Stability analysis

Normally there is a clear correlation between the external load and the deformation of a structure. In some special cases, however, this uniqueness is only given up to a certain limit load. The aim of the stability analysis is to determine the ultimate limit state of a structure. With flat, thin structures this behavior is called buckling, with thin rod-shaped components it is called kinking. Accordingly, this simulation type is also called buckling or kinking analysis.

There are basically two ways to perform a stability analysis. In the first case, the buckling load of a structure is solved as an eigenvalue problem. The results obtained tend to be too optimistic, since real geometries always deviate from the ideal geometry and therefore reach the point where structural failure occurs earlier. Furthermore, no nonlinearities can be taken into account with this method.

Therefore, the second approach of a nonlinear stability analysis provides much more realistic results. Strictly speaking, this method is nothing more than a non-linear static analysis with large deformations in which the load is gradually increased. As a result, all possible nonlinearities can also be taken into account in the model. If the simulation is load-controlled, the limit load is reached when no more convergence takes place. Small variations in geometry and load directions deviating from the ideal state also allow the sensitivity to manufacturing and assembly-related interference to be investigated.

Computation time / model size

Depending on the modeling, a nonlinear stability analysis can become very computationally time-consuming, as the simulation is deliberately brought to the point where a divergence occurs. In this limit load range, relatively many small time steps are necessary for the convergence search. If the step size is selected too large, the maximum load cannot be determined with sufficient accuracy.

Relevance

Stability analysis is important in many areas of technology, especially in the design of structural steel frameworks.