Biaxial experiments on characterization of stress-state-dependent damage in ductile metals

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The paper discusses new biaxial experiments to characterize stress-state-dependent damage and fracture processes in ductile metals on different scales. To motivate the experimental program a phenomenological continuum damage model is presented demonstrating the need of experiments covering a wide range of stress states and loading histories. Biaxial experiments with the X0-specimen taken from thin metal sheets tested under different load ratios are discussed with focus on proportional and corresponding non-proportional loading paths. During the tests strain fields on the surfaces of critical regions of the specimen are monitored by digital image correlation technique elucidating formation of localized strain bands leading to damage and failure. After the experiments fracture surfaces are examined by scanning electron microscopy revealing different damage and fracture process on the micro-scale depending on the stress states and the loading histories.