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Project A13: Local analysis of residual stresses on strongly textured materials

Person in Charge: Dipl.-Ing. Simone Schuster
  Motivation and aims:
Residual stress analysis on highly textured materials is basically problematic. Commonly, the separate analysis methods are based on isotropic material properties. X-ray diffraction stress analysis and the incremental hole-drilling technique are the most widely used methods to determine residual stresses. For application of X-ray diffraction already several approaches have been proposed to determine residual stresses in anisotropic materials (e.g. crystallite group method, application of X-ray stress factors Fij). However these strategies are very laborious. The superior aim of this part of the project is to extend the field of application for the incremental hole-drilling method to strongly textured materials as well as the development of a measurement and evaluation strategy for practical use.
Investigations Results
Load stress and residual stress analysis by means of the incremental hole-drilling technique will be carried out on steel parts (DC04, dual phase steel, press hardening steel) which were picked out at different stages of the process chain cold rolling - heat treatment - deep drawing as well as before and after the press hardening process using the incremental hole-drilling method. A characterization of the preferred crystallographic orientation induced by the individual process steps will be accomplished by X-ray texture analysis. The results of the stress analysis by means of the hole-drilling technique will be compared with complementary analysis methods (e.g. diffraction methods). To a first approach, calibration experiments will be carried out on different steel sheets by varying the grade of the texture and the orientation of the texture with respect to the direction of the applied load systematically. In addition to the laborious experimental investigations further calibration tests will be simulated by means of FEM. The experimental data are used to validate the numeric analysis. The aim of the systematic studies is the determination and the evaluation of the effect of texture on residual stress analysis. First results indicate that the influence of the rolling texture for the ´single-phase´ steel DC04 and the magnitude of the texture on the determination of residual stress using the incremental hole-drilling method are almost negligible.