Post-Critical Analysis
Technical Article
In the case of a post-critical failure, a substantial change in the geometry of a structure occurs. After reaching the instability of the equilibrium, a stable, strong position is reached again. The post-critical analysis requires an experimental approach. It is necessary to manually load the structure in increments step by step.
Example
In the following, the punch-through problem is shown. The structural component can be thought of as a flat roof that is subjected to pressure from the outside. If the pressure is increased slowly, it first appears that the load is absorbed by a compressive stress and transferred to the support.
Figure 01 - Internal Forces According to Large Deformation Analysis
For a certain size of the compression load, the system becomes unstable, there is a breakdown.
Figure 02 - Unstable System: Post-Critical Failure
Figure 03 - Post-Critical Analysis
Then, the load can be increased again, which is then absorbed mainly by tension in the component.
Figure 04 - Post-Critical Analysis: Increasing Load
The second-order analysis can basically not cover the punch-through problem due to the linearization of the description of the deformation geometry.
Further information and examples can be found in [1] and [2].
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