Transient Dynamics of Slicing-Impact Loading on Jet Engine Fan Blades during a Bird-strike Event

Based upon numerous field events involving bird-strikes on aircraft propulsion system components, the engine manufacturers have long recognized the need for better understanding and insight in the physics of slicing action for analytically predicting the damage to the fan blade. A medium or large size bird being ingested in a running engine with aircraft velocity in the range of 100-120 m/second, essentially during the take-off time, is capable of doing a catastrophic damage to multiple blades on the fan rotor. The slicing action during oblique impact at the thin leading edge of the metal airfoil can cause non-linear plastic deformation, which is highly transient in nature with peak magnitude becoming large enough to block the airflow to an extent that can result into engine stall. Precise analytical modeling of an actual bird-strike event on a jet engine fan blade is a very difficult and highly challenging problem in the area of transient nonlinear dynamics. LS-DYNA® offers many different options such as Lagrangian bird, SPH bird as well as ALE approach to simulate the dynamic loading on the fan-blade, which is generally localized at the sharp leading edge and peaks usually within 0.1 milliseconds of initial contact. The present paper provides a historical and current perspective from the modeling considerations of fan blade airfoil during the design and development cycle and its implementations in LS-DYNA simulations for accurately determining its dynamic response under bird-strike.