Fracture Mechannics Analysis Of Embedded Cracks In Plates

During the assessment of structure integrity, the two parameters-stress intensity factor and J-integral are two very important assessing parameters. This paper calculates the two parameters under loads of pure tension, pure bending, and combined tension and bending. According the available kinds of limited load solutions, get the limited loads of this paper’s models, furthermore, through the reference stress method, estimate the J-integral, namely Jref, then compare Jref with JFE from FE method.(1) The stress intensity factor is obtained for the plates under pure tension and pure bending with different crack shapes (Φ=0.2,0.4,1.0), different crack depths (a=0.1,0.2,0.3), different crack offsets(K=0,0.1,0.2), the stress intensity factor for plates under combined tension and bending can be obtained using Superposition Principle. Then, the influence coefficient related to the stress intensity factor for embedded cracks is calculated, giving the summary on the changing rules of influence coefficient impacted by these geometrical configurations parameters, crack location, and loading types.(2) The linear elastic J solution and fully plastic J solution are obtained for the plates with different crack shapes (0=0.2,0.4,1.0), different crack depths (a=0.1,0.2,0.3), different crack offsets (κ=0,0.1,0.2), and different load rations (λ=0,0.3,0.7,∞). The fully plastic J solution was gotten with the material relationship of Romberg-Osgood (n=5).(3) Comparing the estimated J-integral, namely Jref with JFE from FE method under the above different crack geometry parameters, crack location, and different loads. The different kinds of Jref are up to the different types of limited loads.(4) In this paper, the fracture behavior of plates with embedded offset elliptical cracks under combined tension and bending is analyzed using3-D elastic-plastic finite element method. The J-integral values obtained from the FE analyses for the crack tip at the smallest ligament are then compared with those estimated using the reference stress method. The results show that the reference stress method may underestimate the FE J when the global limit load is used. The reason could be that the plastic zone correction in the reference stress method is not sufficient to cover the plastic zone in the small ligament due to the ligament yielding.