A method to calculate the parameters for each instantaneous and relative instantaneous screw axis in an arbitrary rigid multibody system is presented. At first a kinematic analysis is performed which calculates the displacements of all nodes and the rotation of each body. In the next step the displacements of the nodes and the rotation of the bodies are used to calculate the instantaneous screw axis of each body. With the information on the instantaneous screw axes the instantaneous relative screw axes can be computed too. An example of the calculation and the visualization of the instantaneous screw axes is given.

A method to consider nonlinear multipoint constraints in finite element analysis based on a master‐slave elimination scheme operating at the global level is presented. We focus on systems with nonlinear constraints in which the number of constraints is of the same order of magnitude as the number of degrees of freedom. Therefore, we rely on the master‐slave elimination which gives us the huge benefit of drastically reducing the problem size. In the literature the presented master‐slave elimination schemes for linear constraints are based on the manipulation of the system equations (global level), but the master‐slave elimination schemes for nonlinear constraints are based on manipulation of the element formulation (local level). In contrast to that we use a global approach for which the nonlinear constraints are applied directly on the system equations in analogy to linear constraints. Thus, the method is independent of the underlying element formulation and the type of constraints which makes it more flexible.

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