| The Federal Aviation Administration (FAA) has been conducting drop tests since the late 1980's to determine the impact responses of aircraft structures under severe but survivable crash conditions. The knowledge learned in each drop test, however, is limited to one specific test condition. The prohibitively high cost of conducting actual impact tests makes it necessary to develop a modeling and simulation capability. Simulations may be used to study numerous issues in detail, to support the design of improved crashworthiness airframe structures. Crashworthiness simulations of aircraft, unlike those that are routinely performed in the automotive industry, are much more difficult to perform due to the complexity of the airframe structure and the unavailability of proprietary information. In this study, a structurally realistic finite element model was developed to numerically simulate the drop test of a Boeing 737 fuselage section that was conducted at the FAA William J. Hughes Technical Center in November 2000. The model incorporated both geometric and material non-linearity, and used an explicit-integration algorithm to solve for the dynamic responses. Emphasis has been placed on predicting the dynamic response of the structure, including the overall deformation of the fuselage, the acceleration-time histories, and the load-time histories of key structural components. It was determined that the fuselage frame and the under-floor luggage play the most important roles in energy dissipation during impact, and that the friction between impacting surfaces markedly affects the deformation of the entire structure. The effect of luggage stiffness, friction between fuselage and platform, and material degradation due to fatigue and corrosion were also examined. Simulation results compared well with those recorded during the drop test, indicating that the optimized finite element model that was developed is suitable for use in crashworthiness studies of aircraft. The model was then extended to study various other impact conditions. |
