In this contribution we provide benchmark problems in the field of computational solid mechanics. In detail, we address classical fields as elasticity, incompressibility, material interfaces, thin structures and plasticity at finite deformations. For this we describe explicit setups of the benchmarks and introduce the numerical schemes. For the computations the various participating groups use different (mixed) Galerkin finite element and isogeometric analysis formulations. Some programming codes are available open-source. The output is measured in terms of carefully designed quantities of interest that allow for a comparison of other models, discretizations, and implementations. Furthermore, computational robustness is shown in terms of mesh refinement studies. This paper presents benchmarks, which were developed within the Priority Programme of the German Research Foundation ‘SPP 1748 Reliable Simulation Techniques in Solid Mechanics—Development of Non-Standard Discretisation Methods, Mechanical and Mathematical Analysis’.

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Fictitious domain methods, such as the finite cell method, simplify the discretization of a domain significantly. This is because the mesh does not need to conform to the domain of interest. However, because the mesh generation is simplified, broken cells with discontinuous integrands must be integrated using special quadrature schemes. The moment fitting quadrature is a very efficient scheme for integrating broken cells since the number of integration points generated is much lower as compared to the commonly used adaptive octree scheme. However, standard moment fitting rules can lead to integration points with negative weights. Whereas negative weights might not cause any difficulties when solving linear problems, this can change drastically when considering nonlinear problems such as hyperelasticity or elastoplasticity. Then negative weights can lead to a divergence of the Newton-Raphson method applied within the incremental/iterative procedure of the nonlinear computation. In this paper, we extend the moment fitting method with constraints that ensure the generation of positive weights when solving the moment fitting equations. This can be achieved by employing a so-called non-negative least square solver. The performance of the non-negative moment fitting scheme will be illustrated using different numerical examples in hyperelasticity and elastoplasticity.

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