## Implementation of a direct procedure for critical point computations using preconditioned iterative solvers

Research output: Contribution to journal › Article › Scientific › peer-review

### Standard

**Implementation of a direct procedure for critical point computations using preconditioned iterative solvers.** / Kouhia, Reijo; Tůma, Miroslav; Mäkinen, Jari; Fedoroff, Alexis; Marjamäki, Heikki.

Research output: Contribution to journal › Article › Scientific › peer-review

### Harvard

*Computers & Structures*, vol. 108-109, pp. 110-117. https://doi.org/10.1016/j.compstruc.2012.02.009

### APA

*Computers & Structures*,

*108-109*, 110-117. https://doi.org/10.1016/j.compstruc.2012.02.009

### Vancouver

### Author

### Bibtex - Download

}

### RIS (suitable for import to EndNote) - Download

TY - JOUR

T1 - Implementation of a direct procedure for critical point computations using preconditioned iterative solvers

AU - Kouhia, Reijo

AU - Tůma, Miroslav

AU - Mäkinen, Jari

AU - Fedoroff, Alexis

AU - Marjamäki, Heikki

N1 - /kir12<br/>Contribution: organisation=mec,FACT1=1<br/>Publisher name: Elsevier

PY - 2012/10

Y1 - 2012/10

N2 - Computation of critical points on an equilibrium path requires the solution of a non-linear eigenvalue problem. These critical points could be either bifurcation or limit points. When the external load is parametrized by a single parameter, the non-linear stability eigenvalue problem consists of solving the equilibrium equations along the criticality condition. Several techniques exist for solution of such a system. Their algorithmic treatment is usually focused for direct linear solvers and thus use the block elimination strategy. In this paper special emphasis is given for a strategy which can be used also with iterative linear solvers. Comparison to the block elimination strategy with direct linear solvers is given. Due to the non-uniqueness of the critical eigenmode a normalizing condition is required. In addition, for bifurcation points, the Jacobian matrix of the augmented system is singular at the critical point and additional stabilization is required in order to maintain the quadratic convergence of the Newton's method. Depending on the normalizing condition, convergence to a critical point with negative load parameter value can happen. The form of the normalizing equation is critically discussed. Due to the slenderness of the buckling sensitive structures the resulting matrices are ill-conditioned and a good preconditioner is mandatory for efficient solution. © 2012 Civil-Comp Ltd. and Elsevier Ltd. All rights reserved.

AB - Computation of critical points on an equilibrium path requires the solution of a non-linear eigenvalue problem. These critical points could be either bifurcation or limit points. When the external load is parametrized by a single parameter, the non-linear stability eigenvalue problem consists of solving the equilibrium equations along the criticality condition. Several techniques exist for solution of such a system. Their algorithmic treatment is usually focused for direct linear solvers and thus use the block elimination strategy. In this paper special emphasis is given for a strategy which can be used also with iterative linear solvers. Comparison to the block elimination strategy with direct linear solvers is given. Due to the non-uniqueness of the critical eigenmode a normalizing condition is required. In addition, for bifurcation points, the Jacobian matrix of the augmented system is singular at the critical point and additional stabilization is required in order to maintain the quadratic convergence of the Newton's method. Depending on the normalizing condition, convergence to a critical point with negative load parameter value can happen. The form of the normalizing equation is critically discussed. Due to the slenderness of the buckling sensitive structures the resulting matrices are ill-conditioned and a good preconditioner is mandatory for efficient solution. © 2012 Civil-Comp Ltd. and Elsevier Ltd. All rights reserved.

KW - Critical points

KW - Equilibrium equations

KW - Non-linear eigenvalue problem

KW - Preconditioned iterations

UR - http://www.scopus.com/inward/record.url?scp=84865782578&partnerID=8YFLogxK

U2 - 10.1016/j.compstruc.2012.02.009

DO - 10.1016/j.compstruc.2012.02.009

M3 - Article

VL - 108-109

SP - 110

EP - 117

JO - Computers & Structures

JF - Computers & Structures

SN - 0045-7949

ER -