Understanding the impact response of bird strikes on engine blades using a novel wedge-Hopkinson bar system

Bird strikes on engine blades, as a major concern for aviation safety, are complex impact events in which structural responses and bird deformations are coupled. To investigate the slicing process during a bird strike, a wedge-Hopkinson bar (WHB) system was developed to simulate a bird striking an engine blade. The system simplifies the measurement of impact responses by using strain gauges mounted on the bar to detect the signals. Systematic tests were conducted to determine the variation of impact responses using real birds with different masses and velocities. The peak impact force, transferred momentum, equivalent impact force, and time corresponding to the momentum centroid were obtained from the force-time histories to describe the impact process. The results identify the constancy of the normalized peak impact force and the normalized equivalent impact force against the impact velocity. However, the ratio of momentum transfer was found to decrease with increasing velocity. The experimental results for strikes on a wedge and strikes on an oblique planar plate revealed a reduction in the momentum transfer for the slicing state, leading to an impact of lower severity.