Three Dimensional Static and Dynamic Stress Intensity Factor Computations Using ANSYS

In three-dimensional computation for linear elastic fracture mechanics, how to simulate the stress singularity near the crack tip has been a difficult and important point. The so-called quarter-point element is often used to model the stress and displacement field near the crack tip. However, ANSYS only provides automatic meshing capability for two-dimensional problems. It cannot directly generate crack elements for three-dimensional models. At the crack tip region we generate the quarter-point element manually to model the correct singularity of the stresses near the crack tip, thus making the computation for three-dimensional crack problem possible. Manual generation of elements may be tedious for a large and complex model. In this paper, two methods are presented to compute three-dimensional Stress Intensity Factors (SIFs). Firstly, submodel and partial crack submodel methods are adopted to compute the SIFs. Manual generation is only needed for submodel region, which is of much reduced size, thus manual generation is feasible. Secondly, mesh200 element can be used to mesh the area with two dimensional singular elements, and then sweep this area through certain coordinate system to establish three-dimensional crack elements. Finally, three static and dynamic crack examples are given to prove the correctness and ability of these methods. The accuracy of these methods is guaranteed compared with other literature. These two methods are easy to handle and extend the ability of ANSYS in computing three-dimensional SIF.

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