![]() The stress intensity factors were computed using the virtual crack closure-integral method (VCCM). The local mesh was overlaid along with the global before the numerical computation taken place to solve the engineering problem. Hence, the local crack (finer mesh) will be defined the exact location and the mesh control accordingly. The pre-post program was used to model the global geometry (coarser mesh) known as FAST including the material and boundary conditions. A method known as global-local overlay technique was used in this study to predict the fatigue behavior that involve of two separate meshes each specifically for global (geometry) and local ( crack). The paper is presenting the fatigue crack growth (FCG) behavior of semi-elliptical surface cracks for API X65 gas pipeline using S-version FEM. Also, the stress-intensity variations in the boundary-layer region at the intersection of the crack with the free surface were investigated.įatigue crack growth behaviour of semi-elliptical surface cracks for an API 5L X65 gas pipeline under tension The 6900 degrees of freedom used here were more than twice the number used in previously reported solutions. To verify the accuracy of the three-dimensional finite-element models employed, convergence was studied by varying the number of degrees of freedom in the models from 1500 to 6900. In this paper, stress-intensity factors for shallow and deep semi-elliptical surface cracks in plates subjected to tension are presented. However, some of these solutions are in disagreement by 50-100%. Several calculations of stress-intensity factors for semi-elliptical surface cracks subjected to tension have appeared in the literature. Surface cracks are among the more common flaws in aircraft and pressure vessel components. Stress-intensity factors for a wide range of semi-elliptical surface cracks in finite-thickness plates A semi-elliptical surface crack is illustrated in Figure 1-1. The more complex surface crack is typically modeled numerically with the Finite Element Method (FEM). When considering simpler crack configurations, such as a through-the-thickness crack, a three-dimensional (3D) geometry may be modeled under the approximation of two-dimensional (2D) plane stress or plane strain. The shape and geometry of the flaw are among the most influential factors. A semi-elliptical surface crack subjected to monotonic loading will exhibit stable crack growth until the crack has reached a critical size, at which the crack loses stability and fracture ensues (Newman, 2000). Structural components often exhibit several different types of defects, among the most prevalent being surface cracks. M.Īccurate life assessment of structural components may require advanced life prediction criteria and methodologies. ![]() Fracture Analysis of Semi-Elliptical Surface Cracks in Ductile Materialsĭaniewicz, S.
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