Use singleton as source of constants and allow to add custom materials

Signed-off-by: Johannes Mueller <[email protected]>

Author: johannes-mueller

docs/strength/fkm_nonlinear.rst

@@ -3,4 +3,4 @@ The ``fkm_nonlinear`` functions
 
 .. autofunction:: pylife.strength.fkm_nonlinear.assessment_nonlinear_standard.perform_fkm_nonlinear_assessment
 
-.. autofunction:: pylife.strength.fkm_nonlinear.constants.for_material_group
+.. class:: pylife.strength.fkm_nonlinear.FKMNLConstants

src/pylife/strength/damage_parameter.py

@@ -24,6 +24,7 @@
 import pylife.strength.fkm_nonlinear
 import pylife.materiallaws.rambgood
 import pylife.strength.woehler_fkm_nonlinear
+from pylife.strength.fkm_nonlinear.constants import FKMNLConstants
 
 class P_RAM:
     """This class implements the damage parameter P_RAM according to guideline FKM nonlinear.
@@ -58,7 +59,7 @@ def __init__(self, collective, assessment_parameters):
         self._assessment_parameters = assessment_parameters
 
         # select set of constants according to given material group
-        self._constants = pylife.strength.fkm_nonlinear.constants.for_material_group(assessment_parameters)
+        self._constants = FKMNLConstants().for_material_group(assessment_parameters)
 
         # check if collective contains required columns
         assert "S_a" in self._collective.columns
@@ -150,7 +151,7 @@ def __init__(self, collective, assessment_parameters, component_woehler_curve_P_
         self._P_RAJ_D_0 = self._component_woehler_curve_P_RAJ.fatigue_strength_limit
 
         # select set of constants according to given material group
-        self._constants = pylife.strength.fkm_nonlinear.constants.for_material_group(assessment_parameters)
+        self._constants = FKMNLConstants().for_material_group(assessment_parameters)
 
         # check if collective contains required columns
         assert "S_a" in self._collective.columns

src/pylife/strength/fkm_nonlinear/constants.py

@@ -20,149 +20,168 @@
 import numpy as np
 import pandas as pd
 
-"""Constants for various formulas used in the FKM nonlinear procedure."""
-all_constants = pd.DataFrame({
-    "Steel": {
-        # general values and values for P_RAM
-        "E": 206e3,             # table 2.7 (2.16)
-        "n_prime": 0.187,       # table 2.8 (2.17)
-        "a_sigma": 3.1148,
-        "a_epsilon": 1033,
-        "b_sigma": 0.897,
-        "b_epsilon": -1.235,
-        "epsilon_grenz": 0.338,
-        "f_25percent_damage_woehler": 0.86,    # table 2.9
-        "a_PZ_RAM": 20.0,           # table 2.10 (2.18), note that values for P_RAJ are different
-        "b_PZ_RAM": 0.587,
-        "a_PD_RAM": 0.82,
-        "b_PD_RAM": 0.92,
-        "d_1": -0.302,
-        "d_2": -0.197,
-        "f_25percent_material_woehler_FKM_nonlinear_RAM": 0.71,     # table 2.18
-        "f_25percent_material_woehler_FKM_roughness_RAM": 0.73,     # table 35 in report "Rauheit und Randschicht 2022"
-        "k_st": 30,             # table 2.11 (2.19)
-        "a_RP": 0.27,           # table 2.12 (2.20)
-        "b_RP": 0.43,
-        "R_m_N_min": 400,
-        "a_M": 0.35,            # table 2.14 (2.22)
-        "b_M": -0.1,
-        "R_m_bm": 680,          # eq. (2.5-33)
-
-        # values for P_RAJ
-        "d_RAJ": -0.63,         # table 2.33 (2.41) Note, this is -0.56 in the FKM nonlinear document, however due to an error by the authors, the value was corrected later (e-mail of Moritz Hupka 15.09.22 10:27)
-        "f_25percent_material_woehler_FKM_nonlinear_RAJ": 0.39,   # This value is listed as 0.39, table 2.33 in FKM nonlinear 2019, and as 0.35 in table 35 in report "Rauheit und Randschicht 2022".
-        "f_25percent_material_woehler_FKM_roughness_RAJ": 0.25,   # table 35 in report "Rauheit und Randschicht 2022"
-        "a_PZ_RAJ": 10,         # Note, this is 1.173 in the FKM nonlinear document, however due to an error by the authors, the value was corrected later (e-mail of Moritz Hupka 15.09.22 10:27)
-        "b_PZ_RAJ": 0.826,      # Note, this is 1 in the FKM nonlinear document, however due to an error by the authors, the value was corrected later (e-mail of Moritz Hupka 15.09.22 10:27)
-        "a_PD_RAJ": 3.33e-5,
-        "b_PD_RAJ": 1.55,
-    },
-    "SteelCast": {
-        # general values and values for P_RAM
-        "E": 206e3,             # table 2.7 (2.16)
-        "n_prime": 0.176,       # table 2.8 (2.17)
-        "a_sigma": 1.732,
-        "a_epsilon": 0.847,
-        "b_sigma": 0.982,
-        "b_epsilon": -0.181,
-        "epsilon_grenz": np.inf,
-        "f_25percent_damage_woehler": 0.68,    # table 2.9
-        "a_PZ_RAM": 25.56,      # table 2.10 (2.18), note that values for P_RAJ are different
-        "b_PZ_RAM": 0.519,
-        "a_PD_RAM": 0.46,
-        "b_PD_RAM": 0.96,
-        "d_1": -0.289,
-        "d_2": -0.189,
-        "f_25percent_material_woehler_FKM_nonlinear_RAM": 0.51,
-        "k_st": 15,             # table 2.11 (2.19)
-        "a_RP": 0.25,           # table 2.12 (2.20)
-        "b_RP": 0.42,
-        "R_m_N_min": 400,
-        "a_M": 0.35,            # table 2.14 (2.22)
-        "b_M": 0.05,
-        "R_m_bm": 680,          # eq. (2.5-33)
-
-        # values for P_RAJ
-        "d_RAJ": -0.66,         # table 2.33 (2.41)
-        "f_25percent_material_woehler_FKM_nonlinear_RAJ": 0.40,
-        "a_PZ_RAJ": 10.03,
-        "b_PZ_RAJ": 0.695,
-        "a_PD_RAJ": 5.15e-6,
-        "b_PD_RAJ": 1.63,
-    },
-    "Al_wrought": {
-        # general values and values for P_RAM
-        "E": 70e3,              # table 2.7 (2.16)
-        "n_prime": 0.128,       # table 2.8 (2.17)
-        "a_sigma": 9.12,
-        "a_epsilon": 895.9,
-        "b_sigma": 0.742,
-        "b_epsilon": -1.183,
-        "epsilon_grenz": np.inf,
-        "f_25percent_damage_woehler": 0.88,    # table 2.9
-        "a_PZ_RAM": 16.71,      # table 2.10 (2.18), note that values for P_RAJ are different
-        "b_PZ_RAM": 0.537,
-        "a_PD_RAM": 0.30,
-        "b_PD_RAM": 1.00,
-        "d_1": -0.238,
-        "d_2": -0.167,
-        "f_25percent_material_woehler_FKM_nonlinear_RAM": 0.61,
-        "k_st": 20,             # table 2.11 (2.19)
-        "a_RP": 0.27,           # table 2.12 (2.20)
-        "b_RP": 0.43,
-        "R_m_N_min": 133,
-        "a_M": 1.0,             # table 2.14 (2.22)
-        "b_M": -0.04,
-        "R_m_bm": 270,          # eq. (2.5-33)
-
-        # values for P_RAJ
-        "d_RAJ": -0.61,         # table 2.33 (2.41)
-        "f_25percent_material_woehler_FKM_nonlinear_RAJ": 0.36,
-        "a_PZ_RAJ": 101.7,
-        "b_PZ_RAJ": 0.26,
-        "a_PD_RAJ": 5.18e-7,
-        "b_PD_RAJ": 2.04,
-    }
-})
-
-
-def for_material_group(assessment_parameters):
-    """
-    Retrieve the constants for one of the three material groups that are defined in FKM nonlinear.
-
-    .. note::
-
-        The constants for all material groups can be accessed as
-        ``pylife.strength.fkm_nonlinear.constants.all_constants``.
-
-    Parameters
-    ----------
-    assessment_parameters : pandas Series
-        A Series with at least the item ``MatGroupFKM``, which has to be one of
-        ``Steel``, ``SteelCast``, ``Al_wrought``.
-
-    Returns
-    -------
-    pandas Series
-        All constants that are defined by FKM nonlinear for the given material group.
-
-    """
-    # call user hook to modify constants if necessary
-    global all_constants
-    if "user_hook" in assessment_parameters:
-        all_constants = assessment_parameters["user_hook"](all_constants)
-
-    # select set of constants according to given material group
-    assert "MatGroupFKM" in assessment_parameters
-
-    material_group = assessment_parameters["MatGroupFKM"]
-
-    resulting_constants = all_constants[material_group]
-
-    # Rename the key for the safety factor f_25%
-    resulting_constants["f_25percent_material_woehler_RAM"] \
-        = resulting_constants["f_25percent_material_woehler_FKM_nonlinear_RAM"]
-    resulting_constants["f_25percent_material_woehler_RAJ"] \
-        = resulting_constants["f_25percent_material_woehler_FKM_nonlinear_RAJ"]
-
-    return resulting_constants
+
+class FKMNLConstants:
+    _instance = None
+
+    def __new__(cls):
+        if cls._instance is None:
+            cls._instance = super(FKMNLConstants, cls).__new__(cls)
+            cls._instance._initialize()
+        return cls._instance
+
+    def _initialize(self):
+        """Constants for various formulas used in the FKM nonlinear procedure."""
+        self._all_constants = pd.DataFrame({
+            "Steel": {
+                # general values and values for P_RAM
+                "E": 206e3,             # table 2.7 (2.16)
+                "n_prime": 0.187,       # table 2.8 (2.17)
+                "a_sigma": 3.1148,
+                "a_epsilon": 1033,
+                "b_sigma": 0.897,
+                "b_epsilon": -1.235,
+                "epsilon_grenz": 0.338,
+                "f_25percent_damage_woehler": 0.86,    # table 2.9
+                "a_PZ_RAM": 20.0,           # table 2.10 (2.18), note that values for P_RAJ are different
+                "b_PZ_RAM": 0.587,
+                "a_PD_RAM": 0.82,
+                "b_PD_RAM": 0.92,
+                "d_1": -0.302,
+                "d_2": -0.197,
+                "f_25percent_material_woehler_FKM_nonlinear_RAM": 0.71,     # table 2.18
+                "f_25percent_material_woehler_FKM_roughness_RAM": 0.73,     # table 35 in report "Rauheit und Randschicht 2022"
+                "k_st": 30,             # table 2.11 (2.19)
+                "a_RP": 0.27,           # table 2.12 (2.20)
+                "b_RP": 0.43,
+                "R_m_N_min": 400,
+                "a_M": 0.35,            # table 2.14 (2.22)
+                "b_M": -0.1,
+                "R_m_bm": 680,          # eq. (2.5-33)
+
+                # values for P_RAJ
+                "d_RAJ": -0.63,         # table 2.33 (2.41) Note, this is -0.56 in the FKM nonlinear document, however due to an error by the authors, the value was corrected later (e-mail of Moritz Hupka 15.09.22 10:27)
+                "f_25percent_material_woehler_FKM_nonlinear_RAJ": 0.39,   # This value is listed as 0.39, table 2.33 in FKM nonlinear 2019, and as 0.35 in table 35 in report "Rauheit und Randschicht 2022".
+                "f_25percent_material_woehler_FKM_roughness_RAJ": 0.25,   # table 35 in report "Rauheit und Randschicht 2022"
+                "a_PZ_RAJ": 10,         # Note, this is 1.173 in the FKM nonlinear document, however due to an error by the authors, the value was corrected later (e-mail of Moritz Hupka 15.09.22 10:27)
+                "b_PZ_RAJ": 0.826,      # Note, this is 1 in the FKM nonlinear document, however due to an error by the authors, the value was corrected later (e-mail of Moritz Hupka 15.09.22 10:27)
+                "a_PD_RAJ": 3.33e-5,
+                "b_PD_RAJ": 1.55,
+            },
+            "SteelCast": {
+                # general values and values for P_RAM
+                "E": 206e3,             # table 2.7 (2.16)
+                "n_prime": 0.176,       # table 2.8 (2.17)
+                "a_sigma": 1.732,
+                "a_epsilon": 0.847,
+                "b_sigma": 0.982,
+                "b_epsilon": -0.181,
+                "epsilon_grenz": np.inf,
+                "f_25percent_damage_woehler": 0.68,    # table 2.9
+                "a_PZ_RAM": 25.56,      # table 2.10 (2.18), note that values for P_RAJ are different
+                "b_PZ_RAM": 0.519,
+                "a_PD_RAM": 0.46,
+                "b_PD_RAM": 0.96,
+                "d_1": -0.289,
+                "d_2": -0.189,
+                "f_25percent_material_woehler_FKM_nonlinear_RAM": 0.51,
+                "k_st": 15,             # table 2.11 (2.19)
+                "a_RP": 0.25,           # table 2.12 (2.20)
+                "b_RP": 0.42,
+                "R_m_N_min": 400,
+                "a_M": 0.35,            # table 2.14 (2.22)
+                "b_M": 0.05,
+                "R_m_bm": 680,          # eq. (2.5-33)
+
+                # values for P_RAJ
+                "d_RAJ": -0.66,         # table 2.33 (2.41)
+                "f_25percent_material_woehler_FKM_nonlinear_RAJ": 0.40,
+                "a_PZ_RAJ": 10.03,
+                "b_PZ_RAJ": 0.695,
+                "a_PD_RAJ": 5.15e-6,
+                "b_PD_RAJ": 1.63,
+            },
+            "Al_wrought": {
+                # general values and values for P_RAM
+                "E": 70e3,              # table 2.7 (2.16)
+                "n_prime": 0.128,       # table 2.8 (2.17)
+                "a_sigma": 9.12,
+                "a_epsilon": 895.9,
+                "b_sigma": 0.742,
+                "b_epsilon": -1.183,
+                "epsilon_grenz": np.inf,
+                "f_25percent_damage_woehler": 0.88,    # table 2.9
+                "a_PZ_RAM": 16.71,      # table 2.10 (2.18), note that values for P_RAJ are different
+                "b_PZ_RAM": 0.537,
+                "a_PD_RAM": 0.30,
+                "b_PD_RAM": 1.00,
+                "d_1": -0.238,
+                "d_2": -0.167,
+                "f_25percent_material_woehler_FKM_nonlinear_RAM": 0.61,
+                "k_st": 20,             # table 2.11 (2.19)
+                "a_RP": 0.27,           # table 2.12 (2.20)
+                "b_RP": 0.43,
+                "R_m_N_min": 133,
+                "a_M": 1.0,             # table 2.14 (2.22)
+                "b_M": -0.04,
+                "R_m_bm": 270,          # eq. (2.5-33)
+
+                # values for P_RAJ
+                "d_RAJ": -0.61,         # table 2.33 (2.41)
+                "f_25percent_material_woehler_FKM_nonlinear_RAJ": 0.36,
+                "a_PZ_RAJ": 101.7,
+                "b_PZ_RAJ": 0.26,
+                "a_PD_RAJ": 5.18e-7,
+                "b_PD_RAJ": 2.04,
+            }
+        })
+
+    def for_material_group(self, assessment_parameters):
+        """
+        Retrieve the constants for one of the three material groups that are defined in FKM nonlinear.
+
+        .. note::
+
+            The constants for all material groups can be accessed as
+            ``pylife.strength.fkm_nonlinear.constants.all_constants``.
+
+        Parameters
+        ----------
+        assessment_parameters : pandas Series
+            A Series with at least the item ``MatGroupFKM``, which has to be one of
+            ``Steel``, ``SteelCast``, ``Al_wrought``.
+
+        Returns
+        -------
+        pandas Series
+            All constants that are defined by FKM nonlinear for the given material group.
+
+        """
+        # select set of constants according to given material group
+        assert "MatGroupFKM" in assessment_parameters
+
+        material_group = assessment_parameters["MatGroupFKM"]
+
+        resulting_constants = self._all_constants[material_group]
+
+        # Rename the key for the safety factor f_25%
+        resulting_constants["f_25percent_material_woehler_RAM"] \
+            = resulting_constants["f_25percent_material_woehler_FKM_nonlinear_RAM"]
+        resulting_constants["f_25percent_material_woehler_RAJ"] \
+            = resulting_constants["f_25percent_material_woehler_FKM_nonlinear_RAJ"]
+
+        return resulting_constants
+
+    def add_custom_material(self, material_group_nme, material_constants):
+        self._all_constants[material_group_nme] = pd.Series(material_constants)
+        return self
+
+    def __iter__(self):
+        for mg in self._all_constants:
+            yield mg
+
+    def __getitem__(self, material_group_name):
+        return self._all_constants[material_group_name].copy()
+
+    def to_pandas(self):
+        return self._all_constants.copy()

src/pylife/strength/fkm_nonlinear/damage_calculator.py

@@ -24,6 +24,7 @@
 
 import pylife.strength.woehler_fkm_nonlinear
 import pylife.strength.fkm_nonlinear.parameter_calculations
+from pylife.strength.fkm_nonlinear.constants import FKMNLConstants
 
 class DamageCalculatorPRAM:
     """This class performs the lifetime assessment according to the FKM nonlinear assessment.
@@ -189,7 +190,7 @@ def get_lifetime_functions(self, assessment_parameters):
             python function, ``failure_probability(N)``
         """
 
-        constants = pylife.strength.fkm_nonlinear.constants.for_material_group(assessment_parameters)
+        constants = FKMNLConstants().for_material_group(assessment_parameters)
 
         f_25 = constants.f_25percent_material_woehler_RAM
 
@@ -449,7 +450,7 @@ def get_lifetime_functions(self):
             python function, ``failure_probability(N)``
         """
 
-        constants = pylife.strength.fkm_nonlinear.constants.for_material_group(self._assessment_parameters)
+        constants = FKMNLConstants().for_material_group(self._assessment_parameters)
         f_25 = constants.f_25percent_material_woehler_RAJ
         slope_woehler = abs(1/self._component_woehler_curve_P_RAJ.d)
         lifetime_n_cycles = self.lifetime_n_cycles