Browsing by Author "Welzel, Udo Siegfried"

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    Diffraction analysis of residual stress; modelling elastic grain interaction
    (2002) Welzel, Udo Siegfried; Mittemeijer, Eric J. (Prof. Dr. Ir.)
    X-ray (and neutron) diffraction can be used for the non-destructive analysis of residual and load stresses. Suitable parameters as (X-ray) elastic constants are required for relating the measured lattice strains to the components of the mechanical stress tensor. For the first time a unifying, rigorous treatment for the diffraction stress analysis of both macroscopically elastically isotropic and anisotropic polycrystals is given. The notion 'surface anisotropy' of bulk specimens is revisited as a special case of direction-dependent grain interaction. Evidence for direction-dependent grain interaction, i.e. the direction-dependence of the elastic coupling of grains in a polycrystal, was obtained only very recently for the first time in the diffraction stress analysis of an untextured, polycrystalline nickel thin film by van Leeuwen et al. (van Leeuwen, M., Kamminga, J.-D. & Mittemeijer, E. J. (1999), J. Appl. Phys. 86 [4], 1904). The direction-dependent grain-interaction model employed by van Leeuwen et al. is elaborated for the textured case in this work. The concept of direction-dependent grain interaction for diffraction analysis of stress is generalised, overcoming some unrealistic (extreme) grain interaction assumptions involved in the model presented by van Leeuwen et al.. Experimental verification has been achieved by X-ray diffraction strain measurements performed on a vapour deposited copper film. For quantitative diffraction stress analysis the crystallographic texture of the specimen has to be taken into account in terms of an orientation distribution function. In this work, texture analysis was performed employing a polycapillary X-ray lens. The corrections for instrumental aberrations in texture measurements using an X-ray lens were for the first time rigorously investigated and suitable correction procedures are proposed.