Bird strike analysis of jet engine fan blade

Bird strike, also known as avian ingestion, is the collision between a bird and an aircraft. Bird strikes have always been a cause of worry in the aeronautical industry: Aircraft both old and new have suffered from bird strikes. Jet engine ingestion occurs when the bird hits the jet engine of an aircraft and gets sucked in. Given that the fan blades rotate at a high rpm, bird strike on a fan blade causes its displacement into the adjacent blade. This leads to a cascading failure, wherein the entire system fails, thereby resulting in a lot of damage. In this article, we intend to investigate the construction of the fan blade and eventually strengthen its' resistance to bird strikes. Over the years, designers have come up with several ways to effectively model the birds in reducing the overall fatigue caused in the blades. Several bird models were proposed, each more effective than the other. A bird could be thought of as behaving like a fluid when undergoing high speed impact. Some of the models propose an elastic-plastic deformable body with low value of yield point and small hardening, while others consider hyper-elastic (rubber-like) body, jelly-like body which easily splatters over the whole blade, a liquid body or even particles of solid body. In this article, the impact of a bird strike on a jet engine fan blade is analyzed and emphasis is not on just the bird model. Stress and deformation patterns will also be investigated to suggest more robust fan designs to lessen bird strike impact. Investigations conclude that the maximum pressure is expected at the center of impact, on the blade. The suitable bird model selected for analysis is a hyper-elastic (rubberlike) body, which resembles the impact of birds most closely, as they splatter off once they collide. The blade and the bird are initially modeled in CATIA. AUTODYN-3D was used for the collision simulation. The bird was modeled as a cylinder with hemispherical ends. Material selection for the birds to accurately correspond to the actual models was challenging. In order to replicate the behavior of the actual bird during strike, rubber (density =1000 kg/m3) was selected as the bird material. This was reflected in the way the bird behaves in the impact. Titanium Alloy (density = 4420 kg/m3) was chosen for the blade material. The bird was given a translational velocity of 150 m/s and the blade rotated at 2500 rpm. These values were chosen to replicate a worst-case scenario. The resultant stress and deformation patterns of the blade and bird were obtained. These patterns were compared with real bird-strike scenarios and available industry test data to establish the authenticity of the simulation.This article enables us to locate points of maximum deflection / stresses. By doing so, we can conclude whether the blade will undergo failure or not, by comparing these stress values with the Ultimate Strength of the blade material.