Using Updated and Expanded Data to Estimate the Unmeasured Rotational Data of a Bolted Structure

Abstract

For frequency-based substructuring (FBS) to be accurate, translational and rotational data must be available at the connection points between substructures. However, obtaining rotational FRFs from experimental modal analyses is very difficult in practice. In this paper, an alternative method for estimating rotational FRFs is proposed using an approximated simplified finite element model (ASFE), modal updating, and mode expansion. The proposed approach was demonstrated on an assembled structure consisting of an irregular plate (test model) and a simple beam (FE model). The SEREP method was used to augment the translational and rotational FRFs to the updated ASFE mode shapes. The expanded rotational FRF of the test model was validated with the measured rotational FRF obtained from a piezoelectric direct rotational accelerometer. The results showed that the proposed approach for FBS correctly predicted the experimental FRF of the assembled structure with 90% accuracy. The FBS method is no longer dependent on the experimental rotational FRF, which is very difficult to measure with the methodology presented here.