The effect of irregular particle shape and surface deformation on particle bounce, Part I: Characterizing particle geometries and induced plastic deformation on surfaces

Abstract

Erosion of in-engine machinery from the ingestion of atmospheric particulates has been a longstanding problem in the aviation industry. Minerals comprise most atmospheric particles, but their complex characteristics make reproducing and interpreting in-engine particle-driven erosion challenging. Crushed quartz is a commonly used impactor material in engine durability tests, but its jagged morphology renders its dynamical behavior difficult to reproduce in computational and analytical models. This work demonstrates that in the case of a particle-surface impact, the many global-scale geometric parameters of a jagged particle can be reduced to one unifying robust metric that is derived from its local geometric features. We additionally introduce a methodology to semi-quantitatively measure characteristics of particle-induced plastic deformation of flat surfaces. This was implemented on a series of particle impact experiments conducted using a free jet rig in which quartz-laden air was accelerated toward coupons of five different metal alloys at nominal speeds of $60m/s$ and $120m/s$, with two impact angles of ${30}^{°}$ and ${90}^{°}$. This was done such that the extent of impact-induced erosion could be analyzed for a unique particle speed, angle of impingement, and target material combination. Correlations of average crater volume show that particle-induced plastic deformation is inversely proportional to the coupon's compressive yield strength. We further show a correlation between particle incidence angle, impact velocity, and crater volume, which is consistent between each material type. The proposed methodology and data are ideal for validating particle bounce models, which is demonstrated in this study's companion paper.