Mixed dimensional isogeometric FE-BE coupling analysis for solid–shell structures

In this paper, the collocation-based isogeometric boundary element method (IGABEM) is combined with the isogeometric Reissner–Mindlin shell elements to conduct the mixed dimensional solid–shell coupling analysis. On the basis of taking advantages of the geometric smoothness and exactness of isogeometric analysis (IGA), this method can reduce the computational scale of the solid part and eliminate the procedure of constructing analysis-suitable volumetric discretizations. In addition, this method only needs to provide the surface CAD (computer-aided design) meshes of the whole coupling model, so it has great potential in achieving close link with CAD systems. For the coupling implementation, the stiffness formula of BE subdomains is formed by condensing the unknown tractions, which simplifies the implementation of coupling constraints. That is to say, only the displacement compatibility equations on the interface are required, without explicitly establishing the traction equilibrium conditions. Two coupling approaches are developed and studied. One is the collocation-based direct strict kinematic coupling based on the deformation hypothesis of the shell across the section, and another is the weak coupling formulation in an integral sense based on work equality. The accuracy and convergence properties of the presented coupling method are investigated through numerical examples including a complex impeller blade.