Van Mises Stress with Negative Value

Grasshopper Karamba3D
1

Hi I am using the shell view with Van Mises stress for Karamba. I am wondering why it can be negative value. I think the theoretical value for van mises value shoud always be positive.

2020-06-29_14-59-51
2020-06-29_14-59-51712Ɨ725 86.8 KB

2

Hi, Karamba3D outputs the Van Mises stress as a negative number in case the negative value of the second principal stress is larger than the first principal stress. This makes it easier to see whether compression or tension prevails in a region.
ā€“ Clemens

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3

Thanks! Just to confirm, it means the value is the same magnitude as von mises stress, but the positive/negative sign is based on the whether compression/tension prevails the area.

4

Yes, my above description was a bit imprecise: the sign is negative if ABS(sig2)>ABS(sig1), where sig1 and sig2 are the first and second principal stresses. The absolute value of the Van Mises stress is not influenced.
ā€“ Clemens

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