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import numpy as np
import pylife.utils.functions as functions
from pylife.utils.probability_data import ProbabilityFit
[docs]
class PearlChainProbability(ProbabilityFit):
"""Shift all the data point to a normalized load level.
Pearl chain method: consists of shifting the fractured data to a median
load level. The shifted data points are assigned to a Rossow failure
probability. The scatter in load-cycle direction can be computed from the
probability net.
Parameters
----------
fracutres: pd.DataFrame consisting `load` and `cycles`
The data point of the fractures to be shifted.
slope: float
The ``k_1`` slope the data is to be shifted along.
"""
def __init__(self, fractures, slope):
self._normed_load = fractures.load.mean()
self._normed_cycles = np.sort(fractures.cycles * ((self._normed_load/fractures.load)**(slope)))
fp = functions.rossow_cumfreqs(len(self._normed_cycles))
super().__init__(fp, self._normed_cycles)
@property
def normed_load(self):
"""The normalized (shifted) load level."""
return self._normed_load
@property
def normed_cycles(self):
"""The cycles shifted to the normalized load level."""
return self._normed_cycles