work on readme

README.md

@@ -1,27 +1,13 @@
 # fenics-constitutive
 
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+_For some examples which are using legacy-FEniCS you may look on the old `master` branch [legacy code](https://github.com/BAMresearch/fenics-constitutive/tree/master)_
 
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+The new and improved version of `fenics-constitutive` which has the goal of simulating mechanical problems in FEniCSx with nonlinear consitutive models like plasticity, damage, etc. Everything is still a work in process, but from this projct you might expect:
 
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+1. An interface for constitutive models for small strain increments (and some examples for such models)
+2. Solvers for mechanical problems which can use any constitutive model that follows our interface design
+   * This means that **YOU** may write constitutive models in any programming language as long as you can bind that code to Python and this code takes `numpy.ndarray` as parameters.
+3. Solvers that account for large deformations via an objective stress rate.
+4. A documentaion explaining the interface design and tutorials on how to write your own constitutive models.
 
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+More to follow soon!

src/fenics_constitutive/interfaces.py

@@ -8,6 +8,7 @@
     "IncrSmallStrainModel",
 ]
 
+
 class Constraint(Enum):
     UNIAXIAL_STRAIN = 1
     UNIAXIAL_STRESS = 2
@@ -28,25 +29,24 @@ def stress_strain_dim(self):
             case Constraint.FULL:
                 return 6
 
+
 class IncrSmallStrainModel(ABC):
     """Interface for incremental small strain models."""
 
     @abstractmethod
-    def evaluate(self, grad_u: np.ndarray, mandel_stress: np.ndarray, tangent: np.ndarray) -> None:
+    def evaluate(
+        self, del_t: float, grad_u: np.ndarray, mandel_stress: np.ndarray, tangent: np.ndarray
+    ) -> None:
         """Evaluate the constitutive model.
 
         Parameters:
             grad_u : The gradient of the displacement field.
-        mandel_stress : The Mandel stress.
-        tangent : The tangent.
-
+            mandel_stress : The Mandel stress.
+            tangent : The tangent.
         """
         pass
 
     @abstractproperty
     def constraint(self) -> Constraint:
         """The constraint."""
         pass
-
-
-