STRUCTURAL MODIFICATION OF NONLINEAR SYSTEMS USING MODAL MODELS

Date

2024-1-4

Author

Ekinci, Elif Ceren

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There are various methods for structural modification in linear systems, with which either the Frequency Response Functions (FRFs) or the modal properties of the modified system can be calculated without reanalyzing the modified system. However, for modifications in nonlinear systems, as the first step the nonlinearities in the system need to be modeled. When the structural modification method is applied to an existing system, the nonlinear elements in the system should be identified. Most of the identification methods require to know the location, type and strength of the nonlinearities. This cannot be possible in some systems, that is, the system may have strong nonlinearities in multiple locations and it may be difficult, if not impossible, to identify all the nonlinearity effects. The aim of this thesis is to develop a structural modification method that does not require to know the locations and strength of nonlinearities in the system. For that purpose in this thesis, unmodified nonlinear system will be analyzed using the Response Controlled Testing Method which will result in the modal domain model of the original system at different constant dipalcement amplitude levels. Then, the frequency response functions at different forcing levels will be calculated utilizing this modal model. Using the FRFs of the original system and the matrices representing modification, FRFs of the modified system at different forcing levels is calculated in a computationally efficient way.

Subject Keywords

nonlinear, structural modification, sub-structuring

URI

https://hdl.handle.net/11511/108865

Collections

Graduate School of Natural and Applied Sciences, Thesis