Dynamic characterization of bolted joints using FRF decoupling and optimization

• An experimental identification method is developed for structural joints.
• FRF decoupling method is used in the identification of joint stiffness and damping.
• The optimization algorithm improved the identified parameters significantly.
• Very good results are obtained for bolted beams.
• The method is found to be promising to be applied to more complex structures.

Mechanical connections play a significant role in predicting dynamic characteristics of assembled structures. Therefore, equivalent dynamic models for joints are needed. Due to the complexity of joints, it is difficult to describe joint dynamics with analytical models. Reliable models are generally obtained using experimental measurements. In this paper an experimental identification method based on FRF decoupling and optimization algorithm is proposed for modeling joints. In the method the FRFs of two substructures connected with a joint are measured, while the FRFs of the substructures are obtained numerically or experimentally. Then the joint properties are calculated in terms of translational, rotational and cross-coupling stiffness and damping values by using FRF decoupling. In order to eliminate the numerical errors associated with matrix inversion an optimization algorithm is used to update the joint values obtained from FRF decoupling. The validity of the proposed method is demonstrated with experimental studies with bolted joints.