Invariant intersections in diffraction stress analysis — a check of experimental results

There are well known methods to determine residual and load stresses from the measurement of lattice strains by X-ray and neutron diffraction. It is shown theoretically that certain lattice strains are independent of the influences of the stress state, the anisotropy, the orientation or the assumption of the kind of crystallite interaction. The result is discussed and its validity is confirmed by experiments. Cubic symmetry is assumed. The invariant points can be used to check the experimental results fulfilling the theoretical conditions, because different data for residual or load stress states should intersect in special invariant points.