Model updating using antiresonant frequencies identified from transmissibility functions

Abstract

Traditional model updating methods make use of modal information as natural frequencies and mode shapes. Natural frequencies can be accurately identified, but this is not the case for mode shapes. Mode shapes are usually accurate to within 10% at best, which can reduce the accuracy of the updated model. To solve this problem, some researchers have proposed antiresonant frequencies as an alternative to mode shapes. Antiresonances are identified easier and more accurately than mode shapes. In addition, antiresonances provide the same information as mode shapes and natural frequencies together. This article presents a new methodology to identify antiresonant frequencies from transmissibility measurements. A transmissibility function represents the relation in the frequency domain of the measured response of two points in the structure. Hence, it does not involve the measurement of excitation forces. These antiresonances are used to update the numerical models of two experimental structures: An 8-dof mass–spring system, and an exhaust system of a car. In both cases, the algorithm is tested first to update the numerical model of the structure, and second, to assess experimental damage.