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  • 51.
    Strömberg, Niclas
    Department of Mechanical Engineering, Linköping University, Linköping, Sweden.
    TriLab: a tool for simulating tribological systems2003In: Proceedings of the 9th International Power Transmission and Gearing Conference, New York: American Society of Mechanical Engineers , 2003, p. 1051-1056Conference paper (Refereed)
    Abstract [en]

    In this paper TriLab is presented. TriLab is a user-friendly finite element tool for simulating tribological systems. TriLab is based on a method for structural dynamic contact problems with friction and wear. The method is reviewed in the paper as well as the quasi-static formulation of frictional contact, the energy-momentum conserving approach of Simo and Tarnow, and Moreau's nonsmooth contact dynamics formulation. TriLab is easy to use and can be utilized for solving both small displacement contact, rolling contact as well as impact problems. This is demonstrated by solving a number of examples.

  • 52.
    Strömberg, Niclas
    Department of Mechanical Engineering, Linköping University, Linköping, Sweden.
    TriLab: a toolbox for tribological systems2003In: Proceedings from the Nordic MATLAB Conference 2003, Copenhagen, Denmark, 2003Conference paper (Refereed)
  • 53.
    Strömberg, Niclas
    Jönköping University, Jönköping, Sweden.
    What is the optimal shape of a snap ring?2008In: Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference (DETC2007): Volume 5: 6th International Conference on Multibody Systems, Nonlinear Dynamics, and Control, Part A, New York: American Society of Mechanical Engineers , 2008, p. 407-412Conference paper (Refereed)
    Abstract [en]

    In this paper a non-linear elastic ring is studied by using a method for contact/impact problems. The method is developed for frictional contact, impact and rolling between a two-dimensional hyperelastic body and rigid foundations. The elastic properties of the body are defined by coupling the second Piola-Kirchhoff stress to the Green-Lagrange strain via the Kirchhoff-St. Venant law. The rigid supports are described by smooth functions. By introducing the mean value impulses, these functions are utilized to formulate new contact/impact laws. The support functions appear explicitly in the variational formulation of Signorini, and implicitly in the maximal dissipation principle of Coulomb. A feature of this approach is that no search algorithm is needed. Another feature is that the normal and tangential directions of the supports are well defined The above constitutive assumptions together with the law of motion, which is written on velocity form, define the governing equations of the system. These are solved by a nonsmooth Newton method. The method is utilized to study the contact pressure between a snap ring and a rigid groove which has the shape of a perfect circle. It is obvious that if the snap ring also has the shape of a perfect circle, then the distribution of the contact pressure will be uneven. An even distribution of the contact pressure is preferable in order to improve function and increase lifetime. The question that is considered in this paper is how the shape of the ring should be designed in order to produce this type of contact pressure.

  • 54.
    Strömberg, Niclas
    et al.
    Linköping university, Linköping, Sweden.
    Johansson, Lars
    Klarbring, Anders
    A generalized standard model for contact, friction and wear1995In: Contact Mechanics: Proceedings of the 2nd Contact Mechanics International Symposium, New York: Plenum Press , 1995, p. 327-334Conference paper (Refereed)
  • 55.
    Strömberg, Niclas
    et al.
    Department of Mechanical Engineering, Division of Mechanics, Linköping Inst. of Technology, Linköping, Sweden.
    Johansson, Lars
    Department of Mechanical Engineering, Division of Mechanics, Linköping Inst. of Technology, Linköping, Sweden.
    Klarbring, Anders
    Department of Mechanical Engineering, Division of Mechanics, Linköping Inst. of Technology, Linköping, Sweden.
    Derivation and analysis of a generalized standard model for contact, friction and wear1996In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 33, no 13, p. 1817-1836Article in journal (Refereed)
    Abstract [en]

    A model for mechanical contact including friction, wear and heat generation is proposed. By defining an internal state variable for the wear process, a generalized standard model for contact, friction and wear is derived from the principle of virtual power and the fundamental laws of thermodynamics. Within the frame of the generalized standard model some specific constitutive models are presented. For instance, a free energy corresponding to an extension of Signorini's unilateral contact conditions to include the wear process at the interface and having a linear tangential compliance between the relative tangential displacement and the tangential contact traction is suggested. Furthermore, a dual pseudo-potential with a friction and wear limit criterion in agreement with Coulomb's law of friction Archard's law of wear is given. In order to study existence and uniqueness questions, this pair of free energy and dual pseudo-potential is analysed in a one point elastic quasi-static contact problem with two degrees of freedom and thermal effects neglected. The so-called rate problem is solved.

  • 56.
    Strömberg, Niclas
    et al.
    Department of Mechanical Engineering, Jönköping University, Jönköping, Sweden.
    Klarbring, Anders
    Division of Mechanics, Linköping University, Linköping, Sweden.
    Minimization of Compliance of a Linear Elastic Structure with Contact Constraints by using Sequential Linear Programming and Newton's method2008In: Proceedings of the 7th International ASMO-UK/ISSMO International Conference on Engineering Design Optimization, 2008, p. 379-386Conference paper (Refereed)
  • 57.
    Strömberg, Niclas
    et al.
    Department of Mechanical Engineering, Jönköping University, Jönköping, Sweden.
    Klarbring, Anders
    Division of Mechanics, Linköping University, Linköping, Sweden.
    Topology optimization of structures in unilateral contact2010In: Structural and multidisciplinary optimization (Print), ISSN 1615-147X, E-ISSN 1615-1488, Vol. 41, no 1, p. 57-64Article in journal (Refereed)
    Abstract [en]

    In this paper a general framework for topology optimization of structures in unilateral contact is developed. A linear elastic structure that is unilaterally constrained by rigid supports is considered. The supports are modeled by Signorini's contact conditions which in turn are treated by the augmented Lagrangian approach as well as by a smooth approximation. The latter approximation must not be confused with the well-known penalty approach. The state of the system, which is defined by the equilibrium equation and the two different contact formulations, is solved by a Newton method. The design parametrization is obtained by using the SIMP-model. The minimization of compliance for a limited value of volume is considered. The optimization problems are solved by SLP. This is done by using a nested approach where the state equations are linearized and sensitivities are calculated by the adjoint method. In order to avoid mesh-dependency the sensitivities are filtered by Sigmund's filter. The final LP-problem is solved by an interior point method that is available in Matlab. The implementation is done for a general design domain in 2D as well as in 3D by using fully integrated isoparametric elements. The implementation seems to be very efficient and robust.

  • 58.
    Strömberg, Niclas
    et al.
    Department of Mechanical Engineering, Jönköping University, Jönköping, Sweden.
    Klarbring, Anders
    Division of Mechanics, Linköping University, Linköping, Sweden.
    Topology optimization of Structures with Contact Constraints by using a Smooth Formulation and a Neested Approach2009In: Proceedings of the 8th World Congress on Structural and Multidisciplinary Optimization, International Society for Structural and Multidisciplinary Optimization , 2009Conference paper (Refereed)
    Abstract [en]

    In this paper a method for topology optimization of structures in unilateral contact is developed. A linear elastic structure that is unilateral constrained by rigid supports is considered. The supports are modeled by Signorini’s contact conditions which in turn are treated by a smooth approximation. This approximation must not be confused with the well-known penalty approach. The state of the system, which is defined by the equilibrium equations and the smooth approximation, is solved by a Newton method. The design parametrization is obtained by using the SIMP-model. The minimization of compliance for a limited value of volume is considered. The optimization problem is solved by a nested approach where the equilibrium equations are linearized and sensitivities are calculated by the adjoint method. The problem is then solved by SLP. The LP-problem is in turn solved by an interior point method that is available in Matlab. In order to avoid mesh-dependency the sensitivities are filtered by Sigmund’s filter. The method is implemented by using Matlab and Visual Fortran, where the Fortran code is linked to Matlab as mex-files. The implementation is done for a general design domain in 2D by using fully integrated isoparametric elements. The implementation seems to be very efficient and robust.

  • 59.
    Strömberg, Niclas
    et al.
    Department of Mechanical Engineering, Jönköping University, Jönköping, Sweden.
    Massana, J. F.
    Department of Mechanical Engineering, Jönköping University, Jönköping, Sweden.
    A soft contact formulation for modelling thin coatings2005In: Computer methods and experimental measurements for surface effects and contact mechanics VII / [ed] J.T.M. De Hosson, C.A. Brebbia, S.-I. Nishida, Southampton: WIT Press, 2005, p. 211-218Conference paper (Refereed)
    Abstract [en]

    Today, high-performance machine components are often improved by coatings. For instance, thin layers can increase the life-time by reducing friction and wear. An example of this is the spline joint in the suspension system of a truck. This joint, which is placed at the output of the gearbox, allows relative translation in the axial direction. In order to improve performance, this spline can be coated with a thin layer of polyamide. In such a manner, the life-time of the joint is increased by decreasing friction and wear. This type of coatings may be optimized by performing finite element contact analysis. However, when performing such an analysis, it can be difficult to obtain a good mesh due to the very thin layer. An approach to avoid this difficulty is to instead include the elastic properties of the coating in the contact formulation. Such a soft contact formulation is suggested and solved in this paper. The formulation is obtained by adding an elastic part to the free energy corresponding to Signorini’s contact conditions. In such a manner a new soft contact law is derived by taking the subdifferential of the free energy. In this law two new constitutive parameters appear. The first parameter describes the elastic response of the thin layer and the second one is taken to be equal to the thickness of the layer. In the event, when the layer is completely penetrated, hard contact is developed following a classical Lagrange formulation of Signorini.A numerical method for solving the new contact formulation is also developed. The method is obtained by following the augmented Lagrangian approach. In such a way an equivalent setting of equations is derived which in turn is solved by using a non-smooth Newton method. The method is implemented in a Matlab toolbox. The method is robust and produces accurate results. This is shown by comparing numerical results with solutions obtained by using a penalty formulation in Abaqus.

  • 60.
    Tapankov, Martin
    et al.
    School of Engineering, JTH. Research area Product Development - Simulation and Optimization, Jönköping University, Jönköping, Sweden.
    Strömberg, Niclas
    School of Engineering, JTH. Research area Product Development - Simulation and Optimization, Jönköping University, Jönköping, Sweden.
    Sampling- and SORM-based RBDO of a Knuckle Component by using Optimal Regression Models2012In: Proceedings of the 14th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference, American Institute of Aeronautics and Astronautics, 2012Conference paper (Refereed)
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