A Proposal of Fracture Control Design Procedure

In order to make the fracture mechanics analysis readily applicable at design levels with efforts normally required in design for stress analysis, this paper proposes its simplified application procedure. The key point of this procedure is the estimation of the crack propagation path and K value from the stress analysis results on crackless model.The proposed crack path estimation criteria are based on the study of the relationship between the direction of principal stress in a flat plate as well as the K value when the crack reaches a normal crossing member and the crack propagation path. The proposal also includes simplified K value estimation methods by grouping actual forms of cracking into several typical patterns, so that the designer can estimate the K value for almost any type of structural members which he will face in his design. To verify the validity of the proposed procedure, the bottom transverse damage of a large tanker was analyzed for comparison with the actual cracks. The analysis results are consistent in explaining the actual damage phenomena and this procedure has been proved quite practical through examination of the design measures taken.