2018 Volume 67 Issue 9 Pages 861-868
Fan blades and turbine blades in a jet engine are seriously damaged by high velocity impingements of bard, dust, volcanic ash, and metallic fragment, etc. onto these surfaces, which is called foreign object damage (FOD). Finite element method (FEM) is, generally, used for estimation of indent size and residual stress distribution resulting from the FOD caused on a metallic substrate. In order to estimate the FOD of a metallic substrate more easily, an estimate equation for the FOD (EFOD) is developed from a simple theoretical model based on energy conservation under high velocity impingement of a spherical particle onto a metallic substrate. In this study, a radius of crater formed on the surface was focused on. The EFOD was formulated based upon energy conservation before and after impingement phenomena. The Johnson-Cook constitutive equation was also employed to introduce effects of plastic strain and plastic strain rate, i.e. work hardening and strain rate hardening, into the EFOD. The plastic strain and plastic strain rate developed into a substrate were evaluated using FEM and formulated as functions of impact velocity, radius of particle and radius of crater. The validity of the EFOD was checked by comparing with the results of both FE analysis and experiment. It was confirmed that the radius of crater estimated by the EFOD was in a good agreement with that obtained by the FE analysis. Furthermore, the experiment using a single particle impact testing system showed that the EFOD can estimate the radius of crater on a SS400, C1020 and A1070 substrates accurately.
