Joint structural parameter identification using a subset of frequency response function measurements

Abstract

The dynamic characteristics of a structure composed of substructures are affected considerably by the properties of the joints. To conduct an accurate dynamic analysis it is first necessary to model the joints accurately. Their structural parameters can then be identified from experiments. This paper proposes a method of identifying joint structural parameters using subset frequency response function (FRF) measurements. For the most part, it is impractical to obtain all the FRFs since the responses at joint related degrees of freedom (dofs) are difficult to measure correctly. Thus, the unmeasured FRFs are estimated from measured FRFs and the joint excluded structure analytical model. Then, assuming a model of joint, the joint structural parameters are extracted from partly measured and partly estimated FRFs. To avoid the influence of measured noise, the output error method is used in an iterative way. The validity and feasibility of the proposed method are demonstrated both numerically and experimentally. The results show that joint structural parameters can be identified accurately even when the measurements are contaminated by noise. Thus, this method can be applied to real structures usually having rotational and inaccessible dofs.