Modal identification of nonlinear substructures and implementation in structural coupling analysis

Download
2008
Arslan, Özge
In this work, a new method is suggested for the modal identification of nonlinear structures and for the use of the modal data in calculating response of the nonlinear system to harmonic excitation. Nonlinearity in mechanical structures is usually encountered in connection regions. In this study, the nonlinear part of such a structure is modeled as a single nonlinear element and modal parameters of the structure are obtained as a function of displacement amplitude. Identification and modeling of nonlinear elements can be done through modal tests conducted at different response levels. Response level dependent modal parameters are used in calculating the response of the system to harmonic excitation at any forcing level. Furthermore, the modal model of a nonlinear substructure can be used in structural coupling of the nonlinear system with a linear one, and in structural modification problems where a nonlinear structure is modified with linear elements. Validation of the modal model proposed, and the use of this model in harmonic response computation, structural coupling and structural modification problems are demonstrated with several case studies.

Suggestions

A two dimensional euler flow solver on adaptive cartesian grids
Siyahhan, Bercan; Aksel, Mehmet Haluk; Department of Mechanical Engineering (2008)
In the thesis work, a code to solve the two dimensional compressible Euler equations for external flows around arbitrary geometries have been developed. A Cartesianmesh generator is incorporated to the solver. Hence the pre-processing can be performed together with the solution within a single code. The code is written in the C++ programming language and its object oriented capabilities have been exploited to save memory in the data structure developed. The Cartesian mesh is formed by dividing squares succe...
Analysis of thin walled open section tapered beams using hybrid stress finite element method
Akman, Mehmet Nazım; Oral, Süha; Department of Mechanical Engineering (2008)
In this thesis, hybrid stress finite element is formulated for the analysis of the isotropic, thin walled, open section beams with variable cross sections. The beam element has two nodes each having seven degrees of freedom. Assumption of stress field is sufficient to determine the element stiffness matrix. Axial, flexural and torsional effects are taken into account in the analysis. The methodology can be applied both to the tapered and the uniform beams. Throughout this study, firstly element cross-sectio...
Finite element structural model updating by using experimental frequency response functions
Öztürk, Murat; Özgüven, Hasan Nevzat; Department of Mechanical Engineering (2009)
Initial forms of analytical models created to simulate real engineering structures may generally yield dynamic response predictions different than those obtained from experimental tests. Since testing a real structure under every possible excitation is not practical, it is essential to transform the initial mathematical model to a model which reflects the characteristics of the actual structure in a better way. By using structural model updating techniques, the initial mathematical model is adjusted so that...
Fully Coupled Smoothed Particle Hydrodynamics-Finite Element Method Approach for Fluid-Structure Interaction Problems With Large Deflections
Dincer, A. Ersin; Demir, Abdullah; Bozkuş, Zafer; Tijsseling, Arris S. (ASME International, 2019-08-01)
In this study, a combination of the smoothed particle hydrodynamics (SPH) and finite element method (FEM) solving the complex problem of interaction between fluid with free surface and an elastic structure is studied. A brief description of SPH and FEM is presented. Contact mechanics is used for the coupling between fluid and structure, which are simulated with SPH and FEM, respectively. In the proposed method, to couple meshfree and mesh-based methods, fluid and structure are solved together by a complete ...
A genetic algorithm for 2d shape optimization
Chen, Wei Hang; Oral, Süha; Department of Mechanical Engineering (2008)
In this study, an optimization code has been developed based on genetic algorithms associated with the finite element modeling for the shape optimization of plane stress problems. In genetic algorithms, constraints are mostly handled by using the concept of penalty functions, which penalize infeasible solutions by reducing their fitness values in proportion to the degrees of constraint violation. In this study, An Improved GA Penalty Scheme is used. The proposed method gives information about unfeasible ind...
Citation Formats
Ö. Arslan, “Modal identification of nonlinear substructures and implementation in structural coupling analysis,” M.S. - Master of Science, Middle East Technical University, 2008.