3D modelling of ultrasonic testing in austenitic welds

Regulatory requirements enforce a volumetric inspection of welded components of nuclear equipments. However, the multi-pass austenitic welds are characterized by anisotropic and heterogeneous structures which lead to numerous disturbances of the ultrasonic beam. As a consequence, there is a great need for developing modelling codes taking into account complex 3D configurations in order to improve the prediction of the ultrasonic propagation and then to optimize the UT inspections. In this purpose, the MOSAICS project supported by the ANR (French National Research Agency) aims at developing several complementary codes: finite elements code ATHENA, semi-analytical models included in CIVA software, hybrid model combining the two approaches. For validation purpose, experimental data have been acquired on representative mock-ups containing calibrated defects. Moreover, a task of the project is dedicated to the weld description as modeling input data. An ultrasonic device is being designed in order to simultaneously determine the elastic and attenuation coefficients of the wave in an anisotropic material. Furthermore, an inversion process based on ultrasonic data is being developed to optimize a weld description firstly derived from the MINA model. The purpose of this paper is to give a half-project overview on the results obtained in the various tasks of MOSAICS.