Numerical and theoretical prediction of foreign object damage on AM355 simulated blade validated by ballistic impact tests

Foreign object damage (FOD) of aeroengine blade was a critical concern in aeroengine maintenance due to its potential impact on airworthiness. This study investigated FOD of simulated blades made of high-strength steel AM355 through a combination of experiments, finite element (FE) simulations, and theoretical analysis. Firstly, mechanical tests were conducted, including the quasi-static tensile tests at different triaxialities and temperatures, as well as Split-Hopkinson pressure bar (SHPB) tests. Experimental results showed that AM355 was sensitive to strain rate, with a 30.7% increase in yield strength observed at a strain rate of 3864 s⁻¹. Then, a Johnson–Cook (J-C) model with failure criterion was developed and validated through FE analysis. The mechanical performance of AM355 was compared to that of TC4. Lastly, FOD tests accompanied by corresponding numerical simulations were conducted via the laboratory air gun device and the developed J-C model. The predicted notch morphologies and sizes agreed well with experimental observations, with the notch depth linearly increased with the increase of the projectile velocity. Finally, a FOD theory prediction model was developed through a spring-mass model based on Winkler's elastic-plastic foundation. The theoretical predictions were in good agreement with the numerical and experimental results, providing valuable insights for FOD assessment of real aeroengine blades.