Problems of finite element model updating of aircraft based on ground vibration test results

The paper addresses the issues occurring during updating of computational dynamic models of aircraft based on ground vibration test results. These include selection of modal testing methodology based on the analysis of ratio between forced monophase modes and eigenmodes. Structural damping properties can be identified from test results. It is worth noting that the errors in experimental determination of eigenfrequencies are significantly lower than the ones in general masses and damping coefficients. The method for updating elastic properties of finite element models is developed. The mass matrix is assumed to be accurately defined.The objective function is a weighted sum of squares of differences between experimental and calculated eigenfrequencies. The objective function is minimized iteratively. The robustness of the approach with respect to errors in ground vibration test results is investigated. The approach to model structural damping properties based on ground vibration test results is presented. The damping coefficients are computed and chosen as the target ones for each experimentally determined eigenmode. That indicates that in modal coordinates the matrix which consists of these coefficients is diagonal. In order to construct the damping matrix in physical coordinates, the Rayleigh damping model is used. The finite element models of aircraft wing and the aircraft of flying wing type have been updated