Third order elastic constants and Rayleigh wave dispersion of shot-peened aero-engine materials

Abstract

Mechanically high stressed components used in aero-engines are made of highstrength alloys like IN718 and Ti6246. Additionally, they are surface treated by shot-peening. This introduces compressive residual stress to minimize the material's sensitivity to fatigue or stress corrosion failure mechanisms, resulting in improved performance and increased lifetime of components. Besides that, cold work is introduced in an amount depending on the peening parameters. To determine the remaining lifetime of critical aero engine components, a quantitative non-destructive determination of compressive stresses is required. It was shown that the surface treatment of aero engine alloys can be characterized by broadband Rayleigh wave dispersion but the relative contributions of compressive stress and cold work remained an open point. The present paper presents measurements of the second and third order elastic constants (TOEC) of IN718 and Ti6246. By that the stress contribution to the surface wave dispersion can be estimated.