In-Situ Measurement of Loading Stresses by Means of X-ray Diffraction with Multi-State Sheet Specimen

Excerpt

For accurate finite element simulations, description of the material behavior plays an important role. The anisotropic plastic flow of sheet metals is modeled with anisotropic yield conditions which need different number of material parameters. In order to increase the flexibility of these yield conditions the needed number of material parameters should also be increased. The quality of the identified material parameters directly influences the quality of the numerical predictions. In order to obtain these parameters there exist different characterization tests like uniaxial tension test, plane strain tension test, Miyauchi test and biaxial tension test [1]. Inhomogeneity of the deformation due to the edge effects is the main problem in most of the test specimens. The forces needed for analytical stress calculation act on the whole inhomogeneous deformation zone and therefore the stresses calculated with these force values differ from the real stresses [2]. There are mainly three solutions to this problem in the literature: The analytically calculated stresses can be corrected by empirically obtained factors [3], the specimen geometry can be optimized [4] or inverse analysis can be utilized to exploit inhomogeneous deformation fields [5]. …