13th International Conference on Fracture June 16–21, 2013, Beijing, China 1 Simulation of fracture and fatigue damage in stainless steel 304 using a cohesive zone model Huan Li, Huang Yuan* Department of Mechanical Engineering, University of Wuppertal, Germany. * Corresponding author: h.yuan@uni-wuppertal.de Abstract In the present paper a cohesive zone model coupled with monotonic and cyclic damage mechanisms for simulating elastic-plastic fracture and fatigue crack growth is introduced and applied for investigating failure processes in compact tension specimens. Fracture and fatigue crack tests are conducted on the compact tension C(T) specimen made of stainless steel 304 to study crack growth behavior under fracture and low cycle fatigue loading condition associated with severe elastic-plastic deformations. A good agreement between the prediction and the experimental result is obtained from the present simulations. It confirms that the suggested cohesive model in conjugation with the nonlinear damage evolution equations is applicable for describing the material degradation behavior of stainless steel 304 under both monotonic and cyclic loading with large plastic deformations. Keywords Cohesive model, damage evolution, low cycle fatigue, elasto-plastic growth, crack growth rate 1. Introduction Fatigue crack in industrial components are often subjected to heavy cyclic loading, and it is important to predict the fatigue crack growth behavior under higher stress fields. In low cycle metal fatigue problems, e.g. under loading conditions with maximum stresses beyond yield stress, specimens fail in small numbers of loading cycles. Comparing with Paris’ law, Walker model and Forman model or any other kinds of stress intensity factor based models, the cohesive model is more advantageous and gives the possibility to analyze the fatigue propagation behavior under severe plastic loading conditions, since the characterization of the cohesive zone model is generally applicable for inelastic materials [1-7]. Furthermore, it becomes possible to describe crack nucleation and propagation uniformly by the cohesive model. Originally, the cohesive zone model was introduced to describe the fracture process zone ahead of the crack-tip by Dugdale [8] and Barenblatt [9]. In the last twenty years, the cohesive modeling has been applied in simulating monotonic fracture process for diverse materials and has also been verified by experimental results [10-13]. For the fatigue failure analysis, the loading history dependent development of material degradation has to be taken into account under cyclic loading. Establishing a physical solid cohesive model for finite fatigue life is under intensive investigation in many research groups worldwide [2, 3, 14-17]. In the present study, the fatigue crack propagation experiments have been conducted using compact tension C(T) of type 304 stainless steel associated with large plastic deformations. A cohesive model coupled with damage for prediction of fracture and fatigue behavior is introduced for elastic-plastic crack propagation associated with both normal and shear displacements of the crack surface. Both rupture damage and cyclic damage accumulation are considered in the damage evolution equations. The numerical results agree with experimental data and reproduce the high
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