Finite element simulation of high-speed soft-body impacts

Abstract

Military fighter aircraft occasionally suffer highspeed collisions with birds, posing a threat to pilot safety and to the structural integrity of the aircraft. An explicit three-dimensional finite element code for transient dynamic analysis, named X3D, has been developed at the University of Dayton Research Institute as a part of a long-term effort to design bird-impact resistant aircrew enclosure transparencies for fighter aircraft. This paper presents the results of a development effort aimed at improving the soft-body finite element models used with X3D to simulate high-speed bird impacts. Techniques are introduced which produce limited liquid-like behavior in tetrahedral bird-model elements, while avoiding numerical problems by deleting elements which exceed an allowable-def ormation measure. Good agreement on surface pressure distributions in rigid-wall impacts was obtained between the analysis and test data from the literature. A technique was explored for reducing the artificial contact force spikes caused by finite element discretization.