Seyed Ehsan Haji Agha Mohammad Zarbaf - PhD Student, Iranian Research Organization for Science and Technology
Mohammad Mahdi Malekian - Assistant Professor, Iranian Research Organization for Science and Technology
Hasan Jalali - Assistant Professor, Arak University of Technology

Structural nonlinearity is a frequent occurrence in mechanical structures encounter dynamic loading. In several cases, such as the cases where the structure experiences low-amplitude vibration, nonlinear structures can be analyzed using linear theory without losing accuracy in the final results. However, there are cases where nonlinear effects cannot be neglected and using linear theory to analyze a nonlinear system results in significant error in final results and as a result, nonlinear effects and therefore nonlinear analysis become unavoidable. In such circumstances, it becomes necessary to detect, localize and parametrically identify nonlinear elements from measured vibration data. In this study, a recently proposed nonlinear identification method is modified. Although the mentioned method is capable of parametrically identifying nonlinearities from measured frequency response functions, the systems which can be investigated by the method are limited to some tight restrictions. In this paper, it is aimed to identify the limitations of the method and then, modify the method so that it can be applied to a wider range of nonlinear mechanical systems.

Nonlinear system identification, Modal analysis, Frequency response function