Investigation on Free-Free Boundary Condition through Structural FRF Measurements for Test-FEA Correlation Process

Abstract

Modal testing is utilized to grasp dynamic properties of system. In testing process, free-free boundary condition is assumed to exclude external effect on system. However, actually, stiffness and damping of support is added to test object, which means disagreement in boundary condition in both experimental and simulation setup. For this reason, it is difficult to perform accurate test-finite element analysis (FEA) correlation and further model updating process. Hence, necessity of investigation on actual free-free boundary condition is emphasized for reliable model calibration. Since boundary condition cannot be modeled theoretically or analytically, investigation through experimentally measured data is required. In this study, for identification of boundary condition, estimation of frequency response functions (FRFs) in original structure is performed by using FRF relations between original structure and constrained structure. Then, dynamic stiffness of boundary condition is identified. To show feasibility and applicability of suggested method, numerical investigation is carried out to continuous finite element beam model.