Transient three dimensional finite element analysis of a bird striking a fan blade

Abstract

A comprehensive three-dimensional nonlinear finite element analyses were carried out to examine the effects of the geometry and the incidence angle of canonical 4-lb bird striking a stationary fan blade using LS-DYNA. Three aspects of the work were accordingly examined. The first was concerned with the modeling framework used. The second with the constitutive law that governs the behaviour of the bird. The third was concerned with the influence of the geometry and the angle of incidence of the bird on the integrity of the blade. This article combines and extends the earlier works on both the Lagrangian modeling methodology (Mao et al. AIAA J. Aircr. 44(2), 583-596, 2007) and the bird geometry studies (Meguid et al. 2008) in systematic and integrated manner. Both the bird and the blade were simulated in a Lagrangian framework. Furthermore, the homogenized fluidic constitutive equation of the bird follows the Brockman hydrodynamic model, while the blade is modeled as a viscoplastic material of the Perzyna type. The study focused on the three most-frequently used configurations in the literature; namely, hemispherical-ended cylinder, straight-ended cylinder, and ellipsoid, at various length-to-diameter aspect ratios. The results show that the initial contact area between the bird and target in the early phase of the impact event would have a significant effect on the peak impact force. Normal incidence results in maximum impact forces and plastic strains leading to severe deformation. For the case where the incidence angle is equal to or larger than 60°, the impact forces are significantly reduced and the blade deformation remains within the elastic range. The maximum impact force and the resulting plastic strain are not merely governed by the size of the bird but also its density. © 2007 Springer Science+Business Media B.V.