The constraint voigt model for calculation of the X-ray elastic constants of polycrystalline materials with orthorhombic crystal symmetry

摘要

Because of the elastic anisotropy, stresses determined from diffraction methods like X-ray or neutron diffraction can not be determined better than 10% or 20% irrespective of the model which is used for the calculation of the X-ray elastic constants (Voigt, Reuss, Kroner). A reliable stress determination through Hooke's law is only possible if perfect isotropic behaviour can be assumed. In that case, all models give the same values for the X-ray elastic constants. In polycrystalline materials with cubic crystal symmetry, isotropic behaviour is known at an (hkl) dependent orientation factor of 0.2 independent of the material parameters. For all other materials with lower symmetry, the observation of isotropic behaviour is not straight forward. In order to check the possibility of isotropic elastic behaviour the calculation of the full compliance tensor is required [1]. [References: 6]