Hyper‐reduced direct numerical simulation of voids in welded joints via image‐based modeling

International audienceDefects such as gas pores can be formed and trapped in the fusion zone during laser welding. These defects can affect significantly the mechanical reliability of the welded joint. Current non-destructive inspection technologies are able to detect micro-voids in a mass production context. Finite Element Analysis can therefore be used to assess the lifetime of an observed component via image-based model-ing. Unfortunately, running a simulation per component entails a huge and generally unaffordable computational cost. In addition, voids do not admit a parametric mod-eling. In this paper, a numerical method is proposed to study the impact of defects on the mechanical response of a welded joint. It is based on model order reduction techniques that decrease the computational cost of each simulation related to an image-based modeling. To tackle the reduction of non parametric defects, a multi scale construction of the reduced basis is proposed, although no scale separation is assumed when computing the mechanical response of the structure. Some empirical modes are representing the structure behavior and other empirical modes are related to the defect-induced local fluctuations. They are then assembled to simulate a defective joint. Assets and limitations of the proposed method are explored through a simplified 2D problem. For the sake of reproducibility, this 2D problem is fully parametric. Finally, a realistic 3D industrial case is presented, where voids geometries have been measured via computed tomography. This 3D problem being non parametric, fluctuation modes must be computed on the fly, once the computed tomography has been performed