Modelling of weld inspection by using a paraxial ray-tracing

摘要

The controllability of welded joints is a major industrial challenge to meet the requirements of safety and service life of structures. Nevertheless, in most of austenitic welds, ultrasonic detection performances decrease due to unfavourable wave interactions with microstructure. The understanding of such phenomena requires the use of accurate numerical models. In particular, the ray-based model implemented in CIVA can simulate weld inspections considering heterogeneous and anisotropic materials where the microstructure is described using several homogeneous domains. However, according to the size of the domains and the impedance contrast between neighbouring domains, such weld descriptions may lead to discrepancies between simulations and experimental results. To overcome this difficulty, the extension to smoothly inhomogeneous anisotropic media may be performed by using paraxial ray tracing. In this paper, simulation results obtained with this method are presented and compared to finite elements and experimental data on a well-documented sample representative of a weld located in the primary circuit of nuclear power plants. This work is a part of the MOSAICS project, supported by the ANR (French National Research Agency) which aims at significantly improving the understanding of the influence of the weld structure on the performance of ultrasonic NDT inspections.