Numerical analysis of stress-state-dependent damage and failure behavior of ductile steel based on biaxial experiments
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ORIGINAL PAPER
Numerical analysis of stress-state-dependent damage and failure behavior of ductile steel based on biaxial experiments Michael Brünig1 · Marco Schmidt1 · Steffen Gerke1 Received: 9 July 2020 / Accepted: 28 September 2020 © The Author(s) 2020
Abstract The paper deals with a numerical model to investigate the influence of stress state on damage and failure in the ductile steel X5CrNi18-10. The numerical analysis is based on an anisotropic continuum damage model taking into account yield and damage criteria as well as evolution equations for plastic and damage strain rate tensors. Results of numerical simulations of biaxial experiments with the X0- and the H-specimen presented. In the experiments, formation of strain fields are monitored by digital image correlation which can be compared with numerically predicted ones to validate the numerical model. Based on the numerical analysis the strain and stress quantities in selected parts of the specimens are predicted. Analysis of damage strain variables enables prediction of fracture lines observed in the tests. Stress measures are used to explain different stressstate-dependent damage and failure mechanisms on the micro-level visualized on fracture surfaces by scanning electron microscopy. Keywords Ductile damage · Stress state dependence · Low carbon steel · Numerical analysis · Biaxial experiments
1 Introduction During the last years the use of high quality ductile metals has been remarkably increased due to demands and requirements of the customers. For example, reduction in energy consumption, improved cost efficiency and enforced safety pretensions have caused intensive research activities to fulfill environmental, economic and material strength demands. In products of modern engineering disciplines material properties are enhanced to reduce localization of irreversible deformations as well as damage and failure in material samples under various multi-axial loading conditions. Thus, analysis of new engineering materials must be based on accurately predictive and practically applicable constitutive models and corresponding efficient, robust and accurate numerical algorithms. It has been observed in many experiments and practical applications that loading and deformation of material Dedicated to Professor Tomasz Lodygowski on the occasion of his 70th birthday.
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Michael Brünig [email protected] Institut für Mechanik und Statik, Universität der Bundeswehr München, 85577 Neubiberg, Germany
elements often leads to localized bands of inelastic strains accompanied by damage and fracture processes on the microlevel [3,4,29]. Growth of these micro-mechanisms can then produce macro-cracks as a cursor of final failure of structures. These damage and fracture processes acting on the micro-scale depend on the stress state in a material element. For example, tensile loading with high positive stress triaxialities causes growth and coalescence of micro-pores whereas in shear and compressive loading micro-shear-cracks occur. In addition, combination of
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