Energy Method for Selection of Degrees of Freedom in Condensation

Kim, Ki-Ook; Choi, Young-Jae

doi:10.2514/2.1095

Cited by 38 publications

(17 citation statements)

References 19 publications

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“…Although the EIDV method has a similar objective for choosing DOFs as the Henshell and Ong [9] method, the objective of the EIDV method is not exactly the maximization problem of Eq. (18). Therefore, it is expected that the Henshell and Ong method returns better solutions to the given maximization problem than the EIDV method, as is shown in the next section.…”

Section: Automatic Master Degree-of-freedom Selectionmentioning

confidence: 85%

“…Here, this concept is applied to the problem of finding the optimal N that solves Eq. (18). Namely, the corresponding eigenvalue problem is Eq.…”

Section: Automatic Master Degree-of-freedom Selectionmentioning

confidence: 99%

“…The corresponding maximization problem is given by Eq. (18). Solving this problem for the lowest eigenvalue !…”

Section: Automatic Master Degree-of-freedom Selectionmentioning

confidence: 99%

“…Another class of methods is based on the concept of modal energy. For example, the method proposed by Kim and Choi [18] uses the energy distribution among the DOFs for each mode, and it chooses the set of primary DOFs by taking the partial sum over the rows of the energy distribution matrix. The method proposed by Cho and Kim [19] uses energy estimation at the discretization element level by the Rayleigh quotient value of each element.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Node Sampling for Nonlinear Vibration Analysis of Structures with Intermittent Contact

et al. 2010

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Section: Automatic Master Degree-of-freedom Selectionmentioning

confidence: 85%

“…Here, this concept is applied to the problem of finding the optimal N that solves Eq. (18). Namely, the corresponding eigenvalue problem is Eq.…”

Section: Automatic Master Degree-of-freedom Selectionmentioning

confidence: 99%

“…The corresponding maximization problem is given by Eq. (18). Solving this problem for the lowest eigenvalue !…”

Section: Automatic Master Degree-of-freedom Selectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Node Sampling for Nonlinear Vibration Analysis of Structures with Intermittent Contact

et al. 2010

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“…It should be noted that the retained DoFs are chosen carefully so that the overall behavior of the reduced system will be equivalent to that of the GFEM. Various studies are conducted for the proper selection of the retained DoFs for many applications [79][80][81][82][83].…”

Section: Condensation Techniques Involves Dividing the Total Dofs Of mentioning

confidence: 99%

Development and Design Optimization of High Fidelity Reduced Order Models for Dynamic Aeroelasticity Loads Analyses of Complex Airframes

Thomas¹

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Identification of aircraft critical loads envelope requires a lengthy and rigorous analysis procedure that includes simulating the aircraft at thousands of load cases identified in the certification requirements. Imposing a Global Finite Element Model (GFEM) in this process is computationally very expensive. Hence, Reduced Order Models (ROM) of airframes are commonly employed in the static and dynamic aeroelasticity analyses. ROMs must be simple enough to be analyzed thousands of times during the iterative aeroelastic simulation but sufficiently accurate to have their dynamic characteristics closely matching those of the GFEM within a frequency range of interest. Several Model Order Reduction (MOR) methodologies are available in the literature with the Stick Model (SM) being the preferred methodology adopted by the aerospace industry. A SM is a series of beam elements extending along the airframe elastic axis that offers an intuitive spatial representation of the airframe mass and stiffness distributions, a feature of paramount importance to the development engineers in the aerospace industry. However, due to several approximations and simplifications in the current development process, it is evidently found that SM's are not sufficiently appropriate for dynamic simulations. To overcome such limitation, this thesis presents two approaches for the development of high fidelity stick models. The first approach is based on a Hybrid Stick Model (HSM) representation in which the conventional SM is augmented by a set of structural matrices to account for inaccuracies that might be encountered in the modal performance of the base SM as compared to the GFEM. In the second approach, we solve a design optimization problem in which we optimize the stiffness parameters of the conventional SM to minimize errors in its modal pairs with reference to the GFEM. The final product of the optimization iii problem is an Optimized Stick Model (OSM) with dynamic characteristics that closely matching those of the GFEM within a specified frequency range of interest. Case studies are presented where the HSM and the OSM along with the conventional SM are employed in the dynamic aeroelasticity loads analyses of a Bombardier aircraft platform. The extracted aeroelastic loads are compared against those generated employing the aircraft GFEM. The dynamic characteristics of the ROMs are also assessed based on their modal characteristics using metrics of Modal Assurance Criteria (MAC) and Modal Participation Factors (MPF). Results obtained show that the developed HSM and OSM have superior dynamic characteristics compared to the conventional SM.

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Improvement of reduction method combined with sub‐domain scheme in large‐scale problem

Kim

Cho

2006

Numerical Meth Engineering

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SUMMARYFor a few decades, various approximate techniques have been developed to calculate the eigenvalues in a reduced manner. In order to construct reliable reduced systems it is essential to select the proper primary degrees of freedom (PDOFs). Unless the PDOFs are selected properly, the selection of PDOFs might be localized and the eigenvalue prediction might emphasize excessively the lower modes or lose the important modes. Moreover, sometimes, it takes considerable amount of computing time to construct a reduced system in large-scale problem. These troubles in constructing reduced system can be avoided by applying reduction scheme in sub-domain level. After dividing global system into a number of subdomains, reduced system which has only the PDOFs is constructed in each sub-domain. This paper presents new algorithms to construct efficient reduction system through three different schemes. They are version 1, version 2 and version 3 systems. The version 3 system is constructed by combining the advantages of the version 1 and the version 2 systems. Numerical examples demonstrate that the proposed version 3 method saves computational cost effectively and provides a reduced system which can predict accurate eigenvalues of global system.

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Energy Method for Selection of Degrees of Freedom in Condensation

Cited by 38 publications

References 19 publications

Node Sampling for Nonlinear Vibration Analysis of Structures with Intermittent Contact

Node Sampling for Nonlinear Vibration Analysis of Structures with Intermittent Contact

Development and Design Optimization of High Fidelity Reduced Order Models for Dynamic Aeroelasticity Loads Analyses of Complex Airframes

Improvement of reduction method combined with sub‐domain scheme in large‐scale problem

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