Investigation of combined influence of skin pass rolling and roller straightening of a thin sheet made of materials with different crystal lattice on microstructure, texture, static and fatigue strength

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Skin pass rolling and roller straightening represent the final operations in sheet production and decisively determine the resulting microstructural and mechanical properties of the products. In preliminary investigations, it was shown that the intensity of the influence of these forming operations depends inter alia on material lattice structure. Further investigation is required on the combined influence on sheet properties as a result of monotonous forming by skin pass rolling which induces material work hardening and cyclical forming by roller straightening, which could induce either work hardening or work softening. Since sheet metal parts are subject to not only static but also cyclical mechanical stresses in later operations the residual stress state is of essential significance in addition to work hardening or softening. Thus, a comprehensive material characterization is required concerning mechanical properties during static and cyclical stresses. The work programme of the planned project includes the analysis of changes in mechanical properties during static and cyclical stresses as well as the investigation of microstructure and texture of sheets during various skin pass rolling and roller straightening conditions including the s-shape enclosing the rolls. The scientific aim of the planned research project is the investigation of combined influence of monotonous forming during skin pass rolling and cyclical forming during roller straightening of sheets made of materials with different crystal lattices (DC01, Cu, Alpha-Ti) on microstructure, texture, the level and sign of residual stresses, and the mechanical properties within the framework of static and cyclical experiments. The practical aim of the project is the development of an appropriate technology for production of sheets with load-adjusted microstructure, texture, and a high static and fatigue strength by a suitable combination of monotonous forming by skin pass rolling and cyclical forming by roller straightening conditions.