Characterization of Surface Treated Aero Engine Alloys by Rayleigh Wave Velocity Dispersion

Abstract

Investigation of local rayleigh wave velocity dispersion due to surface residual stress AIP Conf.ABSTRACT. In aero engines mechanically high stressed components made of high-strength alloys like IN718 and Ti6Al4V are usually surface treated by shot-peening. Other methods, e.g. laserpeening, deep rolling and low plasticity burnishing are also available. All methods introduce compressive residual stress desired for minimize sensitivity to fatigue or stress corrosion failure mechanisms, resulting in improved performance and increased lifetime of components. Beside that, also cold work is introduced in an amount varying from method to method. To determine the remaining life time of critical aero engine components like compressor and turbine discs, a quantitative non-destructive determination of compressive stresses is required. The opportunity to estimate residual stress in surface treated aero engine alloys by SAW phase velocity measurements has been re-examined. For that original engine relevant material IN718 has been used. Contrary to other publications a significant effect of the surface treatment to the sound velocity was observed which disappeared after thermal treatment. Also preliminary measurements of the acousto-elastic coefficient fit into this picture.

Nonlinear interaction of Rayleigh waves in isotropic materials: Numerical and experimental investigation

“…The perturbation theory formulation described in 2.2.1 provides an estimation of the efficiency of generation of a bulk wave of the form (11). On the other hand, LDV measurements and reasonable-size FEM simulations can only provide wave fields at the surface and in a thin surface layer, correspondingly, where the wave field generated by nonlinearity did not yet evolve into a plane wave.…”

“…The acoustoelastic effect for Rayleigh waves has been theoretically described [6,7] and experimentally proven [8,9]. However, surface layer stress estimation by the acoustoelastic effect is a challenging and not yet successfully implemented approach [10,11,12,13].…”

“…For relevant titanium-and nickel-based superalloys, only a few sets of AEC values have been published, which are not fully consistent with each other [11,12,13,15,16]. Moreover, the AECs themselves are known to vary with plastic deformation [10,17] and depth [14,17].…”