Fracture mechanics methodologies for flaw stability analysis of a storage tank were compared in terms of the maximum stable through-wall flaw sizes or “instability lengths.” The comparison was made at a full range of stress levels at a specific set of mechanical properties of A285 carbon steel and with a specific tank configuration. The two general methodologies, the J-integral-tearing modulus (J-T) and the failure assessment diagram (FAD), and several specific estimation schemes were evaluated. A finite element analysis of a flawed tank was also performed for validating the J estimation scheme with a curvature correction and for constructing the finite element-based FAD. The calculated instability crack lengths show that the J-T methodology based on a center-cracked panel solution with a curvature correction, and the material-specific FAD, most closely approximate the result calculated with finite element analysis for the stresses at the highest fill levels in the storage tanks (less than 124 MPa or 18 ksi). The results from the other FAD methods show instability lengths less than the J-T results over this range.

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