Change search
Refine search result
1 - 33 of 33
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • 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.
    Afzal, Mohammad
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Lopez Arteaga, Ines
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Kari, Leif
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    An analytical calculation of the Jacobian matrix for 3D friction contact model applied to turbine blade shroud contact2016In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 177, p. 204-217Article in journal (Refereed)
    Abstract [en]

    An analytical expression is formulated to compute the Jacobian matrix for 3D friction contact modeling that efficiently evaluates the matrix while computing the friction contact forces in the time domain by means of the alternate frequency time domain approach. The developed expression is successfully used for the calculation of the friction damping on a turbine blade with shroud contact interface having an arbitrary 3D relative displacement. The analytical expression drastically reduces the computation time of the Jacobian matrix with respect to the classical finite difference method, with many points at the contact interface. Therefore, it also significantly reduces the overall computation time for the solution of the equations of motion, since the formulation of the Jacobian matrix is the most time consuming step in solving the large set of nonlinear algebraic equations when a finite difference approach is employed. The equations of motion are formulated in the frequency domain using the multiharmonic balance method to accurately capture the nonlinear contact forces and displacements. Moreover, the equations of motion of the full turbine blade model are reduced to a single sector model by exploiting the concept of cyclic symmetry boundary condition for a periodic structure. Implementation of the developed scheme in solving the equations of motion is proved to be effective and significant reduction in time is achieved without loss of accuracy.

  • 2.
    Ahlström, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Aeroelastic FE modelling of wind turbine dynamicsIn: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243Article in journal (Refereed)
    Abstract [en]

    By designing wind turbines with very flexible components it is possible toreduce loads and consequently the associated cost. As a result, the increased flexibilitywill introduce geometrical nonlinearities. Design tools that can cope with those nonlinearitieswill therefore be necessary at some stage of the design process. The developedmodel uses the commercial finite element system MSC.Marc, which is an advanced finiteelement system focused on nonlinear design and analysis, to predict the structuralresponse. The aerodynamic model named AERFORCE, used to transform the wind toloads on the blades, is a Blade-Element/Momentum model, developed by The SwedishDefence Research Agency (FOI, previously named FFA). The paper describes the developedmodel with focus on component modelling to allow for geometrical nonlinearities.Verification results are presented and discussed for an extensively tested Danwin 180 kWstall-controlled wind turbine. Code predictions of mechanical loads, fatigue and spectralproperties, obtained at normal operational conditions, have been compared with measurements.The simulated results correspond well with measurements. Results from a bladeloss simulation are presented to exemplify the versatility of the developed code.

  • 3.
    Ashwear, Nasseradeen
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Natural frequencies describe the pre-stress in tensegrity structures2014In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 136, p. 162-171Article in journal (Refereed)
    Abstract [en]

    This paper investigates the effect of pre-stress level on the natural frequencies of tensegrity structures. This has been established by using Euler–Bernoulli beam elements which include the effect of the axial force on the transversal stiffness. The axial-bending coupling emphasizes the non-linear dependence of the natural frequencies on the pre-stress state. Pre-stress is seen as either synchronous, considering a variable final pre-stress design or as tuning, when increasing pre-stress is followed in a planned construction sequence. It is shown that for a certain tensegrity structure, increasing the level of pre-stress may cause the natural frequencies to rise or fall. This effect is related to whether the structural behavior can be seen as compression or tension dominant. Vanishing of the lowest natural frequency of the system is shown to be related to the critical buckling load of one or several compressed components. Modes of vibration show that when the force in the compressed components approaches any type of critical buckling load, this results in lower vibration frequencies. The methods in this study can be used to plan the tuning of the considered tensegrity structure towards the design level of pre-stress, and as health monitoring tools.

  • 4.
    Balieu, Romain
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Lauro, F.
    Bennani, B.
    Matsumoto, T.
    Mottola, E.
    Non-associated viscoplasticity coupled with an integral-type nonlocal damage model for mineral filled semi-crystalline polymers2014In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 134, p. 18-31Article in journal (Refereed)
    Abstract [en]

    A non-associated viscoplastic model coupled with nonlocal damage under finite strain framework is developed to simulate the non-isochoric deformation and the damage process exhibiting strain-softening of a 20% mineral filled semi-crystalline polymer. The logarithmic spin tensor properties linking the Eulerian Hencky strain with the Cauchy stress is used thanks to hypoelasticity assuming the additive decomposition of the stretching into elastic and viscoplastic parts. The constitutive model with its nonlocal formulation is implemented in an efficient manner in a commercial implicit finite element code. The proposed model exhibits mesh-independent responses and is in agreement with strain evolution observed experimentally.

  • 5.
    Battini, Jean-Marc
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Nguyen, Q. H.
    Hjiaj, M.
    Non-linear finite element analysis of composite beams with interlayer slips2009In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 87, no 13-14, p. 904-912Article in journal (Refereed)
    Abstract [en]

    This article presents a new non-linear finite element formulation for the analysis of two-layer composite plane beams with interlayer slips. The element is based on the corotational method. The main interest of this approach is that different linear elements can be automatically transformed to non-linear ones. To avoid curvature locking that may occur for low order element(s). a local linear formulation based on the exact stiffness matrix is used, Five numerical applications are presented in order to assess the performance of the formulation.

  • 6.
    Bhatti, Ayjwat Awais
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Barsoum, Zuheir
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Khurshid, Mansoor
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Development of a finite element simulation framework for the prediction of residual stresses in large welded structures2014In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 133, p. 1-11Article in journal (Refereed)
    Abstract [en]

    In this study a framework for efficient prediction of residual stresses in large welded structure is proposed. For this purpose different finite element simulation approaches available in literature are implemented on a large bogie beam structure. Among all approaches rapid dumping approach used minimum computational time and also it showed qualitatively good agreement with X-ray diffraction measurements for welding residual stresses. Moreover, gradual weld bead deposition approach predicted more accurate results when compared with the experimental measurements and other approaches. Also, by using substructuring approach the computational time is significantly reduced with an acceptable accuracy of predicted welding residual stresses.

  • 7.
    Chhang, Sophie
    et al.
    KTH.
    Sansour, C.
    Hjiaj, M.
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    An energy-momentum co-rotational formulation for nonlinear dynamics of planar beams2017In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 187, p. 50-63Article in journal (Refereed)
    Abstract [en]

    This article presents an energy-momentum integration scheme for the nonlinear dynamic analysis of planar Euler-Bernoulli beams. The co-rotational approach is adopted to describe the kinematics of the beam and Hermitian functions are used to interpolate the local transverse displacements. In this paper, the same kinematic description is used to derive both the elastic and the inertia terms. The classical midpoint rule is used to integrate the dynamic equations. The central idea, to ensure energy and momenta conservation, is to apply the classical midpoint rule to both the kinematic and the strain quantities. This idea, developed by one of the authors in previous work, is applied here in the context of the co-rotational formulation to the first time. By doing so, we circumvent the nonlinear geometric equations relating the displacement to the strain which is the origin of many numerical difficulties. It is rigorously shown that the proposed method conserves the total energy of the system and, in absence of external loads, the linear and angular momenta remain constant. The accuracy and stability of the proposed algorithm, especially in long term dynamics with a very large number of time steps, is assessed through four numerical examples.

  • 8.
    Chhang, Sophy
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design. Université Bretagne Loire, France.
    Sansour, Carlo
    Hjiaj, Mohammed
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    An energy-momentum co-rotational formulation for nonlinear dynamics of planar beams2017In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 187, p. 50-63Article in journal (Refereed)
    Abstract [en]

    This article presents an energy-momentum integration scheme for the nonlinear dynamic analysis of planar Euler-Bernoulli beams. The co-rotational approach is adopted to describe the kinematics of the beam and Hermitian functions are used to interpolate the local transverse displacements. In this paper, the same kinematic description is used to derive both the elastic and the inertia terms. The classical midpoint rule is used to integrate the dynamic equations. The central idea, to ensure energy and momenta conservation, is to apply the classical midpoint rule to both the kinematic and the strain quantities. This idea, developed by one of the authors in previous work, is applied here in the context of the co-rotational formulation to the first time. By doing so, we circumvent the nonlinear geometric equations relating the displacement to the strain which is the origin of many numerical difficulties. It is rigorously shown that the proposed method conserves the total energy of the system and, in absence of external loads, the linear and angular momenta remain constant. The accuracy and stability of the proposed algorithm, especially in long term dynamics with a very large number of time steps, is assessed through four numerical examples.

  • 9. Eriksson, A.
    On a thin shell element for non-linear analysis, based on the isoparametric concept1992In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 42, no 6, p. 927-939Article in journal (Refereed)
    Abstract [en]

    This paper discusses a finite element method model for the large displacement, moderate strain analysis of thin shells. The model is based on an 'adapted' reference configuration for a displaced element, separating the displacements into rigid body displacements and strain-producing deformations. A strategy is developed, making use of the isoparametric concept for both the choice of reference configuration and in the element formulation. This makes the use of arbitrarily shaped elements possible. The model is shown to give accurate results for a range of relevant problems. Some problems in the general application of this type of model are discussed. © 1992.

  • 10. Eriksson, A.
    On a thin shell element for non-linear analysis, based on the isoparametric concept1992In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 42, no 6, p. 927-939Article in journal (Refereed)
    Abstract [en]

    This paper discusses a finite element method model for the large displacement, moderate strain analysis of thin shells. The model is based on an 'adapted' reference configuration for a displaced element, separating the displacements into rigid body displacements and strain-producing deformations. A strategy is developed, making use of the isoparametric concept for both the choice of reference configuration and in the element formulation. This makes the use of arbitrarily shaped elements possible. The model is shown to give accurate results for a range of relevant problems. Some problems in the general application of this type of model are discussed. © 1992.

  • 11. Eriksson, A.
    On accurate descriptions for primary and secondary paths in equilibrium problems1992In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 44, no 1-2, p. 229-242Article in journal (Refereed)
    Abstract [en]

    The paper describes how several procedures, based on ideas and expressions from the analytical elastic stability theory, have been introduced as numerical tools in a general finite element program for geometrically non-linear structural analysis. Derivatives of the tangential stiffness matrix are utilized for improved predictions in the step-wise solution of equilibrium states, for identification of critical points and for accurate descriptions of initial post-bifurcation behaviour. The methods are used in a general solution algorithm, based on a parameterizing component formulation. For some element types, analytical expressions for these derivatives can be developed. The corresponding numerical approximations, needed in other element types, are also discussed. Other practical details in the numerical implementation are given. Two numerical frame examples, showing different types of limit and bifurcation behaviours, are used to discuss the numerical properties of the methods. © 1992.

  • 12. Eriksson, A.
    On accurate descriptions for primary and secondary paths in equilibrium problems1992In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 44, no 1-2, p. 229-242Article in journal (Refereed)
    Abstract [en]

    The paper describes how several procedures, based on ideas and expressions from the analytical elastic stability theory, have been introduced as numerical tools in a general finite element program for geometrically non-linear structural analysis. Derivatives of the tangential stiffness matrix are utilized for improved predictions in the step-wise solution of equilibrium states, for identification of critical points and for accurate descriptions of initial post-bifurcation behaviour. The methods are used in a general solution algorithm, based on a parameterizing component formulation. For some element types, analytical expressions for these derivatives can be developed. The corresponding numerical approximations, needed in other element types, are also discussed. Other practical details in the numerical implementation are given. Two numerical frame examples, showing different types of limit and bifurcation behaviours, are used to discuss the numerical properties of the methods. © 1992.

  • 13. Eriksson, A.
    et al.
    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.

  • 14. Eriksson, A.
    et al.
    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.

  • 15. Eriksson, A.
    et al.
    Pacoste, C.
    Symbolic software tools in the development of finite elements1999In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 72, no 4, p. 579-593Article in journal (Refereed)
    Abstract [en]

    Symbolic software has been used in a number of projects concerned with the development of finite element procedures, primarily aiming at complex, i.e. interacting and higher order instabilities, where high accuracy in formulations is required. The symbolic tools improve the efficiency and documentation of the developed procedures, in order to facilitate comparisons between different element assumptions. Beam formulations for plane and space models were developed, in total displacement and co-rotational contexts, respectively. Symbolic derivation allowed analytical verification of equivalence between certain formulations within these two contexts. Treatment of finite space rotations, based on the rotational vector makes the history-less treatment of rotations easier, which is needed in the evaluation of critical equilibrium subsets in higher-dimensional parameter space. A co-rotational viewpoint, where local element displacements can be obtained from global variables in a systematic manner, allowed different element expressions in a common framework. Different simple, linear elements have been tested with respect to computational efficiency. A field consistence approach was used to develop highly accurate beam and plane stress elements. The common element formulations, based on the matrix multiplications BTDB, is often inefficient, due to the large number of operations needed in the matrix product. Other formulations, based on an analytical integration and differentiation of the strain energy, producing explicit expressions for the stiffness terms, were considerably more efficient for certain elements.

  • 16.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Constraint paths in non-linear structural optimization2014In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 140, p. 39-47Article in journal (Refereed)
    Abstract [en]

    Optimization of significantly non-linear structures is a demanding task. The paper discusses how boundaries of the feasible region can be followed as generalized equilibrium paths in parametric space, reflecting engineering demands on stiffness, strains and stability. Solutions on the constraint paths are then evaluated with respect to any chosen objective function. For few design parameters, this approach is efficient and robust. This is demonstrated for a pre-stressed pressurized membrane of three parameters, showing several constraint paths for the problem, and indicating how these are used in optimization. The view is often closer to engineering design analyses than the mathematical optimization settings, which often has problems in handling stability constraints.

  • 17.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    On a thin shell element for non-linear analysis, based on the isoparametric concept1992In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 42, no 6, p. 927-939Article in journal (Refereed)
    Abstract [en]

    This paper discusses a finite element method model for the large displacement, moderate strain analysis of thin shells. The model is based on an 'adapted' reference configuration for a displaced element, separating the displacements into rigid body displacements and strain-producing deformations. A strategy is developed, making use of the isoparametric concept for both the choice of reference configuration and in the element formulation. This makes the use of arbitrarily shaped elements possible. The model is shown to give accurate results for a range of relevant problems. Some problems in the general application of this type of model are discussed. © 1992.

  • 18.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    On accurate descriptions for primary and secondary paths in equilibrium problems1992In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 44, no 1-2, p. 229-242Article in journal (Refereed)
    Abstract [en]

    The paper describes how several procedures, based on ideas and expressions from the analytical elastic stability theory, have been introduced as numerical tools in a general finite element program for geometrically non-linear structural analysis. Derivatives of the tangential stiffness matrix are utilized for improved predictions in the step-wise solution of equilibrium states, for identification of critical points and for accurate descriptions of initial post-bifurcation behaviour. The methods are used in a general solution algorithm, based on a parameterizing component formulation. For some element types, analytical expressions for these derivatives can be developed. The corresponding numerical approximations, needed in other element types, are also discussed. Other practical details in the numerical implementation are given. Two numerical frame examples, showing different types of limit and bifurcation behaviours, are used to discuss the numerical properties of the methods. © 1992.

  • 19.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Temporal finite elements for target control dynamics of mechanisms2007In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 85, no 17-18, p. 1399-1408Article in journal (Refereed)
    Abstract [en]

    This paper discusses a temporal finite element description in the analysis of dynamics of mechanical systems, with a special emphasis on problems where target control is desired. This is defined as a situation where forces are sought for the movement of a structure from an initial to one or more specified target states. The primary applications lie in robotics and in bio-mechanical forward simulations of musculoskeletal systems. A temporal discretization of the movement and forces is introduced. By interpolating simultaneously displacements and velocities in the spatial discrete degrees of freedom, a collocation over the time interval can be used to decide the necessary system. The needed control can be optimized for chosen criteria on the integrated force components. The temporal interpolation of control forces and discrete displacements introduces a degree of continuity in the obtained results. The viewpoint allows variation of many aspects of problem formulation, and leads to efficient solutions for systems of high complexity but moderate size.

  • 20.
    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.

  • 21.
    Eriksson, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Nordmark, Arne
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Activation dynamics in the optimization of targeted movements2011In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 89, no 11-12, p. 968-976Article in journal (Refereed)
    Abstract [en]

    Human movements, and their underlying muscular recruitment strategies, can be studied in several ways. In order to increase the understanding of human movement planning strategies, the movement problem is here seen as a boundary value problem for a mechanism with prescribed initial and final configurations. The time variations of a set of control actuator forces are supposed to fulfil some optimality criterion while creating this motion. The boundary value problem is discretized by temporal finite element interpolation, where the discrete variables are seen in an optimization context. The present work focusses on the introduction of the activation dynamics of the actuators, introducing a delay in the force production from the stimulation variables. The choice of interpolations of the variables is discussed in the light of the optimization setting. Examples show aspects of the results obtained for different assumptions. It is concluded that the formulation gives a good basis for further improvement of muscular force production models in an optimal movement setting.

  • 22.
    Eriksson, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Nordmark, Arne
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Non-unique response of Mooney-Rivlin model in bi-axial membrane stress2014In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 144, p. 12-22Article in journal (Refereed)
    Abstract [en]

    The commonly used two-parameter Mooney-Rivlin incompressible hyper-elastic material model can show non-intuitive responses under certain conditions. This paper shows that critical states with non-unique responses occur at least at very specific bi-axial stress states. This can happen for cases where the constant related to the second invariant of strain is positive, but not for the case with this constant equal to zero (the Neo-Hookean case). The dependence of the instabilities on the ratio between the two constitutive constants is shown by evaluated fold lines. The instability is shown to be related to the imposed boundary conditions. An analytical treatment of the problem shows that dynamic edge effects correspond to the static instability.

  • 23.
    Eriksson, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Nordmark, Arne
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Patil, Amit
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Zhou, Yang
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Parametric stability investigations for hydro-statically loaded membranes2016In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 174, p. 33-41Article in journal (Refereed)
    Abstract [en]

    This paper discusses instabilities occurring in thin pressurized membranes, important in biological as well as in engineering contexts. The membranes are represented by only their in-plane stress components, for which an incompressible isotropic hyper-elastic behavior can be assumed. A hydro-static pressurization can give instabilities in the form of limit points with respect to a loading parameter, but also bifurcations, and wrinkling. The hyper-elastic material model itself can also, under some circumstances, lead to a bifurcation situation. The instability situations can be included as constraints in a structural optimization. The paper discusses the formulation, the solution methods and some relevant instability situations. Numerical examples considering the pressurization of a flat and a cylindrical pre-stressed membrane illustrate some aspects of instability.

  • 24.
    Johansson, christoffer
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Pacoste, Costin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Closed-form solution for the mode superposition analysis of the vibration in multi-span beam bridges caused by concentrated moving loads2013In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 119, p. 85-94Article in journal (Refereed)
    Abstract [en]

    In this paper, a closed-form solution for evaluating the dynamical behavior of a general multi-span Bernoulli-Euler beam is derived. The natural frequencies of vibration and corresponding mode shapes are obtained by applying the boundary conditions to the characteristic function of a beam. A Laplace transformation is applied to the governing differential equation which is then solved for each normal mode in the frequency domain. The main contribution of this paper is to provide a closed-form solution for the vibration of continuous stepped beams under constant moving loads. Several numerical examples are included.

  • 25.
    Kulachenko, Artem
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Gradin, Per
    Koivurova, Hannu
    Modelling the dynamical behaviour of a paper web. Part I2007In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 85, no 3-4, p. 131-147Article in journal (Refereed)
    Abstract [en]

    A new shell element has been proposed for geometrically non-linear, finite element analyses of axially moving paper web. Web instability problems of paper travelling in a printing system, such as wrinkling and fluttering, pose special challenges in the numerical analyses. For examples, theme are finite bending stiffness (as opposed to membrane), orthotropy, and non-uniform distributions of mechanical and hygro-properties (in different length scales). The new formulation has accounted for paper transport velocity and paper bending stiffness based on a mixed -1-agrangian-Eulerian description of the motion. A natural coordinate system has been employed in the analytical and finite element formulations. Benchmarking with different finite elements in various tests showed that the proposed element is indeed more stable and reliable for the chosen application than existing elements. The usability of the shell element has been successfully demonstrated by two example p:,-oblems: wrinkling of stretched isotropic and orthotropic membranes, and the vibration of a web showing a speedtensioning effect above a critical web transport velocity.

  • 26.
    Kulachenko, Artem
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Gradin, Per
    Kolvurova, Hannu
    Modelling the dynamical behaviour of a paper web. Part II2007In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 85, no 3-4, p. 148-157Article in journal (Refereed)
    Abstract [en]

    In this paper, a finite element procedure is used to study the dynamic behaviour of a paper web in a free span between two rollers, including effects of transport velocity and surrounding air. The paper web is modelled as a three-dimensional orthotropic structure. The influence of air is accounted for by utilizing fluid-solid interaction analyses based on acoustic theory. The contribution of transport velocity is included through gyroscopic matrices and forces. The structural response on harmonic excitations has been studied using linear and non-linear models. Results show that air significantly reduces eigenfrequencies of the web. So called "edge-flutter" is nothing but the result of skew tension profile. Excessive web vibration can be eliminated by adjusting the web tension.

  • 27.
    Le, Thanh-Nam
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Université Européenne de Bretagne, France.
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Hjiaj, M.
    Université Européenne de Bretagne, France.
    Corotational formulation for nonlinear dynamics of beams with arbitrary thin-walled open cross-sections2014In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 134, p. 112-127Article in journal (Refereed)
    Abstract [en]

    A new consistent corotational formulation for nonlinear dynamics of beams with arbitrary thin-walled cross-section is presented. The novelty is that the warping deformations and the eccentricity of the shear center are fully taken into account. Therefore, additional terms are introduced in the expressions of the inertia force vector and the tangent dynamic matrix. Their contribution is then investigated considering several numerical examples. Besides, the element has seven degrees of freedom at each node and cubic shape functions are used to interpolate local transverse displacements and axial rotations. The formulation's accuracy is assessed considering five examples with comparisons against 3D-solid solutions.

  • 28.
    Liljencrantz, Axel
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges.
    Olofsson, Per
    Implementing bridge weigh-in-motion for railway traffic2007In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 85, no 02-jan, p. 80-88Article in journal (Refereed)
    Abstract [en]

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

  • 29. Novak, M.
    et al.
    Birgisson, Björn
    Roque, R.
    Near-surface stress states in flexible pavements using measured radial tire contact stresses and ADINA2003In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 81, no 11-aug, p. 859-870Article in journal (Refereed)
    Abstract [en]

    The finite element code ADINA was used to identify the three-dimensional stress states in a typical flexible pavement configuration, resulting from measured radial tire contact stresses. The predictions show that measured radial tire contact stresses result in stress states being both larger in magnitude and more focused near the surface than those obtained from traditional uniform vertical loading conditions. In terms of effects of possible pavement damage mechanisms, predicted high near-surface shear stresses may be a part of an explanation for near-surface rutting failure modes, as supported by near-surface slip planes seen in the field.

  • 30.
    Rumpler, Romain
    et al.
    Conservatoire National des Arts et Métiers (Cnam).
    Legay, Antoine
    Deü, Jean-François
    Performance of a restrained-interface substructuring FE model for reduction of structural-acoustic problems with poroelastic damping2011In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 89, no 23-24, p. 2233-2248Article in journal (Refereed)
    Abstract [en]

    This work deals with numerical computation of structural-acoustic applications including dissipative interfaces, in the context of structure-borne noise reduction. It focuses on the need to propose efficient solution strategies for costly finite element modelling. As such, a restrained-interface component mode synthesis is applied to the conservative parts of structural-acoustic applications. The method description being general and computational-oriented, it is straightforwardly applicable to a wide range of problems. The aim is to establish the efficiency as well as the limitations in the use of such a reduced model for harmonic solutions to dissipative structural-acoustic applications including 3D modelling of porous media.

  • 31. Suleman, A.
    et al.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Topping, B.H.V.
    Mota-Soares, C.A.
    Computational structures technology2007In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 85, no 17-18, p. 1281-1283Article in journal (Other academic)
  • 32.
    Wiberg, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Pacoste, Costin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Statistical screening of individual and joint effect of several modelling factors on the dynamic finite element response of a railway bridge2012In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 106, p. 91-104Article in journal (Refereed)
    Abstract [en]

    More accurate dynamic analysis of bridges is preferred instead of using the dynamic amplification factors in design codes to estimate the dynamic load effects. Additionally, the potentials of statistical methods are often overlooked and seldom used among structural engineers. However, for bridge engineers the parametric studies are still conservative and the finite element (FE) model results can often be misleading. In this paper, factorial experimentation in simulating railway bridge dynamics was exemplified. A two-level (2n) fractional factorial design was proposed and exemplified to screen the individual and joint effect of several modelling factors on the dynamic response of a specific railway bridge. The statistical theory proved to be relevant and meaningful, easy to implement but still very powerful. The concept of factorial experimentation was believed to provide the FE model updating engineer with important indications of the effects of several possible updating parameters.

  • 33.
    Östlund, Sören
    et al.
    KTH, Superseded Departments, Solid Mechanics.
    Gudmundson, Peter
    KTH, Superseded Departments, Solid Mechanics.
    The Application Of Moving Finite-Elements For The Study Of Crack-Propagation In Linear Elastic Solids.1987In: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 25, no 5, p. 765-774Article in journal (Refereed)
    Abstract [en]

    Mode I crack propagation in linear elastic solids is studied by a convecting finite element mesh. The finite element formulation is briefly described. Two different approaches for the determination of the stress intensity factor K1 have been investigated, one using the COD relation to K1 and one using the dynamic G-integral. Different test problems, including stationary cracks, steady-state crack propagation and transient crack propagation, have been thoroughly examined.

1 - 33 of 33
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • 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