Examples of Using Reference State/Model

Example 1: Reference state in the same model

Here is the "raw" plot - Von Mises stress in a crush tube.

And below is the same plot with the reference state set to #18, which is at t = 0.0085s, in the same model. Remember that:

<data> _displayed = <data> _current - <data> _reference

Therefore, as in this example, negative von Mises stresses can be generated since, in some locations, the stress at an earlier state was in fact greater.

(Incidentally this illustrates that the reference calculation is performed upon the scalar output of the data component computation, not upon its individual tensor components.)

Example 2: Reference state in a different model

In this case the model above has been re-run, but with the section thickness of the crushable elements reduced by 25%. Here we are comparing the results between original and modified models to see what difference this makes.

Obviously rerunning the same model with different section properties does not upset node or element labelling, so exact equivalence between the two analyses is preserved.

Here is the original image, showing contours of "true" displacement magnitude.

Here is the same image, with the displacements in the reference model subtracted from the "true" ones above. The "current" state has been used in the reference model (M1), and this is reported on the plot.

It is not that easy to visualise the differences in shape from the contour plot above, since they are obscured by the gross deformations of the structure.

So in this plot reference geometry has been used for the current (plotting) coordinates as well, showing the difference in displacement between the two models. Effectively this is the undeformed geometry + the difference in displacement between the two models.

Displacements have also been magnified by a factor of 2.5 using MAGNIFY_ DISPLACEMENTS to exaggerate them, making them clearer.