Aircraft Birdstrike Simulation Using Smoothed Particle Hydrodynamics

Abstract

Bird strike incidents are not uncommon and cause significant flight safety threats to aircraft operations. An aircraft must show compliance with “continued safe flight and landing” requirements following specified types of high energy bird impact (See FAR 25.571/25.631). A bird strike is classified as a high velocity soft body impact, because the stresses which are generated in the contact region are significantly greater than the strength of the bird but lower than the strength of the impacted structure. High deformability of the impactor (bird) causes spreading of the impact load over a certain area of the structure that requires the use of special strain rate dependent material model s. If the structure is deformable, the impact load depends on the structural response that, in turn, depends on the impact load. During the design process, a means to predict the structural behavior on a birdstrike event has to be employed to size the structure. Final certification is usually made by tests. To simulate this phenomenon, the soft impactor body is modelled using smoothed Particle hydrodynamics. An equation of state is used to provide a hydrodynamic material model, it describes the pressure as function of specific internal energy and density. Aircraft (Target) structure is modeled using a Lagrangian Finite Element Mesh. Large displacements and material plastic behavior (strain rate dependant) are considered This paper presents the bird strike simulation methodology used at FAdeA SA based on the Smooth Particle Hydrodynamics technique. Examples of analysis models developed using ABAQUS Explicit are presented.