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FEA Part 1: Identifying regions of maximum stress in an FEA solution


This video demonstrates techniques for visually determining the locations of high stress in the FEA calculation by using value blanking and color cutoff to display the von Mises stress along the surface.

This example uses a transient FEA data set of a connecting rod created with LS DYNA. The frames per second of the animation are limited to allow us to better analyze the plot. The data file is loaded and you can see all six stress dimensions but no von Mises stress in the variables of the data set.

To calculate the von Mises stress, select Tools > FEA Post-Processing and select Von Mises Stress/Strain as the variable to calculate and use Stress as the variable to derive it from. Once the variable has been added to the data set, toggle on a Contour of the von Mises stress.

At this point you can somewhat see the regions of high stress, however this can be improved. To isolate the areas of interest, hide all pieces except the connecting rod. All the pieces are in the same zone, so Value Blanking must be used. Select von Mises as the blanking variable, and blank when equal to zero.

Engineers are typically only interested in the cells if they go above a critical failure threshold. This can be seen in the current plot, but it can be made more obvious by applying a color cutoff for the contour in the Contours Detail dialog. Select a Cutoff Below 800, which is the critical failure threshold. Turning on Translucency can also help give you a more complete view of the part.

Further improve the visualization by selecting Frame > 3D Multi Frames… This will automatically create a set of Frames at different orientation views.

When animating you will see that at most time steps the von Mises stress level is under the critical threshold, however you can now identify the two time steps and areas where it surpasses this number.

Another way to analyze the part is to use frame linking with value blanking to further isolate the regions of high stress. In this view you can completely remove the regions that satisfy the design criteria while still providing context for the part as a whole.

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