Analysis Of The Vibration Characteristics Of The Gun Bay Structure Under Impact Loading

Gun-bay is the fuselage structure of the area where aircraft gun connected to fuselage. The situation of the force acting on gun-bay structure is more complex when aircraft is flying or aircraft gun is shooting. Gun-bay structure is not only under the condition of irregularly vibration which engine working and force of aerodynamic cause, but also under the condition of intensively impact when aircraft gun shooting. The gun-bay structure's frequency and modal as well as the dynamic response that gun-bay structure at the condition of aircraft gun shooting is needed to study hard. So that, the design of gun-bay structure can meet the aircraft structure design criteria and the gun-bay dynamic strength.In this paper the gun-bay structure of a fighter is studied. First, the geometric model of gun-bay structure in CATIA is put into the software ANSYS. Using ANSYS , the complicated gun-bay structure is predigested a simple gun-bay structure finite element model . This finite element model is assembled with some shell elements, beam elements, and a few three-dimensional solid elements. In order to make the model simple, some not important components in gun-bay structure are deleted. Because of the thin thickness, the skin of gun-bay structure, the frame plane, the oil tank floor, and the plane that hold up the smoke of aircraft gun is considered as shell element. The components that strengthen the skin and the frame plane are considered as beam element. Some irregularly body on gun-bay structure girder and the critical components are considered as three-dimensional solid element.Block Lanczos algorithm is used to analyze the modal of gun-bay structure. Through the process of the modal analysis, the first 20 natural frequencies and modal are gained. At the same time, the vibration characteristics of the gun-bay structure are analyzed under the first 6 frequency. The results indicate that the characteristic of the vibration of the whole gun-bay structure accords the general one of the vibration of the common lengthways shell structure. But because of the complexity of the structure, the results also represent many the local vibration characteristic. The local vibration of the LSF-0412-20, LSF-0412-30 frame and the LSF-0412-11-y,LSF-0412-11-z oil tank floors has large displacement. So these areas are the ones...