Merge pull request #21 from adtzlr/fix-svk

Fix St.-Venant-Kirchhoff material formulation, fixes #20
adtzlr · Sep 27, 2021 · 89a9a2d · 89a9a2d
2 parents bdaad40 + f8fb252
commit 89a9a2d
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diff --git a/README.md b/README.md
@@ -140,9 +140,11 @@ a) the volume ratio is greater zero,
 b) the slope of stress vs. stretch and
 c) the sign of the resulting stretch from a small superposed force in one direction.
 
-## Hints
+## Hints and usage in FEM modules
 Please have a look at [casADi's documentation](https://web.casadi.org/). It is very powerful but unfortunately does not support all the Python stuff you would expect. For example Python's default if-else-statements can't be used in combination with symbolic conditions (use `math.if_else(cond, if_true, if_false)` instead).
 
+Simple examples for using `matadi` with [`scikit-fem`](https://github.com/adtzlr/matadi/discussions/14#) as well as with [`felupe`](https://github.com/adtzlr/matadi/discussions/22) are shown in the Discussion section.
+
 ## References
 [1] J. A. E. Andersson, J. Gillis, G. Horn, J. B. Rawlings, and M. Diehl, *CasADi - A software framework for nonlinear optimization and optimal control*, Math. Prog. Comp., vol. 11, no. 1, pp. 1–36, 2019, [![DOI:10.1007/s12532-018-0139-4](https://zenodo.org/badge/DOI/10.1007/s12532-018-0139-4.svg)](https://doi.org/10.1007/s12532-018-0139-4)
 

diff --git a/matadi/__about__.py b/matadi/__about__.py
@@ -1 +1 @@
-__version__ = "0.0.10"
+__version__ = "0.0.11"
diff --git a/matadi/models/_hyperelasticity_isotropic.py b/matadi/models/_hyperelasticity_isotropic.py
@@ -4,8 +4,8 @@
 
 def saint_venant_kirchhoff(F, mu, lmbda):
     C = transpose(F) @ F
-    I1 = trace(C)
-    I2 = trace(C @ C)
+    I1 = trace(C) / 2 - 3 / 2
+    I2 = trace(C @ C) / 4 - trace(C) / 2 + 3 / 4
     return mu * I2 + lmbda * I1 ** 2 / 2
 
 

diff --git a/pyproject.toml b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "matadi"
-version = "0.0.10"
+version = "0.0.11"
 description = "Material Definition with Automatic Differentiation"
 readme = "README.md"
 requires-python = ">=3.6"

diff --git a/setup.cfg b/setup.cfg
@@ -1,6 +1,6 @@
 [metadata]
 name = matadi
-version = 0.0.10
+version = 0.0.11
 author = Andreas Dutzler
 author_email = a.dutzler@gmail.com
 description = Material Definition with Automatic Differentiation