A Comparison of Three Approaches for the Inversion of Ultrasonic Rayleigh Wave Data into Residual Stress Profiles

Speaker:
Spies, Martin; Fraunhofer IZFP; Germany

Authors:
Mora, P.; Fraunhofer Institute for Nondestructive Testing IZFP; Germany
Spies, M.; Fraunhofer Institute for Nondestructive Testing IZFP; Germany

ID: ECNDT-0376-2018
Download: PDF
Session: Meta Modeling
Room: J2
Date: 2018-06-12
Time: 16:20 - 16:40

In various industries the surfaces of highly-loaded materials and components are specially treated to increase their resistivity to wear, corrosion and stresses. By shot-peening, laser-treatment or other methods residual stresses are deliberately generated. In order to characterize these in the near-surface areas, ultrasonic (Rayleigh) surface waves can be applied.

In this contribution, we study the possibility of retrieving the near-surface residual stress state of a material from ultrasonic Rayleigh wave data. Several formulations that have been proposed in the past are compared on profiles with typical features and scales that are relevant for shot-peening induced pre-stresses. The criterion for the comparison is the capability of the formulations to recover the first 300 m from lower and intermediate frequency data. We have considered simplistic profiles, chosen to schematically reproduce the main features that shot-peening generated profiles usually display, as well as realistic stress profiles obtained from X-ray measurements. We have compared the performance of three reconstruction methods using synthetic Rayleigh wave dispersion data within a limited frequency range, also accounting for the influence of noise on the reconstruction results.

We report on the forward problem via perturbation theory to generate the Rayleigh wave dispersion data in dependence of the stress profile, introduce several formulations for the inverse procedure and finally present our evaluation results. Also, we discuss the approaches in view of practical applicability and with respect to future work.