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  • 301. Eriksson, Anders
    USING EIGENVECTOR PROJECTIONS TO IMPROVE CONVERGENCE IN NON-LINEAR FINITE ELEMENT EQUILIBRIUM ITERATIONS.1987In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 24, no 3, p. 497-512Article in journal (Refereed)
    Abstract [en]

    In an earlier paper a method for calculation of non-linear structural response was described. A method for selective damping of solution components parallel to critical eigenvectors was proposed, reducing the risk for diverging equilibrium iterations. This method is, in the present paper, shown to be related to the 'dynamic relaxation' approach. The method has been further studied for practical problems, and especially adapted for the analysis of plate buckling. A method for variable damping is proposed, and compared to existing methods. The conclusions are that damping, based on eigenvector projection, is an efficient way to improve the stability in the iterations, and in this an alternative to other methods for choice of optimum corrections in N-R schemes. In the paper, suitable criteria for reformulation of the tangential relation during iterations in a step are also discussed.

  • 302.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    USING EIGENVECTOR PROJECTIONS TO IMPROVE CONVERGENCE IN NON-LINEAR FINITE ELEMENT EQUILIBRIUM ITERATIONS.1987In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 24, no 3, p. 497-512Article in journal (Refereed)
    Abstract [en]

    In an earlier paper a method for calculation of non-linear structural response was described. A method for selective damping of solution components parallel to critical eigenvectors was proposed, reducing the risk for diverging equilibrium iterations. This method is, in the present paper, shown to be related to the 'dynamic relaxation' approach. The method has been further studied for practical problems, and especially adapted for the analysis of plate buckling. A method for variable damping is proposed, and compared to existing methods. The conclusions are that damping, based on eigenvector projection, is an efficient way to improve the stability in the iterations, and in this an alternative to other methods for choice of optimum corrections in N-R schemes. In the paper, suitable criteria for reformulation of the tangential relation during iterations in a step are also discussed.

  • 303. Eriksson, Anders
    USING EIGENVECTOR PROJECTIONS TO IMPROVE CONVERGENCE IN NON-LINEAR FINITE ELEMENT EQUILIBRIUM ITERATIONS.1987In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 24, no 3, p. 497-512Article in journal (Refereed)
    Abstract [en]

    In an earlier paper a method for calculation of non-linear structural response was described. A method for selective damping of solution components parallel to critical eigenvectors was proposed, reducing the risk for diverging equilibrium iterations. This method is, in the present paper, shown to be related to the 'dynamic relaxation' approach. The method has been further studied for practical problems, and especially adapted for the analysis of plate buckling. A method for variable damping is proposed, and compared to existing methods. The conclusions are that damping, based on eigenvector projection, is an efficient way to improve the stability in the iterations, and in this an alternative to other methods for choice of optimum corrections in N-R schemes. In the paper, suitable criteria for reformulation of the tangential relation during iterations in a step are also discussed.

  • 304.
    Eriksson, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Faroughi, Shirko
    Quasi-static inflation simulations based on a co-rotational triangular space membrane element2013In: International Journal of Structural Stability and Dynamics, ISSN 0219-4554, Vol. 13, no 3, p. 1250067-Article in journal (Refereed)
    Abstract [en]

    Co-rotational triangular space membrane elements are developed for the quasi-static analysis of very thin structures subjected to pressure loadings from compressible media, aiming primarily at simulations of inflation processes. By separating rigid body motion and deformational displacement, the major part of geometric nonlinearity is treated by a co-rotational filter. With the formulation, hyper-elastic and linear elastic material models are used in the local plane element expressions. Numerical experiments show that either material model can be used in the present context, but that the linearly elastic model demands an optimal reference system. The hyper-elastic form is useful also for very large expansions, but the neo-Hookean expression chosen has some limitations for large strains. Simulations are parameterized by internal over-pressure, but an amount of injected gas can be calculated from pressure and enclosed volume. The uniqueness and stability in the response of the structures must be seen as a function of either pressure or amount of gas, dependent on the precise mechanism for inflation.

  • 305.
    Eriksson, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Kouhia, R.
    On step size adjustments in structural continuation problems1995In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 55, no 3, p. 495-506Article in journal (Refereed)
    Abstract [en]

    Procedures for automatic step size control in non-linear structural equilibrium analyses are discussed. Some algorithms found in the literature are briefly described and compared. The main emphasis is given to the development of criteria for detecting the need for a change of the step size as early as possible. Hence, the size of the increment is controlled during the corrector phase. Two possible procedures for this are developed and compared. Both reduce the step size in highly curved parts of an equilibrium path. The performance of the proposed algorithm is demonstrated in some numerical examples, including both geometrical and material non-linearities. The conclusions are that a procedure for reduction of the step size within the step can give improved possibilities for convergence in the iterations. The need for suitable scaling of used variables in any continuation algorithm is also emphasized. © 1995.

  • 306.
    Eriksson, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Ludvigsson, Jan
    KTH.
    Datorn för byggnadskonstruktionarbete - metoder, möjligheter och risker1983Book (Other academic)
  • 307.
    Eriksson, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Marti, K.
    Müller-Hannemann, M.
    Topping, BHV.
    Mota-Soares, CA.
    Engineering computational technology2007In: Advances in Engineering Software, ISSN 0965-9978, E-ISSN 1873-5339, Vol. 38, no 11-12, p. 723-725Article in journal (Refereed)
  • 308.
    Eriksson, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Månsson, JohanKTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.Tibert, GunnarKTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    NSCM-17: Proceedings of the 17th Nordic Seminar on Computational Mechanics2004Conference proceedings (editor) (Refereed)
  • 309.
    Eriksson, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Nordmark, Arne
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Constrained stability of conservative static equilibrium2019In: Computational Mechanics, ISSN 0178-7675, E-ISSN 1432-0924, Vol. 64, no 4, p. 1199-1219Article in journal (Refereed)
    Abstract [en]

    Modelling of static structural stability problems is considered. Focus is set on problems where passive physical constraints affect the response to applied forces, and where more than one free parameter describes the setting. The existence of vibration frequencies at equilibrium states is investigated, as an indication of stability. The relevant Jacobian matrix is developed, with an emphasis on the necessity to formulate the constraint equations from an energy form in a conservative problem. The corresponding mass matrix is introduced, with zero mass contribution from constraint equations. Three different forms of the relevant Jacobians are considered, and alternative methods for the eigenvalue extraction given. Stability is discussed in a context of generalized equilibrium problems, where auxiliary parameters and equations can be included in a continuation setting. Examples show the formulation, implementation and interpretation of stability.

  • 310.
    Eriksson, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Nordmark, Arne
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Instability of hyper-elastic balloon-shaped space membranes under pressure loads2012In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 237, p. 118-129Article in journal (Refereed)
    Abstract [en]

    This paper discusses the evaluation of quasi-static equilibrium solutions for inflatable space membrane structures. A Mooney-Rivlin hyper-elastic material model, with variable constitutive constants, is considered. A compressible weightless medium is used to introduce within the membrane a one-parametric over-pressure loading compared to an ambient pressure. Analytical instability results are shown for a spherical and derived for a cylindrical case. These are compared to numerical simulations based on a flat linearly interpolated triangular space membrane element. Path-following procedures are used to find generalized equilibrium paths, with different parameterizations. Numerical examples show that the methods developed can give information on the stability of the membranes, but that the medium and means for introducing the internal pressure are of importance for the interpretation of stability.

  • 311.
    Eriksson, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Nordmark, Arne
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Instability of thin hyper-elastic space membranes under pressure loads2011In: Proceedings of TCCM-2011, 2011Conference paper (Refereed)
  • 312.
    Eriksson, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Nordmark, Arne
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Symmetry aspects in stability investigations for thin membranes2016In: Computational Mechanics, ISSN 0178-7675, E-ISSN 1432-0924, Vol. 58, no 5, p. 747-767Article in journal (Refereed)
    Abstract [en]

    Modelling of structural instability problems is considered for thin square membranes subjected to hydrostatic pressure, with a focus on the effects from symmetry conditions considered or neglected in the model. An analysis is performed through group-theoretical concepts of the symmetry aspects present in a flat membrane with one-sided pressure loading. The response of the membrane is described by its inherent differential eigensolutions, which are shown to be of five different types with respect to symmetry. A discussion is given on how boundary conditions must be introduced in order to catch all types of eigensolutions when modelling only a subdomain of the whole. Lacking symmetry in a FEM model of the whole domain is seen as a perturbation to the problem, and is shown to affect the calculated instability response, hiding or modifying instability modes. Numerical simulations verify and illustrate the analytical results, and further show the convergence with mesh fineness of different aspects of instability results.

  • 313.
    Eriksson, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Pacoste, C.
    Zdunek, A.
    Numerical analysis of complex instability behaviour using incremental-iterative strategies1999In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 179, no 3-4, p. 265-305Article in journal (Refereed)
    Abstract [en]

    The paper describes how quasi-static, conservative instability problems can be analysed in a multi-parametric space, using generalised path-following procedures for augmented equilibrium problems. The general formulation of such augmented equilibrium problems is discussed in some detail. The focus is set on two classes of generalised 1D paths: basic equilibrium paths and fold lines, i.e. critical subset paths. The solution methods are seen as extensions to common incremental-iterative strategies, allowing the computation of subsets of equilibrium states which also fulfil some auxiliary conditions, e.g. criticality. In this context, some emphasis is also given to the evaluation of the properties of the problem, at a certain state; the tangential stiffness is here used to evaluate - possibly multidimensional - tangent spaces, and in the isolation of special states, i.e. vanishing variables, turning points and exchanges of stability, being important aspects of instability analyses. A set of carefully chosen numerical examples demonstrate on one hand the ability of the numerical procedures to deal with complex instability phenomena, including coincident or near coincident buckling modes, modal interaction, secondary bifurcations, and, on the other hand, their versatility in performing parameter sensitivity analyses. Finally, comparisons with alternative techniques, based on asymptotic strategies, are also put forth. © 1999 Elsevier Science S.A.

  • 314.
    Eriksson, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Thomasson, Per-Olof
    (KTH).
    On the behaviour of clamped plates loaded in comrpession. Some results from computer calculations.1987In: Proc. ECCS Int. Colloquium on stability of plates and shells, Ghent, 1987Conference paper (Refereed)
  • 315.
    Eriksson, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Tibert, GunnarKTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Proceedings of NSCM-23: the 23rd Nordic seminar on computational mechanics2010Conference proceedings (editor) (Other academic)
  • 316.
    Eriksson, Axel
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Fatigue Injection Moulded Short Fibre Reinforced Polymers2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In order to keep up with the increasing demand of fuel-efficiency in the transportationindustry, the interest of making the vehicles as lightweight as possible is steadilyincreasing. One of the ways of reducing the weight is to introduce an anisotropicmaterial as Short Fibre Reinforced Polymers (SFRP) as a replacement for structuralparts made out of metals. To meet the modern vehicle design process which strivestowards a more simulation driven workflow, the need for accurate simulations offibre reinforced composites is of importance.This thesis aims to evaluate and find a working process for fatigue analysis of injectionmoulded SFRP components. To evaluate the fatigue analysis procedure anexisting SFRP component has been studied. The component is the front bracket thatmounts the roof air deflector to the roof on Scania trucks. To correlate the fatigue lifeestimation from the fatigue analysis, experiments were performed at ÅF Test Centerin Borlänge.The anisotropic behaviour is modelled using the commercial software Digimat togetherwith an injection simulation provided by Scania, to estimate the fibre orientationand thereby the material behaviour of the SFRP component. The fatigue analysiswas conducted by performing a coupled structural analysis between Digimat-Abaqus and then import the resulting stress- and strain-fields into the fatigue postprocessornCode DesignLife. The stress is then cyclic tested towards experimentallydetermined S-N curves determined in Digimat.Due to restriction of available fatigue data for the plastic in the front bracket, a fatiguematerial model for a plastic containing the same fibres and matrix but witha different fibre amount was implemented. The fatigue data were scaled using theUTS method to get a good characterisation of the real-life material behaviour of theplastic of the front bracket component.From the correlation between the fatigue analysis and performed experiments, itwas shown that the simulated fatigue life was conservative compared to the fatiguelife determined from the experiments. However, the correlation between the fatigueanalysis and experiments is not fully captured but gives a better estimation of thefatigue life compared to performing the fatigue analysis using an isotropic materialmodel.

  • 317.
    Eriksson, Viktor
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Automated surveillance of spectrum loading and impact on fatigue life2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 318.
    Erlandsson, Stefan
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Rikoschetter från finkalibrig ammunition.2012Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Försvarsmakten har köpt in en ny typ av ammunition till Ak 5 och Ksp 90,

    miljöammunition. Den nya ammunitionen har en stålkärna istället för en blykärna. För

    att vikten på projektilen skall vara den samma har projektilen gjorts något längre.

    Eftersom stål har andra materialegenskaper än bly kommer den nya projektilen (5,56

    mm sk ptr 5B stkprj) att studsa, rikoschettera annorlunda än den gamla.

    Rikoschetter utgör en risk för såväl egna förband som tredje person vilket gör att det är

    av största vikt att förstå fenomenet, försöka minimera sannolikheten för att rikoschett

    ska uppstå och att uppdatera säkerhetsföreskrifterna. Försvarsmakten har under 2011

    initierat ett rikoschettprojekt på FOI med inriktning mot finkaliberammunition och

    riskområdesberäkningar. Inom ramen för detta behövs modeller för att kunna förutsäga

    risken för rikoschett mot olika målmaterial.

    Detta examensarbete syftar till att ge en analys av tillgängliga rikoschettmodeller med

    fokus på vilka fall som kan hanteras, vilka indata som krävs och vilka resultat modellen

    kan förutsäga (t.ex. rikoschettvinkel och hastighetsminskning). Då tillgången till

    användbara modeller visat sig vara begränsad har ett arbete påbörjats för att fastställa

    olika parametrars inverkan på rikoschettutfallet. Den parameter som bedömdes

    intressantast att börja med var projektilkärnans hårdhet, dels därför att den sannolikt

    har stor betydelse för rikoschetten, dels för att den nya miljöammunitionen har ett

    annat kärnmaterial än den gamla och dels för att kärnmaterialet i hotammunition

    varierar avsevärt.

    Den experimentella studien visade på en klar korrelation mellan ökad hårdhet och ökad

    rikoschettvinkel, en hårdare projektil studsar mer än en mjukare. Den visade även på

    att hårdheten inte har en inverkan på rikoschetthastigheten.

    Den numeriska studien ger en användbar skattning med ett fel på ca 0 till 10 %.

    De empiriska modellerna var inte tillräckligt tillförlitliga för att göra användbara

    skattningar av varken rikoschetthastigheten eller rikoschettvinkeln.

  • 319.
    Essén, Hanno
    et al.
    KTH, Superseded Departments, Mechanics.
    Nordmark, Arne B.
    KTH, Superseded Departments, Mechanics.
    Hamiltonian of a homogeneous two-component plasma2004In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 69, no 3Article in journal (Refereed)
    Abstract [en]

    The Hamiltonian of one- and two-component plasmas is calculated in the negligible radiation Darwin approximation. Since the Hamiltonian is the phase space energy of the system its form indicates, according to statistical mechanics, the nature of the thermal equilibrium that plasmas strive to attain. The main issue is the length scale of the magnetic interaction energy. In the past a screening length lambda=1/rootr(e)n, with n number density and r(e) classical electron radius, has been derived. We address the question whether the corresponding longer screening range obtained from the classical proton radius is physically relevant and the answer is affirmative. Starting from the Darwin Lagrangian it is nontrivial to find the Darwin Hamiltonian of a macroscopic system. For a homogeneous system we resolve the difficulty by temporarily approximating the particle number density by a smooth constant density. This leads to Yukawa-type screened vector potential. The nontrivial problem of finding the corresponding, divergence free, Coulomb gauge version is solved.

  • 320.
    Etikan, Mehmet Kaan
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Fatigue Analysis of a Welded Aluminium Joint2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this project, the fatigue behaviour of aluminium (AL 5083 H111) gusset and flange joined with a fillet weld, is investigated through experiments and numerical methods. The work aims at improved knowledge on fatigue in an aluminium welded joint subjected to constant amplitude varying load.

     

    The results of the experiments are investigated with the Basquin equation. The mean curve is estimated by the maximum likelihood estimation (MLE) by using both the failed specimen data and the run-out data. From the mean curve, a component specific design curve is estimated. Comparison of the component specific design curve with the recommendation’s design curve highlighted the inherent conservatism of the recommendation’s design curve.

     

    Nominal, hot-spot and equivalent notch methods were evaluated, and a comparative study was performed. The numerical investigation showed that the predicted fatigue life increased with model complexity. Comparison to the experimentally derived component specific design curve highlighted non-conservatism of the numerically predicted fatigue life for large stress ranges. The degree of conservatism of the numerical methods is however strongly affected by the slope of the considered design curve.

  • 321.
    Everitt, Carl-Magnus
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Initiation of rolling contact fatigue from asperities in elastohydrodynamic lubricated contacts2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Rolling contacts are utilized in many technical applications, both in bearings and in the contact between gear teeth. These components are often highly loaded, which makes them susceptible to suffer from rolling contact fatigue. This work focuses on the rolling contact fatigue mechanism of pitting. In order to attain a better understanding of why pitting initiates and grows, detailed simulations of rolling contacts have been performed. In particular the contact between two gears in a truck retarder was here used as a case study. The investigated contact experienced elastohydrodynamic lubrication conditions since the load was high enough to causes the surfaces in contact to deform and the viscosity of the lubricant to increase significantly.

    In Paper A it was investigated if surface irregularities in the size of the surface roughness are large enough to cause surface initiated fatigue. The investigation focused on the pitch line since small surface initiated pits were found here even though there was no slip present. Since there were pits present at the pitch line, it is important that the theories of pitting can explain the development of pits also in the absence of slip. The conclusion of the work was that surface irregularities of the size of normal surface roughness are enough to cause surface initiated fatigue at the pitch line.

    In Paper B it was investigated why pits are more likely to initiate in the dedendum of pinion gears than in the addendum. In both areas slip is present but in different directions. In the dedendum the friction from slip is against the rolling direction which enhances the risk for pitting. The investigation was performed by studying the effect of the temperature rise in the contact caused by the slip. The conclusion drawn was that the temperature rise in the contact explained why pitting was more common in the dedendum than in the addendum.

  • 322.
    Everitt, Carl-Magnus
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Alfredsson, Bo
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Contact fatigue initiation and tensile surface stresses at a point asperity which passes an elastohydrodynamic contact2018In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 123, p. 234-255Article in journal (Other academic)
    Abstract [en]

    Contact mechanics and tribology was combined with fundamental fatigue and fracture mechanics to form a new mechanism for surface initiated rolling contact fatigue. Following, fatigue was investigated numerically for single asperities and craters in lubricated rolling contact surfaces. The hypothesis suggests that asperity point contacts can create sufficiently large tensile stresses for fatigue. The investigated case corresponded to a heavily loaded truck gear with ground surfaces. Reynolds equation resolved the elastohydrodynamic effect of the asperity in the transient three dimensional contacts. The Findley critical plane criterion was used for multiaxial and non-proportional fatigue evaluation. The simulations confirmed the new mechanism for rolling contact fatigue and showed how asperities can create contact fatigue in the lubricated contacts even without slip.

  • 323.
    Everitt, Carl-Magnus
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Alfredsson, Bo
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    The asperity point load mechanism for rolling contact fatigue considering slip and thermal elastohydrodynamic lubricationManuscript (preprint) (Other academic)
    Abstract [en]

    Rolling contact fatigue was investigated numerically for a single asperity and crater passing through lubricated rolling contacts with slip. The purposes was to explain why rolling contact fatigue pits develop in the forward rolling direction when slip is negative and to further verify the asperity point load mechanism for pitting. The simulations included thermal effects from friction and compression of the lubricant. It was concluded that heating of the lubricant decreased the viscosity and the contact shear stress profile in the second half of the contact, which provided an asymmetric stress profile and explained the pitting damage behaviour in relation to slip direction. 

  • 324. Ezzat, A
    et al.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM).
    Jolles, F
    Self-started Blade Vibrations in an Annular Turbine Cascade Operating at Transonic and Supersonic Mach Numbers1989Conference paper (Refereed)
  • 325. Ezzat, A
    et al.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM).
    Jolles, F
    Steady-State and Time Dependent Aerodynamics in an Annular Turbine Cascade Operating at High Subsonic Mach Numbers1989Conference paper (Refereed)
  • 326.
    Facciolo, Luca
    et al.
    KTH, Superseded Departments, Mechanics.
    Alfredsson, P. Henrik
    KTH, Superseded Departments, Mechanics.
    The counter-rotating core of a swirling turbulent jet issued from a rotating pipe flow2004In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 16, no 9, p. L71-L73Article in journal (Refereed)
    Abstract [en]

    Axially rotating turbulent pipe flow is an example where rotation strongly affects the turbulence and thereby the Reynolds stresses and mean flow properties. The present Letter reports new measurements where a rotating pipe flow is used to establish a swirling jet. The measurements in the jet show that at some distance downstream (approximately 6 nozzle diameters) the central part of the jet starts to rotate in the opposite direction as compared to the rotation of the pipe. This effect is explained by the influence of the cross flow Reynolds stress originating in the pipe flow.

  • 327.
    Fadil, Hassan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Jelagin, Dennis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    On the Measurement of two Independent Viscoelastic Functions with Instrumented Indentation Tests2018In: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 58, no 2, p. 301-314Article in journal (Refereed)
    Abstract [en]

    In the present paper, a methodology for complete characterization of linear isotropic viscoelastic material with spherical instrumented indentation test is proposed. The developed method allows for measuring two independent viscoelastic functions, shear relaxation modulus and time-dependent Poisson's ratio, from the indentation test data obtained at non-decreasing loading, but otherwise arbitrary. Finite element modelling (FEM) is relied upon for validating the proposed methodology and for quantifying the influence of experimental variables on the measurements accuracy. Spherical indentation experiments are performed on several viscoelastic materials: polyoxymethylene, bitumen and bitumen-filler mastics. The viscoelastic material functions obtained with the indentation tests are compared with the corresponding results from the standard mechanical tests. Numerical and experimental results presented indicate that the methodology proposed allows mitigating the machine compliance and loading rate effects on the accuracy of the viscoelastic indentation tests.

  • 328.
    Fagerberg, Linus
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Zenkert, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Reasonable Knock-Down Factors for Sandwich Face Wrinkling2008Conference paper (Other academic)
    Abstract [en]

    Design rules and formulas used to predict wrinkling failure of sandwich structures ofteninclude a knockdown factor to compensate for "imperfections" in the sandwich structure. The knockdown is usually based on experience and empirically derived from compression testing. It can be substantially large and clearly affect the design. For example the most widely used Hoff's formula suggests a reduction of 45%, from 0.91 to 0.5, due to the effect of imperfections. The wrinkling formulae are also often simplified, thus neglecting the effect of the stacking sequence of the face sheet laminate. These types of rough “rule of thumb” design constraints must be re-evaluated and questioned.Today’s modern design methods and highly optimised structures seek a weigh treduction of the few last percent. This demands a higher level of accuracy in the designprocess and yesterday’s methods must be improved to meet the demand. In this paper an alternative method to derive a reasonable knockdown factor is presented and it is shown that this factor can also be predicted based on constituent material properties and assumed amplitude of initial imperfections. The design method previously published by the authors in [1] is extended to fully anisotropic materials anda first ply failure criterion. The results have thus far been confirmed by tests and good agreement has been achieved.

  • 329.
    Fagerudd, Julie
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Stress simulation of the SEAM CubeSat structure during launch.2015Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A spacecraft is subjected to dynamic and static loads during launch. These loads are deterministic and of random nature and cannot be tested under the real conditions due to cost considerations. The spacecraft must therefore sustain certain mechanical loads without permanent deformation with a certain safety factor due to the uncertainties in the actual loading values during launch. The applicable mechanical test requirements and load combination have been first determined for the structure of interest: the SEAM CubeSat. These requirements are found to be steady-state accelerations, random vibration and shock response spectrum loadings. They have been simulated onto the structure globally and locally in order to extract stress values, amend design features when necessary and determine adequate material properties in order for the final design to fulfill the mechanical requirements during launch.

  • 330.
    Falk, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Architecture, Architectural Technologies.
    Samuelsson, Sture
    KTH, School of Architecture and the Built Environment (ABE), Architecture, Architectural Technologies.
    Tibert, Gunnar
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Plate based tensegrity structures2005In: IASS 2005: Proceedings of the International Symposium on Shell and Spatial Structures, 2005Conference paper (Refereed)
  • 331.
    Fallqvist, Björn
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    On the mechanics of actin and intermediate filament networks and their contribution to cellular mechanics2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The mechanical behaviour of cells is essential in ensuring continued physiological function, and deficiencies therein can result in a variety of diseases. Also, altered mechanical response of cells can in certain cases be an indicator of a diseased state, and even actively promoting progression of pathology. In this thesis, methods to model cell and cytoskeletal mechanics are developed and analysed.

    In Paper A, a constitutive model for the response of transiently cross-linked actin networks is developed using a continuum framework. A strain energy function is proposed and modified in terms of chemically activated cross-links.

    In Paper B, a finite element framework was used to assess the influence of numerous geometrical and material parameters on the response of cross-linked actin networks, quantifying the influence of microstructural properties and cross-link compliance. Also, a micromechanically motivated constitutive model for cross-linked networks in a continuum framework was proposed.

    In Paper C, the discrete model is extended to include the stochastic nature of cross-links. The strain rate dependence observed in experiments is suggested to depend partly on this.

    In Paper D, the continuum model for cross-linked networks is extended to encompass more composite networks. Favourable comparisons to experiments indicate the interplay between phenomenological evolution laws to predict effects in biopolymer networks.

    In Paper E, experimental and computational techniques are used to assess influence of the actin cytoskeleton on the mechanical response of fibroblast cells. The influence of cell shape is assessed, and experimental and computational aspects of cell mechanics are discussed.

    In Paper F, the filament-based cytoskeletal model is extended with an active response to predict active force generation.  Importantly, experimentally observed stiffening of cells with applied stress is predicted.

  • 332.
    Fallqvist, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Kulachenko, Artem
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Kroon, Martin
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Cross-link debonding in actin networks: influence on mechanical properties2015In: International Journal of Experimental and Computational Biomechanics, ISSN 1755-8743, Vol. 3, no 1, p. 16-26, article id b778558v5j17h4n8Article in journal (Refereed)
    Abstract [en]

    The actin cytoskeleton is essential for the continued function and survival of the cell. A peculiar mechanical characteristic of actin networks is their remodelling ability, providing them with a time-dependent response to mechanical forces. In cross-linked actin networks, this behaviour is typically tuned by the binding affinity of the cross-link. We propose that the debonding of a cross-link between filaments can be modelled using a stochastic approach, in which the activation energy for a bond is modified by a term to account for mechanical strain energy. By use of a finite element model, we perform numerical analyses in which we first compare the model behaviour to experimental results. The computed and experimental results are in good agreement for short time scales, but over longer time scales the stress is overestimated. However, it does provide a possible explanation for experimentally observed strain-rate dependence as well as strain-softening at longer time scales.

  • 333. Faroughi, Shirko
    et al.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Co-rotational formulation for dynamic analysis of space membranes based on triangular elements2017In: International Journal of Mechanics and Materials in Design, ISSN 1569-1713, E-ISSN 1573-8841, Vol. 13, no 2, p. 229-241Article in journal (Refereed)
    Abstract [en]

    Nonlinear triangular space membrane elements are developed for the analysis of thin structures subjected to dynamic loading. By using a co-rotated framework, displacements are decomposed into rigid body motions and pure deformational displacements. The novelty of the formulation is that it employs the co-rotated framework to derive tangent dynamic matrix and an inertial force vector. Closed forms for the inertia force vector, the tangent dynamic matrix, the mass matrix and the gyroscopic matrix are derived directly from the current coordinate transformation matrix. Three numerical examples are presented to illustrate the robustness and efficiency of the new co-rotational formulation. The efficiency of the proposed approach is compared to the updated Lagrangian method, and savings in computation of up to 50 %, were achieved.

  • 334.
    Feng, Leiping
    et al.
    KTH, Superseded Departments, Vehicle Engineering.
    Nilsson, A.
    KTH, Superseded Departments, Vehicle Engineering.
    Kari, Leif
    KTH, Superseded Departments, Vehicle Engineering.
    New designs of sandwich engine foundations1998In: International Conference on Sandwich Construction, 1998, p. 289-300Conference paper (Refereed)
  • 335.
    Feng, Leiping
    et al.
    KTH, Superseded Departments, Vehicle Engineering.
    Nilsson, A.
    KTH, Superseded Departments, Vehicle Engineering.
    Kari, Leif
    KTH, Superseded Departments, Vehicle Engineering.
    Vibration of engine foundations1997In: Modern Practice in Stress and Vibration Analysis / [ed] M D Gilchrist, Rotterdam: Balkema, 1997, p. 311-316Conference paper (Refereed)
  • 336.
    Ferrazzi, Giulio
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Numerical modeling of Atomic Force Microscopy (AFM) towards estimation of material parameters from fibroblast cells.2011Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    It has a long been known that many, if not all, diseases are associated with changes in the mechanical

    properties of cells. Although these changes in tissue mechanics have been believed to be a

    conseguence of the disease, recent data show that alterations of these mechanical properties have

    potent eect to many cellular functions. Thus, there is no reason to believe that altered cellular

    mechanics could be a cause of the disease, rather than its consequence. A complete understanding

    of cell mechanics and how the latter one depends on the presence of a disease is therefore necessary

    in order to develop methods of early diagnosis.

    In this master thesis we report the preliminary results of cell mechanical response of broblasts

    obtained simulating AFM (Atomic Force Microscopy) with COMSOL 4.1. Specically, we tried to

    nd out what is the relationship that coexists between the reaction force of a broblast when urged

    by this type of technique. A subsequent process of reverse engineering led to a simply analytical

    model for the quantication of the mechanical properties of this type of cell.

    The second part of this work aims to improve the understading of the mechanotrasduction

    mechanism of cells. The second model, indeed, reports the results of soft concact and adhesion of

    a broblast with a polyacrylamide substrate.

    Finally, we built up a numerical model that combines the assumptios of the rst and the second one.

  • 337.
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    A symmetric formulation for experimental statistical energy analysis1999In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 223, p. 161-169Article in journal (Refereed)
  • 338.
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Book Review: David A. Bies and Colin H. Hansen : Engineering Noise Control, Theory and Practice2005In: Journal of Vibration and Acoustics-Transactions of the ASME, ISSN 1048-9002, E-ISSN 1528-8927, Vol. 127, no 1, p. 104-104Article, book review (Other academic)
  • 339.
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Comments on: “The high-frequency response of a plate carrying a concentrated mass/spring system."1999In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 225, p. 783-800Article in journal (Refereed)
  • 340.
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Ensemble averaged vibration energy flows in a three-element structure1995In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 187, p. 495-529Article in journal (Refereed)
  • 341.
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Exact spectral finite element analysis of stationary vibrations in a rail way car structure1994In: Acta Acustica, Vol. 2, p. 461-482Article in journal (Refereed)
  • 342.
    Finnveden, Svante
    KTH, Superseded Departments, Vehicle Engineering.
    Finite element techniques for the evaluation of energy flow parameters: Keynote Lecture2000Conference paper (Refereed)
    Abstract [en]

    In applications of Statistical Energy Analysis (SEA) to complex engineering structures, procedures for the calculation of the SEA parameters are frequently unavailable. This note discusses two Finite Element techniques for identification of energy flow parameters: a waveguide and a modal approach.

  • 343.
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Formulas for modal density and for input power from mechanical and fluid point sources in fluid filled pipes1997In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 208, p. 705-728Article in journal (Refereed)
  • 344.
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Simplified equations of motion for the radial-axial vibrations of fluid filled pipes1997In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 208, p. 685-703Article in journal (Refereed)
  • 345.
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Spectral finite element analysis of stationary vibrations in a beam – plate structure1996In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 82, p. 478-497Article in journal (Refereed)
  • 346.
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Spectral finite element analysis of the vibration of straight fluid-filled pipes with flanges1997In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 199, p. 125-154Article in journal (Refereed)
  • 347.
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Statistical energy analysis of fluid-filled pipes1999In: IUTAM symposium on Statistical Energy Analysis / [ed] F.J Fahy and W.G. Price, Kluwer Academic Publishers, 1999, p. 289-300Chapter in book (Refereed)
  • 348.
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    The boundary condition for a free surface with gravity waves formulated as a locally reacting surface impedance1987In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 112, p. 575-576Article in journal (Refereed)
  • 349.
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Two observations on the wave approach to SEA: Keynote Lecture2007In: 14th International Congress on Sound and Vibration 2007, ICSV 2007, 2007, p. 4483-4501Conference paper (Refereed)
    Abstract [en]

    First, it is shown that the use of SEA coupling factors derived for the coupling of semi infinite systems is consistent with coupling power proportionality. This demonstration is axiomatic, relying on a set of postulates. It is useful in teaching SEA, as it illustrates concepts and assumptions commonly made. It might be useful for research aiming for a better set of postulates upon which a statistical energy method can be built. Second, the wave motion in double walls is investigated. A new SEA formulation is presented in which each element describe one kind of coupled cavity-wall wave motion. This formulation obsoletes the non-resonant transmission paths and compared to classical formulations, it improves results at frequencies around and a bit above the double wall resonance.

  • 350.
    Finnveden, Svante
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Vibration energy transmission in fluid filled pipes connected with flanges1997In: Structural Dynamics, Recent Advances: Proc of the 6th international conference / [ed] N.S. Fergusson, The Institue of Sound and Vibration , 1997, p. 613-627Chapter in book (Refereed)
45678910 301 - 350 of 1194
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