| IN-SITU MEASUREMENT OF LOADING STRESSES WITH X-RAY DIFFRACTION FOR YIELD LOCUS DETERMINATION |
| A. GÜNER1, B. ZILLMANN2, T. LAMPKE2, A. E. TEKKAYA1 |
1TU Dortmund University
2Technische Universitaet Chemnitz |
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| ABSTRACT |
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The application of the X-ray diffraction method is introduced to solve the problem of inhomogeneous deformation fields in the specimens used for sheet metal characterization. In this method, strains are measured on one side of a specimen with optical measurement systems. On the other side, loading stresses on a specimen are captured with an X-ray diffractometer mounted on a universal testing machine. By this way, the whole stress-strain history of a material point is tracked during testing. The method was first applied to uniaxial tension tests, whereby the applicability of the theory of stress factors and effective X-ray elastic constants were tested. The relaxation behavior of a sheet material which shows itself as stress drops during in-situ experimentation was characterized and compensated by a visco-plastic material model for different stress states. The proposed method was applied to characterize aluminum alloy AA5182 under plane strain tension and shear conditions and the results were compared with the conventionally obtained yield locus. Numerical analyses of a workpiece with the Vegter and Yld2000-2D material models show that the enriched yield locus definition with accurate plane strain tension and shear stresses captures the experimentally obtained surface strains more precisely. |
| Key Words:
X-ray diffraction, Anisotropy, Finite element modeling, Characterization, Yield locus |
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