Abstract
Fan blades and turbine blades in a jet engine are seriously damaged by impingements of bard, dust, volcanic ash, etc. onto these surfaces, which is called foreign object damage (FOD). Finite element method (FEM) is, generally, used for estimation of the FOD caused on a metallic substrate or on a thermal barrier coating. In this study, 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 normal impingement of a spherical particle onto a metallic substrate. In the EFOD, amount of the FOD was represented by a radius of crater formed on a substrate. The Johnson-Cook constitutive equation was 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 generated on 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 confirmed by comparing with the results of FE analysis and experiment. The radius of crater estimated by the EFOD was in a good agreement with that obtained by the FE analysis. Furthermore, the impact experiment confirmed that the EFOD can estimate the radius of crater on a SS400 substrate, although it was difficult to estimate the radius of crater on a C1020 substrate using the EFOD.
