| 11. |
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| 12. |
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| 13. |
- Johansson, Håkan, 1979, et al.
(författare)
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Application-Specific Error Control in Inverse Identification
- 2008
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Ingår i: 8th World Concress on Computational Mechanics WCCM8, 5th European Congress on Computational Methods in Applied Sciences and Engineering ECCOMAS 2008 (Edited by B.A. Schrefler and U. Perego). - 9788496736559 ; :CD, s. 1p abstract-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 14. |
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| 15. |
- Johansson, Håkan, 1979, et al.
(författare)
-
Calibration of a class of non-linear viscoelasticity models with adaptive error control
- 2007
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Ingår i: Computational Mechanics. - : Springer Science and Business Media LLC. - 1432-0924 .- 0178-7675. ; 41:1, s. 107-119
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Tidskriftsartikel (refereegranskat)abstract
- The calibration of constitutive models is considered as an optimization problem where parameter values are sought to minimize the discrepancy between measured and simulated response. Since a finite element method is used to solve an underlying state equation, discretization errors arise, which induce errors in the calibrated parameter values. In this paper, adaptive mesh refinement based on the pertinent dual solution is used in order to reduce discretization errors in the calibrated material parameters. By a sensitivity assessment, the influence from uncertainties in experimental data is estimated, which serves as a threshold under which there is no need to further reduce the discretization error. The adaptive strategy is employed to calibrate a viscoelasticity model with observed data from uniaxial compression (i.e., homogeneous stress state), where the FE-discretization in time is studied. The a posteriori error estimations show an acceptable quality in terms of effectivity measures. © 2007 Springer Verlag.
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| 16. |
- Johansson, Håkan, 1979, et al.
(författare)
-
Calibration of a class of non-linear viscoelasticity models with sensitivity assessment based on duality
- 2007
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Ingår i: International Journal for Numerical Methods in Engineering. - : Wiley. - 0029-5981 .- 1097-0207. ; 69:12, s. 2513-2537
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Tidskriftsartikel (refereegranskat)abstract
- The calibration of constitutive models is based on the solution of an optimization problem, whereby the sought parameter values minimize an objective function that measures the discrepancy between experimental observations and the corresponding simulated response. By the introduction of an appropriate adjoint problem, the resulting formulation becomes well suited for a gradient-based optimization scheme. A class of viscoelastic models is studied, where a discontinuous Galerkin method is used to integrate the governing evolution equation in time. A practical solution algorithm, which utilizes the time-flow structure of the underlying evolution equation, is presented. Based on the proposed formulation it is convenient to estimate the sensitivity of the calibrated parameters with respect to measurement noise. The sensitivity is computed using a dual method, which compares favourably with the conventional primal method. The strategy is applied to a viscoelasticity model using experimental data from a uniaxial compression test. Copyright © 2006 John Wiley & Sons, Ltd.
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| 17. |
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| 18. |
- Johansson, Håkan, 1979, et al.
(författare)
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Calibration of a nonlinear viscoelasticity model with sensitivity assessment
- 2005
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Ingår i: Constitutive Models for Rubber IV, edited by P.-E. Austrell & L. Kari. - 0415383463 ; , s. 341-347
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Konferensbidrag (refereegranskat)abstract
- The calibration of constitutive models isbased on the solution of an optimization problem, where parameter values are sought such that optimal correspondence between measured and simulated response is achieved. The calibration problem is solved using a recently proposed strategy, which has the advantage that discretization errors induced in the simulated response, leading to errors in the optimal parameter values, isrelatively straightforward to estimate. Furthermore, it ispossible to estimate how sensitive the obtained solution is to uncertainties in the experimental data.
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| 19. |
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| 20. |
- Johansson, Håkan, 1979, et al.
(författare)
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Calibration of the Bergström-Boyce model: Explicit expressions
- 2005
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this report we derive the explicit expressions associated with the calibration of the Bergström-Boyce modelof nonlinear viscoelasticity. These expressions are intended for practical use in a computational algorithm.
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