Modal identification of nonlinear substructures and implementation in structural coupling analysis

Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Mechanical Engineering, Turkey

Approval Date: 2008




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.