Joint stiffness identification using FRF measurements

In this research, an identification method for joint parameters has been developed by using the substructure synthesis method and frequency response functions (FRFs). A matrix form for the joint model was proposed. Identifying the joint parameters of a beam screwed down at one of its end was conducted. Only two measurement points were used in the experiment. The simulated results of the FRFs of the constrained beam with the properly identified joint parameters agree with the experimental results very satisfactorily. The accuracy of the identified results is strongly sensitive to the parameters. The rotational stiffness of the screw joint is identified to be located in the sensitive region, so the identified result of the rotational stiffness is very good. However, the less accurate results for the translational stiffness located in the insensitive region do not affect apparently the accuracy of the simulated results. The cross-coupled term between the translational and rotational stiffness in the joint model was identified, which greatly improved the accuracy of the simulated FRFs in higher frequency regions.