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Merge pull request #12476 from bwspenc/volumetric_strain

Fix minor issues with documentation of volumetric strain calc
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permcody committed Nov 15, 2018
2 parents ceb977b + 0fd635a commit bf8b5cfa8b05b58b29a5ae237cbb4f2eb9c1342c
@@ -71,7 +71,8 @@ volumetricStrain(const SymmTensor & symm_strain)
{
// Since the strains are logarithmic strains, which are by definition log(L/L0),
// exp(log_strain) = L/L0
// The ratio of the volume of a strained cube to the original volume is thus:
// The ratio of the volume change of a strained cube to the original volume
// (delta V / V) is thus:
// exp(log_strain_11) * exp(log_strain_22) * exp(log_strain_33) - 1
//
// Since eng_strain = exp(log_strain) - 1, the equivalent calculation using
@@ -290,10 +290,10 @@ where $\Delta V$ is the change in volume and $V$ is the original volume.
This calculation assumes that the strains supplied as input ($T$) are logarithmic strains,
which are by definition $log(L/L_0)$, where $L$ is the current length and $L_0$
is the original length of a line segment in a given direction.
The ratio of the volume of a strained cube to the original volume is thus:
The ratio of the volume change of a strained cube to the original volume is thus:
\begin{equation}
\label{eq:volumetric_strain_from_tensor}
s = \exp(T_{11}) * \exp(T_{22}) * \exp(T_{33}) - 1
s = \frac{\Delta V}{V} = \exp(T_{11}) * \exp(T_{22}) * \exp(T_{33}) - 1
\end{equation}
This is the value computed as the volumetric strain.
@@ -146,7 +146,8 @@ volumetricStrain(const RankTwoTensor & strain)
{
// Since the strains are logarithmic strains, which are by definition log(L/L0),
// exp(log_strain) = L/L0
// The ratio of the volume of a strained cube to the original volume is thus:
// The ratio of the volume change of a strained cube to the original volume
// (delta V / V) is thus:
// exp(log_strain_11) * exp(log_strain_22) * exp(log_strain_33) - 1
//
// Since eng_strain = exp(log_strain) - 1, the equivalent calculation using

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