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  • 1.
    Afzal, Mohammad
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Lopez Arteaga, Ines
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Kari, Leif
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    An analytical calculation of the Jacobian matrix for 3D friction contact model applied to turbine blade shroud contact2016Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 177, s. 204-217Artikkel i tidsskrift (Fagfellevurdert)
    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, Skolan för teknikvetenskap (SCI), Mekanik.
    Aeroelastic FE modelling of wind turbine dynamicsInngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243Artikkel i tidsskrift (Fagfellevurdert)
    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, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Eriksson, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Natural frequencies describe the pre-stress in tensegrity structures2014Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 136, s. 162-171Artikkel i tidsskrift (Fagfellevurdert)
    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.
    Atashipour, Seyed Rasoul
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Girhammar, Ulf Arne
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Al-Emrani, Mohammad
    Chalmers tekniska högskola .
    Exact Lévy-type solutions for bending of thick laminated orthotropic plates based on 3-D elasticity and shear deformation theories2017Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 163, s. 129-151Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Exact solutions for static bending of symmetric laminated orthotropic plates with different Lévy-type boundary conditions are developed. The shear deformation plate theories of Mindlin-Reissner and Reddy as well as the three-dimensional elasticity theory are employed. Using the minimum total potential energy principle, governing equilibrium equations of laminated orthotropic plates and pertaining boundary conditions are derived. Closed-form Lévy-type solutions are obtained for the governing equations of both theories using separation of variables method and different types of classical boundary conditions, namely simply-supported, clamped and free edge, are exactly satisfied. Thereafter, 3-D elasto-static equations for orthotropic materials are solved for bending analysis of laminated plates using two different approaches. First, the method of separation of variables is utilized and an exact closed-from solution is achieved for simply-supported laminated orthotropic plates. Next, a combined Fourier-Differential Quadrature (DQ) approach is employed to present a semi-numerical solution for bending of laminated orthotropic plates with Lévy-type boundary conditions based on the three-dimensional elasticity theory. High accuracy of the presented solutions are proven and comprehensive comparative numerical results are provided and discussed. Presented comparative numerical results can serve as benchmark for investigating the correctness of new solution methods which may be established in the future.

  • 5.
    Balieu, Romain
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Lauro, F.
    Bennani, B.
    Matsumoto, T.
    Mottola, E.
    Non-associated viscoplasticity coupled with an integral-type nonlocal damage model for mineral filled semi-crystalline polymers2014Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 134, s. 18-31Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 6.
    Battini, Jean-Marc
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Nguyen, Q. H.
    Hjiaj, M.
    Non-linear finite element analysis of composite beams with interlayer slips2009Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 87, nr 13-14, s. 904-912Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 7. Bernspång, Lars
    et al.
    Samuelsson, A.
    Chalmers University of Technology.
    Kussner, M.
    Technische Hochschule Darmstadt.
    Wriggers, P.
    Technische Hochschule Darmstadt.
    The consistent strain method in finite element plasticity1995Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 54, nr 1, s. 27-33Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An algorithm for finite element analysis of problems in elastoplasticity with continuous stress and strain approximation is presented. By a global iteration procedure, equilibrium is preserved at the nodes in a weak sense, and the local constitutive relation between stresses and strains is satisfied. A high order numerical integration is used to achieve a good quality stiffness matrix and to evaluate the boundary between elastic and plastic regions in the case of partly plastic elements.

  • 8.
    Bhatti, Ayjwat Awais
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Barsoum, Zuheir
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Khurshid, Mansoor
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Development of a finite element simulation framework for the prediction of residual stresses in large welded structures2014Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 133, s. 1-11Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 9.
    Chhang, Sophy
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap. Structural Engineering Research Group/LGCGM, INSA de Rennes, Université Bretagne Loire, 20 avenue des Buttes de Coësmes, CS 70839, 35708 Rennes Cedex 7, France.
    Sansour, C.
    Hjiaj, M.
    Battini, Jean-Marc
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggteknik och design.
    An energy-momentum co-rotational formulation for nonlinear dynamics of planar beams2017Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 187, s. 50-63Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 10. Eriksson, A.
    On a thin shell element for non-linear analysis, based on the isoparametric concept1992Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 42, nr 6, s. 927-939Artikkel i tidsskrift (Fagfellevurdert)
    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 a thin shell element for non-linear analysis, based on the isoparametric concept1992Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 42, nr 6, s. 927-939Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 12. Eriksson, A.
    On accurate descriptions for primary and secondary paths in equilibrium problems1992Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 44, nr 1-2, s. 229-242Artikkel i tidsskrift (Fagfellevurdert)
    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.
    On accurate descriptions for primary and secondary paths in equilibrium problems1992Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 44, nr 1-2, s. 229-242Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 14. Eriksson, A.
    et al.
    Kouhia, R.
    On step size adjustments in structural continuation problems1995Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 55, nr 3, s. 495-506Artikkel i tidsskrift (Fagfellevurdert)
    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.
    Kouhia, R.
    On step size adjustments in structural continuation problems1995Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 55, nr 3, s. 495-506Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 16. Eriksson, A.
    et al.
    Pacoste, C.
    Symbolic software tools in the development of finite elements1999Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 72, nr 4, s. 579-593Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 17.
    Eriksson, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Constraint paths in non-linear structural optimization2014Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 140, s. 39-47Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 18.
    Eriksson, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    On a thin shell element for non-linear analysis, based on the isoparametric concept1992Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 42, nr 6, s. 927-939Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 19.
    Eriksson, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    On accurate descriptions for primary and secondary paths in equilibrium problems1992Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 44, nr 1-2, s. 229-242Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 20.
    Eriksson, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Temporal finite elements for target control dynamics of mechanisms2007Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 85, nr 17-18, s. 1399-1408Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 21.
    Eriksson, Anders
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Kouhia, R.
    On step size adjustments in structural continuation problems1995Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 55, nr 3, s. 495-506Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 22.
    Eriksson, Anders
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Nordmark, Arne
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Activation dynamics in the optimization of targeted movements2011Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 89, nr 11-12, s. 968-976Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 23.
    Eriksson, Anders
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Nordmark, Arne
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Non-unique response of Mooney-Rivlin model in bi-axial membrane stress2014Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 144, s. 12-22Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 24.
    Eriksson, Anders
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Nordmark, Arne
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Patil, Amit
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Zhou, Yang
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Parametric stability investigations for hydro-statically loaded membranes2016Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 174, s. 33-41Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 25.
    Fritzson, Dag
    et al.
    SKF Engineering & Research Centre, Nieuwegein, The Netherlands.
    Fritzson, Peter
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Viklund, Lars
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Herber, Johan
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Object-Oriented Mathematical Modelling – Applied to Machine Elements1994Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 51, nr 3, s. 241-253Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Machine element analysis has a goal of describing function and other aspects of machine elements in a theoretical form. This paper shows how ideas from object-oriented modelling can be applied to machine element analysis. The models thus obtained are both easier to understand, better structured, and allow a higher degree of re-use than conventional models. An object-oriented model description is natural and suitable for machine element analysis. As a realistic example an equational model of rolling bearings is presented. The structure of the model is general, and applies to many types of rolling bearings. The model and one solution require approximately 200 + 200 equations. The model is extensible, e.g. simple submodels of detailed properties can be made more complex without altering the overall structure. The example model has been implemented in a language of our own design, ObjectMath (Object-oriented Mathematical language for scientific computing). Using ObjectMath, it is possible to model classes of equation objects, to support multiple and single inheritance of equations, to support composition of equations, and to solve systems of equations. Algebraic transformations can conveniently be done since ObjectMath models are translated into the Mathematica computer algebra language. When necessary, equations can be transformed to C++ code for efficient numerical solution. The re-use of equations through inheritance reduced the size of the model by a factor of two, compared to a direct representation of the model in the Mathematica computer algebra language.

  • 26.
    Girhammar, Ulf Arne
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Atashipour, Seyed Rasoul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Analysis of shear deflections of deep composite box-type of beams using different shear deformation models2015Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 155, s. 42-53Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The deflection of deep box-type elements due to shear deformations is treated. A closed-form expression for the shear correction factor is derived by using an energy approach. The high accuracy and reliability of the developed procedure is demonstrated by comparing its results with accurate 3-D finite element results and also with the results of the conventional theories of Timoshenko with constant shear coefficient and of Reddy–Bickford applied to this kind of cross-section. A comprehensive and comparative parametric study is presented to investigate the effects of various mechanical properties and geometric dimensions for the different models. Unlike the higher-order shear deformation theories, which are accurate only for beams with rectangular cross-sections, there is a very good agreement between the results of the proposed method and the 3-D FE model. Clearly, the proposed energy method is applicable to more complicated cross-sections, including those with abrupt changes in the geometry, e.g. due to holes.

  • 27.
    Johannesson, Björn
    et al.
    Technical University of Denmark, Denmark.
    Hosokawa, Yoshifumi
    Taiheiyo Cement Corporation, Japan .
    Yamada, Kazuo
    Taiheiyo Cement Corporation, Japan .
    Numerical Calculations of the Effect of Moisture Content and Moisture Flow on Ionic Multi-Species Diffusion in the Pore Solution of Porous Materials2009Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 87, nr 1-2, s. 39-46Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method to analyse and calculate concentration profiles of different types of ions in the pore solution of porous materials such as concrete subjected to external wetting and drying is described. The equations in use have a solid theoretical meaning and are derived from a porous media technique, which is a special branch of the more general mixture theory. The effect of chemical action is ignored making the presented model suitable to be implemented into codes dealing solely with chemical equilibrium. The coupled set of equations for diffusion of ionic species, the internal electrical potential and the moisture content are solved simultaneously using an implicit finite element technique, in order to avoid numerical oscillations. Important verified material behaviours are included in the model, such as the convective flow of ionic species due to moisture flow, the effect of the moisture content on the ionic diffusion resistance in the pore solution of the porous material. The Gauss’ law is included in the model in order to be able to calculate the electrical potential which develops due to small deviations from total charge neutrality among the ionic species in the pore solution. The correctness of the model should be judged from the assumptions made when developing the balance laws and the constitutive equations and the assumptions made in obtaining a working numerical calculation scheme.

  • 28.
    Johansson, christoffer
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Pacoste, Costin
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Closed-form solution for the mode superposition analysis of the vibration in multi-span beam bridges caused by concentrated moving loads2013Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 119, s. 85-94Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 29. Karbassi, A.
    et al.
    Mohebi, B.
    Rezaee, Shaliz
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Lestuzzi, P.
    Damage prediction for regular reinforced concrete buildings using the decision tree algorithm2014Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 130, s. 46-56Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To overcome the problem of outlier data in the regression analysis for numerical-based damage spectra, the C4.5 decision tree learning algorithm is used to predict damage in reinforced concrete buildings in future earthquake scenarios. Reinforced concrete buildings are modelled as single-degree-of-freedom systems and various time-history nonlinear analyses are performed to create a dataset of damage indices. Subsequently, two decision trees are trained using the qualitative interpretations of those indices. The first decision tree determines whether damage occurs in an RC building. Consequently, the second decision tree predicts the severity of damage as repairable, beyond repair, or collapse.

  • 30.
    Kulachenko, Artem
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Gradin, Per
    Koivurova, Hannu
    Modelling the dynamical behaviour of a paper web. Part I2007Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 85, nr 3-4, s. 131-147Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 31.
    Kulachenko, Artem
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Gradin, Per
    Kolvurova, Hannu
    Modelling the dynamical behaviour of a paper web. Part II2007Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 85, nr 3-4, s. 148-157Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 32.
    Le, Thanh-Nam
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad. Université Européenne de Bretagne, France.
    Battini, Jean-Marc
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Hjiaj, M.
    Université Européenne de Bretagne, France.
    Corotational formulation for nonlinear dynamics of beams with arbitrary thin-walled open cross-sections2014Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 134, s. 112-127Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 33.
    Liljencrantz, Axel
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Olofsson, Per
    Implementing bridge weigh-in-motion for railway traffic2007Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 85, nr 02-jan, s. 80-88Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 34.
    Lindgren, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Improvements of the program "A versatile two-dimensional mesh generator with automatic bandwidth reduction"1987Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 25, nr 4, s. 637-638Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Some simple modifications of the Fortran-code for the mesh generator of L. L. Durocher and A. Gasper are described. The changes make it possible to exclude five large data arrays and at the same time speed up the calculations somewhat

  • 35.
    Mackerle, Jaroslav
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära.
    FEM and BEM in the context of information retrieval2002Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 80, nr 20-21, s. 1595-1604Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Numerical techniques such as, first of all, the finite element and boundary element methods are frequently used today in research as well as in many industry applications. The output of finite element and boundary element literature and development of software, has been growing during last three decades. Today, it is almost impossible to be up-to-date with all the relevant information. At present, we have an excess of information--the term "information fatigue syndrome" will soon be a recognized medical condition. The author presents, by means of information from his database, the progress of both numerical techniques in their theoretical developments and practical usage for the period of last 30 years. The topics included: finite element and boundary element literature and software with emphasis on structural and solid mechanics. Some pointers for classical, printed, and for modern, on-line, information retrieval are given. © 2002 Elsevier Science Ltd. All rights reserved.

  • 36.
    Massih, A.R.
    et al.
    ABB Atom AB.
    Isaksson, P.
    Luleå tekniska universitet.
    Ståhle, Per
    Luleå tekniska universitet.
    Modelling the behaviour of a control-element blade during irradiation1997Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 64, nr 5-6, s. 1113-1127Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The control-rod elements in a boiling-water reactor contain natural boron carbide (B4C) powder, used as neutron-absorber material and clad in stainless-steel blades. During in-reactor service, the internal production of helium gas and point defects in neutron-irradiated boron carbide cause swelling which can induce significant contact stresses in the blade causing, eventually, stress-corrosion cracking of the blades. In this work, a finite-element analysis of a control-rod blade consisting of B4C powder and stainless-steel cladding has been performed using ADINA. An algorithm for the finite-element calculation of a porous material such as B4C powder has been developed and which models both swelling and consolidation behaviour of B4C powder. The Drucker-Prager constitutive law has been used to model the consolidation effect. The model has been verified with an analytical solution for a simple geometry. A number of cases with B4C powder in contact with stainless steel and using the actual blade design have been studied for which contact stresses, the displacements and the effective stresses are calculated. Finally, the model has been used to predict the deformation of the blade during irradiation under B4C swelling and irradiation-induced creep of stainless steel

  • 37. Novak, M.
    et al.
    Birgisson, Björn
    Roque, R.
    Near-surface stress states in flexible pavements using measured radial tire contact stresses and ADINA2003Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 81, nr 11-aug, s. 859-870Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 38. Olovsson, Lars
    et al.
    Nilsson, Larsgunnar
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Hållfasthetslära.
    Simonsson, Kjell
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Hållfasthetslära.
    An ALE formulation for the solution of two-dimensional metal cutting problems1999Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 72, s. 497-507Artikkel i tidsskrift (Fagfellevurdert)
  • 39.
    Olovsson, Lars
    et al.
    Swedish Defence Research Agency, Tumba, Sweden.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Unosson, Mattias
    Swedish Defence Research Agency, Tumba, Sweden.
    Shear locking reduction in eight-noded tri-linear solid finite elements2006Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 84, nr 7, s. 476-484Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new quadrature rule for eight-noded solid finite elements is suggested. The formulation reduces those locking problems associated with the classical full and selectively-reduced Gauss integration schemes and it is based on an element local coordinate system where the shear strain components are averaged in groups of four integration points. This work is mainly interesting in contexts of plasticity and explicit time integration, where low order elements often are preferable. © 2005 Elsevier Ltd. All rights reserved.

  • 40.
    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 damping2011Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 89, nr 23-24, s. 2233-2248Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 41.
    Santiago, Aldina
    et al.
    University of Coimbra.
    Silva, Luís Simões da
    University of Coimbra.
    Real, Paulo Vila
    University of Aveiro.
    Veljkovic, Milan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Numerical study of a steel sub-frame in fire2008Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 86, nr 15-16, s. 1619-1632Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Steel framed buildings are generally designed with "simple" shear-resisting connections, and lateral forces are resisted by vertical bracing and shear walls. When a beam is considered then the effects of the longitudinal restraints by the adjacent structure and the rotational restraint by the connections has to be taken into account. Because of structural interaction, the beam behaviour at elevated temperature is rather complex. This paper presents a numerical parametric study of a structural system consisting of an exposed steel beam restrained between a pair of fire protected steel columns. The structural sub-frame is modelled using 3D shell elements, thereby taking into account the effect of the local failure modes, and the realistic behaviour of the sub-frame exposed to natural fire. The numerical model accounts for the initial geometrical imperfections, non-linear temperature gradient over the cross-section, geometrical and material nonlinearity and temperature dependent material properties. Results obtained using a general Finite Element software - LUSAS and a fire dedicated software - SAFIR, are compared. The influence of following variables: beam span/depth ratio, lateral restraint, gradient temperature within the cross-section and mechanical load level is presented in the paper. The failure modes, the development of the internal forces and displacements throughout the analysis are considered to exemplify the effects of the variables considered.

  • 42. Suleman, A.
    et al.
    Eriksson, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Topping, B.H.V.
    Mota-Soares, C.A.
    Computational structures technology2007Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 85, nr 17-18, s. 1281-1283Artikkel i tidsskrift (Annet vitenskapelig)
  • 43.
    Thore, Carl-Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik. Linköpings universitet, Tekniska högskolan.
    Optimal Design of Neuro-Mechanical Oscillators2013Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 119, s. 189-202Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper concerns optimization of active mechanical systems capable of exhibiting persistent oscillatory behavior. In part inspired by biological systems possessing similar properties we refer to these systems as neuro-mechanical oscillators. The mathematical model consists of a set of nonlinear ordinary differential equations describing an actuated truss excited by a nonlinear recurrent neural network. An optimization problem is formulated with the goal of adjusting some of the parameters in the system such that when the neural network is subjected to a constant input, one of the nodes in the truss follows a prescribed trajectory in a periodic fashion. Two examples are presented to illustrate the concept, and the corresponding optimization problems are solved numerically.

  • 44.
    Torstenfelt, Bo
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling.
    An Automatic incrementation technique for Contact problems with Friction1984Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 19, nr 3, s. 393-400Artikkel i tidsskrift (Fagfellevurdert)
  • 45.
    Wettergren, Håkan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Maskinkonstruktion.
    Beam element for non-symmetric composite shafts2000Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 78, nr 4, s. 617-636Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present paper, an explicit beam element for non-symmetric thin-walled composite shafts is developed. The element is developed from the WS element which normally demands numerical integration. It allows circumferential changes of the radius but takes advantage of the fact that it is only the second term in a Fourier series expansion that has a major influence on the dynamic behaviour of the rotor. The element allows transverse shear and moreover the mass is not distributed on the centre line.

  • 46.
    Wiberg, Johan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Karoumi, Raid
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Pacoste, Costin
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Statistical screening of individual and joint effect of several modelling factors on the dynamic finite element response of a railway bridge2012Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 106, s. 91-104Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 47.
    Östlund, Sören
    et al.
    KTH, Tidigare Institutioner                               , Hållfasthetslära.
    Gudmundson, Peter
    KTH, Tidigare Institutioner                               , Hållfasthetslära.
    The Application Of Moving Finite-Elements For The Study Of Crack-Propagation In Linear Elastic Solids.1987Inngår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 25, nr 5, s. 765-774Artikkel i tidsskrift (Fagfellevurdert)
    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 - 47 of 47
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