Experimental and Numerical Analysis of Work Hardening Effects in Single- and Polycrystals during Cyclic Loading (Bauschinger Effect)

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In practice, the service life of cyclically loaded metallic components is limited by fatigue damage of the alloys applied. Partly irreversibility of the cyclic plastic deformation leads to strain localization, crack initiation and propagation and eventually, to fracture. Especially, unfavorable crystallographic orientations of grains and grain boundaries cause additional stress concentration, and therefore, local plasticity may exhibit even at deformations that are macroscopically elastic. Here, the Bauschinger effect is of particular significance, since it describes load-orientation-dependent strain hardening. By means of micro-indentation and micro-bending experiments as well as tension-compression tests applied to a variety of heat treatments, where the deformation mechanisms will be identified in detail by microstructural analysis (using scanning electron microscopy, incl. EBSD and FIB, and transmission electron microscopy), the proposed project will lead to the development of single crystal and poly crystal material models, that allow for explicit implementation of the Bauschinger effect in the Finite Element method. Verification experiments on two technical important alloys, the duplex steel and Ni-based superalloy 718, will show the potentials and the limits of the proposed models.