A comparative study on the evaluation of Nonlinear Output Frequency Response Functions (NOFRFs) of nonlinear systems

The Nonlinear Output Frequency Response Functions (NOFRFs) are concepts proposed for the frequency analysis of nonlinear systems, and they have been essential for applications of damage detection in mechanical and civil engineering, etc. Although they have been evaluated by the Least-Square method and the associated linear equations based method, there is little research about the comparative study of these two methods. This paper describes the comparative study of the LS method and the ALEs based method in an application of the NOFRFs based mechanical damage detection. The two methods are respectively introduced and employed to evaluate the NOFRFs, which are capable of indicating the growth of damage in the mechanical system; then, the two methods are compared using the damage evolution results of the corresponding NOFRFs. A series of comparative experiments with different system input amplitudes are carried out. The experiment results expose limitations of both methods for the NOFRFs based damage detection.