FRF based joint dynamics modeling and identification

• Two mathematical models are proposed for the joint in mechanical structures.
• These models are used in the identification of joint dynamic properties.
• The joint properties are obtained using the measured FRF and substructures’ FE model.
• Both methods are evaluated through a numerical FE simulation.
• Both methods can accurately predict the joint dynamics in a modular tool.

Complex structures, such as machine tools, are comprised of several substructures connected to each other through joints to form the assembled structures. Joints can have significant contributions on the behavior of the overall assembly and ignoring joint effects in the design stage may result in considerable deviations from the actual dynamic behavior. The identification of joint dynamics enables us to accurately predict overall assembled dynamics by mathematically combining substructure dynamics through the equilibrium and compatibility conditions at the joint. The essence of joint identification is the determination of the difference between the measured overall dynamics and the rigidly coupled substructure dynamics. In this study, we investigate the inverse receptance coupling (IRC) method and the point-mass joint model, which considers the joint as lumped mass, damping and stiffness elements. The dynamic properties of the joint are investigated using both methods through a finite element (FE) simulation and experimental tests.