uu.seUppsala University Publications
Change search
Refine search result
123 1 - 50 of 132
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Afshar, Reza
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Alavyoon, Navid
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Ahlgren, Anders
    Swedish National Maritime Museums, the Vasa Museum.
    van Dijk, Nico P.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Vorobyev, Alexey
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Gamstedt, Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    A full-scale finite-element model of the Vasa ship2017In: Proceedings of ECCOMAS Thematic Conference CompWood 2017: Computational Methods in Wood Mechanics, 2017Conference paper (Refereed)
    Abstract [en]

    A full-scale model of the 17th century Vasa shipwreck has been developed to assess its current and future structural stability as well as design an improved support structure. A wireframe model, consisting of only lines, points and curves to describe the geometry of the ship, has been provided by the Vasa museum. It has been developed based on geodetic measurements using a total station. From this wireframe model, a three-dimensional (3D) model comprising solid bodies for solid-like parts (i.e. hull and keel), surfaces for the shell-like components (deck planks) and lines for beam-like constituents (deck beams) has been developed in Creo Parametric 3D software. This geometric model has been imported in finite-element software, Ansys, for further development of the stiffeners (knees, riders, stanchions, masts, etc.), adjustment of the correct location of deck beams and, finally, structural analyses of the entire ship (Figure 1). The procedure for selection of the different types of elements in the finite-element (FE) model, the definition of orthotropic material properties for the timber structure and preliminary results are discussed in this paper. Experiences drawn from this engineering project may also be useful in development of finite element models for structural assessment of other complex wooden structures in cultural heritage.

  • 2.
    Aspsjö, Philip
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Industrial Engineering & Management.
    Spännkraft på bandavskrapare: Utredning och konstruktion2013Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis was performed at Vendig AB which is a company that develops and sells products such as belt scrapers for conveyor. The thesis is divided into two parts, one part where it´s investigated which tension force is required to tighten Vendig AB´s scraper Hampus against the belt in a correct way. The second part is called mechanical design and here a new and more compact tension device is developed.

    Field studies has been conducted at a couple of Vendig AB´s costumers to get a knowledge base about how Vendig AB´s products are used, how they function and the environment they operate in. During one of the field studies the force between the scraper and the belt was measured. The result from the measurements, together with a report from LKAB [1], were evaluated and summarized in a table. The required force was recalculated for all different version of the scraper.

    After the tension force had been investigated the old tension device was evaluated and a requirement specification for a new was compiled in collaboration with Vendig AB´s group of technology. A number of concepts where then developed using the concept generator tool SCAMPER. One concept conformed very well to the requirement specification and was further developed. The concept was dimensioned by simulations in CAD, and basic drawings were made. The design solutions where discussed with suppliers and the design was updated. Finally a prototype was ordered to test and evaluate the concept. The tests revealed shortcomings in the prototype which has been evaluated and solutions has been discussed.

  • 3.
    Axelsson Paulsson, Victor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Industrial Engineering & Management.
    Konstruktion av dumpervagn: Från beställning till underlag2015Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis describes the design of a tipping trailer, from a company’s demands andrequests to complete manufacturing documentation. The design is developed for thecompany Abexor AB in Östersund that produces tipping trailers. The product issupposed to be used by Abexors customer to transport cargos of different kinds,such as gravel, stone, dirt, etc.The work commenced with a meeting at the company where demands were set.After that a pre-study was conducted to find out what traffic rules were required forthe trailer to be allowed to be driven on roads. Similar products were examined tosee how the trailer could be designed. The pre-study was followed by an idea andconcept generation. Nine different concepts were generated and the best werechosen for continued work.The concepts that were chosen resulted in a design in CAD were considerationswere taken for dimensions, traffic rules and function. Manufacturing documentationand a list of components to be bought were generated.In the section discussion and conclusions you can see what the thesis has resulted in.It’s also described what could have been done different and guidelines for futuredevelopment have been made.

  • 4.
    Batchuluun, Bolormaa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Industrial Engineering & Management.
    Development of New Lifting Equipment for VPA Plates2016Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis explores how to develop new lifting equipment for the membrane and filter plates of the VPA (Metso) machine satisfying all the safety requirements. The VPA is a heavy duty machine with a number of plates, developed for filtration of minerals. The plates must be replaced or removed immediately once the wear has reached a given value or an error has been detected.

    The new lifting system differs to a great extent from conventional system in which a fiber strap was used; the designed lifting equipment comprises of a variety of parts resulting in a higher capacity to be used ín different situations safer and satisfies the vital requirements such as being a secure and cost-effective method, issued by the customers.

    Several solution proposals have been developed to offer better proposals before the final candidate has been selected and theoretically motivated with FEM analysis as well as analytical calculations.

    Keywords - VPA, membrane and filter plate, lifting equipment, pivot supporter hinge, safety, cost effective

  • 5.
    Bergkvist, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Industrial Engineering & Management.
    Ljunggren, Terje
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Industrial Engineering & Management.
    Design och optimering av lagertätning: Hos hydrodynamiska oljeglidlager med labyrinttätning2014Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    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.

  • 6.
    Bjurhager, Ingela
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Gamstedt, E. KristoferUppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Predicting creep rate in archeological wood from theVasa ship – a first appraoch2012Conference proceedings (editor) (Refereed)
  • 7.
    Bjurhager, Ingela
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Gamstedt, Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Keunecke, Daniel
    Niemz, Peter
    Berglund, Lars A.
    Mechanical performance of yew (Taxus baccata L.) from a longbow perspective2013In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 67, no 7, p. 763-770Article in journal (Refereed)
    Abstract [en]

    Yew (Taxus baccata L.) longbow was the preferred weapon in the Middle Ages until the emergence of guns. In this study, the tensile, compression, and bending properties of yew were investigated. The advantage of yew over the other species in the study was also confirmed by a simple beam model. The superior toughness of yew has the effect that a yew longbow has a higher range compared with bows made from other species. Unexpectedly, the mechanical performance of a bow made from yew is influenced by the juvenile-to-mature wood ratio rather than by the heartwood-to-sapwood ratio. A yew bow is predicted to have maximized performance at a juvenile wood content of 30-50%, and located at the concave side (the compressive side facing the bowyer). Here, the stiffness and yield stress in compression should be as high as possible.

  • 8.
    Bjurhager, Ingela
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Vorobyev, AlexeyUppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.van Dijk, NicoUppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.Gamstedt, E. KristoferUppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.Ahlgren, AndersOlofsson, Magnus
    Investigation of time-dependent deformation of wood from the warship Vasa2013Conference proceedings (editor) (Refereed)
  • 9.
    Carlsson, Jenny
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Dynamic crack growth in porous materials2017Conference paper (Other academic)
  • 10.
    Carlsson, Jenny
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Snabba brott i trä2018Conference paper (Other (popular science, discussion, etc.))
  • 11.
    Carlsson, Jenny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Isaksson, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Crack dynamics and crack tip shielding in a material containing pores analysed by a phase field method2019In: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 206, p. 526-540Article in journal (Refereed)
    Abstract [en]

    Many naturally occurring materials, such as wood and bone, have intricate porous micro-structures and high stiffness and toughness to density ratios. Here, the influence of pores in a material on crack dynamics in brittle fracture is investigated. A dynamic phase field finite element model is used to study the effects of pores with respect to crack path, crack propagation velocity and energy release rate in a strip specimen geometry with circular pores. Four different ordered pore distributions are considered, as well as randomly distributed pores. The results show that the crack is attracted by the pores; this attraction is stronger when there is more energy available for crack growth. Crack propagation through pores also enables higher crack propagation velocities than are normally seen in strip specimens without pores (i.e. homogeneous material), without a corresponding increase in energy release rate. It is further noticed that as the porosity of an initially solid material increases, the crack tip is increasingly likely to become shielded or arrested, which may be a key to the high relative strength often exhibited by naturally occurring porous materials. We also find that when a pore is of the same size as the characteristic internal length then the pore does not localise damage. Since the characteristic internal length only regularises the damage field and not the strain end kinetic energy distributions, crack dynamics are still affected by small pores.

  • 12.
    Carlsson, Jenny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Isaksson, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Dynamic crack propagation and crack tip shielding in porous materials analyzed by the phase field method for fracture2018Conference paper (Other academic)
  • 13.
    Carlsson, Jenny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Isaksson, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Dynamic crack propagation in wood fibre composites analysed by high speed photography and a dynamic phase field model2018In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 144-145, p. 78-85Article in journal (Refereed)
    Abstract [en]

    Using an experimental setup, with a high-speed camera to track crack tip velocity, dynamic fracture is studied in wood fibre polylactic acid (PLA) composite and pure PLA. The experiments are analysed quantitatively in terms of the relation between energy release rate and crack tip velocity, and qualitatively in terms of branching occurrence and fracture surface appearance. Branching occurs frequently in PLA specimens but not in wood fibre composite specimens, in spite of high energy release rates. Scanning electron microscopy images of the fracture surfaces show that the fracture surfaces in wood fibre composite materials are rugged and uneven compared to PLA, whose surfaces are smoother. The experimental results are compared to numerical results, obtained using a dynamic phase field finite element model. Simulations correlate well with experiments with respect to the relation between energy release rate and crack tip velocity. For PLA, the simulations also predict branching correctly, but for wood fibre composites, the simulations slightly over-predict the amount of branching and point to a need for further development of fracture models in order to better capture the constitutive behaviour of these heterogeneous materials.

  • 14.
    Carlsson, Jenny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Isaksson, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Fracture nucleation and continued crack growth on the cell scale in wood analysed by as high-resolution finite element model2016In: The Eccomas Congress 2016 Proceedings, 2016Conference paper (Refereed)
  • 15.
    Carlsson, Jenny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Isaksson, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    High-velocity crack speed in wood fibre composites: an experimental and numerical study2017In: CFRAC 2017, International Conference on Computational Fracture and Failure of Materials and Structures, Book of abstracts, 2017, p. 155-Conference paper (Refereed)
  • 16.
    Carlsson, Jenny
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Joffre, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Isaksson, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Dynamic crack propagation in wood fibre composites2017In: Svenska Mekanikdagar 2017, Uppsala 12 – 13 juni, 2017Conference paper (Refereed)
  • 17.
    Carlsson, Markus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Industrial Engineering & Management.
    Konstruktion av beslag med dörrfunktion till spridarlucka2013Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis was performed at Zetterbergs Industri AB. Zetterbergs is designing, building and mounts body systems for trucks, including dumpers and tippers. The assignment for the thesis was to design a door hinge for a spreader gate. The spreader gate is the top of the two tailgates on a dumper or tipper and opens back and outwards when tipping the cargo. The spreader gate controls the mass flow of the material being tipped. Zetterbergs want to offer their customers an opportunity to also open the spreader gate as a door and place it along the outside of the tipper to get easier access to the platform when loading equipment. They already have an existing solution for both the tipper and the dumper, but there is a need to improve and coordinate these solutions. The existing solution is not entirely rigid which causes problems of sagging when used, and a result of this is heavy lifting for the operator.

     

    The process with designing a new hinge began with an initial study where, among others, the existing hinge and prototype solutions of the hinge at Zetterbergs were examined. To get to understand the process and which parts that needed to be taken into consideration when designing, a participation in the production was made. The initial study was finalized with the preparation of a user and technical specification.

     

    Following the initial study several concepts was generated with a method called “ the five step method”.  Afterwards the concepts were evaluated and compared which lead to the selection of one of the concepts for a final design.

     

    The result of this thesis is a door hinge with tree different configurations. Those three configurations were made to fit the combinations between tipper and dumper as well as aluminum and steel hatch. The hinges are similar to each other and only a few details separate them. All components in the door hinge are adjusted for the production at Zetterbergs. The door hinge is designed in a way that prevents the operator from using it improperly.

  • 18.
    Chen, Shaohui
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Isaksson, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    A note on the defect sensitivity of brittle solid foams2019In: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 206, p. 541-550Article in journal (Refereed)
    Abstract [en]

    The fracture behavior of brittle solid foams of different densities and regularities is numerically analyzed in finite element models. The findings provide insight into the complex fracture phenomenon in cellular materials and reveal a size influence from a dominant microstructure on the global fracture mechanism. It is observed that a crack of length of about three times the average cell size in the foam is needed to obtain localization of nucleated fractures to the vicinity of the initial defect At cracks smaller than this critical size, the fractures nucleate at randomly positioned high-stressed regions in the foam far away from the initial crack, i.e. the structure is seemingly insensitive to the initial defect Further, it is found that irregular (i.e. randomly positioned cells) foams are more insensitive to defects than perfectly ordered foams if all other parameters are similar and thus indicate that classical fracture theories for solid foams have to be slightly modified.

  • 19. Collet, Pierre
    et al.
    Gary, Gérard
    Lundberg, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Noise-corrected Estimation of Complex Modulus in Accord With Causality and Thermodynamics: Application to an Impact test2013In: Journal of applied mechanics, ISSN 0021-8936, E-ISSN 1528-9036, Vol. 80, no 1, p. 011018-Article in journal (Refereed)
    Abstract [en]

    Methods for estimation of the complex modulus generally produce data from which discrete results can be obtained for a set of frequencies. As these results are normally afflicted by noise, they are not necessarily consistent with the principle of causality and requirements of thermodynamics. A method is established for noise-corrected estimation of the complex modulus, subject to the constraints of causality, positivity of dissipation rate and reality of relaxation function, given a finite set of angular frequencies and corresponding complex moduli obtained experimentally. Noise reduction is achieved by requiring that two self-adjoint matrices formed from the experimental data should be positive semidefinite. The method provides a rheological model that corresponds to a specific configuration of springs and dashpots. The poles of the complex modulus on the positive imaginary frequency axis are determined by a subset of parameters obtained as the common positive zeros of certain rational functions, while the remaining parameters are obtained from a least squares fit. If the set of experimental data is sufficiently large, the level of refinement of the rheological model is in accordance with the material behavior and the quality of the experimental data. The method was applied to an impact test with a Nylon bar specimen. In this case, data at the 29 lowest resonance frequencies resulted in a rheological model with 14 parameters. The method has added improvements to the identification of rheological models as follows: (1) Noise reduction is fully integrated. (2) A rheological model is provided with a number of elements in accordance with the complexity of the material behavior and the quality of the experimental data. (3) Parameters determining poles of the complex modulus are obtained without use of a least squares fit.

  • 20.
    Edqvist, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hedlund, Emma
    Lundberg, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Quasi-static and dynamic electromechanical response of piezoelectric multilayer cantilever beams2010In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 157, no 2, p. 198-209Article in journal (Refereed)
    Abstract [en]

    Piezoelectric multilayer cantilever beams were considered with the aim to establish a simple but general theoretical model, fabricate such beams by a procedure suitable for devices on millimetre scale such as actuators, and study their quasi-static and dynamic electro-mechanical responses. In addition to Euler-Bernoulli assumptions, the beams were assumed to be lossless and have linear piezoelectric response. Four types of beams of nominal length 10 mm, width 2 mm and thickness either 55 or 86 µm, and with two asymmetric configurations of 14 or 15 layers, were fabricated. From top to bottom, each beam consisted of six aluminium electrode layers alternating with five active P(VDF-TrFE) layers, of one passive such layer, and of one polyimide and one copper layer, or vice versa. The thicknesses of the layers and of the beam were determined by use of focused ion beam, scanning electron microscope, light microscope, and Heidenhain probe. Both theoretical and experimental results for resonance frequencies and transverse tip displacement per unit driving voltage showed fair overall agreement from quasi-static conditions to frequencies above the second resonance frequency. Deviations observed are mainly due to variations resulting from the manufacturing process, to nonlinear piezoelectricity and to the presence of losses.

  • 21.
    Espadas Escalante, Juan José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics. Uppsala University.
    On numerical analyses of woven composite laminates: Homogenization, damage and fracture2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This dissertation analyzes various mechanical properties of textile reinforced composite laminates.

    The dissertation is based on a total of six published works, which are essentially numerical, although experimental elements are available. The numerical methods used are based on high-resolution finite element models in combination with sophisticated phase-field theories for brittle fracture. A key result is that important mechanical properties in engineering applications, such as fracture or damage resistance, can be substantially affected by the arrangement of the constituent materials at the meso level.

    List of papers
    1. A phase-field model for strength and fracture analyses of fiber-reinforced composites
    Open this publication in new window or tab >>A phase-field model for strength and fracture analyses of fiber-reinforced composites
    2019 (English)In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 174, p. 58-67Article in journal (Refereed) Published
    Abstract [en]

    A phase-field model for brittle fracture is proposed and evaluated for strength and fracture analyses of composites. In addition to the elastic properties, this approach makes use of only the fracture toughness and the strength of the material. The capability of the method is shown in analyses of composites at two scales. In laminates, strengths of notched laminates are estimated, including hole size effects. In a lamina, cracks developed in both transverse tension and compression are analyzed and compared to other numerical methods in the literature. The effects of a spectral and a hydrostatic-deviatoric decomposition of the strain energy density, two variants often used in phase-field formulations, are studied. It is shown that the choice of the decomposition affects the fracture development. Results are compared to experiments and simulations in the literature showing the capabilities of the phase-field approach.

    Place, publisher, year, edition, pages
    Elsevier, 2019
    Keywords
    Computational mechanics, Strength, Fracture, Finite element analysis (FEA)
    National Category
    Composite Science and Engineering
    Identifiers
    urn:nbn:se:uu:diva-368254 (URN)10.1016/j.compscitech.2018.10.031 (DOI)000469407500008 ()
    Available from: 2018-12-03 Created: 2018-12-03 Last updated: 2019-07-05Bibliographically approved
    2. A study on the influence of boundary conditions in computational homogenization of periodic structures with application to woven composites
    Open this publication in new window or tab >>A study on the influence of boundary conditions in computational homogenization of periodic structures with application to woven composites
    2017 (English)In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 160, p. 529-537Article in journal (Refereed) Published
    Abstract [en]

    The influence of boundary conditions (BCs) in the estimation of elastic properties of periodic structures is investigated using computational homogenization with special focus on planar structures. Uniform displacement, uniform traction, periodic, in-plane periodic and a proposed mix of periodic and traction BCs are used. First, the effect of the BCs is demonstrated in structures with one-, two- and three-dimensional periodicity. Mixed BCs are shown to most accurately represent the behavior of layered structures with a small number of repeating unit cells. Then, BCs are imposed on a twill woven composite architecture. Special attention is devoted to investigate the sensitivity of the estimated properties with respect to the BCs and to show differences when considering a single lamina or a laminate. High sensitivity of the in-plane extensional modulus and Poisson's ratio with respect to the type of BCs is found. Moreover, it is shown that the mix of BCs and in-plane periodic BCs are capable to represent an experimental strain field.

    Keywords
    Computational homogenization, Mixed boundary conditions, Heterogeneous structures, Elastic properties, Woven composites, Finite element method
    National Category
    Composite Science and Engineering
    Identifiers
    urn:nbn:se:uu:diva-359307 (URN)10.1016/j.compstruct.2016.10.082 (DOI)000390470300044 ()
    Available from: 2018-08-31 Created: 2018-08-31 Last updated: 2019-07-05Bibliographically approved
    3. The effect of free-edges and layer shifting on intralaminar and interlaminar stresses in woven composites
    Open this publication in new window or tab >>The effect of free-edges and layer shifting on intralaminar and interlaminar stresses in woven composites
    2018 (English)In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 185, p. 212-220Article in journal (Refereed) Published
    Abstract [en]

    The free-edge effects and relative layer shifting in the interlaminar and intralaminar stresses of plain woven composite laminates under uniaxial extension is investigated numerically using a finite element approach. A computational framework of the free-edge problem for periodic structures with finite width is applied to woven laminates. First, two-layered laminates with three different shifting configurations are studied considering repeating unit cells simulating finite and infinite width. For each configuration, two different widths are considered by trimming the model at different locations in order to investigate different free-edge effects. Then, two four-layered laminates with no shifting and a maximum shifting configuration are analyzed to illustrate the effect of neighboring layers in the stresses. For each shifting configuration, different delamination mechanisms are expected. When considering more layers, it is found that the stacking configuration affects the state of stress and the free-edge effects depending on the shifting. In general, a different behavior than that of unidirectional tape laminates is found, since the interlaminar and intralaminar stresses can be higher than those generated at the free-edges. Particularly, for the maximum shifting configuration results are in agreement with experimental results in the literature where no debonding between yarns was observed at the free-edges.

    Keywords
    Woven composites, Finite element method, Intralaminar stresses, Interlaminar stresses, Free-edge effects, Multiscale modeling
    National Category
    Applied Mechanics
    Identifiers
    urn:nbn:se:uu:diva-341485 (URN)10.1016/j.compstruct.2017.11.014 (DOI)000418961000018 ()
    Available from: 2018-02-28 Created: 2018-02-28 Last updated: 2019-07-05Bibliographically approved
    4. A study of induced delamination and failure in woven composite laminates subject to short-beam shear testing
    Open this publication in new window or tab >>A study of induced delamination and failure in woven composite laminates subject to short-beam shear testing
    2019 (English)In: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 205, p. 359-369Article in journal (Refereed) Published
    Abstract [en]

    Failure in woven composite laminates subject to global shear load is studied. Laminates are manufactured, tested and analyzed using X-ray computed tomography, scanning electron microscopy and finite element models. It is found that the stress distribution along the thickness direction is dependent on the layer shifting that alters different yarn interactions, which in turn, affects delamination and failure onset A suggested failure mechanism is in agreement with experimental observations.

    National Category
    Applied Mechanics
    Identifiers
    urn:nbn:se:uu:diva-368250 (URN)10.1016/j.engfracmech.2018.10.015 (DOI)000453766000026 ()
    Available from: 2018-12-03 Created: 2018-12-03 Last updated: 2019-07-05Bibliographically approved
    5. Analysis of the Influence of Layer Shifting on the Elastic Response and Damage Nucleation and Growth in Woven Composite Laminates
    Open this publication in new window or tab >>Analysis of the Influence of Layer Shifting on the Elastic Response and Damage Nucleation and Growth in Woven Composite Laminates
    2018 (English)In: NASA Technical MemorandumsArticle in journal (Refereed) Published
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-368253 (URN)
    Available from: 2018-12-03 Created: 2018-12-03 Last updated: 2019-07-05
    6. Mesoscale analysis of the transverse cracking kinetics in woven composite laminates using a phase-field fracture theory
    Open this publication in new window or tab >>Mesoscale analysis of the transverse cracking kinetics in woven composite laminates using a phase-field fracture theory
    2019 (English)In: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 216, article id 106523Article in journal (Refereed) Published
    Abstract [en]

    A phase-field approach to fracture is used to simulate transverse cracking kinetics in composite laminates. First, a typical unidirectional tape laminate is modeled and the transverse cracking evolution with the consequent reduction in the in-plane modulus of elasticity is estimated. Then, a four-layered plain weave composite is modeled using different layer shifting configurations. Predictions in the transverse cracking evolution become improved as the shifting configuration of the laminate model become closer to experimental observations. Simulations predict that some cracks do not form perpendicularly to the loading direction, as it has been observed experimentally in similar locations. Only the fracture toughness and the in situ transverse strength of the ply are required without prior knowledge of the position of the cracks or an ad hoc criterion for crack evolution. All the simulations are compared qualitatively and quantitatively to experiments published elsewhere.

    Keywords
    Composites, Fibre reinforced materials, Fracture mechanics, Damage mechanics, Crack growth
    National Category
    Applied Mechanics
    Research subject
    Engineering science with specialization in Applied Mechanics
    Identifiers
    urn:nbn:se:uu:diva-388533 (URN)10.1016/j.engfracmech.2019.106523 (DOI)000477573000028 ()
    Available from: 2019-07-01 Created: 2019-07-01 Last updated: 2019-09-20Bibliographically approved
  • 22.
    Espadas-Escalante, Juan José
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Isaksson, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    A study of induced delamination and failure in woven composite laminates subject to short-beam shear testing2019In: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 205, p. 359-369Article in journal (Refereed)
    Abstract [en]

    Failure in woven composite laminates subject to global shear load is studied. Laminates are manufactured, tested and analyzed using X-ray computed tomography, scanning electron microscopy and finite element models. It is found that the stress distribution along the thickness direction is dependent on the layer shifting that alters different yarn interactions, which in turn, affects delamination and failure onset A suggested failure mechanism is in agreement with experimental observations.

  • 23.
    Espadas-Escalante, Juan José
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Isaksson, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Mesoscale analysis of the transverse cracking kinetics in woven composite laminates using a phase-field fracture theory2019In: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 216, article id 106523Article in journal (Refereed)
    Abstract [en]

    A phase-field approach to fracture is used to simulate transverse cracking kinetics in composite laminates. First, a typical unidirectional tape laminate is modeled and the transverse cracking evolution with the consequent reduction in the in-plane modulus of elasticity is estimated. Then, a four-layered plain weave composite is modeled using different layer shifting configurations. Predictions in the transverse cracking evolution become improved as the shifting configuration of the laminate model become closer to experimental observations. Simulations predict that some cracks do not form perpendicularly to the loading direction, as it has been observed experimentally in similar locations. Only the fracture toughness and the in situ transverse strength of the ply are required without prior knowledge of the position of the cracks or an ad hoc criterion for crack evolution. All the simulations are compared qualitatively and quantitatively to experiments published elsewhere.

  • 24.
    Espadas-Escalante, Juan José
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    van Dijk, Nico P.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics, Byggteknik.
    Isaksson, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    The effect of free-edges and layer shifting on intralaminar and interlaminar stresses in woven composites2018In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 185, p. 212-220Article in journal (Refereed)
    Abstract [en]

    The free-edge effects and relative layer shifting in the interlaminar and intralaminar stresses of plain woven composite laminates under uniaxial extension is investigated numerically using a finite element approach. A computational framework of the free-edge problem for periodic structures with finite width is applied to woven laminates. First, two-layered laminates with three different shifting configurations are studied considering repeating unit cells simulating finite and infinite width. For each configuration, two different widths are considered by trimming the model at different locations in order to investigate different free-edge effects. Then, two four-layered laminates with no shifting and a maximum shifting configuration are analyzed to illustrate the effect of neighboring layers in the stresses. For each shifting configuration, different delamination mechanisms are expected. When considering more layers, it is found that the stacking configuration affects the state of stress and the free-edge effects depending on the shifting. In general, a different behavior than that of unidirectional tape laminates is found, since the interlaminar and intralaminar stresses can be higher than those generated at the free-edges. Particularly, for the maximum shifting configuration results are in agreement with experimental results in the literature where no debonding between yarns was observed at the free-edges.

  • 25.
    Fjelstad, Emanuel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Industrial Engineering & Management.
    El Harbiti, Mohammed
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Industrial Engineering & Management.
    Design och konstruktionsförbättringar: En omkonstruktion av mockningsredskapet SverigeGrepen2013Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis will describe the redesign of the manure fork SverigeGrepen. The product

    is available for purchase in Scandinavia and and parts of the rest of Europe.

    The product is available in stores but the companys goal is to start distribute it over

    the internet. A problem today with a purchase over the internet is that the costumer

    has to pay a high shipping-fee due to the products unique form. The long handle

    contributes to the high shipping-fee which makes it hard to attract costumers to

    purchase the product online. Deficiencies have been found at the manure forks basket

    and needs to be examined. These problems need to be checked out so that

    SverigeGrepen can become an even more compatitive product.

    To obtain a solid theoretical ground a literature was made about the concerned

    subjects.

    The project proceeded with the gathering of information about the product, by

    communications with the contact at the company and usage of the manure fork in it´s

    real enviroment to locate complications with the design. Some temporary souloutions

    have been tested but would in the long run be in need of new souloutions.

    Based on similar products and the existing soloutions some new consepts were

    introduced. The best concepts were mdeled in CAD and modified by some input

    from the company and a plastic worker. Images of the CAD model and a real life-size

    prototype printed in a 3D-printer were used as support during the discussions.

    The outcome of the project is that design documents of an easy to use souloution to

    assemble/dissmantle the manure forks shafthalves whitch minimizes the packaging

    volume and thereby reduces the shipping costs, were made. Designpropositions were

    produced to eliminate deficiencies located at parts of the basket in the beginning of

    the project.

  • 26.
    Gamstedt, E. Kristofer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Afshar, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Ahlgren, Anders
    Swedish National Maritime Museums, the Vasa Museum, Stockholm, Sweden.
    Preserving the Vasa ship: Research and development of a new support structure2018Conference paper (Other academic)
  • 27.
    Gamstedt, E. Kristofer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Afshar, RezaUppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.van Dijk, Nico P.Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.Vorobyev, AlexeyUppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Development of a support structure for the wooden shipwreck Vasa2017Conference proceedings (editor) (Refereed)
  • 28.
    Gamstedt, E. Kristofer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Bader, T.K.Borst, K.
    Mixed numerical-experimental methods in woodmicromechanics2012Conference proceedings (editor) (Refereed)
  • 29.
    Gamstedt, E. Kristofer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Joffre, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Berthold, F.
    Monitoring of fibre length degradation during processing of short-fibre composites by use of X-ray computed tomography2013In: Proceedings of the 34th Risø International Symposium on Materials Science: Processing of fibre composites - Challenges for maximum materials performanc, Roskilde, Denmark: Technical University of Denmark , 2013Conference paper (Refereed)
  • 30.
    Gamstedt, E. Kristofer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Sandell, Robert
    Berthold, Fredrik
    Pettersson, Torbjörn
    Characterization of interfacial stress transfer ability of particulate cellulose composite materials2011In: Mechanics of materials (Print), ISSN 0167-6636, E-ISSN 1872-7743, Vol. 43, no 11, p. 693-704Article in journal (Refereed)
    Abstract [en]

    Composites with cellulose reinforcements are steadily gaining increased use. The stress transfer ability between reinforcement and polymer matrix has a strong influence on mechanical properties like strength and fracture toughness. This work presents a method to assess the stress transfer ability between cellulose and polymer matrix from a model material with cellulose spheres embedded in a polymer matrix. Such a material show smaller variability compared with composites based on natural cellulose fibres, and is less cumbersome than single fibre tests with regard to interfacial characterization. Measured elastic moduli of particulate composites is compared with predicted values from a micromechanical model based on a composite sphere assembly in a self-consistent scheme with only a spring constant of an imperfect interface as fitting parameter expressed in Pa/m. This interface parameter is identified through inverse modelling and used to quantify stress-transfer ability of cellulose/polylactide and cellulose/polystyrene composite interfaces. A higher degree of interfacial interaction was found for the former. This ranking was corroborated by adhesive force measurements using a micrometre sized cellulose sphere attached to the end of a cantilever in an atomic force microscope. With the model microstructure of a cellulose-sphere composite, an interfacial efficiency parameter can be backed out from stiffness measurements to be used in e.g. ranking of different fibre surface treatments and choice of matrix in the development of stronger natural-fibre composites.

  • 31.
    Gamstedt, E. Kristofer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Ståhlberg, MartinBjurhager, IngelaAhlgren, AndersOlofsson, Magnus
    From creep characterization of Vasa oak towards design strategies of an improved support structure for the ship2011Conference proceedings (editor) (Refereed)
  • 32.
    Gamstedt, E. Kristofer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Sun, Fengzhen
    Department of Mechanical Engineering, Imperial College London, UK.
    Polymer physics in nanoscale cutting: Opportunities for improved control in nano-manufacturing?2018Conference paper (Refereed)
    Abstract [en]

    Nano-scale manufacturing imposes demands on prediction of cutting processes on small scales. Specifically for applications that include optical functions, means to control the process parameter to produce high quality and damage-free surfaces are of importance. Control through empirical testing may be time-consuming and costly. Predictive modelling schemes based on the underlying physical mechanisms could potentially be more generally applicable in manufacturing. The understanding of polymer physics and mechanics on sub-micrometre scale is emerging, and slowly but increasingly transferred from a fundamental research field to useful engineering applications. Nanoscale cutting of metals has been studied more and is better understood than that of polymers. For polymers, there are generally more complex interactions between deformation rates, temperature change and material transitions. These effects need to be included in physical models describing the cutting processes in polymers. Furthermore, the mechanical behaviour of polymers may be quite different on the nanoscale compared with macroscale. The material properties are frequently known to be size-dependent. This calls for development of experimental methods to characterize the material properties on the nanoscale, to be used in predictive modelling.

    In this work, we have used an ultramicrotome, normally intended for preparation of ultrathin samples for transmission electron microscopy, instrumented with piezoelectric transducers to measure the cutting forces on sections down to about 50 nm thickness of thermoplastic PMMA. With this equipment, it was possible to investigate the effects of cutting speed and cutting thickness on the formation of surface damage in a well-controlled and reproducible manner. Using atomic force microscopy, the surface damage was identified as shear yield bands triggered by adiabatic heating. A suitable physical model including these observed phenomena made it possible to link the processing conditions with the onset of damage formation, i.e. the transition between a high-quality transparent surface and a damaged uneven surface. A finite element model was developed to predict the formation of the undesired shear bands. From an engineering perspective, such an approach could be potentially useful in improved manufacturing control. The present example supports the idea that material mechanics can be integrated in nanoscale manufacturing. In the future, it is not unlikely that instrumented nanomachining will provide on-line feedback through physical predictive models to adjust the processing parameters (forces, speed, etc.) to maintain a sufficiently high product quality at the highest production rate.

  • 33. Girlanda, O
    et al.
    Sahlen, F
    Joffre, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Gamstedt, Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Schmidt, L
    Forsberg, F
    Sjödahl, M
    Analysis of the micromechanical deformation in pressboard performed by X-ray microtomography2015In: 2015 IEEE Electrical Insulation Conference (EIC), 2015, p. 89-92Conference paper (Refereed)
    Abstract [en]

    A large number of electrical insulation components are produced in paper-based materials. Paper combines good insulating properties with the necessary mechanical and chemical stability. Paper consists of a system of fibers binding to each other creating a strong network. The presence of large open pores allows for impregnability of the material but also causes mechanical weakness in particular in the out-of-plane direction of the material. This aspect is important for pressboard components, where the resistance to compression stress is relevant for e.g. transformer windings. It is therefore relevant to understand the mechanisms that underlay the out-of-plane deformation of pressboard. In order to get a clear picture of the deformation patterns within the material, X-ray micro-computed tomography was used. Pressboard test pieces were subjected to in-situ out-of-plane compressive loading. 3D images of the sample could be captured before, during and after the loading sequence. Image analysis allowed for the definition of strain fields. The results revealed a strong correlation between the density variation within the sample and the strain calculated from the 3D images.

  • 34.
    Gustavsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Diverse mechanisms of friction induced self-organisation into a low-friction material - An overview of WS2 tribofilm formation2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 101, p. 340-347Article in journal (Refereed)
    Abstract [en]

    A clever way to accomplish low friction in sliding contacts is to use materials that combine high hardness with low shear strength. Such seemingly paradoxical combination of high resistance and low resistance to plastic deformation can only be realized by combining a hard substrate material with a thin easy-shear coating. Some prominent such coating candidates are sulfides and selenides of mainly molybdenum and tungsten. This paper focuses on tungsten disulfide, WS2, and explores the many routes to formation and regeneration of such low-friction tribofilms. The initial surfaes involve various types of coatings, materials and fluids, including W and S in different states, but none of which include crystalline WS2. All formation routes result in remarkably similar, pure crystalline WS2 tribofilms.

  • 35.
    Göteman, Malin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Engström, Jens
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Eriksson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Isberg, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Methods of reducing power fluctuations in wave energy parks2014In: Journal of Renewable and Sustainable Energy, ISSN 1941-7012, E-ISSN 1941-7012, Vol. 6, p. 043103-Article in journal (Refereed)
    Abstract [en]

    One of the major challenges in constructing effective and economically viable wave energy parks is to reduce the large fluctuations in power output. In this paper, we study different methods of reducing the fluctuations and improve the output power quality. The parameters studied include the number of devices, the separating distance between units, the global and local geometries of the array, sea state and incoming wave direction, and the impact of including buoys of different radii in an array. Our results show that, e. g., the fluctuations as well as power per device decrease strictly with the number of interacting units, when the separating distance is kept constant. However, including more devices in a park with fixed area will not necessarily result in lowered power fluctuations. We also show that varying the distance between units affects the power fluctuations to a much larger extent than it affects the magnitude of the absorbed power. The fluctuations are slightly lower in more realistic, randomized geometries where the buoys tend to drift slightly off their mean positions, and significantly lower in semi-circular geometries as opposed to rectangular geometries. 

  • 36.
    Hassel, Beatriz Ivón
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Trey, Stacy
    KTH.
    Leijonmarck, Simon
    KTH.
    Johansson, Mats
    KTH.
    A Study on the Morphology, Mechanical, and Electrical Performance of Polyaniline-modified Wood: A Semiconducting Composite Material2014In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, no 3, p. 5007-5023Article in journal (Refereed)
    Abstract [en]

    This study investigated the morphology, electrochemical modification with respect to the wood fiber direction, and mechanical properties of wood modified by in situ polymerization with polyaniline (PANI). This polymerization formed a composite material with applications as an anti-static, electromagnetic, anti-corrosion, and heavy metal purifying materials. The polymer was found throughout the entire structure of the wood and was quantified within the wood cell wall and middle lamella by SEM-EDX. The presence of PANI affected the conductivity of the composite specimens, which was found to be higher in the fiber direction, indicating a more intact percolation pathway of connected PANI particles in this direction. The PANI modification resulted in a small reduction of the storage modulus, the maximum strength, and the ductility of the wood, with decreases in the properties of specimens conditioned in an environment above 66% relative humidity. The in situ-polymerized PANI strongly interacted with the lignin component of the veneers, according to the decrease in the lignin glass transition temperature (Tg) noted in DMA studies.

  • 37.
    Hassel, Ivon
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Afshar, R
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Vorobyev, A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Bommier, F
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Gamstedt, K
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Towards determination of local and overall displacements of the Vasa ship structure: Effect of its mechanical connections2014Conference paper (Refereed)
    Abstract [en]

    The warship Vasa from the 17th century must be preserved for the future generations. There are many concerns currently being addressed by ongoing research efforts. The support structure is one of them, which needs to be re-designed. In order to do this, the local and overall deformation of the Ship’s structure must be identified. The earlier impregnation of PEG on the Vasa material is causing the material to creep significantly more than oak without PEG, resulting in an increasing deformation of the ship. In addition to this, the effect of the mechanical connections of the ship needs to be considered. Experimental tests were performed on a 1:1 scale replica of a representative section of the Vasa ship. Different load cases were applied in order to represent the current situation of the vessel’s connections. Linear displacement gauges as well as non-contacting image correlation systems were used as measurement methods to analyze the behaviour of the test sample. A validated computer model, using finite element method (FEM) simulations, with Vasa-material properties will be used to calculate the stiffness coefficients, which will be included in a simplified full-computer model of the entire vessel. Based on the latter, the overall and local displacements will be obtained. This is a necessary input in a full numerical model of the ship to optimize a new support structure.

  • 38.
    Hedlund, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. Doktorand, Uppsala Universitet.
    Kamf, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Gamstedt, Kristoffer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Fast Optimization Methodology for Press-fitted Composite Hollow Cylinder Flywheel Energy StorageIn: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085Article in journal (Refereed)
    Abstract [en]

    An optimization strategy for a hollow flywheel energy storage is presented. Several press-fitted shells of anisotropic materials (such as carbon composites) are studied by an analytical model based on a plane stress assumption. The optimization target is stored energy. The optimizer constraints (which were evaluated at full and zero charge level, respectively) were based on strain-based models for fatigue life of composites, and stress-based fatigue life models for high-strength aluminum. A compiled library was built within the scope of this work, and used to run a robust global grid-search optimizing method. The analytical model was compared against a finite element method solution, and the (single-core) library was seen to be at least 5 orders of magnitude faster. 

  • 39. Hendriks, Johannes N.
    et al.
    Jidling, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Schön, Thomas B.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Wills, Adrian
    Wensrich, Christopher M.
    Kisi, Erich H.
    Neutron transmission strain tomography for non-constant stress-free lattice spacing2019In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 456, p. 64-73Article in journal (Refereed)
  • 40.
    Hernandez-Perez, Adrian
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Hagglund, R.
    Carlsson, L. A.
    Aviles, F.
    Analysis of twist stiffness of single and double-wall corrugated boards2014In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 110, p. 7-15Article in journal (Refereed)
    Abstract [en]

    The twist stiffness of single and double-wall corrugated board is analyzed using first order shear deformation (FOSD) theory. Results are compared to finite element analysis (FEA) and dynamic test data for a large range of torsion loaded rectangular board specimens. The FOSD approach and FEA employ a homogenized core. In addition, a structural finite element model was developed where the web core is represented by shell elements. According to FOSD analysis, the twist stiffness is linearly dependent on the transverse shear moduli of the web core along both principal directions of the core. Good agreement between the torsional stiffness predictions by analytical and numerical approaches and test results is found for the range of single and double-wall boards examined. The FOSD solution is significantly less computationally demanding than FEA, and appears viable for prediction of the twist stiffness of corrugated board.

  • 41. Hirsch, J.-M.
    et al.
    Gamstedt, KristoferUppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.Sörensen, J.Rännar, L.-E.Carlbom, I.
    Virtual planning of reconstructions, production ofindividualized implants and transfer of the plan to the operating room incraniomaxillofacial surgery2012Conference proceedings (editor) (Refereed)
  • 42.
    Huc, Sabina
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics. Univ Boras, Fac Text Engn & Business, SE-50190 Boras, Sweden.
    Hozjan, Tomaž
    Univ Ljubljana, Fac Civil & Geodet Engn, SI-1000 Ljubljana, Slovenia.
    Numerical analysis of moisture-induced strains and stresses in glued-laminated timberIn: Article in journal (Refereed)
  • 43.
    Hultmar, Oscar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Paulsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Sundell, Jonathan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Mechanical design and construction of solar panel experiment in stratospheric conditions2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This project will be a part of the LODESTAR experiment. LODESTAR is one of the experiments scheduled to fly on the REXUS/BEXUS 26 high altitude balloon flight. The primary objective of the experiment is to investigate the effects of cosmic radiation on CIGS solar cells. The objective of this project is to build a mechanical design that can fulfill all requirements set by the ESA user manual.

    The mechanical design will first be drawn in mechanical CAD, where the drawing will be constructed from the ESA requirements. Later the design will be simulated in order to choose appropriate materials and a design that can withstand all simulations. Lastly the design will be built according to the drawings and tested according to the simulations.

    The mechanical design withstood all the simulations and verification tests with no visual deformation, except for the simulation and verification of the drop test. Both the drop simulation and verification test resulted in deformation in one of the aluminium plates.

    Since this mechanical design is constructed to be used only once, small deformations is within the margin of error. The deformation resulted by the simulation and verification of the drop test matched with a high precision. This is a good confirmation of the results of the drop test.

    In conclusion, the executed tests gave very promising results. Therefor the design constructed fits all the requirements to travel with solar panels in stratospheric conditions.

  • 44.
    Huo, Jinxing
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Biomechanical Analysis of Stress and Stiffness of New Load-Bearing Implants2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Medical implants are essential products for saving lives and improving life quality. Nowadays, the demand for implants, especially biocompatible and personalized ones, is increasing rapidly to deal with factors like congenital malformations, aging, and increasing prevalence of cancer. To facilitate their clinical applications, better understanding of their biomechanical properties is important. This thesis focuses on tubular and mandibular implants, and aims at studying stiffness properties and assessing stress distributions.

    Tubular implants with coupled helical-coil structure, which can be potentially used as tubular organ constructs, were manufactured by winding polycaprolactone filaments. Tensile and bending stiffnesses were evaluated through mechanical testing and finite element simulations. By increasing the number of helical coils, we could realize a new type of tubular implants which could be used in applications like trachea and urethra stents. Stiffness properties of such implants were investigated analytically, due to the geometrical periodicity. Through computational homogenization, the discrete mesh structures were converted to equivalent continua, whose structural properties were studied using composite beam theories. The numerical and analytical models developed can serve as tools for the mechanical design of implants.

    A patient-specific mandibular implant, additively manufactured of titanium alloys, failed shortly after surgery. The failure was studied using a numerical approach. Finite element models were generated from the 3D bone reconstructed from computed tomography data and implants processed by computational homogenization. The failure location and that of the numerically predicted largest von Mises stress agree well, which confirms the feasibility of using finite element simulations to quantitatively analyze implant failures and assist in implants design.

    For implant failures caused by local bone loss, analytical studies were also carried out to assess the stress distribution around screw-loaded holes in bones. The mandibular bone was treated as a laminate of which elastic properties were obtained by classical laminate theory. The stress profiles were predicted using a complex stress function method. The loading direction was found to have a minor influence on the stress distributions, while the friction coefficient has non-negligible influence. The stress state can serve as starting point to predict bone remodeling and be compared with criteria for bone strength.

    List of papers
    1. Parametric elastic analysis of coupled helical coils for tubular implant applications: Experimental characterization and numerical analysis
    Open this publication in new window or tab >>Parametric elastic analysis of coupled helical coils for tubular implant applications: Experimental characterization and numerical analysis
    Show others...
    2014 (English)In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 29, p. 462-469Article in journal (Refereed) Published
    Abstract [en]

    Coupled helical coils show promising mechanical behavior to be used as tubular organ constructs, e.g., in trachea or urethra. They are potentially easy to manufacture by filament winding of biocompatible and resorbable polymers, and could be tailored for suitable mechanical properties. In this study, coupled helical coils were manufactured by filament winding of melt-extruded polycaprolactone, which was reported to demonstrate desired in vivo degradation speed matching tissue regeneration rate. The tensile and bending stiffness was characterized for a set of couple helical coils with different geometric designs, with right-handed and left-handed polymer helices fused together in joints where the filaments cross. The Young's modulus of unidirectional polycaprolactone filaments was characterized, and used as input together with the structural parameters of the coupled coils in finite element simulations of tensile loading and three-point bending of the coils. A favorable comparison of the numerical and experimental results was found, which paves way for use of the proposed numerical approach in stiffness design under reversible elastic conditions of filament wound tubular constructs.

    Keywords
    Coupled helical coils, Finite element simulation, Structural stiffness, Tubular implants
    National Category
    Natural Sciences Engineering and Technology
    Research subject
    Engineering science with specialization in Applied Mechanics
    Identifiers
    urn:nbn:se:uu:diva-218968 (URN)10.1016/j.jmbbm.2013.09.026 (DOI)000330085700042 ()
    Available from: 2014-02-20 Created: 2014-02-20 Last updated: 2017-12-06Bibliographically approved
    2. Elastic analyses of periodic rhombic mesh structures
    Open this publication in new window or tab >>Elastic analyses of periodic rhombic mesh structures
    (English)Manuscript (preprint) (Other academic)
    National Category
    Applied Mechanics
    Identifiers
    urn:nbn:se:uu:diva-262684 (URN)
    Available from: 2015-09-18 Created: 2015-09-18 Last updated: 2015-10-27
    3. Applicability of a two-stage analytical model of the stiffness of mesh tubes
    Open this publication in new window or tab >>Applicability of a two-stage analytical model of the stiffness of mesh tubes
    (English)Manuscript (preprint) (Other academic)
    National Category
    Applied Mechanics
    Identifiers
    urn:nbn:se:uu:diva-262685 (URN)
    Available from: 2015-09-18 Created: 2015-09-18 Last updated: 2015-10-27
    4. Failure location predictoin by finite element analysis for an additive manufactured mandible implant
    Open this publication in new window or tab >>Failure location predictoin by finite element analysis for an additive manufactured mandible implant
    Show others...
    2015 (English)In: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 37, no 9, p. 862-869Article in journal (Refereed) Published
    Abstract [en]

    In order to reconstruct a patient with a bone defect in the mandible, a porous scaffold attached to a plate, both in a titanium alloy, was designed and manufactured using additive manufacturing. Regrettably, the implant fractured in vivo several months after surgery. The aim of this study was to investigate the failure of the implant and show a way of predicting the mechanical properties of the implant before surgery. All computed tomography data of the patient were preprocessed to remove metallic artefacts with metal deletion technique before mandible geometry reconstruction. The three-dimensional geometry of the patient's mandible was also reconstructed, and the implant was fixed to the bone model with screws in Mimics medical imaging software. A finite element model was established from the assembly of the mandible and the implant to study stresses developed during mastication. The stress distribution in the load-bearing plate was computed, and the location of main stress concentration in the plate was determined. Comparison between the fracture region and the location of the stress concentration shows that finite element analysis could serve as a tool for optimizing the design of mandible implants.

    National Category
    Applied Mechanics
    Identifiers
    urn:nbn:se:uu:diva-262683 (URN)10.1016/j.medengphy.2015.06.001 (DOI)000361409100005 ()
    Available from: 2015-09-18 Created: 2015-09-18 Last updated: 2017-12-04Bibliographically approved
    5. An analytical study of stress distributions around screws in mandibular bone
    Open this publication in new window or tab >>An analytical study of stress distributions around screws in mandibular bone
    (English)Manuscript (preprint) (Other academic)
    National Category
    Applied Mechanics
    Identifiers
    urn:nbn:se:uu:diva-262686 (URN)
    Available from: 2015-09-18 Created: 2015-09-18 Last updated: 2015-10-27
  • 45.
    Huo, Jinxing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Dérand, Per
    Department of Oral and Maxillofacial Surgery, Skåne University Hospital.
    Rännar, Lars-Erik
    Sports Tech Research Centre, Mid Sweden University.
    Hirsch, Jan-Michaél
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Oral and Maxillofacial Surgery.
    Gamstedt, E. Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Failure location predictoin by finite element analysis for an additive manufactured mandible implant2015In: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 37, no 9, p. 862-869Article in journal (Refereed)
    Abstract [en]

    In order to reconstruct a patient with a bone defect in the mandible, a porous scaffold attached to a plate, both in a titanium alloy, was designed and manufactured using additive manufacturing. Regrettably, the implant fractured in vivo several months after surgery. The aim of this study was to investigate the failure of the implant and show a way of predicting the mechanical properties of the implant before surgery. All computed tomography data of the patient were preprocessed to remove metallic artefacts with metal deletion technique before mandible geometry reconstruction. The three-dimensional geometry of the patient's mandible was also reconstructed, and the implant was fixed to the bone model with screws in Mimics medical imaging software. A finite element model was established from the assembly of the mandible and the implant to study stresses developed during mastication. The stress distribution in the load-bearing plate was computed, and the location of main stress concentration in the plate was determined. Comparison between the fracture region and the location of the stress concentration shows that finite element analysis could serve as a tool for optimizing the design of mandible implants.

  • 46.
    Huo, Jinxing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Gamstedt, E. Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Applicability of a two-stage analytical model of the stiffness of mesh tubesManuscript (preprint) (Other academic)
  • 47.
    Huo, Jinxing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Hirsch, Jan-Michaél
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Oral and Maxillofacial Surgery.
    Deránd, Per
    Lund University.
    Rännar, Lars-Erik
    Mittuniversitetet.
    Gamstedt, E. Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Finite Element Investigation of the In - Vivo Failure of a Titanium Alloy HumanJaw Implant2014Conference paper (Refereed)
    Abstract [en]

    In order to reconstruct a patient with a bone defect in the right lower jaw, a scaffold attached to a reconstruction plate, both in a titanium alloy, was designed and manufactured using three-dimensional printing technique. Regrettably the implant fractured in situ several months after surgery. This paper is orientated to investigate the reason for the implant’s failure and provide a way of predicting the mechanical properties of the implant before surgery. Preoperative, postoperative and implant-break computed tomography data of the patient were provided by the responsible surgeon. Metallic artifacts introduced by previous dental implants were removed with metallic deletion technique software beforehand. Three-dimensional volume of the patient’s jaw was thereafter reconstructed with trabecular bone removed based on the cleaned computed tomography data. The implant, screws and jaw were assembled together and meshed with triangular elements in Mimics 16.0. The assembly was imported into in-house software with surface mesh converted to linear tetrahedral mesh. Simulations were implemented under simplified but suitable loading conditions with the assumption that jaw was a linear elastic and homogeneous material. The stress distribution on the implant plate was calculated and the location of stress concentration on the plate was determined and then verified by the clinical data of the patient. This validated model could serve in the future as a tool for optimizing the design of jaw implants.

  • 48.
    Huo, Jinxing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Hirsch, Jan-Michaél
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Oral and Maxillofacial Surgery.
    Gamstedt, E. Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    An analytical study of stress distributions around screws in mandibular boneManuscript (preprint) (Other academic)
  • 49.
    Huo, Jinxing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Rojas, RamiroKTH Royal Institute of Technology.Bohlin, JanUppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.Hilborn, JönsUppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.Gamstedt, E. KristoferUppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Parametric analysis of stiffness properties of coupled helical coils for implant application2013Conference proceedings (editor) (Refereed)
  • 50.
    Huo, Jinxing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    van Dijk, Nico
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Gamstedt, E. Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Elastic analyses of periodic rhombic mesh structuresManuscript (preprint) (Other academic)
123 1 - 50 of 132
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf