On the determination of nonlinear elastic constants for residual stress measurements using Rayleigh waves.

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This work focuses on the evaluation of the acoustoelastic constants (AEC) using Rayleigh waves (RW). These constants represent the state of the microstructure of the material on macroscopic level and are therefore very sensitive to changes in microstructure. They are used as input parameters to determine the residual stress level with acoustoelastic measurements. The comparison of different measurement strategies and the investigation of the possibility to create an in-situ method to measure the AEC near the surface using the nonlinear interaction of two Rayleigh waves are the main contributions of this work. Nonlinear interactions between elastic waves are considered as a prospective mean for in-situ determination of local near-surface nonlinear elastic parameters. The permissible interactions between bulk and surface waves were investigated using an analytical model and then compared with experimental results and available FEM simulations.