Experimental and analytical modelling on aeroengine blade foreign object damage

Aeroengines in operational service were susceptible to the ingestion of small, hard particles, resulting in foreign object damage (FOD) on rotating blades. Such particles impacting the blade edge at a velocity up to about 350 m/s yielded millimeter-sized damages, which might result in crack initiation and became the primary life-limiting factors. In this study, experimental and analytical efforts were undertaken respectively to examine the effect of spherical foreign impact on simulated blade edge. For the experiments, a total of 94 laboratory air gun tests were conducted under 17 different conditions, with impact energy ranging from 0.05 J to 16.01 J. The resulting distribution zone of FOD, which continuously characterized the damage sizes, showed that the raised impact energy would boost FOD size. The macroscopic morphology of FOD exhibited three distinct types of transformations. Additionally, FOD prediction models about impact velocity and impact energy were developed using the linear and power formulas, respectively. These models demonstrated good accuracy, with the linear method achieving a maximum error of 11.7 %. For theoretical analysis, a spring-mass system based on Winkler's elastic-plastic foundation theory was employed to model FOD. It was found that the predicted results from this model were in good agreement with the experimental measurements. The predicted results could serve as the upper and lower bounds within the damage space to envelope the test results, providing a reference for fatigue life assessment of the aeroengine blades.