# [cig-commits] r18601 - in short/3D/PyLith/trunk/doc/userguide: materials tutorials/3dhex8/quasistatic

willic3 at geodynamics.org willic3 at geodynamics.org
Sun Jun 12 15:59:09 PDT 2011

Author: willic3
Date: 2011-06-12 15:59:09 -0700 (Sun, 12 Jun 2011)
New Revision: 18601

Modified:
short/3D/PyLith/trunk/doc/userguide/materials/materials.lyx
short/3D/PyLith/trunk/doc/userguide/tutorials/3dhex8/quasistatic/quasistatic.lyx
Log:
For materials.lyx:
Added explanation of state variable used to hold initial-stress-zz for
2D viscoelastic models.
Tidied up a couple of equations.
Updated section on initial state variables.
For tutorials:
Added sentence at the beginning mentioning HDF5 output.

Modified: short/3D/PyLith/trunk/doc/userguide/materials/materials.lyx
===================================================================
--- short/3D/PyLith/trunk/doc/userguide/materials/materials.lyx	2011-06-12 21:39:03 UTC (rev 18600)
+++ short/3D/PyLith/trunk/doc/userguide/materials/materials.lyx	2011-06-12 22:59:09 UTC (rev 18601)
@@ -1604,6 +1604,22 @@
Note that both 2D and 3D viscoelastic models are described, but we present
below only the 3D formulations.
The 2D formulations are easily obtained from the plane strain definition.
+ The one aspect of the 2D formulations that is different is the specification
+ of initial stresses.
+ Since 2D models only have three tensor components, it is not possible to
+ specify the normal stress in the out-of-plane direction (
+\begin_inset Formula $\sigma_{33}$
+\end_inset
+
+), which is generally nonzero.
+ To allow for the specification of this initial stress component, an additional
+ state variable corresponding to
+\begin_inset Formula $\sigma_{33}^{I}$
+\end_inset
+
+ is provided.
+ Note that this is not an issue for the 2D elastic models, since this initial
+ stress component is not needed.
\end_layout

\begin_layout Standard
@@ -2452,7 +2468,7 @@
, we obtain
\begin_inset Formula
$$-\underline{S}\left(t\right)=2\mu_{tot}\left[\mu_{0}\underline{e}\left(t\right)+\sum_{i=1}^{N}\mu_{i}\exp\frac{-t}{\lambda_{i}}\left(\underline{e}_{0}+\intop_{0}^{t}\exp\frac{t}{\lambda_{i}}\underline{\dot{e}}\left(\tau\right)\, d\tau\right)-\underline{e}^{I}\right]+\underline{S}^{I}\,.\label{eq:29} +\underline{S}\left(t\right)=2\mu_{tot}\left\{ \mu_{0}\underline{e}\left(t\right)+\sum_{i=1}^{N}\left[\mu_{i}\exp\frac{-t}{\lambda_{i}}\left(\underline{e}_{0}+\intop_{0}^{t}\exp\frac{t}{\lambda_{i}}\underline{\dot{e}}\left(\tau\right)\, d\tau\right)\right]-\underline{e}^{I}\right\} +\underline{S}^{I}\,.\label{eq:29}$$

\end_inset
@@ -5223,11 +5239,14 @@
In a more general sense, initial values for state variables may be used
to provide values that are consistent with any set of conditions that occurred
prior to the beginning of a simulation.
- The current release of PyLith allows the specification of initial stresses
- and strains for elastic materials, but only initial stresses for anelastic
- materials.
- The next release will support initial stresses, strains, and state variables
- for all materials.
+ The current release of PyLith allows the specification of initial stresses,
+ strains, and state variables for all materials; however, the initial state
+ variables are not presently used.
+ The reason for this is that the present version of PyLith always performs
+ an elastic solution prior to performing the time-dependent solution, and
+ the state variables are not used in the elastic solution.
+ In future versions of PyLith, the solution of the elastic problem will
+ be optional, so that initial state variables may be used.
\end_layout

\begin_layout Subsection
@@ -5279,6 +5298,15 @@
\begin_layout Plain Layout
Values in spatial database for initial state variables for 3D problems.
2D problems use only the relevant values.
+ Note that initial stress and strain are available for all material models.
+ Some models have additional state variables (
+\begin_inset CommandInset ref
+LatexCommand ref
+reference "tab:material-model-output"
+
+\end_inset
+
+) and initial values for these may also be provided.
\end_layout

\end_inset

Modified: short/3D/PyLith/trunk/doc/userguide/tutorials/3dhex8/quasistatic/quasistatic.lyx
===================================================================
--- short/3D/PyLith/trunk/doc/userguide/tutorials/3dhex8/quasistatic/quasistatic.lyx	2011-06-12 21:39:03 UTC (rev 18600)
+++ short/3D/PyLith/trunk/doc/userguide/tutorials/3dhex8/quasistatic/quasistatic.lyx	2011-06-12 22:59:09 UTC (rev 18601)
@@ -156,6 +156,8 @@
Some of the examples also demonstrate the usage of the nonlinear solver,
which is required by the nonlinear rheologies (power-law viscoelastic and
Drucker-Prager elastoplastic).
+ Some of the examples also demonstrate the usage of HDF5 output, which is
+ an alternative to the default VTK output.
All of the examples are contained in the directory
\family typewriter
examples/3d/hex8