Substructure Synthesis via Elastic Media Part I: Joint Identification

A generalised method for the identification of the parameters which describe the dynamic properties of media between coupled substructures using measured FRFs is presented in this paper. The effort is mainly focused on the development of this generalised method and the improvement of its constituent algorithms. The method presented here is more general and more practical in some aspects when compared with most of the previous studies. Using the method, the effective mass, stiffness and damping parameters of a joint element can be identified simultaneously. The FRFs needed in the identification do not have to be measured exactly at the coupling DOFs. The identified results are presented in the form of mass, stiffness and damping matrices, which are convenient for the use in either coupling analysis or model updating. The partitioning algorithm proposed in this paper not only makes the solution more accurate by improving significantly the condition of the FRF matrix but also saves computational time. Two numerical cases are studied using different algorithms. The factors which have been considered in the simulations are: noise contamination and the selection of interior DOFs for FRF measurements. NOMANCLATURE . stiffness matrix of joint 0 mass matrix of joint & viscous damping matrix of joint = impedance matrix of joint T transformation matrix c n number of coupling DOFs f n number of frequency points s singular value L number of internal DOFs X F, force and displacement of assembled system x f, force and displacement of substructures [ I force and displacement of joint