| Popis: |
Misalignment of the X-ray diffractometer can lead to significant errors in the stress measured by X-ray diffractometry. A generalized equation is derived for the relationship between the crystal lattice d spacing and the stress tensor which involves the Δψ and Δχ misalignments of the diffractometer as well as large χ-angle tilts and ϕ-angle rotations. Inclusion of the ϕ and χ rotations allows for measurements with complicated sample geometries as well as for a direct comparison of the χ- and ψ-geometry diffractometers in common use. In the case of no misalignment errors (Δχ, Δψ = 0), the symmetries between the classical ψ-tilt and χ-tilt diffractometers are clearly shown. The generalized equation is reduced to more manageable forms for several approximations in which the misalignments are small. How these errors affect the computation of shear and normal stresses is also discussed. Finally, determination of residual stresses in more complicated sample geometries is discussed. |
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