13th International Conference on Fracture June 16–21, 2013, Beijing, China 6 material Jacobian matrix denoted as ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ Δ Δ Δ Δ = n n s n n s s s T T T T d d d d d d d d D . (16) During the implementation, the matrices of Eq. (15) should be transformed to x-y coordinates according to Eq. (14). Figure 4. Illustration of a cohesive element 4. Results and discussion 4.1. Crack growth under monotonic loading C(T) specimens were tested to determine cohesive parameters under monotonic loading. The load-displacement curve was recorded in the experiment. In computations the finite element mesh of the potential damage zone ahead of the crack tip is refined and the minimal element size is about 0.4mm. In the process of numerical simulation, cohesive elements are placed at the symmetric line of the mesh with zero thickness. The rest of region is occupied by the conventional four nodal elements under the plane strain assumption. The initial crack length is around 29mm. The stainless steel is described by the J2 plasticity for simplicity. (a) (b) Figure 5. Computational prediction of monotonic crack growth in a C(T) specimen. (a) Comparison between the simulation and the test result. (b) Cohesive response of a ruptured element during the crack propagation.
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