Influence of measurement and evaluation parameters on stress distributions investigated by X‐rays

The complete triaxial X‐ray strain or stress analysis including gradients requires a physical description of the beam path through the superficial layer of the material for both the conventional ω and Ψ goniometer. Within this description, a theory has been developed for plane, cylindrical, spherical or any other convex or concave specimen topography which can be described by two different radii. All crystal structures are supported. Measurements and calculations are controlled by the independent in‐situ determination of Poisson's ratio and the stress free lattice spacing. The physical boundary conditions are verified or can be postulated depending on the measurement quality. A complete internal strain and stress field analysis is discussed in terms of the ‘X‐ray integral method’ on steel specimens of 100 Cr‐6 (ASTM: A 295, BS: 97012), Al₂O₃ ceramics using conventional X‐ray diffractometry and on NiO layers on a metal substrate by the use of synchrotron radiation and parallel beam optics.