LAUSR

The paper presents a multiscale model based on a FEMxDEM approach, a method that couples Discrete Elements at the micro-scale and Finite Elements at the macro-scale. FEMxDEM has proven to be an effective way to treat real-scale engineering problems by embedding constitutive laws numerically obtained using Discrete Elements into a standard Finite Element framework. The proposed paper focuses on some numerical open-issues of the method. Given the problem non- linearity, Newton’s method is required. The standard full Newton method is modified by adopting operators different from the consistent tangent matrix and by developing ad-hoc solution strategies. The efficiency of several existing operators is compared and a new, original strategy is proposed, which is shown to be numerically more efficient than the existing propositions. Furthermore, a shared memory parallelization framework using OpenMP directives is introduced. The combination of these enhancements allow to overcome the FEMxDEM computational limitations, thus making the approach competitive with classical FEM in terms of stability and computational cost.