vinolas, J.
    Kari, Leif
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Nieto, F. J.
    Dynamic characterisation of different magneto-sensitive natural rubbers for application in vibration isolation2010Inngår i: Proceedings of ISMA 2010 - International Conference on Noise and Vibration Engineering, including USD 2010, Katholieke Universiteit Leuven , 2010, s. 227-231Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Dynamic properties of magneto-sensitive natural rubber components were experimentally studied. Different magneto-sensitive rubbers were manufactured, consisting of irregularly shaped micron-sized iron particles embedded in a natural rubber matrix, and the influence of the hardness of the matrix material and the particle volume concentration were analyzed. Vibration isolators consisting of magneto-sensitive elastomers promise to have more functionality than conventional isolators as they can change their dynamic stiffness rapidly, continuously and reversibly under the application of an external magnetic field. Experimental measurements on MS components show that a better performance may be obtained at applications where small amplitudes are required, using soft matrix materials and with concentration close to a critical particle volume fraction.

  • 67.
    Alberdi-Muniain, Ane
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Magneto-sensitive elastomers in vibration isolation2012Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Vibration isolators made of rubber are used in numerous engineeringapplications to isolate structures from undesirable effects of vibrations.However, once a vibration isolator is installed in an application, it is not possible to modify its characteristics to adjust to changing conditions. An alternative to obtain more adaptive characteristics is touse magneto-sensitive (MS) elastomers. MS elastomers are a type of smart material consisting of an elastomer matrix, such as natural or synthetic rubber, to which iron particles are added displaying properties that vary rapidly, continuously and reversibly by applying an external magnetic field.The aim of this thesis is to investigate the possibility to use MS natural rubber in vibration isolation.Firstly, dynamic shear properties of MS natural rubber are experimentally studied at various frequencies, dynamic amplitudes and magnetic fields. In addition, the influence on the dynamic properties of adding carbon black and plasticisers to MS rubber is investigated. Carbon black is the most popular reinforcing filler that rubber usually contains in engineering applications to improve mechanical properties where as plasticisers simplify the filler blending process.Furthermore, the effectiveness of MS rubber applied in a vibration isolation system is experimentally investigated by measuring the energy flow into the foundation. The energy flow, including both force and velocity of the foundation, is a suitable measure of the effectiveness of a real vibration isolation system where the foundation is not perfectly rigid. The vibration isolation system in this study consists of a solid aluminium mass excitedby an electro-dynamic shaker and mounted upon four nonlinear frequency,amplitude and magnetic field dependent MS isolators being connected to a relatively stiff foundation. The energy flow through the MS isolators is directly measured by inserting a force transducer below each isolator andan accelerometer on the foundation close to each isolator. MS isolators are shown to be more useful than conventional rubber isolators since the dynamic stiffness varies with the application of an external magnetic field,thus resulting in more effective vibration isolation. In addition, the indirect technique is employed to measure the energy flow while requiring only accelerometers since it is usually difficult to directly measure the force in a real application. The indirect technique is validated by direct measurements.Finally, a model of the energy flow through the nonlinear frequency,amplitude and magnetic field dependent MS isolators is developed for the tested vibration isolation system. Vibration isolators are usually only a small connecting component within a more complex system. Hence, simple discrete models are frequently used to characterise the frequency and dynamic amplitude dependence of rubber. Recently, a model of this type has been modified to include magneto-sensitivity and thus model MS rubber. In this study, this novel MS rubber model is incorporated into the full system to model the MS isolators while the foundation is characterised by its driving-point and transfer inertances at and between the connection points.The energy flow model results are compared to those of measurements,showing good agreement. The developed energy flow model provides a basis to design vibration isolator systems made of MS isolators.

  • 68.
    Alberdi-Muniain, Ane
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Gil-Negrete, N.
    Department of Applied Mechanics, CEIT and Tecnun (University of Navarra).
    Kari, Leif
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Direct energy flow measurement in magneto-sensitive vibration isolator systems2012Inngår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 331, nr 9, s. 1994-2006Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effectiveness of highly nonlinear, frequency, amplitude and magnetic field dependent magneto-sensitive natural rubber components applied in a vibration isolation system is experimentally investigated by measuring the energy flow into the foundation. The energy flow, including both force and velocity of the foundation, is a suitable measure of the effectiveness of a real vibration isolation system where the foundation is not perfectly rigid. The vibration isolation system in this study consists of a solid aluminium mass supported on four magneto-sensitive rubber components and is excited by an electro-dynamic shaker while applying various excitation signals, amplitudes and positions in the frequency range of 20-200 Hz and using magneto-sensitive components at zero-field and at magnetic saturation. The energy flow through the magneto-sensitive rubber isolators is directly measured by inserting a force transducer below each isolator and an accelerometer on the foundation close to each isolator. This investigation provides novel practical insights into the potential of using magneto-sensitive material isolators in noise and vibration control, including their advantages compared to traditional vibration isolators. Finally, nonlinear features of magneto-sensitive components are experimentally verified.

  • 69.
    Alberdi-Muniain, Ane
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Gil-Negrete, N
    Kari, Leif
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Indirect energy flow measurement in magneto-sensitive vibration isolator systems2013Inngår i: Applied Acoustics, ISSN 0003-682x, ISSN 0003-682x, Vol. 74, nr 4, s. 575-584Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    The indirect energy flow measurement method is extended to cover highly nonlinear, frequency, amplitude and magnetic field dependent magneto-sensitive natural rubber isolators applied in a real vibration isolation system. Energy flow is an effective measure of vibration isolation while being a single quantity that considers both force and velocity. The use of the indirect technique is of interest while requiring only accelerometers since it is usually difficult to directly measure the force in a real application. The vibration isolation system is composed of four magneto-sensitive rubber isolators that are inserted under a vibrating source consisting of a solid aluminium mass excited by an electro-dynamic shaker. Magneto-sensitive rubber isolators are more useful than conventional rubber isolators since the dynamic stiffness varies with the application of an external magnetic field, thus resulting in more effective vibration isolation. Various approximations regarding the indirect technique are investigated, concluding that average stiffness of magneto-sensitive isolators can be used and auto-spectrum of the foundation velocity ignored. In addition, various error analyses are performed. Finally, the indirect measurement of the energy flow is validated by direct measurements, showing very good agreement.

  • 70.
    Alberdi-Muniain, Ane
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Gil-Negrete, N
    Kari, Leif
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Modelling energy flow through magneto-sensitive vibration isolators2013Inngår i: International Journal of Engineering Science, ISSN 0020-7225, E-ISSN 1879-2197, Vol. 65, s. 22-39Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A highly nonlinear model of the energy flow in a magneto-sensitive (MS) vibration isolation system is developed where it is possible to investigate the influences of MS rubber material parameters; magnetic field strength; MS isolator dimension and position; excitation force magnitude, position and frequency; engine mass, inertia and dimension and, finally, foundation inertance. The MS vibration isolation system consists of an engine modelled by a solid mass, excited by a vertical force and mounted upon four MS isolators being connected to a relatively stiff foundation characterised by its driving-point and transfer inertances at and between the connection points. The energy flow into the foundation is the most appropriate indicator of the effectiveness of a real vibration isolation system while considering both foundation velocity and force. The MS isolator model applied is a nonlinear MS rubber model including frequency, dynamic amplitude and magnetic field dependence. The energy flow model results are compared to those of measurements, showing good agreement. Finally, parameter studies are carried out. The developed energy flow model provides a basis for designing MS vibration isolation systems to meet specific requirements.

  • 71.
    Alberdi-Muniain, Ane
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Gil-Negrete, N.
    Department of Applied Mechanics, CEIT and Tecnun (University of Navarra).
    Nieto, F.J.
    Department of Applied Mechanics, CEIT and Tecnun (University of Navarra).
    Kari, Leif
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Vinolas, J.
    Department of Applied Mechanics, CEIT and Tecnun (University of Navarra).
    An experimental study of magneto-sensitive natural rubber components applied in a vibration isolation system2009Inngår i: CONSTITUTIVE MODELS FOR RUBBER VI / [ed] Gert Heinrich, Michael Kaliske, Alexander Lion, London: Taylor & Francis, 2009, s. 99-104Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The effectiveness of magneto-sensitive natural rubber components applied in a vibration isolation system is experimentally investigated, where influences of excitation position, amplitude, frequency and magnetic field are examined. The magneto-sensitive elastomer consists of micron-sized, irregularly shaped iron particles blended in soft natural rubber at a concentration close to the critical particle volume fraction, shown to be the most favorable composition for optimum behaviour. A rigid aluminium mass supported on four vibration isolators is excited by an electro-dynamic shaker. Each component of this vibration isolation system is composed of two thin, square shaped, symmetrically positioned magneto-sensitive elements excited in simple shear with a magnetic field applied perpendicularly to the motion by an electromagnet. The magnetic field is varied by applying different intensities through the coil. The excitation position is either on the centre or on the edge of the surface of the mass, using step-sine excitation of various amplitudes in the frequency range of 0 to 300 Hz. The results show that it is possible to use magneto-sensitive rubber for vibration control purposes.

  • 72.
    Albernaz, Daniel L.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Do-Quang, Minh
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Hermanson, J. C.
    Amberg, Gustav
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Fysiokemisk strömningsmekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Droplet deformation and heat transfer in isotropic turbulence2017Inngår i: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 820, s. 61-85Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The heat and mass transfer of deformable droplets in turbulent flows is crucial. to a wide range of applications, such as cloud dynamics and internal combustion engines. This study investigates a single droplet undergoing phase change in isotropic turbulence using numerical simulations with a hybrid lattice Boltzmann scheme. Phase separation is controlled by a non-ideal equation of state and density contrast is taken into consideration. Droplet deformation is caused by pressure and shear stress at the droplet interface. The statistics of thermodynamic variables are quantified and averaged over both the liquid and vapour phases. The occurrence of evaporation and condensation is correlated to temperature fluctuations, surface tension variation and turbulence intensity. The temporal spectra of droplet deformations are analysed and related to the droplet surface area. Different modes of oscillation are clearly identified from the deformation power spectrum for low Taylor Reynolds number Re, whereas nonlinearities are produced with the increase of Re A, as intermediate frequencies are seen to overlap. As an outcome, a continuous spectrum is observed, which shows a decrease in the power spectrum that scales as similar to f(-3) Correlations between the droplet Weber number, deformation parameter, fluctuations of the droplet volume and thermodynamic variables are also developed.

  • 73.
    Albertsson, Robin
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Sjöfartshögskolan (SJÖ).
    Hermansson, Joakim
    Linnéuniversitetet, Fakulteten för teknik (FTK), Sjöfartshögskolan (SJÖ).
    LNG träningsmanual för M/T Bit Viking2013Independent thesis Basic level (university diploma), 10 hpOppgave
    Abstract [sv]

    Denna uppsats är gjord på uppdrag av Tarbit Shipping som år 2011 konverterade sin tankbåt M/T Bit Viking från konventionell drift på tjockolja till LNG (Liquefied Natural Gas).Uppdraget som gavs var att upprätta en tränings manual till fartyget då det är ett krav från IMO (International Maritime Organization). Manualen skrevs i 3 st huvuddelar Kategori A, B och C. Kategori A är till för att manskap ombord ska få en kännedom om gasen och säkerhet runt den, Kategori B är skriven till däcksbefäl där det krävs en större kännedom om gasen och Kategori C är till för maskinbefäl. Manualen finns nu ombord på fartyget och på rederi kontoret för utbildning av nypåmönstrad personal och fortlöpande utbildning av ordinarie personal. Manualen är ett resultat på tolkning av IMO´s IGF kod (ANNEX11. RESOLUTION MSC.285(86)) där det står riktlinjer för säkerheten ombord på fartyg med maskiner som drivs på naturgas.

  • 74.
    Alexander, Mattsson
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap.
    Engine stability: A study of the events occurring prior to thecombustion in a small two-stroke engine2017Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    This thesis is a study conducted in collaboration with the engine performance group atHusqvarna AB. The study focuses on engine stability of smaller two stroke handheld enginesrunning on E10 (10% ethanol mixture in gasoline). The reason for the study is the new EUproposition that by 2020 all fuel must have 10 % renewable fuel content. To meet thisproposition Husqvarna has evaluated E10 and found that the engine stability of smaller twostroke engines are affected in a negative way by the fuel.The study focuses on events occurring prior to the combustion and mainly the carburetor. Theobjective for the thesis is to seek what contribution the events occurring prior to thecombustion have to the engine stability and find simple and implantable solution to improvethe stability with regards to the carburetor.The study has been conducted in three different work packages, system understanding to buildknowledge of how the carburetor operates, fault finding to seek potential attributes that canaffect the stability and fault mode analysis to seek why the attributes affect the stability.Furthermore, all the attributes found has been tested and validated on the engine to seek theircontribution to the stability.The conclusion made of the thesis is that with simple and implementable improvements of thecarburetor the engine stability could be increased with 40 %. A total of five differentattributes were found to affect the stability of the engine. Furthermore, a very detailedexplanation of how the carburetor operates and components inside the carburetor has beenestablished during the thesis.

  • 75.
    Alfredsson, Bo
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Öberg, Martin
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Lai, J.
    Propagation of physically short cracks in a bainitic high strength bearing steel due to fatigue load2016Inngår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 90, s. 166-180Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Physically short cracks in a bainitic high strength bearing steel were fatigue loaded. The rapid propagation rate of early open short cracks agreed with that of long closure free cracks. After some rapid growth, the short cracks entered a transition period to the rate of growth limited long cracks. Potential drop showed that the short cracks were open to the tip throughout the growth sequence, which excluded crack face closure in the wake as the growth limiting mechanism in this material. Instead the short crack effect was related to residual stresses and other mechanisms at the crack tip. Crack manufacturing procedures were determined for straight long and short start cracks in the present material. LEFM with effective material parameters and limit compensation predicted the short crack lives.

  • 76.
    Alfredsson, K. Svante
    et al.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Biel, Anders
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Salimi, Saeed
    Högskolan i Skövde.
    Shear testing of thick adhesive layers using the ENF-specimen2015Inngår i: International Journal of Adhesion and Adhesives, ISSN 0143-7496, E-ISSN 1879-0127, Vol. 62, s. 130-138Artikkel i tidsskrift (Fagfellevurdert)
  • 77.
    Alfredsson, P. Henrik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Tillmark, Nils
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Instability, transition and turbulence in plane Couette flow with system rotation2005Inngår i: IUTAM Symposium on Laminar-Turbulent Transition and Finite Amplitude Solutions / [ed] Mullin, T; Kerswell, R, Springer Netherlands, 2005, Vol. 77, s. 173-193Konferansepaper (Fagfellevurdert)
    Abstract [en]

    System rotation may have either stabilizing or destabilizing effects on shear flows depending on the direction of rotation vector as compared to the vorticity vector of mean flow. This study describes experimental results of laminar, transitional and turbulent plane Couette flow with both stabilizing and destabilizing system rotation. For laminar flow with destabilizing rotation roll cells appear in the flow which may undergo several different types of secondary instabilities, especially interesting is a repeating pattern of wavy structures followed by breakdown, thereafter roll cells reappear in a cyclic pattern. For higher Reynolds number roll cells appear also in a turbulent environment. It is also shown how stabilizing rotation may quench the turbulence completely.

  • 78.
    Alfredsson, P. Henrik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH Mech, Linne FLOW Ctr, SE-10044 Stockholm, Sweden..
    Örlü, Ramis
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Large-Eddy BreakUp Devices - a 40 Years Perspective from a Stockholm Horizon2018Inngår i: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 100, nr 4, s. 877-888Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the beginning of the 1980's Large Eddy BreakUp (LEBU) devices, thin plates or airfoils mounted in the outer part of turbulent boundary layers, were shown to be able to change the turbulent structure and intermittency as well as reduce turbulent skin friction. In some wind-tunnel studies it was also claimed that a net drag reduction was obtained, i.e. the reduction in skin-friction drag was larger than the drag on the devices. However, towing-tank experiments with a flat plate at high Reynolds numbers as well as with an axisymmetric body showed no net reduction, but instead an increase in total drag. Recent large-eddy simulations have explored the effect of LEBUs on the turbulent boundary layer and evaluations of the total drag show similar results as in the towing tank experiments. Despite these negative results in terms of net drag reduction, LEBUs manipulate the boundary layer in an interesting way which explains why they still attract some interest. The reason for the positive results in the wind-tunnel studies as compared to drag measurements are discussed here, although no definite answer for the differences can be given.

  • 79. Alfthan, J.
    et al.
    Gudmundson, Peter
    Östlund, S.
    Micro-mechanical model for mechanosorptive creep2000Konferansepaper (Annet vitenskapelig)
  • 80.
    Alimadadi, Majid
    et al.
    Mid Sweden Univ, Dept Nat Sci NAT, Sundsvall, Sweden..
    Lindström, Stefan B.
    Linköping Univ, Dept Management & Engn, Div Solid Mech, Linkoping, Sweden..
    Kulachenko, Artem
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Role of microstructures in the compression response of three-dimensional foam-formed wood fiber networks2018Inngår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 14, nr 44, s. 8945-8955Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High-porosity, three-dimensional wood fiber networks made by foam forming present experimentally accessible instances of hierarchically structured, athermal fiber networks. We investigate the large deformation compression behavior of these networks using fiber-resolved finite element analyses to elucidate the role of microstructures in the mechanical response to compression. Three-dimensional network structures are acquired using micro-computed tomography and subsequent skeletonization into a Euclidean graph representation. By using a fitting procedure to the geometrical graph data, we are able to identify nine independent statistical parameters needed for the regeneration of artificial networks with the observed statistics. The compression response of these artificially generated networks and the physical network is then investigated using implicit finite element analysis. A direct comparison of the simulation results from the reconstructed and artificial network reveals remarkable differences already in the elastic region. These can neither be fully explained by density scaling, the size effect nor the boundary conditions. The only factor which provides the consistent explanation of the observed difference is the density and fiber orientation nonuniformities; these contribute to strain-localization so that the network becomes more compliant than expected for statistically uniform microstructures. We also demonstrate that the experimentally manifested strain-stiffening of such networks is due to development of new inter-fiber contacts during compression.

  • 81.
    Alizadeh, Amir
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Fracture Simulation of Electrofusion Joining.2015Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This Master thesis investigates mechanical failures of electrofusion joints. This type of joints are used for weld high density polyethylene pipe systems where tting and pipe will be welded together by the heat caused by the resistance of the copper cables to electric current. There have been some failures where a brittle crack has grown through the fusion zone. Polyethylene as a material has a ductile character but brittle behavior occurs due to an unsuccessful welding by a poor fusion interface. In this study, we have chosen to investigate the plausible load cases that can cause the failure and studied the e ect of the geometry of the tting on the fracture toughness of the welded structure. We used the nite element method numerical analysis. We have approached unsuccessful welding (brittle) with a linear model and non-linear (CZM) model and successful welding (ductile) with a non-linear XFEM model. The material parameters needed for these models are gathered by series of experiments. The results shows that the inside pressure is the critical load case. The linear model and CZM model are consistent in terms of predicted responses to the geometrical parameters for the unsuccessful welding. Decreasing the inner cold zone length, increasing the fusion length and the thickness of the tting will improve the fracture toughness of the welded structure.

  • 82. Alkhagen, M.
    et al.
    Toll, Staffan
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    A triaxial rheometer for soft compressible solids2002Inngår i: Journal of Rheology, ISSN 01486055 (ISSN), Vol. 46, nr 1, s. 31-47Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The compression and the shear of soft compressible solids were studied using the triaxial rheometer. The sample was fixed between two parallel plates and the deformation was controlled by an x, y, z displacement on one plate while the stress was measured on the other. The triaxial stress transducer eliminates the edge effects by only measuring the stress on an interior region of the plate. The edge effects and the associated measurement errors were analyzed by the simple isotropic elastic theory and were compared to the measurements done on the chloroprene rubber foam.

  • 83. Alkhagen, M.
    et al.
    Toll, Staffan
    Chalmers University of Technology, Sweden.
    Micromechanics of a compressed fiber mass2007Inngår i: Journal of applied mechanics, ISSN 0021-8936, E-ISSN 1528-9036, Vol. 74, nr 4, s. 723-731Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A theory is presented for the rate modeling of flexible granular solids based on affine average motion of interparticle contacts. We allow contacts to form and break continually but assume the existence of a finite friction coefficient rendering contacts force free as they form or break. The resulting constitutive equations are of the hypoelastic type. A specific model for the deformation of a fiber mass is then developed. The model improves on previous theories for fiber masses in at least two respects: First, it is more general in that it is not restricted to uniaxial compression, although it is restricted to predominantly compressive deformations histories, due to neglect of frictional dissipation. Second, by allowing torsion as well as bending of fibers, this theory covers a larger deformation range. Compression experiments are performed on carded slivers of PA6 fibers under various conditions. The measured response is found to be in close agreement with that predicted by the model.

  • 84. Alkhagen, M.
    et al.
    Toll, Staffan
    Chalmers University of Technology, Sweden.
    The effect of fiber diameter distribution on the elasticity of a fiber mass2009Inngår i: Journal of applied mechanics, ISSN 0021-8936, E-ISSN 1528-9036, Vol. 76, nr 4, artikkel-id 041014Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A random mass of loose fibers interacting by fiber-fiber contact is considered. As proposed in a previous paper, the elastic response is modeled based on the statistical mechanics of bending and torsion of fiber segments between fiber-fiber contact points. Presently we show how the statistical approach can be used to account for a distribution of fiber diameters rather than just a single diameter. The resulting expression has the same form and the same set of parameters as its single-diameter counterpart, except for two dimensionless reduction factors, which depend on the fiber diameter distribution only and reduce to unity for monodisperse fibers. Uniaxial compressibility experiments are performed on several materials with different bimodal fiber diameter distributions and are compared to model predictions. Even though no additional parameters were introduced to model the effect of mixed fiber diameters, the behavior is accurately predicted. Notably, the effect of the nonuniform fiber diameter is strong: A mixture of two fiber diameters differing by a factor of 2 can reduce the response by an order of magnitude, compared to the case of uniform diameter.

  • 85.
    Alm, Christoffer
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Mehari, Amanuel
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Utveckling av hanteringsmaskin för IKEA-påsar2012Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Det här examensarbete handlar om att ta fram en ny maskin, en hanteringsmaskin, till TEXO Application i Älmhult. Syftet med maskinen är att den ska vika IKEAs kundpåsar, hanteringsmaskinen ska användas på samtliga IKEA varuhus världen över. Utvecklingen av hanteringsmaskinen går från enkla skisser av flera koncept till val av koncept och utveckling en denna till en fullständig ritning som det sedan byggs en prototyp utfrån. Effektiviseringen bland samtliga varuhus beräknas att öka då denna lösning ger de anställda mer tid till annat arbete.

  • 86.
    Alm Grundström, Henrik
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Developments in Topology Optimization in the ADDMAN Project2018Rapport (Annet vitenskapelig)
    Abstract [en]

    This document gives an account of some of the work done so far on topology optimization (TO) in the ADDMAN project. As well as the mathematical formulations and implementations details, short discussions are presented on some of the nuances of the different formulations and how they should be used efficiently

  • 87.
    Alm Grundström, Henrik
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära.
    Topology Optimization for Additive Manufacturing Considering Stress and Anisotropy2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Additive manufacturing (AM) is a particularly useful manufacturing method for components designed using topology optimization (TO) since it allows for a greater part complexity than any traditional manufacturing method. However, the AM process potentially leads to anisotropic material properties due to the layer-by-layer buildup of parts and the fast and directional cooling. For Ti6Al4V tensile specimens built using electron beam melting (EBM), it has been observed that flat built specimens show superior strength and elastic moduli compared to top built specimens. Designs with the loading direction parallel to the build layers are therefore expected to show greater reliability.

    In this thesis a procedure is developed to optimize the AM build orientation considering anisotropic elastic material properties. A transversely isotropic material model is used to represent the in-plane and out-of-plane characteristics of AM produced parts. Two additional design variables are added to the TO formulation in order to control the orientation of the material using a coordinate transformation. Sensitivity analysis for the material direction variables is conducted for compliance as well as maximum von-Mises stress using a -norm stress aggregation function.

    The procedures for the AM build orientation optimization and stress constraints are implemented in the finite element software TRINITAS and evaluated using a number of examples in 2D and 3D. It is found that the procedure works well for compliance as well as stress but that a combination of these may lead to convergence issues due to contradicting optimal material orientations. An evaluation of the -norm stress aggregation function showed that a single global stress measure in combination with a stress correction procedure works well for most problems given that the mesh is refined enough to resolve the stresses accurately.  

  • 88.
    Al-Najjar, Basim
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för maskinteknik (MT).
    A method and an apparatus for predicting the condition of amachine or a component of the machine2016Patent (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    The present invention relates to a methodand an apparatus for predicting the condition of a machine or a component of the machine based on measurements of a condition monitoring parameter. The apparatus comprising a data storage for storing a moving window including measurement values of the condition monitoring parameter, a monitoring module configured to determine whena measurement value exceeds a potential failure level at which damage of the machine or component is considered initiated, and to determine the point in time (tP) when the monitoring parameter exceeded the potential failure level, a data cleaning module configured to discarda new measurement value if it is smaller than the latest stored measurement value inthe moving window, to determine an expected value for the measurement based on a defined pattern for the condition monitoring parameter, which pattern reflects an expected behavior of the monitoring parameter after damage has been initiated, and the time elapsed since the point in time the monitoring parameter exceeded the potential failure level, and to discard the new measurement value if it deviates too much from the expected value, and to store not discarded measurement values in the moving window, and a prediction module configured to predict the level of the condition monitoring parameter at a future point in time based on the measurement

  • 89.
    Al-Najjar, Basim
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för maskinteknik (MT).
    A universal coupling for transferring rotary movements between an inputshaft and an output shaft2016Patent (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    The present invention relates to a universal coupling for transferring rotary movements between an input shaft and an output shaft (when the angel between the shafts can be about 90 degree), wherein each of the shafts are arranged to rotate about a longitudinal axis of the shaft, the coupling comprising: an input joint member and output joint member movably coupled to each, and the input joint member  is fixedly connected to the input shaft and the output joint member is fixedly connected to the output shaft.  Each of the input and output joint members comprises at least one annular part having a cross section and defining a central aperture, the annular part of the input joint member passes through the aperture of the annular part of the output joint member, and the annular part of the output joint member passes through the aperture of the annular part of the input joint member, and the area of each the central apertures is larger than the cross section area of each of the annular parts and two spaced apart contact points are formed between the annular parts of the input and output joint members.

  • 90.
    Al-Ramahi, Nawres
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Failure Impact Energy in Curved Composite Plates2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An investigation of low velocity impact characteristics of curved composite plates have been presented. The plates represent parts of car's bumpers with radii of curvature of 120mm,200mm, 300mm, 450mm and infinity.

    Two types of composite materials are used, unidirectional 0° and woven 0°/90° types with five layers of 3mm thickness and ten layers of 6mm thickness of each type.

    The results showed that larger plates curvatures can absorb more impact energy and the ten layer woven 0°/90° composite are superior to similar unidirectional 0° composite. On the other hand the five layer unidirectional 0° plates are superior in absorbing energy compared to similar woven 0°/90° plates.

    An investigation of the failure patterns and development for both types of composite has been presented and discussed.

    The effects of multi-strike on the energy absorbtion of both type of composite have showed different pattern of energy absorbtion behavior.

  • 91.
    Al-Ramahi, Nawres
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Institute of Technology / Baghdad, Middle Technical University, Baghdad, Iraq.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Swerea SICOMP AB, Piteå, Sweden.
    Varna, Janis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Investigation of end and edge effects on results of numerical simulation of single lap adhesive joint with non-linear materials2018Inngår i: International Journal of Adhesion and Adhesives, ISSN 0143-7496, E-ISSN 1879-0127, Vol. 87, s. 191-204Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents systematic numerical study of stresses in the adhesive of a single-lap joint with the objective to improve understanding of the main material and geometrical parameters determining performance of adhesive joints. For this purpose a 3D model as well as 2D model, optimized with respect to the computational efficiency by use of novel displacement coupling conditions able to correctly represent monoclinic materials (off-axis layers of composite laminates), are employed. The model accounts for non-linearity of materials (adherend and adhesive) as well as geometrical non-linearity. The parameters of geometry of the joint are normalized with respect to the dimensions of adhesive (e.g. thickness) thus making analysis of results more general and applicable to wide range of different joints. Optimal geometry of the single-lap joint allowing to separate edge effect from end effects is selected based on results of the parametric analysis by using peel and shear stress distributions in the adhesive layer as a criterion. Three different types of single lap joint with similar and dissimilar (hybrid) materials are considered in this study: a) metal-metal; b) composite-composite; c) composite-metal. In case of composite laminates, four lay-ups are evaluated: uni-directional ([08]T and [908]T) and quasi-isotropic laminates ([0/45/90/-45]S and [90/45/0/-45]S). The influence of the abovementioned parameters on peel and shear stress distributions in the adhesive layer is examined carefully and mechanical parameters governing the stress concentrations in the joint have been identified, this dependence can be described by simple but accurate fitting function. The effect of the used material model (linear vs non-linear) on results is also demonstrated.

  • 92. Alrifaiy, Ahmed
    et al.
    Borg, Johan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Lindahl, Olof
    Ramser, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    A lab-on-a-chip for hypoxic patch clamp measurements combined with optical tweezers and spectroscopy: first investigations of single biological cells2015Inngår i: Biomedical engineering online, ISSN 1475-925X, E-ISSN 1475-925X, Vol. 14, artikkel-id 36Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The response and the reaction of the brain system to hypoxia is a vital research subject that requires special instrumentation. With this research subject in focus, a new multifunctional lab-on-a-chip (LOC) system with control over the oxygen content for studies on biological cells was developed. The chip was designed to incorporate the patch clamp technique, optical tweezers and absorption spectroscopy. The performance of the LOC was tested by a series of experiments. The oxygen content within the channels of the LOC was monitored by an oxygen sensor and verified by simultaneously studying the oxygenation state of chicken red blood cells (RBCs) with absorption spectra. The chicken RBCs were manipulated optically and steered in three dimensions towards a patch-clamp micropipette in a closed microfluidic channel. The oxygen level within the channels could be changed from a normoxic value of 18% O 2 to an anoxic value of 0.0-0.5% O 2. A time series of 3 experiments were performed, showing that the spectral transfer from the oxygenated to the deoxygenated state occurred after about 227 ± 1 s and a fully developed deoxygenated spectrum was observed after 298 ± 1 s, a mean value of 3 experiments. The tightness of the chamber to oxygen diffusion was verified by stopping the flow into the channel system while continuously recording absorption spectra showing an unchanged deoxygenated state during 5400 ± 2 s. A transfer of the oxygenated absorption spectra was achieved after 426 ± 1 s when exposing the cell to normoxic buffer. This showed the long time viability of the investigated cells. Successful patching and sealing were established on a trapped RBC and the whole-cell access (Ra) and membrane (Rm) resistances were measured to be 5.033 ± 0.412 M Ω and 889.7 ± 1.74 M Ω respectively.

  • 93. Alsved, Malin
    et al.
    Wang, Cong
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Civilis, Anette
    Sadrizadeh, Sasan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Ekolind, Peter
    Skredsvik, Henrik
    Höjerback, Peter
    Jakobsson, Jonas
    Löndahl, Jakob
    Experimental and computational evaluation of airborne bacteria in hospital operating rooms with high airflows2018Inngår i: Proceedings of The 5th Working & Indoor Aerosols Conference 18-20 April 2018; Cassino, Italy, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Post-operative infections after surgery can be decreased by the use of efficient ventilation with clean air. In this study, we investigated three types of operating room ventilation: turbulent mixed airflow(TMA), laminar airflow (LAF) and a new type of ventilation named temperature controlled airflow(TcAF). Measurements of airborne bacteria were made during surgery and compared with values calculated by computational fluid dynamics (CFD). The results show that LAF and TcAF are most efficient in removing bacteria around the patient. With LAF, there are large differences in bacterial loads, depending on location in the room.

  • 94. Altimira, M.
    et al.
    Fuchs, Laszlo
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Corrigendum to Numerical investigation of throttle flow under cavitating conditions (International Journal of Multiphase Flow 75 (2015) 124–136) (S0301932215001238) (10.1016/j.ijmultiphaseflow.2015.05.006))2017Inngår i: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 93, s. 216-217Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The authors regret that the figures that were included in the final version of their paper were incorrect. Corrected Figures 3, 4, 5, and 6 are included here. The authors would like to apologise for any inconvenience caused. 

  • 95.
    Alvarez, Victor S
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Neuronik.
    Kleiven, Svein
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Neuronik.
    Effect of pediatric growth on cervical spine kinematics and deformations in automotive crashes2018Inngår i: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 71, s. 76-83, artikkel-id S0021-9290(18)30075-7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Finite element (FE) models are a powerful tool that can be used to understand injury mechanisms and develop better safety systems. This study aims to extend the understanding of pediatric spine biomechanics, where there is a paucity of studies available. A newly developed and continuously scalable FE model was validated and scaled to 1.5-, 3-, 6-, 10-, 14- and 18-year-old using a non-linear scaling technique, accounting for local topological changes. The oldest and youngest ages were also scaled using homogeneous geometric scaling. To study the effect of pediatric spinal growth on head kinematics and intervertebral disc strain, the models were exerted to 3.5 g acceleration pulse at the T1 vertebra to simulate frontal, rear and side impacts. It was shown that the head rotation increases with age, but is over predicted when geometrically scaling down from 18- to 1.5-year-old and under predicted when geometrically scaling up from 1.5- to 18-year-old. The strain in the disc, however, showed a clear decrease with age in side impact and for the upper cervical spine in rear impact, indicating a higher susceptibility for neck injury at younger ages. In the frontal impact, no clear age dependence could be seen, suggesting a large contribution from changed facet joint angles, and lower levels of strain, suggesting a lower risk of injury. The results also highlight the benefit of rearward facing children in a seat limiting head lateral motion.

  • 96. Al-Zubaidy, M. N.
    et al.
    Chan, J. F. L.
    Gibson, A. G.
    Toll, Staffan
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Properties of orthotropic glass-polypropylene composites manufactured by weaving of prepreg tapes and other routes2000Inngår i: Plastics, Rubber and Composites Processing and Applications, ISSN 09598111 (ISSN), Vol. 29, nr 10, s. 520-526Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper reports a study of the melt impregnation and weaving of glass-polypropylene prepreg tapes into sheet for use as a precursor for pressed thermoplastic composite products and a comparison of the properties attainable with those achievable by other comparable routes. Melt impregnation has been used successfully to manufacture well impregnated tapes, with and without internal coupling agent. It appears that weaving could be an economically viable process for converting unidirectional tape into a conformable, press formable prepreg. The properties of glass-polypropylene laminates manufactured by pressing the tape woven product were compared with those of other glass-polypropylene composites, including crossply laminate made from Plytron and samples prepared by film stacking. Quasi-static mechanical properties were found to be comparable with those of Plytron and superior to those of the other materials. In the coupled samples, coupling was somewhat less effective than in Plytron. The impact behaviour of the pressed, tape woven products was impressive and superior to any of the other materials tested. © 2000 IoM Communications Ltd.

  • 97.
    Amberg, Gustav
    KTH.
    Solidification microstructure, dendrites and convection2004Inngår i: Phase Change With Convection: Modelling And Validation / [ed] Kowalewski, TA., Gobin, D., Wien: Springer, 2004, s. 1-53Konferansepaper (Fagfellevurdert)
  • 98.
    Amberg, Gustav
    KTH, Tidigare Institutioner, Mekanik.
    Solidification microstructure, dendrites and convection2004Inngår i: PHASE CHANGE WITH CONVECTION: MODELLING AND VALIDATION / [ed] Kowalewski, TA., Gobin, D., 2004, nr 449, s. 1-53Konferansepaper (Fagfellevurdert)
  • 99. Ambrosi, D.
    et al.
    Ateshian, G. A.
    Arruda, E. M.
    Cowin, S. C.
    Dumais, J.
    Goriely, A.
    Holzapfel, Gerhard A.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Biomekanik.
    Humphrey, J. D.
    Kemkemer, R.
    Kuhl, E.
    Olberding, J. E.
    Taber, L. A.
    Garikipati, K.
    Perspectives on biological growth and remodeling2011Inngår i: Journal of the mechanics and physics of solids, ISSN 0022-5096, E-ISSN 1873-4782, Vol. 59, nr 4, s. 863-883Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    The continuum mechanical treatment of biological growth and remodeling has attracted considerable attention over the past fifteen years. Many aspects of these problems are now well-understood, yet there remain areas in need of significant development from the standpoint of experiments, theory, and computation. In this perspective paper we review the state of the field and highlight open questions, challenges, and avenues for further development.

  • 100.
    Amer, Eynas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Pulsed laser ablation studied using digital holographic interferometry2008Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Pulsed digital holographic interferometry has been used to investigate the plume and the shock wave generated in the ablation process of a Q-switched Nd-YAG (lambda= 1064 nm and pulse duration = 12 ns) laser pulse on a polycrystalline Boron Nitride (PCBN) target under atmospheric air pressure. A special set-up based on using two synchronised wavelengths from the same laser for simultaneous processing and measurement has been used. Digital holograms were recorded for different time delays using collimated laser light (lambda= 532 nm) passed through the volume along the target. Numerical data of the integrated refractive index field were calculated and presented as phase maps showing the propagation of the shock wave and the plume generated by the process. Radon inversion has been used to estimate the 3D refractive index fields measured from the projections assuming rotational symmetry. Verification of the point explosion model has been done. The amount of released energy i.e. the part of the incident energy of the laser pulse that is eventually converted to a shock wave has been estimated. Shock wave front densities have been calculated from the reconstructed refractive index fields using the Gladstone-Dale equation. A comparison of the shock front density calculated from the reconstructed data and that calculated using the point explosion model at different time delays has been done. The comparison shows quite good agreement between the model and the experimental data. Finally the reconstructed refractive index field has been used to estimate the electron number density distribution within the laser induced plasma. The results show that pulsed digital holographic interferometry is a promising technique to study laser ablation processes. Different materials and laser parameters like wavelength, focusing, number of pulses can be studied in combinations with other techniques.

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