code: def _calc_damping_min(self):
          
          return ((0.8005 + 0.0129 * self._plas_index * self._ocr ** -0.1069) *
                  (self._stress_mean * KPA_TO_ATM)
                  ** -0.2889 * (1 + 0.2919 * np.log(self._freq))) / 100
docs: minimum damping [decimal]