Theoretical validation and improvement of the traditional in-situ decoupling method for the multi-coordinate coupled system

Accurate dynamic characteristics of substructures and parameters of the coupling links are important for transfer path analysis and fault diagnosis, since complex mechanical structures often consist of many substructures and moving parts. In this paper, a procedure is derived for revealing relationships between frequency response functions of substructures and that of the multi-coordinate coupled system to theoretically validate the traditional in-situ decoupling method. In order to improve the traditional in-situ decoupling method, simpler expressions for substructure FRFs between internal DOFs and internal /interface DOFs are derived. It is found that the traditional in-situ decoupling method is theoretically equivalent to the virtual decoupling method, which helps clarify the difference between the two decoupling methods.