Estimation of stresses in 1D structures via inverse wavenumber analysis

The ANR ITHERATE project proposes to develop identification procedures of residual stresses in additive manufacturing via in-situ and non destructive methods using the wide band wave response of structures. This work presents a proof on concept on one-dimensional waveguides, as a preliminary results to more complex configurations. An original experimental setup is implemented using a cylindrical lens to optically amplify the vibrations of the structure in the transverse direction, allowing to resolve the wave propagation with a high-speed low-resolution camera. The dispersion of the wave velocity with the frequency, obtained via high-resolution wavenumber analysis (HRWA), is compared to predictions given by the acousto-elastic theory. In particular, the effects of the quasi-static initial stress and the elasticity of the material can be separated and estimated seperately via an inverse method that is independent from the boundary conditions and applied loads. Interestingly, this wave-based estimation does not necessitate an a-priori knowledge of the material constitutive law, overcoming the limitations of most stress estimation techniques of the state of the art, that are based on a measurement of the strain. Finally, perspectives for the generalization of the method to more complex situations, as plates under thermal loads, will be presented.