Direct model optimisation for data inversion. Application to ultrasonic characterisation of heterogeneous welds

Numerous multipass welds in austenitic stainless steel are made on the primary circuits of nuclear power stations. The heterogeneous anisotropic nature of these welds causes disturbance to ultrasonic propagation. Simulation is a useful tool when attempting to understand physical phenomena. With this objective, a finite element code called ATHENA was developed. Sufficiently realistic modelling of the material is proposed by the Modelling anIsotropy from Notebook of Arc welding (MINA) model, which determines the orientation of the weld grains. Optimisation by inversion of the MINA model is proposed in this study. The results validate the strategy and open perspectives regarding use on real data.