| 11. |
- Sikström, Fredrik, 1971, et al.
(författare)
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Model order reduction methods applied to a welding model
- 2012
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Ingår i: Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering. - : SAGE Publications. - 2041-3041 .- 0959-6518. ; 226:I7, s. 972-984
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Tidskriftsartikel (refereegranskat)abstract
- A finite element representation modelling transient heat conduction of gas tungsten arc welding of stainless steel is used to evaluate different methods for model order reduction. The focus is on establishing a linear low-order model of the dynamic relation between the welding current and the temperature measured by a radiation pyrometer. The objective of this low-order model is to design a model-based feedback controller and to investigate the consequences of applying feedback control of the process. Three different approaches for model reduction have been evaluated, namely the Krylov subspace method for moment matching, balanced truncation and parametric system identification. The study provides a knowledge base for the selection of model order reduction methods when dealing with large-scale systems like finite element models of transient heat conduction, and it recommends parametric system identification. It renders sufficient approximations for controller design, no linearization of the finite element model is required, and there is no limit on degrees of freedom of the finite element model.
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| 12. |
- Sikström, Fredrik, 1971-, et al.
(författare)
-
Role of fixture forces on distortion in gas tungsten arc welding - an experimental and modelling approach
- 2011
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Ingår i: Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture. - : Sage Publications. - 0954-4054 .- 2041-2975. ; 225:B1, s. 140-148
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Tidskriftsartikel (refereegranskat)abstract
- Simulation and experiments show that the fixture clamping force has a significant influence on the structural integrity of a welded workpiece. This understanding is of great importance for the manufacture of aerospace components with tight tolerances in the specifications. The focus in the present study is on the temperature history during welding and residual deformation; its main contribution is a demonstrator designed for evaluation of the influence of fixture clamping forces and validation of the simulation results. The demonstrator concerns a simplified situation considering gas tungsten arc welding of a nickel-based metal plate fixed by a specially designed fixture, where one side of the plate was clamped with different levels of force. The temperature history was measured during the weld sequence and deformation measurements were performed after cooling and release of the workpiece from the fixture. The results from simulation and experimentation showed good agreement. The proposed strategy is industrially competitive and has shown that the looser the fixture clamps, the smaller the residual deformation. Furthermore, the study provides a knowledge base for selection of active fixture concepts in that the fixture clamping force can be determined in advance and possibly also be subject to force control.
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