THE NONLINEAR OUTPUT FREQUENCY RESPONSE FUNCTION AND ITS APPLICATION TO FAULT DETECTION

In this paper, the new concept of Nonlinear Output Frequency Response Functions (NOFRFs) (Lang and Billings, 2005) is introduced. The potential of the use of the NOFRFs in detecting faults is demonstrated through studying the sensitivity of the NOFRFs to the change of stiffness ratios of a bilinear model which has widely used to model various nonlinear phenomena in engineering practices, including the presence of cracks in structures. The results show that the higher order NOFRFs are significantly sensitive to the stiffness ratio. This research study establishes an important basis for developing nonlinear approaches to the detection of faults in mechanical structures.