Abstract:
In this paper, a new concentrated mass-bent beam model of aircraft pylon is proposed, which is an effective mode reduction method for the analysis of vibration characteristics of continuous structures of pylon. Firstly, according to the periodic structure and the stress characteristics of pylon structure under actual working conditions, pylon structure is simplified into a concentrated mass-bent beam model which consists of 12 mass elements and 11 beam elements in series by using the concentrated mass method. The two simply supported boundary conditions reflect the true constraints of pylon-wing front and rear lifting points. The transfer equation and characteristic equation of the model are established based on the transfer matrix method. After using the parameter sensitivity method to correct and optimize the uncertain parameters of bending stiffness, the effectiveness of pylon concentrated mass-bent beam model is verified by comparing with the lower order natural frequencies of the finite element model. On this basis an engine is connected to the front and rear lifting points of pylon-engine through the installation section as the basic excitation, and engine-pylon concentrated mass-bent beam coupled model is established. Transfer matrix method is applied to study the natural frequency of the coupled model and the vibration response of pylon structure under the take-off, cruise and flight idle conditions of the engine. The vibration envelope lines of pylon structure mass elements under different conditions and different times and the vibration response of the representative mass element are obtained. In addition, the effectiveness of the new model is further verified by comparing with the finite element method. The research results provide theoretical support for the vibration reduction design of the pylon structure.