First Invariant of Strain

First Invariant of Strain = {yes | no}

Description / Usage

The strain tensor is associated with the deformation of the mesh. Its first invariant is its trace and represents the volume change in the small strain limit. This variable is called IE in the output EXODUS II file.

The permissible values for this postprocessing option are:

yes	Calculate the first invariant.
no	Do not calculate the first invariant.

Examples

Following is a sample card:

First Invariant of strain = yes

Technical Discussion

Computation of the strain tensor \(\underline{E}\) in Goma is discussed on the Solid Constitutive Equation card. The trace is related to the divergence of the tensor, and hence related to a measure of volume change in a material.

It should be noted that the mesh strain is equivalent to the material strain for LAGRANGIAN mesh motion types. For ARBITRARY or TOTAL_ALE mesh motion types (see Mesh Motion card), the strain is strictly related to mesh and not the material.

References

No References.