New Simplified Dynamic Modeling Method of Bolted Flange Joints of Launch Vehicle

The bolted flange joint is an important source of nonlinearity in dynamical analysis of launch vehicles, which will lead to both longitudinal and transversal responses simultaneously subject to transversal dynamic loads, and may result in the failure of the connection structure. In this paper, a novel simplified dynamic modeling method via structural static analysis is proposed to simulate dynamical response of nonlinear bolted flange joints of launch vehicle, in which only static analysis of the detailed finite element model or static experiment is used for parameter identification of the model. Two types of nonlinear springs are designed for different tensile and compressive stiffness of the bolted flange joint, which affect longitudinal dynamic behaviour of the connection, and a shear spring is used to modify the transversal stiffness. The sections of launch vehicle are modeled as linear beams for efficiency. Effectiveness of the proposed modeling method is confirmed by a typical connection structure, bolted flange connected cylindrical shells, whose finite element models are verified with dynamic experiments. Superiority of the simplified dynamic model from the proposed method is demonstrated by comparing with the previous simplified model. The connection structures with different numbers of bolts are studied, and most of the dynamic responses calculated from the proposed model agree well with those from the finite element model. The coupling vibration of the connection structure is predicted successfully, in which longitudinal response of the structure is excited by the transversal load.