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  • 1. Christensen, XP.W
    et al.
    Klarbring, A
    Pang, J.S.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Formulation and comparison of algorithms for frictional contact problems1998In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 42, no 1, p. 145-173Article in journal (Refereed)
  • 2. Gustafsson, E
    et al.
    Hofwing, Magnus
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Simulation and Measurement of Residual Stresses in a Stress Lattice2007In: Proceedings of the the 2nd International Conference of Simulation and Modelling of Metallurgical Processes in Steelmaking, September 12-14, Austria, 2007, Leoben: ASMET , 2007, p. 285-290Conference paper (Refereed)
  • 3. Gustafsson, E
    et al.
    Hofwing, Magnus
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Simulering och mätning av restspänningar i spänningsharpor2007In: Luleå tekniska universitet, Svenska Mekanikdagar, 13-15 juni, 2007, 2007Conference paper (Other academic)
  • 4. Gustafsson, E
    et al.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Shape optimization of castings by using successive response surface methodology2008In: Structural and multidisciplinary optimization (Print), ISSN 1615-147X, E-ISSN 1615-1488, Vol. 35, no 1, p. 11-28Article in journal (Refereed)
  • 5. Gustafsson, E
    et al.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Structural optimization of castings by using ABAQUS and Matlab2005In: Proceedings of the Seminar on Competent Design by Castings (GJUTDESIGN -2005), June 13-14, Espoo, FINLAND,, 2005Conference paper (Refereed)
  • 6. Gustafsson, E.
    et al.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Structural optimization of castings by using Abaqus and Matlab2005In: Proceedings of the Abaqus World Users' Conference, May 18-20, Stockholm, Sweden, 2005., 2005Conference paper (Refereed)
  • 7.
    Gustafsson, E
    et al.
    Jönköping University.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Strukturoptimering av gjutgods med hänsyn tagen till gjutspänningar2007In: Luleå tekniska universitet, Svenska Mekanikdagar, 13-15 juni, 2007, 2007Conference paper (Other academic)
  • 8. Gustafsson, E
    et al.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Successive Response Surface Methodology by using Neural Networks2007In: Proceedings of the 7th World Congress on Structural and Multidisciplinary Optimization, May 21-25, Seoul, Korea, 2007Conference paper (Refereed)
  • 9.
    Gustafsson, Erik
    et al.
    Väderstad-Verken AB.
    Hofwing, Magnus
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Residual stresses in a stress lattice - experiments and finite element simulations2009In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 209, no 9, p. 4320-4328Article in journal (Refereed)
    Abstract [en]

    In this work residual stresses in a stress lattice are studied. The residual stresses are both measured and simulated. The stress lattice is casted of low alloyed grey cast iron. In fact, nine similar lattices are casted and measured. The geometry of the lattice consists of three sections in parallel. The diameter of the two outer sections are thinner than the section in the middle. When the stress lattice cools down, this difference in geometry yields that the outer sections start to solidify and contract before the section in the middle. Finally, an equilibrium state, with tensile stresses in the middle and compressive stresses in the outer sections, is reached. The thermo-mechanical simulation of the experiments is performed by using Abaqus. The thermo-mechanical solidification is assumed to be uncoupled. First a thermal analysis, where the lattice is cooled down to room temperature, is performed. Latent heat is included in the analysis by letting the fraction of solid be a linear function of the temperature in the mushy zone. After the thermal analysis a quasi-static mechanical analysis is performed where the temperature history is considered to be the external force. A rate independent J2-plasticity model with isotropic hardening is considered, where the material data depend on the temperature. Tensile tests are performed at room temperature, 200°C, 400°C, 600°C and 800°C in order to evaluate the Young´s modulus, the yield strength and the hardening accurate. In addition, the thermal expansion coefficient is evaluated for temperatures between room temperature and 1000°C. The state of residual stresses is measured by cutting the mid section or the outer section. The corresponding elastic spring-back reveals the state of residual stresses. The measured stresses are compared to the numerical simulations. The simulations show good agreement with the results from the experiments.

  • 10.
    Hofwing, Magnus
    et al.
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    D-optimality of non-regular design spaces by using a Bayesian modification and a hybrid method2010In: Structural and multidisciplinary optimization (Print), ISSN 1615-147X, E-ISSN 1615-1488, Vol. 42, no 1, p. 73-88Article in journal (Refereed)
    Abstract [en]

    In this work a hybrid method of a genetic algorithm  and sequential linear programming is suggested to obtain a D-optimal design of experiments. Regular as well as non-regular design spaces are considered. A D-optimal design of experiments maximizes the determinant of the information matrix, which appears in the normal equation. It is known that D-optimal design of experiments sometimes include duplicate design points. This is, of course, not preferable since duplicates do not add any new information to the response surface approximation and the computational effort is therefore wasted. In this work a Bayesian modification, where higher order terms are added to the response surface approximation, is used in case of duplicates in the design of experiments. In such manner, the draw-back with duplicates might be eliminated. The D-optimal problem, which is obtained by using the Bayesian modification, is then solved by a hybrid method. A hybrid method of a genetic algorithm that generates a starting point for sequential linear programming is developed. The genetic algorithm performs genetic operators such as cross-over and mutation on a binary version of the design of experiments, while the real valued version is used to evaluate the fitness. Next, by taking the gradient of the objective, a LP-problem is formulated which is solved by an interior point method that is available in Matlab. This is repeated in a sequence until convergence is reached. The hybrid method is tested for four numerical examples. Results from the numerical examples show a very robust convergence to a global optimum. Furthermore, the results show that the problem with duplicates is eliminated by using the Bayesian modification.

  • 11.
    Hofwing, Magnus
    et al.
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    D-optimality of non-regular design spaces by using a Genetic Algorithm2009In: proceedings of the 8th World Congress on Structural and Multidisciplinary Optimization, June 1-5, Lisbon, Portugal, 2009, 2009Conference paper (Refereed)
  • 12.
    Hofwing, Magnus
    et al.
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Robustness of residual stresses in castings and an improved process window2009In: proceedings of the 35th Design Automation Conference, August 30-September 2, San Diego, USA 2009., 2009Conference paper (Refereed)
    Abstract [en]

    In this work the robustness of residual stresses in finite element simulations with respect to deviations in mechanical parameters in castings is evaluated. Young's modulus, the thermal expansion coefficient and the hardening are the studied parameters. A 2D finite element model of a stress lattice is used. The robustness is evaluated by comparing purely finite element based Monte Carlo simulations and Monte Carlo simulations based on linear and quadratic response surfaces. Young's modulus, the thermal expansion coefficient and the hardening are assumed to be normal distributed with a standard deviation that is 10% of their nominal value at different temperatures. In this work an improved process window is also suggested to show the robustness graphically. By using this window it is concluded that least robustness is obtained for high hardening values in combination to deviations in Young's modulus and the thermal expansion coefficient. It is also concluded that quadratic response surface based Monte Carlo simulations substitute finite element based Monte Carlo simulations satisfactory. Furthermore, the standard deviation of the responses are evaluated analytically by using the Gauss formula, and are compared to results from Monte Carlo simulations. The analytical solutions are accurate as long as the Gauss formula is not utilized close to a stationary point.

  • 13.
    Hofwing, Magnus
    et al.
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Simulation of residual stresses in stamping dies2008In: Proceedings of the IDDRG 2008 Conference: Best in class stamping, 16-18 June 2008, Olofström, Sweden / [ed] Nader Asnafi, Olofström: Industriellt utvecklingscentrum i Olofström AB , 2008, p. 765-776Conference paper (Refereed)
    Abstract [en]

    In the past stamping dies have in principle been designed by rules of thumb and intuition. As the sheet metals in the vehicle industry have got increased mechanical properties in recent years the demands on the stamping dies have increased. For instance increase in stiffness is desirable in order to better control spring-back. The most simple way to satisfy this new demand would be to make the stamping dies even more heavy in order to be able to handle the new sheet metals. Since there are restrictions of the weight of the stamping dies in the stamping machines and since the overhead cranes usually have reached the limit of what they can handle, this is not a desirable solution. Another approach, in order to increase the stiffness without increasing the weight is to use topology optimization. Recently in a master thesis at Volvo Car Corporation a conceptual design of a stamping die has been done by topology optimization. In that work no consideration is taken to the fact that the stamping die is casted. Casting implies that residual stresses possibly are produced during the solidification and cooling process. The residual stresses might affect the fatigue life and the risk of failure of the stamping die.

    In this work the residual stress state after casting is analyzed for the original stamping die as well as the optimized stamping die from the master thesis discussed above. The analyses are performed using an uncoupled approach, where one thermal analysis is followed by a quasi-static elasto-plastic analysis. The thermal analysis simulates the solidification and cooling during the casting process, while the quasi-static elasto-plastic analysis uses the temperature history, obtained from the thermal analysis, in order to build up residual stresses. The thermal analysis includes the release of latent heat. Furthermore, the material properties included in the heat equation (density, conductivity, specific heat) are given as temperature dependent properties for the mould as well as the casting. In the quasi-static elasto-plastic analysis the plasticity is described by the von Mises yield surface in combination with isotropic hardening and the mechanical properties (thermal expansion coefficient, Young's modulus, yield stress, hardening parameter, Poisson's ratio) are given as temperature dependent properties. The simulations show high levels of residual stresses.

     

  • 14.
    Hofwing, Magnus
    et al.
    Jönköping University, School of Engineering, JTH. Research area Product Development - Simulation and Optimization.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH. Research area Product Development - Simulation and Optimization.
    Tapankov, Martin
    Jönköping University, School of Engineering, JTH. Research area Product Development - Simulation and Optimization.
    Optimal Polynomial Regression Models by using a Genetic Algorithm2011In: Proceedings of the second International Conference on Soft Computing Technology in Civil, Structural and Environmental Engineering / [ed] Yiannis Tsompanakis; B H V Topping, 2011Conference paper (Refereed)
  • 15. Ireman, P
    et al.
    Klarbring, A
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    A model of damage coupled to wear2003In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 40, no 12, p. 2957-2974Article in journal (Refereed)
  • 16. Ireman, P
    et al.
    Klarbring, A
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Algorithms for thermoelastic wear problems2002In: Contact mechanics: proceedings of the 3rd Contact Mechanics International Symposiuum, Praia da Consolação, Peniche, Portugal, 17-21 June 2001, Dordrecht: Kluwer Academic , 2002, p. 363-370Conference paper (Refereed)
  • 17. Ireman, P
    et al.
    Klarbring, A
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Algoritmer för termoelastiska nötningsproblem2001In: Svenska Mekanikdagar, Linköpings universitet, 11-13 juni,2001, 2001Conference paper (Other academic)
  • 18. Ireman, P
    et al.
    Klarbring, A
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Finite element algorithms for thermoelastic wear problems2002In: European journal of mechanics. A, Solids, ISSN 0997-7538, E-ISSN 1873-7285, Vol. 21, no 3, p. 423-440Article in journal (Refereed)
  • 19. Ireman, P
    et al.
    Klarbring, A
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Gradient Theory of Damage Coupled to Frictional Contact and Wear, and Its Numerical Treatment2009In: CMES - Computer Modeling in Engineering & Sciences, ISSN 1526-1492, E-ISSN 1526-1506, Vol. 52, no 2, p. 125-158Article in journal (Refereed)
  • 20. Klarbring, A
    et al.
    Lundvall, O
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    A flexible multi-body approach for frictional contact in spur gears2004In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 278, no 3, p. 479-499Article in journal (Refereed)
  • 21.
    Klarbring, Anders
    et al.
    Linköping university.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH. Research area Product Development - Simulation and Optimization.
    A Note on the Min-Max Formulation of Stiffness Optimization including Non-Zero Prescribed Displacements2012In: Structural and multidisciplinary optimization (Print), ISSN 1615-147X, E-ISSN 1615-1488, Vol. 45, no 1, p. 147-149Article in journal (Refereed)
    Abstract [en]

    The present theoretical note shows how a naturalobjective function in stiffness optimization, including bothprescribed forces and non-zero prescribed displacements,is the equilibrium potential energy. It also shows how theresulting problem has a saddle point character that may beutilized when calculating sensitivities.

  • 22.
    Klarbring, Anders
    et al.
    Linköping university.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH. Research area Product Development - Simulation and Optimization.
    Topology optimization of hyperelastic bodies including non-zero prescribed displacements2013In: Structural and multidisciplinary optimization (Print), ISSN 1615-147X, E-ISSN 1615-1488, Vol. 47, no 1, p. 37-48Article in journal (Refereed)
    Abstract [en]

    Stiffness topology optimization is usually based on a state problem of linear elasticity, and there seems to be little discussion on what is the limit for such a small rotation-displacement assumption. We show that even for gross rotations that are in all practical aspects small (<3 deg), topology optimization based on a large deformation theory might generate different design concepts compared to what is obtained when small displacement linear elasticity is used. Furthermore, in large rotations, the choice of stiffness objective (potential energy or compliance), can be crucial for the optimal design concept. The paper considers topology optimization of hyperelastic bodies subjected simultaneously to external forces and prescribed non-zero displacements. In that respect it generalizes a recent contribution of ours to large deformations, but we note that the objectives of potential energy and compliance are no longer equivalent in the non-linear case. We use seven different hyperelastic strain energy functions and find that the numerical performance of the Kirchhoff–St.Venant model is in general significantly worse than the performance of the other six models, which are all modifications of this classical law that are equivalent in the limit of infinitesimal strains, but do not contain the well-known collapse in compression. Numerical results are presented for two different problem settings.

  • 23.
    Rashid, Asim
    et al.
    Jönköping University, School of Engineering, JTH. Research area Product Development - Simulation and Optimization.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH. Research area Product Development - Simulation and Optimization.
    An Efficient Sequential Approach for Simulation of Thermal Stresses in Disc Brakes2012In: Nordtrib 2012, 15th Nordic Symposium on Tribology, 2012, 2012Conference paper (Other academic)
    Abstract [en]

    In this paper an efficient approach to simulate thermal stresses due to frictional heating of disc brakes is presented. Inthe approach thermal and stress analysis are performed sequentially. The frictional heat analysis is based on the Eulerianmethod, which requires significantly low computational time as compared to the Lagrangian approach. Completethree-dimensional geometries of a disc and a pad are considered for the numerical simulations. The contact forcesare computed at each time step taking the thermal deformations of the disc into account. The nodal temperaturehistory is recorded at each time step and is used in sequentially coupled stress analysis, where a temperature dependentelasto-plastic material model is used to compute the stresses in a disc brake. The results show that during hard braking,high compressive stresses are generated on the disc surface in circumferential direction which cause plastic yielding. Butwhen the disc cools down, the compressive stresses transform to tensile stresses. Such thermoplastic stress history maycause cracks on disc surface after a few braking cycles. These results are in agreement with experimental observationsavailable in the literature.

  • 24.
    Rashid, Asim
    et al.
    Jönköping University, School of Engineering, JTH. Research area Product Development - Simulation and Optimization.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH. Research area Product Development - Simulation and Optimization.
    Sequential simulation of thermal stresses in disc brakes for repeated braking2013In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 227, no 8, p. 919-929Article in journal (Refereed)
    Abstract [en]

    In this paper, an efficient sequential approach for simulating thermal stresses in brake discs for repeated braking is presented. First, a frictional heat analysis is performed by using an Eulerian formulation of the disc. Then, by using the temperature history from the first step of the sequence, a plasticity analysis with temperature dependent material data is performed in order to determine the corresponding thermal stresses. Three-dimensional geometries of a disc and a pad to a heavy truck are considered in the numerical simulations. The contact forces are computed at each time step taking the thermal deformations of the disc and pad into account. In such manner, the frictional heat power distribution will also be updated in each time step, which in turn will influence the development of heat bands. The plasticity model is taken to be the von Mises yield criterion with linear kinematic hardening, where both the hardening and the yield limit are temperature dependent. The results show that during hard braking, high compressive stresses are generated on the disc surface in the circumferential direction which cause yielding. But when the disc cools down, these compressive stresses transform to tensile residual stresses. For repeated hard braking when this kind of stress history is repeated, we also show that stress cycles with high amplitudes are developed which might generate low cycle fatigue cracks after a few braking cycles.

  • 25.
    Rashid, Asim
    et al.
    Jönköping University, School of Engineering, JTH. Research area Product Development - Simulation and Optimization.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH. Research area Product Development - Simulation and Optimization.
    Thermomechanical Simulation of Wear and Hot Bands in a Disc Brake by Adopting an Eulerian Approach2013In: Eurobrake 2013, 2013Conference paper (Refereed)
    Abstract [en]

    In this paper frictional heating of a disc brake is simulated while taking wear into account. By performing thermomechanical finite element analysis, it is studied how the wear history will influence the development of hot bands. The frictional heat analysis is based on an Eulerian formulation of the disc, which requires significantly lower computational time as compared to a standard Lagrangian approach. A real disc-pad system to a heavy truck is considered, where complete three-dimensional geometries of the ventilated disc and pad are used in the simulations. A sequential approach is adopted, where the contact forces are computed at each time step taking the wear and thermal deformations of the mating parts into account. After each brake cycle, the wear profile of the pad is updated and used in subsequent analysis. The results show that when wear is considered, different distributions of the temperature on disc are obtained for each new brake cycle. After a few braking cycles two hot bands appear on the disc surface instead of only one. These results are in agreement with experimental observations.

  • 26.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    A method for structural dynamic contact problems with friction and wear2003In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 58, no 15, p. 2371-2385Article in journal (Refereed)
  • 27.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    A Newton algorithm for fretting problems1996In: Euromech Colloquium 351, Systems with Coulomb friction, Vadstena, Sweden, August 5-7, 1996, 1996Conference paper (Other academic)
  • 28.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    A Newton algorithm for wear problems1997In: 3rd EUROMECH Solid Mechanics Conference, Stockholm, Sweden, August 18-22, 1997, 1997Conference paper (Other academic)
  • 29.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    A Newton method for three-dimensional fretting problems1999In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 36, no 14, p. 2075-2090Article in journal (Refereed)
  • 30.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    An augmented Lagrangian method for fretting problems1996In: Euromech Colloquium 346, March 20-22, Oxford, 1996., 1996Conference paper (Other academic)
  • 31.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    An augmented Lagrangian method for fretting problems1997In: European journal of mechanics. A, Solids, ISSN 0997-7538, E-ISSN 1873-7285, Vol. 16, no 4, p. 573-593Article in journal (Refereed)
  • 32.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    An Efficient Tradeoff Approach for Topology Optimization with Manufacturing Constraints2010In: 36th Design Automation Conference, ASME proceedings, 2010Conference paper (Refereed)
  • 33.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH. Research area Product Development - Simulation and Optimization.
    An Eulerian approach for simulating frictional heat bands in rotating discs2012Conference paper (Other academic)
  • 34.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH. Research area Product Development - Simulation and Optimization.
    An Eulerian Approach for Simulating Frictional Heating in Disc-Pad Systems2011In: European journal of mechanics. A, Solids, ISSN 0997-7538, E-ISSN 1873-7285, Vol. 30, no 5, p. 673-683Article in journal (Refereed)
    Abstract [en]

    Thermal stresses as a result from frictional heating must be considered when designing disc brakes, clutches or other rotating machine components with sliding contact conditions. The rotational symmetry of the disc in these kind of applications makes it possible to model these systems using an Eulerian approach instead of a Lagrangian framework. In this paper such an approach is developed and implemented. The disc is formulated in an Eulerian frame where the convective terms are defined by the angular velocity. By utilizing the Eulerian framework, a node-to-node formulation of the contact interface is obtained, producing most accurate frictional heat power solutions. The energy balance of the interface is postulated by introducing an interfacial temperature. Both frictional power and contact conductances are included in this energy balance. The contact problem is solved by a non-smooth Newton method. By adopting the augmented Lagrangian approach, this is done by rewriting Signorini’s contact conditions to an equivalent semi-smooth equation. The heat transfer in the disc is discretized by a Petrov–Galerkin approach, i.e. the numerical difficulties due to the non-symmetric convective matrix appearing in a pure Galerkin discretization is treated by following the streamline-upwind approach. In such manner a stabilization is obtained by adding artificial conduction along the streamlines. For each time step the thermo-elastic contact problem is first solved for the temperature field from the previous time step. Then, the heat transfer problem is solved for the corresponding frictional power. In such manner a temperature history is obtained sequentially via the trapezoidal rule. In particular the parameter is set such that both the Crank–Nicolson and the Galerkin methods are utilized. The method seems very promising. This is demonstrated by solving a two-dimensional benchmark as well as a real disc brake system in three dimensions.

  • 35.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    An Implicit Method for Frictional Contact, Impact and Rolling2005In: European journal of mechanics. A, Solids, ISSN 0997-7538, E-ISSN 1873-7285, Vol. 24, no 6, p. 1016-1029Article in journal (Refereed)
    Abstract [en]

    In this paper an implicit method for frictional contact, impact and rolling is suggested. A nonclassical formulation of a two-dimensional hyperelastic body unilaterally constrained to rigid supports is proposed by following the ideas of Moreau and Jean. A total Lagrangian formulation of the system is given. The elastic properties are defined by coupling the second Piola–Kirchhoff stress to the Green–Lagrange strain via the Kirchhoff–St. Venant law. The equation of motion is written in the spirit of Moreau by using the mean value impulses introduced by Jean. The mean value impulses appear explicitly in the equation of motion. In such manner the treatment of nonconstant kinematic transformation matrices becomes straightforward. The rigid supports are described by smooth functions. By utilizing these functions and the mean value impulses, new contact/impact laws of Signorini and Coulomb type are formulated. The governing equations are solved by a nonsmooth Newton method. This is performed by following the augmented Lagrangian approach and deriving the consistent stiffness matrix as well as the contact stiffness matrices. Three two-dimensional examples are solved by the method: a contact problem, an impact problem and a rolling contact problem.

  • 36.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Augmented Lagrangian methods for wear problems1995In: NSCM VIII: eighth Nordic seminar on computational mechanics : Göteborg November 17-18, 1995 : short papers, Göteborg: Department of Structural Mechanics, Chalmers University of Technology , 1995Conference paper (Other academic)
  • 37.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Conceptual design of a hub by using topology optimization and residual stress simulations2007In: handouts in the proceedings of the 1st European HTC, 23-24 October, Berlin, 2007, 2007Conference paper (Other (popular science, discussion, etc.))
  • 38.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Contact, impact and rolling of a nonlinear elastic body on rigid foundations2005In: Proceedings of Multibody Dynamics, International Conference on Advances in Computational Multibody Dynamics: June 21-24, Madrid, Spain, 2005, 2005Conference paper (Refereed)
  • 39.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Contact Modeling in Topology Optimization2010In: the IV European Conference on Computational Mechanics (Abstracs), 2010Conference paper (Refereed)
  • 40.
    Strömberg, Niclas
    Linköping University.
    Continuum Thermodynamics of Contact Friction and Wear1995Licentiate thesis, monograph (Other scientific)
  • 41.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH. Research area Product Development - Simulation and Optimization.
    Development and Implementation of an Eulerian Approach for Efficient Simulation of Frictional Heating in Sliding Contacts2011In: Coupled problems 2011 : computational methods for coupled problems in science and engineering IV: proceedings of the IV International Conference on Computational Methods for Coupled Problems in Science and Engineering held in Kos, Greece, 20 - 22 June 2011, 2011Conference paper (Refereed)
  • 42.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    En implicit metod för kontakt och stötproblem med stora rotationer2007In: Luleå tekniska universitet, Svenska Mekanikdagar, 13-15 juni, 2007, 2007Conference paper (Other academic)
  • 43.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Finite element treatment of thermoelastic wear problems1998In: Proceedings of the IUTAM-Symposium on Unilateral Multibody Dynamics, 1998Conference paper (Refereed)
  • 44.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Finite element treatment of tribological problems1998In: Proceedings of the International Symposium on Impact and Friction of Solids, Structures and Machines, June 27-30, Ottawa, Canada, 1998, 1998Conference paper (Refereed)
  • 45.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Finite element treatment of two-dimensional thermoelastic wear problems1999In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 177, no 3-4, p. 441-455Article in journal (Refereed)
  • 46.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Frictional Contact/Impact between a Hyperelastic Body and Moving Rigid Obstacles2006In: Proceedings of the 3rd European Conference on Computational Mechanics: June 5-9, Lisbon, Portugal, 2006., 2006Conference paper (Refereed)
  • 47.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering.
    Optimering av styrstavsbladets huvuddimensioner med hjälp av FE-programmet ANSYS, LiTH-IKP-Ex-10171992Licentiate thesis, monograph (Other scientific)
  • 48.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH. Research area Product Development - Simulation and Optimization.
    RBDO with Non-Gaussian Variables by using a LHS- and SORM-based SLP approach and Optimal Regression Models2012Conference paper (Other academic)
    Abstract [en]

    A general sequential linear programming (SLP) approach for reliability based design optimization (RBDO) with non-Gaussian random variables is presented. The RBDO problems are formulated by using optimal regression models (ORM) as surrogate models and S-optimal design of experiments (DoE). The S-optimal DoE is obtained by maximizing the average mean of the distances between the nearest neighbors. Finite element simulations are performed for the S-optimal DoE and corresponding ORM are obtained by a genetic algorithm. In such manner not only optimal regression coefficients are generated but also optimal rational base functions. The RBDO problems are solved by introducing intermediate variables defined by the iso-probabilistic transformation at the most probable point. By using these variables in the Taylor expansions, a corresponding deterministic linear programming problem is derived, which is corrected by applying second order reliability methods (SORM) as well as Monte Carlo simulations. For low target values on the reliability crude Monte Carlo simulations are used, but for high targets a Latin hypercube sampling (LHS) approach is utilized. The implementation of the suggested sampling- and SORM-based SLP approach is efficient and robust. This is demonstrated by presenting trade-off curves between the objective function, constraints, variables and the target of reliability.

  • 49.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Engineering mechanics and optimization.
    Simulation of Rotary Draw Bending using Abaqus and a Neural Network2005In: Proceedings of Nafems Nordic Conference on Component and System Analysis using Numerical Simulation Techniques - FEA, CFD, MBS: November 24-25, Gothenburg, 2005., 2005Conference paper (Refereed)
  • 50.
    Strömberg, Niclas
    Jönköping University, School of Engineering, JTH. Research area Product Development - Simulation and Optimization.
    Simulering av bromsvärme i en skivbroms med en Eulerformulering, Svenska Mekanikdagar2011Conference paper (Other academic)
12 1 - 50 of 72
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