Numerical Evaluation of Stress Intensity Factor for Inclined-Edge Crack Geometry using Singularity Elements

Abstract

Edge cracks are more dangerous than interior cracks. Free edge close to the crack influences the stress field near the crack tip (since the free edge is traction free).In case of edge crack, the free edge is not only close to the crack, but it intersects the crack. Evaluation of Stress Intensity factor for oblique edge crack geometry is done using commercial FEM software ANSYS and compared with analytical results. The conventional elements always underestimate the sharply rising stress-displacement gradients near the crack tip. Therefore, in order to produce this singularity in stresses and strains Barsoum elements were employed which involves shifting the mid-side nodes to the quarter point locations. It observed that stress intensity factor found by FEM method has good agreement with analytical results.. The singular order of stresses near the interface is a good way of understanding of failure initiation; however, in engineering applications usually the knowledge of singular orders is not enough for the prediction of failure initiation. As an example in the case of homogeneous cracks, the singular order is -1/2 which remains constant irrespective of the surrounding environment and outside loading of the crack. These influential factors are reflected through the associated stress intensity factor of the cracks. Hwu and Kuo [1] have demonstrated several different kinds of examples such as cracks in homogenous isotropic or anisotropic materials, central or edge notches in isotropic materials, interface cracks and interface corners between two dissimilar materials. It is also shown that KI Evaluation Using Displacement etrapolation technique under adaptive dense mesh with Parallel Finite Element gives fairly accurate results [2]. Based upon the analytical solutions obtained previously for the multi-bonded anisotropic wedges and the well-known path-independent H-integral, Hwo and Kuo [3] provided a unified definition and a stable computing approach for the stress intensity factors of interface corners. The stress intensity factor calculations are usually limited to Linear Elastic Fracture Mechanics (LEFM). For a linear elastic material the stress and strain fields ahead of the crack tip are expressed as [4]. The singular order of stresses near the interface is a good way of understanding of failure initiation; however, in engineering applications usually the knowledge of singular orders is not enough for the prediction of failure initiation. As an example in the case of homogeneous cracks, the singular order is -1/2 which remains constant irrespective of the surrounding environment and outside loading of the crack. These influential factors are reflected through the associated stress intensity factor of the cracks. Hwu and Kuo [1] have demonstrated several different kinds of examples such as cracks in homogenous isotropic or anisotropic materials, central or edge notches in isotropic materials, interface cracks and interface corners between two dissimilar materials. It is also shown that KI Evaluation Using Displacement etrapolation technique under adaptive dense mesh with Parallel Finite Element gives fairly accurate results [2]. Based upon the analytical solutions obtained previously for the multi-bonded anisotropic wedges and the wellknown path-independent H-integral, Hwo and Kuo [3] provided a unified definition and a stable computing approach for the stress intensity factors of interface corners. The stress intensity factor calculations are usually limited to Linear Elastic Fracture Mechanics (LEFM). For a linear elastic material the stress and strain fields ahead of the crack tip are expressed as [4].